Ceramic and fibre optic hydrophone as sensors for lightweight arrays — A comparative study

Design and development of lightweight arrays has been a subject of intense study in recent years. This is largely owing to the successful deployment of autonomous vehicles as operational platforms for many underwater applications. The acoustic sensing capabilities of these platforms can be greatly improved by adding a hydrophone array and towing it behind them. Apart from the conventional ceramic based acoustic sensing technology, distributed feedback fibre laser hydrophones has opened up another possibility for the design of thin line towed arrays. However, either not enough information is available or they are scattered in the literature to compare the performance envelope of these two technologies from a thin line towed array application perspective. The purpose of this paper is to do a literature survey and compare the status of lightweight and thin line towed hydrophone arrays based on the two technologies for use from small autonomous platforms. The different performance parameters of the array such as its sensitivity, channel count, frequency and bandwidth of operation, power budget, vibration isolation requirements and flow induced noise effect have been addressed. The comparisons are based on both the studies conducted at our laboratory and also results reported on similar systems developed elsewhere. It is believed that this study would help researchers and users in the field of underwater acoustics to understand the areas of performance improvement required under both technologies and make an informed decision on the selection of a technology for a particular application. It is concluded, based on the study conducted and results presented here, that ceramic based acoustic sensor arrays are still a better choice for operation as a thin line towed array compared to the distributed feedback fibre laser hydrophones.