Single pin coherent receiver

A coherent optical receiver for receiving a data signal x(t) modulated on an optical signal transmitted through an optical communications system, the coherent optical receiver comprising:

• a local oscillator (LO) laser generating a linearly polarized LO light having a frequency of f1=f0±Δf, where f0 is a frequency of a narrowband carrier of the optical signal, and Δf is at least equal to a band-width fB of the data signal x(t);
• a single detection path for detecting a respective polarization of received light of the optical signal and for generating a corresponding one multi-bit digital sample stream representative of the detected polarization, the detection path comprising:
• a power combiner for combining the LO light with the respective polarization of received light of the optical signal;
• a single photodetector for detecting a combined light output from the power combiner, and generating a corresponding analog signal;
• a low-pass filter for filtering the analog signal generated by the photodetector to generate a filtered signal, the low-pass filter having a filter characteristic that exhibits a roll-off at a frequency greater than approximately Δf+nfB, where n is an integer multiple and n≧1;
• and
• an analog-to digital (A/D) detector for sampling the filtered signal at a sample rate greater than approximately 2(Δf+nfB) from the low-pass filter to generate a the multi-bit digital sample stream;
• and
• a digital signal processor for digitally processing the multi-bit digital sample stream to recover respective In-Phase and Quadrature components of the detected polarization.