In response to the performance degradation problem of semi-conductor light sources and photodetectors in all-fiber optical current sensors, this paper proposes an online measurement technology scheme of all-fiber optical current sensor based on dual-redundancy configuration. Firstly, the optical path scheme and working principle of the dual-redundant all-fiber optical current sensor are proposed. Then, by establishing a dual band optical transmission model, the modulation and demodulation measurement scheme of the sensor is explored, and the current demodulation error and temperature influence error of the sensor are simulated and analyzed. Finally, a sensor prototype is built, and the nonlinear and temperature error tests are conducted on the sensor prototype. A real-time monitoring method for sensor accuracy is proposed and verified, and the effects of magnetic field interference and vibration interference are studied. The results show that within 5%Ir~ 120%Ir(Ir=500 A), the prototype measurement error is less than ±1%. Within the range of -40℃ to +80℃, the measurement error is less than ±0.1%, and accurate self-monitoring with the measurement error of less than ±0.2% is achieved. Under the influence of magnetic field interference and vibration interference, the measurement error is also less than ±0.2%. The developed dual-redundant all-fiber optical current sensor has achieved practical measurement accuracy requirements.