Fundamental Experiment in Real-time Strain Measurement of Multipoint Fiber Bragg Grating using Optical Frequency Sweeping

Abstract

With the objective of real-time monitoring of the structural integrity of man-made structures such as bridges, high buildings, and dams and areas of bedrock collapse and other such hazardous areas, we are attempting to use fiber Bragg grating (FBG) to construct a structural health monitoring system. To construct a multipoint strain measurement system with FBG, which is an optical fiber type sensor, we investigated ways to use FBGs that have the same reflection characteristics and FBGs that have different reflection wavelengths in multipoint measurement. The constructed system combines optical frequency sweeping with the multipoint FBG to accomplish measurement of the reflection wavelengths of multipoint FBG and real-time graphic display. This paper describes fundamental experiment on multipoint strain measurement, demonstrating that the constructed real-time measurement system can measure the reflection wavelengths of FBGs that have the same reflection characteristics and FBGs that have different reflection wavelengths every four seconds.