Optical threshold devices and methods

• US 20040037524A1
• Filed: 04/02/2003
• Published: 02/26/2004
• Est. Priority Date: 08/22/2002
• Status: Active Grant

• Current Assignee: Main Street Ventures, LLC
• Original Assignee: Prima Luci, Inc.
• Inventors: Shahar, Arie, Halberthal, Eldan
• Granted Patent: US 6,892,016 B2
• Time in Patent Office: Days
• US Class Current: 385/122
• CPC Class Codes: G02B 2006/12107 Grating
• CPC Class Codes: G02B 2006/12142 Modulator
• CPC Class Codes: G02B 2006/12145 Switch
• CPC Class Codes: G02B 2006/12147 Coupler
• CPC Class Codes: G02B 2006/12164 Multiplexing; Demultiplexing
• CPC Class Codes: G02B 6/04 formed by bundles of fibres G02B6/24 takes precedence
• CPC Class Codes: G02B 6/125 Bends, branchings or intersections
• CPC Class Codes: G02B 6/2804 forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
• CPC Class Codes: G02B 6/2861 using fibre optic delay lines and optical elements associated with them, e.g. for use in signal processing, e.g. filtering delay lines in general H03H, H01P9/00; optical computing devices G06E
• CPC Class Codes: G02F 1/225 in an optical waveguide structure
• CPC Class Codes: G02F 1/3511 Self-focusing or self-trapping of light; Light-induced birefringence; Induced optical Kerr-effect
• CPC Class Codes: G02F 1/3523 Non-linear absorption changing by light, e.g. bleaching
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04J 14/08 Time-division multiplex systems

Abstract

An optical threshold device including an input, an output, first and second radiation guiding branches, each branch having first and second terminals, at least one of the first and second branches having a non-linear optical element, first and second optical couplers, at least one of the first and second optical couplers having an asymmetric optical coupler, the first optical coupler configured to split an input signal of radiation from the input into a first radiation portion propagating through the first branch and a second radiation portion propagating through the second branch, the second optical coupler configured to combine the first and second radiation portions from the second terminals of the first and second branches, respectively, into an output signal at the output, wherein the non-linear optical element produces a phase shift between the first and second radiation portions and wherein the first and second radiation portions interfere at the second coupler in response to the phase shift.

Claims

1. An optical threshold device comprising:

an input;

an output;

first and second radiation guiding branches, each branch having first and second terminals, at least one of said first and second branches comprising a non-linear optical element;

first and second optical couplers, at least one of said first and second optical couplers comprising an asymmetric optical coupler, said first optical coupler configured to split an input signal of radiation from said input into a first radiation portion propagating through said first branch and a second radiation portion propagating through said second branch, said second optical coupler configured to combine said first and second radiation portions from the second terminals of said first and second branches, respectively, into an output signal at said output,

wherein said non-linear optical element produces a phase shift between said first and second radiation portions and wherein said first and second radiation portions interfere at said second coupler in response to said phase shift.

2. The device of claim 1 wherein the interference between said first and second radiation portions at said second coupler is at least partly destructive when the intensity of said input signal is below a predetermined threshold level and at least partly constructive when the intensity of said input signal is above said threshold level

3. The device of claim 1 wherein each of said first and second branches comprises a non-linear optical element.

4. The device of claim 3 wherein the non-linear optical elements of said first and second branches are excited to different excitation levels.

5. The device of claim 3 wherein at least one of said first and second branches comprises an optical attenuator.

6. The device of claim 1 wherein said non-linear optical element comprises a non-linear optical element selected from, the group. consisting of an element including a solid state optical amplifier, a linear optical amplifier, and an Erbium doped fiber amplifier.

7. The device of claim 1 wherein the amplitude of the output signal at said output is responsive to a phase shift produced by said non-linear optical element.

8. The device of claim 1 wherein the amplitude of the output signal at said output is responsive to a gain function of said non-linear optical element.

9. The device of claim 1 wherein the amplitude of the output signal at said output is responsive to a phase shift and gain function of said non linear element.

10. The device of claim 1 wherein said predetermined threshold level is set by adjusting at least one parameter selected from the group consisting of a splitting ratio of said first optical coupler, a combining ratio of said second optical coupler, an excitation level of said non-linear optical element, and a gain of said non-linear optical element.

11. The device of claim 1 wherein at least one of said first and second branches and said input is operatively associated with an optical attenuator.

12. The device of claim 1 wherein at least one of said input and said output is operatively associated with an optical amplifier.

13. The device of claim 1 wherein said input is operatively associated with an optical amplifier and an optical attenuator.

14. The device of claim 1 wherein said first-optical coupler comprises a symmetric optical coupler.

15. The device of claim 1 wherein said second optical coupler comprises a symmetric optical coupler.

16. The device of claim 1 wherein at least one of said first and second branches comprises an optical phase shifter.

17. The device of claim 16 comprising a closed optical phase-control loop to controllably adjust said phase shifter.

18. The device of claim 17 wherein said closed optical phase-control loop comprises a controller arranged to tap a fraction of the output signal from said output and to adjust said optical phase shifter to maintain a predetermined relative phase between the radiation portions at the second terminals of said first and second branches.

19. The device of claim 17 wherein said closed optical phase-control loop has a response time shorter than a time period of said input signal.

20. The device of claim 17 wherein said closed optical phase-control loop comprises an averaging integrator.

21. The device of claim 1 comprising at least one optical fiber.

22. The device of claim 1 comprising at least one planar waveguide.

23. The device of claim 1 comprising integrated optics.

24. The device of claim 1 comprising a planar optical circuit.

25. The device of claim 1 comprising an on-chip optical device.

26. The device of claim 1 wherein said radiation is guided at least partly in a gaseous medium or vacuum.

27. The device according to claim 26 wherein at least one of said first and second optical couplers comprises a beam splitter.

28. An optical threshold device comprising:

an input;

an output;

first and second radiation guiding branches, each branch having first and second terminals, at least one of said first and second branches comprising a non-linear optical element and at least one of said first and second branches comprising an optical attenuator;

first and second optical couplers, said first optical coupler configured to split an input signal of radiation from said input into a first radiation portion propagating through said first branch and a second radiation portion propagating through said second branch, said second optical coupler configured to combine said first and second radiation portions from the second terminals of said first and second branches, respectively, into an output signal at said output,

wherein said non-linear optical element produces a phase shift between said first and second radiation portions and wherein said first and second radiation portions interfere at said second coupler in response to said phase shift.

29. The device of claim 28 wherein the interference between said first and second radiation portions at said second coupler is at least partly destructive when the intensity of said input signal is below a predetermined threshold level and at least partly constructive when the intensity of said input signal is above said threshold level.

30. An optical threshold method comprising:

splitting an input signal of radiation into a first radiation portion and a second radiation portion;

causing a phase shift between said first and second radiation portions; and

producing an output signal by interfering said first and second radiation portions in response to said phase shift,

wherein at least one of said splitting and said producing comprises an asymmetrical effect.

31. The method of claim 30 wherein interfering said first and second radiation portions comprises interfering said first and second radiation portions at least partly destructively when the intensity of said input signal is below a predetermined threshold level and interfering said first and second radiation portions at least partly constructively when the intensity of said input signal is above said threshold level.