Patent ID: 7693428

Claim:
An optical receiver to receive a data modulated beam from an optical link, comprising: at least a first optical hybrid for receiving the data modulated beam and a local oscillator beam; the data modulated beam being one channel of WDM orthogonal frequency division multiplexed (OFDM) communication system, the OFD multiplexing having N subcarrier in each WDM channel, each subcarrier being individually M-PSK encoded, a set of photodetectors receiving output beams from the optical hybrid and producing electrical signals I and Q; a digital signal processing unit receiving the electrical signals I and Q, converting them into digital signals, measuring their instant power P 1 (t i )=Q(t i ) 2 +I(t i ) 2 , where a sampling interval Δt i =t i+1 −t i is equal or less than a symbol interval, calculating an expected nonlinear phase shift φ 1 (t i ) i for the i-th sampling interval, performing a nonlinearity compensation by multiplying the signals I(t i ) and Q(t i ) on a nonlinearity coefficient depending on the expected nonlinear phase shift, transforming the digital signals into frequency domain, forming a set of spectral signals each having its own digital frequency, demodulating the data encoded in each spectral signal, and outputting a received information.