Spring-Loaded Diaphragm-Based Fiber Acoustic Sensor
Spring-Loaded Diaphragm-Based Fiber Acoustic Sensor
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DOI：
10.1109/jlt.2019.2923369
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发表时间：
2019-09-15
影响因子：
4.7
通讯作者：
Digonnet, Michel J. E.
中科院分区：
文献类型：
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作者：
Afshar, Behrad Habib;Digonnet, Michel J. E.
我们报道了一种新的光纤传感器，它利用弹簧加载的圆形膜片来检测极弱的声波。当暴露在声波中时，隔膜相对于静止的基板平行于自身振动。利用单模光纤提供的激光束以干涉方式检测到该振动，该单模光纤放置在距离膜片类似的30微米处。横跨反射膜片和衬底的光束被反射，并重新耦合到光纤中。当膜片振动时，它会调制反射光束的相位和幅度分布，因此，光功率重新耦合到光纤中。这种功率调制的测量提供了声波的幅度和频率。与上一代相比，这种设计有几个优点。它不需要透镜，灵敏度对芯片和光纤之间的角度偏差的依赖性小得多，组装更快、更简单，压力分辨率提高了近2倍。介绍了一种传感器样机，在300~20 kHz范围内测得的平均压力分辨率为7.6 mA/根Hz，在7.5 kHz时的分辨率为1.8 mA/根Hz。测量的声学灵敏度与询问光的偏振无关。由于光纤端的弱菲涅耳反射产生了杂散的法布里-珀罗涉仪，测量的波长依赖性比预期的要大。第二种传感器具有抗反射涂层光纤端，其波长依赖性显著降低，这在多路复用传感器阵列中引起了极大的兴趣。
We report a new fiber sensor utilizing a spring-loaded circular diaphragm to detect extremely weak acoustic waves. When exposed to an acoustic wave, the diaphragm vibrates parallel to itself relative to a stationary substrate. This vibration is detected interferometrically with a laser beam provided by a single-mode fiber placed similar to 30 mu m from the diaphragm. The beam straddles the reflective diaphragm and the substrate, is reflected, and recoupled into the fiber. When the diaphragm vibrates, it modulates the phase and amplitude profiles of the reflected beam, and therefore, the optical power recoupled into the fiber. A measurement of this power modulation provides the amplitude and frequency of the acoustic wave. This design presents several advantages over the previous generation. It does not require a lens, its sensitivity is much less dependent on angular misalignment between the chip and the fiber, assembly is faster and simpler, and the pressure resolution is improved by a factor of similar to 2. A sensor prototype is described with a measured average pressure resolution of 7.6 mu Pa/root Hz between 300 Hz and 20 kHz and a resolution of 1.8 mu Pa/root Hz at 7.5 kHz. The measured acoustic sensitivity is independent of the polarization of the interrogating light. The measured wavelength dependence is larger than expected, as a result of a spurious Fabry-Perot interferometer caused by the weak Fresnel reflection on the fiber end. A second sensor with an anti-reflection-coated fiber end is reported with significantly reduced wavelength dependence, of great interest in multiplexed sensor arrays.