Cooperative Four-State Modulation for Sensitivity Enhancement in a Fiber Optic Gyroscope

Abstract

A highly sensitive portable fiber optic gyroscope has significant value in inertial navigation and geophysical exploration. However, the excessive relative intensity noise (RIN) generated by broadband light sources degrades the sensitivity of the interferometric fiber optic gyroscope (IFOG). To suppress RIN, we propose the cooperative four-state modulation scheme based on a source-sharing configuration. Reverse-phase square-wave modulation signals are applied to two minimum configurations. The modulation states in the configuration are cooperatively implemented and therefore have RIN compensation ability. In this study, a noise model is employed to guide the selection of modulation depths. Compared to the minimum configuration with conventional sinusoidal and square-wave modulation, the new scheme achieves a 20.0-fold and 4.7-fold decrease in self-noise, as well as an 18.0-fold and 4.3-fold decrease in angular random walk. In a test on detecting the rotation rate of the Earth, a selfnoise level of 55 nrad/s/Hz1/2 and an angular random walk of 1.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$ </tex-math></inline-formula> 10−4 deg/h1/2 are achieved using the proposed scheme with an enclosed area of only 25.5 m2, demonstrating superior sensitivity performance.