Bidirectional Radio over Fiber Transmission System Using Reflective Semiconductor Optical Amplifier

Abstract

Radio over fiber is becoming an increasingly important technology for the wireless market since it introduces a good data transmission rate and large bandwidth. We have demonstrated a bidirectional radio over fiber ROF system based on a reflective semiconductor optical amplifier (RSOA) utilizing an offset quadrature differential phase shift keying (OQPSK) signal for down-link and an on-off keying (OOK) signal re-modulated for up-link. We have performed a detailed comparison between OQPSK and DPSK according to the system behavior. We have also implemented a combination of SCM-ROF and optical wavelength division multiplexing (WDM) techniques to simplify the access network architecture. The combination of two different types has been performed to provide high bit data rate and wide bandwidth in cellular communication. The system allows different Base Stations (BS's) to be fed by a common fiber. Different wavelength channels can be allocated to different BSs depending on user requirements. We have also presented an investigation on the performance of Orthogonal Frequency Division Multiplexing (OFDM) system in terms of degradation of channel capacity, variation of optical input power and variation of number of subcarriers. OFDM is an attractive technique for achieving high bit rate data transmission. Several measurements are found; the eye diagram, Bit Error Rate (BER) curves for both uplink and downlink, RSOA gain curve and noise figure with the variation of input power and temperature for each system.