WDM optical network with passive pass-through at each node

• US 6,493,117 B1
• Filed: 11/19/1999
• Issued: 12/10/2002
• Est. Priority Date: 08/27/1997
• Status: Expired due to Term

• Current Assignee: Ciena Corporation
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Milton, David, Liu, Kexing, Valis, Tomas, Pigeon, Michel, Totti, Gino
• Primary Examiner(s): NEGASH, KINFE MICHAEL
• Application Number:
  US09/443,329
• Time in Patent Office: 1,117 Days
• Field of Search: 319/119, 319/124-125, 319/127, 319/130, 385/24
• US Class Current: 398/49
• CPC Class Codes: H04J 14/0206 Express channels arrangements
• CPC Class Codes: H04J 14/0209 Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0213 Groups of channels or wave bands arrangements
• CPC Class Codes: H04J 14/0226 Fixed carrier allocation, e.g. according to service
• CPC Class Codes: H04J 14/0227 Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
• CPC Class Codes: H04J 14/0241 Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
• CPC Class Codes: H04J 14/0246 using one wavelength per ONU
• CPC Class Codes: H04J 14/025 using one wavelength per ONU, e.g. for transmissions from-ONU-to-OLT or from-ONU-to-ONU
• CPC Class Codes: H04J 14/028 WDM bus architectures
• CPC Class Codes: H04J 14/0282 WDM tree architectures
• CPC Class Codes: H04J 14/0283 WDM ring architectures
• CPC Class Codes: H04J 14/0284 WDM mesh architectures
• CPC Class Codes: H04J 14/0289 Optical multiplex section protection
• CPC Class Codes: H04J 14/0291 Shared protection at the optical multiplex section (1:1, n:m)
• CPC Class Codes: H04J 14/0298 with sub-carrier multiplexing [SCM]
• CPC Class Codes: H04Q 11/0062 Network aspects

Abstract

A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Claims

1. A communications network employing wavelength division multiplexing comprising:

a plurality of nodes;

an optical transmission medium interconnecting said nodes in a bi-directional ring configuration; and

an interface at each node for receiving an input multi-band optical signal, dropping a drop band associated with said node, passively forwarding other bands, and combining an add band carrying traffic for another node with said other bands to provide an output multi-band optical signal,

wherein each band comprises a plurality of optical signals travelling over corresponding transmission channels at distinct wavelengths, and wherein each band is shared between a pair of nodes in said network such that bi-directional communications may be established between each said pair of nodes without the active intervention of any intervening nodes.

2. A communications network as claimed in claim 1, wherein said interface includes a band demultiplexer for separating said input multi-band optical signal into said drop band and said other bands.

3. A communication network as claimed in claim 1, wherein said band demultiplexer is an optical band demultiplexer.

4. A communications network as claimed in claim 1, wherein said interface comprises a channel demultiplexer for distributing the channels within said drop band to a respective user.

5. A communications network as claimed in claim 4, wherein said channel demultiplexer is an optical channel demultiplexer.

6. A communications network as claimed in claim 1, wherein said interface includes a band multiplexer for combining said other bands with said add band to provide said output multi-band signal.

7. A communication network as claimed in claim 6, wherein said band multiplexer is an optical band multiplexer.

8. A communications network as claimed in claim 1, wherein said interface comprises a channel multiplexer for combining a plurality of channels received from one or more users into said add band.

9. A communications network as claimed in claim 8, wherein said channel multiplexer is an optical channel multiplexer.

10. A communication network as claimed in claim 1, wherein the distinct wavelengths of the optical signals of said add band correspond to the distinct wavelengths of the optical signals of said drop band.

11. A method of establishing communication over an optical network employing wavelength division multiplexing and having a plurality of network nodes interconnected by an optical transmission medium capable of carrying a plurality of wavelengths organized into bands, comprising the steps of:

sending traffic from a local node destined for a remote node in a band associated with the local node and the remote node;

passively forwarding said band at any intervening nodes; and

dropping said band at said remote node to extract said traffic destined therefore,

wherein said network nodes are physically arranged in a bidirectional ring configuration, and wherein said band comprises a plurality of optical channels at distinct wavelengths, such that one direction of a bi-directional communications link is provided between said local node and said remote node without the active intervention of any intervening nodes.

12. A method as claimed in claim 11, further comprising the step of adding said band at said local node for transmission over said network to said remote node dropping said band.

13. A method as claimed in claim 12, further comprising the step of performing wavelength switching at said remote node to transfer data between bands.

14. A traffic node of an optical WDM network comprising:

a band demultiplexer for receiving an input multi-band optical signal from the network and separating therefrom a drop multichannel band signal for local use; and

a channel demultiplexer for receiving said drop multichannel band signal and providing each channel carried within said drop multichannel band signal to a respective local user.

15. A traffic node as claimed in claim 14, wherein said band demultiplexer is an optical band demultiplexer.

16. A traffic node as claimed in claim 15, further comprising means for converting said drop multichannel band signal to an electrical format.

17. A traffic node as claimed in claim 14, wherein said drop multichannel band signal comprises at least two local optical signals at distinct wavelengths.

18. A traffic node as claimed in claim 14, wherein said band demultiplexer passes through unchanged other multichannel band signals than said drop multichannel band signal.

19. A traffic node as claimed in claim 18, wherein said other multichannel band signals comprise at least two passthrough signals at distinct wavelengths.

20. A traffic node as claimed in claim 18, further comprising a band multiplexer for receiving said other multichannel band signals and an add multichannel band signal, combining same into an output multi-band optical signal, and launching same over said network.

21. A traffic node of an optical WDM network comprising:

a band multiplexer for receiving a passthrough multi-band optical signal and an add multi-channel band signal, combining same into an output multi-band optical signal, and launching same over said network; and

a channel multiplexer for combining a plurality of local channels into said add multichannel band signal and providing same to said band multiplexer.

22. A traffic node as claimed in claim 21, wherein said band multiplexer is an optical band multiplexer.

23. A traffic node as claimed in claim 21, wherein said add multichannel band signal comprises at least two local wavelengths.

24. A traffic node as claimed in claim 21, wherein said channel multiplexer combines said local wavelengths into said add multichannel band in an electrical format, and converts same to an optical format.

25. A communications network employing wavelength division multiplexing, comprising:

a plurality of nodes;

an optical transmission medium interconnecting said nodes in a bi-directional ring configuration, said medium being capable of carrying a plurality of optical signals organized into distinct bands of wavelength channels, each distinct band of wavelength channels being associated with a respective pair of nodes; and

an interface at each node operable;

to add traffic over at least one wavelength channel in at least one band associated with a pair of nodes including said node;

to drop traffic from at least one wavelength channel in at least one band associated with said pair of nodes including said node; and

to passively forward wavelength channels in all bands associated with other pairs of nodes not including said node;

such that bi-directional communications may be established between said pair of nodes including said node without the active intervention of any intervening nodes.

26. A node for an optical communications network employing wavelength division multiplexing, the node comprising:

a band demultiplexer operable to separate an input multi-band optical signal comprising a plurality of wavelength band signals into at least one drop band optical signal and at least one forward band optical signal, each wavelength band signal comprising a plurality of wavelength channel signals at distinct wavelengths within a respective wavelength band, each drop band optical signal comprising a plurality of wavelength channel signals in a respective wavelength band, and each forward band optical signal comprising a plurality of wavelength channel signals in at least one wavelength band;

a channel demultiplexer operable to separate at least one drop wavelength channel signal from the drop band optical signal; and

a multiplexer operable to combine the forward band optical signal with at least one add wavelength channel signal to form an output multi-band optical signal.

27. A node as defined in claim 26, wherein the multiplexer comprises:

a channel multiplexer operable to combine add wavelength channel signals to form an add band optical signal; and

a band multiplexer operable to combine at least one add band optical signal with the forward band optical signal to form said output multi-band optical signal.

28. A node as defined in claim 26, further comprising a cross-connect coupled to the channel demultiplexer and the multiplexer, and operable to cross-connect drop wavelength channel signals and add wavelength channel signals.

29. A node as defined in claim 28, wherein the cross-connect is an optical cross-connect.

30. A node for an optical communications network employing wavelength division multiplexing, the node comprising:

a band demultiplexer operable to separate an input multi-band optical signal comprising a plurality of wavelength band signals into at least one drop band optical signal and at least one forward optical signal, each wavelength band signal comprising a plurality of wavelength channel signals at distinct wavelengths within a respective wavelength band, each drop band optical signal comprising a plurality of wavelength channel signals in a respective wavelength band, and each forward optical signal comprising a plurality of wavelength channel signals in at least one wavelength band;

a channel demultiplexer operable to separate at least one drop wavelength channel signal from the drop band optical signal;

a multiplexer operable to combine the forward optical signal with at least one add wavelength channel signal to form a node output optical signal; and

an electrical cross-connect coupled to the channel demultiplexer and the multiplexer via optical transponders.