Pressure compensated fiber laser hydrophone: modeling and experimentation

Area of Science:

• Acoustics and Signal Processing
• Optical Sensing Technologies
• Ocean Engineering

Background:

• Traditional hydrophones face limitations in sensitivity, bandwidth, and noise floor performance.
• Developing advanced underwater acoustic sensors is crucial for naval and oceanographic applications.
• Fiber laser hydrophones offer potential advantages over conventional piezoelectric devices.

Purpose of the Study:

• To propose and validate a novel pressure-compensated metal diaphragm based fiber laser hydrophone.
• To achieve high sensitivity, broad bandwidth, and a sea state zero noise floor.
• To optimize sensor design parameters through theoretical modeling and finite element analysis.

Main Methods:

• Development of a simplified theoretical model using acoustic transfer matrices and single degree of freedom elements.
• Axisymmetric finite element analysis for validating the theoretical model.
• Fabrication of prototype sensors and experimental testing, including hydrostatic and acoustic measurements.

Main Results:

• The prototype fiber laser hydrophone demonstrated a flat frequency response up to 5 kHz.
• Experimental results closely matched theoretical predictions.
• Effective pressure compensation was validated up to hydrostatic pressures equivalent to 50 meters depth.
• The sensor achieved an acceleration rejection figure of approximately 0 dB ref 1 m/s(2) Pa.

Conclusions:

• The proposed fiber laser hydrophone configuration successfully meets the objectives of high sensitivity, large bandwidth, and low noise.
• The theoretical model and finite element analysis provide a reliable basis for sensor design optimization.
• The experimental validation confirms the practical feasibility and performance of the pressure-compensated fiber laser hydrophone for underwater acoustic measurements.