Dual Interferometric Interrogation for DFB Laser-Based Acoustic Sensing

Area of Science:

• Engineering
• Acoustic Sensing
• Optical Physics

Background:

• Conventional piezoelectric hydrophones have limitations like size, electromagnetic interference, and corrosion.
• Fiber-optic hydrophones (FOHs) offer advantages such as mechanical flexibility and resistance to harsh environments.
• Distributed feedback (DFB) lasers are sensitive to perturbations, enabling acoustic signal detection via wavelength shifts.

Purpose of the Study:

• To present an enhanced interrogation mechanism for fiber-optic hydrophones.
• To improve the cost-effectiveness and resolution of phase-based measurements.
• To extend the dynamic range of FOH systems for underwater applications.

Main Methods:

• Utilized Mach-Zehnder interferometers to translate laser wavelength shifts into measurable phase deviations.
• Implemented a dual interferometric setup integrated with a standard demodulation algorithm.
• Leveraged the sensitivity of distributed feedback (DFB) lasers to external perturbations.

Main Results:

• Achieved cost-effective and high-resolution phase-based measurements.
• Demonstrated a significant increase in dynamic range from 125 dB to 139 dB at 1 kHz.
• Maintained the noise floor without degradation while extending the dynamic range.

Conclusions:

• The enhanced interrogation mechanism substantially improves FOH performance.
• The expanded dynamic range enhances the utility of FOH systems in underwater environments.
• This technology supports critical applications including underwater surveillance, submarine communication, and marine ecosystem monitoring.