Optical ring network with selective signal regeneration and wavelength conversion

• US 20040240884A1
• Filed: 05/29/2003
• Published: 12/02/2004
• Est. Priority Date: 05/29/2003
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Kinoshita, Susumu, Gumaste, Ashwin Anil
• Granted Patent: US 7,321,729 B2
• Time in Patent Office: Days
• US Class Current: 398/59
• CPC Class Codes: H04J 14/0204 Broadcast and select arrangements, e.g. with an optical splitter at the input before adding or dropping
• CPC Class Codes: H04J 14/0205 Select and combine arrangements, e.g. with an optical combiner at the output after adding or dropping
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0283 WDM ring architectures
• CPC Class Codes: H04J 14/0291 Shared protection at the optical multiplex section (1:1, n:m)
• CPC Class Codes: H04J 14/0294 Dedicated protection at the optical channel (1+1)
• CPC Class Codes: H04J 14/0295 Shared protection at the optical channel (1:1, n:m)

Abstract

An optical network includes an optical ring having a plurality of subnets. The subnets each include one or more add/drop nodes that are coupled to the optical ring and that passively add and drop traffic to and from the optical ring in one or more wavelengths. The optical network also includes a plurality of gateway nodes that are each coupled to the optical ring at a boundary between neighboring subnets. Each gateway node forwards a first copy of a received optical signal to a multiplexer/demultiplexer unit of the gateway node, which selectively forwards or terminates the traffic in each wavelength of the first copy. The gateway nodes also forward a second copy of the received optical signal to a regeneration element. The gateway nodes selectively forward or terminate the traffic in each wavelength of the first copy at the multiplexer/demultiplexer unit. Moreover the gateway nodes selectively perform one of the following on the traffic in each wavelength of the second copy at the regeneration element: terminate the traffic, forward the traffic after regenerating the traffic, or forward the traffic after regenerating and converting the wavelength of the traffic.

Claims

1. An optical network, comprising:

an optical ring including a plurality of subnets;

the subnets each comprising one or more add/drop nodes coupled to the optical ring and operable to passively add and drop traffic to and from the optical ring in one or more wavelengths;

a plurality of gateway nodes, each gateway node coupled to the optical ring at a boundary between neighboring subnets, each gateway node operable to;

forward a first copy of a received optical signal to a multiplexer/demultiplexer unit of the gateway node that is operable to selectively forward or terminate the traffic in each wavelength of the received optical signal;

forward a second copy of the received optical signal to a regeneration element of the gateway node, the second copy thus bypassing the multiplexer/demultiplexer unit;

selectively forward or terminate the traffic in each wavelength of the first copy at the multiplexer/demultiplexer unit, the forwarded traffic not being regenerated; and

selectively perform one of the following on the traffic in each wavelength of the second copy at the regeneration element;

terminate the traffic, forward the traffic after regenerating the traffic, or forward the traffic after regenerating and converting the wavelength of the traffic.

2. The optical network of claim 1, wherein, within each subnet, each add/drop node is operable to add and drop traffic independent of the channel spacing of the traffic.

3. The optical network of claim 1, wherein each add/drop node comprises a single optical coupler operable to passively add and drop traffic.

4. The optical network of claim 1, wherein the gateway node comprises:

a first optical coupler operable to receive ingress traffic on the optical ring, to forward the first copy of the received optical signal to the multiplexer/demultiplexer unit, and to forward the second copy of the received optical signal to the regeneration element; and

a second optical coupler operable to receive the traffic forwarded by the multiplexer/demultiplexer unit and the regeneration element, and further operable to combine the received traffic such that the combined signal is forwarded on the optical ring.

5. The optical network of claim 4, wherein the signal regeneration element comprises:

a splitter operable to make a plurality of copies of the second copy received from the first optical coupler;

one or more filters each operable to receive one of the plurality of copies of the second copy and to forward one or more wavelengths of the associated copy;

one or more transponders operable to receive each filtered wavelength from the one or more filters and to regenerate the signal in that wavelength; and

a combiner operable to receive and combine the regenerated signals and to forward the combined signals to the second optical coupler.

6. The optical network of claim 5, wherein one or more of the transponders are further operable to convert the wavelength of the signal associated with a filtered wavelength that is received at the transponder.

7. The optical network of claim 1, wherein the multiplexer/demultiplexer unit comprises:

a demultiplexer operable to demultiplex the second copy of the received optical signal into a plurality of constituent wavelengths;

a switch operable to selectively forward or terminate each wavelength; and

a multiplexer operable to combine the forwarded wavelengths.

8. The optical network of claim 1, wherein each wavelength that is regenerated by the signal regeneration element is terminated by the multiplexer/demultiplexer unit.

9. The optical network of claim 1, wherein one or more of the gateway nodes are further operable to drop the traffic in one or more wavelengths of the second copy of the received optical signal to one or more appropriate clients.

10. The optical network of claim 1, wherein one or more of the gateway nodes are further operable to add traffic from one or more clients to the optical ring.

11. An optical gateway node operable to be coupled to an optical ring of an optical network, the gateway comprising:

a first optical coupler operable to receive ingress traffic on the optical ring and to forward a first and a second copy of the ingress traffic;

a multiplexer/demultiplexer unit operable to receive the first copy of the ingress traffic from the first optical coupler, the multiplexer/demultiplexer unit comprising;

a demultiplexer operable to demultiplex the first copy of the ingress traffic into a plurality of constituent wavelengths;

a switch operable to selectively forward or terminate each wavelength; and

a multiplexer operable to multiplex the forwarded wavelengths;

a signal regeneration element operable to receive the second copy of the ingress traffic from the first optical coupler and to selectively regenerate a signal in one or more constituent wavelengths of the ingress traffic; and

a second optical coupler operable to;

receive the regenerated signals in one or more wavelengths;

receive the multiplexed forwarded wavelengths from the multiplexer; and

combine the multiplexed forwarded wavelengths with the regenerated wavelengths received from the signal regeneration element such that the combined signal is forwarded on the optical ring.

12. The optical gateway node of claim 11, wherein the signal regeneration element is further operable to convert the wavelength of one or more of the regenerated signals.

13. The optical gateway node of claim 11, wherein the signal regeneration element comprises:

a splitter operable to make a plurality of copies of the second copy received from the first optical coupler;

one or more filters each operable to receive one of the plurality of copies of the second copy and to forward one or more wavelengths of the associated copy;

one or more transponders operable to receive each filtered wavelength from the one or more filters and to regenerate the signal in that wavelength; and

a combiner operable to receive and combine the regenerated signals and to forward the combined signals to the second optical coupler.

14. The optical gateway node of claim 13, wherein one or more of the transponders are further operable to convert the wavelength of the signal associated with a filtered wavelength that is received at the transponder.

15. The optical gateway node of claim 11, wherein each wavelength that is regenerated by the signal regeneration element is terminated by the multiplexer/demultiplexer unit.

16. The optical gateway node of claim 11, wherein the signal regeneration element is further operable to drop the signal in one or more wavelengths of the second copy of the ingress traffic to one or more appropriate clients of the optical gateway node.

17. The optical gateway node of claim 11, wherein the second optical coupler is further operable to:

receive add traffic from one or more clients of the optical gateway node; and

combine the add traffic with the multiplexed forwarded wavelengths and the regenerated wavelengths received from the signal regeneration element such that the combined signal is forwarded on the optical ring.

18. A method of providing a gateway function in an optical ring of an optical network, the method comprising:

receiving ingress traffic from the optical ring;

passively forwarding a first and a second copy of the ingress traffic, the second copy not being demultiplexed;

demultiplexing the first copy of the ingress traffic into one or more constituent wavelengths;

terminating the signal in at least one constituent wavelength of the first copy of the ingress traffic;

selectively regenerating a signal in one or more constituent wavelengths of the second copy of the ingress traffic;

receiving the regenerated signals in one or more wavelengths; and

adding the regenerated signals to the optical ring.

19. The method of claim 18, further comprising converting the wavelength of one or more of the regenerated signals.

20. The method of claim 18, further comprising:

selectively forwarding or terminating each demultiplexed wavelength of the first copy of the ingress signal; and

multiplexing the forwarded wavelengths.

21. The method of claim 20, further comprising:

receiving the multiplexed forwarded wavelengths; and

combining the multiplexed forwarded wavelengths with the received regenerated signals.

22. The method of claim 20, wherein each wavelength that is regenerated is terminated after being demultiplexed.

23. A method of protection switching traffic carried on an optical ring network having a first optical ring and a second optical ring carrying traffic in opposite directions in the optical ring network, the network comprising a plurality of passive add/drop nodes without in-line rejection filters and one more gateways coupled to each of the optical rings, the method comprising:

transmitting protected traffic in one or more wavelengths in the first optical ring;

transmitting preemtable traffic in one or more wavelengths in the second optical ring;

detecting an interruption in a working path of a protected traffic stream, the working path traversing at least a portion of a first subnet;

reconfiguring the gateways to create a protection path, the protection path traversing at least a portion of a second subnet;

terminating any preemtable traffic along the protection path;

transmitting protection traffic in the protection path to the destination node of the protected traffic stream; and

converting the wavelength of protection traffic at one or more of the gateways.

24. The method of claim 23, further comprising:

transmitting protected traffic in one or more different wavelengths in the second optical ring than the wavelengths of the preemtable traffic in the second optical ring; and

transmitting preemtable traffic in one or more different wavelengths in the first optical ring than the wavelengths of the protected traffic in the first optical ring.

25. The method of claim 23, further comprising reverting the network to a pre-interruption state in response to at least a correction of the interruption.

26. The method of claim 23, wherein the protected traffic stream comprises higher priority traffic than any existing traffic terminated along the protection path.