A Novel Frequency Doubling Radio on Fiber System Without Bit Walk-Off Effect by Inserting a Pilot Frequency Signal

Abstract

A novel insertion pilot-frequency signal method for doubling frequency radio on fiber (ROF) system is proposed. At the center station (CS), the carrier emitting from the continuous wave (CW) laser is split into two branches. In one branch, a composite RF drive signal formed by combining the data modulated by a phased modulator (PM) and the data gained by an electrical gainer (EG) is loaded to the Mach-Zehnder modulator (MZM) to produce ± 1th order sideband signals. The data signal of down link is modulated only on −1th order sideband. The other branch is used as the pilot signal. At the base station (BS), the pilot signal is reflected out using a fiber Bragg grating (FBG) and used as the carrier for the uplink. The signal passing through the FBG is sent into the photodetector, and the twofold millimeter wave signal is generated. The mathematical analysis and simulated experiment are given. The innovation of this paper is to introduce the pilot optical signal method for carrier reuse in ROF, it can overcome the poor tunability and degraded downlink performance in the conventional carrier reuse in ROF. The effect of bit walk-off is eliminated due to the data of downlink and uplink being modulated on the −1th and 0th order sideband respectively.