Patent ID: 8849130
Filing Date: 2014-09-30
Classification: H04B

Abstract:
1. An apparatus comprising: an M×N coupler for receiving an optical signal into a first of M input ports of the M×N coupler and for receiving a local oscillator signal into a second of the M input ports, where M and N are integers larger than 2; N detectors, each detector for detecting a mixed signal from a respective output of the M ×N coupler to generate one of N respective detected signals; N Alternating Current (AC) couplers, each AC coupler for filtering a respective one of the detected signals to correspondingly generate one of N filtered signals; an adder for adding the N filtered signals to determine a directly detected signal term; a first subtractor for subtracting the directly detected signal term from a first set of at least one of the N filtered signals to determine an in-phase signal; a second subtractor for subtracting the directly detected signal term from second set of at least one of the N filtered signals to determine a quadrature signal; and a digital signal processor for processing the in-phase signal and the quadrature signal in the digital domain to recover the optical signal.