Research For Key Technology Of New All-fiber Polarization-stable Photonic Millimeter-wave Generation

With the rapid development of mobile communications, the existing wireless spectrum resources have been unable to meet the growing demand for broadband wireless services. To overcome the lack of radio spectrum resources, Radio Over Fiber(ROF) has been proposed. ROF is a technology which is the combination of light and microwave. In the technology, millimeter-wave subcarrier propagates in the optical fiber, so the millimeter-wave has a longer propagation distance than in the atmosphere, and it can meet the demand of high-capacity transmission and high-speed access demand. ROF is one of the most promising technologies in ultra-broadband wireless access because of its high-capacity, low cost, low power consumption and long propagation distance. With the role of local oscillator and emission sources, millimeter-wave generator is the key factor of in ROF system, therefor, millimeter-wave technology is a hot area in the research on ROF. In the paper, a new all-fiber polarization-stable wavelength-tunable millimeter-wave generator is proposed and studied. The primary achievements in this paper are as follows:1. The principles of ROF is analyzed, the advantages of ROF compared to traditional wireless communication systems and the applications are summarized. The key technologies’research, and the research status of the mainstream millimeter-wave generation are introduced too.2. The theoretical principle of the all-fiber polarization-stable wavelength-tunable photonic millimeter-wave generator is studied. The key components of the generator such as polarization maintaining fiber(PMF), polarization maintaining fiber Bragg gratings(PMFBG), fiber laser and polarization scrambler(PS) are analyzed.3. A new all-fiber polarization-stable wavelength-tunable photonic millimeter-wave generator is proposed, It utilizes frequency selecting of PMFBG to produce two polarization-stable lasing signals, ensures the consistency of the orthogonal polarization’s power by polarization scrambler, and then generates microwave/millimeter-wave by beating frequency in high-speed photodetector(PD). Millimeter-wave of10-100GHz can be generated by different lateral strain loading on the PMFBG. In the simulation, the millimeter-wave of60GHz is generated and transmission performance of the millimeter-wave in radio-over-fiber(ROF)downlink is analyzed. The results show that the eye diagrams demodulated in the mobile station are excellent when the optical carrier which is modulated the millimeter-wave sub-carrier transmits over80kilometers from center station to base station. The excellent performance of the system in long-distance transmission is verified.4. In the experiment, a scheme for tunable millimeter-wave generation based on a polarization-stable dual-wavelength PMFBG laser is produced, and the microwave signals of20.407GHz and22.050GHz are generated by different axial pulls loading on PMFBG.5. Optimizing the parameters of new all-fiber polarization-stable wavelength-tunable photonic millimeter-wave generator, the effects of laser’s power, linewidth, width of pulse profile, PMF length, PMF group velocity delay, PMF group velocity dispersion, PMFBG and PD are analyzed.