Digital Radio over Fiber System with OFDM & OACI Reduction and Its Performance Evaluation

Radio over Fiber (RoF) system uses remodulation technique to reduce the hardware requirement at every Base Station. This paper reports a study of Radio over Fiber system using remodulation along with Digital Modulation scheme of OFDM, in which the same optical carriers are used for both downlink and uplink connection. The main drawback of remodulation ROF system is Optically Generated Adjacent Channel Interference (O-ACI), which is likely to reduce Q-Factor. To overcome this issue, a Single Drive Mach Zehnder Modulator (SD-MZM) is used to tune up the phase and amplitude of carrier signal which can reduce the interference, thereby improving the efficiency level of the system. Instead of a simple Mach Zehnder Modulator used for the conversion of RF signal to Optical signal, a Single Drive Dual Parallel Mach Zehnder Modulator (SD-MZM) at the control station and an MZM modulator at the base station are used. Using a multiuser RoF model, observations are made at various power levels, in terms of Q factor, Eye Height and etc. A Data Envelopment Analysis (DEA) technique is applied to identify the optimum transmission power to achieve high Q factor, eye height and a threshold value of 0.5.