Rong Qiangzhou, Guo Tuan, Bao Weijia, Shao Zhihua, Peng Gang-Ding, Qiao Xueguang
Department of Physics, Northwest University, Xi'an, 710069, China.
Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Institute of Photonics Technology, Jinan University, Guangzhou, 510632, China.
Sci Rep. 2017 Sep 19;7(1):11856. doi: 10.1038/s41598-017-12322-6.
A highly sensitive fiber-optic accelerometer based on detecting the power output of resonances from the core dip is demonstrated. The sensing probe comprises a compact structure, hereby a short section of specific core (with a significant core dip) fiber stub containing a straight fiber Bragg grating is spliced to another single-mode fiber via a core self-alignment process. The femtosecond laser side-illumination technique was utilized to ensure that the grating inscription region is precisely positioned and compact in size. Two well-defined core resonances were achieved in reflection: one originates from the core dip and the other originates from fiber core. The key point is that only one of these two reflective resonances exhibits a high sensitivity to fiber bend (and vibration), whereas the other is immune to it. For low frequency (<10 Hz) and weak vibration excitation (<0.3 m/s) measurement, the proposed sensor shows a much higher resolution (1.7 × 10 m/s) by simply monitoring the total power output of the high-order core mode reflection. Moreover, the sensor simultaneously provides an inherent power reference to eliminate unwanted power fluctuations from the light source and transmission lines, thus providing a means of evaluating weak seismic wave at low frequency.
展示了一种基于检测纤芯凹陷处共振功率输出的高灵敏度光纤加速度计。传感探头具有紧凑的结构，即一段包含直光纤布拉格光栅的特定纤芯（具有明显纤芯凹陷）的短光纤 stub 通过纤芯自对准过程与另一根单模光纤熔接。利用飞秒激光侧面照明技术确保光栅写入区域定位精确且尺寸紧凑。在反射中实现了两个明确的纤芯共振：一个源自纤芯凹陷，另一个源自光纤纤芯。关键在于这两个反射共振中只有一个对光纤弯曲（和振动）表现出高灵敏度，而另一个对此免疫。对于低频（<10 Hz）和弱振动激励（<0.3 m/s）测量，通过简单监测高阶纤芯模式反射的总功率输出，所提出的传感器显示出更高的分辨率（1.7×10 m/s）。此外，该传感器同时提供了一个固有功率参考，以消除来自光源和传输线的不必要功率波动，从而提供了一种在低频下评估弱地震波的方法。
