The fiber optic coil is a component in the fiber optic gyroscope for the Sagnac phase difference between two counter-propagating light waves caused by the sensitive input angular velocity, so it is the main factor affecting the performance of the fiber optic gyroscope. Fiber optic coils can be divided into de-skeletonized fiber optic coils and skeletonized fiber optic coils. A fiber optic coil wound on a bobbin and used with the bobbin is a bobbin fiber coil. After being wound with a tooling, the optical fiber coil that is taken out after coil and used alone is a de-skeletonized optical fiber coil. In the fiber optic gyroscope, the four-pole symmetrical winding method is usually used to wind the fiber coil.
The main requirements of the fiber optic gyroscope for the fiber coil are:
1. Lower loss, especially for high-precision fiber optic gyroscopes and space applications;
2. High polarization performance to reduce polarization error. For polarization-maintaining and mixed-polarization fiber optic gyroscopes, the polarization crosstalk of the coil is required to be low, and for depolarization fiber optic gyroscopes, low polarization-related loss is required;
3. Higher symmetry to reduce errors caused by temperature changes and vibrations.
The fiber coil parameters that affect the fiber optic gyroscope mainly include the structure parameters of the fiber coil (including average diameter, fiber length, and the cross-sectional ratio of the fiber coil), loss, polarization crosstalk, stress distribution, and the symmetry of the fiber coil. Polarization crosstalk is limited by the fiber used.
The relationship between the structural parameters of the fiber optic coil and the performance of the fiber optic gyroscope
It can be known from the Sagnac effect that the longer the fiber length and the larger the average diameter of the fiber optic coil, the larger the scale factor, the higher the sensitivity of the fiber optic gyroscope, and the smaller the dynamic range. Therefore, the sensitivity and dynamic range of the gyroscope can be changed by changing the structure size of the optical fiber coil.
