Integrated Optic Current Sensors Based on Silica Waveguide Devices

Silica optical waveguide devices are incorporated for constructing fiber-optic current sensors employing polarization-rotated reflection interferometry. The integrated optic current sensor (IOCS) we propose comprises a Y-branch splitter, phase modulator, half-wave plate, polarizer, and directional coupler. Each silica waveguide device was meticulously designed, fabricated, and characterized to ensure that it consistently demonstrated excellent performance and high reproducibility, making it suitable for integration into the IOCS system. A total of 122 IOCS devices were fabricated on a 6-in quartz wafer, and it was observed that the directional coupler devices, even when produced from different batches, displayed identical characteristics to confirm the exceptional fabrication reproducibility of silica waveguide devices. In our current-sensing experiments, the IOCS demonstrated an accuracy level in line with IEC 60044-8 class 0.2 standards, displaying exceptional linearity for a current of 9 kA
_rms
. Furthermore, during a continuous 24-hour current measurement, we consistently observed a stable measurement signal, with the relative error staying within a range of ±0.2%. In our temperature dependence experiment on the IOCS, we observed Hi-Bi spun fiber produced temperature dependent periodic retardation, which led to a degradation in the IOCS's extinction ratio.