Claims
- 1. A 2×2 optical switch having a main propagation axis, comprising:
a) a first 3 dB adiabatic coupler having a first pair of symmetric branches, said first coupler further characterized by having two straight branches with different widths, said first coupler straight branches separated over a coupling length by a changing spacing therebetween; b) a second 3 dB adiabatic coupler having a second pair of symmetric branches, said second coupler further characterized by having two straight branches with different widths, said second coupler straight branches separated over a coupling length by a changing spacing therebetween, said first and second adiabatic couplers facing each other with their respective symmetric branches along the main propagation axis in a mirror image; c) two identical arms connecting said first and second pairs of symmetric branches optically to each other along the main propagation axis; and d) at least one active element coupled to at least one of said identical arms for dynamically changing an optical property of said at least one arm, whereby the implementation of the switch in a planar lightwave circuit provides a switch which is practically polarization independent, and has a low loss and a very high extinction ratio over an exceptionally broad band range.
- 2. The switch of claim 1, wherein said first and second adiabatic couplers are identical.
- 3. The switch of claim 1, wherein said two straight branches with different widths include two straight input waveguides with different widths that intersect to form a small adiabatic angle and blend in a symmetric intersection area.
- 4. The switch of claim 3, wherein at least one of said couplers further includes an optional mediating waveguide located between said intersection area and said symmetric branches.
- 5. The switch of claim 4, wherein at least one of said couplers further includes a first blunt located at said intersection of said two straight and adiabatic input waveguides and said mediating waveguide, and, optionally, a second blunt located at the intersection of said mediating waveguide and said symmetric branches.
- 6. The switch of claim 1, wherein at least one of said couplers further includes a pair of symmetric input bends, each said input bend having an input bend width, each said input bend connected to a respective said straight branch and used for connecting said coupler to a pair of optical ports.
- 7. The switch of claim 6, wherein said connection of each said input bend to a respective straight branch is mediated by an adiabatic taper.
- 8. The switch of claim 1, wherein said couplers and said identical arms are built of silica on a silicon substrate, and wherein said optical property of said arm includes an index of refraction of said arm.
- 9. The switch of claim 8, wherein said extinction ratio is selected from the group consisting of an extinction ratio of at least 34 in the C+L bands, and an extinction ratio of at least 20 in the 1.3 μm wavelength window.
- 10. The switch of claim 1, wherein said identical arms are further characterized by being straight waveguides with equal cross sections and equal lengths.
- 11. The switch of claim 1, wherein said at least one active element coupled to at least one of said identical arms includes an active element on each of said identical arms, whereby a combined use of said two active elements can actively compensate for any asymmetry effect in said arms.
- 12. An optical switch having a main propagation axis, comprising:
a) a Y-splitter that includes an input waveguide and a first pair of symmetric branches; b) a 3 dB adiabatic coupler having a second pair of symmetric branches, said coupler further characterized by having two straight branches with different widths, said coupler straight branches separated over a coupling length by a changing spacing therebetween, said Y-splitter and said adiabatic coupler facing each other with their respective symmetric branches along the main propagation axis in a mirror image; c) two identical arms connecting said first and second pairs of symmetric branches optically to each other along the main propagation axis; and d) at least one active element coupled to at least one of said identical arms for dynamically changing an optical property of said arm, whereby the implementation of the switch in a planar lightwave circuit provides a switch which is practically polarization independent, and which has a low loss and a very high extinction ratio over an exceptionally broad band range.
- 13. The optical switch of claim 12, configured as a switch selected from the group consisting of 1×2 optical switches and 2×1 optical switches.
- 14. The switch of claim 12, wherein said Y-splitter further includes an adiabatic taper connecting between said input waveguide and said pair of first symmetric branches.
- 15. The switch of claim 14, wherein said two straight branches of said coupler further include two straight and adiabatic input waveguides with unequal widths that intersect to form a small angle and blend in a symmetric intersection area.
- 16. The switch of claim 15, wherein said adiabatic coupler further includes an optional mediating waveguide located between said intersection area and said second pair of symmetric branches.
- 17. The switch of claim 16, wherein said Y-splitter further includes an optional splitter blunt at an interface between said adiabatic taper and said first pair of symmetric branches, and wherein said coupler further includes an optional first blunt located at said intersection of said two straight branches and said mediating waveguide, and, optionally, a second blunt located at the intersection of said mediating waveguide and said symmetric branches
- 18. The switch of claim 12, wherein said coupler further includes a pair of symmetric input bends, each said input bend having an input bend width, each said input bend connected to a respective said straight branch and used for connecting said coupler to a pair of optical ports.
- 19. The switch of claim 18, wherein said connection of each said input bend to a respective straight branch is mediated by an adiabatic taper.
- 20. The switch of claim 12, wherein said Y-splitter, said coupler and said two identical arms are built of silica on a silicon substrate, and wherein said optical property of said arm includes an index of refraction of said arm.
- 21. The switch of claim 12, wherein said extinction ratio is selected from the group consisting of an extinction ratio of at least 34 in the C+L bands, and an extinction ratio of at least 20 in the 1.3 μm wavelength window.
- 22. A 3 dB broadband adiabatic coupler, comprising:
a) two straight branches having different widths, separated over a coupling length by a changing spacing therebetween, and blending in a symmetric intersection area having a proximal and a distal end, and b) two symmetric branches connected to said intersection area at said distal end.
- 23. The 3 dB coupler of claim 22, further comprising a mediating waveguide symmetrically located immediately between said intersection area and said symmetric branches.
- 24. The 3 dB coupler of claim 23, further comprising a first optional blunt related to said straight branches at said intersection area proximal end, and, optionally, a second optional blunt related to said symmetric branches at said intersection area distal end, whereby both said optional blunts improve the tolerance to process related defects.
- 25. The 3 dB coupler of claim 24, further comprising input and output bends as extensions of respectively said straight branches and said symmetric branches, for connection to respective input and output ports.
- 26. The 3 dB coupler of claim 24 implemented in a planar lightwave circuit using silica on a silicon substrate.
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of priority from U.S. Provisional Application No. 60/341,240 filed Dec. 20, 2001, the contents of which are incorporated herein by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60341240 |
Dec 2001 |
US |