A novel two-stage phase noise estimation algorithm for coherent optical OFDM systems

Abstract

In coherent optical orthogonal frequency-division-multiplexing (CO-OFDM) receivers, the phase noise caused by the instabilities of the local oscillator is a potentially serious problem. In order to deal with the common phase error (CPE) caused by the phase noise in actual CO-OFDM receiver, a novel two-stage Least Mean Square (LMS) phase noise adaptive estimation algorithm is proposed. In the proposed estimation algorithm, an initial coarse estimation of the optical carrier phase to exploit the knowledge of pilot symbols is followed by a fine LMS adaptive estimation. The main advantage of the proposed method is that the phase-ambiguity problem is avoided after a cycle slip and the Bit Error Rate (BER) performance is improved. Furthermore, the phase noise effect induced by the transmitter laser and receiver Local Oscillator (LO) is analyzed. A simple CO-OFDM transmission system with QPSK to apply the proposed adaptive estimation algorithm is simulated, the simulation analysis shows that the proposed adaptive estimation algorithm has a more excellent performance.