Reconfigurable optical add-drop multiplexers employing polarization diversity

• US 6,760,511 B2
• Filed: 02/14/2002
• Issued: 07/06/2004
• Est. Priority Date: 03/19/2001
• Status: Expired

• Current Assignee: Capella Photonics, Inc. (Nokia Corporation)
• Original Assignee: Capella Photonics, Inc. (Nokia Corporation)
• Inventors: Wilde, Jeffrey P., Polynkin, Pavel G., Garrett, Mark H., Mansuripur, Masud
• Primary Examiner(s): NGO, HUNG NHAT
• Application Number:
  US10/076,145
• Publication Number:
  US 20020131691A1
• Time in Patent Office: 873 Days
• Field of Search: 385/11, 385/37, 385/24, 385/34
• US Class Current: 385/24
• 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 6/29383 Adding and dropping
• CPC Class Codes: G02B 6/29385 Channel monitoring, e.g. by tapping channel monitoring in optical transmission systems H04B10/07
• CPC Class Codes: G02B 6/29391 Power equalisation of different channels, e.g. power flattening
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02B 6/32 having lens focusing means positioned between opposed fibre ends with lens being an integral part of the single fibre end G02B6/262
• CPC Class Codes: G02B 6/34 utilising prism or grating G02B6/293 takes precedence
• 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 6/3586 Control or adjustment details, e.g. calibrating testing optical equipment G01M11/00
• 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 6/3592 Means for removing polarization dependence of the switching means, i.e. polarization insensitive switching light guides coupling with polarization selective and adjusting means G02B6/27

Abstract

This invention provides a novel wavelength-separating-routing (WSR) apparatus that uses a diffraction grating to separate a multi-wavelength optical signal by wavelength into multiple spectral channels, which are focused onto an array of corresponding channel micromirrors. The channel micromirrors are individually controllable and continuously pivotable to reflect the spectral channels into selected output ports. As such, the inventive WSR apparatus is capable of routing the spectral channels on a channel-by-channel basis and coupling any spectral channel into any one of the output ports. The WSR apparatus of the invention may further employ a polarization diversity scheme, whereby polarization-sensitive effects become inconsequential and insertion loss is minimized. The WSR apparatus of the invention may additionally be equipped with servo-control and channel equalization capabilities. The WSR apparatus of the invention can be used to construct a novel class of dynamically reconfigurable optical add-drop multiplexers (OADMs) for WDM optical networking applications.

Claims

1. An optical apparatus, comprising:

fiber collimators providing an input port for a multi-wavelength optical signal and a plurality of output ports;

a polarization-displacing unit that decomposes said multi-wavelength optical signal into first and second polarization components;

a polarization-rotating unit that rotates a polarization of the second polarization component to be substantially parallel to a polarization of the first polarization component;

a wavelength-separator that separates said first and second polarization components by wavelength into first and second sets of optical beams; and

an array of channel micromirrors positioned to reflect said first and second sets of optical beams such that said reflected first and second sets of optical beams arc recombined by wavelength into reflected spectral channels by said polarization-rotating unit and said polarization-displacing unit;

wherein said polarization-displacing unit comprises a polarization-displacing element in optical communication with said input port and said output ports, and

wherein said polarization-rotating unit comprises a polarization-rotating element, in optical communication with said polarization-displacing clement.

2. The optical apparatus of claim 1, wherein said polarization-displacing unit comprises a polarization-displacing element in optical communication with said input port and said output ports.

3. An optical apparatus, comprising:

fiber collimators providing an input port for a multi-wavelength optical signal and a plurality of output ports;

a polarization-displacing unit that decomposes said multi-wavelength optical signal into first and second polarization components;

a polarization-rotating unit that rotates a polarization of the second polarization component to be substantially parallel to a polarization of the first polarization component;

a wavelength-separator that separates said first and second polarization components by wavelength into first and second sets of optical beams; and

an array of channel micromirrors positioned to reflect said first and second sets of optical beams such that said reflected first and second sets of optical beams are recombined by wavelength into reflected spectral channels by said polarization-rotating unit and said polarization-displacing unit;

wherein said polarization-displacing unit comprises a plurality of polarization-displacing elements in correspondence with said input port and said output ports.

4. The optical apparatus of claim 3, wherein said polarization-displacing element comprises an element selected from the group consisting of birefringent beam displacers and polarizing-beam-splitting elements.

5. The optical apparatus of claim 3, wherein said polarization-rotating unit comprises a plurality of polarization-rotating elements in correspondence with said polarization-displacing elements.

6. The optical apparatus of claim 5, wherein each polarization-rotating element comprises an element selected from the group consisting of half-wave plates, Faraday rotators, and liquid crystal rotators.

7. An optical apparatus, comprising:

fiber collimators providing an input port for a multi-wavelength optical signal and a plurality of output ports;

a polarization-displacing unit that decomposes said multi-wavelength optical signal into first and second polarization components;

a polarization-rotating unit that rotates a polarization of the second polarization component to be substantially parallel to a polarization of the first polarization component;

a wavelength-separator that separates said first and second polarization components by wavelength into first and second sets of optical beams;

an array of channel micromirrors positioned to reflect said first and second sets of optical beams such that said reflected first mid second sets of optical beams are recombined by wavelength into reflected spectral channels by said polarization-rotating unit and said polarization-displacing unit; and

a beam-modifying unit for providing anamorphic beam magnification of said first and second polarization components and anamorphic beam demagnification of said reflected first and second sets of optical beams.

8. The optical apparatus of claim 7, wherein beam-modifying unit comprises one or more cylindrical lenses.

9. The optical apparatus of claim 7, wherein beam-modifying unit comprises one or more prisms.

10. An optical apparatus, comprising:

fiber collimators providing an input port for a multi-wavelength optical signal and a plurality of output ports;

a polarization-displacing unit that decomposes said multi-wavelength optical signal into first and second polarization components;

a polarization-rotating unit that rotates a polarization of the second polarization component to be substantially parallel to a polarization of the first polarization component;

a wavelength-separator that separates said first and second polarization components by wavelength into first and second sets of optical beams;

an array of channel micromirrors positioned to reflect said first and second sets of optical beams such that said reflected first and second sets of optical beams are recombined by wavelength into reflected spectral channels by said polarization-rotating unit and said polarization-displacing unit; and

an array of collimator-alignment mirrors in optical communication with said fiber collimators and said polarization-displacing unit for adjusting an alignment of said multi-wavelength optical signal from said input port and for directing said reflected spectral channels into said output ports.

11. The optical apparatus of claim 10, wherein each collimator-alignment mirror is rotatable about at least one axis.

12. An optical apparatus, comprising:

fiber collimators providing an input pod for a multi-wavelength optical signal and a plurality of output pods;

a polarization-displacing unit that decomposes said multi-wavelength optical signal into first and second polarization components;

a polarization-rotating unit that rotates a polarization of the second polarization component to be substantially parallel to a polarization of the first polarization component;

a wavelength-separator that separates said first and second polarization components by wavelength into first and second sets of optical beams; and

an array of channel micromirrors positioned to reflect said first and second sets of optical beams such that said reflected first and second sets of optical beams are recombined by wavelength into reflected spectral channels by said polarization-rotating unit and said polarization-displacing unit;

wherein said polarization-displacing unit comprises a polarizing beam splitter and a first beam-deflecting unit.

13. The optical apparatus of claim 12, wherein said first beam-deflecting unit comprises an array of first mirrors that are individually adjustable to control positions of said second polarization component and said reflected first set of optical beams.

14. The optical apparatus of claim 13, further comprising a second beam-deflecting unit, in optical communication with said first polarization component and said reflected second set of optical beams, said second beam-deflecting unit comprising an array of second mirrors that are individually adjustable.

15. An optical apparatus, comprising:

fiber collimators providing an input port for a multi-wavelength optical signal and a plurality of output ports;

a polarization-displacing unit that decomposes said multi-wavelength optical signal into first and second polarization components;

a polarization-rotating unit that rotates a polarization of the second polarization component to be substantially parallel to a polarization of the first polarization component;

a wavelength-separator that separates said first and second polarization components by wavelength into first and second sets of optical beams;

an array of channel micromirrors positioned to reflect said first and second sets of optical beams such that said reflected first and second sets of optical beams are recombined by wavelength into reflected spectral channels by said polarization-rotating unit and said polarization-displacing unit; and

a servo-control assembly, including a spectral monitor for monitoring optical power lever of said reflected spectral channels and a processing unit responsive to said optical power levels for controlling said channel micromirrors.

16. The optical apparatus of claim 15, wherein said servo-control assembly controls said channel micromirrors to maintain said optical power levels at a predetermined value.

17. An optical apparatus, comprising:

fiber collimators providing an input port for a multi-wavelength optical signal and a plurality of output ports;

a polarization-displacing unit that decomposes said multi-wavelength optical signal into first and second polarization components;

a polarization-rotating unit that rotates a polarization of the second polarization component to be substantially parallel to a polarization of the first polarization component;

a wavelength-separator that separates said first and second polarization components by wavelength into first and second sets of optical beams; and

an array of channel micromirrors positioned to reflect said first and second sets of optical beams such that said reflected first and second sets of optical beams are recombined by wavelength into reflected spectral channels by said polarization-rotating unit arid said polarization-displacing unit;

wherein each channel micromirror is pivotable about two axes; and

wherein said fiber collimators are arranged in a two-dimensional array.

18. An optical apparatus, comprising:

fiber collimators providing an input port for a multi-wavelength optical signal arid a plurality of output ports;

a polarization-displacing unit that decomposes said multi-wavelength optical signal into first and second polarization components;

a polarization-rotating unit that rotates a polarization of the second polarization component to be substantially parallel to a polarization of the first polarization component;

a wavelength-separator that separates said first and second polarization components by wavelength into first and second sets of optical beams; and

an array of channel micromirrors positioned to reflect said first and second sets of optical beams such that said reflected first and second sets of optical beams arc recombined by wavelength into reflected spectral channels by said polarization-rotating unit and said polarization-displacing unit;

wherein said array of channel micromirrors reflects said first and second sets of optical beams so as to couple said beams into selected output ports.

19. An optical apparatus, comprising:

fiber collimators providing an input pod for a multi-wavelength optical signal and a plurality of output ports;

a polarization-displacing unit that decomposes said multi-wavelength optical signal into first and second polarization components;

a polarization-rotating unit that rotates a polarization of the second polarization component to be substantially parallel to a polarization of the first polarization component;

a wavelength-separator that separates said first and second polarization components by wavelength into first and second sets optical beams; and

an array of channel micromirrors positioned to reflect said first and second sets of optical beams such that said reflected first and second sets of optical beams are recombined by wavelength into reflected spectral channels by said polarization-rotating unit and said polarization-displacing unit;

wherein said fiber collimators are arranged in a one-dimensional array.

20. An optical apparatus, comprising:

fiber collimators providing an input port for a multi-wavelength optical signal and a plurality of output ports;

a polarization-displacing unit that decomposes said multi-wavelength optical signal into first and second polarization components;

a polarization-rotating unit that rotates a polarization of the second polarization component to be substantially parallel to a polarization of the first polarization component;

a wavelength-separator that separates said first and second polarization components by wavelength into first and second sets of optical beams;

an array of channel micromirrors positioned to reflect said first and second sets of optical beams such that said reflected first and second sets of optical beams are recombined by wavelength into reflected spectral channels by said polarization-rotating unit and said polarization-displacing unit; and

a beam-focuser for focusing said first and second sets of optical beams onto said channel micromirrors.

21. A method of dynamic routing of a multi-wavelength optical signal in a polarization diversity arrangement comprising:

decomposing said multi-wavelength optical signal into first and second polarization components;

providing an anamorphic beam magnification to said first and second polarization components, respectively;

rotating a polarization of said second polarization component to be substantially parallel to a polarization of the first polarization component;

separating said first and second polarization components by wavelength respectively into first and second sets of optical beams;

focusing said first and second sets of optical beams onto an array of micromirrors;

dynamically controlling said micromirrors to reflect said first and second sets of optical beams into selected output ports;

rotating a polarization of said reflected First, set of optical beams by approximately 90-degrees; and

recombining said reflected first and second sets of optical beams by wavelength into reflected spectral channels.

22. The method of claim 21 further comprising the step of monitoring said optical power levels at a predetermined value.

23. A method of dynamic routing of a multi-wavelength optical signal in a polarization diversity arrangement, comprising:

decomposing said multi-wavelength optical signal into first and second polarization components;

rotating a polarization of said second polarization component to be substantially parallel to a polarization of the first polarization component;

separating said first, and second polarization components by wavelength respectively into first and second sets of optical beams;

focusing said first and second sets of optical beams onto an array of micromirrors;

dynamically controlling said micromirrors to reflect said first and second sets of optical beams into selected output ports;

rotating a polarization of said reflected first set of optical beams by approximately 90-degrees;

recombining said reflected first and second sets of optical beams by wavelength into reflected spectral channels

monitoring optical power levels of said reflected spectral channels coupled into said output pods; and

providing Feedback control of said micromirrors.

24. The method of claim 23 further comprising the step of maintaining said optical power levels at a predetermined value.

25. A method of dynamic routing of a multi-wavelength optical signal in a polarization diversity arrangement, comprising:

adjusting an alignment of said multi-wavelength optical signal;

decomposing said multi-wavelength optical signal into first and second polarization components;

rotating a polarization of said second polarization component It) be substantially parallel to a polarization of the first polarization component;

separating said first and second polarization components by wavelength respectively into U) first and second sets of optical beams;

focusing said first and second sets of optical beams onto an array of micromirrors dynamically controlling said micromirrors to reflect said first and second sets of optical beams into selected output ports;

rotating a polarization of said reflected first set of optical beams by approximately 90-degrees; and

recombining said reflected first and second sets of optical beams by wavelength into reflected spectral channels.

26. The method of claim 25 further comprising the step of coupling of said reflected spectral channels into selected output ports.

27. A method of dynamic routing of a multi-wavelength optical signal in a polarization diversity arrangement, comprising:

decomposing said multi-wavelength optical signal into first and second polarization components;

adjusting a relative alignment between said first and second polarization components;

rotating a polarization of said second polarization component to be substantially parallel to a polarization of the first polarization component;

separating said first and second polarization components by wavelength respectively into first and second sets of optical beams;

focusing said first and second sets of optical beams onto an array of micromirrors;

dynamically controlling said micromirrors to reflect said first awl second sets of optical beams into selected output pods;

rotating a polarization of said reflected first set of optical beams by approximately 90-degrees; and

recombining said reflected first and second sets of optical beams by wavelength into reflected spectral channels.

28. The method of claim 27 further comprising the step of adjusting a relative alignment between said reflected first and second sets of optical beams.