Double-polarization fiber ring interferometer based on a single-mode isotropic fiber for gyroscopy

Abstract

We propose and implement the scheme of a whole-fiber double-polarization ring interferometer based on an isotropic fiber for gyroscopy purposes. The results of an experimental study of the output signal of the interferometer based on the proposed scheme are presented. The shift of the zero point of the interferometer signal (at a level of 3 • /h) and the drift of the zero point (at a level of 1 • /h) are determined. The rotation sensitivity of the interferometer is measured. It amounts to 0.1•/h, which agrees well with the calculation allowing for the shot noise of the photoelectric current at the output of the scheme.Recently, the fiber gyroscopy based on fiber ring interferometers has reached the level of industrial manufacturing. A number of companies in the world (see review papers [1, 2]) manufacture fiber gyroscopes using anisotropic filaments. Some companies produce a special anisotropic noncircular D-fiber which is convenient for the development of dividers and polarizers. However, it should be noted that anisotropic fibers are much more expensive than isotropic ones (by a factor of up to 100). Therefore, designers can be interested in studying the possibility to use isotropic fibers in gyroscopes having medium accuracy ratings. It is the purpose of the present paper to demonstrate the features of the proposed scheme using an isotropic fiber. This scheme allows one to obtain low values of the zero-point shift and drift of the interferometer signal and achieve the device sensitivity at a level of 0.1 • /h. This sensitivity is close to the ultimate sensitivity determined by the quantum (shot) noise and the noise of the radiation source. It will be clear from the further discussion that the sensitivity can be increased by increasing the power of the source and decreasing its noise. The noise level can be decreased by extending the source bandwidth or compensating the noise by allowing for the phase increment of the waves in the circuit. The latter requirement complicates development of schemes with compensation. Studying the reasons for the appearance of parasitic signals at the output of a fiber ring interferometer and the ways for their removal (see our works [2, 4] and works [5, 10] of other authors) made it possible to develop the criteria for the positioning and adjustment of the components of the isotropic-fiber ring interferometer, under which the additional signals not related to the rotation are absent at the output. These criteria are as follows.1. The difference between the optical paths of induced polarization modes of the circuit fiber whose anisotropy is determined by winding of the isotropic fiber on a coil with a sufficiently small radius should exceed the coherence length of the used light source. The relation of the birefringence to the winding radius and the diameters of the core and the shell is given in [1; p. 67]. The achieved incoherence of the waves transmitted along the orthogonal anisotropy axes of the circuit allows one to reduce the influence of the

Polarization nonreciprocity suppression of dual-polarization fiber-optic gyroscope under temperature variation

“…Different from the polarization-maintaining scheme with its single-polarization operation, the optical compensation scheme allows two orthogonal polarizations to propagate simultaneously. Actually, the benefit of using two polarizations has been discussed in some early studies [12][13][14][15][16]. Our recent theoretical and experimental findings further indicate that PN errors of two polarizations possess opposite signs, thus they can be optically canceled out when two polarizations are balanced in their intensity.…”