Modelling of Fibre-Optic Gyroscopes with Low-Coherence Light Sources

• Published in: International journal of modelling & simulation Vol. 25; no. 2; pp. 71 - 78
• Main Authors: Seidel, C., Trommer, G.F.
• Format: Journal Article
• Language: English
• Published: Anaheim, CA Taylor & Francis 01.01.2005; Calgary, AB Acta Press; Zürich
• Subjects: Applied sciences; Circuit properties; coherence; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Fibre-optic gyroscope; Integrated optics. Optical fibers and wave guides; interference; modelling; Optical and optoelectronic circuits; polarization; Waveform; Integrated optics; Temperature dependence; Fiber optic gyroscopes; Polarization; Light source; coherence; Fibre-optic gyroscope; modelling; Fiber optic sensors; Optimal design; Signal interference; Experimental result; Light coherence; Numerical simulation; System simulation; interference; Mathematical model; System analysis
• ISSN: 0228-6203; 1925-7082
• DOI: 10.1080/02286203.2005.11442320

Although much research has been done on fibre-optic gyroscopes (FOG), these sensors often show bias errors, that is, 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. The authors present a new simulation tool for modelling interferometric fibre optic sensors with inclusion of polarization and coherence effects. It allows, for the first time, modelling of the FOG signal quantitatively considering temperature dependence, light source parameters, and all perturbations and interferences between them with the corresponding degree of coherence. The authors analyze the gyroscope design, which leads to a localization of a bias error source that has not yet been described. 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 temperaturedependent bias errors. Guidelines for an optimum design avoiding the perturbing interferences are given.