WDM optical network with passive pass-through at each node

• US 6,775,479 B2
• Filed: 12/20/2002
• Issued: 08/10/2004
• Est. Priority Date: 08/27/1997
• Status: Expired due to Term

• Current Assignee: Ciena Corporation
• Original Assignee: Nortel Networks Corporation
• Inventors: Milton, David, Liu, Kexing, Valis, Tomas, Pigeon, Michel, Totti, Gino
• Primary Examiner(s): NEGASH, KINFE MICHAEL
• Application Number:
  US10/323,683
• Publication Number:
  US 20030123881A1
• Time in Patent Office: 599 Days
• Field of Search: 398/50, 398/56, 398/59, 398/79, 398/68, 398/82-85, 385/24
• US Class Current: 398/79
• 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 method of operating a node of a communications network in which pairs of nodes are associated with distinct bands of optical channels used for communication between said pairs of nodes, each band of optical channels comprising a plurality of distinct optical channels operating at respective distinct wavelengths, the method comprising:

separating a selected band of optical channels from non-selected bands of optical channels and passively forwarding the non-selected bands of optical channels, the non-selected bands being separated from the selected band by at least one optical channel which is not used for communication; and

combining a band of optical channels with the passively forwarded non-selected bands of optical channels.

2. A method as defined in claim 1, wherein said distinct wavelengths are selected according to a predetermined grid of wavelength channels which are spaced uniformly in frequency, and adjacent bands are separated by at least one wavelength channel on said predetermined grid of wavelength channels which is not used for communicating information.

3. A method as defined in claim 2, wherein said adjacent bands are separated by at least two wavelength channels on said predetermined grid which are not used for communicating information.

4. A method as defined in claim 1, further comprising:

further separating the separated band into individual optical channels; and

combining optical channels to assemble the band of optical channels which is combined by the band multiplexer with passively forwarded non-selected bands of optical channels.

5. A method as defined in claim 4, further comprising connecting a cross-connect switch to at least one of the channel demultiplexer and the channel multiplexer.

6. A method as defined in claim 5, further comprising connecting an opto-electronic converter between the cross-connect switch and the at least one of the channel demultiplexer and the channel multiplexer, the cross-connect switch being an electrical switch.

7. A method for operating a node of a communications network in which pairs of nodes of the network are associated with distinct bands of optical channels used for communication between said pairs of nodes, each band of optical channels comprising a plurality of distinct optical channels at respective distinct wavelengths, said distinct wavelengths being selected according to a predetermined grid of wavelength channels which are spaced uniformly in frequency, the method comprising:

separating a selected band of optical channels from non-selected bands of optical channels and passively forwarding the non-selected bands of optical channels, the separated band being spaced from the non-selected bands by at least one wavelength channel on said predetermined grid of wavelength channels which is not used for transmission; and

combining a band of optical channels with the passively forwarded non-selected bands of optical channels.

8. A method as defined in claim 7, wherein said separated band is spaced from the non-selected bands by at least two wavelength channels on said predetermined grid which are not used for transmission.