FLATTENED FREQUENCY RESPONSE USING FIBER BRAGG GRATING V-SHAPE FILTER IN RADIO OVER FIBER LINKS

A novel scheme for improving RF performance in radio-over-fiber (RoF) systems by using fiber Bragg grating (FBG) is demonstrated. The optical double-sideband (DSB) signal is sent through a fiber Bragg grating working as an optical V-shape filter. The FBG offers simultaneous suppression of the two sidebands and the optical carrier. The closer the sidebands are to the optical carrier, the more the sidebands are suppressed. In this way the detected radio frequency (RF) signal after a photodetector increases as the RF frequency goes higher. Both theoretical analysis and experimental results show that this effect can compensate for the RF gain loss in high frequency region due to the deteriorated performance of devices such as photodetectors and Mach-Zehnder modulators at higher frequency. A uniform system frequency response with fluctuation of no more than 2 dB is obtained from 1 GHz to 16 GHz.