Highly sensitive fiber-optic accelerometer by grating inscription in specific core dip fiber

• Main Authors: Qiangzhou Rong, Tuan Guo, Weijia Bao, Zhihua Shao, Gang-Ding Peng, Xueguang Qiao
• Format: Article
• Language: English
• Published: Nature Publishing Group 2017-09-01
• Series: Scientific Reports
• Online Access: https://doi.org/10.1038/s41598-017-12322-6

Abstract 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/s2) measurement, the proposed sensor shows a much higher resolution (1.7 × 10−3 m/s2) 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.