Variable transmission multi-channel optical switch

• US 20020071627A1
• Filed: 09/20/2001
• Published: 06/13/2002
• Est. Priority Date: 09/22/2000
• Status: Active Grant

• Current Assignee: Lumentum Operations, LLC (Lumentum Holdings Inc.)
• Original Assignee: Movaz Networks, Inc. (ADTRAN Holdings, Inc.)
• Inventors: Smith, David A., Farhan, Fariborz, Golub, John E.
• Granted Patent: US 6,798,941 B2
• Time in Patent Office: Days
• US Class Current: 385/15
• CPC Class Codes: G02B 2006/12104 Mirror; Reflectors or the like
• 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 6/3512 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 6/3556 NxM switch, i.e. regular arrays of switches elements of matrix type constellation
• 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 6/359 of the position of the moving element itself during switching, i.e. without monitoring the switched beams
• 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 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 2011/0039 Electrical control
• CPC Class Codes: H04Q 2011/0043 Fault tolerance
• CPC Class Codes: H04Q 2011/0049 Crosstalk reduction; Noise; Power budget
• CPC Class Codes: H04Q 2011/0052 Interconnection of switches

Abstract

A multi-wavelength or white-light optical switch including an array of mirrors tiltable about two axes, both to control the switching and to provide variable power transmission through the switch, both for optimization and for power equalization between wavelength channels in a multi-wavelength signal. The output power of a channel is monitored, thereby allowing feedback adjustment of the transmitted power. The mirrors are preferably formed in a micro electromechanics system array to be tiltable in orthogonal directions and having electrostatically controlled tilting by two pairs of electrodes beneath the mirrors. Input power of the separate channels may also be monitored.

Claims

1. An optical switching system comprising:

at least one movable mirror for selectively coupling an optical signal from an input port to any of a plurality of output ports according to a position of said mirror;

an optical detector receiving a portion of light coupled to one of said output ports to measure an intensity of said light; and

a controller receiving an output of said optical detector and in response adjusting said position of said mirror to effect control of said intensity.

2. The system of claim 1 comprising a plurality of said mirrors, a plurality of said optical signals from a plurality of said input ports, and a plurality of said optical detectors receiving portions of light coupled to each of said mirrors and wherein said controller adjust said position of at least one of said mirrors to control relative sizes of two of said intensities.

3. The system of claim 2 further comprising a dispersive element for spatially separating said plurality of multi-wavelength signals into said plurality of said optical signals.

12. The cross connect system of claim 1 further comprising a second optical detector receiving a portion of light coupled to one of said input ports.

4. A cross connect system for selectively and optically interconnecting a plurality of optical input channels to a plurality of optical output channels, comprising:

a controller;

an optical cross connect controlled by said controller and capable of switching signals from one of said input channels to a selected one of said output channels under control of said controller; and

an optical power monitor tapping portions of power of said output channels to determine intensities of optical signals on each of said output channels;

wherein said controller in response to intensities determined by said optical power monitor fractionally adjusts one or more optical power transmission coefficients between one of said input channels and said selected one of said output channels of said optical cross connect.

5. The cross connect system of claim 4, wherein said optical cross connect includes a plurality of tiltable mirrors for reflecting light from one of said input channels to one of said output channels and wherein said controller control tilt angles of said mirrors select said output channels and to fractionally adjust said power transmission coefficients.

6. The cross connect system of claim 5, wherein said tiltable mirrors are included in a micro electromechanical system array.

7. The cross connect system of claim 5,

wherein said input channels are included as wavelength components in a plurality of multi-wavelength input signals, and

further comprising a dispersive element dispersing said multi-wavelength input signals into spatially separated ones of wavelength components incident upon respective ones of said mirrors.

8. The cross connect system of claim 6, wherein said mirrors are tiltable along a first direction and along an orthogonal second direction.

9. The cross connect system of claim 8, wherein said controller controls a switching route between said input channels and said output channels by tilting said mirrors only along said first direction.

10. The cross connect system of claim 9, wherein said control tilts said mirrors along said second direction to effect one of transmission optimization and power transmission through said system.

11. The cross connect system of claim 8, wherein said controller controls a switching route between said input channels and said output channels by tilting said mirrors along both said first direction and said second direction.

14. The cross connect of claim 13, further comprising a fold mirror positioned to reflectively couple respective pairs of said tertiary beams.

15. The cross connect of claim 13, wherein tilting of said mirrors about said first axes effects switching from one of said primary input beams to a selected one of said primary output beams.

16. The cross connect of claim 13, wherein tilting of said mirrors about said second axes effects control of transmissivity through said cross connect.

17. The cross connect of claim 16, wherein tilting of said mirrors about said first axes also effects control of transmissivity through said cross connect.

18. The cross connect of claim 13, further comprising an optical power monitor measuring output power of each wavelength component of each of said primary output beams and therefrom controlling said tiliting of said mirrors to effect a fractional change in power transmission through said cross connect.

19. The cross connect of claim 18, further comprising a second optical power monitor measuring input power of each wavelength component of said input beams.

13. A wavelength division multiplexing cross connect for interconnecting selected wavelength components in a plurality of primary input beams to a plurality of primary output beams, comprising:

a wavelength-dispersive element receiving from an output side of said cross connect said plurality of primary input beams and said plurality of primary output beams to thereby create a two-dimensional array of secondary beams arranged in one direction according said primary beams and in a second direction according to wavelength; and

a two-dimensional array of mirrors tiltable about respective first and second axes and positioned to receive respective different ones of said secondary beams to reflect therefrom respective tertiary beams;

20. An optical cross connect comprising:

a plurality of mirrors arranged along an axis in a micro electromechanical system, tiltable about respective first axes and second axes inclined to said first axes, and positioned to receive a plurality of beams propagating within a plane, wherein each of said mirrors is supported by a gimbal structure comprising a frame supported on a support structure through a first torsion beam extending along said first axis, and

wherein said mirror is supported through a second torsion beam extending along said second axis; and

electrostatic actuators formed by said mirrors and underlying electrodes to independently tilt a selected one of said mirrors about its first axis and its second axis, wherein

first ones of said electrodes are arranged in pairs in opposition to said frame on opposite sides of said first axes, and

second ones of said electrodes are arranged in pairs in opposition to said mirror on opposite sides of said second axes.

21. The cross connect of claim 20, wherein said mirrors are arranged in a two-dimensional array.

22. The cross connect of claim 20, wherein said mirrors are incorporated into a micro electromechanical systems array.

23. The cross connect of claim 20, further comprising a spectrally dispersive element for spatially separating at least one multi-wavelength optical signal into said plurality of beams.

25. The method of claim 24, wherein said switching network is an all-optical switching network.

26. The method of claim 24, wherein said optical switching network includes a plurality of movable mirrors and wherin said transmission coefficient is adjusted by moving at least one of said movable mirrrors.

27. The method of claim 26, wherein said connecting step includes moving at least one of said movable mirrors.

28. The method of claim 26, wherein said at least one of said movable mirrors is also used in said connecting step.

29. The method of claim 24 further comprising spectrally and spatially dispersing at least one multi-wavelength signal into said optical communications channels.

30. The method of claim 24 further comprising monitoring a power on at least one of said input communications channels.

24. A method of interconnecting an input optical communications channel to a plurality of output optical communications channels comprising the steps of:

connecting said input optical communications channel to a selected one of said output optical communications channels through an optical switching network;

monitoring a power on said selected one output optical communications channel; and

in response to said monitoring step, adjusting a transmission coefficient through said switching network of said one input optical communications channel to said selected one output optical communications channel.

31. A method for controlling an optical cross connect which includes a plurality of individually controllable trasnmissive elements comprising:

adjusting said transmissive elements to effect selective optical coupling between a plurality of input beams to a plurality of output beam monitoring optical powers on said plurality of output beams; and

in response to said monitoring step, adjusting a transmission of said transmissive elements to achieve a predetermined relationship of optical powers between said plurality of output beams.

32. The method of claim 31, wherein said transmissive elements are rotatable mirrors and said adjusting includes rotating said mirrors.

33. The method of claim 31, additionally comprising monitoring optical powers on said plurality of input beams.

34. The method of claim 31, wherein said input and output beams are wavelength-separated components of a plurality of multi-wavelength input and output signals.

35. A method of interconnecting an input optical communications channel to a selected one of a plurality of optical output channels wherein said output communication channels have ports aligned along an axis and wherein at least one mirror is tiltable along a first direction to switch said optical input channel to any of said plurality of optical output channels and is tiltable along a second direction, wherein when said input optical channel is to be switched to a first one of said output channels to a second one of said output channels separated along said axis by a third output channel, said method comprises the sequential steps of:

tilting said mirror at least partially along said first direction to move an output beam away from said first optical input channel in a direction away from said axis;

tilting said mirror at least partially along said second direction; and

tilting said mirror along at least partially along said first direction to move said output beam toward said second optical output beam in a direction towards said axis.