Phase noise compensation for long-haul coherent optical communication systems using OFDM

Abstract

Long-haul optical transmission systems employing coherent optical orthogonal frequency division multiplexing (CO-OFDM) are sensitive to laser phase noise. This causes a common phase rotation and inter-carrier interference. An effective method to compensate for the phase noise is to insert an RF-pilot tone in the middle of the OFDM signal. This RF-pilot is used to reverse the phase distortion at the receiver. This thesis presents a detailed performance analysis of the RF-pilot phase noise compensation scheme in a simulated 64 Gbit/s CO-OFDM system. The effects of various parameters including laser linewidth, Mach-Zehnder modulator drive power, pilot-tosignal ratio, and fiber launch power are investigated. A comparison with the pilot-aided common phase error compensation method is provided to show the differences in the BER performance with respect to the required overhead.