Radio-over-fiber downlink system based on a new polarization-stable millimeter-wave genarator

Abstract

A radio-over-fiber(ROF) downlink system based on a new polarization-stable millimeter-wave generator is proposed to reduce costs, increase transmission distance and improve system performance. Compared with traditional system, the system uses two polarization-stable laser signals produced by selecting the frequency of the polarization maintaining fiber Bragg grating(PMFBG) to generate millimeter-wave by beating frequency. It is easy to be implemented and the influence of power noise on the system is reduced. The effects of laser power, linewidth and reflectance spectrum of PMFBG on the performance of millimeter-wave are analyzed; Simulation shows that the frequency of millimeter-wave is affected by the group delay, the length, the dispersion of the polarization-maintaining fiber(PMF) and the width, the chirp coefficient of laser's pulse profile. After optimizing parameters of PMF, millimeter-wave of 60GHz is generated, and the ROF downlink system is analyzed. The results of the study show that the eye diagrams demodulated in the mobile station are excellent when the optical carrier which is modulated by the millimeter-wave serving as sub-carrier transmits over 80 kilometers from center station to base station. The excellent performance of the system is verified.