Research Of The Wideband RF Signal Transmission Over Fiber

Recently the technology of the RF signal transmission over fiber has been a research hot spot in radar communication and optical fiber communication. With the help of the modern advanced optic-fiber communication technology, transmission system of the wideband RF signal over fiber is theoretically analyzed and experimentally verified in this thesis. A 6-18GHz RF signals over fiber link is then carefully designed and successfully realized.The technology of the RF signal transmission over fiber is investigated in three parts. Firstly, a link model is analyzed. Considering that the digital control signals may be used in actual applications, a wavelength division multiplexing (WDM) technology is used in the designed transmission system so that two different transmission signals including the wideband RF signals and the digital control signal, can be transmitted in one single fiber simultaneously. In central station, a DFB laser emits the light of a 1550nm and is externally modulated by the wideband RF signal using Mach-Zehnder Modulator (MZM). Meanwhile, a FP laser emits the light of1310 nm and is directly modulated by the digital control signal. The two different signals are then transmitted in the same fiber using a wavelength division multiplexer (WDM). In based station, the two optical signals from central station can be separated using another WDM and then demodulated by the corresponding photodetectors.Secondly, the basic structure of the RF signal transmission over fiber system is proposed, The main devices in the link including laser,MZM,photodetector,coupler and WDM are then introduced and their effects on the system performance are systematically analyzed.Finally, based on the link model and the knowledge of the optical devices in the link, the wideband RF signals over fiber system is realistically set up and the performances are measured at different temperatures. The main tasks contain the design and realization of the DFB laser driving circuit, MZM bias voltage control circuit as well as the digital signal modulation and demodulation circuits, the combination of these circuits with the optical links, and the performance measurements for this wide RF signal over fiber system. The use of MZM bias voltage control circuit avoids the system performance fluctuation due to the change of environmental temperature. The experimental results show that system can work normally in any condition of the environmental temperature.