Bias error in fiber optic gyroscopes due to elastooptic interactions in the sensor fiber

It has become a standard to use Shupe's nonreciprocity formula(1) for calculating the thermally induced bias error in fibre gyroscopes. This effect is initiated by thermal waves propagating through the material. However, it seems as if it has not been recognized yet that elastooptical interactions in the fiber can also lead to a nonreciprocity effect. In this case it is not required that a thermal wave propagate through the material, a simple temperature change - even if homogeneous - would have the same effect. In this contribution, we demonstrate the nature of the effect and, based upon the standard architecture of a sensor coil assembly, report on calculations (including FEM) elucidating the origination of elastic stress leading to a nonreciprocity.