Phase Biasing System for Optical Gyroscope Using Passive Non-Reciprocal Polarization Techniques

Abstract

Interferometric Fiber Optic Gyroscopes (IFOGs) are widely used in precision navigation systems due to their high sensitivity, robustness, and solid-state nature. To ensure linear response and accurate angular velocity measurement, a fixed $\pi/2$ phase bias is typically introduced between the clockwise (CW) and counter-clockwise (CCW) beams using active modulation components. However, these active elements increase system complexity, power consumption, cost, and susceptibility to thermal drift and long-term degradation. In this work, we present a novel IFOG configuration that, to the best of our knowledge, achieves for the first time, simultaneous operation at two quadrature points ($\pi/2$ and $3\pi/2$), providing natural noise suppression without relying on active components. This is made possible through the integration of a Non-Reciprocal Polarization-Dependent Phase Shifter (NRPPS), which introduces a pure $\pi/2$ passive phase shift. We detail the optical architecture and provide theoretical modeling using Jones calculus to demonstrate how the NRPPS element introduces passive quadrature biasing. Simulation results show that the proposed NRPPS-IFOG achieves significantly improved sensitivity, with Angular Random Walk (ARW) values up to 40x lower than those of conventional IFOGs, depending on the fiber coil length. The design further leverages quadrature-phase signal detection and adjustable temporal offsets between photodetectors to enhance noise suppression. This passive biasing approach eliminates the need for active modulation, offering reduced power consumption, improved stability, and enhanced long-term reliability.