Phase Noise Resistant Rotation Iteration-Based Carrier Interferometry Code Design for High Speed Optical OFDM Systems

The spreading codes have been applied to the orthogonal frequency-division multiplexing (OFDM) system to suppress the peak-to-average power ratio. However, in the spreading code aided high data rate optical OFDM (OOFDM) systems, the subcarrier number is large, which induces the problem of phase noise sensitivity due to the narrow intervals between the adjacent subcarriers. In this letter, we present phase noise resistant rotation iteration-based carrier interferometry (RICI) spreading codes to resist the phase noise interference. With the aid of rotation iteration, the long RICI codes are constructed from the short carrier interferometry codes and the intervals are enlarged. Notably, we prove that the RICI codes are orthogonal with enlarged interval, thus they can combat the phase noises and provide more reliable performances for the OOFDM systems. Theoretical and simulation results are provided to demonstrate the benefits achieved by the proposed RICI codes, which can provide more stable communication in the presence of phase noises.