Sagnac-type fiber-optic array sensor for detection of bulk ultrasonic waves

Area of Science:

• Photonics and Wave Sensing
• Acoustic Metrology

Background:

• Conventional hydrophones often have limitations in detecting ultrasonic waves, especially when the receiver size is much smaller than the acoustic wavelength.
• There is a need for advanced sensing technologies capable of precise ultrasonic wave detection with enhanced signal quality.

Purpose of the Study:

• To describe a novel fiber optic array sensor for bulk ultrasonic wave detection.
• To demonstrate its capability for tunable narrowband detection and improved signal-to-noise ratio (SNR).

Main Methods:

• Development of an intrinsic fiber optic Sagnac interferometer.
• Formation of a fiber array through multiple folding of optical fiber into flat coils.
• Testing the sensor's performance in detecting ultrasonic waves in water using piezoelectric and laser sources.

Main Results:

• The fiber optic array sensor can operate in both in-phase and tunable narrowband detection modes.
• Narrowband detection frequency can be tuned by adjusting array element spacing to match the ultrasonic wavelength.
• The array sensor demonstrated an enhanced SNR compared to single-element detection schemes.

Conclusions:

• The developed fiber optic array sensor is effective for bulk ultrasonic wave detection.
• Its tunable narrowband capability and enhanced SNR offer advantages over conventional hydrophones.
• Potential applications include process monitoring, smart structures, bio-medical ultrasound, and chemical sensing.