Patent ID: 8767575

Claim:
An apparatus comprising: a fast Fourier transform (FFT) module configured to transform a time domain optical signal into a frequency domain optical signal; a circular shifter coupled to the FFT module and configured to provide coarse frequency offset compensation to the frequency domain optical signal based on an estimated frequency offset; a frequency offset estimation module coupled to the circular shifter and configured to provide the estimated frequency offset based on a power spectrum of the frequency domain optical signal or a data block header autocorrelation of the time domain optical signal; and a circuit indirectly coupled to the circular shifter and comprising: a multiple-input and multiple-output (MIMO) and finite impulse response (FIR) module a phase ramping module coupled to the MIMO and FIR module, a phase rotation module indirectly coupled to the phase ramping module, and a phase detector module coupled to the phase ramping module and the phase rotation module.