Hetero-core Spliced Fiber Optical Sensing System for an Environment Monitoring

J. Ocean Eng. Technol. 2007;21(3):46-51.

Kim, Young-Bok;Lee, Kwon-Soon;Watanabe, Kazuhiro;Sasaki, Hiroyuki;Choi, Yong-Woon;

Faculty of Engineering, Pukyang National University;Dept. of Electric Engineering, Dang-A University;Faculty of Engineering, Soka University;Faculty of Engineering, Soka University;Faculty of Engineering, Soka University;

구조물 모니터링을 위한 헤테로 코어형 광센싱 시스템

김영복;이권순;와타나베카즈히로;사사키히로유키;최용운;

부경대학교 공과대학 기계공학부;동아대학교 공과대학 전기공학과;SOKA 대학 공학부;SOKA 대학 공학부;SOKA 대학 공학부;

Keywords: Hetero-core, Optic fiber sensor, Optical time domain reflectometer(OTDR), Environment monitoring

핵심용어: 헤테로 코어, 광파이어 센서, 환경 모니터링

Abstract

A multi-purpose environmental monitoring system has been developed as a commercially available standard using the technique of hetero-core spliced fiber optic sensors, for the purposes of monitoring large-scale structures and preserving natural environments. The monitoring system has been tested and evaluated in a possible outdoor condition, in view of the full-scale operation at actual sites to be monitored. Additionally, the developed system in this work conveniently provides us with various options of sensor modules intended for monitoring such physical quantities as displacement, distortion, pressure, binary states, and liquid adhesion. Two channels of optical fiber line were monitored in each channel, three displacement sensor modules were connected in series, in order to examine the performance to a pseudo-cracking experiment in the outdoor situation and to clarify temperature influences an the system, in terms of the coupling of optical connectors and the OTDR stability. The results from the pseudo-cracking experiment agreed with the actual cracks, by means of calculation, based an the detected displacement values and their geometrical arrangement of the used sensor modules. The temperature change, ranging from 10 to $20^{circ}C$ resulting from the 10-days free running operation, was found to influence the system stability of ${pm}10{mu}m$, primarily due to the coupling instability of the used optical connectors. It was found that fusion splicing, rather than the use of connectors, reduced the fluctuation dawn to ${pm}2{mu}m$. The specification and performance of various option modules have been demonstrated to show the capability of inspecting various physical quantities by use of the single system, which would be suitable for multi-purpose environmental monitoring.