Patent ID: 7333732

Claim:
An apparatus comprising: a demodulator for demodulating an optical input signal having data modulated thereon according to a DPSK modulation format, said demodulator being configured to split said optical input signal onto first and second arms and provide first and second optical outputs; first and second photodetectors, said first photodetector being configured for providing a first electrical output in response to said first optical output being imparted thereon, said second photodetector being configured for providing a second electrical output in response to said second optical output being imparted thereon; an integrated clock and data recovery circuit coupled to first and second electrical outputs, said integrated clock and data recovery circuit being configured to provide a signal level output representative of a signal level of at least one of said first and second electrical outputs; a first dither circuit for establishing a demodulator dither signal; a controller configured for providing a demodulator setting signal in response to said signal level output; and a combiner for combining said demodulator dither signal and said demodulator setting signal as a demodulator control signal for controlling and dithering an optical path length of one of said first and second arms.