Design of an RoF Downlink System for generation of dual frequency millimetre wave carrier signal by frequency multiplication

In this paper we propose a Radio-over-Fibre (RoF) downlink system for dual frequency millimetre wave (mm wave) signal generation. We externally modulate two 1550 nm Laser sources using balanced Mach Zehnder Modulators (MZM). A 12 GHz Radio Frequency (RF) signal is used for modulation. The two MZMs separate out the odd and even order sidebands each. The MZM modulated optical signal is intensity modulated by a 5 Gbps baseband signal. Single Mode Fibre (SMF) is used as a transmission medium between Central Station (CS) and Base Station (BS). A PIN photo-detector at the BS is used to detect the electrical signal and generate mm wave electrical signals by means of frequency multiplication. The mm wave signals contain the baseband data and are propagated into the wireless medium. Simulation ensures good performance for this 5Gbps RoF downlink system. A power penalty of less than 0.6dB is achieved for a bit error rate (BER) of 10⁻⁹ after transmitting successfully for a length of 80km over a single mode fibre.