Carrier recovery and reuse in full-duplex radio over fiber 60GHz millimeter-wave system based on frequency quadrupling

This paper presents a novel scheme for implementation of Orthogonal Frequency Division Multiplexing (OFDM) based Radio over Fiber (RoF) systems. In the proposed method, both optical and RF carrier signals are extracted from the received signals at base station (BS) and customer unit (CU) respectively. In the downlink, a dual tone optical millimeter wave signal carrier is generated by a local oscillator using a Mach-Zehnder modulator. The 4-QAM intermediate frequency (IF) signal is OFDM modulated and then modulated on one of the two tones with single side band (SSB) modulation at the central station. A high speed photodiode is used at the base station to detect the SSB optical millimeter wave signal. The reserved uplink optical carrier is separated by optimized filtering. The reuse of the extracted carrier signals help to reduce the complexity of both the stations. The need of high frequency oscillators and the laser diodes at BS and CU are eliminated by this method.