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 <i>g</i> 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/(A<sub>rms</sub> 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
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)