Patent ID: 8805206

Claim:
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 f 1 =f 0 ±Δf, where f 0 is a frequency of a narrowband carrier of the optical signal, and Δf is at least equal to a band-width f B 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+nf B , 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+nf B ) 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.