Multi-channel optical transceiver with offset quadrature amplitude modulation

Patent metadata

Field	Value
Publication number	US-9515767-B2
Application number	US-201313927901-A
Country	US
Kind code	B2
Filing date	Jun 26, 2013
Priority date	Jan 21, 2010
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

The present disclosure provides a multi-carrier optical transmitter, receiver, transceiver, and associated methods utilizing offset quadrature amplitude modulation thereby achieving significant increases in spectral efficiency, with negligible sensitivity penalties. In an exemplary embodiment, an optical transmitter includes circuitry configured to generate a plurality of optical subcarriers, a plurality of data signals for each of the plurality of subcarriers, and a plurality of modulator circuits for each of the plurality of subcarriers, wherein each of the plurality of modulator circuits includes circuitry configured to offset an in-phase component from a quadrature component of one of the plurality data signals by one-half baud period.

First claim

What is claimed is:

1. An optical receiver, comprising:
a splitter configured to split a received optical signal into N copies where N comprises a number of subcarriers;
a polarization splitter for each of the N copies configured to split the received optical signal into two polarizations;
a coherent optical hybrid for each of the N copies configured to receive the two polarizations of the received optical signal and an output from a local oscillator for each of the N copies, wherein the local oscillator comprises a frequency tuned substantially to match a corresponding subcarrier frequency;
a postfilter located subsequent to the coherent optical hybrid configured to reject, for each of the N copies, adjacent subcarriers and adjacent symbols based on which copy of the N copies is being addressed and the postfilter configured to implement pulse-shape filtering complementary to transmitter pulse-shaping and to provide chromatic dispersion compensation; and
a data decoder.

2. The optical receiver of claim 1 , wherein the received optical signal comprises an offset quadrature amplitude modulation format on each of the subcarriers where in-phase components and quadrature components on each of the subcarriers are offset by one-half baud rate, and wherein each subcarrier is modulated with a corresponding sub-data signal and a data signal is collectively formed by a plurality of sub-data signals.

3. The optical receiver of claim 2 , wherein the local oscillator is locked to the corresponding subcarrier frequency through one of laser injection locking, optical phase-locked loop feedback, or subsequent processing in an electronic block.

4. The optical receiver of claim 2 , wherein separation of the subcarriers is performed in an electrical domain.

5. The optical receiver of claim 2 , further comprising:
circuitry configured to provide polarization mode dispersion compensation.

6. The optical receiver of claim 1 , wherein the data decoder forms a composite electrical signal with at least 1 Tb/s and utilizes less than 500 GHz of optical spectral width.

7. An optical transceiver, comprising:
a transmitter portion comprising:
circuitry configured to generate a plurality of optical subcarriers;
a plurality of data signals for each of the plurality of subcarriers;
a plurality of modulator circuits for each of the plurality of subcarriers; and
polarization multiplexing components for each of the plurality of subcarriers; and

a receiver portion comprising:
a splitter configured to split a received optical signal into N copies where N comprises a number of the;
a polarization splitter for each of the N copies configured to split the received optical signal into two polarizations;
a coherent optical hybrid for each of the N copies configured to receive the two polarizations of the received optical signal and an output from a local oscillator for each of the N copies, wherein the local oscillator comprises a frequency tuned substantially to match a corresponding subcarrier frequency; and
a postfilter located subsequent to the coherent optical hybrid configured to reject, for each of the N copies, adjacent subcarriers and adjacent symbols based on which copy of the N copies is being addressed and the postfilter configured to implement pulse-shape filtering complementary to transmitter pulse-shaping and to provide chromatic dispersion compensation.

8. The optical transceiver of claim 7 , wherein each of the plurality of modulator circuits comprises circuitry configured to offset an in-phase component from a quadrature component of one of the plurality data signals by one-half baud period.

9. The optical transceiver of claim 7 , wherein the received optical signal comprises an offset quadrature amplitude modulation format on each of the subcarriers where in-phase components and quadrature components on each of the subcarriers are offset by one-half baud rate, and wherein each subcarrier is modulated with a corresponding sub-data signal and a data signal is collectively formed by a plurality of sub-data signals.

10. The optical transceiver of claim 7 , wherein the polarization multiplexing components further comprise:
a splitter splitting each of the plurality of subcarriers into two components, wherein the plurality of modulator circuits comprise modulator circuits for each of the plurality of subcarrier components; and
a polarization combiner combining each of the subcarrier components to form a polarization multiplexed signal with horizontal and vertical components.

11. An optical demodulation method, comprising:
splitting a received optical signal into N copies with N comprising a number of subcarriers associated with the received optical signal, wherein the received optical signal comprises an offset quadrature amplitude modulation format on each of the subcarriers where in-phase components and quadrature components on each of the subcarriers are offset by one-half baud rate, and wherein each subcarrier is modulated with a corresponding sub-data signal and a data signal is collectively formed by a plurality of sub-data signals;
inputting each of the N copies into an associated coherent optical hybrid with a local oscillator at a frequency matching a corresponding subcarrier frequency associated therewith;
filtering, via a postfilter, subsequent to the coherent optical hybrid an output of each the associated coherent optical hybrids for chromatic dispersion, for pulse shaping, and for rejecting, for each of the N subcarriers, adjacent subcarriers and adjacent symbols based on which copy of the N copies is being addressed; and
performing data decoding for each of the N subcarriers.

12. The optical demodulation method of claim 11 , further comprising:
performing the filtering electronically thereby removing all other subcarriers except a subcarrier of interest.

13. The optical demodulation method of claim 11 , further comprising:
performing polarization demultiplexing on each of the N subcarriers and polarization mode dispersion compensation.

14. The optical demodulation method of claim 11 , further comprising:
combining the decoded data from each of the N subcarriers to form a composite electrical signal.

15. The optical demodulation method of claim 14 , wherein the composite electrical signal comprises at least 1 Tb/s and utilizes less than 500 GHz of spectral width.

Assignees

• Frankel Michael Y
• Bourget Christian
• Wingrove Michael J
• Ciena Corp

Inventors

• Frankel Michael Y
• Bourget Christian
• Wingrove Michael J

Classifications

• H04B10/614

  comprising one or more polarization beam splitters, e.g. polarization multiplexed [PolMux] X-PSK coherent receivers, polarization diversity heterodyne coherent receivers (H04J14/06 takes precedence) · CPC title

• H04B10/6161

  Compensation of chromatic dispersion · CPC title

• H04B10/61

  Coherent receivers · CPC title

• H04B10/64

  Heterodyne {, i.e. coherent receivers where, after the opto-electronic conversion, an electrical signal at an intermediate frequency [IF] is obtained} · CPC title

• H04B10/541

  Digital intensity or amplitude modulation · CPC title