Study Of High Performance-to-price Ratio Radio-over-fiber System

With society developing, people become more urgent to communication demand, and hoped transmits higher grade information in limited band width. Radio-over-fiber technique has fully displayed flexibility in wireless communication and provided large capacity, low cost in optical communication. It has formidable potential in future communication.Mach-Zehnder Modulator and Phase Modulator are often used to generate optical mm-wave, which is the key technique in radio-over-fiber system. The phase modulator has low insertion loss, low voltage actuation, high efficiency, and so on, compared with Mach-Zehnder modulator (MZM), the phase modulator has no complex control circuit and direct-current drifting influence, the system cost can also be decreased. It is possible to eliminate multi-diameter effect and Doppler shift which is in wireless communication after transmitting Orthogonal Frequency Division Multiplexing (OFDM) signal in optical fiber communication system. This article mainly studied the high performance-to-price ratio radio-over-fiber system, which is based on phase modulator to generate optical millimeter -wave. The innovate work are as followed:(1) A radio-over-fiber system with sextuple optical millimeter-wave generation by transmitting OFDM signal was proposed by two parallel phase modulators.2.5 Gbit/s OFDM signal is modulated on the optical millimeter wave with 60GHz frequency and transmitted to the base station over standard single-mode fiber. We have analyzed the generation principle and the transmission performance over fiber of optical millimeter wave generation by theory and simulation, respectively.(2) A system with octal optical millimeter-wave' generation which is based on two parallel phase modulators was proposed. After adjusting the phase modulator's phase -shift parameter, the two step sidebands in frequency spectrum are suppressed. Carries on the superimposition two groups signals after a power coupler, there are only the central carrier and two four step sideband left. We have analyzed the generation principle and simulation the system.