Apparatus and method for high speed optical signal processing

• US 6,493,488 B1
• Filed: 12/22/2000
• Issued: 12/10/2002
• Est. Priority Date: 12/22/2000
• Status: Expired due to Fees

• Current Assignee: Cheetah Omni LLC
• Original Assignee: Celeste Optics, Inc.
• Inventors: Islam, Mohammed N., Kuditcher, Amos
• Primary Examiner(s): Sanghavi, Hemang
• Assistant Examiner(s): ROJAS, OMAR R
• Application Number:
  US09/746,850
• Time in Patent Office: 718 Days
• Field of Search: G02/B.626, G02/B.628, G02/B.635, G02/B 2.600, G02/B 2.602, 385/16, 385/18, 385/25, 385/39, 385/47, 385/140
• US Class Current: 385/47
• CPC Class Codes: G02B 6/266 the optical element being an attenuator
• CPC Class Codes: G02B 6/272 comprising polarisation means for beam splitting and combining
• CPC Class Codes: G02B 6/2766 Manipulating the plane of polarisation from one input polarisation to another output polarisation, e.g. polarisation rotators, linear to circular polarisation converters
• CPC Class Codes: G02B 6/29383 Adding and dropping
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02B 6/3516 the reflective optical element moving along the beam path, e.g. controllable diffractive effects using multiple micromirrors within the beam
• CPC Class Codes: G02B 6/356 in an optical cross-connect device, e.g. routing and switching aspects of interconnecting different paths propagating different wavelengths to (re)configure the various input and output links switching polarized beams G02B6/3594; power equalizers G02B6/356 and G02B6/3594; path selecting means H04Q11/0001
• CPC Class Codes: G02B 6/357 Electrostatic force electrostatic forces controlling reflecting elements in general G02B26/0841
• CPC Class Codes: G02B 6/3594 Characterised by additional functional means, e.g. means for variably attenuating or branching or means for switching differently polarized beams
• CPC Class Codes: H04Q 2011/003 using switches based on microelectro-mechanical systems [MEMS]
• CPC Class Codes: H04Q 2011/0035 using miscellaneous components, e.g. circulator, polarisation, acousto/thermo optical

Abstract

In one aspect of the invention, an apparatus operable to facilitate optical signal processing includes a micro-electro-optic system (MEMS) device having a moveable mirror layer operable to receive a first copy of an input signal from a beam splitter and to reflect the first copy of the input signal for combination with a second copy of the input signal at an output to form an output signal. The moveable mirror layer being displaceable in a substantially piston-like motion to introduce a phase shift between the first and second signal copies at the output. The amplitude of the output signal varying depending on the displacement of the moveable mirror layer.

Claims

1. A signal processing device, comprising:

a first beam splitter operable to receive an optical input signal and communicate at least two copies of the input signal in at least two directions;

a plurality of reflective surfaces, each operable to receive one of the signal copies and to reflect the copies for ultimate combination at an output to form an output signal;

wherein at least one of the reflective surfaces comprises a moveable mirror layer of a first micro-electro-optic system (MEMS) device, the moveable mirror layer operable to experience a substantially piston-like motion to change its position relative to the first beam splitter, the change in position causing a phase shift between the signal copies and a corresponding interference between the signal copies at the output, the amplitude of the output signal operable to vary depending on the position of the moveable mirror.

2. The signal processing device of claim 1, wherein the first beam splitter comprises a partially silvered mirror or a mirror having at least one layer of dielectric coating.

3. The signal processing device of claim 1, wherein the first beam splitter comprises a fiber coupler.

4. The signal processing device of claim 1, wherein the first MEMS device comprises:

an inner conductive layer disposed inwardly from the moveable mirror layer and forming a space between the moveable mirror layer and the inner conductive layer;

wherein the moveable mirror layer comprises an at least substantially conductive layer operable to move relative to the inner conductive layer in response to a voltage difference between the moveable mirror layer and the inner conductive layer.

5. The signal processing device of claim 4, wherein the moveable mirror layer is operable to facilitate variable attenuation by selectively moving a distance relative to the inner conductive layer, wherein the distance increases as the voltage difference increases.

6. The signal processing device of claim 4, wherein the moveable mirror layer is operable to facilitate optical switching by selectively moving relative to the inner conductive layer by a distance of either approximately zero or approximately one half of a wavelength of the input optical signal.

7. The signal processing device of claim 4, wherein the inner conductive layer comprises a doped semiconductor substrate.

8. The signal processing device of claim 4, wherein the inner conductive layer comprises a layer of at least substantially conductive material formed outwardly from a semiconductor substrate.

9. The signal processing device of claim 4, wherein the moveable mirror layer comprises a plurality of adjacent mirror strips, at least some of the plurality of adjacent mirror strips separated by air gaps operable to relieve air damping when the mirror strips move relative to the inner conductive layer.

10. The signal processing device of claim 9, wherein all of the moveable mirror strips move at least substantially in unison in response to the voltage difference.

11. The signal processing device of claim 9, wherein either the inner conductive layer or each of the moveable mirror strips is coupled to a ground, and wherein the other is operable to receive a control voltage signal.

12. The signal processing device of claim 1, wherein at least two of the reflective surfaces comprise moveable mirror layers of micro-electro-optic system (MEMS) devices, each operable to receive one of the signal copies, and each operable to be displaced between a first position and a second position in response to a control signal, the displacement resulting in a phase difference between the signal copies at the output.

13. The signal processing device of claim 12, wherein one of the moveable mirror layers is operable to switch from a first position to a second position to lengthen the path length of its associated signal copy through the device, while the other moveable mirror layer is operable to switch from a second position to a first position to shorten the path length of its associated second signal copy through the device.

14. The signal processing device of claim 1, wherein a grazing angle between the moveable mirror layer and the signal copy reflected by the moveable mirror layer comprises an angle that is less than forty-five degrees.

15. The signal processing device of claim 1, further comprising a second MEMS device disposed between the first MEMS device and the output, the second MEMS device comprising a moveable mirror layer operable to receive a phase shifted signal copy from the first MEMS device and to change its position relative to the first MEMS device to introduce a further phase shift to the signal copy.

16. The signal processing device of claim 15, wherein the moveable mirror layers of the first and second MEMS devices are collectively operable to facilitate optical switching by each moving relative to its associated inner conductive layer to result in a combined displacement of moveable mirror layers of either approximately zero or approximately one half of a wavelength of the input optical signal.

17. The signal processing device of claim 1, further comprising at least one additional reflective surface between the first beam splitter and the first MEMS device, the at least one additional reflective surface operable to receive a signal copy from the first beam splitter and to reflect the signal copy for ultimate reception by the first mirror.

18. The signal processing device of claim 1, wherein the output comprises the first beam splitter.

19. The signal processing device of claim 1, wherein the output comprises a second beam splitter.

20. An apparatus operable to facilitate optical signal processing, comprising:

a micro-electro-optic system (MEMS) device comprising a moveable mirror layer operable to receive a first copy of an input signal from a beam splitter and to reflect the first copy of the input signal for combination with a second copy of the input signal at an output to form an output signal, the moveable mirror layer displaceable in a substantially piston-like motion to introduce a phase shift between the first and second signal copies at the output, the amplitude of the output signal varying depending on the displacement of the moveable mirror layer.

21. The apparatus of claim 20, wherein the MEMS device comprises:

an inner conductive layer disposed inwardly from the moveable mirror layer and forming a space between the moveable mirror layer and the inner conductive layer;

wherein the moveable mirror layer comprises an at least substantially conductive layer operable to move relative to the inner conductive layer in response to a voltage difference between the moveable mirror layer and the inner conductive layer.

22. The apparatus of claim 21, wherein the inner conductive layer comprises a doped semiconductor substrate.

23. The apparatus of claim 21, wherein the inner conductive layer comprises a layer of at least substantially conductive material formed outwardly from a semiconductor substrate.

24. The apparatus of claim 21, wherein the moveable mirror layer comprises a plurality of adjacent mirror strips, at least some of the plurality of adjacent mirror strips separated by air gaps operable to relieve air damping when the mirror strips move relative to the inner conductive layer.

25. The apparatus of claim 24, wherein all of the moveable mirror strips move at least substantially in unison in response to the voltage difference.

26. The apparatus of claim 24, wherein either the inner conductive layer or each of the moveable mirror strips is coupled to a ground, and wherein the other is operable to receive a control voltage signal.

27. The apparatus of claim 21, wherein the moveable mirror layer is operable to facilitate variable attenuation by selectively moving a distance relative to the inner conductive layer, wherein the distance increases as the voltage difference increases.

28. The apparatus of claim 21, wherein the moveable mirror layer is operable to facilitate optical switching by selectively moving relative to the inner conductive layer by a distance of either approximately zero or approximately one half of a wavelength of the input optical signal.

29. A method of optical signal processing, comprising:

receiving an optical input signal at an input;

communicating a first copy of the input signal toward a first reflective surface and a second copy of the input signal toward second reflective surface, at least one of the reflective surfaces comprising a moveable mirror layer of a first micro-electro-optic system (MEMS) device;

reflecting the first and second signal copies toward an output;

combining components of the reflected first and second signal copies to form at least one optical output signal; and

displacing the moveable mirror layer in a substantially piston-like motion to result in an interference between the first and second signal copies at the output and a corresponding change in the amplitude of the output signal relative to the amplitude of the input signal.

30. The method of claim 29, wherein receiving the optical input signal comprises receiving the optical input signal at a first beam splitter.

31. The method of claim 29, wherein the MEMS device comprises an inner conductive layer disposed inwardly from the moveable mirror layer and forming a space between the moveable mirror layer and the inner conductive layer;

and

wherein changing the position of the moveable mirror layer comprises displacing the moveable mirror layer relative to the inner conductive layer in response to a voltage difference between the moveable mirror layer and the inner conductive layer.

32. The method of claim 31, wherein the moveable mirror layer comprises a plurality of adjacent mirror strips, at least some of the plurality of adjacent mirror strips separated by air gaps operable to relieve air damping when the mirror strips move relative to the inner conductive layer.

33. The method of claim 32, wherein changing the position of the moveable mirror layer comprises displacing all of the moveable mirror strips relative to the inner conductive layer substantially in unison in response to the voltage difference.

34. The method of claim 32, wherein changing the position of the moveable mirror layer comprises:

coupling either the inner conductive layer or each of the moveable mirror strips to a ground; and

applying to the other a control voltage signal.

35. The method of claim 31, wherein changing the position of the moveable mirror layer comprises selectively displacing the moveable mirror layer relative to the inner conductive layer, wherein the distance increases as the voltage difference between the moveable mirror layer and the inner conductive layer increases.

36. The method of claim 31, wherein changing the position of the first mirror comprises selectively displacing the moveable mirror layer relative to the inner conductive layer by a distance of either approximately zero or approximately one half of a wavelength of the input optical signal.

37. The method of claim 29, wherein:

the first reflective surface comprises a moveable mirror layer of a first MEMS device; and

the second reflective surface comprises a moveable mirror layer of a second MEMS device.

38. The method of claim 37, further comprising changing the position of the moveable mirror layer of the second MEMS device to result in additional interference between the first and second signal copies at the output and a corresponding change in the amplitude of the output signal relative to the amplitude of the input signal.

39. The method of claim 29, further comprising positioning the first and second reflective surfaces at an angle of less than forty-five degrees to the first and second signal copies, respectively.

40. The method of claim 29, further comprising:

receiving at a third reflective surface and a fourth reflective surface, the reflected first and second signal copies from the first and second reflective surfaces, respectively;

further reflecting the reflected first and second signal copies toward the output; and

changing the position of the third reflective surface to result in a further interference between the first and second signal copies at the output and a corresponding change in the amplitude of the output signal relative to the amplitude of the input signal.

41. A signal processing device, comprising:

a first beam splitter operable to receive an optical input signal and communicate at least two copies of the input signal in at least two directions;

a plurality of reflective surfaces, each operable to receive one of the signal copies and to reflect the copies for ultimate combination at an output to form an output signal;

wherein at least one of the reflective surfaces comprises a moveable mirror layer of a first micro-electro-optic system (MEMS) device, the moveable mirror layer comprising a plurality of adjacent mirror strips operable to receive one of the signal copies, all of the plurality of mirror strips operable to experience a substantially piston-like motion to change their position at least substantially in unison relative to the first beam splitter, the change in position causing a phase shift between the signal copies and a corresponding interference between the signal copies at the output, the amplitude of the output signal operable to vary depending on the position of the moveable mirror strips.

42. A method of optical signal processing, comprising:

receiving an optical input signal at an input;

communicating a first copy of the input signal toward a first reflective surface and a second copy of the input signal toward second reflective surface, at least one of the reflective surfaces comprising a moveable mirror layer of a first micro-electro-optic system (MEMS) device, the moveable mirror layer comprising a plurality of adjacent mirror strips;

reflecting the first and second signal copies toward an output;

combining components of the reflected first and second signal copies to form at least one optical output signal; and

displacing substantially all of the adjacent mirror strips substantially in unison in a substantially piston-like motion to result in an interference between the first and second signal copies at the output and a corresponding change in the amplitude of the output signal relative to the amplitude of the input signal.