Nonlinear tolerant optical modulation formats at high spectral efficiency

Patent metadata

Field	Value
Publication number	US-9749058-B2
Application number	US-201514744395-A
Country	US
Kind code	B2
Filing date	Jun 19, 2015
Priority date	Jun 19, 2015
Publication date	Aug 29, 2017
Grant date	Aug 29, 2017

Abstract

Techniques for transmitting a data signal through an optical communications system. An encoder is configured to encode the data signal to generate symbols to be modulated onto an optical carrier. Each symbol encodes multiple bits of data and includes a first portion selected from a first constellation and a second portion selected from a second constellation. The first and second constellations have respective different average amplitudes. Each of the first and second constellations have a cardinality of at least two and the cardinality of the first constellation is greater than the cardinality of the second constellation. A modulator is configured to modulate a first frame of the optical signal using the first portion and modulate a second frame of the optical signal using the second portion. A selection of one frame of the optical signal to be used as the first frame encodes at least 1 bit of data.

First claim

We claim:

1. A method of transmitting a data signal through an optical communications system, the method comprising:
encoding the data signal to generate symbols to be modulated onto an optical carrier in successive signaling intervals, each symbol encoding a plurality of bits of data and comprising a first constellation point selected from a first constellation and a second constellation point selected from a second constellation, wherein the first and second constellations have respective different average amplitudes, each of the first and second constellations have a cardinality of at least two and the cardinality of the first constellation is greater than the cardinality of the second constellation; and
modulating a first frame of the optical signal in accordance with the first constellation point and modulating a second frame of the optical signal in accordance with the second constellation point;
wherein a selection of one frame of the optical signal to be used as the first frame of the optical signal encodes at least 1 bit of data.

2. The method of claim 1 , wherein the first and second frames of the optical signal comprise respective first and second sub-carrier wavelengths of the optical signal.

3. The method of claim 1 , wherein the first and second frames of the optical signal comprise respective first and second polarizations of the optical signal.

4. The method of claim 3 , wherein a selection of either an X-polarization or a Y-polarization of the optical signal as the first frame encodes 1 bit of data; the first constellation is a phase shift keying constellation that encodes 3 bits of data, and the second constellation is a phase shift keying constellation that encodes 2 bits of data.

5. The method of claim 3 , wherein the 1 bit of data used to select either the X-polarization or the Y-polarization of the optical signal as the first frame corresponds with a most significant bit (MSB) of the data signal, the next most significant bits are encoded for transmission on the X-polarization, and the least significant bits of the data signal are encoded for transmission on the Y-polarization.

6. The method of claim 3 , wherein the 1 bit of data used to select either the X-polarization or the Y-polarization of the optical signal as the first frame corresponds with a most significant bit (MSB) of the data signal, the next most significant bits are encoded for transmission on the Y-polarization, and the least significant bits of the data signal are encoded for transmission on the X-polarization.

7. The method of claim 3 , wherein the 1 bit of data used to select either the X-polarization or the Y-polarization of the optical signal as the first frame corresponds with a least significant bit (LSB) of the data signal, the next least significant bits are encoded for transmission on the X-polarization, and the most significant bits of the data signal are encoded for transmission on the Y-polarization.

8. The method of claim 3 , wherein the 1 bit of data used to select either the X-polarization or the Y-polarization of the optical signal as the first frame corresponds with a least significant bit (LSB) of the data signal, the next least significant bits are encoded for transmission on the Y-polarization, and the most significant bits of the data signal are encoded for transmission on the X-polarization.

9. A transmitter for transmitting a data signal through an optical communications system, the transmitter being configured to modulate an optical carrier in successive signaling intervals to generate and optical signal for transmission through the optical communications system, the transmitter comprising:
an encoder configured to encode the data signal to generate symbols to be modulated onto the optical carrier, each symbol encoding a plurality of bits of data and comprising a first constellation point selected from a first constellation and a second constellation point selected from a second constellation, wherein the first and second constellations have respective different average amplitudes, each of the first and second constellations have a cardinality of at least two and the cardinality of the first constellation is greater than the cardinality of the second constellation; and
a modulator configured to modulate a first frame of the optical signal in accordance with the first constellation point and modulate a second frame of the optical signal in accordance with the second constellation point;
wherein a selection of one frame of the optical signal to be used as the first frame of the optical signal encodes at least 1 bit of data.

10. The transmitter of claim 9 , wherein the first and second constellations are selected such that a variance of symbol energy of two successively transmitted symbols divided by the square of the average energy of these symbols is at most 0.05.

11. The transmitter of claim 10 , wherein each symbol encodes 6 bits of data.

12. The transmitter of claim 10 , wherein the respective amplitudes of the first and second constellations are selected such that R A 2 +R B 2 =1, where R A is a first radius indicative of the average amplitude of the first constellation and R B is a second radius indicative of the average amplitude of the second constellation.

13. The transmitter of claim 10 , wherein each of the first and second constellations comprise a respective plurality of complex valued points, and the encoder is configured to encode the data signal by selecting one complex valued point from the first constellation, and selecting one complex valued point from the second constellation.

14. The transmitter of claim 9 , wherein the first and second frames of the optical signal comprise respective first and second sub-carrier wavelengths of the optical signal.

15. The transmitter of claim 9 , wherein the first and second frames of the optical signal comprise respective first and second polarizations of the optical signal.

16. The transmitter of claim 15 , wherein a selection of either an X-polarization or a Y-polarization of the optical signal as the first frame encodes 1 bit of data; the first constellation is a phase shift keying constellation that encodes 3 bits of data, and the second constellation is a phase shift keying constellation that encodes 2 bits of data.

17. The transmitter of claim 15 , wherein the 1 bit of data used to select either the X-polarization or the Y-polarization of the optical signal as the first frame corresponds with a most significant bit (MSB) of the data signal, the next most significant bits are encoded for transmission on the X-polarization, and the least significant bits of the data signal are encoded for transmission on the Y-polarization.

18. The transmitter of claim 15 , wherein the 1 bit of data used to select either the X-polarization or the Y-polarization of the optical signal as the first frame corresponds with a most significant bit (MSB) of the data signal, the next most significant bits are encoded for transmission on the Y-polarization, and the least significant bits of the data signal are encoded for transmission on the X-polarization.

19. The transmitter of claim 15 , wherein the 1 bit of data used to select either the X-polarization or the Y-polarization of the optical signal as the first frame corresponds with a least significant bit (LSB) of the data signal, the next least significant bits are encoded for transmission on the X-polarization, and the most significant bits of the data signal are encoded for transmission on the Y-polarization.

20. The transmitte

Assignees

• Reimer Michael Andrew
• Oveis Gharan Shahab
• Shiner Andrew D
• O'Sullivan Maurice
• Ciena Corp

Inventors

• Reimer Michael Andrew
• Oveis Gharan Shahab
• Shiner Andrew D
• O'Sullivan Maurice

Classifications

• H04B10/69

  Electrical arrangements in the receiver · CPC title

• H04L27/3405

  Modifications of the signal space to increase the efficiency of transmission, e.g. reduction of the bit error rate, bandwidth, or average power · CPC title

• H04B10/2507

  for the reduction or elimination of distortion or dispersion · CPC title

• H04B10/516

  Details of coding or modulation · CPC title

• H04B10/532

  Polarisation modulation · CPC title