Patent ID: 7970289

Claim:
An optical receiver comprising: an input port to receive a modulated optical input signal having carrier frequencies separated by a channel spacing and carrying data corresponding to a modulation of the optical input signal; a decoder configured to split said input signal into two signal paths having a transit time difference by using at least a partially reflecting first mirror, said transit time difference defining a free spectral range (FSR) having passbands approximately centered at said carrier frequencies and an FSR bandwidth about equal to half the channel spacing, alter the FSR bandwidth by using at least an etalon disposed in a first of said signal paths, the altered FSR bandwidth being broader than half the channel spacing, provide a differentially demodulated signal having the altered FSR bandwidth to at least one of constructive and destructive outputs; and a data estimator configured to estimate said data by using at least the differentially demodulated signal having the altered FSR bandwidth that is provided at the at least one of the constructive and destructive outputs of the decoder.