Fabry-Perot Interference Fiber Acoustic Wave Sensor Based on Laser Welding All-Silica Glass

Low-Coherence Homodyne Interferometer for Sub-Megahertz Fiber Optic Sensor Readout

This study proposes a method for interferometric fiber optic sensor readouts. The method utilizes the advantages of the active homodyne demodulation technique and low-coherence interferometry. The usage of the tandem low-coherence interferometer enables modulating the reference interferometer without any changes to the sensor. This achieves high sensitivity, high stability, and a wide frequency band. A sensitivity of up to 0.1 nm (RMS) in the frequency range of 5 kHz is demonstrated by detecting acoustic signals with a fiber Michelson interferometer as a sensor.

Fiber Optic Impact Location System Based on a Tracking Tandem Low-Coherence Interferometer

This study proposes a method for detecting small-length fluctuations for fiber-optic sensors (FOS). The method is based on a tracking tandem low-coherence interferometer and enables the ability to compensate for temperature and deformation drifts in FOS. As a result, the constant high sensitivity of FOS over a wide frequency range is guaranteed. Sensitivity to the level of 2 nm in the frequency range of 200 kHz has been demonstrated. The operation of the circuit is demonstrated on the example of the 2D location of acoustic signals using a correlation algorithm for signal processing, known as the time reversal method. It is shown that this system enables us to determine the place of the impact on the sample under the test with an accuracy of about 2 cm using a single sensor.

Ultra-High Sensitivity Ultrasonic Sensor with an Extrinsic All-Polymer Cavity

An ultra-high sensitivity ultrasonic sensor with an extrinsic all-polymer cavity is presented. The probe is constructed with a polymer ferrule and a polymer-based reflection diaphragm. A specially designed polymer cover is used to seal the cavity sensor head and apply pretension to the sensing diaphragm. It can be manufactured by a commercial 3D printer with good reproducibility. Due to its all-polymer structure and high coherence depth, the sensitivity of our proposed sensor is improved significantly compared with that of the other sensor structures. Its sensitivity is 189 times as great as that of the commercial standard ultrasonic sensor at the ultrasonic frequency of 50 KHz, and it has a good response to ultrasonic within the frequency range of 18.5 KHz-200 KHz.