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Fiber-optic Gyroscope With Only Grain Size

Nov 27, 2018

Nature recently published research from the California Institute of Technology on the latest advances in fiber optic gyroscopes. As shown in the figure below, the gyroscope is similar in volume to rice grains and is 1/500 of the smallest fiber optic gyroscope currently available.

Gyros


Gyros, which evolved from the maritime era, are now used in cars, drones, portable devices, and wearable devices, and have become an essential part of the three-dimensional space.

Unlike inertial spin gyros in the nautical era, modern gyroscopes have evolved into a variety of categories based on operational principles, including laser gyros, fiber optic gyroscopes, and microelectromechanical gyroscopes (MEMS).


The fiber optic gyroscope discussed in this paper uses the principle of interference of light for orientation, and its function is based on the interference of light passing through the fiber coil.


Two laser beams are simultaneously injected into the fiber from both ends of the same fiber. Since the speed of light is fixed, in the case of rotation, the optical path of one beam will be slightly shorter than the optical path of the other beam, so that there is a phase difference between the two beams, and the phase difference can pass through the interferometer. Measured, the Segnik effect. In this way, the component of the angular velocity can be converted into a change in the interference pattern measured by the photodetector.


Due to the need to ensure the length of the fiber coil, the smallest fiber optic gyroscope currently has the size of a golf ball, limiting its potential for use in mobile devices. The breakthrough in this study was the creation of a fiber optic gyroscope with a volume of only a grain of rice, which is 1/500 of the volume of the smallest fiber optic gyroscope previously. It is worth mentioning that the accuracy of the volume is reduced and the accuracy of the phase difference that the device can detect is 1/30 of the previous one.


In the previous technical solution, since light is incident from both ends of the optical fiber, the signal is interfered by factors such as the quality of different parts of the optical fiber, thermal expansion and contraction, and the like. The researchers innovatively used a technique called reciprocal sensitivity enhancement to reduce the signal-to-noise ratio within the fiber, thereby shortening fiber length and reducing device size.


Because fiber optic gyroscopes are more accurate than the microelectromechanical gyroscopes (MEMS) used in mobile devices such as mobile phones today, this research will help improve the accuracy of three-dimensional orientation of mobile devices.