Systems and methods for the compensation of nonlinear cross polarization and cross phase modulation in dual polarization coherent channels

Patent metadata

Field	Value
Publication number	US-9419725-B2
Application number	US-201414482776-A
Country	US
Kind code	B2
Filing date	Sep 10, 2014
Priority date	Aug 20, 2012
Publication date	Aug 16, 2016
Grant date	Aug 16, 2016

Abstract

The present disclosure provides systems and methods for the compensation of signal distortion in fiber optic communication systems and the like. More specifically, the present disclosure provides an orthogonal polarization detection and broadband pilot (OPDBP) technique for the compensation of nonlinear cross polarization (i.e. nonlinear cross polarization modulation) (XPolM) induced noise and nonlinear nonlinear cross phase modulation (XPM) induced noise in a high data rate polarization multiplexed (PM) multilevel-quadrature amplitude modulated (M-QAM) channel due to neighboring channels. This approach allows for the compensation of both XPolM and XPM simultaneously, providing several dBs of optical reach extension. The approach uses a pilot tone based orthogonal polarization detection scheme with broadband (i.e. a few GHz wide) filtering of the pilot tones.

First claim

What is claimed is:

1. A method, in a receiver, for compensation of nonlinear cross phase polarization and cross phase modulation in a dual polarization coherent optical system, the method comprising:
receiving a dual polarization optical signal with two pilot tones, each of the two pilot tones is i) at a different frequency thereby avoiding mixing during propagation from the transmitter and ii) in a same State of Polarization (SOP) as respective data signals associated with the dual polarization optical signal;
obtaining a Horizontal polarization (H-pol) pilot and a Vertical (V-pol) polarization pilot from the received dual polarization optical signal; and
determining scalar products using the H-pol pilot, the V-pol pilot, and a signal pilot, wherein the scalar products are indicative of fast nonlinear cross polarization modulation-induced polarization variations and nonlinear cross phase modulation-induced phase variations during the propagation, for use in the compensation.

2. The method of claim 1 , wherein the H-pol pilot and the V-pol pilot are fully separable in frequency prior to polarization demultiplexing of electrical data signals associated with the dual polarization optical signal.

3. The method of claim 1 , further comprising:
performing polarization demultiplexing of electrical data signals associated with the dual polarization optical signal, using the H-pol pilot and the V-pol pilot, wherein common mode phase noise terms, both linear laser related and nonlinear cross talk related, are compensated automatically in the polarization demultiplexing.

4. The method of claim 1 , wherein the receiver is an analog Gilbert cell mixer-based receiver.

5. The method of claim 1 , wherein the receiver is a Digital Signal Processor (DSP)-based receiver configured to digitally compensate Polarization Mode Dispersion.

6. The method of claim 1 , further comprising:
broadband filtering the H-pol pilot and the V-pol pilot in a range up to a few GHz where an overwhelming amount of nonlinear noise due to the nonlinear cross polarization modulation and nonlinear cross phase modulation is located.

7. The method of claim 6 , wherein the broadband filtering is in a range of 1.5 GHz to 3 GHz.

8. The method of claim 1 , wherein the H-pol pilot and the V-pol pilot are indicative of a Jones matrix due to the propagation.

9. A method, in a transmitter, allowing for compensation of nonlinear cross phase polarization and cross phase modulation in a dual polarization coherent optical system, at a receiver, the method comprising:
inserting a Horizontal polarization (H-pol) pilot tone, at a first frequency, with a data signal associated with a Horizontal polarization;
inserting a Vertical (V-pol) polarization pilot tone, at a second frequency, with a data signal associated with a Vertical polarization, wherein the first frequency and the second frequency are different thereby avoiding mixing during propagation to the receiver; and
transmitting, to the receiver, a dual polarization optical signal that includes the H-pol pilot tone, the V-pol pilot tone, the data signal associated with the Horizontal polarization, and the data signal associated with the Vertical polarization.

10. The method of claim 9 , wherein the H-pol pilot tone and the V-pol pilot tone are used by the receiver to capture fast nonlinear cross polarization modulation-induced polarization variations and nonlinear cross phase modulation-induced phase variations during the propagation, based on recovering the H-pol pilot tone and the V-pol pilot tone.

11. The method of claim 9 , wherein the H-pol pilot and the V-pol pilot are fully separable in frequency prior to polarization demultiplexing of electrical data signals, at the receiver, associated with the dual polarization optical signal.

12. The method of claim 9 , wherein the H-pol pilot and the V-pol pilot are indicative of a Jones matrix due to the propagation from the transmitter to the receiver.

13. The method of claim 9 , wherein the transmitter utilizes coherent modulation.

14. The method of claim 9 , wherein the data signal associated with the Horizontal polarization and the data signal associated with the Vertical polarization are orthogonal frequency division multiplexed.

15. A system for compensation of nonlinear cross phase polarization and cross phase modulation in a dual polarization coherent optical system, the system comprising:
a transmitter configured to transmit a dual polarization optical signal with a Horizontal polarization (H-pol) pilot and a Vertical (V-pol) polarization pilot, each of the H-pol pilot and the V-pol pilot is i) at a different frequency thereby avoiding mixing during propagation from the transmitter and ii) in a same State of Polarization (SOP) as respective data signals associated with the dual polarization optical signal; and
a receiver communicatively coupled to the transmitter and configured to
receive the dual polarization optical signal with the two pilot tones, and
determine scalar products using the received H-pol pilot, the received V-pol pilot, and a signal pilot, wherein the scalar products are indicative of fast nonlinear cross polarization modulation-induced polarization and nonlinear cross phase modulation-induced phase variations during the propagation for compensation of both using the scalar products.

16. The system of claim 15 , wherein the transmitter is configured to, prior to transmitting to the receiver,
insert the H-pol pilot, at a first frequency, with the respective data signal associated with a Horizontal polarization of the dual polarization optical signal, and
insert the V-pol pilot, at a second frequency that is different from the first frequency, with the respective data signal associated with a Vertical polarization of the dual polarization optical signal.

17. The system of claim 15 , wherein the receiver is an analog Gilbert cell mixer-based receiver.

18. The system of claim 15 , wherein the receiver is a Digital Signal Processor (DSP)-based receiver configured to digitally compensate Polarization Mode Dispersion.

19. The system of claim 16 , wherein the transmitter utilizes coherent modulation.

20. The system of claim 16 , wherein the data signal associated with the Horizontal polarization and the data signal associated with the Vertical polarization are orthogonal frequency division multiplexed.

Assignees

• Grigoryan Vladimir S
• Frankel Michael Y
• Ciena Corp

Inventors

• Grigoryan Vladimir S
• Frankel Michael Y

Classifications

• H04B10/2572 Primary

  due to forms of polarisation-dependent distortion other than PMD · CPC title

• H04B10/6162 Primary

  Compensation of polarization related effects, e.g., PMD, PDL · CPC title

• H04J14/06

  Polarisation multiplex systems · CPC title