Optical threshold devices and methods

• US 20040037525A1
• 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 6,795,626 B2
• Time in Patent Office: Days
• US Class Current: 385/122
• CPC Class Codes: G02F 1/212 Mach-Zehnder type
• CPC Class Codes: G02F 1/3517 using an interferometer
• CPC Class Codes: G02F 1/3519 of Sagnac type, i.e. nonlinear optical loop mirror [NOLM]

Abstract

An optical threshold device including an optical loop having first and second terminals aid including at least one non-linear optical element and at least one optical attenuator; and an optical coupler able to couple a first portion of an input signal to the first terminal and a second portion of the input signal to the second terminal, wherein the optical loop is able to produce a first return signal at the second terminal and a second return signal at the first terminal, and wherein the optical coupler is able to combine the first and second return signals into an output signal.

Claims

1. An optical threshold device comprising:

an optical loop having first and second terminals and comprising at least one non-linear optical element and at least one optical attenuator; and

an optical coupler able to couple a first portion of an input signal to said first terminal and a second portion of the input signal to said second terminal,

wherein said optical loop is able to produce a first return signal at said second terminal and a second return signal at said first terminal, and wherein said optical coupler is able to combine the first and second return signals into an output signal.

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

3. The device of claim 1 wherein said at least one optical attenuator comprises an optical amplifier adapted to operate as an attenuator.

4. The device of claim 3 wherein said optical amplifier comprises an optical amplifier selected from the group consisting of a solid-state optical amplifier, a linear optical amplifier, and an Erbium doped fiber amplifier.

5. The device of claim 1 wherein said at least one non-linear optical element is positioned on said optical loop at a position which minimizes influence between said first and second input portions.

6. The device according to claim 1 wherein said at least one non-linear optical element and said at least one optical attenuator are positioned on said optical loop such that said nonlinear optical element is able to receive said first component prior to its attenuation by said at least one optical attenuator and to receive said second input portion after its attenuation by said at least one optical attenuator.

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

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

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

10. 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 at least one non-linear optical element.

11. The device of claim 1 wherein said predetermined intensity threshold level is set by adjusting at least one parameter selected from the group consisting of an excitation level of said at least one non-linear optical element, a gain of said at least one non-linear optical element, and an attenuation of said at least one optical attenuator.

12. The device of claim 1 wherein said at least one non-linear optical element comprises first and second non-linear optical elements.

13. The device of claim 1 wherein said at least one optical attenuator comprises first and second optical attenuators.

14. The device of claim 1 wherein said at least one non-linear optical element comprises first and-second non-linear optical elements and wherein said at least one optical attenuator comprises first and second optical attenuators.

15. The device of claim 14 wherein said second optical attenuator is positioned on said optical loop between said first non-linear optical, element and said second non-linear optical element.

16. The device of claim 14 wherein said second optical attenuator is positioned on said optical loop between said first optical attenuator and said second non-linear optical element.

17. The device of claim 14 wherein said first and second non-linear optical elements are excited to different excitation levels.

18. The device of claim 1 wherein said optical loop comprises at least one optical fiber.

19. The device of claim 1 wherein said optical loop comprises at least one planar waveguide.

20. The device of claim 1 comprising integrated optics.

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

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

23. The device of claim 1 wherein at least a potion of said optical loop comprises a gaseous medium or vacuum.

24. The device according to claim 23 wherein said optical coupler comprises a beam splitter.

25. An optical threshold device comprising:

an optical loop having first and second terminals;

an optical coupler associated;

with said first and second terminals and configured to couple a first portion of an input signal to said first terminal and a second portion of said input signal to said second terminal;

at least one non-linear optical element and at least one optical attenuator on said optical loop configured to shift the phase of said first portion by a first phase shift and to shift the phase of said second portion by a second phase shift different from said first phase shift,

wherein said optical coupler is able to combine a first return signal at said second terminal and a second return signal at said first terminal into an output signal responsive to the difference between said first and second phase shifts.

26. An optical threshold device comprising:

an optical loop having first and second terminals;

an optical coupler associated with said first and second terminals and configured to couple a first portion of an input signal to said first terminal and a second portion of said input signal to said second terminal;

at least one non-linear optical element on said optical loop able to receive and transmit said first portion in a first propagation direction and to receive and transmit said second portion in a second propagation direction; and

at least one optical attenuator on said optical loop able to attenuate said first portion before it is received by said non-linear element and to attenuate said second portion after it is transmitted through said non-linear element,

wherein said non-linear optical element is further able to produce a phase difference between said first and second portions responsive to a difference in amplitude between said first and second portions before said portions are transmitted through said non-linear element,

and wherein said optical coupler is able to combine said first and second portions after said portions are transmitted through said non-linear element into an output signal responsive to said phase difference.

27. An optical threshold device according to claim 26 wherein said optical coupler comprises a substantially symmetric optical coupler and wherein the intensities of said first and second portions of said signal are substantially equal before propagating trough said optical loop.

28. An optical threshold device comprising:

an input;

an output;

an optical coupler associated with said input and said output and able to couple an input signal from said input into a first input portion and a second input portion, and

an optical loop having first and second terminals associated with said optical coupler to receive said first and second input portions, respectively, and comprising at least one non-linear optical element and at least one optical attenuator, said optical loop able to produces a first return signal at said second terminal and a second return signal at said first terminal,

wherein said optical coupler is further able to combine said first and second return signals into an output signal at said output by interference between said first and second return signals.

29. The device of claim 28 wherein said interference is at least partly destructive below a predetermined intensity threshold level of said input signal and at least partly constructive above said intensity threshold level.

30. An optical threshold method comprising:

receiving an input signal;

coupling a first portion of said input signal to a first terminal of an optical loop comprising a non-linear optical element and an optical attenuator;

coupling a second portion of said input signal to a second terminal of said optical loop;

producing first and second return signals at said second and first terminals, respectively, by simultaneously propagating said first and second input portions, respectively, through said loop in opposite directions; and

combining said first and second return signals into an output signal.

31. The method of claim 30 wherein combining said first and second return signals comprises:

interfering said first and second return signals at least partly destructively when the intensity of said input signal is below a predetermined threshold level; and

interfering said first and second return signals at least partly constructively when the intensity of said input signal is above said threshold level.

32. The method of claim 30 wherein the intensities of said first and second input portions are substantially equal.

33. The method of claim 30 wherein propagating said first and second input portions through said loop comprises attenuating and non-linearly transmitting said first and second input portions.

34. The method according to claim 33 wherein attenuating and non-linearly transmitting said first and second input portions comprises attenuating before non-linearly transmitting said first input portion and attenuating after non-linearly transmitting said second input portion.

35. The method of claim 30 wherein propagating said first and second input portions through said loop comprises producing a predetermined phase shift between said first and second return signals.

36. The method of claim 30 wherein the amplitude of said output signal is responsive to said phase shift.

37. The method of claim 30 wherein propagating said first and second input portions through said loop comprises applying a predetermined gain function to said first and second input portions.

38. The method of claim 30 wherein the amplitude of said output signal is responsive to said gain function.

39. The method according to claim 30 wherein propagating said first and second input portions through said loop comprises preventing mutual influence between said first and second input portions in said loop.

40. The method of claim 30 comprising setting said threshold level by adjusting at least one parameter selected from the group consisting of an excitation level of a non-linear optical element in said optical loop, a gain of an optical elements in said optical, and an attenuation of an optical element in said optical loop.

41. The method of claim 30 wherein producing said first and second return signals comprises producing a predetermined phase difference between said first and second return signals.