Title of Invention

A METHOD FOR MANUFACTURING SOOT POROUS BODY

Abstract

A method for increasing the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the soot deposition machine for manufacturing the soot porous body, without modifying the existing soot deposition machines is disclosed. The method involves multiple stages of soot deposition using multiple soot deposition machines, each machine having a plurality of burners, the diameter of burners for each machine being different, thus controlling the deposition rate and at the same time ensuring that the burners are not idle. The method further provides for matching the density of soot deposition across machines to avoid problems like splitting of deposited soot in the soot porous body formed, slippage, bubbles, and interface irregularities.

Full Text

FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION (See Section 10 and Rule 13) 1. Title of the Invention: - A method for increasing utilization of soot deposition machine, thereby-increasing the production capacity. 2. Applicant(s): - (a) Name: STERLITE OPTICAL TECHNOLOGIES LTD. (b) Nationality: An Indian Company (c) Address: E1/E2/E3, MIDC, Waluj, Aurangabad - 431136 Maharashtra, INDIA 3. Preamble to the Description: - Complete Specification: The following specification particularly describes the invention and the manner in which it is to be performed. CONFIDENTIAL PA/043/SPECIFICATION V-l I9.09.2007 Field of the Invention: The present invention generally relates to the field of optical fiber preform manufacture. Particularly, the present invention relates to a method for manufacture of soot porous body and soot porous body produced therefrom. More particularly, the present invention relates to a method for increasing the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the soot deposition machines for manufacturing the soot porous body without modification of the existing machines. The present invention also relates to optical fiber preform and optical fiber prepared from the soot porous body. Background of the Invention: Optical fiber serves as the backbone of networks for audio, video & data transmission, thus plays a significant role in the field of communications. The utilization of optical fiber has increased remarkably. Further, it is anticipated that the use of optical fibers in local loop telephone and cable TV service will increase in order to deliver greater amount of information in the form of data, audio, and video signals. Optical fiber comprises a core and a cladding surrounding the core. The refractive index of the core is higher as compared with the refractive index of the cladding in order to achieve light transmission inside the optical fiber, by the phenomena known as total internal reflection. Generally, either the refractive index of the core is substantially uniform across its diameter (also called step index optical fiber) or the refractive index of the core has a maximum at the center and decrease in parabolic fashion near the periphery (also called graded index optical fiber). Any other geometric shape and profile of the refractive index of the core is possible catering to a particular need. In the view of the ever-increasing demand of optical fibers it is necessary to increase production of optical fiber but on other hand it is also essential to reduce the manufacturing cost, meaning thereby, it is necessary to increase the efficiency of the manufacturing process. One way of achieving this is by reducing the manufacturing time at each step of the optical fiber 2 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 manufacture without modification of existing machines or within the same infrastructure. Usually, the optical fiber is manufactured by batch type manufacturing process, wherein the optical fiber is obtained by drawing an optical fiber preform. The optical fiber preform is a magnified image of optical fiber, which resembles the optical fiber and comprises a central core portion and an outer cladding but at least several hundred times magnified as compared to optical fiber dimensions. The core portion of the optical fiber preform can be prepared by any known conventional methods, for example by Atmospheric Chemical Vapor Deposition (ACVD) method, while the cladding portion can be prepared by ACVD method or any other method like clad tube jacketing. Figure 1 illustrates an ACVD soot deposition machine 101 for deposition of soot, resulting in the formation of soot porous body. In accordance with the conventional ACVD method the soot 107 is deposited during the deposition process step on the cylindrical member 104 (also referred as target rod or mandrel) with a hollow glass handle 105 attached to one end of the cylindrical member 104, wherein the hollow glass handle 105 facilitates handling of the soot porous body 121. The opposite ends of the cylindrical member 104 are held by chucks 118, the chucks 118 being mounted on the stands 119. The chucks 118 are capable of rotation (electromechanical device is used to rotate the chucks 118 [not shown in the figure]), wherein the cylindrical member 104 is rotated (rotation of the cylindrical member 104 and hence of the soot porous body 121 is indicated by the arrow 106) while the burners 108 traverses the cylindrical member 104 longitudinally (the longitudinal traverse direction of the burners 108 is shown by arrows 109) or vice-versa. The burners 108 are supplied with silicon tetrachloride vapors 112 (or vapors of any other silicon contain material capable of forming silica), wherein silicon tetrachloride vapors 112 are obtained by vaporizing the liquid silicon tetrachloride 111 contained in a chamber 110. The temperature of the liquid silicon tetrachloride 111 is increased above its boiling point by means of heater 117, resulting in formation of silicon tetrachloride vapors 112, wherein a pipe 113 is connected between the chamber 110 and burners 108, to feed the burners 3 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 with the vapors of silicon tetrachloride 112 continuously. A self-generated vapor pressure forces the silicon tetrachloride vapors 112 towards the burners 108 through the pipe 113. The amount of liquid silicon tetrachloride vaporized is replenished with more liquid silicon tetrachloride from a tank (not shown in the figure), wherein mass flow controller controls the flow rate of liquid silicon tetrachloride 111. In accordance with the conventional ACVD method, gases supporting oxidation of silicon containing material, for example oxygen, and heat producing gases, for example hydrogen, methane etc., along with oxygen (for combustion) are supplied to the burners 108. The oxidation of silicon tetrachloride vapors 112 takes place resulting in the formation of silicon dioxide (SiO2), which is generally referred to as soot 107, wherein, the soot 107 formed is deposited onto the cylindrical member 104 and the part of the soot 107 that is not deposited onto the cylindrical member 104 is exhausted through the suction port 120 of the deposition machine 101. In accordance with the conventional ACVD method, controlling the flow rates of oxidation-supporting gas (oxygen) and heat-producing gases (hydrogen or methane) controls the temperature of soot deposition. The temperature of the soot deposition in-turn controls the density of the soot being deposited. As the temperature of the deposition is increased, by increasing the flow of oxygen and hydrogen, the density of the soot deposited is increased and vice versa, meaning thereby, the soot density is proportional to temperature of soot deposition or soot density is proportional to hydrogen-oxygen flow. In accordance with the conventional ACVD method, the initial deposition of soot 107 comprises dopant chemicals like germanium tetrachloride, wherein germanium tetrachloride vapors 115a is obtained by vaporizing the liquid germanium tetrachloride 115 contained in the chamber 114, wherein the heater(s) 117 heats the liquid germanium tetrachloride to a temperature above its boiling point. The vapors of germanium tetrachloride 115a are then carried over to the burners 108 through the pipe 116. The germanium tetrachloride vapors 115a move towards the burners 108 via pipe 116 under self-generated vapor pressure. The role of the dopant, that is, 4 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 germanium tetrachloride, is to increase index of refraction of soot, resulting in formation of the core region. The germanium tetrachloride vapor flow is terminated after desired core diameter is obtained. Any other dopant suitable for increasing the index of refraction of the core can be used in place of germanium tetrachloride. (In figure 1, the core soot is indicated by numeral 103 and the partial clad soot is indicated by numeral 102). In accordance with the conventional ACVD method the process of soot deposition continues until the required dimension of the soot porous body 121 is attained necessary for meeting desired core diameter in the optical fiber preform and the desired core-clad diameter ratio in the fiber. The pure soot deprived of any dopant or soot with a dopant, wherein the dopant is characterized by the property of decreasing the index of refraction of soot, is deposited as clad onto the core, after terminating the germanium tetrachloride vapor flow, resulting in a soot porous body with core and a part of clad. In an optical fiber about 90 % of the light travels through the core region. If the core region gets contaminated, the attenuation loss of the optical fiber increases. In accordance with the conventional ACVD method, a part of the cladding soot is deposited onto the core soot (soot with dopant), immediately after core deposition, wherein the contamination of the core region is prevented due to direct contact of core soot with the environment. It is observed that if the core part of the optical fiber preform is deposited without deposition of cladding and the core deposited soot porous body is taken out of the soot deposition machine, the core deposited soot porous body may acquire moisture from the surrounding atmosphere, wherein the moisture is observed to increase the attenuation in the wavelength region from about 1360 nm to about 1420 nm, in the optical fiber drawn therefrom; it also an observation that the core deposited soot porous body gets contaminated from the surrounding atmosphere (that is dust, metal parts etc.), there is increase in the attenuation loss in the wavelength region from about 1300 nm to about 1625 nm, rendering the optical fiber drawn therefrom unusable for desired applications. Thus, it is desirable to deposit a part of cladding onto the core, immediately after the core soot (that soot with dopant) is deposited. Accordingly, a particular ratio of clad to core is 5 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2(X)7 maintained to mitigate the above-mentioned problems, wherein this ratio is generally maintained in the range 2 to 5, preferably in the range 2.5 to 3.5 and more preferably in the range 2.7 to 3.4. Subsequent to completion of soot deposition, the cylindrical member 104 is removed from the soot porous body 121, to form hollow cylindrical soot porous body 201 defining a capillary 204 at the center [herein after referred to as hollow soot porous body] (figure 2A and figure 2B). The hollow soot porous body 201 comprises a core region 203, a cladding region 202 and the capillary 204. Now referring to figure 2A, figure 2B and figure 3, the hollow soot porous body 201 so formed in accordance with the conventional ACVD method, described above, contains large amount of hydroxyl ion or water or moisture as generally referred to. In order to remove the hydroxyl ion content of the hollow soot porous body 201, it is treated with gases, which chemically reacts with the hydroxyl ions. Halogens or compounds of halogen are generally used for such purpose. This step of removing the hydroxyl content from the hollow soot porous body 201 is known as dehydration or drying, wherein, in this step of dehydration or drying firstly a glass plug 308 is inserted into the end remote from the handle 205 of the hollow soot porous body 201 to close the mouth of the capillary 204, thereafter, the hollow soot porous body 201 is moved into a dehydration and sintering furnace 301. Figure 3 illustrates a dehydration and sintering furnace in accordance with the conventional ACVD method, wherein the dehydration and sintering furnace 301 comprises a high temperature resistant quartz glass body 305. The quartz glass body 305 has three openings, 302 for introducing the gases necessary for dehydration and sintering, opening 303 connected to suction unit (not shown in the figure) to remove the unreacted chemicals and reaction products formed during the dehydration and sintering processes and a mouth 311 to allow the hollow soot porous body to be inserted into the sintering furnace 301. The mouth 311 is covered with plate 306 during the dehydration and sintering processes. The temperature needed for the 6 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 dehydration and sintering process is attained by using one or more heaters 304. Accordingly, the hollow soot porous body 201 is suspended with the help of the suspending device 307 and the hollow handle 205, wherein the capillary 204 of hollow soot porous body 201 is connect to vacuum pump (not shown in figure) via the hollow handle 205 and a pipe 309. One end of the capillary 204 is thus connected to vacuum pump and the other end of the capillary 204 is closed with a glass plug 308. The hollow soot porous body 201 is rotated about the vertical axis of symmetry, in the direction as indicated by the arrow 310, wherein the hollow soot porous body 201 is evenly heated. In accordance with the ACVD method during the process of dehydration of the hollow soot porous body 201, it is heated to a temperature of about 1050°C in an atmosphere of halogens or compounds thereof to remove the hydroxyl content for a predetermined duration of time. Thereafter the dehydrated hollow soot porous body 201 is sintered to form a glass preform in an atmosphere of gases of halogens or compounds thereof at a temperature of about 1500°C. The step of sintering the hollow soot porous body 201 into glass is also known as vitrification or consolidation. In accordance with the conventional ACVD method preferably both the dehydration and sintering are carried out in same furnace. In accordance with the conventional ACVD method, the capillary 204 in the hollow soot porous body 201 is collapsed either during the sintering step or after the sintering step. After removal of the sintered glass preform (also called as mother preform) from the dehydration and sintering furnace, it is subjected to a process step of rod draw to form a plurality of core rods having a predetermined diameter. Optical fiber can also be drawn from the mother preform at this stage. Figure 4 illustrates a soot deposition machine 401 for deposition of over-cladding or extra-cladding of the optical fiber preform, wherein the core rod drawn is subjected to a step of soot deposition, resulting in a soot porous body containing core rod. This step of depositing soot 407 over the 7 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 core rod 403 is called over-cladding or extra-cladding. In accordance with the conventional ACVD method only a part of cladding is added during the core deposition process for the reasons discussed above. It is necessary to add more cladding [referred to as over-cladding hereinafter] to achieve the desired core-clad ratio in the final optical fiber, meaning thereby, the desired optical parameters like cutoff wavelength, dispersion etc., are attained in the optical fiber drawn therefrom. Before depositing soot onto the core rod 403, solid glass handles 404 are attached to both ends of the core rod 403, resulting in core rod assembly, wherein the solid glass handles 404 aids in handling the optical fiber preform and the soot porous body. The core rod assembly is transferred to a deposition machine 401 for deposition of cladding portion of the optical fiber preform. The core rod assembly is fixed in the soot deposition machine 401 with the help of chuck 418. The chucks 418, supported on the stands 419, hold the core rod assembly. The chucks 418 and hence the core rod assembly can be rotated in the direction shown by arrow 406, while depositing soot 407 onto the core rod assembly, using the burners 408. The burners 408 traverse the core rod assembly (indicated in figure by the arrows 409) or vice versa while depositing the soot 407 onto the core rod assembly. The soot deposition machine 401 differs from the soot deposition machine 101 in that it comprises burners 408 with larger diameter (size) and only one vaporizer 410 for vaporizing liquid silicon tetrachloride 411, wherein the silicon tetrachloride vapors 412 are supplied to the burners 408 in addition to oxygen (gas supporting combustion) and hydrogen or methane (gas producing heat). It is known that the soot delivering capacity of the burner is proportional to the diameter of the burner, meaning thereby, larger the burner diameter larger is soot-delivering capacity. The liquid silicon tetrachloride 411 is vaporized by means of heaters 417, wherein the liquid silicon tetrachloride is heated to a temperature above its boiling point, wherein the silicon tetrachloride vapor 412 is supplied to the burners 408 via pipe 413. Combustion of silicon tetrachloride vapor 412 in presence of hydrogen and oxygen produces the soot (SiO2) 407. The soot that is not deposited onto the core rod assembly and other reaction products are exhausted through the port 420 in the soot deposition machine 401. Thereafter, the soot porous body 421 so formed with the core rod 403, the 8 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 soot 402 and the handles 404 intact, is removed from the soot deposition machine 401 and is transferred to a dehydration and sintering furnace similar to that for dehydration and sintering of the hollow soot porous body 201. The soot porous body 421 is dehydrated and sintered in the dehydration and sintering furnace resulting in solid glass preform, also called as the daughter preform. The process of dehydration and sintering is similar as that for hollow soot porous body 201. The daughter preform is thereafter removed from the dehydration and sintering furnace and transferred to optical fiber drawing furnace, wherein optical fiber is drawn from the daughter preform. In accordance with the conventional ACVD method, it is known that the diameter of the cylindrical member 104 used for deposition is critical for two reasons; Firstly, if the diameter of cylindrical member 104 is larger, it is observed that the capillary 204 formed in the hollow soot porous body 201, after removal of cylindrical member 104 is larger, wherein the capillary 204 is found to be difficult to collapse and results in formation of seeds or bubbles in the centerline of the sintered preform. Secondly, if the diameter of the cylindrical member 104 is small, it is observed that more soot cannot be deposited, as there is always possibility of breaking of the cylindrical member 104 during the deposition owing to the weight of the deposited soot. Thus, it is necessary to have an optimized diameter of the cylindrical member 104, such that both the problems of formation of bubbles or seeds during the collapsing of large capillary 204 and possibility of breaking of the cylindrical member during the deposition owing to the weight of the deposited soot are mitigated. It is known in art to use the cylindrical member 104 of diameter in the range 5 mm to 9 mm, wherein the cylindrical member 104 is made up of alumina or quartz or any other material that has low thermal expansion coefficient so that the problems mentioned above are mitigated. It is also known that the soot deposition rate or the weight of soot deposited onto the cylindrical member 104 per unit time, at the beginning of soot deposition onto the cylindrical member 104 is low. As the soot accumulates on the cylindrical member 104, the diameter of the soot deposited on the cylindrical member increases and so the soot deposition 9 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 rate increases, wherein at the start of soot deposition the cross-sectional area of the cylindrical member 104 as encountered by the soot is small, thereby the soot deposition rate is low. As the diameter of soot deposited cylindrical member increases the cross-sectional area of the cylindrical member as encountered by the soot increases, thereby the soot deposition rate increases. In general the rate of soot deposition is proportional to the diameter of the cylindrical member 104, greater the diameter greater the soot deposition rate. It is observed that the soot deposition rate can be increased by increasing the delivery of the soot from the burner, keeping the cylindrical member size in the range 5 mm to 9 mm. But, the soot that is not deposited onto the cylindrical member 104 in this case is more as the cross-sectional area of the cylindrical member as encountered by the soot is less. This results in wastage of soot, in particular, since at the initial deposition stage dopant is used; there is wastage of dopant. This leads to increase in the cost of manufacture. In accordance with the conventional ACVD method, it is essential to deposit a part of cladding onto the core. This constraint of depositing a part of cladding onto the core limits the increase of soot deposition rate. This limitation is due to the fact that the burners 108 used for deposition of soot are having a certain capacity of soot delivery, beyond which the soot deposition rate cannot be increased. In order to further increase the soot deposition rate it is necessary to increase the burner 108 capacity for delivering soot, meaning thereby, it is necessary to use burners with large size for soot deposition. The Japanese patent laid open JP 07-242434 [herein after referred to as JP '434] attempts to increase the soot deposition rate (referred to as rate of sedimentation in JP '434). In accordance with JP '434, the soot deposition rate is increased by providing multiple burners of two or more kind of different diameters, wherein the burners are arranged alternately and traverse along the longitudinal direction of the cylindrical member while rotating the cylindrical member. When the cylindrical member is thin (at the start of soot deposition), only the burners with small diameter are used to 10 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 deposit the soot and when the diameter of soot deposited cylindrical member increases, burners having large diameter are switched-on to deposit the soot. However, it is observed that in order to provide multiple burners of two or more kind of different diameters, in accordance with the invention of JP '434, it is necessary to modify existing deposition machine and also inevitable to invest capital. It is observed by the inventors of the present invention that though JP '434 does indeed increase the soot deposition rate, but after completion of the dopant deposition, the apparatus for deposition of the dopant, that is, the vaporizer 114 for dopant, remains idle, meaning thereby the vaporizer cannot be utilized for any other deposition. It is an observation of the inventors of the present invention that about 20 % to about 40 % of the total deposition time is needed to deposit the core part and remaining about 60 % to about 80 % of time the clad part is deposited. Thus, about 60 % to about 80 % of the time, the vaporizer for the dopant remains idle. It is also an observation that the burners with smaller diameter used in the JP '434 remains idle during the deposition of soot with burner of larger diameter and burners of larger diameter remains unused when depositing soot with smaller burners. Further, it is known that the soot density of the deposited soot has to follow a specific profile, wherein the soot density decreases in radially outward direction from the center of the core. The inventors of the present invention have observed that if there is mismatch in the density of the soot deposited from the given profile problems like splitting of deposited soot in the soot porous body formed and further problems like slippage, bubbles etc., may occur in the sintered glass preform. It is observed that if the soot deposited has density mismatch, the presence of hydroxyl ions or moisture results in increase of attenuation in the wavelength region from about 1360 nm to about 1420 nm in the optical fiber drawn therefrom. The Japanese patent JP '434 teaches how to increase the soot deposition rate, but does not provides any means or method for matching the soot density when the 11 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 burners with small diameter stops and burners with large diameter starts soot deposition. Accordingly, it is understood that the JP '434 though capable of increasing the rate of soot deposition rate, the modification of the existing deposition machine and the investment of the capital is inevitable in order to provide multiple burners of two or more kind of different diameters, in accordance with the invention of JP '434. The JP '434 fails to utilize the vaporizer for about 60 % to about 80 % of total time, meaning thereby, the vaporizer 114 for dopant, remains idle, and the vaporizer cannot be utilized for any other deposition, when the cladding portion is being deposited. Another shortcoming of the JP '434 that when the burners with smaller diameter are used for soot deposition the burners with larger diameter remain idle and when the burners with larger diameter are used for soot deposition the burners of smaller diameter remains unused. Still another shortcoming of the JP '434 is that it fails to disclose means or method for matching the soot density when the burners with small diameter stops and burners with large diameter starts soot deposition, which is responsible for problems like splitting of deposited soot in the soot porous body formed and further problems like slippage, bubbles, interface irregularities, hydroxyl ions (and hence increased attenuation in the wavelength region from about 1360 nm to about 1420 nm ) etc., in the sintered glass preform. Yet another shortcoming of the JP '434 is that about 60 % to 80 % of the production capacity of the soot deposition machine is not utilized due to dopant vaporizer remaining idle. Accordingly, it is understood from the foregoing description that the utilization of soot deposition machine, increasing soot deposition rate of soot and thereby increasing the production capacity of the soot deposition 11 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 machines for manufacturing the soot porous body cannot be achieved by the method of conventional ACVD or the prior art. Need of the Invention: Therefore, there is a need to have a method for increasing the utilization of soot deposition machine, increasing the deposition rate of soot and thereby increasing the production capacity of the soot deposition machines for manufacturing the soot porous body and overcoming the above-described problems of the prior art. Objects of the Present Invention: The main object of the present invention is to provide a method for deposition of the soot porous body such that the utilization of soot deposition machine is increased, thereby decreasing the manufacturing time and cost of the soot porous body and hence that of the optical fiber. Another object of the present invention is to provide a method for deposition of the soot porous body such that rate of soot deposition is increased soot and thereby the production capacity of the soot deposition machine for manufacturing the soot porous body is increased. Still another object of the present invention is to provide a method for deposition of the soot porous body such that it is not necessary to modify existing deposition machine and also not inevitable to invest capital. Yet another object of the present invention is to provide a method for deposition of the soot porous body such that after completion of the dopant deposition, the apparatus for deposition of the dopant, that is, the vaporizer for dopant, do not remain idle. It is an object of the present invention to provide a method for deposition of the soot porous body such that the burners with smaller diameter do not remain idle during the deposition of soot with burner of 13 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 larger diameter and burners of larger diameter do not remain unused when depositing soot with smaller burners. It is another object of the present invention to provide a method for deposition of the soot porous body such that the problem of mismatch in the soot density when the burners with small diameter stops and burners with large diameter starts soot deposition, is mitigated and thereby the problems like splitting of deposited soot in the soot porous body formed and further problems like slippage, bubbles, interface regularities, hydroxyl ions etc., that may occur in the sintered glass preform are also mitigated. It is still another object of the present invention to provide a method such that the production capacity of the soot deposition machine is increased by about 60 % to 80 %. Other objects, advantages and preferred embodiments of the present invention will be apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present invention, but incorporated merely for illustrating the present invention. Brief Description of the Invention: It is understood from the foregoing description that the known methods for producing the soot porous body (which is further processed to form optical fiber preform) suffers from various shortcomings as herein described. The prior art method for producing the soot porous body has been observed to have shortcomings of not being suitable for increasing the utilization of the soot deposition machine, the soot deposition rate and thereby not suitable for increasing the production capacity of the soot deposition machine for manufacturing the soot porous body. Further, the method of the prior art have the shortcoming that the burners (both with smaller and larger diameter) and the dopant vaporizer 14 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 remains idle or unused, wherein the small diameter burners and the dopant vaporizer remains unused from about 60 % to about 80 % of the total time while the large diameter burners remain unused from about 20 % to about 40 % of the total time. Still further, the inventors of the present invention have observed that if the conventional methods described above are used for producing optical fiber preform, then about 10 % to 30 % of time is wasted, the production is hampered, that leads to increase in manufacturing cost Accordingly, the present invention relates to a method for the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the manufacturing process of soot porous body, without modifying the existing soot deposition machines, wherein the increasing soot deposition rate and thereby increasing the production capacity of the manufacturing process of soot porous body is achieved by increasing the utilization of the soot deposition machine, meaning thereby, the wastage of time due to the idle condition of the dopant vaporizer, the small and the larger diameter burners during the soot deposition is avoided thereby making the manufacturing process of the soot porous body more economical and thus overcomes the shortcomings of the prior art as described herein. In accordance with first preferred embodiment, the present invention relates to a method for increasing the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the soot deposition machines for manufacturing the soot porous body, without modifying the existing soot deposition machines, wherein the method of the present invention for soot deposition process comprises, manufacturing of soot porous body in two or more soot deposition machines. In accordance with second preferred embodiment, the present invention relates to a method for increasing the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the soot deposition machines for manufacturing the soot porous body, without modifying the existing soot deposition machines, 15 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 the soot porous body is prepared in stepwise manner, wherein soot is deposited to form a first intermediate soot porous body with core and a portion of clad in first deposition machine, and subsequently the said intermediate soot porous body is deposited with clad in second deposition machine to form a final soot porous body. In accordance with third preferred embodiment, the present invention relates to a method for increasing the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the soot deposition machines for manufacturing the soot porous body, without modifying the existing soot deposition machines, wherein the method of the present invention for soot deposition process comprises the steps; a) providing a first soot deposition machine with a plurality of first burners, having a diameter di, for depositing soot; b) providing a cylindrical member over said plurality of first burners; c) rotating said cylindrical member over said plurality of first burners; d) traversing said cylindrical member over said plurality of first burners or vice-versa; e) depositing soot on said cylindrical member to form an intermediate soot porous body having a diameter Di; f) providing a second soot deposition machine with a plurality of second burners, having a diameter d2, said diameter d2 of the second burners being greater than said diameter di of the first burners for depositing soot; g) transferring said intermediate soot porous body to said second soot deposition machine; h) providing said intermediate soot porous body over the said plurality of second burners; i) rotating said intermediate soot porous body over the said plurality of second burners; j) traversing said intermediate soot porous body over the said plurality of second burners or vice-versa; and k) depositing soot on said intermediate soot porous body using said plurality of second burners to form a corresponding final soot porous 16 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 body having diameter D2, said diameter D2 of the final soot porous body is greater than said diameter Di of the intermediate soot porous body. In accordance with fourth preferred embodiment, the present invention relates to a method for increasing the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the soot deposition machines for manufacturing the soot porous body, without modifying the existing soot deposition machines, wherein the method of the present invention for soot deposition process comprises the steps; a) providing a first soot deposition machine with a plurality of first burners, having a diameter di, for depositing soot; b) providing a cylindrical member over said plurality of first burners; c) rotating said cylindrical member over said plurality of first burners; d) traversing said cylindrical member over said plurality of first burners or vice-versa; e) depositing soot on said cylindrical member to form a first intermediate soot porous body having a diameter D1; f) providing a second soot deposition machine with a plurality of second burners, having a diameter d2, said diameter d2 of the second burner being greater than said diameter di of the first burner for depositing soot; g) transferring said first intermediate soot porous body to said second soot deposition machine; h) providing said first intermediate soot porous body over the said plurality of second burners; i) rotating said first intermediate soot porous body over the said plurality of second burners; j) traversing said first intermediate soot porous body over the said plurality of second burners or vice-versa; and k) depositing soot on said first intermediate soot porous body using said plurality of second burners to form a second intermediate soot porous body having a diameter D2; 1) providing a third soot deposition machine with a plurality of third burners, having a diameter d3, said diameter d3 of the third burner being 17 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 greater than said diameter of both first and second burners di and d2, for depositing soot; m) transferring said second intermediate soot porous body to said third soot deposition machine; n) providing said second intermediate soot porous body over the said plurality of third burners; o) rotating said second intermediate soot porous body over the said plurality of third burners; p) traversing said second intermediate soot porous body over the said plurality of third burners or vice-versa; and q) depositing soot on said second intermediate soot porous body using said plurality of third burners to form a corresponding final soot porous body having a diameter D3, said diameter D3 of the final soot porous body is greater than said diameter D2 of the second intermediate soot porous body which in turn is greater than said diameter Di of the first intermediate soot porous body. In accordance with one preferred embodiment of the present invention the first deposition machine is provided with one or more vaporizers for vaporizing one or more dopant, used to increase the refractive index of the core region, in addition to the silicon tetrachloride vaporizer. In accordance with other preferred embodiment of the present invention both the core and portion of cladding is deposited in the first deposition machine while the remaining part of the cladding is deposited in the second or second and third deposition machines. In accordance with another preferred embodiment of the present invention the intermediate soot porous body (both first and second) is forced cooled to room temperature in an inert atmosphere before transferring it to second or third deposition machine. In accordance with still another preferred embodiment of the present invention static charge generated on the intermediate soot porous body (both first and second) due to heat and rotation is discharged by using ionized nitrogen gas before transferring it to second or third deposition machine. 18 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 In accordance with yet another preferred embodiment of the present invention, the soot density of the intermediate soot porous body and the soot to be deposited in the subsequent steps is matched, wherein the hydrogen (Ha) flow (and oxygen (O2) flow) for deposition of soot, in subsequent step, onto the intermediate soot porous body is determined based on the diameter of the intermediate soot porous bodies. In accordance with another preferred embodiment of the present invention, the soot density of the intermediate soot porous body and the soot to be deposited in the subsequent steps is matched, wherein the hydrogen (H2) flow (and oxygen (O2) flow) for deposition of soot, in subsequent step, onto the intermediate soot porous body is determined using the formula: X = 8.73 + (0.624*Di) (1) Wherein, X is the hydrogen flow (standard liters per minute) to be determined Di (mm) is the diameter of the intermediate soot porous bodies (example, first in a two stage manufacturing process), and i = 1 to n, where n is the number of stages involved in preparing a final soot porous body. The oxygen flow is kept based on the 02/H2 ratio and the ratio is kept in between 0.35 to 0.5. Thus, the soot density of the soot being deposited onto the intermediate soot porous body is controlled by controlling the temperature, wherein the temperature is controlled by controlling the hydrogen flow in accordance with equation (1). Accordingly, in one embodiment, the present invention relates to a method for manufacturing soot porous body and soot porous body produced therefrom. In one embodiment, the present invention also relates to optical fiber preform produced from the soot porous body produced by employing method of the present invention. 19 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 In one embodiment, the present invention also relates to optical fiber drawn from the optical fiber preform produced from the soot porous body by employing the method of the present invention. The other embodiments of the present invention will be apparent from the following description when read in conjunction with the accompanying drawings. It is to be understood that both the foregoing general description and the following detailed description of the embodiments of the present invention, are intended to provide an overview for understanding the nature and character of the invention as it is claimed and not restricted to manufacture by the ACVD method or to various chemicals referred to, such as silicon tetrachloride, germanium tetrachloride, oxygen, hydrogen or methane etc. Brief Description of the Accompanying Figures: Figure 1 illustrates a soot deposition machine in accordance with the conventional Atmospheric Chemical Vapor Deposition (ACVD) method. 20 Figure 2A illustrates longitudinal cross-sectional view of a hollow soot porous body with centerline capillary, core and a part of cladding deposited in accordance with the conventional ACVD method. Figure 2B illustrates radially cross-sectional view of a hollow soot porous body with centerline capillary, core and a part of cladding deposited in accordance with the conventional ACVD method. Figure 3 illustrates a dehydration and sintering furnace for dehydration and sintering of hollow soot porous body and the soot porous body. Figure 4 illustrates a soot deposition machine in accordance with the conventional Atmospheric Chemical Vapor Deposition (ACVD) method for deposition of over-clad or extra-cladding onto the core rods. 20 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 Figure 5 illustrates a first soot deposition machine having first burners with diameter di in accordance with the first embodiment of the present invention. Figure 6 illustrates a second soot deposition machine having second burners with diameter d2 in accordance with the first embodiment of the present invention. Detailed Description of the Invention; Typically, an optical fiber preform can be manufactured by any of the conventional method, for example by ACVD method as described above. As described herein above, in accordance with the known methods, without modification of the existing machines, it is not possible to achieve the objective of increasing the utilization of soot deposition machine and increasing in deposition rate of soot, thereby increasing the production capacity of the manufacturing process of soot porous body and achieving a reduction in the wastage of time due to the idle condition of the dopant 20 vaporizer, the small and the larger diameter burners during the soot deposition making the manufacturing process of the soot porous body more economical. Therefore, the present invention aims to overcome the shortcomings of the prior art. Accordingly, in one embodiment, the present invention relates to a method for utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the manufacturing process of the soot porous body without modification of the existing machines. Accordingly, in another embodiment, the present invention relates to a method for manufacturing the soot porous body in short time and at low cost. 21 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 In accordance with the present invention, in order to achieve the objective of increase in utilization of soot deposition machine and increase deposition rate of soot without modifying the existing soot deposition machines, thereby increase the production capacity of the manufacturing process of soot porous body and reduce the wastage of time due to the idle condition of the dopant vaporizer, the small and the larger diameter burners during the soot deposition and make the manufacturing process of the soot porous body more economical and thus overcome the shortcomings of the prior art, the method of the present invention utilizes a first soot deposition machine for deposition of soot, wherein the first soot deposition machine is provided with a plurality of first burners having a diameter di, resulting in formation of a first intermediate soot porous body having diameter Di. The first intermediate soot porous body is transferred to a second soot deposition machine for soot deposition, wherein the second soot deposition machine is provided with a plurality of second burners having a diameter d2, the said diameter d2 of the second burners being greater than the diameter di of the first burners resulting in formation of final soot porous body having diameter D2. In accordance with first preferred embodiment, the present invention relates to a method for increasing the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the soot deposition machines for manufacturing the soot porous body, without modifying the existing soot deposition machines, wherein the method of the present invention for soot deposition process comprises, manufacturing of soot porous body in two or more soot deposition machines. In accordance with second preferred embodiment, the present invention relates to a method for increasing the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the soot deposition machines for manufacturing the soot porous body, without modifying the existing soot deposition machines, the soot porous body is prepared in stepwise manner, wherein soot is deposited to form a first intermediate soot porous body with core and a portion of clad in first deposition machine, and subsequently the said 27. CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 intermediate soot porous body is deposited with clad in second deposition machine to form a final soot porous body. In accordance with third preferred embodiment, the present invention relates to a method for increasing the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the soot deposition machines for manufacturing the soot porous body, without modifying the existing soot deposition machines, wherein the method of the present invention for soot deposition process comprises the 10 steps; a) providing a first soot deposition machine with a plurality of first burners, having a diameter di, for depositing soot; b) providing a cylindrical member over said plurality of first burners; c) rotating said cylindrical member over said plurality of first burners; d) traversing said cylindrical member over said plurality of first burners or vice-versa; e) depositing soot on said cylindrical member to form an intermediate soot porous body having a diameter D i; f) providing a second soot deposition machine with a plurality of second burners, having a diameter d2, said diameter d2 of the second burners being greater than said diameter di of the first burners for depositing soot; g) transferring said intermediate soot porous body to said second soot deposition machine; h) providing said intermediate soot porous body over the said plurality of second burners; i) rotating said intermediate soot porous body over the said plurality of second burners; j) traversing said intermediate soot porous body over the said plurality of second burners or vice-versa; and k) depositing soot on said intermediate soot porous body using said plurality of second burners to form a corresponding final soot porous body having diameter Da, said diameter D2 of the final soot porous body is greater than said diameter Di of the intermediate soot porous body. 23 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 Accordingly, it is observed that by transferring the intermediate soot porous body to a second soot deposition machine, the first soot deposition machine is available for deposition of another intermediate soot porous body. Since the diameter of the intermediate soot porous body is greater than the diameter of the cylindrical member and the diameter of the second burners provided in the second soot deposition machine are is greater than that in the first soot deposition machine, the soot deposition rate increases in the step (k) of depositing soot on the intermediate soot porous body, resulting in formation of final soot porous body in reduced time. Thus, the production capacity of the first soot deposition machine is increased. Referring to figure 5, in accordance with the first preferred embodiment of the present invention the soot porous body is manufactured by providing a first soot deposition machine 501 with a plurality of first burners 508, having diameter di, for depositing soot, wherein a cylindrical member 504 is provided over the plurality of first burners 508 while rotating and traversing the cylindrical member 504 (rotation indicated by arrow 506 and traverse movement indicated by arrows 509) over the plurality of first burners 508 or vice-versa, soot 507 is deposited on said cylindrical member 504 to form intermediate soot porous body 521 having a diameter Di. In accordance with the preferred embodiment of the present invention the intermediate soot porous body 521 is cooled to room temperature in an atmosphere of nitrogen (or other inert gas like helium, neon, argon etc.). In accordance with the present invention, preferably, the cooling is forced cooling, wherein the intermediate soot porous body 521 is place in a chamber with inert atmosphere and the intermediate soot porous body 521 is cooled in a controlled manner. Forced cooling helps in reducing the time needed for cooling the intermediate soot porous body 521. The provision of inert atmosphere prevents contamination of the intermediate soot porous body 521. It is an observation of the inventors of the present invention that the cooling of the intermediate soot porous body 521 is essential to prevent the splitting of the soot deposited onto it in the subsequent step of deposition. 24 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 Referring now to figure 5 and figure 6, the intermediate soot porous body 521 so formed is freed from static charge by treating with ionized nitrogen (or any other ionized inert gas), wherein the static free intermediate soot porous body 521 transferred to a second soot deposition machine 601 with a plurality of second burners 608, having a diameter d2, said diameter d2 of the second burners 608 being greater than said diameter di of the first burners 608 for depositing soot, wherein the said intermediate soot porous body 521 is positioned over the said plurality of second burners 608 as shown in the figure 6; the said intermediate soot porous body 521 is rotated and traversed (indicated by the arrow 606 and arrows 609 respectively) over the said plurality of second burners 608, wherein soot 607 is deposited on said intermediate soot porous body 521 using said plurality of second burners 608 to form a corresponding final soot porous body 621 having diameter D2, said diameter D2 of the final soot porous body 621 is greater than said diameter Di of the intermediate soot porous body 521. In accordance with the present invention, after formation of the final soot porous body 621, it is cooled to room temperature and the cylindrical member 504 is removed, resulting in formation of the hollow soot porous body with capillary at the center. The hollow soot porous body is dehydrated, sintered and the capillary is collapsed in accordance with the conventional method, to result in formation of a glass preform called mother preform. Either the mother preform is directly drawn into optical fiber or it is drawn into core rods. These core rods are over-cladded to result in formation of daughter preform, which can be drawn into optical fiber. In accordance with fourth preferred embodiment, the present invention relates to a method for increasing the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the soot deposition machines for manufacturing the soot porous body, without modifying the existing soot deposition machines, wherein the method of the present invention for soot deposition process comprises the steps; a) providing a first soot deposition machine with a plurality of first 35 burners, having a diameter di, for depositing soot; b) providing a cylindrical member over said plurality of first burners; 25 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 c) rotating said cylindrical member over said plurality of first burners; d) traversing said cylindrical member over said plurality of first burners or vice-versa; e) depositing soot on said cylindrical member to form a first intermediate soot porous body having a diameter Di; f) providing a second soot deposition machine with a plurality of second burners, having a diameter d2, said diameter d2 of the second burner being greater than said diameter di of the first burner for depositing soot; g) transferring said first intermediate soot porous body to said second soot deposition machine; h) providing said first intermediate soot porous body over the said plurality of second burners; i) rotating said first intermediate soot porous body over the said plurality of second burners; j) traversing said first intermediate soot porous body over the said plurality of second burners or vice-versa; and k) depositing soot on said first intermediate soot porous body using said plurality of second burners to form a second intermediate soot porous body having a diameter D2; 1) providing a third soot deposition machine with a plurality of third burners, having a diameter d3, said diameter d3 of the third burner being greater than said diameters of both first and second burners di and d2, for depositing soot; m) transferring said second intermediate soot porous body to said third soot deposition machine; n) providing said second intermediate soot porous body over the said plurality of third burners; 0) rotating said second intermediate soot porous body over the said plurality of third burners; p) traversing said second intermediate soot porous body over the said plurality of third burners or vice-versa; and q) depositing soot on said second intermediate soot porous body using said plurality of third burners to form a corresponding final soot porous body having a diameter D3, said diameter D3 of the final soot porous body is greater than said diameter D2 of the second intermediate soot porous 26 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 body which in turn is greater than said diameter Di of the first intermediate soot porous body. The rest of the steps are similar to that followed in the first embodiment of the present invention. Further, in accordance with the present invention the after formation of the final soot porous body, it is cooled to room temperature and the cylindrical member is removed, resulting in formation of the hollow soot porous body with capillary at the center. The hollow soot porous body is dehydrated, sintered and the capillary is collapsed in accordance with the conventional method, to result in formation of a glass preform called mother preform. Either the mother preform is directly drawn into optical fiber or it is drawn into core rods. These core rods are over-cladded to result in formation of daughter preform, which can be drawn into optical fiber. In accordance with one preferred embodiment of the present invention the first deposition machine 501 is provided with one or more vaporizers for vaporizing one or more dopant 514, used to increase the refractive index of the core region, in addition to the silicon tetrachloride vaporizer 510, that is, core region (soot with dopant) is deposited, wherein the dopant supply is terminated after a predetermined diameter of soot with dopant is obtained, wherein, only soot is deposited onto the core region to form a part of cladding. In accordance with other preferred embodiment of the present invention core and a portion of cladding is deposited in the first deposition machine while the remaining part of the cladding is deposited in the second and third soot deposition machines, wherein deposition of a portion of cladding in the first deposition machine immediately after core deposition, prevents contamination of the core region due to direct contact of core soot with the environment, meaning thereby, the problems of increase in the attenuation in the wavelength region from about 1360 nm to about 1420 nm, in the optical fiber drawn therefrom due to absorption of moisture from the surrounding atmosphere and increase the attenuation loss in the wavelength region from about 1300 nm to about 1625 nm due which the 27 CONFIDENTIAL PA/043/SPECIFICATION V-l I '109.2007 optical fiber drawn therefrom becomes unusable for desired applications due to contamination of deposited soot porous body, in particular the core region, from the surrounding atmosphere are mitigated. In accordance with another preferred embodiment of the present invention the intermediate soot porous body (both first and second) is forced cooled to room temperature in an inert atmosphere before transferring it to second or third deposition machine. It is an observation of the inventors of the present invention that if soot is deposited onto the hot intermediate soot porous body (both first and second) splitting of soot deposited occurs. In accordance with still another preferred embodiment of the present invention static charge generated on the intermediate soot porous body (both first and second) due to heat and rotation is discharged by using ionized inert gases for example nitrogen, helium, argon, neon etc, before transferring it to second or third deposition machine, wherein the step of discharging the static charge assures that the surface of the intermediate soot porous body does not get contaminated due to the possibility of attraction of dust or any other form of contamination due to presence of static charge while transferring or handling of the intermediate soot porous body. In accordance with yet another preferred embodiment of the present invention the soot density of the intermediate soot porous body and the soot to be deposited in the subsequent steps has to be matched. It is observed that if there is a variation in the soot density, that is, if the density of the soot deposited onto the intermediate soot porous body (both first and second) is less than the density of the soot of the intermediate soot porous body (both first and second) then there is splitting of soot and if the density of the soot being deposited is greater than the intermediate soot porous body (both first and second) then the hydroxyl ions in the soot porous body cannot be completely removed, in the subsequent step of dehydration, as the hydroxyl ions are locked in the soot porous body in-addition to the problems of bubbles, slippage etc. The hydroxyl ions in the soot porous body results in increase in attenuation in the resulting optical fiber in the wavelength region from about 1360 nm to about 1420 nm. Thus, it is necessary to match the 28 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 density of the soot to be deposited onto the intermediate soot porous body (both first and second) in order to mitigate the above-mentioned problems. In accordance with this embodiment, the soot density of the intermediate soot porous body and the soot to be deposited in the subsequent steps is matched, wherein the hydrogen (H2) flow (and oxygen (O2) flow) for deposition of soot, in subsequent step, onto the intermediate soot porous body is determined based on the diameter of the intermediate soot porous bodies. 10 Accordingly, the soot density of the intermediate soot porous body and the soot to be deposited in the subsequent steps is matched, wherein the hydrogen (H2) flow (and oxygen (O2) flow) are determined using the formula: X = 8.73 + (0.624*Di) (1) Wherein, X is the hydrogen flow (standard liters per minute) to be determined, Di (mm) is the diameter of the intermediate soot porous bodies, and i = 1 to n, where n is the number of stages involved in preparing a final soot porous body. The oxygen flow is kept based on the 02/H2 ratio and the ratio is kept in between 0.35 to 0.5. Accordingly, the soot density of the intermediate soot porous body and the soot to be deposited in the subsequent steps is matched such that the soot density follows the formula 1, meaning thereby, the difference between the soot density of the soot layer being deposited on the intermediate soot porous body and the density of the soot of the soot porous body is less than or equal to 0.05. In accordance with the present invention it is observed that it is not necessary to provide multiple burners of two or more kind of different diameters and hence not necessary to modify existing deposition machine 29 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 and also to invest capital as in the case of invention of the prior art patent JP '434. In accordance with the present invention after completion of the dopant deposition, the apparatus for deposition of the dopant, that is, the vaporizer 114 for dopant, does not remain idle, meaning thereby the vaporizer can be utilized for any other deposition. Thus, about 75 % of the total deposition time needed to deposit the clad part is saved. In accordance with the present invention the burners with smaller diameter are in separate soot deposition machine and the burners with large diameter are in another soot deposition machine, thus there is no issue of burners remaining idle as in the case of JP '434, wherein during the deposition of soot with burner of larger diameter, burners with small diameter remain idle and burners of larger diameter remain unused when depositing soot with smaller burners. In accordance with the present invention the soot density while depositing the soot onto the intermediate soot porous body is matched by using the formula: X = 8.73 + (0.624*D;) (1) Wherein, X is the hydrogen (H2) flow (standard liters per minute) to be determined, Di (mm) are the diameters of the intermediate soot porous body, and i = 1 to n, where n is the number of stages involved in preparing a final soot porous body. The oxygen flow is kept based on the 02/H2 ratio and the ratio is kept in between 0.35 to 0.5. herein the inventors of the present invention have observed that there is no mismatch in the density of the soot deposited from the given profile and the problems like splitting of deposited soot in the soot porous body formed and further problems like slippage, bubbles, interface irregularities etc., do not occur in the sintered glass preform. 30 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 Accordingly, it is understood that the present invention is capable of increasing the rate of soot deposition rate, without modification of the existing deposition machine and the investment of the capital is inevitable in accordance with the invention of JP '434. In accordance with the present invention the vaporizer for dopant is utilized to its full extent and does not remains idle as in the case of the Japanese patent JP '434, wherein JP '434 fails to utilize the vaporizer for about 60 % to about 80 % of the total. 10 In accordance with the present invention since the burners with small diameter and the burners with large diameter are provided in separate soot deposition machine the shortcoming of the Japanese patent JP '434 that when the burners with smaller diameter are used for soot deposition the burners with larger diameter remain idle and when the burners with larger diameter are used for soot deposition the burners of smaller diameter remains unused, is eliminated. In accordance with the present invention the production capacity of the first soot deposition machine is increased by about 60 % to 80 %. It is an advantage of the present that the utilization of soot deposition machine is increased, thereby decreasing the manufacturing time and cost of the soot porous body and hence that of the optical fiber. It is another advantage of the present invention that rate of soot deposition is increased soot and thereby the production capacity of the soot deposition machine for manufacturing the soot porous body is increased. It is still another advantage of the present invention that it is not necessary to modify existing deposition machine and also not inevitable to invest capital. It is yet another advantage of the present invention that after completion of the dopant deposition, the apparatus for deposition of the dopant, that is, the vaporizer for dopant, does not remain idle. 31 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 This is a further advantage of the present invention that the burners with smaller diameter do not remain idle during the deposition of soot with burner of larger diameter and burners of larger diameter do not remain unused when depositing soot with smaller burners. This is still further advantage of the present invention that the problem of mismatch in the soot density when the burners with small diameter stops and burners with large diameter starts soot deposition, is mitigated and thereby the problems like splitting of deposited soot in the soot porous body formed and further problems like slippage, bubbles etc., that may occur in the sintered glass preform are also mitigated. This is yet another advantage of the present invention that the preparation time of the final soot porous body is reduced by about 10 % to about 30 %. It has been observed that the optical fiber preform produced in accordance with the present invention do not have bubbles and/or interface irregularities. It is an observation that the optical fiber produced in accordance with the present invention has an attenuation at about 1310 nm of less than or equal to 0.310 dB/Km, at about 1550 nm an attenuation of less than or equal to 0.190 dB/Km and in the wavelength range of 1360 nm to 1420 nm an attenuation of less than or equal to 0.30 dB/Km. It may be noted that various terms, for example cylindrical member, soot porous body, hollow soot porous body, capillary, glass preform, core rod, mother preform, daughter preform, intermediate soot porous body, first intermediate soot porous body, second intermediate soot porous body, burners, soot deposition machine etc., as employed herein are merely intended to illustrate the present invention and are not intended to restrict the scope of the present invention. It is obvious for the persons skilled in the art that alternative terms may also be employed to describe the present invention without deviating from the intended scope of the present invention. 32 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 It may also be noted that the presently disclosed method has been described with reference to ACVD method. However, the present invention method is suitable even for other alternative methods known for producing soot porous body and hence the optical fiber preforms. It may also be noted that the presently disclosed method is suitable for producing soot porous body, wherein only the extra-cladding is deposited onto the core rod assembly. The present invention is now elaborated with the help of following examples, which are not intended to limit its scope. Example 1 (Prior art - Conventional ACVD method): A cylindrical member with a hollow handle was fixed in a soot deposition machine. The soot deposition machine was provided with two vaporizers one for formation of silicon tetrachloride vapors and other for the dopant vapors. The soot deposition machine was also provided with a pair of burners with diameter of 65 mm. The soot was deposited onto the cylindrical member while rotating and traversing the cylindrical member in accordance with the conventional ACVD method, to form core and clad of the soot porous body. During the soot deposition process, the dopant germanium tetrachloride vapors were mixed with the soot to form the core portion of the soot porous body and later the supply of the germanium tetrachloride was terminated. Approximately, 900 g of soot with the dopant was deposited onto the cylindrical member as core soot, wherein the deposition of 900 g of soot with the dopant took 180 minutes. Thereafter, 8100 g of soot deprived of any dopant was deposited as clad onto the core soot, wherein deposition of pure 8100 g of soot as cladding took 540 minutes. After formation of the final soot porous body with core and cladding with diameter of 170 mm, the cylindrical member was removed from the soot porous body to form hollow soot porous body with capillary therein. The hollow soot porous body was dehydrated at a temperature of 1050°C in an atmosphere of chlorine and helium gas. The dehydrated hollow soot porous body was sintered at a temperature of 1500°C in a sintering furnace wherein chlorine and helium gases for sintering were provided, resulting in formation of mother preform. The mother preform was drawn into plurality of core rods. Solid handles were 33 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 attached to one of the core rods and extra-cladding was deposited onto the core rod assembly. The soot porous body so formed was dehydrated and sintered in accordance with the conventional method to form mother preform. The mother preform was drawn into plurality of core rods. Handles were attached to one of the core rod and extra-cladding was deposited onto it. The extra-cladded soot porous body was dehydrated and sintered to form daughter preform, which was drawn into fiber. The fiber characteristics, that is, the cutoff wavelength, the attenuation etc., were found to be the desired ones. It was observed that the deposition of 900 g of soot with dopant takes only 180 minutes while deposition of 8100 g of cladding took 540 minutes. Thus, about 25 % of time was needed to deposit the core portion while 75 % was needed to deposit cladding portion. Thus, for about 75 % of the time the vaporizer for dopant remained unused during the complete deposition process. The burner pair with the diameter 65 mm were used to deposit both the core and cladding. The average soot deposition rate was observed to be 12.5 g/min. Example 2 (Prior art - JP '434): A cylindrical member with a hollow handle was fixed in a soot deposition machine. The soot deposition machine was provided with two vaporizers one for formation of silicon tetrachloride vapors and other for the dopant vapors. The soot deposition machine was also provided with a pair of two kind burners with diameters of 65 mm and 95 mm arranged alternately in accordance with the JP '434. Using the burner pair with the diameter of 65 mm the soot was with dopant germanium tetrachloride was deposited onto the cylindrical member while rotating and traversing the cylindrical member over the burners, in accordance with the Japanese patent JP '434 to form core and clad of the soot porous body. Later the supply of the dopant was terminated. Approximately, 900 g of soot with the dopant was deposited onto the cylindrical member as core soot, wherein the deposition of 900 g of soot with the dopant took 180 minutes. Further, the cladding was deposited onto the core soot using the burner pair with diameter of 95 mm. About 8100 g of soot deprived of cladding was deposited as clad onto the core soot, wherein deposition of pure 8100 g of soot as cladding took 480 minutes. The hydrogen flow was kept 38 slpm (standard liters per minute) while depositing with the 95 mm burner. After formation of the final soot porous body with 34 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 core and cladding with a diameter of 172 mm, the cylindrical member was removed from the soot porous body to form hollow soot porous body with capillary therein. The hollow soot porous body was dehydrated at a temperature of 1050°C in an atmosphere of chlorine and helium gas. The dehydrated hollow soot porous body was sintered at a temperature of 1500°C in a sintering furnace wherein chlorine and helium gases for sintering were provided, resulting in formation of mother preform. The mother preform was drawn into plurality of core rods. Solid handles were attached to one of the core rods and extra cladding was deposited onto the core rod assembly. The soot porous body so formed was dehydrated and sintered in accordance with the conventional method to form mother preform, which was drawn into 100 km of fiber. It was observed that the deposition of 900 g of soot with dopant takes only 180 minutes while deposition of 8100 g of cladding took 480 minutes. Thus, 27 % of time was needed to deposit the core portion while 73 % was needed to deposit cladding portion. In comparison with example 1, the total time needed for complete deposition, that is, core and cladding is less by 60 minutes. Thus, for 73 % of the time the vaporizer for dopant and the burners with diameter 65 mm remained unused during the complete deposition process, while the burners with diameter 95 mm remained unused for 27 % of the time. The average soot deposition rate was observed to be 13.6 g/min, which was better than the conventional ACVD method. Further, it was observed that since the density of the soot deposited by the burner pair with diameter of 95 mm was not matched with the density of soot on the cylindrical member, deposited with the burner pair of 65 mm, bubbles were observed at the place on the soot preform where the changeover was taken from 65 mm burner to 95 mm burner. Example 3 (Present invention - First embodiment): A cylindrical member with a hollow handle was fixed in a first soot deposition machine, wherein the soot first deposition machine was provided with two vaporizers one for formation of silicon tetrachloride vapors and other for the dopant vapors. The first soot deposition machine was also provided with a pair of first burners with diameter of 65 mm. The soot was deposited onto the cylindrical member while rotating and traversing the cylindrical member, to form a core and a portion of clad of the soot porous 35 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 body. During the soot deposition process, the dopant germanium tetrachloride vapor was mixed with the soot to form the core portion of the soot porous body and later the supply of the dopant was terminated. Approximately, 900 g of soot with the dopant was deposited onto the cylindrical member as core soot, wherein the deposition of 900 g of soot with the dopant took 180 minutes. Thereafter, 1000 g of soot deprived of dopant was deposited as a portion of clad onto the core soot, wherein deposition of pure 1000 g of soot as cladding took 120 minutes. Thus, an intermediate soot porous body with weight of 1900 g and diameter of 72 mm was formed with core and a portion of clad. The static charge on the intermediate soot porous body was discharged with ionized nitrogen gas. Further, the intermediate soot porous body was removed from the first soot deposition machine and transferred to a chamber with nitrogen gas (inert gas) atmosphere, wherein the intermediate soot porous body was forced cooled to room temperature. After force cooling of the intermediate soot porous body, the static charge on the intermediate soot porous body was discharged with ionized nitrogen gas, thereafter the intermediate soot porous body was transferred to a second soot deposition machine provided with a pair of second of burners having diameters 95 mm, greater than the pair of first burners. The remaining part of cladding, that is, 7100 g of soot was deposited onto the intermediate soot porous body using the pair of second burners to form final soot porous body with diameter 174 mm. The hydrogen flow for deposition of the soot onto the intermediate soot porous body of diameter 72 mm was determined using the equation (1) to match the density of soot to be deposited with the density of intermediate soot porous body. X = 8.73 + (0.624*D,) (1) In this case D1 = 72 mm. The hydrogen flow determined in accordance with the equation (1) is X = 8.73 + (0.642*72) = 53.7 slpm. The soot deposition was started onto the intermediate soot porous body by keeping the hydrogen flow 53.7 slpm and oxygen flow 22 slpm. The deposition of 7100 g of soot took 250 minutes. The cylindrical member was removed from the final soot porous body to form hollow soot porous body with capillary therein. The hollow soot porous body was dehydrated at a temperature of 1050°C in an atmosphere of chlorine and helium gas. The dehydrated hollow soot porous body was sintered at a temperature of 36 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 1500°C in a sintering furnace wherein chlorine and helium gases for sintering were provided, resulting in formation of mother preform. The mother preform was drawn into plurality of core rods. Solid handles were attached to one of the core rods and extra cladding was deposited onto the core rod assembly. The soot porous body so formed was dehydrated and sintered in accordance with the conventional method similar to daughter preform. It was observed that the deposition of 900 g of soot with dopant takes only 180 minutes while deposition of 1000 g of cladding took 120 minutes. Thus, about 180 minutes were needed to deposit the core portion while 370 minutes were needed to deposit cladding portion. The average soot deposition rate was observed to be 16.4 g/min. It was further observed that there were no bubbles or interface irregularities formed in the resulting sintered mother preform. Example 4 (Present invention - Second embodiment): A cylindrical member with a hollow handle was fixed in a first deposition machine, wherein the first deposition machine was provided with two vaporizers one for formation of silicon tetrachloride vapors and other for the dopant vapors. The first deposition machine was also provided with a pair of first burners with diameter of 65 mm. The soot was deposited onto the cylindrical member while rotating and traversing the cylindrical member, to form a core and a portion of clad of the soot porous body. During the soot deposition process, the dopant germanium tetrachloride vapor was mixed with the soot to form the core portion of the soot porous body and later the supply of the dopant was terminated. Approximately, 900 g of soot with the dopant was deposited onto the cylindrical member as core soot, wherein the deposition of 900 g of soot with the dopant took 180 minutes. Thereafter, 1000 g of soot deprived of cladding was deposited as a portion of clad onto the core soot, wherein deposition of pure 1000 g of soot as cladding took 120 minutes. Thus, first intermediate soot porous body with weight of 1900 g and diameter of 73 mm was formed with core and a portion of clad. The static charge on the first intermediate soot porous body was discharged with ionized nitrogen gas. Further, the first intermediate soot porous body was removed from the first soot deposition machine and transferred to a chamber with nitrogen gas (inert gas) atmosphere, wherein the first intermediate soot porous body was forced cooled to room temperature. After cooling of the first 37 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 intermediate soot porous body, the static charge on the first intermediate soot porous body was discharged with ionized nitrogen gas, thereafter the first intermediate soot porous body was transferred to a second soot deposition machine provided with a pair of second of burners having diameters 95 mm, greater than the pair of first burners. A soot of 3000 g was deposited onto the first intermediate soot porous body using the pair of second burners to form a second intermediate soot porous body with diameter 140 mm. The deposition of 3000 g of soot took 100 minutes for deposition using the burners with 95 mm diameter. The hydrogen flow for deposition of the soot onto the first intermediate soot porous body of diameter 73 mm was determined using the equation (1) to match the density of soot to be deposited with the density of first intermediate soot porous body. X = 8.73 + (0.624*Di) (1) In this case Dl = 72 mm. The hydrogen flow determined in accordance with the equation (1) is X = 8.73 + (0.642*73) = 54.3 slpm. The soot deposition was started onto the first intermediate soot porous body by keeping the hydrogen flow 54.3 slpm and oxygen flow 21.72 slpm. Further, the second intermediate soot porous body with diameter of 140 mm was removed from the second soot deposition machine and transferred to a chamber with nitrogen gas (inert gas) atmosphere, wherein the second intermediate soot porous body was forced cooled to room temperature. After cooling of the second intermediate soot porous body, the static charge on the second intermediate soot porous body was discharged with ionized nitrogen gas, thereafter the second intermediate soot porous body was transferred to a third soot deposition machine provided with a pair of third of burners having diameters 105 mm, the diameter being greater than the pair of first burners and second burners. The remaining part of cladding, that is, 4100 g of soot was deposited onto the second intermediate soot porous body using the pair of third burners to form a final soot porous body with diameter 171 mm. The hydrogen flow for deposition of the soot onto the intermediate soot porous body of diameter 140 mm was determined using the equation (1) to match the density of soot to be deposited with the density of second intermediate soot porous body. X = 8.73 + (0.624*D.) (1) 38 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 In this case Dl = 72 mm. The hydrogen flow determined in accordance with the equation (1) is X = 8.73 + (0.642* 140) = 96.1 slpm. The soot deposition was started onto the second intermediate soot porous body by keeping the hydrogen flow 96.1 slpm and oxygen flow 38.44 slpm. The cylindrical member was removed from the final soot porous body to form hollow soot porous body with capillary therein. The hollow soot porous body was dehydrated at a temperature of 1050°C in an atmosphere of chlorine and helium gas. The dehydrated hollow soot porous body was sintered at a temperature of 1500°C in a sintering furnace wherein chlorine and helium gases for sintering were provided, resulting in formation of mother preform. The mother preform was drawn into plurality of core rods. Solid handles were attached to one of the core rods and extra cladding was deposited onto the core rod assembly. The soot porous body so formed was dehydrated and sintered in accordance with the conventional method to form daughter preform. It was observed that the deposition of 900 g of soot with dopant takes only 180 minutes while deposition of 1000 g of cladding took 120 minutes. Thus, about 180 minutes were needed to deposit the core portion while 340 minutes were needed to deposit cladding portion. The average soot deposition rate was observed to be 17.3 g/min. It was further observed that there were no bubbles or interface irregularities formed in the resulting sintered mother preform. It is clear from the foregoing examples [ 1 to 4] that the soot deposition rate does increase. Similarly, it is also clear that the production capacity of the first soot deposition machine also increases, as it is not engaged for deposition of cladding as it was in the case of conventional ACVD method or the Japanese patent JP'434. 39 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 What is claimed is: 1. A method for increasing the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the soot deposition machines for manufacturing the soot porous body, without modifying the existing soot deposition machines, wherein the method for soot deposition process comprises, manufacturing of soot porous body in two or more soot deposition machines. 2. A method for increasing the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the soot deposition machines for manufacturing the soot porous body, without modifying the existing soot deposition machines, the soot porous body is prepared in stepwise manner, wherein the method for soot deposition process comprises depositing soot to form a first intermediate soot porous body with core and a portion of clad in first deposition machine, and subsequently depositing clad soot onto the said intermediate soot porous body in subsequent deposition machines to form a final soot porous body. 3. The method as claimed in claim 2, wherein said first soot deposition machine is provided with one or more vaporizers for vaporizing one or more dopant in addition to a silicon tetrachloride vaporizer, the dopant being used to increase the refractive index of the core region, wherein the dopant supply is terminated after a predetermined diameter of soot with dopant is obtained, and thereafter, only soot is deposited onto the core region to form a part of cladding material. 4. The method as claimed in claim 1, wherein said method for increasing the utilization of soot deposition machine, increasing soot deposition rate and 30 thereby increasing the production capacity of the soot deposition machine for manufacturing the soot porous body, without modifying the existing soot deposition machines, the method comprising the steps of: a) providing a first soot deposition machine with a plurality of first burners, each having a diameter dl, for depositing soot; 40 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 b) providing a cylindrical member over said plurality of first burners; c) rotating said cylindrical member over said plurality of first burners; d) traversing said cylindrical member over said plurality of first burners or traversing said plurality of first burners over said cylindrical member; e) depositing soot on said cylindrical member to form an intermediate soot porous body having a diameter Dl; f) providing a second soot deposition machine with a plurality of second burners, each having a diameter d2, said diameter d2 of the second burners being greater than said diameter dl of the first burners for depositing soot; g) transferring said intermediate soot porous body to said second soot deposition machine; h) providing said intermediate soot porous body over the said plurality of second burners; i) rotating said intermediate soot porous body over the said plurality of second burners; j) traversing said intermediate soot porous body over the said plurality of second burners or traversing said plurality of second burners over said intermediate soot porous body; and k) depositing soot on said intermediate soot porous body using said plurality of second burners to form a corresponding final soot porous body having diameter D2, said diameter D2 of the final soot porous body is greater than said diameter Dl of the intermediate soot porous body, wherein the burners with smaller diameter are in a one soot deposition machine and the burners with large diameter are in another soot deposition machine enables to have high deposition rate of soot porous body and also both the burners can be put to use simultaneously, thereby increase 41 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 production capacity of soot deposition machines, without the modification of existing soot deposition machines. 5. The method as claimed in claim 4, the method further comprises of the step 5 wherein said intermediate soot porous body is cooled to room temperature in an inert gas atmosphere, where the inert gas is any one from the group but not limited to nitrogen, helium, neon, and argon, before being transferred to said second soot deposition machine. 6. The method as claimed in claim 4, the method further comprises of the step wherein said intermediate soot porous body is freed from static charge by treating with an ionized inert gas, the inert gas being any one from the group but not limited to nitrogen, argon, helium, and neon. 7. The method as claimed in claim 4, wherein said final soot porous body having diameter D2 is treated as a second intermediate soot porous body, the method further comprising the steps of: a) providing a third soot deposition machine with a plurality of third burners, each having a diameter d3, said diameter d3 of said third burners being greater than said diameter of both first and second burners dl and d2, for depositing soot; b) transferring said second intermediate soot porous body to said third soot deposition machine; c) providing said second intermediate soot porous body over the said plurality of third burners; d) rotating said second intermediate soot porous body over the said plurality of third burners; e) traversing said second intermediate soot porous body over the said plurality of third burners or traversing said plurality of third burners over said second intermediate soot porous body; and 42 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 f) depositing soot on said second intermediate soot porous body using said plurality of third burners to form a corresponding final soot porous body having a diameter D3, said diameter D3 of the final soot porous body is greater than said diameter D2 of the second intermediate soot porous body which in turn is greater than said diameter D1 of the first intermediate soot porous body. 8. The method as claimed in claim 4, wherein the soot density of said intermediate soot porous body and the soot to be deposited in the subsequent steps are matched by determining the hydrogen flow of subsequent deposition machine. 9. The method as claimed in claim 8, wherein the hydrogen flow is determined based on the diameter of the intermediate soot porous body to avoid problems like splitting of deposited soot in the soot porous body formed, slippage, bubbles, and interface irregularities. 10. The method as claimed in claim 9, the method further comprising the step wherein the hydrogen flow is determined using the formula: 20 X = 8.73 + (0.624*Di) Wherein, X is the hydrogen flow (standard liters per minute), Di (mm) is the diameter of the intermediate soot porous bodies, and i = 1 to n, where n is the number of stages involved in preparing final soot porous body. 11. The method as claimed in claim 9, the method further comprising the step 30 wherein the oxygen flow is determined based on the 02/H2 ratio and the ratio is kept in between 0.35 to 0.5. 12. The soot porous body produced in accordance with any one of the claims 1 to 11. 43 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.2007 13. An optical fiber preform without having bubbles and/or interface irregularities when produced in accordance with any one of the claims 1 to 12. 14. An optical fiber having an attenuation at about 1310 nm of less than or 5 equal to 0.310 dB/Km, at about 1550 nm an attenuation of less than or equal to 0.190 dB/Km and in the wavelength range of 1360 nm to 1420 nm an attenuation of less than or equal to 0.30 dB/Km when produced in accordance with any of the claims 1 to 13. 15. The method as claimed in claim 3, the manufacturing time of soot porous body is reduced by about 10% to 30%. 16. The method as claimed in claim 3, wherein the production capacity of the first soot deposition machine for producing intermediate soot porous body is 15 increased by about 60 % to 80 %. 44 CONFIDENTIAL PA/043/SPECIFICATION V-l 19.09.201)7 Abstract A method for increasing the utilization of soot deposition machine, increasing soot deposition rate and thereby increasing the production capacity of the soot deposition machine for manufacturing the soot porous body, without modifying the existing soot deposition machines is disclosed. The method involves multiple stages of soot deposition using multiple soot deposition machines, each machine having a plurality of burners, the diameter of burners for each machine being different, thus controlling the deposition rate and at the same time ensuring that the burners are not idle. The method further provides for matching the density of soot deposition across machines to avoid problems like splitting of deposited soot in the soot porous body formed, slippage, bubbles, and interface irregularities. 45 CONFIDENTIAL

Documents:

1879-MUM-2007-ABSTRACT(18-10-2012).pdf

1879-MUM-2007-ABSTRACT(31-5-2010).pdf

1879-MUM-2007-ABSTRACT(5-9-2012).pdf

1879-mum-2007-abstract.doc

1879-mum-2007-abstract.pdf

1879-MUM-2007-CLAIMS(AMENDED)-(18-10-2012).pdf

1879-MUM-2007-CLAIMS(AMENDED)-(31-5-2010).pdf

1879-mum-2007-claims.doc

1879-mum-2007-claims.pdf

1879-mum-2007-correspondence(15-5-2008).pdf

1879-mum-2007-correspondence(ipo)-(3-5-2010).pdf

1879-MUM-2007-CORRESPONDENCE(IPO)-(31-5-2010).pdf

1879-mum-2007-correspondence-received.pdf

1879-mum-2007-description (provisional).pdf

1879-MUM-2007-DRAWING(18-10-2012).pdf

1879-MUM-2007-DRAWING(31-5-2010).pdf

1879-mum-2007-drawings.pdf

1879-MUM-2007-FORM 1(18-10-2012).pdf

1879-MUM-2007-FORM 1(31-5-2010).pdf

1879-mum-2007-form 13(15-5-2008).pdf

1879-mum-2007-form 13(31-5-2010).pdf

1879-MUM-2007-FORM 13(5-9-2012).pdf

1879-MUM-2007-FORM 2(MARKED COPY)-(31-5-2010).pdf

1879-MUM-2007-FORM 2(TITLE PAGE)-(18-10-2012).pdf

1879-MUM-2007-FORM 2(TITLE PAGE)-(31-5-2010).pdf

1879-MUM-2007-FORM 26(18-10-2012).pdf

1879-MUM-2007-FORM 26(31-5-2010).pdf

1879-MUM-2007-FORM 3(18-10-2012).pdf

1879-MUM-2007-FORM 5(18-10-2012).pdf

1879-MUM-2007-FORM 5(31-5-2010).pdf

1879-mum-2007-form-1.pdf

1879-mum-2007-form-18.pdf

1879-mum-2007-form-2.doc

1879-mum-2007-form-2.pdf

1879-mum-2007-form-26.pdf

1879-mum-2007-form-3.pdf

1879-mum-2007-form-5.pdf

1879-mum-2007-form-9.pdf

1879-MUM-2007-MARKED COPY(18-10-2012).pdf

1879-mum-2007-other document(15-5-2008).pdf

1879-MUM-2007-REPLY TO EXAMINATION REPORT(31-5-2010).pdf

1879-MUM-2007-REPLY TO HEARING(18-10-2012).pdf

1879-MUM-2007-SPCIFICATION(AMENDED)-(31-5-2010).pdf

1879-MUM-2007-SPECIFICATION(AMENDED)-(18-10-2012).pdf

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