Optical receiver for wavelength-division-multiplexed signals
View Patent ↗A WDM receiver that includes a single, delay interferometer coupled to an N-channel wavelength-demultiplexing filter provides for the simultaneous conversion of a multiplex of N differential-phase-shift-keyed modulated optical signals of different wavelengths into N intensity-modulated optical signal channels. The Nintensity-modulated optical signals may be individually detected by a bank of N photodiode circuits to recover the modulated data stream or used for optical amplification, regeneration, processing, control, or modulation.
1. A receiver for an optical input signal, the receiver comprising:
a delay interferometer (DI) adapted to receive the optical input signal, wherein the optical input signal is a multiplex of N modulated signals separated from each other by integer multiples of ½T d , where T d is a relative path delay of the DI and N is an integer greater than 1;
a first wavelength-demultiplexing filter (WDF), wherein a first optical output of the DI is coupled to an optical input of the first WDF;
a second WDF, wherein a second optical output of the DI is coupled to an optical input of the second WDF, wherein:
each of the first and second WDFs has N outputs; and
each WDF output is connected to an O-E converter adapted to convert an optical signal from the corresponding WDF into an electrical signal; and
a plurality of differencing circuits, wherein each differencing circuit is associated with an O-E converter of the first WDF and a corresponding O-E converter of the second WDF, wherein each differencing circuit generates a difference between the electrical signals from the corresponding pair of O-E converters.
2. The invention of claim 1 , wherein:
the DI converts the optical input signal into two or more versions of a multiplex of N intensity-modulated optical signals;
the first WDF separates a first version of the multiplex of N intensity-modulated optical signals into N respective different optical channel signals; and
the second WDF separates a second version of the multiplex of N intensity-modulated optical signals into N respective different optical channel signals.
3. The invention of claim 2 , wherein the optical input signal comprises N phase-encoded carriers.
4. The invention of claim 3 , wherein the optical input signal is a DPSK WDM signal.
5. The invention of claim 1 , wherein the optical input signal is a DQPSK or an 8-DPSK WDM signal.
6. The invention of claim 1 , wherein the DI is implemented using a Mach-Zehnder interferometer.
7. A receiver for an optical input signal, wherein the optical input signal is a multiplex of N modulated signals separated from each other by integer multiples of ½T d , where T d is a relative path delay of a delay interferometer and N is an integer greater than 1, the receiver comprising:
a first component adapted to convert the optical input signal into two or more versions of a multiplex of N intensity-modulated optical signals;
a second component adapted to separate a first version of the multiplex of N intensity-modulated optical signals into N respective different optical channel signals;
a third component adapted to separate a second version of the multiplex of N intensity-modulated optical signals into N respective different optical channel signals;
a plurality of O-E converters, wherein each O-E converter is coupled to an output of the second and third components; and
a plurality of differencing circuits, wherein each differencing circuit is associated with an O-E converter of the second component and a corresponding O-E converter of the third component, wherein each differencing circuit generates a difference between the electrical signals from the corresponding pair of O-E converters.
8. The invention of claim 7 , wherein the first component is the delay interferometer (DI) and the second component is a wavelength-demultiplexing filter (WDF).
9. The invention of claim 7 , wherein the first component is the delay interferometer (DI) and each of the second and third components is a wavelength-demultiplexing filter (WDF).
10. A method for processing an optical input signal, wherein the optical input signal is a multiplex of N modulated signals separated from each other by integer multiples of ½T d , where T d is a relative path delay of a delay interferometer and N is an integer greater than 1, the method comprising:
convening the optical input signal into two or more versions of a multiplex of N intensity-modulated optical signals;
separating a first version of the multiplex of N intensity-modulated optical signals into N respective different optical channel signals;
separating a second version of the multiplex of N intensity-modulated optical signals into N respective different optical channel signals;
convening each optical channel signal generated in the separating steps into an electrical channel signal; and
subtracting each electrical channel signal generated by convening optical channel signals from the first version from a corresponding electrical channel signal generated by convening optical channel signals from the second version.
11. The invention of claim 10 , wherein:
the step of convening the optical input signal is implemented using the delay interferometer (DI); and
each of the separating steps is implemented using a respective wavelength-demultiplexing filter (WDF).
12. The invention of claim 10 , wherein the optical channel signals are used for one or more of optical amplification, optical regeneration, optical processing, and optical modulation.
13. The invention of claim 11 , wherein the optical input signal comprises N phase-encoded carriers.
14. The invention of claim 11 , wherein each of said respective WDFs has channel spacing of about ½T d .
15. The invention of claim 1 , wherein each of the first and second WDFs has channel spacing of about ½T d .
16. The invention of claim 9 , wherein each of said WDFs has channel spacing of about ½T d .