Patent ID: 7574079

Claim:
A method for dither control of a micromirror using a servo control loop in an optical switching apparatus, comprising: a) deflecting an optical beam from a first optical component of the optical switching apparatus to a second optical component with a micromirror; b) detecting an optical signal associated with a degree of coupling of the optical beam to the second optical component; c) applying a dither tone to an output driver that controls a position of the micromirror, wherein the dither tone includes two or more frequency components, including a first component and a second component; d) producing an output signal proportional to the optical signal; e) filtering the output signal in parallel with two or more band-pass filters including first and second band-pass filters to produce first and second band-pass outputs, wherein the first band-pass filter is characterized by a pass band centered on the frequency of the first component of the dither tone and the second band-pass filter is characterized by a pass band centered on the frequency of the second component of the dither tone; f) comparing the first and second band-pass outputs to each other and generating a comparison output, wherein the comparison output is equal to a sum of the first and second band-pass outputs if the first and second band-pass outputs are within a predetermined range of agreement, wherein the comparison output is equal to zero if the first and second band-pass outputs are not within the predetermined range of agreement; g) integrating the comparison output to produce one or more integrated signals; and h) driving the output driver using the one or more integrated signals.