Reconfigurable free space wavelength cross connect

• US 20020164114A1
• Filed: 04/11/2002
• Published: 11/07/2002
• Est. Priority Date: 04/13/2001
• Status: Active Grant

• Current Assignee: Lumentum Operations, LLC (Lumentum Holdings Inc.)
• Original Assignee: Movaz Networks, Inc. (ADTRAN Holdings, Inc.)
• Inventors: Smith, David A., Presley, Harry, Bao, Zhuoyu, Golub, John E.
• Granted Patent: US 6,694,073 B2
• Time in Patent Office: Days
• US Class Current: 385/18
• CPC Class Codes: G02B 6/266 the optical element being an attenuator
• CPC Class Codes: G02B 6/2931 Diffractive element operating in reflection
• CPC Class Codes: G02B 6/29313 characterised by means for controlling the position or direction of light incident to or leaving the diffractive element, e.g. for varying the wavelength response switching G02B6/35
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/3518 the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device MEMS devices in general B81B; manufacture of MEM devices in general B81C; micromechanical devices controlling the direction of light G02B26/0833
• CPC Class Codes: G02B 6/3542 Non-blocking switch, e.g. with multiple potential paths between multiple inputs and outputs, the establishment of one switching path not preventing the establishment of further switching paths
• 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 6/3582 Housing means or package or arranging details of the switching elements, e.g. for thermal isolation
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 2011/0016 using wavelength multiplexing or demultiplexing
• CPC Class Codes: H04Q 2011/0022 using fibre gratings
• CPC Class Codes: H04Q 2011/0024 using space switching
• CPC Class Codes: H04Q 2011/003 using switches based on microelectro-mechanical systems [MEMS]
• CPC Class Codes: H04Q 2011/0049 Crosstalk reduction; Noise; Power budget
• CPC Class Codes: H04Q 2011/0052 Interconnection of switches

Abstract

An optical cross connect, especially a wavelength cross connect, using free-space optics, a diffraction grating, and a micro electromechanical systems (MEMS) array of movable mirrors. A concentrator receives light from widely separated optical fibers and brings the beams together into a more closely spaced linear array. Free-space optics process all the beams. Front-end optics collimate the beams from the fibers and flatten their fields. The diffraction grating spectrally separates each beam into sub-beams. A long-focus lens focuses the sub-beams onto the 2-dimensional MEMS array. A fold mirror reflectively couples two such mirrors, whereby the switched signals propagate back through the same optics and are spectrally recombined onto the fibers. Other embodiments include white-color cross connects, multiple MEMS arrays, and parallel optics. Power dividers or wavelength interleavers can divide signals from the fibers, and multiple cross connects switch different wavelength groups.

Claims

1. A wavelength cross connect, comprising:

at least three optical waveguides having waveguide ends arranged in a first linear array extending in a first direction perpendicular to a principal optical plane;

a wavelength dispersive element uniform in said first direction and coupled to beams associated with each of said waveguide ends and spectrally separating wavelength components of said beams with wavelength-separated sub-beams disposed in a two-dimensional array arranged in a first waveguide direction and a first wavelength direction;

a first set of free-space optics arranged along an optical axis extending in said principal optical plane and coupling said waveguides and said wavelength dispersive element;

a plurality of micro electromechanical system (MEMS) mirrors arranged in a first mirror array arranged in at least a second wavelength direction and coupling at least one of said waveguides to a selected one of others of said waveguides.

2. The cross connect of claim 1, wherein said first mirror array is a two-dimensional array additionally extending in a waveguide direction.

3. The cross connect of claim 2, further comprising a fold mirror coupling pairs of mirrors in said first mirror array.

4. The cross connect of claim 1, further comprising a second mirror array of MEMS mirror extending at least in a third waveguide direction.

5. The cross connect of claim 1, further comprising a second set of free space optics extending along said optical axis in said principal optical plane and coupling said wavelength dispersive element to said first MEMS array.

6. The cross connect of claim 5, wherein beams passing between two optical elements of said first and second set of free space optics cross beams passing between two other optical elements of said first and second set of free space optics.

7. The cross connect of claim 5, wherein a magnification of a combination of said first and second free space optics is between 10 and 100.

8. The cross connect of claim 1, wherein said wavelength dispersive element is a diffraction grating and wherein said first set of free space optics includes a prism compensating an astigmatism of said diffraction grating.

9. The cross connect of claim 1, further comprising a concentrator in which said waveguides are formed in a curved pattern spaced more closely together at said waveguide ends than at portions away from said waveguide ends.

10. A wavelength cross connect, comprising:

at least three optical waveguides having waveguide ends arranged in a first linear array;

a wavelength dispersive element coupled to beams associated with each of said waveguide ends and spectrally separating wavelength components of said beams with wavelength-separated sub-beams disposed in a two-dimensional array arranged in a first waveguide direction and a first wavelength direction;

a first set of free-space optics coupling said waveguides and said wavelength dispersive element;

a fold mirror;

a plurality of micro electromechanical system (MEMS) mirrors arranged in a two-dimensional array arranged in a second waveguide direction and a second wavelength direction, pairs of said mirrors disposed at one location along said second wavelength direction being movable to couple light through said fold mirrors between respective ones of said pairs; and

a second set of free-space optics coupling said wavelength dispersive element to said MEMS mirrors and said fold mirror;

wherein one of said waveguides is selectively coupled to either of two others of said waveguides.

11. The cross connect of claim 10, wherein said at least three waveguides comprise at least two first waveguides and at least two second waveguides and wherein each of said first waveguides is selectively coupled to any of said second waveguides.

12. The cross connect of claim 11, wherein all of said first waveguides are arranged in said linear array inside respective ones of said second waveguides.

13. The cross connect of claim 10, wherein said MEMS mirrors are formed in a plane.

14. The cross connect of claim 13, wherein said MEMS mirrors are formed in a single substrate.

15. The cross connect of claim 13, wherein said beams and sub-beams propagate substantially parallel to a principal optical plane, and wherein said plane of said MEMS mirrors is inclined with respect to said principal optical plane.

16. The cross connect of claim 15, wherein said fold mirror has a reflective surface parallel to said principal optical plane.

17. The cross connect of claim 10, wherein said MEMS mirrors are tiltable about respective first axes to effect selective coupling through said fold mirror.

18. The cross connect of claim 17, wherein said MEMS mirrors are titable about respective second axes perpendicular to respective ones of said first axes.

19. The cross connect of claim 10, wherein said waveguides are coupled to free-space beams propagatnig in parallel.

20. The cross connect of claim 10, wherein said first set of free-space optics are arranged along an optical path extending in a principal optical plane and wherein said first linear array extends in a direction perpendicular to said principal optical plane.

21. A optical cross connect, comprising:

a concentrator having associated therewith at least three waveguides having ends arranged in a first linear array separated by a first spacing and being separated from each other by a second spacing larger than said first spacing away from said ends;

a free-space optical system coupled to all of said ends; and

a microelectromechanical system including an array of movable mirrors coupled to all of said ends through said free-space optical system.

22. The cross connect of claim 21, wherein said first spacing is no more than 50 μ

m.

23. The cross connect of claim 21, further comprising a substrate in which said waveguides are formed as planar waveguides in a curved pattern, said ends being formed on a first side of said substrate and a second side of said substrate being configured to couple said waveguides to respective ones of at least three optical fibers.

24. The cross connect of claim 21, wherein said free-space optical system is arranged along an optical axis extending in a principal optical plane and wherein said first linear array is arranged along a direction perpendicular to said principal optical plane.

25. The cross connect of claim 21, wherein said waveguides are optical fibers and further comprising a substrate formed with grooves formed in a curved pattern to align respective ones of said optical fibers.

26. The cross connect of claim 25, wherein said optical fibers are tapered toward said ends.

28. The cross connect of claim 27, wherein said plane of said MEMS array is inclined at 45°

with respect to said principal optical plane and said fold mirror has a reflective surface parallel to said principal optical plane.

29. The cross connect of claim 27, wherein said free-space optics includes a diffraction grating and wherein said array of movable mirrors is a two-dimensional array arranged in a waveguide direction and in a wavelength direction.

27. An optical cross connect, comprising:

an array of optical waveguides having ends and coupled to free-space beams propagating substantially parallel to a principal optical plane;

free-space optics disposed in an optical path parallel to said principal optically interacting with said free-space beams;

a micro electromechanical system (MEMS) array of movable mirrors disposed in a plane inclined to principal optical plane; and

a fold mirror reflectively coupling respective pairs of said mirrors.

30. An optical cross connect, comprising:

a plurality of optical waveguides arranged in an array and extending along parallel paths to waveguide ends thereof;

a collimating lens system optically coupled to said waveguide ends and including a field-flattening element; and

an array of micro electromechnical system (MEMS) mirrors optically coupled through said collimating lens system to said waveguide ends.

31. The optical cross connect of claim 30, further comprising:

a wavelength dispersive element coupled to said waveguide ends through said collimating lens system; and

a focusing lens interposed between said wavelength dispersive element and said array of MEMS mirrors and having a focus point on said array of MEMS mirrors.

32. The optical cross connect of claim 30, further comprising a fold mirror reflectively coupling pairs of said MEMS mirrors.

33. The optical cross connect of claim 30, further comprising:

a wavelength dispersive element coupled to said waveguide ends through said collimating lens system; and

a focusing lens interposed between said wavelength dispersive element and said array of MEMS mirrors and having a focus point on an optical path between said array of MEMS mirrors and said fold mirror.

34. The optical cross connect of claim 30, further comprising:

a wavelength dispersive element coupled to said waveguide ends through said collimating lens system; and

a focusing lens interposed between said wavelength dispersive element and said array of MEMS mirrors;

wherein a ratio between a focal length of said focusing lens and a focal length of said collimating lens system is between 10 and 100.

35. The optical cross connect of claim 34, wherein said ratio is between 20 and 50.

37. The cross connect of claim 36, wherein each of said wavelength cross connects includes an array of micro electromechanical system (MEMS) mirrors and free-space optics including a wavelength dispersive element.

38. The cross connect of claim 36, wherein said divider/combiners comprises power combiner/dividers.

39. The cross connect of claim 36, wherein said divider/combiners comprise interleavers.

36. An optical cross connect coupled to a plurality of optical waveguides carrying a plurality of wavelength multiplexed optical signals, comprising:

at least one stage of a plurality of optical divider/combiners each coupled on one side to a one of said optical waveguides and including on another side a plurality of ports; and

a plurality of wavelength cross connects each coupled to a respective one of said ports of each of said optical divider/combiners and configured to optically switch corresponding and different groups of wavelength components of said plurality of wavelength multiplexed optical signals.

40. A method of wavelength switching multi-wavelength signals conveyed on a plurality of fibers, comprising the steps of:

coupling light between said fibers and multi-wavelength free-space beams propagating in parallel in a linear array arranged parallel to a principal optical plane with spacings of no more than 50 μ

m;

spectrally coupling said multi-wavelength free-space beams and wavelength-separated free-space sub-beams;

positioning a two-dimensional array of tiltable mirrors to intercept respective ones of said sub-beams; and

selectively tilting said mirrors to selectively optically couple pairs of said fibers.

41. The method of claim 40, wherein said two-dimensional array of tiltable mirrors is formed in a common substrate and wherein said tilting includes electrically actuating said mirrors.

42. The method of claim 40, wherein said mirrors are tiltable about two respective orthogonal axes.