Long-haul signal transmission using various modulator formats and frequency conversion

Abstract

With rapid growth in demand for data, audio and particularly video services, optical fibre for long-haul transmission has provided huge bandwidth and has become reliable for signal transmission. The main tasks emerging for designers of long-haul systems are modulation impairments and linear and nonlinear effects in the fibre. Message signal transmission over the optical fibre is the most reliable and fastest form of communication for long-haul signal transmission. This thesis addresses the key aspects of long-haul signal transmission and analyses the essential issues related to modulation, DC and used power, by comparing signal transmission performance with other transmission approaches. A comparative study affords a useful structure for optimisation of the RoF signal transmission over SSMF. This work focuses on achieving high quality signal at lowest BER, for the longest as possible transmission distance by reducing impairments during modulation and transmission such as power variation, distortion, and dispersion over long-haul signal transmission. The key system performance pointers such as Signal Modulation, DC, and Link Amplification, are investigated through various fibre optic configurations. I have found that to achieve consistent long-haul signal transmission, with a high data rate, is necessary to upgrade the optical configuration scheme in a proportional way to the used power, by monitoring the length of the fibre span, compensation span and amplification. When using SSB modulation, I have identified an effective way to reduce the nonlinear effects on modulation and the chromatic dispersion consequences in the fibre link. Furthermore, I have demonstrated that the message signal transmission over the fibre optic link can be improved by CS-SSB modulation, which will increase the effectiveness of the message signal. For easier digitization and the analog to digital signal conversion at some structures, it is very important to convert high frequency to the required IF signals, which can be easily matched. By utilising the DP-DPM and linearising the modulated input signal by applying a strict control on the system parameters, such as the electrical signal difference between both electrodes, and modulation index, I am presenting a configuration obtaining high conversion efficiency, wide bandwidth, and stable output signal. The real-time presentation is tested through VPI and Optisystem Simulation Software, where some of the work as a proof of concept has been experimentally demonstrated.