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 are used in order to monitor strain distribution of a structure, because they have many advantages for structural health monitoring. By using Fiber Bragg Grating (FBG) sensors with a general interrogation system e.g. Wavelength Division Multiplexing (WDM) makes it possible to measure only average strain within the gauge length. In addition, it is necessary to allocate enough numbers of FBG sensors for monitoring stress concentration overall. Therefore, it is expected to apply a distributed strain sensor with the higher spatial resolution and the longer sensing length to accurate and effective monitoring of stress concentration. We present a new strain measurement system with a long gauge FBG sensor based on Optical Frequency Domain Reflectometry (OFDR), which enables us to measure fully distributed strain at special high spatial resolution. In this paper, we describe the principle and optical simulation model of the proposed measurement system and show results of numerical calculations.