Claims
- 1. A wavelength switchable optical filter, comprising:
b) an optical waveguide having a grating along a section thereof, said grating comprising a pre-selected number of spaced sub-gratings with each sub-grating having a sub-grating period, said grating having a spectral response characterized by a pre-selected number of spaced band-pass windows spanning a pre-selected wavelength range; and b) modifying means connected to said optical waveguide for modifying at least one of said sub-grating period, refractive index and a combination of sub-grating period and refractive index of each individual sub-grating for selectively opening or closing each of said band pass windows independently of all the other band pass windows.
- 2. The wavelength switchable optical filter according to claim 1 wherein said optical waveguide is an optical fiber.
- 3. The wavelength switchable optical filter according to claim 2 wherein said modifying means includes transduction means attached along an outer surface of said optical fiber adjacent to said sub-gratings for applying a pre-determined amount of strain individually to each sub-grating independent of the other sub-gratings for modifying the period of one or more of said sub-gratings.
- 4. The wavelength switchable optical filter according to claim 3 wherein said transduction means includes a plurality of piezoelectric elements with a separate piezoelectric element attached to said optical fiber adjacent to each separate sub-grating and including power supply control means for controlling a voltage on each piezoelectric element independent of a voltage applied on the other piezoelectric elements.
- 5. The wavelength switchable optical filter according to claim 4 wherein the number of piezoelectric elements attached to said outer surface of said optical fiber is equal to the number of sub-gratings in said grating.
- 6. The wavelength switchable optical filter according to claim 3 wherein said transduction means includes temperature control means for independently controlling the temperature of each sub-grating.
- 7. A method of wavelength switching, comprising the steps of:
providing an optical waveguide having a grating along a section thereof, said grating comprising a pre-selected number of spaced sub-gratings with each sub-grating having a sub-grating period, said grating having a spectral response characterized by a pre-selected number of spaced band-pass windows spanning a pre-selected wavelength range; and modifying at least one of said sub-grating period, refractive index and a combination of sub-grating period and refractive index of one or more selected said sub-gratings for opening or closing one or more selected band pass windows independently of all the other band pass windows.
- 8. The method according to claim 7 wherein said optical waveguide is an optical fiber.
- 9. The method according to claim 8 wherein said step of modifying includes activating a transduction means attached along an outer surface of said optical fiber adjacent to said sub-gratings for applying a pre-determined amount of strain individually to each sub-grating independent of the other sub-gratings for modifying the period of one or more of said sub-gratings.
- 10. The method according to claim 9 wherein said transduction means is a separate piezoelectric element attached to said optical fiber adjacent to each sub-grating, and wherein the step of modifying means includes activating one or more of said piezoelectric elements.
- 11. The method according to claim 9 wherein said transduction means includes temperature control means for independently controlling the temperature of each sub-grating.
- 12. A wavelength switchable optical filter, comprising:
b) an optical waveguide having a grating along a section thereof, said grating comprising a pre-selected number of spaced sub-gratings with each sub-grating having a sub-grating period, said grating having a spectral response characterized by alternating band stop windows and band pass windows spanning a selected wavelength range; and b) modifying means connected to said optical waveguide for modifying at least one of said sub-grating period, refractive index and a combination of sub-grating period and refractive index of one or more selected said sub-gratings for selectively opening or closing at least one band-pass window and simultaneously closing or opening a band-stop window adjacent to said at least one band-pass window.
- 13. The wavelength switchable optical filter according to claim 12 wherein said optical waveguide is an optical fiber.
- 14. The wavelength switchable optical filter according to claim 13 wherein said modifying means includes transduction means attached along an outer surface of said optical fiber adjacent to said sub-gratings for applying a pre-determined amount of strain individually to each sub-grating independent of the other sub-gratings for modifying the period of one or more of said sub-gratings.
- 15. The wavelength switchable optical filter according to claim 14 wherein said transduction means includes a plurality of piezoelectric elements with a separate piezoelectric element attached to said optical fiber adjacent to each separate sub-grating and including power supply control means for controlling a voltage on each piezoelectric element independent of a voltage applied on the other piezoelectric elements.
- 16. The wavelength switchable optical filter according to claim 15 wherein the number of piezoelectric elements attached to said outer surface of said optical fiber is equal to the number of sub-gratings in said grating.
- 17. The wavelength switchable optical filter according to claim 14 wherein said transduction means includes temperature control means for independently controlling the temperature of each sub-grating.
- 18. An optical switching device, comprising:
b) a wavelength switchable optical filter including an optical waveguide having a grating along a section thereof and an optical input for receiving optical signals and an optical output, said grating comprising a pre-selected number of spaced sub-gratings with each sub-grating having a sub-grating period, said grating having a spectral response characterized by a pre-selected number of spaced band-pass windows spanning a pre-selected wavelength range, and modifying means connected to said optical waveguide for modifying at least one of said sub-grating period, refractive index and a combination of sub-grating period and refractive index of each individual sub-grating for selectively opening or closing each of said band pass windows independently of all the other band pass windows; and b) optical branching means having at least first, second and third optical ports, said first optical port being an optical input port for receiving optical signals containing wavelengths within said pre-selected wavelength range, said optical branching means being optically connected through said second optical port to said optical input of said wavelength switchable optical filter.
- 19. The optical switching device according to claim 18 wherein said optical waveguide is an optical fiber.
- 20. The optical switching device according to claim 18 wherein said optical branching means is an optical circulator.
- 21. The optical switching device according to claim 19 wherein said modifying means includes transduction means attached along an outer surface of said optical fiber adjacent to said sub-gratings for applying a pre-determined amount of strain individually to each sub-grating independent of the other sub-gratings for modifying the period of one or more of said sub-gratings.
- 22. The optical switching device according to claim 21 wherein said transduction means includes a plurality of piezoelectric elements with a separate piezoelectric element attached to said optical fiber adjacent to each separate sub-grating and including power supply control means for controlling a voltage on each piezoelectric element independent of a voltage applied on the other piezoelectric elements.
- 23. The optical switching device according to claim 22 wherein the number of piezoelectric elements attached to said outer surface of said optical fiber is equal to the number of sub-gratings in said grating.
- 24. The wavelength switchable optical filter according to claim 21 wherein said transduction means includes temperature control means for independently controlling the temperature of each sub-grating.
- 25. The optical switching device according to claim 18 wherein said wavelength switchable optical filter is a first wavelength switchable optical filter, including a second wavelength switchable optical filter optically connected to said third optical port of said optical branching means.
- 26. The optical switching device according to claim 25 wherein said gratings in said first and second wavelength switchable optical filters are substantially the same having substantially the same spectral response.
- 27. The optical switching device according to claim 25 wherein said gratings in said first and second wavelength switchable optical filters are different from each other therefore having different spectral responses.
- 28. The optical switching device according to claim 25 wherein said optical waveguides of said first and second wavelength switchable optical filters are first and second optical fibers respectively.
- 29. The optical switching device according to claim 28 wherein said modifying means includes transduction means attached along an outer surface of each of said first and second optical fibers and positioned adjacent to said sub-gratings in each of said first and second optical fiber for applying a pre-determined amount of strain individually to each sub-grating independent of the other sub-gratings in said grating in each of said first and second optical fibers for modifying the period of one or more of said sub-gratings.
- 30. The optical switching device according to claim 29 wherein said transduction means includes a first set of piezoelectric elements with a piezoelectric elements from said first set being attached to said first optical fiber adjacent to each sub-grating in said first fiber, and including a second set of piezoelectric elements with piezoelectric elements from said second set being attached to said second optical fiber adjacent to each sub-grating in said second optical fiber, and including power supply control means for controlling a voltage on each piezoelectric element independent of a voltage applied on the other piezoelectric elements.
- 31. The optical switching device according to claim 30 wherein said gratings of said first and wavelength switchable optical filters are offset with respect to each other so that the spectrum of one of said gratings is offset with respect to the spectrum of the other grating by one half of a channel spacing, and wherein said first and second optical fibers are aligned together so that the gratings in each fiber are aligned side by side, and wherein said first set of piezoelectric elements is also the second set of piezoelectric elements so that each piezoelectric element is bonded to both said first and second optical fibers and is adjacent to a sub-grating in each of said first and second optical fibers, and including power supply control means for controlling a voltage on each piezoelectric element independent of a voltage applied on the other piezoelectric elements.
- 32. An optical switching device, comprising:
a) optical coupler means having an optical input for receiving optical signals and first and second optical coupler arms, a first wavelength switchable optical filter optically connected to said first optical coupler arm and a second wavelength switchable optical filter optically connected to said second optical coupler arm; and b) said first and second wavelength switchable optical filters each including an optical waveguide having a grating along a section thereof and an optical input for receiving optical signals from said first and second optical coupler arms respectively, each of said first and second wavelength switchable optical filters having an optical output, each grating comprising a pre-selected number of spaced sub-gratings with each sub-grating have a sub-grating period, said grating having a spectral response characterized by a pre-selected number of spaced band-pass windows spanning a pre-selected wavelength range, and modifying means connected to said optical waveguide for modifying at least one of said sub-grating period, refractive index and a combination of sub-grating period and refractive index of each individual sub-grating for selectively opening or closing each of said band pass windows independently of all the other band pass windows.
- 33. The optical switching device according to claim 32 including an optical isolator optically connected to said optical input of said optical branching means.
- 34. The optical switching device according to claim 33 wherein said optical waveguides of said first and second wavelength switchable optical filters are first and second optical fibers respectively.
- 35. The optical switching device according to claim 34 wherein said modifying means includes transduction means attached along an outer surface of each of said first and second optical fibers and positioned adjacent to said sub-gratings in each of said first and second optical fiber for applying a pre-determined amount of strain individually to each sub-grating independent of the other sub-gratings in said grating in each of said first and second optical fibers for modifying the period of one or more of said sub-gratings.
- 36. The optical switching device according to claim 35 wherein said transduction means includes a first set of piezoelectric elements with a piezoelectric elements from said first set being attached to said first optical fiber adjacent to each sub-grating in said first fiber, and including a second set of piezoelectric elements with piezoelectric elements from said second set being attached to said second optical fiber adjacent to each sub-grating in said second optical fiber, and including power supply control means for controlling a voltage on each piezoelectric element independent of a voltage applied on the other piezoelectric elements.
- 37. The optical switching device according to claim 36 wherein said gratings of said first and second wavelength switchable optical filters are offset with respect to each other so that the spectrum of one of said gratings is offset with respect to the spectrum of the other grating by one half of a channel spacing, and wherein said first and second optical fibers are aligned together so that the gratings in each fiber are aligned side by side, and wherein said first set of piezoelectric elements is also the second set of piezoelectric elements so that each piezoelectric element is bonded to both said first and second optical fibers and is adjacent to a sub-grating in each of said first and second optical fibers, and including power supply control means for controlling a voltage on each piezoelectric element independent of a voltage applied on the other piezoelectric elements.
- 38. An optical switching device, comprising:
a) odd/even channel interleaver means including an interleaver optical input for receiving optical signals and first and second interleaver arms, a first wavelength switchable optical filter optically connected to said first interleaver arm and a second wavelength switchable optical filter optically connected to second interleaver arm; b) said first and second wavelength switchable optical filters each including an optical waveguide having a grating along a section thereof and an optical input for receiving optical signals from said first and second optical coupler arms respectively, each of said first and second wavelength switchable optical filters having an optical output, each grating comprising a pre-selected number of spaced sub-gratings with each sub-grating having a sub-grating period, said grating having a spectral response characterized by a pre-selected number of spaced band-pass windows spanning a pre-selected wavelength range, and modifying means connected to said optical waveguide for modifying at least one of said sub-grating period, refractive index and a combination of sub-grating period and refractive index of each individual sub-grating for selectively opening or closing each of said band pass windows independently of all the other band pass windows; and c) an optical coupler, said optical outputs of said first and second wavelength switchable optical filters being optically connected to said optical coupler for combining optical signals transmitted through said first and second wavelength switchable optical filters, said optical coupler having an optical output for outputting said combined optical signals.
- 39. The optical switching device according to claim 38 wherein said odd/even channel interleaver means includes an optical branching means having first, second, third and fourth optical ports, wherein said first optical port is the interleaver input port, said first interleaver arm including an odd channel filter means connected to said second optical port for passing channels containing odd wavelengths in a pre-selected wavelength range and reflecting even wavelengths in said pre-selected wavelength range, said second interleaver arm including an even channel filter means connected to said third optical port for passing channels containing even wavelengths and reflecting odd wavelengths, said first wavelength switchable optical filter input being optically connected to said odd channel filter and said second wavelength switchable optical filter input being optically connected to said even channel filter, and wherein said fourth optical port is a drop port.
- 40. The optical switching device according to claim 39 wherein said optical waveguides are optical fibers.
- 41. The optical switching device according to claim 18 wherein said grating has a pre-selected spectral response characterized by alternating band stop windows and band pass windows spanning a selected wavelength range, and wherein a channel spacing of input signals is one half of a periodicity of said pre-selected spectral response so that when said switchable grating is in an off-state, those channels with wavelengths aligned with wavelengths of each of said band stop windows will be reflected to said third optical port of said optical branching means while those channels with wavelengths mis-aligned with wavelength of each band pass region will pass through the switchable grating to an output port of said wavelength switchable grating, and when said switchable grating is in an on-state, all dropped channels will pass to said output port of said wavelength switchable grating, and vice versa.
CROSS REFERENCE TO RELATED U.S. PATENT APPLICATIONS
[0001] This patent application relates to U.S. provisional patent application Serial No. 60/306,158 filed on Jul. 19, 2001 entitled Random Access Optical Add/Drop Multiplexer.
Provisional Applications (1)
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Number |
Date |
Country |
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60306158 |
Jul 2001 |
US |