Research On RoF Technology And Its Applications

Radio-over-Fiber (RoF) is an enabling technology, where microwave or millimeter wave signals are modulated onto the optical signals, and transported through optical fiber. Due to its flexibility, bandwidth efficiency and low cost, RoF technology is deemed as one of the choices for the optical wireless access networks in the near future, especially in the places of buidings and companies. By combining the advantage of the flexibility of wireless access technology and the huge bandwidth of optical networks, RoF is regarded one of the most promising solutions for the'last mile'problem. Major achievements of this thesis in the field of RoF include:Microwave and millimeter-wave generation using phase modulation to intensity modulation conversion. We have proposed a method of generating microwave and millimeter-wave by using fiber Bragg grating (FBG) along with optical phase modulator. By reflecting phase modulated optical signal using FBGs, we have realized the conversion from phase modulation to intensity modulation in RoF links, and generated the microwave and millimeter wave signal needed in the base station.Flattening frequency response of RoF links by using V-shaped filter. In order to solve the problem of gain drop in high frequency region of system response, we have proposed a way of improving RoF system performance in higher frequency by using fiber Bragg gratings.The result shows that the optical carrier is suppressed, and the modulation depth of the system is increased.Frequency response equalization and dispersion compensation using fiber Bragg grating in RoF systems. In order to overcome gain drop in high frequency as well as fiber dispersion effect, we came-up with a method to improve RoF systems performance by using fiber Bragg grating as a tilted filter. In the experiment, we used vestigial modulation to solve the gain drop problem and the problem of fiber dispersion effect.Instantaneous microwave frequency measurement using an optical phase modulator. We have, for the first time, proposed to use optical phase modulator to measure the frequency of an unknown microwave signal.There is no need of using bias circuit to operate an optical phase modulator. Therefore, it is more stable than intensity modulation with Mach-Zehnder modulators.Microwave frequency measurement based on PM-IM conversion using fiber Bragg gratings. We have developed a way of measuring frequency using optical phase modulator along with a fiber Bragg grating.A fiber Bragg grating is used as a tilted filter to fulfill the phase to intensity modulation conversion. Since the slopes of the grating at different wavelengths are different, we have avoided using multiple linear filters.