Optimization Strategies for Environmental Durability of Lithium Niobate Modulation-Based Fiber Optical Current Transducers

The optical circuit of fiber current transformers is prone to aging under long-term outdoor exposure to high/low temperatures and humid-heat environments, leading to decreased measurement accuracy or even failure. This paper proposes an innovative design scheme for lithium niobate modulation voltage closed-loop control. It introduces optimization strategies including high-strength integrated waveplate sensing fiber drawing process, sensing fiber winding process with magnetic leakage protection, and temperature compensation algorithm using $2 \pi$ reset technology. These strategies significantly improve the temperature characteristics and consistency of fiber current transformers, achieving a temperature coefficient better than $0.05 \%$ and linearity better than 0.98 across the full temperature range. The proposed high-strength integrated waveplate sensing fiber utilizes polarization-maintaining fiber with gradient spiral structure to replace waveplates, transforming concentrated polarization conversion of cut-type fiber waveplates into gradient polarization conversion. This optimization enhances the vibration response and durability characteristics of lithium niobate modulated fiber current transformers, meeting error limit requirements without installing butterfly springs and buffer washers.