Signal processing device used in optical receiver and signal processing method

Patent metadata

Field	Value
Publication number	US-2018034552-A1
Application number	US-201715637389-A
Country	US
Kind code	A1
Filing date	Jun 29, 2017
Priority date	Jul 27, 2016
Publication date	Feb 1, 2018
Grant date	—

Abstract

A signal processing device processes an electric field information signal indicating a polarization multiplexed optical signal in which different modulation formats are used. A first optical signal transmitted in a first polarization component and a second optical signal transmitted in a second polarization component are multiplexed in the polarization multiplexed optical signal. The signal processing device includes a generator and a compensation circuit. The generator selects the first polarization component or the second polarization component based on modulation formats of the first and second optical signals, and generates a compensation value for compensating for an electric field information signal of a selected polarization component based on the electric field information signal of the selected polarization component. The compensation circuit compensates for electric field information signals of the first and second polarization components using the compensation value generated by the generator.

First claim

What is claimed is:

1 . A signal processing device that processes an electric field information signal indicating a polarization multiplexed optical signal in which different modulation formats are used, a first optical signal transmitted in a first polarization component and a second optical signal transmitted in a second polarization component that is orthogonal to the first polarization component being multiplexed in the polarization multiplexed optical signal, the signal processing device comprising:
a generator configured to select the first polarization component or the second polarization component based on a modulation format of the first optical signal and a modulation format of the second optical signal, and to generate a compensation value for compensating for an electric field information signal of a selected polarization component based on the electric field information signal of the selected polarization component; and a compensation circuit configured to compensate for an electric field information signal of the first polarization component and an electric field information signal of the second polarization component using the compensation value generated by the generator.

2 . The signal processing device according to claim 1 , wherein
when the number of bits per symbol of a modulation format of the first polarization component is smaller than the number of bits per symbol of a modulation format of the second polarization component,
the generator generates a compensation value used for compensating for the electric field information signal of the first polarization component based on the electric field information signal of the first polarization component, and
the compensation circuit compensates for the electric field information signal of the first polarization component and the electric field information signal of the second polarization component using the compensation value generated by the generator.

3 . The signal processing device according to claim 1 , wherein
the generator includes:
a compensation value calculator configured to calculate a compensation value used for compensating for the electric field information signal of the first polarization component based on the electric field information signal of the first polarization component, and calculates a compensation value used for compensating for the electric field information signal of the second polarization component based on the electric field information signal of the second polarization component; and
a selector configured to select one of the compensation values generated by the compensation value calculator based on the modulation format of the first optical signal and the modulation format of the second optical signal, and wherein
the compensation circuit compensates for the electric field information signal of the first polarization component and the electric field information signal of the second polarization component using the compensation value selected by the selector.

4 . The signal processing device according to claim 1 , wherein
the generator includes:
a selector configured to select the electric field information signal of the first polarization component or the electric field information signal of the second polarization component based on the modulation format of the first optical signal and the modulation format of the second optical signal; and
a compensation value calculator configured to calculate a compensation value used for compensating for the electric field information signal selected by the selector based on the electric field information signal selected by the selector, and wherein
the compensation circuit compensates for the electric field information signal of the first polarization component and the electric field information signal of the second polarization component using the compensation value calculated by the compensation value calculator.

5 . The signal processing device according to claim 1 , wherein
the compensation circuit is an adaptive equalizer that separates the first polarization component and the second polarization component from each other by a matrix operation, and the generator includes:
a coefficient estimator configured to estimate a portion of coefficients for the matrix operation based on the electric field information signal of the first polarization component when the first polarization component is selected; and
a coefficient converter configured to calculate the other coefficients for the matrix operation based on the portion of the coefficients estimated by the coefficient estimator.

6 . The signal processing device according to claim 1 , wherein
the generator estimates a frequency offset based on the electric field information signal of the first polarization component when the first polarization component is selected, the frequency offset representing a difference between a frequency of a carrier of the polarization multiplexed optical signal and a frequency of a local light source for coherent detection of the polarization multiplexed optical signal, and the compensation circuit compensates for the frequency offset estimated by the generator respectively in the electric field information signal of the first polarization component and the electric field information signal of the second polarization component.

7 . The signal processing device according to claim 1 , wherein
the generator estimates a phase error of the electric field information signal of the first polarization component when the first polarization component is selected, and the compensation circuit compensates for the phase error estimated by the generator respectively in the electric filed information signal of the first polarization component and the electric field information signal of the second polarization component.

8 . A signal processing device that processes an electric field information signal indicating a polarization multiplexed optical signal in which different modulation formats are used, a first optical signal transmitted in a first polarization component and a second optical signal transmitted in a second polarization component that is orthogonal to the first polarization component being multiplexed in the polarization multiplexed optical signal, the signal processing device comprising:
an estimator configured to estimate a crosstalk component between the first polarization component and the second polarization component for each of a plurality of symbols transmitted by the polarization multiplexed optical signal; a weighted averaging unit configured to calculate a weighted average of the crosstalk component estimated for each of the plurality of symbols using a weight that corresponds to a sum of the number of bits per symbol of the modulation format of the first optical signal and the number of bits per symbol of the modulation format of the second optical signal; and a canceller configured to cancel the crosstalk component between the first polarization component and the second polarization component based on the weighted average of the crosstalk component.

9 . A signal processing method for processing an electric field information signal indicating a polarization multiplexed optical signal in which different modulation formats are used, a first optical signal transmitted in a first polarization component and a second optical signal transmitted in a second polarization component that is orthogonal to the first polarization component being multiplexed in the polarization multiplexed optical signal, the signal processing method comprising:
selecting the first polarization component or the second polarization component based on a modulation format of the first optical s

Assignees

• Fujitsu Ltd

Inventors

• Oyama Tomofumi
• Nakashima Hisao
• Nomura Yoshitaka
• Hoshida Takeshi
• Tanimura Takahito

Classifications

• H04B10/6162 Primary

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

• H04L7/0075

  with photonic or optical means · CPC title

• G02B6/4246

  Bidirectionally operating package structures · CPC title

• G02B6/12009

  comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides · CPC title

• 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