Dense WDM optical multiplexer and demultiplexer

• US 6,567,196 B1
• Filed: 03/22/1999
• Issued: 05/20/2003
• Est. Priority Date: 03/22/1999
• Status: Expired due to Term

• Current Assignee: Ciena Corporation
• Original Assignee: Ciena Corporation
• Inventors: Archambault, Jean-Luc
• Primary Examiner(s): Pascal, Leslie
• Assistant Examiner(s): Phan, Hanh
• Application Number:
  US09/274,063
• Time in Patent Office: 1,520 Days
• Field of Search: 359/124, 359/127, 359/161, 359/130, 359/154, 359/133, 359/173, 359/174, 359/176, 359/177, 359/179, 359/341, 359/337, 385/24, 385/16, 385/140, 385/17, 385/37
• US Class Current: 398/79
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04J 14/0221 Power control, e.g. to keep the total optical power constant

Abstract

In accordance with the present invention, optical channels to be demultiplexed are supplied to first and second optical fibers via an optical splitter. Low loss interference filters, for example, coupled to the first and second optical fibers, select respective groups of channels. Each group of channels is next demultiplexed with sub-demultiplexers into individual channels, each of which is then sensed with a corresponding photodetector. Although the optical splitter introduces an optical power loss at the input to the demultiplexer, the interference filters and sub-demultiplexers create little additional loss. As a result, the total power loss associated with the present invention is significantly less than that obtained with a conventional n channel demultiplexer based on a 1×n splitter. Accordingly, large numbers of channels, e.g., in excess of forty can be readily demultiplexed and detected. Optical multiplexers are further disclosed for supplying relatively large number of channels to a single optical fiber.

Claims

1. An optical device comprising:

a first optical combiner receiving a first plurality of optical signals, each of which being at a respective one of a first plurality of wavelengths, said first optical combiner having an output supplying said first plurality of optical signals to an optical communication path;

an optical attenuator coupled to said optical communication path, said optical attenuator having an input receiving said first plurality of optical signals and an output supplying said first plurality of optical signals in attenuated form; and

a second optical combiner having a first input coupled to said output of said attenuator and receiving said attenuated first plurality of optical signals, and a second input receiving a second plurality of optical signals, each of said second plurality of optical signals being at a respective one of a second plurality of wavelengths, said second optical combiner having an output supplying said first and second pluralities of optical signals, each optical signal within said first and second pluralities of optical signals has substantially uniform optical power.

2. An optical device in accordance with claim 1, wherein said second optical combiner comprises a dielectric filter.

3. An optical device in accordance with claim 1, wherein said optical attenuator comprises:

a first optical fiber having a core portion and a cladding portion, said core and cladding of said first optical fiber being disposed about a first axis; and

a second optical fiber having a core portion and a cladding portion, said core and said cladding of said second optical fiber being disposed about a second axis, said first and second optical fibers being joined at respective ends thereof such that said first axis is offset from said second axis.

4. An optical device in accordance with claim 1, further comprising a third optical combiner, said third optical combiner receiving each of said second plurality of optical signals, and having an output for supplying said second plurality of optical signals, said output of said third optical combiner being coupled to said second input of said second optical combiner.

5. An optical device, comprising:

a first optical combiner having a plurality of inputs, each of which receiving a respective one of a first plurality of optical signals, each of said first plurality of optical signals being at a respective one of a first plurality of wavelengths, said first optical combiner having an output supplying said first plurality of optical signals;

a first optical attenuator having an input coupled to said output of said first optical combiner and an output supplying said first plurality of optical signals in attenuated form;

a second optical combiner having a first input receiving said attenuated first plurality of optical signals, a second input receiving a second plurality of optical signals, and an output supplying both said first and second pluralities of optical signals;

a third optical combiner having a plurality of inputs, each of which receiving a respective one of a third plurality of optical signals, each of said third plurality of optical signals being at a respective one of a third plurality of wavelengths, said third optical combiner having an output supplying said third plurality of optical signals;

a second optical attenuator coupled to said output of said third optical combiner, said second optical attenuator having an input receiving said third plurality of optical signals and an output supplying said third plurality of optical signals in attenuated form; and

a fourth optical combiner having a first input coupled to said output of said second optical attenuator, a second input coupled to said output of said second optical combiner and receiving said first and second pluralities of optical signals, and an output supplying said first, second and third pluralities of optical signals.

6. An optical device in accordance with claim 5, wherein said second and fourth optical combiners each include a dielectric filter.

7. An optical device in accordance with claim 5, wherein said first optical attenuator comprises:

a first optical fiber having a core portion and a cladding portion, said core and cladding of said first optical fiber being disposed about a first axis; and

a second optical fiber having a core portion and a cladding portion, said core and said cladding of said second optical fiber being disposed about a second axis, said first and second optical fibers being joined at respective ends thereof such that said first axis is offset from said second axis by a first distance.

8. An optical device in accordance with claim 7, wherein said second optical attenuator comprises:

a third optical fiber having a core portion and a cladding portion, said core and cladding of said first optical fiber being disposed about a third axis; and

a fourth optical fiber having a core portion and a cladding portion, said core and said cladding of said fourth optical fiber being disposed about a fourth axis, said third and fourth optical fibers being joined at respective ends thereof such that said third axis is offset from said fourth axis by a second distance, said first distance being different than said second distance.

9. An optical device in accordance with claim 5, wherein an attenuation associated with said first optical attenuator is different than an attenuation associated with said second optical attenuator.

10. An optical multiplexer, comprising:

a first optical combiner receiving a first plurality of optical signals, each of which being at a respective one of a first plurality of wavelengths, said first optical combiner having an output supplying said first plurality of optical signals to a first optical communication path;

a second optical combiner receiving a second plurality of optical signals, each of which being at a respective one of a second plurality of wavelengths, said second optical combiner having an output supplying said second plurality of optical signals to a second optical communication path;

an optical attenuator coupled to said second optical communication path, said optical attenuator having an input receiving said second plurality of optical signals and an output supplying said second plurality of optical signals in attenuated form; and

a third optical combiner having a first input coupled to said output of said attenuator and a second input receiving said first plurality of optical signals, said third optical combiner further having an output supplying said first and second pluralities of optical signals, each optical signal within said first and second pluralities of optical signals has substantially uniform optical power.

11. An optical device in accordance with claim 10, wherein said third optical combiner includes a dielectric filter.

12. An optical device comprising:

a first plurality of optical combiners, each of which receiving a respective one of a plurality of groups of optical signals, each optical signal within each of said plurality of groups being at a different wavelength, each of said first plurality of optical combiners having a respective output for supplying corresponding ones of said plurality of groups of optical signals;

a plurality of optical attenuators each of which being associated with a corresponding one of said first plurality of optical combiners, each of said plurality of optical attenuators supplying a corresponding one of said plurality of groups of optical signals through a respective output; and

a second plurality of optical combiners, each of which being coupled to a respective one of said plurality of optical attenuators, each of said plurality of optical combiners having a first input receiving one of said plurality of groups of optical signals from a corresponding one of said plurality of optical attenuators, a second input receiving at least a different one of said plurality groups of optical signals, and an output supplying said one of said one of said plurality of groups of optical signals and said different one of said plurality of groups of optical signals.

13. An optical device in accordance with claim 12, wherein each of said second plurality of optical combiners comprises a dielectric filter.

14. An optical device in accordance with claim 12, wherein each of optical signals output from one of said second plurality of optical combiners has substantially uniform optical power.

15. An optical communication device in accordance with claim 14, wherein each of said plurality of optical attenuators comprises:

a first optical fiber having a core portion and a cladding portion, said core and cladding of said first optical fiber being disposed about a first axis; and

a second optical fiber having a core portion and a cladding portion, said core and said cladding of said second optical fiber being disposed about a second axis, said first and second optical fibers being joined at respective ends thereof such that said first axis is offset from said second axis by an offset distance.

16. An optical device in accordance with claim 15, wherein said offset distance is different for each of said plurality of optical attenuators.

17. A method for multiplexing optical signals, comprising the steps of:

combining a first plurality of optical signals onto a single optical communication path;

attenuating said combined optical signals;

combining a second plurality of optical signals with said first plurality of optical signals, whereby each optical signal within said first and second pluralities of optical signals has substantially uniform optical power.

18. An optical device comprising:

a first optical combiner receiving a first plurality of optical signals, each of which being at a respective one of a first plurality of wavelengths, said first optical combiner having an output supplying said first plurality of optical signals to an optical communication path;

an optical attenuator coupled to said optical communication path, said optical attenuator having an input receiving said first plurality of optical signals and an output supplying said first plurality of optical signals in attenuated form, said optical attenuator comprising;

a first optical fiber having a core portion and a cladding portion, said core and cladding of said first optical fiber being disposed about a first axis; and

a second optical fiber having a core portion and a cladding portion, said core and said cladding of said second optical fiber being disposed about a second axis, said first and second optical fibers being joined at respective ends thereof such that said first axis is offset from said second axis; and

a second optical combiner having a first input coupled to said output of said attenuator and receiving said attenuated first plurality of optical signals, and a second input receiving a second plurality of optical signals, each of said second plurality of optical signals being at a respective one of a second plurality of wavelengths, said second optical combiner having an output supplying said first and second pluralities of optical signals.