Effect of semiconductor laser noise on coherent optical OFDM systems

Orthogonal frequency division multiplexing (OFDM) is a modulation/multiplexing method that has many advantageous when it is employed in optical fiber communications. However, the OFDM signal is very sensitive to semiconductor laser’s phase noise that requires either to use a very stable semiconductor laser with a narrow linewidth, or to equalize the phase noise effect before or after demodulation. This thesis presents an in-depth analysis of the long-haul coherent optical OFDM (CO-OFDM) link with pilot-aided feedforward loop (PA-FFL), which is used for pre-demodulation phase noise compensation. The thesis examines effect of large semiconductor laser noise on the OFDM’s performance yielding a new homodyne OFDM design, and showing the feasibility of this technique comparing with the conventional coherent OFDM system