Optical millimeter waves signal generation using stimulated brillouin scattering approach for radio over fibre system

Abstract

Mm-waves are vital to overcome the issues of spectral congestion at low-frequency ranges and to acknowledge the performance of the Radio-over-Fibre (RoF) systems due to their large bandwidth, low cost and low attenuation. In this thesis, an alternative method is proposed, which used Stimulated Brillouin Scattering (SBS) in the generation of optical mm-waves signals based on the RoF system. The proposed approach is compared with optical intensity modulations, such as Double-Side Band (DSB) and Single-Side Band (SSB), to determine the enhancement in signal generation, Bit Error Rate, power received and eye diagram. Previous studies have confirm that the decrease on the performance of the external modulation scheme system is due to the dispersion and fading effect in optical signal generation with a high Bit Error Rate (BER) at long fibre distances, larger insertion loss and low frequency response. The proposed system consists of Central Station (CS) and Base Station (BS), where SBS is successfully generated by Optisystem software with 40 Ghz mm-waves signal by utilising a Continuous Wave (CW) laser in a single mode fibre (SMF) via Mach Zehnder Modulator (MZM) with Erbium-Doped Fibre Amplifier (EDFA), optical circulator, optical filter and photodiode. Several performance criteria measured for the signal generation of optical mm waves are based on received power, input power, transmission distance, error probability and eye diagram. The simulation results affirm that the DSB+SBS system exhibits the best performance amongst the schemes, in which DSB+SBS is superior compared with SSB, which significantly transmit the signal with fibre distance at 85-km and 28% improved before reaching the threshold of optical communication system of 10−9. The average received power at 50-km for DSB+SBS and SSB+SBS are −16.94 dBm and −15.71 dBm, respectively. Further, the plot of eye diagram and BER curve is evaluated at 50-km distance where DSB+SBS manages to receive the lowest BER of 10−77 compared with the SSB+SBS of 10−60, and DSB modulation shows an error floor because it generates signal at a low distance range. Moreover, the validation of theoretical and simulation result have also been presented. Thus, the DSB+SBS technique is capable of enhancing the generated optical mm-waves signals with low error probability at long distances.