High Temperature Endurable Fiber Optic Accelerometer

Yeon-Gwan Lee,Chun-Gon Kim,Jin-Hyuk Kim

doi:10.1155/2014/571017

Abstract

This paper presents a low frequency fiber optic accelerometer for application in high temperature environments of civil engineering structures. The reflection-based extrinsic fiber optic accelerometer developed in this study consists of a transmissive grating panel, reflective mirror, and two optical fiber collimators as the transceiver whose function can be maintained up to 130°C. The dynamic characteristics of the sensor probe were investigated and the correlation between the natural frequency of the sensor probe and temperature variation was described and discussed. Furthermore, high temperature simulation equipment was designed for the verification test setup of the developed accelerometer for high temperature. This study was limited to consideration of 130°C applied temperature to the proposed fiber optic accelerometer due to an operational temperature limitation of commercial optical fiber collimator. The sinusoidal low frequency accelerations measured from the developed fiber optic accelerometer at 130°C demonstrated good agreement with that of an MEMS accelerometer measured at room temperature. The developed fiber optic accelerometer can be used in frequency ranges below 5.1 Hz up to 130°C with a margin of error that is less than 10% and a high sensitivity of 0.18 (m/s2)/rad.

Highlights

Over the past three decades, many types of fiber optic accelerometers (FOAs) have been developed because optical fibers (OFs) allow structural health monitoring within highly electromagnetic environments [1].optical fiber with fused silica is useful in a wide temperature range up to about 1000∘C [2] it depends on the optical fiber material such as fused silica and sapphire (Al2O3, single crystal alumina) [3, 4]
The fabricated sensor probe can be used for the 130∘C endurable fiber optic accelerometer in equilibrium temperature states the fabricated sensor in our paper may not be appropriate for steadily increasing temperature environments like most accelerometers due to sensitivity variation
For use in high temperature environments, the natural frequency change rate should be considered at the targeted temperature due to natural frequency reduction that occurs with an increase in temperature

Summary

Introduction

Over the past three decades, many types of fiber optic accelerometers (FOAs) have been developed because optical fibers (OFs) allow structural health monitoring within highly electromagnetic environments [1].optical fiber with fused silica is useful in a wide temperature range up to about 1000∘C [2] it depends on the optical fiber material such as fused silica and sapphire (Al2O3, single crystal alumina) [3, 4]. In order to resolve these problems, reflectionbased techniques using grating panel have been developed [12, 13] This resolved the difficulties in corner installations and complex cabling problems in multipoint sensing due to the 50% simplified cabling by employing collimated optical fibers as transceivers, which allows the fibers to be placed on only one side of the sensor case. This FOA was reported to withstand temperatures up to only 65∘C due to the use of epoxy for assembly. A performance test of the 130∘C endurable FOA was implemented through a comparison with a commercial low frequency accelerometer

Working Principles

Fabrication of a Prototype for High Temperature Environments

Findings

Conclusion