Title of Invention

A DEVICE FOR PACKAGING AN OPTICAL FIBER AMPLIFIER

Abstract

A device for an optical amplifier is described. The device comprises a packaging box(10) including an optical fibre holder(14) and a plurality of retaining means (18, 20a, 24a, 26a). The optical fibre holder(14)is positioned around a central opening. The optical fibre holder includes a plurality of protuberances (16) for preventing detachment of the optical fibres.The retaining means hold and fix the optical elements of the optical amp1ifier.

Full Text

1A Field of the invention The present invention relates to a device for packing an optical fibre amplifier, and in particular to a packaging assembly for a double pumping erbium doped optical fibre amplifier (EDFA.) Background to the Invention Optical fibre amplifiers amplify optical signals, which are converted from an electrical signal. They are provided at a given distance along an optical fibre to compensate for transmission loss. One of the more widely used optical fibre amplifiers is the double pumping erbium doped optical fibre amplifier (EDFA), the structure of which is illustrated in Fig. 1. The construction and the operation of the double pumping erbium-doped optical fibre amplifier will now be described with reference to figure 1. An EDFA includes an input connector 100 which connects a lead-in optical fibre from outside to an inner optical fibre, inside of the optical fibre amplifier. A first optical tap 104 is connected via the optical fibre to the input connector 100. The first optical tap 104 splits the optical signal received through the optical fibre at a fixed rate and applies the split signals to a first photo diode 110 and to a first optical isolator 112. The first photo diode 110 monitors the magnitude of the received signal. The first optical isolator 112, which includes an input end and an output end, transmits a fixed wavelength region of the optical signal travelling from the input end to the output end. First optical isolator 112 also prevents a reverse optical signal returning to the input end. Thus, the optical isolator 112 blocks the backward flow of the ASE (amplified spontaneous emission) generated by the first erbium-doped optical fibre to its rear and prevents the optical input signal from being 2 distorted. The optical signal output from first optical isolator 112 is applied to a first wavelength-division multiplexer 120. A first pumping laser diode 126 is connected to the output end of the first wavelength-division multiplexer 120 and supplies a light source of stimulated wavelength to first erbium-doped optical fibre 116. The first wavelength-division multiplexer 120 receives the incident optical signal having a wavelength of 1550nm and the stimulated light source having a wavelength of 980nm or 1480nm in different input terminals and provides an output to an optical fibre terminal. The first pumping laser diode 126 is used in many power amplifiers. It is usually positioned just before the sending-end of the communication means because it increases the saturation output. Saturation output is increased by amplifying large-signals with the reverse directional ASE, the strength of which is greater than that of the forward directional ASE in optical fibre amplifiers. The output end of the above first wavelength-division multiplexer 120 is connected to a second optical isolator 128. The output end of the second optical isolator 128 is connected to a second wavelength-division multiplexer 136. The second optical isolator 128 performs the same function as the first optical isolator 112. The second wavelength-division multiplexer 136 supplies the light source with a stimulated wavelength pumped in the forward direction by a second pumping laser diode 134. It also supplies the incident optical signal to a second erbium-doped optical fibre 140. The second pumping laser diode 134 is used in many preamplifiers. It is typically positioned just before the receiving end of the communication means. It utilizes pumping light with a wavelength of 980nm in which the small-signal gain is relatively high and the noise is low. 3 The output-end of the second wavelength-division multiplexer 136 applies the stimulated light source having a wavelength of 980nm and the incident optical signal having a wavelength of 1550nm to the second erbium-doped optical fibre 140. The erbium-doped optical fibres 116, 140 amplify the incident optical signal because they are doped with the rare-earth erbium element (atomic No. 68) which has a high absorptivity in specific wavebands (800nm, 980nm, 1480nm, etc.) and a spectrum with a bandwidth divergence of about 60nm in a specific wave band (1550nm). The output-end of the second erbium-doped optical fibre 140 is connected to a third optical isolator 144. Third optical isolator 144 is connected to a second optical tap 148. The output-end of the second optical tap 148 is connected to the output optical fibre by means of an output connector 156. The third optical isolator 144 blocks a reverse optical signal reflected by/from the connecting parts of the second optical tap 148 or the output connector 156. The second optical tap 148 receives the optical signal from the third optical isolator 144 and splits it further into an optical signal for transmission to the output optical fibre via the output connector 156 and a monitoring optical signal for monitoring the optical output signal. The monitoring optical signal is monitored by the second photodiode 152. After the optical elements of the optical fibre amplifier (i.e. the input connector, optical taps, photodiodes, optical isolators, wavelength-division multiplexers, pumping laser diodes, and output connector) are connected with the respective input optical fibre and output optical fibre provided on both sides of the amplifier, the contact points, i.e., splicing points, are wrapped with thermocontractile tubes 102, 106, 108, 114, 118, 122, 124, 130, 132, 138, 142, 146, 154, 150. Alternatively, the contact points are coated with aluminum or stainless material. 4 The number of optical elements in the double pumping erbium-doped optical fibre amplifier packed is 25, including the thermocontractile tubes. In the conventional packaging method, the optical section and the electrical circuitry are installed in a packaging box the inside of which is formed like elliptical racetrack. Installation is such that the optical isolators, wavelength division multiplexers, optical taps, and the thermocontractile tubes are each arranged around the track without any fixing means. After insulation in the racetrack, a sponge rubber plate is placed above the optical elements and thermocontractile tubes to fix them in the box by pressing down on them. The conventional packaging of the optical fibre amplifier suffers from a disadvantage since the optical elements and thermocontractile tubes are not fixed in the packaging box. Thus, packed optical elements will shake and vibrate within the box when the box is moved or turned around. As a result, the optical fibres, each of which is connected to the optical elements are depressed and bent. This in turn results in deterioration of the properties of the optical elements and the entire optical fibre amplifier itself. A further disadvantage results from the arrangement of the track inside of the packaging box. The track leans downwardly from the centre. This arrangement means that the packaging box does not have enough space to accommodate the wavelength-division multiplexers, optical taps, optical isolators, and thermocontractile tubes of an optical amplifier with a double pumping structure. Moreover, the arrangement of the optical elements around the track is such that, the optical fibres are bent by each of the optical elements, which results in bending losses. Furthermore the part replacement and general improvements of the optical amplifier are made more difficult because the parts are not fixed in with the box. Productivity is also decreased because the optical elements can not be installed quickly in the assembly process. 5 It is, therefore, an objective of the present invention to provide a device for fixing the elements of an optical fibre amplifier in predetermined positions inside a packaging box and which prevents the optical elements and optical fibre from being damaged during movement and vibration. Summary, of the Invention Accordingly, the present invention provides a packaging assembly for an optical fibre amplifier including electronic circuitry and an erbium doped optical fibre, at least one pumping diode and a plurality of optical elements connected to one another by spliced optical fibres, the packaging assembly comprising: a housing including a central region for accommodating the electronic circuitry and the pumping diode or diodes; an optical fibre holder which circumscribes the central region of the housing, for retaining the erbium doped optical fibre around the central region; means for retaining the optical elements of the optical fibre amplifier and the splicing points of the optical fibres. Preferably, the central region comprises a central opening in the housing. The optical fibre holder may include a plurality of fixing protuberances for preventing detachment of the erbium doped optical fibre from the holder. The optical fibre holder may comprise an elliptical track and the optical fibres are wound around the track. A plurality of retaining means are formed on opposite sides of the optical fibre holder for retaining the optical elements of the optical fibre amplifier. Two retaining means may be formed on each side of the optical fibre holder, comprising grooves of a predetermined curvature. The grooves may be formed substantially parallel to each other. A plurality of protrusions may be formed along the upper 6 edges of the housing to prevent the upward movement of the optical fibres. The housing may further include curved guide walls at each of its corners, for guiding the optical fibres around the walls of the housing. Where the splicing points of the optical fibres are protected by thermocontractile tubes, the packaging assembly preferably comprises protecting means, positioned at opposite ends of the optical fibre holder, for holding the thermocontractile tubes. The thermocontractile tube holders may comprise two levels, each level including a plurality of recesses for holding thermocontractile tubes, and may include rounded edges for guiding the optical fibres around the walls of the housing. The thermocontractile tube holders may further include a plurality of resilient protrusions for resiliently holding the thermocontractile tubes. The thermocontractile tube holders may be fitted onto guide bosses to prevent their detachment from the housing. Where thermocontractile tubes are not present, the packaging assembly may include a plurality of ribs arranged around the optical fibre holder for holding and retaining the splicing points of the optical fibres. The ribs may be positioned around the optical fibre holder diagonally opposite to each other. The ribs may be substantially L-shaped. The packaging assembly may further include fixing bosses at each corner of the housing, or fastening holes at each corner of the housing for fastening a cover onto the housing. Brief Description of the accompanying Drawings The present invention will now be described by way of example with reference to the accompanying drawings in which: 7 Fig. 1 is a block diagram of the structure of a conventional double pumping erbium doped optical fibre amplifier (EDFA); Fig. 2 is a perspective view of the structure of a packaging assembly to fix the optical elements according to an embodiment of the present invention; Fig. 3 is a perspective view of the protector for holding the thermocontractile tubes which protect the splicing points of the optical fibres, in the packaging box as shown in Fig. 2; Fig. 4 is a plan view of Fig. 1; Fig. 5 illustrates the layout of the optical elements in the packaging box as shown in Fig. 1; Fig. 6 is a perspective view illustrating the structure of a packaging assembly according to another embodiment of the present invention; Fig 7 is a perspective view illustrating the protector for holding the thermocontractile tubes in Fig. 6; Fig. 8 is a plan view of Fig. 6; and Fig. 9 illustrates the layout of the optical elements in the packaging assembly of Fig. 6. Detailed Description of the Preferred Embodiment As shown in Figs. 2 and 4, the packaging box 10, of the present invention comprises a central opening 12. The central opening 12 is provided to accommodate the pumping laser diodes 126, 134 connected with the optical section of the amplifier and the electronic circuitry of the amplifier, as well as the monitoring connectors of the optical taps 104, 148. An optical fibre holder 14 is provided along/around the central opening 12 for holding the erbium-doped optical fibres 116, 140 around central opening 12. The optical fibre holder 14 is formed like an elliptical track in order to minimize the bending losses of the erbium-doped optical fibres 116, 140 in the vicinity of curved surfaces when they are mounted. A plurality of fixing protuberances 16 are formed at regular intervals on the upper periphery of the optical fibre holder 14 to 8 support and fix the erbium-doped optical fibres 116, 140 in position. Fixing protuberances 16 thus prevent erbium doped optical fibres 116, 140 from being detached from the optical fibre holder 14. The upper side of the optical fibre holder 14 is provided with a second guide support 20a for holding and fixing second optical isolator 128. Second guide support 20a is formed like a groove and has a pre-determined curvature. First guide support 18 is also formed like a groove and has a pre-determined curvature. First guide support 18 is provided on one side of the second guide support 20a to hold and fix the first optical isolator 112. The lower side of the optical fibre holder 14 is provided with third guide support 24a, which is also formed like a groove and has a pre-determined curvature. Third guide support 24a holds and fixes first and second optical taps 104, 148, and first and second wavelength-division multiplexers 120, 136. A fourth guide support 26a is also formed like a groove and has a pre-determined curvature. Fourth guide support 26a is formed on one side of the third guide support 24a to hold and fix third optical isolator 144. A plurality of inverted L-shaped fixing ribs 22a, 22b, 22c, 22d are arranged around the optical fibre holder 14 diagonally opposite to each other. Fixing rings 22a, 22b, 22c,22d hold and fix input-end optical fibres and output-end optical fibres projected from each of the optical elements. Protectors 28 are provided in order to support and fix a plurality of thermocontractile tubes. The protectors 28 include plurality of fixing supports 30, which are formed like grooves. As shown in figure 3, the protectors 28 comprise two identical level or decks and the fixing supports are provided on each deck. Protectors 28 are provided on the left and right sides of the optical fibre holder 14 and are fastened onto the box 10 by means of screws 48. As shown in figure 5, the protector 28 provided on the left 9 side of the optical fibre holder 14 holds the thermocontractile tubes 138, 142, 146, on the first level and thermocontractile tubes 132, 150, 154 on the second level. Likewise, the protector 28 on the right side of the optical fibre holder 14 holds the thermocontractile tubes 114, 118, 122, 130 on the first level and holds the thermocontractile tubes 102, 106, 108, 124 on the second level. Alternatively, if input- and output-end optical fibres of the optical elements are simply spliced together and the splicing points are then coated with aluminum or stainless material, instead of using thermocontractile tubes, the above input- and output-end optical fibres of optical elements may be mounted and fixed on the above fixing ribs 22a, 22b, 22c, 22d. In such a case, the protectors 28 need not be provided to the left and right of the optical fibre holder 14. The four corners of the packaging box 10 are provided with cover fastening holes 52. Fastening holes 52 are provided so that a protection cover can be screwed down tight onto the packaging box 10. The protection cover protects the optical elements from the external environment after packaging. The underside of the packaging box 10 is provided with an optical fibre lead-in path 54 on one side and an optical fibre lead-out path 56 on an opposite side. The method for packaging the double pumping erbium-doped optical fibre amplifier in the packaging box of the present invention will now be described. A layout is prepared by arranging all the optical elements. The optical elements are arranged by dividing them into input-ends and output-ends and defining the specified disposition spaces of the optical elements as shown in Fig. 5. The optical elements (optical fibre, holder, protectors fixing ribs etc) are arranged and fixed on the fixing board within the above packaging box 10 according to the above 10 layout (Fig. 5), and the input-ends optical fibres and output-ends optical fibres are spliced together respectively. Next, the thermocontractile tubes 102, 106, 108, 114, 118, 122, 124, 130, 132, 138, 142, 146, 154, 150 which wrap each of the splicing points for protection are fixed in the protectors 28. This completes the packaging process of the optical fibre amplifier. A second embodiment of a packaging box 10 according to the present invention will now be described. The packaging box 10 includes a central opening 12. The central opening 12 accommodates the pumping laser diodes 126, 134 which are connected with the optical section, the electronic circuitry, and the monitoring connectors of the optical taps 104, 148. The packaging box 10 includes an optical fibre holder 14 formed around/along the central opening 12 for holding the erbium-doped optical fibres 116, 140. The optical fibre holder 14 is formed like an elliptical track in order to minimize the bending losses of the erbium-doped optical fibres 116, 140 in the vicinity of curved surfaces when they are mounted. Six fixing protuberances 16 are formed at regular intervals on the upper periphery of the optical fibre holder 14 to support and fix the erbium-doped optical fibres 116, 140 in position. Fixing protuberances 16 prevent upward detachment of optical fibres from the optical fibre holder 14. The upper side of the optical fibre holder 14 is provided with a second guide support 20b. Second guide support 20b is formed like a groove and has a predetermined curvature. Second guide support 20b holds and fixes third optical isolator 144. A second guide support 20a which is also formed like a groove and has a predetermined curvature, is provided on one side of the second guide support 20b. The second guide support 20a holds and fixes second optical isolator 128. A fixing support 40 is provided on one side of the second guide support 20a to hold and fix first and second optical taps 104, 148 and first and second wavelength-division multiplexers 120, 136. Fixing support 11 40 is also formed like a groove and has a pre-determined curvature. The fixing support 40 consists of first fixing support 40a, which holds the first and second optical taps 104, 148, and second fixing support 40b, which holds the first and second wavelength-division multiplexers 120, 136. First and second fixing supports 40a and 40b are formed so that each has its own separate curvature. This means that the optical fibres packaged in the first and second fixing supports can be different, depending on the packaging method. A third guide support 24b, which is also formed like a groove and has a pre-determined curvature holds the first optical isolator 112. Third guide support 24b is provided in the lower part of the optical fibre holder 14. A fourth guide support 26b holds the second optical isolator 128. Fourth guide support 26b is provided on one side of the third guide support 24b. Fourth guide support 26b is formed like a groove and has a pre-determined curvature. Protectors 28 are provided to support and fix a plurality of thermocontractile tubes. As shown in figure 7 protectors 28 include a plurality of fixing supports 30 which are formed like grooves. The protectors 28 comprise two identical levels or decks with fixing supports 30 provided on each deck etc. The protectors 28 are provided to the right and left of the optical fibre holder 14 and are fastened onto the packaging box 10 by means of screws 48. As shown in Fig. 9, the protector 28 to the left of the optical fibre holder 14 holds the thermocontractile tubes 138, 142, 146,on the first level and holds the thermocontractile tubes 132, 150, 154 on the second level. Similarly the protector 28 to the right of the optical fibre holder 14 holds the thermocontractile tubes 114, 118, 122, 130 on the first level, the thermocontractile tubes 102, 106, 108, 124 on the second level. The protectors 28 are fitted onto guide bosses 44 which are provided on the bottom of the packaging box 10. Guide bosses 44 are 12 provided to fix the protectors 28 firmly in the box 10, protect them from external impact, and prevent them from being detached. In order to maintain the curvature of the optical fibres at a specified angle to the packaging path, guide roundings 32 are formed round on the outer periphery of the protectors 28. Resilient protuberances 34 are also formed at regular intervals on the top of the fixing supports 30 in order to resi1iently hold the thermocontractile tubes. In order to prevent the upward detachment of the optical fibres from when they are wound with a given curvature in the packaging box, four barring protuberances 42 are formed inwardly from the upper and lower edges of the packaging box 10. In order to guide the optical fibres along/around the inner wall of the packaging box without damaging the optical fibres, curved guide walls 58 are formed inside of each corners. Four fixing bosses 50 are also provided in the four corners of the packaging box 10 so that the packaging box 10 may be mounted and fixed on the main housing (not shown). To protect the optical elements from the external environment after packaging, cover fastening holes 52 are formed on the outermost corners so that a cover (not shown) may be screwed down tight onto the packaging box 10. The underside of the packaging box 10 is also provided with an optical fibre lead-in path 54 on one side and an optical fibre lead-out path 56 on an opposite side. The method of packaging the double pumping erbium-doped optical fibre amplifier in a packaging box according to the second embodiment will now be described. A layout is prepared with optical elements arranged in the packaging box 10 as illustrated in Fig. 9. The optical elements (optical fibre holder, fixing supports, guide supports etc.) are spliced according to the arrangement as shown in Fig. 9 and then arranged and fixed on the fixing board of the packaging box 10 layout. Next the thermocontractile tubes which wrap each of the splicing points for protection 13 are fixed in the protectors 28. This step completes the packaging process of the optical fibre amplifier. As described above, a packaging assembly according to the present invention in a packaging box has several advantages. Optical elements can be efficiently packaged during the production process. The optical section of the optical fibre amplifier can be miniaturized. Thus, the packaging process can be performed at high speed. Moreover the optical elements are stably fixed in the packaging box which protects the optical elements and optical fibres against external vibrations and impacts. Furthermore, the positions of optical elements on the input- and output-ends within the packaging box can be standardized. This facilitates parts replacement during repair -14-WE CLAIM: 1. A device for packaging an optical fibre amplifier having electronic circuitry and an erbium doped optical fibre, at least one pumping diode and a plurality of optical elements connected to one another by spliced optical fibres, said device comprising: a packaging box (10) with an opening (12) for accomodating the electronic circuitry and the pumping diode or diodes; an optical fibre holder (14) which circumscribes the central region of the housing for retaining the erbium doped optical fibre around the central region; means (18, 20a, 24a, 26a, 28) for retaining the optical elements of the optical fibre amplifier and the splicing points of the optical fibres. 2. The device as claimed in claim 1 wherein the opening (12) comprises a central opening in the packaging box (10). 3. The device as claimed in claim 1 or 2 wherein the optical fibre holder (14) comprises a plurality of fixing protuberances (16) for preventing detachment of the erbium doped optical fibre from the holder. 4. The device as claimed in any preceding claim wherein a plurality of retaining means ( 18, 20a, 24a, 26a) are formed on opposite sides of the optical fibre holder for retaining the optical elements of the optical fibre amplifier. -15- 5. The device as claimed in claim 4 3 wherein two retaining me arts (18, 20a; 24a, 26a) are formed an each side of the optica1 fibre holder. 6. The device as claimed in claim 5 wherein the retaining means comprise grooves of a predetermined curvature. 7. The device as claimed in claim 6 wherein the grooves are formed substantially parallel to each other. 8. The device as- claimed in any preceding claim wherein a plurality of barring protuberances (42) are formed along the upper edges of the housing to prevent the upward movement of the optical fibres. 9. The device as claimed in any preceding claim wherein the housing comprises curved guide walls (58) at each of its corners, for guiding the optical fibres around the walls of the housing. 10. The device as claimed in any preceding claim wherein the splicing points of the optical fibres are protected by thermocontractile tubes and comprising protectors (28),positioned at opposite ends of the optical fibre holder, for holding the thermocontractile tubes. 11. The device as claimed in claim 10 wherein the thermocontractile tube holders comprises two levels, each level comprising a plurality of fixing supports (30) for holding thermocontractile tubes. -16- 12. The device as claimed in claim 10 or claim 11 wherein the thermocontractile tube holders comprise guide roundings (32) for guiding the optical fibres around the walls of the housing. 13. The device as claimed in any one of claims 10-12 wherein the thermocontractile tube holders comprises a plurality of resilient protuberances (34) for resiliently holding the thermo- contractile tubes. 14. The device as claimed in any one of claims 10-13 wherein the thermocontractile tube holders are fitted onto guide bosses (44) to prevent their detachment from the housing. 15. The device as claimed in any one of claims 1-9 comprising a plurality of ribs (22a, 22b, 22c, 22d) arranged around the optical fibre holder for holding and retaining the splicing points of the optical fibres. 16. The device as claimed in claim 15 wherein the ribs (22a, 22b, 22c, 22d) are positioned around the optical fibre holder diagonally opposite to each other. 17. The device as claimed in claim 15 or 16 wherein the ribs ( 22a, 22b, 22c, 22d) are substantially L-shaped. 18. The device as claimed in any preceding claim comprising fixing bosses (50) at each comer of the housing. -17- 19. The device as claimed in any preceding claim comprising fastening holes (52) at each corner of the housing for fastening a cover onto the housing. A device for an optical amplifier is described. The device comprises a packaging boss (10) including an optical fibre holder (14) and a plurality of retaining means (18, 20a, 24a, 26a). The optical fibre holder (14) is positioned around a central opening. The optical fibre holder includes a plurality of protuberances (16) for preventing detachment of the optical fibres. The retaining means hold and fix the optical elements of the optical amp1ifier.

Documents:

02008-cal-1997 abstract.pdf

02008-cal-1997 claims.pdf

02008-cal-1997 correspondence.pdf

02008-cal-1997 description(complete).pdf

02008-cal-1997 drawings.pdf

02008-cal-1997 form-1.pdf

02008-cal-1997 form-2.pdf

02008-cal-1997 form-3.pdf

02008-cal-1997 form-5.pdf

02008-cal-1997 pa.pdf

2008-cal-1997-granted-abstract.pdf

2008-cal-1997-granted-acceptance publication.pdf

2008-cal-1997-granted-claims.pdf

2008-cal-1997-granted-correspondence.pdf

2008-cal-1997-granted-description (complete).pdf

2008-cal-1997-granted-drawings.pdf

2008-cal-1997-granted-form 1.pdf

2008-cal-1997-granted-form 2.pdf

2008-cal-1997-granted-form 3.pdf

2008-cal-1997-granted-form 5.pdf

2008-cal-1997-granted-gpa.pdf

2008-cal-1997-granted-letter patent.pdf

2008-cal-1997-granted-priority document.pdf

2008-cal-1997-granted-reply to examination report.pdf

2008-cal-1997-granted-specification.pdf

2008-cal-1997-granted-translated copy of priority document.pdf