Thermal Error
Non-reciprocal phase shifts induced by temperature changes in a fiber optic coil cause measurable errors in interferometric gyroscopes. The shupe effect occurs when a temperature gradient moves through the fiber, affecting different parts of the counter-propagating light beams at different times. This leads to a false rotation signal even when the sensor is stationary.
Error Mechanism
As the temperature fluctuates, the refractive index and the physical length of the fiber change. Because the two light waves pass through the same point at different times, they experience different optical path lengths due to the shupe effect. This difference appears as an angular rate bias.
Mitigation Strategy
Manufacturers use specific winding patterns, such as the quadrupolar wind, to minimize the impact of the shupe effect. These patterns ensure that parts of the fiber equidistant from the center are placed close to each other. This causes both light waves to experience the thermal change simultaneously, cancelling out the error.
Thermal insulation and active heating are also used to keep the gradient as small as possible. Software compensation can further reduce the residual error by monitoring the temperature at multiple points on the coil. High-end tactical gyroscopes rely on these techniques to maintain stability.
Performance Constraint
This effect remains one of the primary noise sources in fiber optic gyroscopes. Controlling the shupe effect is the biggest challenge in scaling these sensors for smaller packages.