Drift of an Optical Fibre Gyroscope Caused by the Faraday Effect and Its Reduction by Use of a Polarizing Fibre

The drift of fibre gyroscopes caused by a magnetic field via the Faraday effect is formulated in a simple model with a polarizing fibre as a sensing loop. It is found that polarizing fibre, which has a extremely large loss difference between two polarization modes, can make the drift less than that with polarization-maintaining fibre. In this case, the drift is inversely proportional to the square of the loss difference. Although currently available polarizing fibre must be improved to have a larger loss difference, by using such a polarizing fibre or an absolute single-polarization fibre, we can reduce the requirement for shielding the magnetic field and/or the way of winding the sensing loop. The use of these fibres is attractive for applications that demand ultra-low drift, for example, geophysical applications.