WDM optical network and switching node with pilot tone communications

• US 6,556,321 B1
• Filed: 08/12/1999
• Issued: 04/29/2003
• 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:
  US09/372,576
• Time in Patent Office: 1,356 Days
• Field of Search: 359/119, 359/110, 359/128, 359/124, 370/222, 370/907
• 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 fiber optic wavelength division multiplexed ring, comprising:

a plurality of switching nodes,

means for generating a plurality of wavelengths organized into bands on said ring, and transmitting a like plurality of traffic channels associated with said wavelengths; and

means for transmitting maintenance channel data on at least one of said wavelengths as a pilot tone;

wherein said maintenance channel has a modulation depth such that it matches the bit error rate (BER) or waterfall curve performance of the data channel so that the system can determine the performance of the data channel by monitoring the maintenance channel data and without looking at the maintenance channel payload.

2. A network as claimed in claim 1, wherein said maintenance channel carriers feedback information about the performance of said means for generating at said destination node.

3. A network as claimed in claim 2, wherein said feedback information is used to control operation of said means for generating.

4. A network as claimed in claim 3, wherein said means for generating includes a laser emitting at said respective wavelength and said feedback information is used to control the laser extinction rate and peak power.

5. A network as claimed in claim 2, wherein said feedback information is used to initiate corrective action routines for said generating means.

6. A network as claimed in claim 2, wherein said feedback information is used to initiate stabilization routines for said generating means.

7. A network as claimed in claim 2, wherein said feedback information is used to control operation of said destination switching node.

8. A network as claimed in claim 1, wherein said maintenance channel carries at least one of switching information, maintenance information and feedback information.

9. A network as claimed in claim 8, wherein said switching information, maintenance information and feedback information are independent from the bit rate of the respective traffic channel.

10. A network as claimed in claim 8, wherein said switching information, maintenance information and feedback information are independent from the protocol of the respective traffic channel.

11. A fiber optic wavelength division multiplexed ring comprising:

a plurality of switching nodes,

means for generating a plurality of wavelengths organized into bands on said ring, and transmitting a like plurality of traffic channels associated with said wavelengths; and

means for transmitting maintenance channel data on at least one of said wavelengths as a pilot tone;

wherein said maintenance channel has a modulation depth, such that the system can determine the performance of the respective traffic channel by monitoring the bit error rate (BER) or waterfall curve performance of the maintenance channel data and without looking at the maintenance data.

12. A fiber optic wavelength division multiplexed ring comprising:

a plurality of switching nodes,

means for generating a plurality of wavelengths organized into bands on said ring, and transmitting a like plurality of traffic channels associated with said wavelengths; and

means for transmitting maintenance channel data on at least one of said wavelengths as a pilot tone;

wherein said maintenance channel has a known modulation depth with respect to said respective traffic channel, such that the system can determine the performance of the respective traffic channel by monitoring the bit error rate (BER) or waterfall curve performance of the maintenance channel data and without looking at the maintenance data.