Although many advantages of OFDM technology have been gradually found,and has been widely used in the wireless communication system,but the application in optical communication is in recent years.There are many differences between traditional OFDM system and the OFDM in optical communication system.The traditional OFDM system is the transmission of electrical signals,and the polarity of the signal is not required,While in the wireless optical communication system,because of the linear relationship between the current and the light intensity,the OFDM signal must be expressed as light intensity.Which means the modulation signal must be a real-value signal and positive signal.