Investigation of stimulated Brillouin scattering effects in radio over fiber distribution systems
Hu, Ling (2006) Investigation of stimulated Brillouin scattering effects in radio over fiber distribution systems. Master of Engineering thesis, Dublin City University.
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Because of the emerging demand for bandwidth, future wireless access networks are likely to use high frequency microwave signals as the access media. Hence, radiofrequency (RF) signals need to be processed and transmitted with higher bandwidth in many applications. However, the attenuation of RF signals in traditional transmission media increases rapidly when the frequencies of the signal increase. On the other hand, optical fiber has emerged as an alternative and promising transmission medium in which RF modulated optical carriers can be transmitted and distributed with very low loss. This kind of hybrid radio/fiber system or Radio over Fiber (RoF) system provides good synergy between optics and radio.
This thesis first introduces optical and radio communication systems, and provides a review of the RoF systems for wireless access networks. The research then explores the effects of Stimulated Brillouin Scattering (SBS) in RoF distribution networks, and shows that it can seriously degrade the performance of radio-over-fiber systems in which a high transmission power is required. The work then goes onto look at how pre-filtering of the optical microwave signal can simultaneously perform Single Sideband (SSB) filtering to overcome the effects of signal fading due to dispersion, in addition to reducing the effect of SBS on signal transmission. Subsequently, the thesis investigates how to overcome the SBS effect by changing the modulation depth of the optical microwave signal. These experiments show that increasing the modulation index may increase the Brillouin threshold, as it is primarily the carrier power that induces the SBS effect due to its narrow linewidth. In this way we can further reduce the limitations on system performance due to SBS.
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