Research On PAPR Reduction Based On O-OFDM Systems

The optical orthogonal frequency division multiplexing technology has receivedwide attention and research in large capacity and long distance opticalcommunications due to its high spectrum efficiency, strong anti-interference abilityand good anti-dispersion character. There is a major drawback of highpeak-to-average-power-ratio exciting in optical orthogonal frequency divisionmultiplexing system as well as orthogonal frequency division multiplexing system.The paper mainly focuses on how to solve the problem of high PAPR in the system ofdirect detection optical OFDM transmission, and obtain the main results are asfollows:(1) Analyzes the effect of high PAPR on O-OFDM system theoretically. Whensignal is in the transmission process, the effect of high PAPR on O-OFDM system ismainly reflected in two aspects: signal nonlinear distortion and the fiber’s nonlineareffects. In this paper, simple mathematical reasoning and theoretical explanations ar edescribed. High PAPR effect’s theoretical analysis of the key components in thesystem which include amplifier, analog-to-digital converter and M-Z modulator isdone because of their stringent requirements of linear range. when the transmissionsignal’s PAPR is too high, the key system device will be into the nonlinear region ofHPA, and cause nonlinear distortion. Meanwhile, spread spectrum, modulationdistortion and harmonic are made. Then, we analyze that the high PAPR opticalOFDM signal is easily affected by nonlinear in optical fiber transmission processwhich will not only cause serious fiber Cole effect and reduce the signa l-to-noise ratioof the system, but also engender inter-subcarrier interference and out-of-band powerradiation.(2) The paper proposes a scheme for reducing PAPR in intensity modulationand direct-detection optical OFDM system based on virtual subcarrier. Thistechnology uses specified location part of the virtual subcarrier of OFDM signal toreduce the PAPR. Without the need to send sideband information in the transmitter,this method does not need additional treatment in the receiver. The results ofsimulation and experiment show that the method can not only reduces the PAPR andthe complexity of the calculation, but also improves the bit error rate of the system after200-km standard single-mode fiber transmission.