In a study published in Electronics, researchers designed and optimized a resonant micro-optic gyroscope based on a transmissive silica waveguide ring resonator.
Study: Design and Optimization of a Resonant Micro-Optic Gyroscope Based on a Transmissive Silica Waveguide Resonator. Image Credit: aappp/Shutterstock.com
What is Optical Gyroscope Technology?
An optical gyroscope senses changes in direction or position using the Sagnac effect. In this way, it operates similarly to a mechanical gyroscope. However, these gyros are more reliable and resistant to electromagnetic perturbations than mechanical gyros because there is no moveable component in the rotation sensor unit.
Due to their wide dynamic range, high precision, and resistance to mechanical abrasion, optical gyroscopes have attracted much attention in navigational areas.
Commercial jetliners, ground vehicles orbiting satellites, and unmanned aerial vehicles depend on optical gyroscopes for safe operations.
Resonant Micro-Optic Gyroscope
A resonant micro-optic gyroscope is an advanced optoelectronic hybrid integrated sensor that has the potential to develop monolithic device integration and miniaturized all-solid-state electronics.
The resonant micro-optic gyroscope with a waveguide-type ring resonator has proven to be the optimum choice for the next generation of highly accurate, cost-effective, and compact optical gyroscopes.
The development of integrated resonant micro-optic gyros on a single chip has been discussed for years. It is advancing quickly due to the developments in integrated circuits and planar light waveguide circuit processes.
A variety of factors, including the effective area and quality factor of a resonator, are directly associated with the performance of a gyroscope. Its performance is also suppressed by backscattering noise, Fresnel back reflection, polarization fluctuation noise, and the Kerr effect.
However, the performance of a gyroscope can be enhanced by optimizing the properties of its resonator.
Ideal Resonator for Micro-Optic Gyroscope
The waveguide ring resonator is the primary sensing component of an optical gyroscope, and its performance directly affects the device’s accuracy. Therefore, the design and production of high-quality waveguide ring resonators have emerged as a critical research area for micro-optic waveguide gyros.
There are two fundamental types of ring resonators: transmissive and reflecting. Compared to the reflecting resonator, the transmissive resonator provides an additional coupler to resonate the light, resulting in an increased coupling loss and a drop in the resonator’s finesse, reducing the gyro’s sensitivity.
However, the transmissive resonator is preferable because its structure is more reciprocal and symmetrical and suppresses polarization fluctuations more effectively. In addition, no circulators are needed to construct the transmissive resonator in the gyroscope system.
Optimizing the Performance of Resonant Micro-Optic Gyro with Transmissive Waveguide Ring Resonator
Researchers designed a custom transmissive silica waveguide ring resonator with various gaps on a silicon substrate.
First, the transmissive resonator’s physical model was established, the transfer function was deduced, and the transmission coefficient was obtained at the maximum sensitivity.
Then, the optimal conditions for the resonant micro-optic gyroscope’s sensing optical waveguide resonator were achieved by examining the correlation between the gyroscope’s scale factor and the resonator’s transmission coefficient.
The incoming light source was a tunable laser with a 300 kHz spectral line width and a 1550 nm center wavelength. In addition, a triangle-shaped voltage signal was provided to the laser for linear frequency scanning.
An isolator was installed between the resonator and the laser to prevent the laser from being affected by the echo light. Afterward, the light was linked to the resonator. The resonator’s light output was transformed into an electrical signal using a photodetector. This enhanced the resonance spectrum’s visibility on the oscilloscope.
Significant Findings of the Study
The largest scale factor of all the resonators was reached at 1.34 mV/°/s with an open-loop system, and this result was in line with the proposed model’s predictions. In addition, the transmission loss of the silica optical waveguide was measured to be 0.017 dB/cm in the c-band of the spectrum using experimental methods.
The resonator’s quality reached 2.1x107, the highest among all previously recorded transmissive resonators. The designed gyroscope was almost the same size as the reflecting resonator and had nearly the same quality, zero-bias stability, and finesse.
Based on silicon dioxide transmissive waveguide ring resonators, the optical gyroscope’s index successfully exhibited bias stability of 183.7 °/h throughout a one-hour test. The other two resonator groups’ bias stability values were 191.7 °/h and 203.1 °/h.
The experimental results validate the viability of the proposed design methodology and offer inspiration for developing superior transmissive optical waveguide resonators. This study offers a strong foundation for enhancing the micro-optic gyroscope.
Reference
Zhang, W., Liu, W., Guo, H., Tang, J., & Liu, J. (2022) Design and Optimization of a Resonant Micro-Optic Gyroscope Based on a Transmissive Silica Waveguide Resonator. Electronics. https://www.mdpi.com/2079-9292/11/20/3355/htm
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