In order to improve frequency multiplication factor and tuned ability of optical carrier-to-sideband ratio (OCSR) in optical single sideband (OSSB) radi o over fiber (RoF) system,a novel scheme is proposed by using Mach-Zehnder modu l ator (MZM) and fiber Bragg grating (FBG) based on the polarization multiplexing technology,and wide dynamic range of OCSR can be realized by adjusting the polar ization angle of polarization controller (PC).Basic principle of the proposed s cheme is analyzed theoretically,and influence of the relevant parameters on OCS R tuning characteristics is discussed,which is consistent with the experimental results.When the OCSR is tuned from 4.35dB to 0dB,the experimental results sh ow that receiver sensitivity can be increased by 1.31dB at BER=10－9 for transmission over 50km standard single mode fiber (SSMF ).