Patent ID: 7769305

Claim:
In a coherent optical receiver, a high speed digital signal processor (DSP) for digitally processing at least two multi-bit sample streams of a received optical signal, the digital signal processor comprising: a Fast Fourier Transform (FFT) filter for processing the at least two multi-bit sample streams to compute an array {R A X } representative of a spectrum of the received optical signal; a frequency domain processor for applying a selected frequency domain function to the FFT output array {R A X } to derive a modified array {V A X }, the frequency domain processor comprising: a multiplier for multiplying the FFT output array {R A X } by a respective coefficient vector implementing at least a portion of the frequency domain function; and a transpose-and-add block for emulating parallel real FFT-IFFT filters; and an Inverse Fast Fourier Transform (IFFT) filter for deriving a time domain output vector based on the modified array {V A X }; wherein the frequency domain function is selected to support any two or more of: clock recovery, dispersion compensation, quadrature error correction and signal framing; and wherein the transpose-and-add block comprises: a vector addition block; a direct path for supplying the FFT output array {R A X } to the vector addition block; and a transpose path for supplying a transpose array { R A X } to the vector addition block; wherein the multiplier comprises a respective vector multiplier disposed in each path, for applying a respective coefficient vector to each array.