Patent ID: 8355638

Claim:
An optical receiver, comprising: a tap module configured to sample an optical transverse-mode multiplexed (TMM) signal having N independently modulated components to produce K optical samples per signaling interval, where N and K are positive integers greater than one, wherein K≧N; a local oscillator (LO) source configured to generate an optical LO signal; K coherent detectors, each optically coupled to the tap module and to the LO source and configured to: mix a respective optical sample and the LO signal to generate one or more optical interference signals; and convert said one or more optical interference signals into one or more electrical signals indicative of an in-phase component and a quadrature-phase component of the optical sample; and a digital signal processor (DSP) operatively coupled to the K coherent detectors and configured to process the electrical signals produced by the coherent detectors to recover data carried by each of the N independently modulated components of the TMM signal, wherein: the optical receiver is configured to receive the TMM signal via a multimode fiber that supports a plurality of transverse modes; and a coherent detector comprises: a phase mask configured to phase-filter the LO signal to produce a phase-filtered beam, wherein the phase mask causes the phase-filtered beam to have a phase/field-strength (PFS) pattern corresponding to a PFS pattern of a selected transverse mode; an optical hybrid configured to mix (i) an optical beam corresponding to the respective optical sample and (ii) the phase filtered beam to generate the one or more optical interference signals; and a plurality of photo-detectors that convert the one or more optical interference signals into the one or more electrical signals.