Development of a novel high-frequency reciprocal structure fiber optical pulsed current sensor.

A novel all-fiber optic current sensor (FOCS) is designed specifically for the measurement of large transient currents based on the Faraday effect. A reciprocal symmetric structure is incorporated into the optical sensing loop, and the current dependent phase demodulation is achieved by using a passive optical fiber coupler and the homodyne detection scheme. This design offers several advantages, including structural simplicity, high voltage insulation, low noise, high linearity, and excellent frequency response, and is highly suitable for use in any system of high-voltage, high-power, and high-frequency in nature. A current source based on fast capacitor discharge is used for the bench-test of the FOCS system, and several laser sources with different wavelengths and linewidths have been used to test the FOCS performance. Experimental results show that the phase noise of the laser is independent of both wavelength and linewidth. The sensitivity of the FOCS system has been calibrated against a commercial Rogowski current sensor. This FOCS offers precise and flexible high-current pulse measurements with a measured phase noise of 1.4 × 10-3 rad, using a 1550 nm laser with a 1 kHz linewidth. The fully reciprocal sensing loop ensures that the phase noise remains unchanged as the loop length increases. These features make the FOCS a robust and adaptable tool for high-precision current sensing in challenging environments. Finally, the FOCS system has consistently demonstrated its superior and stable performance in terms of high-frequency response and low noise with minimal dependence on the laser parameters.