Development and Characterisation of a high performance Distributed Feedback Fibre Laser Hydrophone

Abstract

Fibre laser based sensing is fast developing and provides an attractive alternative to conventional piezo-ceramic sensors used in underwater surveillance applications. This thesis presents a novel pressure compensated fibre laser hydrophone for thin-line array applications. Major design considerations are presented along with a comprehensive design approach. Analytical model of the proposed configuration was derived and validated through finite element analysis (FEA) and experimentation. The distortion performance of major phase generated carrier demodulation schemes are analysed in the context of fibre laser based sensing and effect of spectral overlapping is characterised. The application of thin line arrays for underwater surveillance to some extend is limited by flow noise. Flow noise estimates for the proposed configuration were obtained through analytical modelling and FEA of array sections. This thesis also presents the performance validation of the static pressure compensation scheme and characterises the effect of temperature and acceleration on sensor performance.