Digital Control and Demodulation Algorithm for Compact Open-Loop Fiber-Optic Gyroscope.

With the advantages of small size, low cost, and moderate accuracy, an open-loop fiber-optic gyroscope (FOG) has a wide range of applications around control and automation. For the most cost-sensitive applications, a simple and stable digital algorithm with a reduced control-circuit volume and cost is highly desirable to realize high-precision control of a FOG. In this work, a new algorithm for an open-loop FOG is proposed based on the discrete multi-point demodulation in the sinusoidal modulation period. Utilizing this algorithm, stable control and angular velocity calculation of a gyro are realized with effectively suppressed gyro error. The use of this algorithm greatly reduces the requirements for processing power and simplifies the gyro circuit. Based on this algorithm, a digital FOG with a volume of only 25 × 20 × 40 mm3 achieves a bias instability of less than 0.15°/h, an angle random walk (ARW) of less than 0.015°/√h, a start-up time of less than 1 s, and a 3 dB bandwidth beyond 160 Hz. This low-cost, compact, and high-performance gyro is sufficient to satisfy the requirements of applications in the navigation and control fields such as unmanned driving.

Compact and high-reliability fiber-optic open-loop gyroscope enabled by an in-fiber polarizer.

The performance of an open-loop fiber-optic gyroscope is strongly dependent on the optical characteristics of its polarizer. Here we report the implementation of an in-house fabricated 45° tilted-fiber-grating-based polarizer, for the first time on an ultra-fine diameter polarization-maintaining fiber platform in an open-loop fiber-optic gyroscope. This special in-line polarizer is proven to have the merits of high extinction ratio, broad spectrum, bendability, stretchability, temperature insensitivity, and high reliability, all of which make it a perfect match for practical fiber optic gyros that need to be packaged compactly without affecting performance. Our prototype fiber optic gyroscope has a compact volume of only ϕ35 × 20 mm2, achieving a bias instability of less than 0.1 °/h, full temperature bias stability of less than 1 °/h, and scale factor linearity of better than 200 ppm. This compact and high-performance fiber gyro enabled by TFG polarizer may promise great potential in the field of automation and control.

Tilted fiber grating polarizer in a 40-µm polarization-maintaining fiber.

The optical polarizer is a crucial component widely used in many optical systems and applications. Fiber-optic polarizers have the merits of excellent compatibility and ease of integration with other fiber components. We report an in-line polarizer enabled by a 45° tilted fiber grating inscribed into a specialty fiber for the next generation fiber-optic gyroscope, i.e., a 40-µm ultra-fine-diameter tiger-type polarization-maintaining fiber with which the size of fiber-optic sensors can be miniaturized. The results show that a 40-mm-long polarizer operates at a center wavelength of around 830 nm with high-performance characteristics, such as a polarization extinction ratio exceeding 30 dB, a low insertion loss of less than 1.5 dB, and a large 3-dB optical bandwidth more than 60 nm. This kind of fiber-optic polarizer may have a broad scope across applications and systems such as fiber lasers and sensors, especially high-precision fiber-optic gyroscopes.

Dual-input concave diffraction grating demultiplexer based on dielectric multidirectional reflectors: publisher's note.

This publisher's note corrects an affiliation in J. Opt. Soc. Am. A36, 1585 (2019)JOAOD60740-323210.1364/JOSAA.36.001585.

Dual-input concave diffraction grating demultiplexer based on dielectric multidirectional reflectors.

The conventional concave diffraction grating (CDG) is commonly operated as a coarse demultiplexer device due to significant increases in the chip size and cost for large dispersion. Compact dense wavelength multiplexing is proposed and demonstrated by utilizing a dual-input CDG integrated with dielectric multidirectional reflectors. This structure allows light beams incident from two different directions to be efficiently reflected and get diffracted into the respective output waveguides by a single grating, thus creating a doubled channel number and halved channel spacing while keeping the chip size constant. The dielectric multidirectional reflector is designed by one-dimensional photonic crystal theory and used as the grating tooth to provide high reflectivities over a wide angular range. Simulation results suggest that the dual-input CDG with incident angles of 1° and 6° exhibits efficiency of more than $-0.564 \,\,{\rm{dB}} $ and crosstalk less than $-21.2 \,\,{\rm{dB}} $.

Perfect matching of concave diffraction grating with continuously circular Bragg mirrors on SOI platform.

A concave diffraction grating (CDG), based on circular Bragg mirrors, was constructed on the 220 nm silicon-on-insulator (SOI) platform. This continuous and smooth dielectric mirror is employed to eliminate the extra scattering loss occurring at the connection with neighboring grating teeth. A perfect match between the Bragg condition and the grating condition was derived in order to determine the geometrical parameters of the grating profile. finite-difference time-domain (FDTD) simulation shows that the reflection of the designed Bragg mirror can be up to 99.7% over a broad bandwidth of 330 nm. And the grating with circular Bragg mirrors exhibits low insertion loss in a relatively high order of M=5 with some unwanted diffraction orders suppressed, thus creating a large dispersion while keeping compact structure.