A receiver that may include a receiver front end arranged to receive (a) a received signal, (b) a reference signal generated by a local oscillator laser, and to output a first intermediate signal; a carrier phase estimator that is arranged to receive the first intermediate signal and to generate a phase estimation signal that represents a phase difference between the received signal and the reference signal; wherein the carrier phase estimator comprises a multi-symbol-differential-detection module and a carrier phase demodulator; and an output circuit arranged to receive the phase estimation signal and to apply a slicing operation to provide an output signal of the carrier phase estimator.