In order to solve the problems that the existing electronic sensors for measuring the angle of the contact line isolation switch are difficult to obtain electricity and are susceptible to electromagnetic interference, a sensor for measuring the angle of the isolation switch is designed using an optical fiber sensor, using the idea of replacing the curve with straight , The rotation angle of the catenary isolation switch is converted to the optical distance measurement method for measurement, and the curve fitting algorithm is used to compensate for the nonlinearity of the designed optical fiber angle sensor. And install the compensated optical fiber angle sensor together with the high-precision Hall angle sensor on the SBE27.5kV/2000A isolating switch for experimental testing. The experimental results show that: compared with the commonly used BP neural network, the fitting degree of the optical fiber angle sensor corrected by the curve fitting algorithm has increased from 92.47% to 99.94%, and the linearity has increased from 9.66% to 0.84%. The optical fiber angle sensor The accuracy reached 0.677. It shows that the scheme has high accuracy and strong feasibility, and is suitable for monitoring the opening and closing of the catenary isolation switch.