COHERENT LIGHT RECEIVING DEVICE, SYSTEM, AND METHOD

• US 20130216240A1
• Filed: 10/06/2011
• Published: 08/22/2013
• Est. Priority Date: 11/01/2010
• Status: Abandoned Application

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Fukuchi, Kiyoshi
• Application Number:
  US13/882,707
• Publication Number:
  US 20130216240A1
• Time in Patent Office: Days
• US Class Current: 398/208
• CPC Class Codes: H04B 10/6161 Compensation of chromatic dispersion
• CPC Class Codes: H04B 10/6163 Compensation of non-linear effects in the fiber optic link, e.g. self-phase modulation [SPM], cross-phase modulation [XPM], four wave mixing [FWM]
• CPC Class Codes: H04B 10/6165 Estimation of the phase of the received optical signal, phase error estimation or phase error correction

Abstract

A coherent light receiving device includes a coherent receiving unit which mixes a received optical signal with local light and performs optical coherent detection to output a digital signal, a wavelength dispersion compensation unit which compensates for waveform distortion in the digital signal and outputs a digital signal after compensation, and a frequency difference detection unit which detects the frequency difference between the received optical signal and local light and notifies the wavelength dispersion compensation unit of the frequency difference, wherein the wavelength dispersion compensation unit performs compensation using a transfer function which is based on the frequency difference notified from the frequency difference detection unit and represents waveform distortion due to wavelength dispersion.

Claims

1. A coherent light receiving device comprising:

a coherent receiving unit which receives an optical signal including waveform distortion due to wavelength dispersion, mixes the optical signal with local light, performs optical coherent detection to convert the optical signal to an electrical signal, converts the converted electrical signal to a digital signal, and outputs the digital signal;

a wavelength dispersion compensation unit which compensates for waveform distortion in the digital signal output from the coherent receiving unit and outputs a digital signal after compensation; and

a frequency difference detection unit which receives the digital signal after compensation output from the wavelength dispersion compensation unit, detects the frequency difference between the frequency of the optical signal and the frequency of local light, and notifies the wavelength dispersion compensation unit of the frequency difference,

wherein the wavelength dispersion compensation unit performs compensation using a transfer function which is based on the frequency difference notified from the frequency difference detection unit and represents waveform distortion due to wavelength dispersion.

2. The coherent light receiving device according to claim 1,

wherein the transfer function is a transfer function which represents waveform distortion due to wavelength dispersion at the frequency of the optical signal under the condition that the frequency difference between the frequency of the optical signal and the frequency of local light is a frequency difference f which becomes a specific value, and

the wavelength dispersion compensation unit performs the compensation using a second dispersion compensation factor obtained by shifting a dispersion compensation factor for compensating for waveform distortion represented by the transfer function on a frequency axis with an integer value closest to (f1−

f2)/Δ

F as a shift amount with respect to the frequency difference f1, a second frequency difference f2 notified from the frequency difference detection unit, and a frequency step Δ

F of the dispersion compensation factor.

5. The coherent light receiving device according to claim 1,

wherein the coherent receiving unit has a polarization separation unit which receives a polarization multiplexed optical signal and separates the polarization multiplexed optical signal for each polarization component, and

the optical signal including waveform distortion due to wavelength dispersion is the optical signal separated by the polarization separation unit.

3. A coherent light receiving device comprising:

a coherent receiving unit which receives an optical signal including waveform distortion due to wavelength dispersion, mixes the optical signal with local light, performs optical coherent detection to convert the optical signal to an electrical signal, converts the converted electrical signal to a digital signal, and outputs the digital signal;

a wavelength dispersion compensation unit which compensates for waveform distortion in the digital signal output from the coherent receiving unit and outputs a digital signal after compensation; and

a frequency difference detection unit which receives the digital signal after compensation output from the wavelength dispersion compensation unit, detects the frequency difference between the frequency of the optical signal and the frequency of local light, and notifies the wavelength dispersion compensation unit of the frequency difference,

wherein the wavelength dispersion compensation unit changes the frequency of the digital signal output from the coherent receiving unit on the basis of the frequency difference so as to compensate for the frequency difference, and compensates for waveform distortion in the digital signal after frequency change.

4. The coherent light receiving device according to claim 3,

wherein the wavelength dispersion compensation unit converts the digital signal output from the coherent receiving unit to a frequency spectrum, shifts the frequency spectrum on a frequency axis with an integer value closest to (f1−

f2)/Δ

F as a shift amount with respect to a frequency difference f1 which becomes a specific value as the frequency difference between the frequency of the optical signal and the frequency of local light, a second frequency difference f2 notified from the frequency difference detection unit, and a frequency step Δ

F of the frequency spectrum, and uses a dispersion compensation factor for compensating for waveform distortion due to wavelength dispersion at the frequency of the optical signal in the frequency difference f1.

6. A coherent light receiving method comprising:

receiving an optical signal including waveform distortion due to wavelength dispersion, mixing the optical signal with local light, performing optical coherent detection to convert the optical signal to an electrical signal, and converting the converted electrical signal to a digital signal;

compensating for waveform distortion in the converted digital signal; and

detecting the frequency difference between the frequency of the optical signal and the frequency of local light from the digital signal after compensation,

wherein, when compensating for waveform distortion, the compensation is performed using a transfer function which is based on the detected frequency difference and represents waveform distortion due to wavelength dispersion.

7-9. -9. (canceled)