Indian Patents. 261064:EXTRACTION OF ONE BEAM FROM A MIXTURE OF TWO COAXIALLY CO-PROPAGATING MUTUALLY INCOHERENT BEAMS OF SAME FREQUENCY, EXTRACTION OF DATA BITS LOADED ON ONE COHERENT BEAM MIXED WITH THE DATA BITS LOADED ON ANOTHER COHERENT BEAM OF SAME FREQUENCY AND COHERENCE DIVISION MULTIPLEXING (CDM)

Title of Invention	EXTRACTION OF ONE BEAM FROM A MIXTURE OF TWO COAXIALLY CO-PROPAGATING MUTUALLY INCOHERENT BEAMS OF SAME FREQUENCY, EXTRACTION OF DATA BITS LOADED ON ONE COHERENT BEAM MIXED WITH THE DATA BITS LOADED ON ANOTHER COHERENT BEAM OF SAME FREQUENCY AND COHERENCE DIVISION MULTIPLEXING (CDM)
Abstract	The invention relates to a method for extracting one beam form the mixture of two mutually incoherent co-propagating beams of same frequency, same state of polarization and mode but unequal intensity in a Mach-Zehnder interferometer (MZI) configured with predetermined parameters.

Full Text	FIELD OF INVENTION The invention relates to a method of extracting one beam form the mixture of mutually incoherent co-propagating beams of same frequency and same polarization state in a single mode waveguide. The invention further relates to extracting Data Bits loaded on one coherent beam mixed with the Data Bits loaded on another coherent beam (where both beams are mutually incoherent with respect to each other) of same frequency, same polarization state and . mode adapting a Mach-Zehnder Interferometer (MZI). The present invention also relates to Coherence Division Multiplexing (CDM) and All-Optical Signal Processing. BACKGROUND OF INVENTION Extraction of one beam from a mixture of two or more coaxially co-propagating mutually incoherent beams in a single mode waveguide, when all the beams being of the same frequency and same state of polarization, is considered impossible in optics. Mixture of mutually incoherent beams means two or more coaxially co-propagating beams obtained from different coherent (e.g. laser) sources. Moreover, extraction of one Data from the mixture of two Data is considered impossible when one is loaded on one coherent beam and the other is loaded on another coherent beam of same frequency, same polarization state and mode (where both beams are mutually incoherent with respect to each other). Such a method of extraction may find applications in signal processing, particularly in Coherence Division Multiplexing De-multiplexing (CDM), signal coding-decoding , OBJECTS OF INVENTION It is therefore, an object of the present invention to propose a method of extracting one beam form the mixture of two mutually incoherent co-propagating beams of same frequency, same state of polarization and mode in a single mode waveguide using a Mach-Zehnder Interferometer (MZI) or using a Photonic Crystal (PC) waveguides based Mach-Zehnder interferometer. Another object of the present invention is to propose a method of extracting Data Bits loaded on one coherent beam mixed with the Data Bits loaded on an another coherent beam (where both beams are mutually incoherent with respect to each other) of same frequency, same state of polarization and mode using a Mach-Zehnder Interferometer (MZI) or using a Photonic Crystal (PC) waveguides based Mach-Zehnder interferometer. A still another object of the present invention is to propose a method of signal processing, particularly a method of Coherence Division Multiplexing De- multiplexing and signal coding-decoding. A further object of the present invention is to propose a method of data extraction from each channel in Coherence Division Multiplexing De-multiplexing having two channels created by two coherent but mutually incoherent carrier waves of same frequency, same state of polarization, same mode and different intensities. SUMMARY OF INVENTION Thus, in a first aspect of the present invention, there is proposed a method of extracting one beam from the mixture of two or more coaxially co-propagating mutually incoherent beams of same frequency, same state of polarization in a single mode wave guide. In a second aspect, the invention proposes a method of extracting Data Bits loaded on one coherent beam mixed with the Data Bits loaded on another coherent beam (where both beams are mutually incoherent with respect to each other) of same frequency, same state of polarization in a single mode waveguide using a Mach-Zehnder Interferometer (MZI). In a third aspect, there is provided a MZI with a first arm made up of a nonlinear material and a second arm with linear material, which can be adapted in the extraction methods of the invention.. When an optical beam is launched at the input port (Pj) of a MZI, the beam is equally splitted and propagates through each arm of the interferometer and recombines at the output port (Po) of the interferometer (MZI). If the splitted parts of the beam recombine with "in-phase" condition, whole of the input beam reaches at the output port and if splitted parts of the beam recombine with "out- of-phase" condition, the input beam doesn't reach at Po, thus giving zero output. One can set the parameters of the MZI such that when the mixture of two coherent but mutually incoherent beams of same frequency but unequal intensities are launched at (Pj) of the MZI, the splitted parts of a first beam recombine with the "in-phase" condition, while, the splitted parts of the second beam recombine with "out-of-phase" condition thus allowing only one beam to pass through. Such extraction is also possible for a mixture of more than two beams. One can also set the parameters of the MZI in such a fashion that the MZI always allows a first beam to pass through and blocks a second beam when either of the beams or the mixture of both is launched at Pi thereby extracting Data bits loaded on the first beam, The above mentioned extraction can also be achieved by using 3 dB directional couplers in place of Y-combiner/splitter of the MZI. In this case, when two mutually incoherent beams (or two data bits loaded on two mutually incoherent beams) are launched at the same input port, they come out at two different ports of the output directional coupler of the MZI. If those are launched at the different input port, they come out at the same port of the output directional coupler of the MZI accomplishing multiplexing and demultiplexing function. Mentioned extractions are also possible using a Photonic Crystal (PC) waveguides based Mach-Zehnder interferometer. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The nature of the invention, its objective and further advantages residing in the same will be apparent from the following description made with reference to non-limiting exemplary embodiments of the invention represented in the accompanying drawings: - Figure 1 - shows a Mach-Zehnder Interferometer with a first arm made of a non-linear material and a second arm of linear material according to the invention. Figure 2 - Shows that the Mach-Zehnder Interferometer with parameters set according to the invention, which (a) allows only one beam from the mixture of two beams to pass through, and (b) blocks the other beam from passing through from the mixture of beams. Figure 3 - shows that the MZI with parameters set according to the invention; always allows one beam and blocks other beam when either of the beams or mixture of both is launched at Pi, thereby (a) extracting Data Bits loaded on the one beam, and. (b) MZI parameters can further be adjusted according to the invention to extract Data Bit loaded on the other beam. Figure 4- The mentioned extraction can also be achieved by using 3 dB directional couplers in place of Y-combiner/splitter of the MZI. (a) If two mutually incoherent beams or two data bits loaded on two mutually incoherent beams are launched at the same input port, they come out at two different ports of the output directional coupler of the MZI. (b) If those are launched at the different input port, they come out at the same port of the output directional coupler of the MZI accomplishing multiplexing and demultiplexing function. Figure 5- Shows the Mach-Zehnder Interferometer with 3 dB directional couplers at the input/output ports and parameters set according to the invention. When (a) The first beam alone launched at P1, it comes out at P3. (b) the second beam alone launched at P1, it comes out at P4. (c) both first and the second beams simultaneously launched at P1, first comes out at P3 and second comes out at P4. DETAIL DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION The schematic diagram of the Mach-Zehnder Interferometer (MZI) according to the invention is shown in figure 1. The Mach-Zehnder Interferometer (MZI) comprises a first arm (NLA) made up of a nonlinear material and a second arm (LA) of linear material. When an Input intensity is launched at the input port (P1), it equally splits and propagates through each arm (NLA, LA) of the interferometer (MZI) and recombines at the output port (Po) of the interferometer (MZI). If the splitted parts of the beam recombine with "in-phase" condition, whole of the input beam reaches at the output port (Po) and if the splitted parts of the beam recombine with "out-of-phase" condition, the input beam doesn't reach at the input port( Po )giving a zero output. Extraction of one beam from a mixture of two coaxially co-propagatinq mutually incoherent beams of same frequency; The concept on which the present invention is developed, is the nonlinearity induced refractive index change (Δnj) seen by two co-propagating beams in the nonlinear arm (NLA) of the interferometer (MZI). The refractive index change (Δnj) seen by the two coaxially co-propagating mutually incoherent beams of intensities (\|E1\|2 and \|E2\|2) , can be generally represented by the following relationship:- where, n2 is the nonlinear coefficient of the material of the nonlinear arm (NLA), K is the coupling or interaction coefficient of the two beams, which is, normally, not equal to 1 (for two beams of same polarization, K =2) and therefore, if the two beams are of unequal intensities, they see different refractive indices of the nonlinear arm (NLA) of the interferometer (MZI) and therefore, they see different optical path lengths after propagating through same length in the NLA. For a given n2 and selected beam intensities (essentially unequal), one can select the length of the interferometer (MZI) so that the difference in the optical path lengths of the two beams in the nonlinear arm (NLA) is 111. The splitted parts of the input beams propagating through the linear arm (LA) will always see same optical path length. In this situation, if the selected length of the interferometer (MZI) is also providing "in-phase" condition to the recombining splitted parts (propagating through the linear arm (LA) and the nonlinear arm (NLA) of any one of the two beams), the splitted parts of the other beam will recombine with "Out-of-phase" condition. Therefore, only the first beam will be allowed (see figure 2a) and appear at the output of the interferometer (MZI) and the second beam will be blocked (see figure 2b). It is also possible to extract one beam from the mixture of more than two coaxially co-propagating mutually incoherent beams by appropriately setting the parameters of the interferometer (MZI). Extraction of Data Bits loaded on one coherent beam mixed with the Data Bits loaded on another coherent beam of same frequency; An optical beam carries information in the form of bit streams. It is possible to select the input bit intensity \|Et\| of a first beam, bit intensity \E2\2 of a second beam, and associated parameters of an interferometer (MZI) such that when \|E,\|2 is provided at the output port (P1), it appears at the input port (Po), when \E2\|2 is provided at the output port (Pi), it doesn't appears at the input port (Po) and when both (\|E1\|2 and \|E2\|2) are provided at the output port (Pi), only \|E1\|2 appears at the input port (Po). In other words, the (MZI) only allows Data bits loaded on the first beam and blocks Data bits loaded on the second beam thereby extracting information loaded on the first beam as shown in figure 3a. One can also set parameters of the interferometer (MZI) to extract Data Bits loaded on the second beam and block Data Bits loaded on the first beam as shown in figure 3b. The above mentioned extraction can also be achieved by using 3 dB directional couplers in place of Y-combiner/splitter of the MZI as shown in the figure 4. In this case, two mutually incoherent beams or two data bits loaded on two mutually incoherent beams are launched at the same input port, (each of them alone or both of them simultaneously) first beam always appears at one of the two output ports of the MZI and second beam appears at the other output port of the MZI accomplishing de-multiplexing. In figure 5, each case is shown separately for the Mach-Zehnder Interferometer with 3 dB directional couplers at the input/output ports and parameters set according to the invention. When (a) beam 1 alone launched at P1, it comes out at P3. (b) beam 2 alone launched at P1, it comes out at P4. (c) both beam 1 and beam 2 simultaneously launched at P1, beam 1 comes out at P3 and beam 2 comes out at P4. If the beams are launched at the two different input ports, they come out at the same port of the output directional coupler of the MZI accomplishing multiplexing. Mentioned extractions are also possible using a Photonic Crystal (PC) waveguides based Mach-Zehnder interferometer. Coherence division multiplexing (CDM); The invention further provides a novel Coherence Division Multiplexing and De- multiplexing in which two channels are created by two coherent but mutually incoherent carrier waves of same frequency and different intensities. Thus, information loaded on either of them can be extracted as explained hereinabove. Hence, the data carrying capacity of existing Wavelength Division Multiplexing (WDM) systems can be doubled, as each WDM channel can have two CDM channels. Signal Coding De-coding: Accordingly, confidential data loaded on one beam can be mixed with a pseudo data loaded on other mutually incoherent beam for coding or hiding purpose. The confidential data can only be extracted by a properly set interferometer (MZI). We Claim 1. A method for extracting one beam form the mixture of two mutually incoherent co-propagating beams of same frequency, same state of polarization and mode but unequal intensity in a Mach-Zehnder interferometer (MZI) configured with predetermined parameters. 2. A method as claimed in claim 1 wherein the parameters of the interferometer (MZI) are set to have one beam extracted form the mixture of more than two mutually incoherent co-propagating beams of same frequency, same state of polarization and mode. 3. A method for extracting data bits loaded on one coherent beam mixed with the data bits loaded on another coherent beam, both the beams being mutually incoherent with respect to each other of same frequency, same state of polarization and mode adapting a Mach-Zehnder Interferometer (MZI), the interferometer being set with selected parameters. 4. A method of Coherence Division Multiplexing De-multiplexing in all-optical signal processing, wherein two channels are created by two coherent but mutually incoherent carrier waves of same frequency, same state of polarization, mode and different intensities, and wherein data loaded on either of the carrier waves being extracted by carrying-out the method as claimed in claim 1 or 3, thereby doubling the data carrying capacity of existing Wavelength Division Multiplexing (WDM) systems by enabling each WDM channel to have two CDM channels. 5. The method as claimed in claim 1, wherein a nonlinearity induced refractive index change (Δnj) is created in a nonlinear arm (NLA) of the interferometer (MZI) by the two coaxially copropagating mutually incoherent beams of intensities (\|E1\|2 and \|E2\|2) maintaining a feature- relationship of: where: n2 is the nonlinear coefficient of a material of the nonlinear arm (NLA); : k is the coupling or interaction coefficient of two beams. 6. The method as claimed in claim 1 or 5, wherein the length of the interferometer (MZI) for a given nonlinear coefficient of the nonlinear arm (NLA) including an unequal beam intensities, is selectable so as to achieve a difference of λ / 2 optical path length for the two beams propagating in the nonlinear arm (NLA). 7. The method as claimed in claim 6, wherein the splitted parts of the input beams propagating through a linear arm (LA) of the interferometer (MZI) travel an identical optical path length. 8. The method as claimed in claim 1, 6 or 7, wherein the selected length of the interferometer(MZI) when provides an "in-phase" condition to the recombining splitted parts propagating through the linear and the nonlinear arms (LA,NLA) of a first of the two beams, the splitted parts of the second beam recombining with "out-of-phase" condition. 9. The method as claimed in claim 1, 5 to 8, wherein only the first beam is allowed to pass through so as to appear in the output of the interferometer (MZI), and wherein the second beam is blocked, thereby enabling extraction of the first beam from the mixture of two coaxially co-propagating mutually incoherent beams of same frequency. 10. The method as claimed in claim 3, wherein the bit-intensity of the first beam and the second beam (\|E1\|2 and \|E2\|2) including the associated parameters of the interferometer (MZI) are so selected that the bit intensity of the first beam (\|E1[2) when inputted at an input port (Pi) of the interferometer (MZI), the bit intensity appears at an output port (P0) of the interferometer (MZI), wherein when the bit intensity of the second beam (\|E2\|2) is inputted in the input port (Pi), it does not appear in the output port (Po), and wherein when the bit intensity of the first end second beams (\|E1\|2 and \|E2\|2) are inputted in the input port (Pi), only the bit stream of the first beam \|E1\|2) appears in the output port (Po) thereby extracting data bits loaded on the first beam 11. The method as claimed in claim 3 or 10, wherein the interferometer (MZI) can be set with corresponding parameters so as to enable extracting data bits loaded on the second beam and block data bits loaded on the first beam. 12. The method as claimed in above claims, wherein the interferometer (MZI) can incorporated with directional couplers at the input and output ports in place of Y-combiner/splitter. 13. The method as claimed in claim 1 to 11 claims, wherein the mentioned extractions are also possible using a Photonic Crystal (PC) waveguides based Mach-Zehnder interferometer. Abstract Title: EXTRACTION OF ONE BEAM FROM A MIXTURE OF TWO COAXIALLY CO- PROPAGATING MUTUALLY INCOHERENT BEAMS OF SAME FREQUENCY, EXTRACTION OF DATA BITS LOADED ON ONE COHERENT BEAM MIXED WITH THE DATA BITS LOADED ON ANOTHER COHERENT BEAM OF SAME FREQUENCY AND COHERENCE DIVISION MULTIPLEXING (CDM) The invention relates to a method for extracting one beam form the mixture of two mutually incoherent co-propagating beams of same frequency, same state of polarization and mode but unequal intensity in a Mach-Zehnder interferometer (MZI) configured with predetermined parameters.

Full Text

FIELD OF INVENTION
The invention relates to a method of extracting one beam form the mixture of
mutually incoherent co-propagating beams of same frequency and same
polarization state in a single mode waveguide. The invention further relates to
extracting Data Bits loaded on one coherent beam mixed with the Data Bits
loaded on another coherent beam (where both beams are mutually incoherent
with respect to each other) of same frequency, same polarization state and
. mode adapting a Mach-Zehnder Interferometer (MZI). The present invention also
relates to Coherence Division Multiplexing (CDM) and All-Optical Signal
Processing.
BACKGROUND OF INVENTION
Extraction of one beam from a mixture of two or more coaxially co-propagating
mutually incoherent beams in a single mode waveguide, when all the beams
being of the same frequency and same state of polarization, is considered
impossible in optics. Mixture of mutually incoherent beams means two or more
coaxially co-propagating beams obtained from different coherent (e.g. laser)
sources.
Moreover, extraction of one Data from the mixture of two Data is considered
impossible when one is loaded on one coherent beam and the other is loaded on
another coherent beam of same frequency, same polarization state and mode
(where both beams are mutually incoherent with respect to each other). Such a
method of extraction may find applications in signal processing, particularly in
Coherence Division Multiplexing De-multiplexing (CDM), signal coding-decoding ,

OBJECTS OF INVENTION
It is therefore, an object of the present invention to propose a method of
extracting one beam form the mixture of two mutually incoherent co-propagating
beams of same frequency, same state of polarization and mode in a single mode
waveguide using a Mach-Zehnder Interferometer (MZI) or using a Photonic
Crystal (PC) waveguides based Mach-Zehnder interferometer.
Another object of the present invention is to propose a method of extracting
Data Bits loaded on one coherent beam mixed with the Data Bits loaded on an
another coherent beam (where both beams are mutually incoherent with respect
to each other) of same frequency, same state of polarization and mode using a
Mach-Zehnder Interferometer (MZI) or using a Photonic Crystal (PC) waveguides
based Mach-Zehnder interferometer.
A still another object of the present invention is to propose a method of signal
processing, particularly a method of Coherence Division Multiplexing De-
multiplexing and signal coding-decoding.
A further object of the present invention is to propose a method of data
extraction from each channel in Coherence Division Multiplexing De-multiplexing
having two channels created by two coherent but mutually incoherent carrier
waves of same frequency, same state of polarization, same mode and different
intensities.

SUMMARY OF INVENTION
Thus, in a first aspect of the present invention, there is proposed a method of
extracting one beam from the mixture of two or more coaxially co-propagating
mutually incoherent beams of same frequency, same state of polarization in a
single mode wave guide. In a second aspect, the invention proposes a method
of extracting Data Bits loaded on one coherent beam mixed with the Data Bits
loaded on another coherent beam (where both beams are mutually incoherent
with respect to each other) of same frequency, same state of polarization in a
single mode waveguide using a Mach-Zehnder Interferometer (MZI).
In a third aspect, there is provided a MZI with a first arm made up of a nonlinear
material and a second arm with linear material, which can be adapted in the
extraction methods of the invention..
When an optical beam is launched at the input port (Pj) of a MZI, the beam is
equally splitted and propagates through each arm of the interferometer and
recombines at the output port (Po) of the interferometer (MZI). If the splitted
parts of the beam recombine with "in-phase" condition, whole of the input beam
reaches at the output port and if splitted parts of the beam recombine with "out-
of-phase" condition, the input beam doesn't reach at Po, thus giving zero output.
One can set the parameters of the MZI such that when the mixture of two
coherent but mutually incoherent beams of same frequency but unequal
intensities are launched at (Pj) of the MZI, the splitted parts of a first beam
recombine with the "in-phase" condition, while, the splitted parts of the second
beam recombine with "out-of-phase" condition thus allowing only one beam to
pass through. Such extraction is also possible for a mixture of more than two
beams.

One can also set the parameters of the MZI in such a fashion that the MZI
always allows a first beam to pass through and blocks a second beam when
either of the beams or the mixture of both is launched at Pi thereby extracting
Data bits loaded on the first beam,
The above mentioned extraction can also be achieved by using 3 dB directional
couplers in place of Y-combiner/splitter of the MZI. In this case, when two
mutually incoherent beams (or two data bits loaded on two mutually incoherent
beams) are launched at the same input port, they come out at two different
ports of the output directional coupler of the MZI. If those are launched at the
different input port, they come out at the same port of the output directional
coupler of the MZI accomplishing multiplexing and demultiplexing function.
Mentioned extractions are also possible using a Photonic Crystal (PC) waveguides
based Mach-Zehnder interferometer.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The nature of the invention, its objective and further advantages residing in the
same will be apparent from the following description made with reference to
non-limiting exemplary embodiments of the invention represented in the
accompanying drawings: -
Figure 1 - shows a Mach-Zehnder Interferometer with a first arm made of a
non-linear material and a second arm of linear material according
to the invention.

Figure 2 - Shows that the Mach-Zehnder Interferometer with parameters set
according to the invention, which (a) allows only one beam from
the mixture of two beams to pass through, and (b) blocks the other
beam from passing through from the mixture of beams.
Figure 3 - shows that the MZI with parameters set according to the invention;
always allows one beam and blocks other beam when either of the
beams or mixture of both is launched at Pi, thereby (a) extracting
Data Bits loaded on the one beam, and. (b) MZI parameters can
further be adjusted according to the invention to extract Data Bit
loaded on the other beam.
Figure 4- The mentioned extraction can also be achieved by using 3 dB
directional couplers in place of Y-combiner/splitter of the MZI. (a) If
two mutually incoherent beams or two data bits loaded on two
mutually incoherent beams are launched at the same input port,
they come out at two different ports of the output directional
coupler of the MZI. (b) If those are launched at the different input
port, they come out at the same port of the output directional
coupler of the MZI accomplishing multiplexing and demultiplexing
function.
Figure 5- Shows the Mach-Zehnder Interferometer with 3 dB directional
couplers at the input/output ports and parameters set according to
the invention. When (a) The first beam alone launched at P1, it
comes out at P3. (b) the second beam alone launched at P1, it
comes out at P4. (c) both first and the second beams
simultaneously launched at P1, first comes out at P3 and second
comes out at P4.

DETAIL DESCRIPTION OF PREFERRED EMBODIMENTS OF
THE INVENTION
The schematic diagram of the Mach-Zehnder Interferometer (MZI) according to
the invention is shown in figure 1. The Mach-Zehnder Interferometer (MZI)
comprises a first arm (NLA) made up of a nonlinear material and a second arm
(LA) of linear material. When an Input intensity is launched at the input port (P1),
it equally splits and propagates through each arm (NLA, LA) of the
interferometer (MZI) and recombines at the output port (Po) of the
interferometer (MZI). If the splitted parts of the beam recombine with "in-phase"
condition, whole of the input beam reaches at the output port (Po) and if the
splitted parts of the beam recombine with "out-of-phase" condition, the input
beam doesn't reach at the input port( Po )giving a zero output.
Extraction of one beam from a mixture of two coaxially co-propagatinq
mutually incoherent beams of same frequency;
The concept on which the present invention is developed, is the nonlinearity
induced refractive index change (Δnj) seen by two co-propagating beams in the
nonlinear arm (NLA) of the interferometer (MZI). The refractive index change
(Δnj) seen by the two coaxially co-propagating mutually incoherent beams of
intensities (|E1|2 and |E2|2) , can be generally represented by the following
relationship:-

where, n2 is the nonlinear coefficient of the material of the nonlinear arm (NLA),
K is the coupling or interaction coefficient of the two beams, which is, normally,
not equal to 1 (for two beams of same polarization, K =2) and therefore, if the
two beams are of unequal intensities, they see different refractive indices of the
nonlinear arm (NLA) of the interferometer (MZI) and therefore, they see
different optical path lengths after propagating through same length in the NLA.
For a given n2 and selected beam intensities (essentially unequal), one can
select the length of the interferometer (MZI) so that the difference in the optical
path lengths of the two beams in the nonlinear arm (NLA) is 111. The splitted
parts of the input beams propagating through the linear arm (LA) will always see
same optical path length. In this situation, if the selected length of the
interferometer (MZI) is also
providing "in-phase" condition to the recombining splitted parts (propagating
through the linear arm (LA) and the nonlinear arm (NLA) of any one of the two
beams), the splitted parts of the other beam will recombine with "Out-of-phase"
condition. Therefore, only the first beam will be allowed (see figure 2a) and
appear at the output of the interferometer (MZI) and the second beam will be
blocked (see figure 2b).
It is also possible to extract one beam from the mixture of more than two
coaxially co-propagating mutually incoherent beams by appropriately setting the
parameters of the interferometer (MZI).

Extraction of Data Bits loaded on one coherent beam mixed with the
Data Bits loaded on another coherent beam of same frequency;
An optical beam carries information in the form of bit streams. It is possible to
select the input bit intensity |Et| of a first beam, bit intensity \E2\2 of a second
beam, and associated parameters of an interferometer (MZI) such that when
|E,|2 is provided at the output port (P1), it appears at the input port (Po), when
\E2|2 is provided at the output port (Pi), it doesn't appears at the input port (Po)
and when both (|E1|2 and |E2|2) are provided at the output port (Pi), only |E1|2
appears at the input port (Po).
In other words, the (MZI) only allows Data bits loaded on the first beam and
blocks Data bits loaded on the second beam thereby extracting information
loaded on the first beam as shown in figure 3a. One can also set parameters of
the interferometer (MZI) to extract Data Bits loaded on the second beam and
block Data Bits loaded on the first beam as shown in figure 3b.
The above mentioned extraction can also be achieved by using 3 dB directional
couplers in place of Y-combiner/splitter of the MZI as shown in the figure 4. In
this case, two mutually incoherent beams or two data bits loaded on two
mutually incoherent beams are launched at the same input port, (each of them
alone or both of them simultaneously) first beam always appears at one of the
two output ports of the MZI and second beam appears at the other output port
of the MZI accomplishing de-multiplexing.

In figure 5, each case is shown separately for the Mach-Zehnder Interferometer
with 3 dB directional couplers at the input/output ports and parameters set
according to the invention. When (a) beam 1 alone launched at P1, it comes out
at P3. (b) beam 2 alone launched at P1, it comes out at P4. (c) both beam 1 and
beam 2 simultaneously launched at P1, beam 1 comes out at P3 and beam 2
comes out at P4.
If the beams are launched at the two different input ports, they come out at the
same port of the output directional coupler of the MZI accomplishing
multiplexing.
Mentioned extractions are also possible using a Photonic Crystal (PC) waveguides
based Mach-Zehnder interferometer.
Coherence division multiplexing (CDM);
The invention further provides a novel Coherence Division Multiplexing and De-
multiplexing in which two channels are created by two coherent but mutually
incoherent carrier waves of same frequency and different intensities. Thus,
information loaded on either of them can be extracted as explained hereinabove.
Hence, the data carrying capacity of existing Wavelength Division Multiplexing
(WDM) systems can be doubled, as each WDM channel can have two CDM
channels.
Signal Coding De-coding:
Accordingly, confidential data loaded on one beam can be mixed with a pseudo
data loaded on other mutually incoherent beam for coding or hiding purpose.
The confidential data can only be extracted by a properly set interferometer
(MZI).

We Claim
1. A method for extracting one beam form the mixture of two mutually
incoherent co-propagating beams of same frequency, same state of
polarization and mode but unequal intensity in a Mach-Zehnder
interferometer (MZI) configured with predetermined parameters.
2. A method as claimed in claim 1 wherein the parameters of the
interferometer (MZI) are set to have one beam extracted form the mixture
of more than two mutually incoherent co-propagating beams of same
frequency, same state of polarization and mode.
3. A method for extracting data bits loaded on one coherent beam mixed
with the data bits loaded on another coherent beam, both the beams
being mutually incoherent with respect to each other of same frequency,
same state of polarization and mode adapting a Mach-Zehnder
Interferometer (MZI), the interferometer being set with selected
parameters.
4. A method of Coherence Division Multiplexing De-multiplexing in all-optical
signal processing, wherein two channels are created by two coherent but
mutually incoherent carrier waves of same frequency, same state of
polarization, mode and different intensities, and wherein data loaded on
either of the carrier waves being extracted by carrying-out the method as
claimed in claim 1 or 3, thereby doubling the data carrying capacity of
existing Wavelength Division Multiplexing (WDM) systems by enabling
each WDM channel to have two CDM channels.

5. The method as claimed in claim 1, wherein a nonlinearity induced
refractive index change (Δnj) is created in a nonlinear arm (NLA) of the
interferometer (MZI) by the two coaxially copropagating mutually
incoherent beams of intensities (|E1|2 and |E2|2) maintaining a feature-
relationship of:

where: n2 is the nonlinear coefficient of a material of the nonlinear arm
(NLA);
: k is the coupling or interaction coefficient of two beams.
6. The method as claimed in claim 1 or 5, wherein the length of the
interferometer (MZI) for a given nonlinear coefficient of the nonlinear arm
(NLA) including an unequal beam intensities, is selectable so as to achieve a
difference of λ / 2 optical path length for the two beams propagating in the
nonlinear arm (NLA).
7. The method as claimed in claim 6, wherein the splitted parts of the input
beams propagating through a linear arm (LA) of the interferometer (MZI)
travel an identical optical path length.
8. The method as claimed in claim 1, 6 or 7, wherein the selected length of the
interferometer(MZI) when provides an "in-phase" condition to the recombining
splitted parts propagating through the linear and the nonlinear arms (LA,NLA) of
a first of the two beams, the splitted parts of the second beam recombining with
"out-of-phase" condition.

9. The method as claimed in claim 1, 5 to 8, wherein only the first beam is
allowed to pass through so as to appear in the output of the interferometer
(MZI), and wherein the second beam is blocked, thereby enabling extraction of
the first beam from the mixture of two coaxially co-propagating mutually
incoherent beams of same frequency.
10. The method as claimed in claim 3, wherein the bit-intensity of the first beam
and the second beam (|E1|2 and |E2|2) including the associated parameters of
the interferometer (MZI) are so selected that the bit intensity of the first beam
(|E1[2) when inputted at an input port (Pi) of the interferometer (MZI), the bit
intensity appears at an output port (P0) of the interferometer (MZI), wherein
when the bit intensity of the second beam (|E2|2) is inputted in the input port
(Pi), it does not appear in the output port (Po), and wherein when the bit
intensity of the first end second beams (|E1|2 and |E2|2) are inputted in the input
port (Pi), only the bit stream of the first beam |E1|2) appears in the output port
(Po) thereby extracting data bits loaded on the first beam
11. The method as claimed in claim 3 or 10, wherein the interferometer (MZI)
can be set with corresponding parameters so as to enable extracting data bits
loaded on the second beam and block data bits loaded on the first beam.

12. The method as claimed in above claims, wherein the interferometer (MZI)
can incorporated with directional couplers at the input and output ports in place
of Y-combiner/splitter.
13. The method as claimed in claim 1 to 11 claims, wherein the mentioned
extractions are also possible using a Photonic Crystal (PC) waveguides based
Mach-Zehnder interferometer.

Abstract

Title: EXTRACTION OF ONE BEAM FROM A MIXTURE OF TWO COAXIALLY CO-
PROPAGATING MUTUALLY INCOHERENT BEAMS OF SAME FREQUENCY,
EXTRACTION OF DATA BITS LOADED ON ONE COHERENT BEAM MIXED WITH
THE DATA BITS LOADED ON ANOTHER COHERENT BEAM OF SAME FREQUENCY
AND COHERENCE DIVISION MULTIPLEXING (CDM)
The invention relates to a method for extracting one beam form the mixture of
two mutually incoherent co-propagating beams of same frequency, same state of
polarization and mode but unequal intensity in a Mach-Zehnder interferometer
(MZI) configured with predetermined parameters.

Documents:

01192-kol-2007-abstract.pdf

01192-kol-2007-claims.pdf

01192-kol-2007-correspondence others 1.1.pdf

01192-kol-2007-correspondence others 1.2.pdf

01192-kol-2007-correspondence others.pdf

01192-kol-2007-description complete 1.1.pdf

01192-kol-2007-description complete.pdf

01192-kol-2007-drawings 1.1.pdf

01192-kol-2007-drawings.pdf

01192-kol-2007-form 1 1.1.pdf

01192-kol-2007-form 1.pdf

01192-kol-2007-form 13.pdf

01192-kol-2007-form 18.pdf

01192-kol-2007-form 2.pdf

01192-kol-2007-form 3.pdf

01192-kol-2007-gpa.pdf

01192-kol-2007-priority document.pdf

1192-KOL-2007-(19-08-2013)-ABSTRACT.pdf

1192-KOL-2007-(19-08-2013)-CLAIMS.pdf

1192-KOL-2007-(19-08-2013)-CORRESPONDENCE.pdf

1192-KOL-2007-(19-08-2013)-DESCRIPTION (COMPLETE).pdf

1192-KOL-2007-(19-08-2013)-DRAWINGS.pdf

1192-KOL-2007-(19-08-2013)-FORM-1.pdf

1192-KOL-2007-(19-08-2013)-FORM-2.pdf

1192-KOL-2007-CORRESPONDENCE.pdf

1192-KOL-2007-EXAMINATION REPORT.pdf

1192-KOL-2007-FORM 13-1.1.pdf

1192-KOL-2007-FORM 13.pdf

1192-KOL-2007-FORM 18.pdf

1192-KOL-2007-FORM 26.pdf

1192-KOL-2007-GRANTED-ABSTRACT.pdf

1192-KOL-2007-GRANTED-CLAIMS.pdf

1192-KOL-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

1192-KOL-2007-GRANTED-DRAWINGS.pdf

1192-KOL-2007-GRANTED-FORM 1.pdf

1192-KOL-2007-GRANTED-FORM 2.pdf

1192-KOL-2007-GRANTED-FORM 3.pdf

1192-KOL-2007-GRANTED-SPECIFICATION-COMPLETE.pdf

1192-KOL-2007-REPLY TO EXAMINATION REPORT.pdf

abstract-01192-kol-2007.jpg

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Patent Number

261064

Indian Patent Application Number

1192/KOL/2007

PG Journal Number

23/2014

Publication Date

06-Jun-2014

Grant Date

02-Jun-2014

Date of Filing

30-Aug-2007

Name of Patentee

BIRLA INSTITUTE OF TECHNOLOGY

Applicant Address

MESRA, RANCHI-835215

Inventors:

#	Inventor's Name	Inventor's Address
1	DR. S. MEDHEKAR	C-II/69, BIRLA INSTITUTE OF TECHNOLOGY, MESRA, RANCHI 835215
2	MR. PUNYA PRASANNA PALTANI	L-162 MAHASHAKTI NAGAR DEWAS ROAD, UJJAIN 456010

PCT International Classification Number

G02B6/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA