Experimental Performance evaluation of RF over Fiber Optic Channel for QPSK Modulation

This paper characterizes the effect of RF over Fiber Optic (RFoF) Channel for long distance transmission of QPSK modulated RF signal at L Band. QPSK modulated signal ranging from 10 Mbps to 300 Mbps is transmitted over Fibre Optic cable. The performance of the channel is evaluated in terms of constellation diagram and Error Vector Magnitude (EVM) for various data rates. Commercial off the shelf (COTS) Signal Generator and Spectrum Analyser are configured along with RF to Optical converter and Optical to RF converter for performance evaluation of RFoF channel. Further, investigative performance analysis of the channel was carried out for Low Noise amplifier (LNA) ON and OFF conditions. Moreover, the comparative performance analysis was carried between Fiber Optic cable and equivalent length of RF cable. The aim of the proposed architecture is to carryout performance evaluation of QPSK modulation over LOS datalink in the Test Rig. This will facilitate the process of improvement of the signal quality and hence the link margin of the data link systems.