Millimeter wave ROF system has the characteristics of large capacity, light equipment and strong anti-interference ability. It is suitable for train ground communication of high-speed railway and establishes wireless communication modes such as Pico cellular, which has great market potential. In order to reduce the cost and improve the system stability, the structure of millimeter wave ROF system is simplified, and the optical carrier direct QPSK modulation ROF system for the purpose of high-speed data transmission is adopted; Seek a series of problems such as how to obtain pure local oscillator in the uplink transmission of optical direct modulation ROF system, and the impact of optical fiber dispersion on high-speed millimeter wave ROF system, so as to improve the existing millimeter wave ROF system and meet the needs of the future development of wireless communication system.

Because of its broadband characteristics, terahertz band has great application potential in the fields of communication, radar, characteristic spectrum detection and so on. In order to make the data rate of short-range wireless communication reach 10Gbps, a terahertz wireless communication system is established by using photoelectric combination technology with THz band (125ghz) as the carrier. As shown in the figure below, the 62.5ghz signal is used to modulate the optical wave, and the optical signal separated by 0.125thz is generated through the plane wave division circuit. The optical signal is modulated by the transmitted data, and then enters the PD for photoelectric conversion to generate the 0.125th group of modulated waves. After amplification, it is fed into the antenna for transmission, and the receiving end enters the low-noise amplifier after passing through the antenna. After detection, it becomes a baseband signal. After amplification, the data is recovered.