Yosuke TANAKA^*, Tatsutoshi SHIODA^†, Takashi KUROKAWA, Junji OKA¹, Kazuyuki UETA¹, and Toshiharu FUKUOKA¹

Graduate School of Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
¹The Chugoku Electric Power Co., Inc., Hiroshima 730-8701, Japan

(Received November 27, 2008; Revised March 4, 2009; Accepted March 6, 2009)

We propose a novel power-line-monitoring system using optical fibers for transmitting power as well as signal. The principle is experimentally confirmed with a system composed of a monitoring side with a 1.5-μm laser diode, transmission line of a single mode fiber, and a sensing side having an efficient photovoltaic (PV) cell, electrical junction sensor, and low power liquid crystal optical modulator (LCOM). The PV cell generates the electrical power in the sensing side with a conversion efficiency of 20%. The LCOM is driven with low power of less than 50 μW, modulates the laser light with a signal indicating the power line condition, and transmits the optical signal. The developed sensing unit produces an optical signal having an extinction ratio of 15 dB with low optical power of 1.8 mW. Five systems were in operation for two years, faithfully monitoring the oil pressure in electrical cables every 20 min without incident.

Key words: laser power supply, fiber optic sensor, remote sensing, liquid crystal

^*E-mail address: tyosuke@cc.tuat.ac.jp
^†Present address: Nagaoka University of Technology, Nagaoka, Niigata 940-2188, Japan.