# US 7,609,969 B2 · Method and system for compensating for optical dispersion in an optical signal

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- Number: US 7,609,969 B2
- Document ID: US7609969B2
- Status: Granted
- Kind: B2
- Application number: 11/311,717
- Filed: 2005-12-19
- Published: 2007-06-21
- Granted: 2009-10-27
- Earliest claimed: 2005-12-19
- Assignees: Fujitsu Limited
- Inventors: Olga I. Vassilieva; Susumu Kinoshita
- Web page: https://patentgrep.com/patent/US7609969B2

## CPC

- H04L 25/03006: {Arrangements for removing intersymbol interference}
- H04B 10/25133: {including a lumped electrical or optical dispersion compensator (H04B10/2519, H04B10/2525 takes precedence)}
- H04J 14/0204: {Broadcast and select arrangements, e.g. with an optical splitter at the input before adding or dropping}
- H04J 14/0209: {Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers}
- H04J 14/0213: {Groups of channels or wave bands arrangements}
- H04J 14/0219: {Modular or upgradable architectures}
- H04J 14/0227: {Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation}
- H04L 2025/03375: {Passband transmission}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- 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 method for compensating for optical dispersion in an optical signal includes receiving an optical signal comprising a plurality of channels. The information being communicated in a first set of channels is modulated using a first modulation technique, and the information being communicated in a second set of channels is modulated using a second modulation technique. The method also includes compensating for optical dispersion in the optical signal such that dispersion compensation for the first set of channels is complete and such that dispersion compensation for the second set of channels is incomplete. In addition, the method includes splitting the optical signal into a first copy and a second copy, terminating the second set of channels in the first copy, performing additional dispersion compensation on the second copy such that dispersion compensation for the second set of channels is complete, and terminating the first set of channels in the second copy.

## Claims

### Claim 1

A method for dispersion compensation of an optical signal, comprising:
receiving an optical signal comprising a plurality of channels, wherein the information being communicated in a first set of one or more of the channels is modulated using a first modulation technique and wherein the information being communicated in a second set of one or more of the channels is modulated using a second modulation technique;
compensating for optical dispersion in the optical signal such that dispersion compensation for the first set of channels is complete for the first modulation technique and such that dispersion compensation for the second set of channels is incomplete for the second modulation technique;
splitting the optical signal into at least a first copy of the optical signal and a second copy of the optical signal;
terminating the second set of channels in the first copy;
performing additional dispersion compensation on the second copy such that dispersion compensation for the second set of channels is complete for the second modulation technique; and
terminating the first set of channels in the second copy.

### Claim 2 (depends on 1)

The method of claim 1, wherein:
the information being communicated in the first set of channels is communicated at 10 GB/s; and
the information being communicated in the second set of channels is communicated at 40 GB/s.

### Claim 3 (depends on 1)

The method of claim 1, further comprising combining the channels in the first and second copies of the optical signal that are not terminated to form a compensated optical signal.

### Claim 4 (depends on 1)

The method of claim 1, further comprising:
before performing dispersion compensation on the second copy, splitting the second copy into a third copy and a fourth copy, wherein the additional dispersion compensation is performed on the fourth copy;
demultiplexing the channels of the third copy; and
dropping the information in one or more of the channels of the third copy to one or more client devices.

### Claim 5 (depends on 4)

The method of claim 4, further comprising performing additional dispersion compensation on any of the channels being dropped to the client devices that are in the second set of channels.

### Claim 6 (depends on 1)

The method of claim 1, further comprising:
before performing dispersion compensation on the second copy, splitting the second copy into a third copy and a fourth copy, wherein the additional dispersion compensation is performed on the fourth copy;
demultiplexing the channels of the third copy;
dropping the information in one or more of the first set of channels of the third copy to one or more client devices; and
after performing dispersion compensation on the fourth copy such that dispersion compensation for the second set of channels is complete, dropping the information in one or more of the second set of channels of the fourth copy to one or more client devices.

### Claim 7

An optical dispersion compensation system operable to receive an optical signal comprising a plurality of channels, wherein the information being communicated in a first set of one or more of the channels is modulated using a first modulation technique and wherein the information being communicated in a second set of one or more of the channels is modulated using a second modulation technique, the system comprising:
a first dispersion compensation device operable to compensate for optical dispersion in the optical signal such that dispersion compensation for the first set of channels is complete for the first modulation technique and such that dispersion compensation for the second set of channels is incomplete for the second modulation technique;
a coupler operable to receive the optical signal from the first dispersion compensation device and to split the optical signal into at least a first copy of the optical signal and a second copy of the optical signal;
a second dispersion compensation device operable to receive the second copy and to perform additional dispersion compensation on the second copy such that dispersion compensation for the second set of channels is complete for the second modulation technique; and
a switch operable to terminate the second set of channels in the first copy of the optical signal and operable to terminate the first set of channels in the second copy of the optical signal.

### Claim 8 (depends on 7)

The system of claim 7, wherein:
the information being communicated in the first set of channels is communicated at 10 GB/s; and
the information being communicated in the second set of channels is communicated at 40 GB/s.

### Claim 9 (depends on 7)

The system of claim 7, wherein the switch is further operable to combine the remaining channels in the first and second copies to form a compensated optical signal.

### Claim 10 (depends on 7)

The system of claim 7, further comprising:
a second coupler device operable to split the second copy of the optical signal into a third copy and a fourth copy, wherein the second dispersion compensation device is operable to perform additional dispersion compensation on the fourth copy; and
a demultiplexer operable to demultiplex the channels of the third copy and drop the information in one or more of the channels of the third copy to one or more client devices.

### Claim 11 (depends on 10)

The system of claim 10, further comprising one or more third dispersion compensation devices each operable to perform additional dispersion compensation on a channel in the second set of channels that is being dropped to the client devices by the demultiplexer.

### Claim 12 (depends on 7)

The system of claim 7, further comprising:
a second coupler device operable to split the second copy of the optical signal into a third copy and a fourth copy, wherein the second dispersion compensation device performs additional dispersion compensation on the fourth copy;
a demultiplexer operable to demultiplex the channels of the third copy and drop the information in one or more of the channels of the third copy to one or more client devices;
a second demultiplexer operable to drop the information in one or more of the second set of channels of the fourth copy to one or more client devices after the fourth copy has been compensated by the second dispersion compensation device.