FLEX SPECTRUM WSS

• US 20090028503A1
• Filed: 08/16/2007
• Published: 01/29/2009
• Est. Priority Date: 04/11/2005
• Status: Active Grant

• Current Assignee: Capella Photonics, Inc. (Nokia Corporation)
• Original Assignee: Capella Photonics, Inc. (Nokia Corporation)
• Inventors: Davis, Joseph E., Garrett, Mark H.
• Granted Patent: US 7,756,368 B2
• Time in Patent Office: Days
• US Class Current: 385/18
• CPC Class Codes: G02B 6/2706 as bulk elements, i.e. free space arrangements external to a light guide, e.g. polarising beam splitters
• CPC Class Codes: G02B 6/29311 Diffractive element operating in transmission
• CPC Class Codes: G02B 6/29382 including at least adding or dropping a signal, i.e. passing the majority of signals
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• 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 6/3588 of the processed beams, i.e. controlling during switching of orientation, alignment, or beam propagation properties such as intensity, size or shape
• 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: G02B 6/4246 Bidirectionally operating package structures

Abstract

Switching optical signals containing a plurality of spectral channels characterized by a predetermined channel spacing is described. A selected beam deflector array may be selected from among a plurality of available beam deflector arrays configured to accommodate spectral channels of different channel spacings. The selected beam deflector array is configured to accommodate spectral channels of the predetermined channel spacing. The spectral channels are selectively optically coupled to the selected beam deflector array, which selectively optically couples the spectral channels between one or more input ports and one or more output ports.

Claims

1. Optical switching apparatus, comprising:

one or more input ports and one or more output ports;

a wavelength separator optically coupled to the input ports and the output ports; and

two or more channel beam deflector arrays configured to be selectively optically coupled to the wavelength separator, each channel beam deflector array comprising one or more channel beam deflectors, each array being characterized by a different deflector spacing selected for a given channel spacing of constituent spectral channels, wherein the wavelength separator and channel beam deflectors are configured to facilitate selective coupling of a spectral channel between the output ports and a selected input port or vice versa; and

an array selector configured to selectively optically couple the wavelength separator to a selected array of the two or more beam deflector arrays.

2. The apparatus of claim 1, wherein the beam deflector arrays are in substantially fixed positions relative to the wavelength separator and the array selector is configured for selective optical coupling between the wavelength separator and selected array by selective optical deflection of an optical signal containing the constituent spectral channels.

3. The apparatus of claim 2 wherein the array selector includes a reflective element optically coupled to the wavelength separator, wherein the reflective element is configured to rotate about an axis to selectively optically couple the wavelength separator to the selected array.

4. The apparatus of claim 3 wherein the two or more beam deflector arrays are not co-planar or are non-parallel.

5. The apparatus of claim 1 wherein the array selector is configured to selectively optically couple the wavelength separator to the selected one of the two or more beam deflector arrays by selectively moving the selected array into a position wherein the selected array is optically coupled to the wavelength separator.

6. The apparatus of claim 5 wherein the two or more beam deflector arrays are substantially parallel to each other.

7. The apparatus of claim 6 wherein the two or more beam deflector arrays are substantially co-planar with each other.

8. The apparatus of claim 1 wherein each channel beam deflector array is an array of channel micromirrors, wherein each channel micromirror is rotatable about a switching axis.

9. The apparatus of claim 8, wherein each channel micromirror is configured to rotate about an attenuation axis that is different from the switching axis.

10. The apparatus of claim 9 further comprising a control system for controlling rotation of the channel micromirrors about the switching and attenuation axes, the control system being responsive to predetermined values corresponding to rotational positions of a channel micromirror about the switching axis for switching a spectral channel to different output ports, and control electronics responsive to a measurement of power in a spectral channel for controlling the rotation of the channel micromirror about the attenuation axis for a selected power level in said spectral channel.

11. Optical apparatus for switching multi-channel optical signals having spectral channels of different wavelengths, comprising:

fiber coupled collimators providing a plurality of input and output ports for optical signals having one or more of said spectral channels;

an anamorphic system receiving an optical signal from an input port of the fiber collimators and being formed to convert the optical signal to a beam having a predetermined beam profile;

a diffraction grating for spatially separating the beam into constituent spectral channel beams;

focusing optics for converting the constituent spectral channels into channel beams having an elongated channel beam profile;

two or more arrays of biaxial channel micromirrors, each array being characterized by a different mirror spacing selected for a given channel spacing of the constituent spectral channels, the micromirrors in each array having an elongated shape compatible with said elongated channel beam profile, and each micromirror of the array being positioned to receive one of said constituent spectral channels, the micromirrors being rotatable about a first switching axis to switch said one spectral channel to a selected output port, and being rotatable about a second attenuation axis to vary the coupling of the switched spectral channel to the selected output port to control the power level of the spectral channel output at such selected port; and

an array selector configured to selectively optically couple the wavelength separator to a selected array of the two or more arrays of biaxial channel micromirrors.

12. The apparatus of claim 11, wherein the arrays of biaxial channel micromirrors are in substantially fixed positions relative to the wavelength separator and the array selector is configured for selective optical coupling between the wavelength separator and beam deflector array by selective optical deflection of the spectral channel.

13. The apparatus of claim 12 wherein the array selector includes a reflective element optically coupled to the wavelength separator, wherein the reflective element is configured to rotate about an axis to selectively optical couple the wavelength separator to the selected array.

14. The apparatus of claim 13 wherein the two or more beam deflector arrays are not co-planar or are non-parallel.

15. The apparatus of claim 11 wherein the array selector is configured to selectively optically couple the wavelength separator to the selected one of the two or more beam deflector arrays by selectively moving the selected array into a position wherein the selected array is optically coupled to the wavelength separator.

16. The apparatus of claim 15 wherein the two or more beam deflector arrays are substantially parallel to each other.

17. The apparatus of claim 16 wherein the two or more beam deflector arrays are substantially co-planar with each other.

18. The apparatus of claim 17 further comprising a control system for controlling rotation of the channel micromirrors about the switching and attenuation axes, the control system being responsive to predetermined values corresponding to rotational positions of a channel micromirror about the switching axis for switching a spectral channel to different output ports, and control electronics responsive to a measurement of power in a spectral channel for controlling the rotation of the channel micromirror about the attenuation axis for a selected power level in said spectral channel.

19. A method for switching optical signals containing a plurality of spectral channels characterized by a predetermined channel spacing, comprising:

selecting from among a plurality of available beam deflector arrays configured to accommodate spectral channels of different channel spacings a selected beam deflector array configured to accommodate spectral channels of the predetermined channel spacing;

selectively optically coupling the plurality of spectral channels to the selected beam deflector array; and

selectively optically coupling the spectral channels between one or more input ports and one or more output ports or vice versa using the particular beam deflector array.

20. The method of claim 19, wherein the plurality of beam deflector arrays are in substantially fixed positions relative to a wavelength separator and selectively optically coupling the plurality of spectral channels to the selected beam deflector array includes selectively optically deflecting the spectral channels toward the selected beam deflector array.

21. The method of claim 19 wherein selectively optically coupling the plurality of spectral channels to the selected beam deflector array includes moving the selected array into a position wherein the selected array is optically coupled to the spectral channels.

22. The method of claim 21 wherein the plurality of beam deflector arrays are substantially parallel to each other.

23. The method of claim 22 wherein the two or more beam deflector arrays are substantially co-planar with each other.

24. The method of claim 19 wherein each channel beam deflector array is an array of channel micromirrors, wherein each channel micromirror is rotatable about a switching axis.

25. The method of claim 24, wherein each channel micromirror is configured to rotate about an attenuation axis that is different from the switching axis.

26. The method of claim 25 further comprising controlling rotation of the channel micromirrors about the switching and attenuation axes in response to predetermined values corresponding to rotational positions of a channel micromirror about the switching axis for switching a spectral channel to different output ports, measuring of power in a spectral channel and controlling the rotation of the channel micromirror about the attenuation axis for a selected power level in said spectral channel.

27. The method of claim 19 wherein selectively optically coupling the plurality of spectral channels to the selected beam deflector array includes converting the optical signals from one or more input ports into beams having predetermined beam profiles by anamorphically expanding the beams in orthogonal directions;

spatially separating said beams into constituent spectral channel beams having elongated channel beam profiles; and

focusing the separated spectral channel beams as elongated spots onto corresponding channel micromirrors of the selected beam deflector array that switch the focused spectral channel beams to one or more selected output ports, the channel micromirrors having an elongated shape and size that is compatible with the shape and size of said elongated spots, said focusing comprising aligning said elongated spots to be centered on said corresponding micromirrors.

28. The method of claim 27 further comprising reflecting the optical signals from a port mirror, the rotational position of which moves the focused elongated spots of the constituent spectral channels across the micromirrors, determining the locations of the focused elongated spots on the channel micromirrors, and maintaining the elongated spots centered on the micromirrors.

29. The method of claim 28, wherein determining the locations of the focused elongated spots on the channel micromirrors comprises detecting the position of a reference beam injected into an input port with said optical signals on a detector, and wherein said maintaining comprises controlling the port mirror to maintain the reference beam at a predetermined location on the detector.

30. The method of claim 28 further comprising modulating the optical signals with dither tones of a predetermined frequency, detecting the dither tone modulation on spectral channels at an output port, and controlling the channel micromirrors for a predetermined detected dither tone modulation condition.

31. The method of claim 30, wherein said modulating comprises modulating the spectral channels with out-of-phase dither tones, and said controlling comprises controlling for a detected dither modulation at a multiple of the predetermined frequency.

32. The method of claim 28 further comprising modulating the optical signals with dither tones of different predetermined frequencies, detecting the dither tone modulation on spectral channels at an output port, and identifying the spectral channels coupled to ports from said predetermined dither tone frequencies.

33. The method of claim 28, wherein the port mirror is biaxial, and the method further comprises dithering orthogonal axes of the port mirror, measuring the power level at different combinations of angular positions of said axes, using a feed forward algorithm based on a predetermined relationship between power and rotation angle of each axis of said port mirror to predict the rotation angles that provide optimal coupling efficiency, and rotating the port mirror to said rotational angles to achieve optimal coupling efficiency.

34. The method of claim 28 further comprising dithering orthogonal switching and attenuation axes of a channel micromirror;

measuring the power level at different combinations of angular positions of said port mirror and said channel micromirror, using a feed forward algorithm based on said predetermined relationship for said port mirror and on another predetermined relationship between power and rotation angle of each axis of the channel micromirror to predict the rotation angles that provide optimal coupling efficiency and a selected power or attenuation level, and rotating said channel mirror and said port mirror to such rotation angles to achieve said optimal coupling efficiency or a selected power or attenuation level.

35. The method of claim 27 further comprising rotating a channel micromirror about a first axis to switch a spectral channel to a selected output port, and rotating the channel micromirror about a second orthogonal axis to control the power of the spectral channel coupled to the output port.

36. The method of claim 35 further comprising reducing the power in the spectral channel at a first port to a minimum power level by rotating the micromirror about the second orthogonal axis;

switching the spectral channel to a second port by rotating the channel micromirror about the first axis while maintaining said minimum power level;

increasing said power to a low power level by rotating the channel micromirror about the orthogonal axis;

optimizing the coupling of the spectral channel at the second port at said low power level by rotating about the first axis; and

increasing the power level to a selected power level by rotating the channel micromirror about the orthogonal axis.

37. The method of claim 35 further comprising measuring the power of individual spectral channels of said multi-channel optical signal, and applying feedback control to the orthogonal axis of the channel micromirrors for a predetermined power level of said individual spectral channels.

38. The method of claim 27 wherein said converting comprises applying different magnifications to said beams in orthogonal directions, and selecting said magnifications such that said focused elongated spots have a shape and size on the micromirrors that optimizes optical passband.

39. The method of claim 38, wherein said selecting comprises selecting said magnifications for a spot size on a micromirror that reduces aerodynamic cross-talk.

40. The method of claim 38, wherein said selecting comprises selecting said magnifications for a spot size of a spectral beam reflected from a micromirror to said selected output port that reduces coupling and cross-talk from said reflected beam to an adjacent output port.

41. The method of claim 27 further comprising rotating a channel micromirror about both a first and a second axis to control the power of the spectral channel coupled to the output port.

42. The method of claim 19 wherein selectively optically coupling the plurality of spectral channels to the selected beam deflector array includes hitlessly switching one or more spectral channels between the one or more input ports and one or more of the output ports or vice versa.