Dense WDM add/drop multiplexer

• US 6,459,516 B1
• Filed: 07/27/2000
• Issued: 10/01/2002
• Est. Priority Date: 09/11/1997
• Status: Expired due to Fees

• Current Assignee: Ciena Corporation
• Original Assignee: Ciena Corporation
• Inventors: Archambault, Jean-Luc, Mizrahi, Victor
• Primary Examiner(s): Pascal, Leslie
• Assistant Examiner(s): Phan, Hanh
• Application Number:
  US09/627,899
• Time in Patent Office: 796 Days
• Field of Search: 359/127, 359/130, 359/129, 359/131
• US Class Current: 398/82
• CPC Class Codes: G02B 6/12019 characterised by the optical interconnection to or from the AWG devices, e.g. integration or coupling with lasers or photodiodes coupling integrated waveguide to fibre G02B6/30, to optoelectronic element G02B6/42; monolithic integration of integrated waveguides with other optical elements G02B6/12004
• CPC Class Codes: G02B 6/29317 Light guides of the optical fibre type
• CPC Class Codes: G02B 6/29355 Cascade arrangement of interferometers
• CPC Class Codes: G02B 6/29361 Interference filters, e.g. multilayer coatings, thin film filters, dichroic splitters or mirrors based on multilayers, WDM filters
• CPC Class Codes: G02B 6/2938 for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• 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 14/0209 Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers
• CPC Class Codes: H04J 14/0213 Groups of channels or wave bands arrangements

Abstract

An optical add/drop multiplexer (OADM) is provided wherein input optical channels are supplied on first and second optical fibers, e.g. via an optical splitter. Low loss interference filters, for example, coupled to the first and second optical fibers, select respective groups or bands of channels. Selected groups of channels to be dropped by the OADM may be demultiplexed with sub-demultiplexers into individual channels. Groups of express channels are supplied to associated filters or gratings to ensure that the channel groups selected from the first and second optical fibers to do not contain undesired channels. Channels to be added by the OADM are multiplexed with sub-multiplexers into channel groups corresponding to the dropped channel groups. The added channel groups and the express channel groups are combined on a single output fiber.

Claims

1. An optical device, comprising:

an optical splitter having an input and first and second outputs, said input for coupling to an input optical path, said input optical path carrying a plurality of optical channels, each said optical channels having a respective wavelength, said first output being coupled to a first output optical path, and said second output being coupled to a second output optical path, said first and second output optical paths carrying said plurality of optical channels;

a first plurality of optical filtering elements coupled to said first output optical path, each of said first plurality of optical filtering elements respectively selecting a corresponding one of a plurality of first groups of said plurality of optical channels and associated undesired channels; and

a second plurality of optical filtering elements coupled to said second output optical path, each of said second plurality of optical filtering elements respectively selecting a corresponding one of a plurality of second groups of said plurality of optical channels and associated undesired channels, said plurality of first groups of optical channels being different than said plurality of second groups of optical channels;

at least one filter coupled to an associated one of said first and second plurality of optical filtering elements for receiving one of said first and second groups of optical channels and said undesired channels associated with said one of said first and second groups of optical channels, said filter supplying said one of said first and second groups of optical channels as an express channel group while substantially rejecting said undesired channels associated with said one of said first and second groups of optical channels; and

a multiplexer receiving said express channel group and at least one added channel group on associated inputs, said added channel group being different from said express channel group, said multiplexer supplying an output comprising said express channel group and said added channel group in an aggregated form on an output optical communication path.

2. An optical device in accordance with claim 1, where said first and second output optical paths are con figured to accommodate additional filtering elements.

3. An optical device in accordance with claim 1, wherein said first and second pluralities of filtering elements comprise interference filters.

4. An optical device in accordance with claim 1, further comprising an optical amplifier coupled to said input of said optical splitter.

5. An optical device in accordance with claim 1, further comprising:

at least one sub-demultiplexer coupled to an optical filtering element, said optical filtering element being one of said first plurality of optical filtering elements, said sub-demultiplexer having a plurality of outputs each presenting a respective drop channel associated with optical filtering element.

6. An optical device in accordance wit claim 1, further comprising:

at least one sub-multiplexer having a plurality of input each configured to receive a respective add channel associated with one of said add channel groups, said sub-multiplexer supplying an output comprising said one of said add channel groups.

7. An optical device in accordance with claim 1, wherein said multiplexer comprises:

a first plurality of optical filtering elements, each of said first plurality of optical filtering elements being coupled to a respective one of a first group of said associated inputs, said first plurality of optical filtering elements supplying channel groups received on said first group of said associated inputs in an aggregated form as a first aggregate channel group on a first aggregate optical path;

a second plurality of optical filtering elements, each of said second plurality of optical filtering elements being coupled to a respective one of a second group of said associated inputs, said second plurality of optical filtering elements supplying channel groups received on said second group of said associated inputs in an aggregated form as a second aggregate channel group on a second aggregate optical path; and

an optical coupler having first and second inputs and an output, said first input being coupled to said first aggregate optical path and said second input coupled to said second aggregate optical path, said coupler supplying said first aggregate channel group and said second aggregate channel group in an aggregated form on said single output fiber.

8. An optical device in accordance with claim 7, wherein said first and second

aggregate optical paths are configured to accommodate additional filtering elements.

9. An optical device in accordance with claim 7, wherein said first and second pluralities of filtering elements comprise interference filters.

10. An optical device, comprising:

first and second optical paths carrying a plurality of optical channels;

a first plurality of optical filtering elements coupled to said first optical path, each of said first plurality of optical filtering elements respectively selecting a corresponding one of a plurality of first groups of said plurality of optical channels and associated undesired channels; and

a second plurality of optical filtering elements coupled to said second optical path, each of said second plurality of optical filtering elements respectively selecting a corresponding one of a plurality of second groups of said plurality of optical channels and associated undesired channels, said plurality of first groups of optical channels being different than said plurality of second groups of optical channels;

at least one filter coupled to an associated one of said first and second plurality of optical filtering elements for receiving one of said first and second groups of optical channels and said undesired channels associated with said one of said first and second groups of optical channels, said filter supplying said one of said first and second groups of optical channels as an express channel group while substantially rejecting said undesired channels associated with said one of said first and second groups of optical channels; and

a multiplexer receiving said express channel group and at least one added channel group on associated inputs, said added channel group being different from said express channel group, said multiplexer supplying an output comprising said express channel group and said added channel group in an aggregated form on a single optical output fiber.

11. An optical device in accordance with claim 10, wherein said first and second optical paths are configured to accommodate additional filtering elements.

12. An optical device in accordance with claim 10, wherein said first and second pluralities of filtering elements comprise interference filters.

13. An optical device in accordance with claim 10, further comprising:

at least one sub-demultiplexer coupled to an associated one of said first and second plurality of optical filtering elements, said sub-demultiplexer having a plurality of outputs each presenting a respective drop channel associated with a corresponding one of said first and second groups of said plurality of channels.

14. An optical device in accordance with claim 10, further comprising:

at least one sub-demultiplexer coupled to an optical filtering element, said optical filtering element being one of said first plurality of optical filtering elements, said sub-demultiplexer having a plurality of outputs each presenting a respective drop channel associated with optical filtering element.

15. An optical device in accordance with claim 10, wherein said multiplexer comprises:

a first plurality of optical filtering elements, each of said first plurality of optical filtering elements being coupled to a respective one of a first group of said associated inputs, said first plurality of optical filtering elements supplying channel groups received on said first group of said associated inputs in an aggregated form as a first aggregate channel group on a first aggregate optical path;

a second plurality of optical filtering elements, each of said second plurality of optical filtering elements being coupled to a respective one of a second group of said associated inputs, said second plurality of optical filtering elements supplying channel groups received on said second group of said associated inputs in an aggregated form as a second aggregate channel group on a second aggregate optical path; and

an optical coupler having first and second inputs and an output, said first input being coupled to said first aggregate optical path and said second input coupled to said second aggregate optical path, said coupler supplying said first aggregate channel group and said second aggregate channel group in an aggregated form on said single output fiber.

16. An optical device in accordance with claim 15, wherein said first and second aggregate optical paths are configured to accommodate additional filtering elements.

17. An optical device in accordance with claim 15, wherein said first and second pluralities of filtering elements comprise interference filters.

18. An optical add/drop multiplexer, comprising:

an optical splitter having an input and first and second outputs, said input for coupling to an input optical path, said input optical path carrying a plurality of optical channels, each said optical channels having a respective wavelength, said first output being coupled to a first output optical path, and said second output being coupled to a second output optical path, said first and second output optical paths carrying said plurality of optical channels;

a first plurality of optical filtering elements coupled to said first output optical path, each of said first plurality of optical filtering elements respectively a corresponding one of a plurality of selecting first groups of said plurality of optical channels and associated undesired channels;

a second plurality of optical filtering elements coupled to said second output optical path, each of said second plurality of optical filtering elements respectively selecting a corresponding one of a plurality of second groups of said plurality of optical channels and associated undesired channels, said plurality of first groups of optical channels being different than said plurality of second groups of optical channels;

at least one filter coupled to an associated one of said first and second plurality of optical filtering elements for receiving one of said first and second groups of optical channels and said undesired channels associated with said one of said first and second groups of optical channels, said filter supplying said one of said first and second groups of optical channels as an express channel group while reducing said undesired channels associated with said one of said first and second groups of optical channels; and

a multiplexer receiving said express channel group and at least one added channel group on associated inputs, said added channel group being different from said express channel group, said multiplexer supplying an output comprising said express channel group and said added channel group in an aggregated form on a single optical output fiber.

19. An optical add/drop multiplexer accordance with claim 18, further comprising:

at least one sub-demultiplexer coupled to an optical filtering element, said optical filtering element being one of said first plurality of optical filtering elements, said sub-demultiplexer having a plurality of outputs each presenting a respective drop channel associated with optical filtering element.

20. An optical device, comprising:

an optical demultiplexer having an input being configured to receive a plurality of optical signals, each at a respective one of a plurality of wavelengths, and a plurality of outputs, each of which supplying a corresponding one of a plurality of subgroups of said plurality of optical signals, and associated undesired channels;

a filter coupled to receive one of said plurality of subgroups of said plurality of optical signals, said filter passing said one of said plurality of subgroups of said plurality of optical signals and rejecting undesired channels associated with said one of said plurality of subgroups of said plurality of optical signals; and

an optical multiplexer coupled to said filter, said multiplexer having a first input being configured to receive an added optical signal subgroup and a second input coupled to receive said one of said plurality of subgroups of said plurality of optical signals, and an output supplying said added optical signal subgroup and said one of said plurality of subgroups of said plurality of optical signals.

21. An optical device in accordance with claim 20, wherein said filter includes a Bragg grating.

22. An optical device in accordance with claim 20, further comprising a variable optical attenuator coupled to said one of said plurality of outputs of said optical demultiplexer.

23. An optical device in accordance with claim 22, further comprising an optical amplifier coupled to optical demultiplexer, said variable optical attenuator being adjusted to provide an attenuation such that each optical signal within said subgroup of said plurality of optical signals has substantially uniform optical power at an output of said optical multiplexer.

24. An optical device in accordance with claim 20, further comprising a dispersion compensating element coupled to one of said plurality of outputs of said optical demultiplexer.

25. An optical device comprising:

an optical demultiplexer having an input being configured to receive a plurality of optical signals, each at a respective one of a plurality of wavelengths, and a plurality of outputs, each of which supplying a corresponding one of a plurality of subgroups of said plurality of optical signals, and associated undesired channels;

a plurality of optical switches, each of which being coupled to a respective one of said plurality of outputs of said optical demultiplexer, each of said plurality of optical switches being configured to selectively drop a corresponding one of said subgroups of said plurality of optical signals; and

a plurality of filters, each of which being coupled to a respective one of said plurality of optical switches, each of said plurality of filters passing a respective one of said plurality of subgroups of said plurality of optical signals and rejecting undesired channels associated with said respective one of said plurality of subgroups of said plurality of optical signals.

26. An optical device in accordance with claim 25, further comprising:

an optical multiplexer having a plurality of inputs, each of which being coupled to a respective one of said plurality of filters, and an output for supplying combined optical signals.