Reduction of MEMS mirror edge diffraction in a wavelength selective switch using servo-based rotation about multiple non-orthogonal axes
First Claim
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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Abstract
Effects of diffraction of a spectral beam from an edge of the micromirrors are reduced in order to optimize the passband in a wavelength selective switch. The effects of diffraction on the pass band may be reduced by using rotation of the micromirror about both the attenuation axis and the switching axis to achieve the desired level of attenuation. Peak coupling can be attained by dithering the micromirror about a dither axis that is tangent to a contour of constant attenuation using simultaneous rotation about the switching and attenuation axes. A power level of a spectral channel may be attenuated by rotating the channel micromirror with respect to an effective attenuation axis that is non-orthogonal to the dither axis through a combination of rotations about the switching axis and the attenuation axis.
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Citations
16 Claims
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1. Optical apparatus for switching multi-channel optical signals having spectral channels of different wavelengths, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of optimizing passband in optical apparatus for switching optical signals of a multi-channel optical signal having constituent spectral channels of different wavelengths between input and output ports, comprising:
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spatially separating said multi-channel optical signal from one of the input ports into spectral beams corresponding to the constituent spectral channels; focusing the separated spectral channels onto corresponding channel micromirrors that switch the focused spectral channels to one or more selected output ports; and dithering a particular channel micromirror with respect to a dither axis y′
that is substantially tangent to a contour of constant attenuation through a combination of rotations about a switching axis y and an attenuation axis x, andattenuating a power level of a spectral channel by rotating the particular channel micromirror with respect to an effective attenuation axis x′
through a combination of rotations about the switching axis y and the attenuation axis x, wherein the dither axis y′
is non-orthogonal to the effective attenuation axis x′
,whereby rotating the particular channel micromirror 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 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. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification