The performance of a Radio over Fiber (RoF) Communications Link is analysed taking into account the effect of impairments such as thermal and shot noise in the receiver photodetector, non-idealities in the Mach-Zehnder modulator (MZM) at the transmitter side, such as finite Extinction Ratio (ER) and large modulation index, chromatic dispersion in the fibre and the impact of Optical Carrier to Signal Ratio (OCSR). A numerical tool for MonteCarlo simulation of the end-to-end Bit Error Rate (BER) has been developed using MATLAB to confirm the predictions obtained from the theoretical analysis using 4-QAM modulation 2021/2022