Abstract
A displacement sensor has been developed using a hetero-core spliced fiber optic element in a form of simple module structure and evaluated in terms of the accuracy, reproducibility, and sensitivity as a new displacement sensitive detector, for the purpose of the full-scale environmental monitoring. The developed sensor module is designed to be sensitive to a relatively large displacement in the range 0-5mm, for which a simple displacement-macrobending conversion mechanism in the module produces as the change in the sensor transmission loss ranging from 0 to a few dB. The experiment promisingly showed the sufficient reproducibility for its sensing operation with the accuracy less than 0.1% to the full span displacement of 5mm. Experiments have been made on the tandem connection of this sensors in a single fiber line, in which accuracy degradation has been elucidated in terms of the reduced S/N ratio for the OTDR measurement brought by tandemly connected sensors in the upstream of a sensor of interest. Discussions are also given on OTDR-based tandem-connection use and on required conditions associated with the averaging time, pulse width, and cursors setting from the practical point of view.
