Distributed Measurements with a Long Gauge FBG Sensor Using Optical Frequency Domain Reflectometry

(1st Report, System Investigation Using Optical Simulation Model)

Abstract

Optical fiber sensors have many advantages for structural health monitoring and are often used to monitor the strain distribution of structures. However, using Fiber Bragg Grating (FBG) sensors with a general interrogation system, e.g. Wavelength Division Multiplexing (WDM), permits only the measurement of average strain within the gauge length and moreover, a large number of FBG sensors may be necessary to monitor overall stress concentrations. A distributed strain sensor with a higher spatial resolution and longer sensing length is therefore desired for the accurate and effective monitoring of stress concentration. To meet this need, we present a new strain measurement system with a long gauge FBG sensor based on the principle of Optical Frequency Domain Reflectometry (OFDR) which enables us to measure fully distributed strain at high spatial resolution. In this paper, we describe the principle and optical simulation model of our proposed measurement system and show the results of numerical calculations.