# US 8,542,992 B2 · System and method for mitigating polarization hole burning

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- Number: US 8,542,992 B2
- Document ID: US8542992B2
- Status: Granted
- Kind: B2
- Application number: 12/713,792
- Filed: 2010-02-26
- Published: 2011-09-01
- Granted: 2013-09-24
- Earliest claimed: 2010-02-26
- Assignees: Fujitsu Limited
- Applicants: Kevan P. Jones; Denis Daniel Leclair; Sean D. L. McVeigh; Jean V. E. Ouellet; Douglas J. Greenwood; John B. Mills; Robert W. Keys
- Inventors: Kevan P. Jones; Denis Daniel Leclair; Sean D. L. McVeigh; Jean V. E. Ouellet; Douglas J. Greenwood; John B. Mills; Robert W. Keys
- Web page: https://patentgrep.com/patent/US8542992B2

## CPC

- H04B 10/2572: {due to forms of polarisation-dependent distortion other than PMD}
- H04B 10/291: in which processing or amplification is carried out without conversion of the main signal from optical form
- H04J 14/0204: {Broadcast and select arrangements, e.g. with an optical splitter at the input before adding or dropping}
- H04J 14/0212: {using optical switches or wavelength selective switches [WSS]}
- H04J 14/0217: {Multi-degree architectures, e.g. having a connection degree greater than two}
- H04J 14/02216: {by gain equalization}
- H04J 14/0257: {Wavelength assignment algorithms}
- H04J 14/0269: {using tables for routing}
- H04B: TRANSMISSION
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)

## Abstract

A system for mitigating the effects of polarization hole burning in an optical communication system. The system includes an optical input signal comprising one or more traffic channels, a measurement module configured to check for the existence of ghost channels around the traffic channels, and a ghost channel generation module configured to generate a ghost channel around the traffic channels from amplified spontaneous emission noise of the optical input signal.

## Claims

### Claim 1

A system for mitigating the effects of polarization hole burning in an optical communication system, comprising:
an optical input signal including one or more traffic channel(s);
a measurement module configured to check for the existence of ghost channels around the traffic channel(s);
a ghost channel generation module configured to generate a ghost channel around the traffic channel(s) at least by amplifying a spontaneous emission of the optical input signal;
a power monitor configured to measure at least a signal strength of the ghost channel and one of the traffic channels;
a comparator configured to compare the signal strength of the ghost channel and the signal strength of the traffic channel; and
an amplification module configured to amplify the signal strength of the ghost channel if the signal strength of the ghost channel is not substantially equal to the signal strength of the traffic channel.

### Claim 2 (depends on 1)

The system of claim 1, wherein the ghost channel generation module is part of a wavelength selection switch within the optical communication system.

### Claim 3 (depends on 1)

The system of claim 1, wherein the measurement module is part of a wavelength selection switch within the optical communication system.

### Claim 4 (depends on 1)

The system of claim 1, wherein the measurement module is part of a wavelength selection switch within the optical communication system.

### Claim 5 (depends on 1)

The system of claim 1, wherein the comparator is part of a wavelength selection switch within the optical communication system.

### Claim 6 (depends on 1)

The system of claim 1, wherein the amplification module is part of a wavelength selection switch within the optical communication system.

### Claim 7 (depends on 1)

The system of claim 1, wherein the amplification module is configured to limit amplification of the signal strength of the ghost channel so that it does not substantially exceed the signal strength of the optical input signal.

### Claim 8

A method for mitigating the effects of polarization hole burning in an optical communication system, comprising:
receiving an optical input signal at a first node of the optical communication system, the optical input signal including one or more traffic channel(s);
checking for the existence of a ghost channel around the traffic channel(s);
generating a ghost channel around the traffic channel(s) at least by amplifying a spontaneous emission of the optical input signal;
forwarding the traffic channel(s) and the ghost channel to a second node of the optical communication system;
measuring at least a signal strength of the traffic channel;
measuring at least a signal strength of the ghost channel;
determining if the signal strength of the ghost channel is substantially equal to the signal strength of the traffic channel; and
amplifying the signal strength of the ghost channel if the signal strength of the ghost channel is not substantially equal to the signal strength of the traffic channel.

### Claim 9 (depends on 8)

The method of claim 8, wherein generating a ghost channel around the traffic channel comprises generating one ghost channel on each side of the optical input signal.

### Claim 10 (depends on 8)

The method of claim 8, wherein the ghost channel is within two channel separation wavelengths of the traffic channel.

### Claim 11 (depends on 8)

The method of claim 8, further comprising determining the isolation level of the traffic channel.

### Claim 12 (depends on 11)

The method of claim 11, wherein determining the isolation level of the traffic channel comprises determining whether immediately neighboring channels are traffic channels.

### Claim 13 (depends on 11)

The method of claim 11, wherein determining the isolation level of the traffic channel comprises determining whether only one immediately neighboring channel is a traffic channel.

### Claim 14

A method for mitigating the effects of polarization hole burning in an optical communication system, comprising:
receiving an optical input signal at a first node of the optical communication system, the optical input signal comprising one or more traffic channel(s);
forwarding the traffic channel(s) to a second node of the optical communication system;
amplifying at least a spontaneous emission noise of the optical input signal to generate a ghost channel;
forwarding the traffic channel(s) and the ghost channel to a third node of the optical communication system;
comparing an optical strength of the ghost channel to an optical strength of the traffic channel(s);
if the optical strength of the ghost channel is substantially equal to the optical strength of the traffic channel(s), capping amplification of the ghost channel; and
if the optical strength of the ghost channel is not substantially equal to the optical strength of the traffic channel(s), amplifying the ghost channel.