Polymeric Integrated-Optic Bias Chip for Optical Voltage Transducers

The operating bias point of optical voltage transducers (OVTs) must be adjusted to a quadrature phase point through the compensation of residual birefringence induced by the optical fiber and sensor head. An integrated optical device consisting of a polymeric waveguide 3-dB coupler, TE-pass polarizer, thermo-optic phase modulator, and polarization converter was proposed for adjusting the operating bias point. A high-voltage sensor probe was prepared with a LiTaO₃ electro-optic crystal sandwiched by Teflon spacers. The operating point control was confirmed by measuring the output polarization change on the Poincaré sphere. Preliminary OVT experiment was performed by applying a high-voltage signal of 60 Hz, 4 kV_pp, and the sensor exhibited linear response with a sensitivity of 9.4 mrad/kV.