Research On The Characteristics Of The Clipping And Filtering Signal In OFDM-RoF Optical Transmission System

OFDM technology has a strong anti-jamming capability and provides a good solution for system extension which is recognized as one of the core technologies of 4G's. Radio over fiber technology which is a good wireless access scenario can provide a large bandwidth, low-loss transmission channel with 4G and is also believed to be one of the network technologies of the 4G network. Therefore, the combination of OFDM and RoF technology should be the future direction of communication development.It's showed by extensive investigation that the study of OFDM-RoF system is currently mainly concentrated on the OFDM signal waveform distortion caused by the light source, fiber, optic modulators and so on. There are few reports that discussed how the OFDM signal have effects on the system performance. Therefore, it's proposed OFDM-RoF optical transmission down-link model in this paper. And those key parameters that could have influence on the whole system performance.Firstly, it's presented the solution to lower PAPR of the OFDM signal adopting the technique of clipping and filtering to reduce the affection of too large PAPR on the nonlinear components and settle down the problem of degradation of the performance of OFDM-RoF optical transmission system caused by the too high peak power. Optimal parameters have been derived in different threshold, different modulation techniques and multiple clipping and filtering operations, the simulation by simulations in several ratio of clipping. Secondly, the nonlinearity of RoF link has been studied. The function of multimode fiber transmission characteristics and the expression of the nonlinearity of RoF link are given. Ultimately, taking all of factors into account, simulation of transmiting clipping and filtering OFDM signal in the nonlinearity of OFDM-RoF link has been simulated and the performance of the bit error rate of the OFDM-RoF system has been investigated. Thus, the feasibility of the clipping and filtering technique in the OFDM-RoF system has been proved.Compared with other methods, the clipping and filtering technique is simplily designed and easily completed. The proposed OFDM-RoF model will have the merits of compatibility and practicability since the clipping and filtering technique won't change the physical layer specification. Then, further investigations can be carried on to improve system's performance.