WDM optical network with passive pass-through at each node

• US 6,892,032 B2
• Filed: 12/20/2002
• Issued: 05/10/2005
• 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, Valis, Tomas, Pigeon, Michel, Totti, Gino, Liu, Kexing
• Primary Examiner(s): NEGASH, KINFE MICHAEL
• Application Number:
  US10/323,680
• Publication Number:
  US 20030215238A1
• Time in Patent Office: 872 Days
• Field of Search: 398/3, 398/50, 398/56, 398/59, 398/68, 398 83- 85, 398/91, 398/168, 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 for communicating between nodes of a communications network employing wavelength division multiplexing, comprising:

defining bands of optical channels for communication between respective pairs of network nodes, each band of optical channels comprising a plurality of distinct optical channels at respective distinct wavelengths, said bands being separated by at least one wavelength channel which is not used for communicating information;

allocating a selected bend of optical channels for communication between a specific pair of network nodes;

separating the selected band of optical channels from non-selected bands of optical channels at each node of the pair of nodes, and passively forwarding the non-selected bands of optical channels at each node of the pair of nodes;

and passively forwarding the selected band at any node of the network located between the specific pair of nodes.

2. A method an 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 separating the separated band of optical channels into individual optical channels.

5. A method as defined in claim 4, further comprising applying separated optical channels to a cross-connect switch.

6. A method as defined in claim 5, further comprising converting the optical channels to electrical signals before they are applied to the cross-connect switch, the cross-connect switch being an electrical switch.

7. A method as defined in claim 5, wherein the step of applying the separated optical channels to the cross-connect switch comprises applying the separated optical channel to an optical cross-connect switch.

8. A method for communicating between nodes of a communications network employing wavelength division multiplexing, comprising:

defining bands of optical channels for communication between respective pairs of network 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, and adjacent bands are separated by at least one wavelength channel on said predetermined grid of wavelength channels which is not used for transmission;

allocating a selected band of optical channels for communication between a specific pair of network nodes;

separating the selected band of optical channels from non-selected bands of optical channels at each node of the pair of nodes, and passively forwarding the non-selected bands of optical channels at each node of the pair of nodes;

and passively forwarding the selected band at any node of the network located between the specific pair of nodes.

9. A method for communicating between nodes of a communications network as defined in claim 8, wherein said adjacent bands are separated by at least two wavelength channels on said predetermined grid which are not used for transmission.