Research On PAPR Reduction Without Side Information For IM-DD Optical OFDM System

Orthogonal frequency division multiplexing (OFDM) is a high-speed parallel multi-carrier transmission technology. And OFDM has low complexity, the ability of resistance to frequency selective fading and suppression of narrowband interference and othe advantages. In recent years, optical OFDM technology has been widespread concern in the field of optical communication. At the same time, FFT electronic chip and DSP technology are developing rapidly. Optical OFDM system shows strong chromatic dispersion tolerance and polarization mode dispersion tolerance. It is one of the core technologies of the future of optical communications and mobile communication. But a major drawback of the OFDM system is high peak-to-average ratio. When the PAPR of the signal value exceeds the dynamic range of the power amplifier, it causes the nonlinear distortion of the signal. And it also leads to the bit error rate performance of the OFDM system degradation. So PAPR suppression techniques become the focus in the research of OFDM.This paper first introduces the basic principles and the key technologies of wireless communication OFDM system and optical OFDM system. And the paper focuses on the PAPR concept of OFDM system and its distribution formula. On the basis of careful study to the traditional methods of the PAPR reduction, the paper focuses on the PAPR suppression techniques without side information. The main results of the work are as follows:1. For optical OFDM systems with intensity modulation-direct detection (IM-DD), this paper proposes a simple scheme of PAPR reduction based on phase pre-emphasis. Simulation results show that the scheme can effectively reduce the PAPR. At the same time it does not need to transmission side information and can reduce the complexity of the system.2. Then this paper put forward the method of the application of two broken-line transform to reduce PAPR which also need not sideband information transmission. It can obtain through simulation that the method can reduce the PAPR effectively. And the BER performance is poor. According to different parameters of the selected two broken-line transform, the inhibitory effects of the PAPR are not the same.3. On the basis of the above two methods, this paper presents a hybrid method of PAPR reduction for the IM-DD optical OFDM systems. The hybrid method processes PAPR reduction twice in turn by using phase pre-emphasis and two broken-line transform at the sending end. After the two PAPR reductions processing, PAPR of the signal is to be effective in improving. The receiving end processes the two methods of inverse transform in turn and restore the original signal. Through the simulation the results show that the new algorithm in the case without transmission of side information can effectively reduce the PAPR, and it can achieve an excellent tradeoff between PAPR reduction and BER performance.