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Reduction of MEMS mirror edge diffraction in a wavelength selective switch using servo-based rotation about multiple non-orthogonal axes

  • US 7,362,930 B2
  • Filed: 08/31/2006
  • Issued: 04/22/2008
  • Est. Priority Date: 04/11/2005
  • Status: Expired due to Fees
First Claim
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1. Optical apparatus for switching multi-channel optical signals having spectral channels of different wavelengths, comprising:

  • a plurality of input and output ports for optical signals having one or more of said spectral channels;

    an optical beam expander and relay system adapted to receive the optical signals from one or more of the input ports, the optical beam expander and relay system being formed to convert the optical signals to spectral beams having a predetermined elongated beam profile;

    a wavelength separator for spatially separating the spectral beams into constituent spectral channels; and

    an array of channel micromirrors, each channel micromirror of the array being positioned to receive one of said constituent spectral channels, the micromirrors being rotatable about a switching axis y to switch said one spectral channel to a selected output port;

    wherein each channel micromirror is rotatable about an attenuation axis x to vary coupling of said one spectral channel to the selected output port to control a power level of the spectral channel output at such selected port, wherein the attenuation axis is different from the switching axis,wherein each channel micromirror is configured to dither with respect to a dither axis y′

    that is substantially tangent to a contour of constant attenuation by rotating simultaneously about the switching axis y and the attenuation axis x, wherein the dither axis y′

    is non-orthogonal to an effective attenuation axis x′

    , andwherein each channel micromirror is configured to attenuate the power level by rotating the mirror with respect to the effective attenuation axis x′

    through a combination of rotations about the switching axis y and the attenuation axis x,wherein rotating the mirrors about the dither axis y′ and

    the effective attenuation axis x′

    reduces an increase in signal intensity of a spectral channel near side edges of a passband for that spectral channel relative to a central portion of the passband due to diffraction of that spectral channel from an edge of that spectral channel'"'"'s associated micromirror, wherein the edge is substantially parallel to the attenuation axis.

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