A modified in-line Sagnac interferometer (MISI) with passive demodulation Technique (PDT) was proposed to immunize the fiber-optic current sensor (FOCS) from environmental perturbations. A large vibration to simulate the environmental perturbations with acceleration up to 12 g was applied to the lead fiber of the FOCS. The noise floor could be significantly suppressed (20 dB) by the MISI better than by a conventional interferometer. In the same dynamic environments, the PDT could make the FOCS achieve a good linear demodulation with average distortion rates always lower than 0.9%. In addition, all the sensitivities measured in both static and dynamic environments are all approximately 4.5 µrad/(Arms turns), which is close to the literatural data measured in static environments. These considerable achievements of high sensitivity, environmental immunity, and free electric shock concerns may lead FOCS’s to field-monitoring applications of power delivery lines.
© 1999 Optical Society of America
Original Manuscript: October 8, 1998
Revised Manuscript: January 5, 1999
Published: May 1, 1999
Hermann Lin, Wuu-Wen Lin, and Mao-Hsiung Chen, "Modified in-line Sagnac interferometer with passive demodulation technique for environmental immunity of a fiber-optic current sensor," Appl. Opt. 38, 2760-2766 (1999)