Reduction of Intercarrier Interference Based on Window Shaping in OFDM RoF Systems

In this letter, we theoretically investigate the intercarrier interference (ICI) that is induced by carrier frequency offset (CFO) and sampling frequency offset (SFO) for orthogonal frequency division multiplexing (OFDM) radio-over-fiber (RoF) system. A window shaping technique in the time domain at the OFDM receiver is presented, which can improve the tolerance to the frequency offset and reduce ICI. Compared with the conventional demodulation scheme, the simulation shows that the utilization of the window shaping method can increase the resistance to residual CFO to about eight times at power penalty of 2 dB. It can also improve the tolerance to SFO. A 4.65 Gb/s 4QAM OFDM RoF system over 40 km fiber link and 60 GHz wireless link is demonstrated experimentally. The bit error rate (BER) performance of the scheme is measured, with and without the proposed window shaping method, respectively. About 0.9 dB improvement of the required receiver power at a BER of 10^-3 shows the feasibility of the window shaping method for ICI reduction in OFDM RoF system.