We study carrier frequency offset estimation (FOE) and compensation for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. A robust FOE is crucial for OFDM reception as multicarrier systems are particularly susceptible to frequency offset. We present an FOE algorithm that reduces training overhead by exploiting the pilot symbols used for channel estimation instead of dedicated FOE pilot symbols.
Our simulations show that the proposed algorithm is robust against noise and dispersion over a wide range of frequency offsets. Additionally, the impact of random laser phase walk on system performance and estimation error is examined.