A quasi-distributed optical fiber sensor network for large strain and high-temperature measurements of structures

Abstract

Due to earthquake effects, buildings often experience large strains, leading to progressive collapses. Monitoring and assessing the large strain condition of critical buildings is of paramount importance to post-earthquake responses and evacuations in earthquake-prone regions. However, few monitoring system can work under such harsh environments. For their unique attributes such as compactness, immunity to electromagnetic interference and capability integrated within various types of structures and materials, optical fiber sensors are especially attractive for quasi-distributed strain sensing purposes in harsh environments. Nevertheless, the dynamic range of strain measurements of an optical sensor is limited by the elasticity of the optical fiber. In this paper, a quasi-distributed optical fiber sensor network based on extrinsic Fabry-Perot interferometer (EFPI) and long-period fiber grating (LPFG) sensors for both large strain and high temperature measurements has been developed. The sensor network combined several inline EFPIs and LPFGs by various couplers. Each EFPI sensor in the sensor network system has the capacity of large strain measurement up to 12% and each LPFG sensor here has a temperature measurement range of up to 700°C. To obtain strain and temperature information for multiple locations more efficiently, a hybrid LPFG/EFPI optical fiber sensor based sensor network system has been studied in this paper. Experimental results demonstrate that the proposed quasi-distributed optical fiber sensor network system is capable for both large strain and high temperature measurements. Therefore, the proposed optical fiber sensor network system can be applied to monitor the quasi-distributed strain of civil infrastructure in harsh environments.