Liu Guigen, Zhu Yupeng, Sheng Qiwen, Han Ming
Opt Lett. 2020 Aug 1;45(15):4164-4167. doi: 10.1364/OL.397955.
We report an ultrasonic sensor system based on a low-finesse Fabry-Perot interferometer (FPI) formed by two weak chirped fiber Bragg gratings (CFBGs) on a coiled single-mode fiber. The sensor system has several desirable features for practical applications in detecting ultrasound on a solid surface. By controlling the birefringence of the fiber coil during the sensor fabrication, the sensor is made insensitive to the polarization variations of the laser source. The circular symmetric structure of the fiber coil also renders the omnidirectional response of the sensor to ultrasound. While the fiber coil is bonded directly to the structure, the CFBGs are suspended from the structure and free from large background strains with little reduction to the sensitivity of the sensor. The low-finesse FPI features a sinusoidal reflection spectrum. Like the conventional phase-generated carried technique, a phase modulator is utilized to implement quadrature demodulation. Therefore, the sensing system is adaptive to large background perturbations experienced by the fiber coil.
我们报道了一种基于低精细度法布里-珀罗干涉仪（FPI）的超声传感器系统，该干涉仪由缠绕在单模光纤上的两个弱啁啾光纤布拉格光栅（CFBG）构成。该传感器系统在固体表面检测超声的实际应用中具有几个理想特性。通过在传感器制造过程中控制光纤线圈的双折射，可使传感器对激光源的偏振变化不敏感。光纤线圈的圆对称结构还使传感器对超声具有全向响应。当光纤线圈直接粘结到结构上时，CFBG 则从结构上悬空，免受大的背景应变影响，而传感器灵敏度几乎不受降低。低精细度 FPI 具有正弦反射光谱。与传统的相位生成载波技术一样，利用相位调制器实现正交解调。因此，该传感系统能适应光纤线圈所经历的大背景扰动。
