Method and apparatus for automatic compensation of chromatic dispersion

Patent metadata

Field	Value
Publication number	US-2018205461-A1
Application number	US-201715406027-A
Country	US
Kind code	A1
Filing date	Jan 13, 2017
Priority date	Jan 13, 2017
Publication date	Jul 19, 2018
Grant date	—

Abstract

A chromatic dispersion compensation apparatus for automatic compensation of chromatic dispersion of signals transmitted via an optical link at predetermined wavelengths of WDM channels within a predetermined band. A tapping unit taps optical signals received by the chromatic dispersion compensation apparatus via the optical link at predetermined wavelengths and supply them to an optical coherent receiver adapted to tune its local oscillator to WDM channels to generate corresponding analog electrical signals of the WDM channels which are sampled by an analog digital converter to provide digital signal samples of WDM channels processed by a digital signal processor of the chromatic dispersion compensation apparatus to calculate an estimate residual chromatic dispersion value of the received optical signals. A tuneable dispersion compensation module is set to perform optical compensation of a residual chromatic dispersion of the received optical signals depending on calculated estimate residual chromatic dispersion value of the received optical signals.

First claim

1 . A chromatic dispersion compensation apparatus for automatic compensation of chromatic dispersion, CD, of signals transmitted via an optical link at predetermined wavelengths of WDM channels within a predetermined band of a WDM system, the chromatic dispersion compensation apparatus having a signal input and a signal output, and comprising:
an amplifier connected to the signal input for amplifying optical signals received at the signal input; and a tapping unit coupled to the signal output and receiving the amplified optical signals from the amplifier via an internal signal line coupled to the amplifier, the tapping unit adapted such that the amplified optical signals output by the amplifier can travel through the tapping unit to the signal output and adapted to tap the amplified optical signals received by the chromatic dispersion compensation apparatus at its signal input via the optical link at predetermined wavelengths and adapted to supply the tapped optical signals to an optical coherent receiver adapted to tune its local oscillator to selected WDM channels to generate corresponding analog electrical signals of the different WDM channels which are sampled by an analog digital converter, ADC, to provide digital signal samples of the selected WDM channels processed by a digital signal processor, DSP, of the chromatic dispersion compensation apparatus to calculate an estimate residual chromatic dispersion value of the received optical signals; wherein a tuneable dispersion compensation module, TDCM, of the chromatic dispersion compensation apparatus is set to perform an optical compensation of a residual chromatic dispersion, rCD, of the received optical signals depending on the calculated estimate residual chromatic dispersion value of the received optical signals.

2 . The chromatic dispersion compensation apparatus according to claim 1 , wherein a bulk amount of chromatic dispersion, bCD, is compensated by a fixed dispersion compensation module, DCM, connected in the optical link, upstream of the signal input.

3 . The chromatic dispersion compensation apparatus according to claim 1 , wherein the residual chromatic dispersion, rCD, of the received optical signals is compensated in two compensation stages comprising a coarse compensation stage and a fine compensation stage;
wherein in the coarse compensation stage, the digital signal processor, DSP, is used to estimate a coarse value of the residual chromatic dispersion, rCD, communicated to the tuneable dispersion compensation module, TDCM, which performs a compensation of the received optical signals depending on the estimated coarse value of the residual chromatic dispersion; and wherein in the fine compensation stage, an error vector magnitude, EVM, of the received optical signals is calculated and used as a metric for fine tuning of the chromatic dispersion setting of the tuneable dispersion compensation module, TDCM.

4 . The chromatic dispersion compensation apparatus according to claim 1 , wherein the estimate residual chromatic dispersion value of the received optical signals calculated by the digital signal processor, DSP, is communicated to a setting processor adapted to set the tuneable dispersion compensation module, TDCM, according to the communicated estimate residual chromatic dispersion value.

5 . The chromatic dispersion compensation apparatus according to claim 1 , comprising:
a probe signal generation unit adapted to generate a probe signal having a fixed or tuneable wavelength; and the probe signal being supplied to the optical link and used for estimation of chromatic dispersion, CD.

6 . The chromatic dispersion compensation apparatus according to claim 1 , wherein the digital samples output by the analog digital converter, ADC, are stored in a memory and processed by the digital signal processor, DSP, in an offline processing mode.

7 . The chromatic dispersion compensation apparatus according to claim 1 , wherein the tuneable dispersion compensation module, TDCM, is collocated with the tapping unit, the optical coherent receiver, the digital signal processor, DSP, and the setting processor on a receiver line card at a receiver side of the optical link.

8 . The chromatic dispersion compensation apparatus according to claim 1 , wherein the tuneable dispersion compensation module, TDCM, is located on a transmitter line card at a transmitter side of the optical link and receives the chromatic dispersion compensation setting from a setting processor located on a receiver side via an optical supervisory channel, OSC, through the optical link.

9 . The chromatic dispersion compensation apparatus according to claim 1 , wherein the tapping unit comprises an optical splitter, an optical switch or an optical filter.

10 . The chromatic dispersion compensation apparatus according to claim 1 , wherein the tapping unit is connected to an output of an optical preamplifier of a receiver line card or to an output of an optical demultiplexer connected to the output of an optical preamplifier of a receiver line card.

11 . The chromatic dispersion compensation apparatus according to claim 1 , wherein the optical coherent receiver comprises a dual-polarization IQ coherent receiver.

12 . The chromatic dispersion compensation apparatus according to claim 1 , wherein the local oscillator of the optical coherent receiver comprises a tuneable laser diode.

13 . A method for automatic compensation of chromatic dispersion of signals transmitted via an optical link at predetermined wavelengths of WDM channels within a predetermined band of a WDM system, the method, being carried out by a chromatic dispersion compensation apparatus having a signal input and signal output, comprising:
amplifying, by an amplifier of the chromatic dispersion compensation apparatus connected to the signal input, optical signals received at the signal input; tapping, by a tapping unit coupled to the signal output and receiving the amplified optical signals from the amplifier via an internal signal line coupled to the amplifier, the tapping unit being adapted such that the amplified optical signals output by the amplifier can travel through the tapping unit to the signal output, optical signals received via the optical link at predetermined wavelengths and supplying the tap signals to an optical coherent receiver; tuning a local oscillator of the optical coherent receiver to selected WDM channels to generate corresponding analog electrical signals of the different WDM channels; sampling the analog electrical signals by an analog digital converter to provide digital signal samples of the different WDM channels; processing the digital signal samples by a digital signal processor, DSP, to calculate a residual chromatic dispersion value of the received optical signals; and setting a tuneable dispersion compensation module, TDCM, to perform an optical compensation of a residual chromatic dispersion, rCD, of the received optical signals depending on the calculated residual chromatic dispersion value of the received optical signals.

14 . The method according to claim 13 , wherein a bulk amount of chromatic dispersion, bCD, of the optical link is compensated by a fixed dispersion compensation module, DCM, connected in the optical link upstream of the signal input.

15 . The method according to claim 13 , wherein the residual chromatic dispersion, rCD, of the received optical signals is compensated in two compensation stages comprising a coarse compensation stage and a fine compensation stage;
wherein in the coarse compensation stage, a dedicated digital signal processor, DSP, is used to es

Assignees

• Adva Optical Networking Se

Inventors

• Alfiad Mohammad
• Tibuleac Sorin
• Fuerst Cornelius
• Meyer Christophe

Classifications

• H04B10/2513 Primary

  due to chromatic dispersion · CPC title

• H04J14/02

  Wavelength-division multiplex systems · CPC title

• H04B10/25133 Primary

  including a lumped electrical or optical dispersion compensator (H04B10/2519, H04B10/2525 takes precedence) · CPC title