Towards a Portable Multi-Megabit Optical Fibre Sonar Sensor System for Deep Oceanic Passive Seismic Monitoring

Ching Y. Man1, Brian Moss1, Elfed Lewis2, Lai Bun Lok*3

1Analog Devices, Limerick, Ireland (, 2Optical Fibre Sensors Research Centre, University of Limerick, Ireland, 3Department of Engineering, Lancaster University, UK.

An optical fiber communication architecture based on a towed oceanic acoustic sonar sensor array system for very high (>20 Mbps) data rate is described. The proposed transmitter interface is unique compared to traditional sheath and cabling methods typically employed in this application. The result is a portable, lightweight and relatively low-cost solution that would be suitable for deep and remote oceanic deployment and can be fine tuned to detect seismic activities. The technique offers enhanced performance compared to traditional coaxial cable systems for passive sonar acoustic telemetry and communications. We present the design and implementation of the system including data acquisition and high speed fibre transmission interface circuitry using multiple hydrophones. The transmitted signal is digitized, channel-tagged and controlled by a custom-designed application specific integrated circuit (ASIC). The proposed system architecture is programmable and can be optimized for optical carrier specification OC1 to OC3 and beyond. Finally, we discuss work in progress to tailor this instrumentation platform for passive seismic monitoring of deep oceanic environments.