Modeling of bias errors in fiber optic gyroscopes with new simulation tool

Abstract

Although much research has been done on fiber-optic gyroscopes (FOG), these sensors often show bias errors, i.e. the offset rotation rate varies with temperature and other environmental parameters. A low coherence light source is used to avoid undesirable interferences between error signals. Nevertheless in the standard FOG design it is possible that unintentionally optical paths match which may cause bias errors. The parasitic interferences may originate from reflections and polarization cross-coupling, whether intended or not. A new simulation tool for modeling interferometric fiber optic sensors with inclusion of polarization and coherence effects is presented. It allows for the first time to model the FOG signal quantitatively considering temperature dependence, light source parameters and all perturbations and interferences between them with the corresponding degree of coherence. An analysis of the gyroscope design is made which leads to a localization of a bias error source which has not been described yet. This problem may occur in every FOG with an integrated optics circuit (IOC) and a Lyot depolarizer. Reflection paths from the IOC match phase differences gained in the depolarizer and lead to temperature dependent bias errors. Guidelines for an optimum design avoiding the perturbing interferences are given.