System and method for mitigating cross-saturation in optically amplified networks

• US 5,907,420 A
• Filed: 09/13/1996
• Issued: 05/25/1999
• Est. Priority Date: 09/13/1996
• Status: Expired due to Term

• Current Assignee: AT&T Corporation (AT&T, Inc.), Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Newsome, George W., Ellson, John C., Tkach, Robert William, Chraplyvy, Andrew R., Zyskind, John Lehrer
• Primary Examiner(s): PASCAL, LESLIE C
• Application Number:
  US08/713,568
• Time in Patent Office: 984 Days
• Field of Search: 359/110, 359/161, 359/174, 359/176, 359/177, 359/179, 359/124, 359/125, 359/134, 359/135
• US Class Current: 398/180
• CPC Class Codes: H04J 14/0221 Power control, e.g. to keep the total optical power constant

Abstract

A system and method of protecting all the amplifiers in a link between wavelength routing network elements of an optical network. According to the invention, an optical control channel is added before a plurality of optical amplifier, preferably the first amplifier, in a link. To prevent improper loading of downstream links, the control channel is stripped off at the next wavelength routing network element. The power of the control channel is automatically adjusted using a fast feedback circuit to hold substantially constant the total power of the signal channels and the control channel at the input of the first amplifier following the feedback loop. In this manner, channel loading of all optical amplifiers in the link is maintained substantially constant, and the incidence of error bursts, as might otherwise result when one or more channels are added or dropped due to a network fault or reconfiguration, is substantially reduced.

Claims

1. A method of operating an optical communication network including at least one optical communication path having at least one input terminal and at least one output terminal and a plurality of optical amplifiers along the at least one optical communication path, comprising:

transmitting multiplexed optical signal channels along a communication path of the network;

introducing an optical compensating channel into the at least one communication path, said optical compensating channel being at a wavelength in the gain band of the optical amplifiers;

adjusting the power level of the optical compensating channel using an optical amplifier of the plurality of optical amplifiers in response to a change in the power of at least one of the signal channels; and

removing the optical compensating channel at a next optical amplifier along the communication path to prevent improper loading downstream of the adjusting optical amplifier.

2. The method of claim 1, wherein the optical compensating channel passes through at least one optical amplifier in the communication path.

3. The method of claim 1, wherein at least some of the optical amplifiers are rare-earth doped optical fiber amplifiers.

4. The method of claim 1, wherein said adjusting step is performed within 100 μ

sec of a change in signal channel power.

5. The method of claim 1, wherein said adjusting step includes monitoring the total signal power level in all of the optical signal channels.

6. The method of claim 1, wherein wavelength division multiplexed signals are transmitted during said transmitting step.

7. The method of claim 1, wherein time-division multiplexed signals are transmitted during said transmitting step.

8. The method of claim 1, further including a step of selectively routing at least one of the optical signal channels from a first channel routing element to a second channel routing element to thereby establish the communication path between an input terminal and an output terminal of the optical communication network.

9. The method of claim 8, further including a step of selectively routing at least one of the optical signal channels from said second channel routing element to a third channel routing element.

10. The method of claim 1, further including a step of selectively routing, using at least one channel routing element, at least one of the optical signal channels to thereby establish the communication path between an input terminal and an output terminal of the optical communication network.

11. The method of claim 10, wherein the channel routing element is selected from the group consisting of fixed or reconfigurable wavelength-selective crossconnects, fixed or reconfigurable wavelength-add/drop multiplexers, fixed or reconfigurable wavelength routers, and fixed or reconfigurable wavelength-interchanging crossconnects.

12. The method of claim 1, wherein the adjusting step is performed when one or more optical signal channels are added or dropped as a result of network reconfigurations or faults.

13. An optical communication network including at least one optical communication path having at least one input terminal and at least one output terminal and a plurality of optical amplifiers along the at least one optical communication path, comprising:

means for transmitting multiplexed optical signal channels along a communication path of the network;

means for introducing an optical compensating channel into the at least one communication path, said optical compensating channel being at a wavelength in the gain band of the optical amplifiers;

means for adjusting the power level of the optical compensating channel using an optical amplifier of the plurality of optical amplifiers in response to a change in the power of at least one of the signal channels; and

means for removing the optical compensating channel at a next optical amplifier along the communication path to prevent improper loading downstream of the adjusting optical amplifier.

14. The network of claim 13, wherein the optical compensating channel passes through at least one optical amplifier in the communication path.

15. The network of claim 13, wherein at least some of the optical amplifiers are rare-earth doped optical fiber amplifiers.

16. The network of claim 13, wherein said means for adjusting is operable to adjust the power level of the optical control channel within 100 μ

sec of a change in signal channel power.

17. The network of claim 13, wherein said means for adjusting is operable to monitor the total signal power level in all of the optical signal channels.

18. The network of claim 13, wherein said means for transmitting is operable to direct wavelength division multiplexed signals over the optical communication path.

19. The network of claim 13, wherein said means for transmitting is operable to direct time-division multiplexed signals over the optical communication path.

20. The network of claim 13, further including a first channel routing element and a second channel routing element, said first channel routing element being operable to route at least one of the optical signal channels to a second channel routing element to thereby establish the communication path between an input terminal and an output terminal of the optical communication network.

21. The network of claim 20, wherein the second channel routing element is operable to selectively route at least one of the optical signal channels to a third channel routing element.

22. The network of claim 13, further including at least one channel routing element for routing at least one of the optical signal channels to thereby establish the communication path between an input terminal and an output terminal of the optical communication network.

23. The network of claim 22, wherein the channel routing element is selected from the group consisting of fixed or reconfigurable wavelength-selective crossconnects, fixed or reconfigurable wavelength-add/drop multiplexers, fixed or reconfigurable wavelength routers, and fixed or reconfigurable wavelength-interchanging crossconnects.

24. An apparatus for controlling a plurality of optical amplifiers disposed along an optical communication path, comprising:

means for transmitting multiplexed optical signal channels along a communication path of the network;

means for introducing an optical compensating channel into the at least one communication path, said optical compensating channel being at a wavelength in the gain band of the optical amplifiers; and

means for adjusting the power level of the optical compensating channel using an optical amplifier of the plurality of optical amplifiers in response to a change in the power of at least one of the signal channels; and

removing the optical compensating channel at a next optical amplifier along the communication path to prevent improper loading downstream of the adjusting optical amplifier.

25. The apparatus of claim 24, further including a channel routing element selected from the group consisting of fixed or reconfigurable wavelength-selective crossconnects, fixed or reconfigurable wavelength-add/drop multiplexers, fixed or reconfigurable wavelength routers, and fixed or reconfigurable wavelength-interchanging crossconnects.