高精度光纤光栅地震计
摘要
光纤地震观测仪器具有传感器无源、抗电磁干扰性强、深井观测耐高温高压、抗雷击等优点,可为地震观测提供一种新的技术手段。光纤地震计的敏感元件采用相移光栅代替传统的光纤光栅,相比于传统的光纤光栅,其光谱线宽要窄4个数量级,可以获得了更高的反射光谱信噪比和更高的波长解调精度。对于相移光栅式光纤地震计,其反射光谱波长与所测的地震波具有良好的线性关系,只需要解调出相移光栅的波长漂移信号就可以推算得到地震波信息。采用该技术,可以实现精度在ng级、测量频带DC~50 Hz的震动信号测量。2015年4月-6月,在云南省昭通防震减灾局的协助和配合下,于昭通市巧家地震观测站进行了光纤地震计试验。可清晰记录临近发生的地震信号。
Fiber optic sensor based earthquake monitoring instruments have some advantages such as passive monitoring,immunity to EMI,reliability in high temperature and pressure environment,immunity to lightening,which can provide a new approach to earthquake observation. We propose a high resolution fiber optic seismometer based on phase-shift fiber Bragg grating( π-FBG). Compared with conventional FBG,the π-FBG has a narrower linewidth by four orders of magnitude,which result in lower noise level and higher resolution. The reflective wavelength of theπ-FBG is linear to the magnitude of earthquake wave and we can demodulate the earthquake information by demodulating the wavelength shift of π-FBG. A resolution of ng within bandwidth of DC-50 Hz is achieved. In April 2015,the fiber optic seismometer is installed in Zhaotong city,Yunnan Province. The earthquake events were well recorded.
引文
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