Highly Sensitive Fiber Optic Current Sensors with Integrated λ/4 Retarder

Fiber optic current sensors have made unprecedented contributions to the safety and security of power grids. The lambda/4 retarder, as a key component for generating circular polarization, can significantly enhance the performance of fiber optic current sensors (FOCS) due to its superior characteristics. However, traditional methods of fabricating homemade lambda/4 retarders have inherent flaws. This study replaced the traditional lambda/4 retarder in the all-fiber current sensor with an integrated lambda/4 retarder, which is proposed to convert linearly polarized light into circularly polarized light by controlling different spin rates of the spun fiber. The current sensitivity was increased from 0.235 to 0.404 mV/mA, and the noise was suppressed.