Resonator Fiber Optic Gyroscope Back Reflection Cancellation
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Solution Overview
Problem
Resonator fiber optic gyros (RFOGs) face instability in rotation rate measurements due to double back-reflections, which cause interference between the main light beam and its reflected portion, leading to signal fluctuations and degradation in performance.
Innovation Solution
The implementation of highly symmetric configurations for clockwise (CW) and counter-clockwise (CCW) lightwaves with identical properties, such as phase modulation frequency, amplitude, and linewidth, along with the use of optical isolators to prevent back-reflections, effectively cancels rotation rate errors by averaging the oscillating errors induced by double reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If double back-reflections are present in the optical path, then lightwaves interfere with reflected portions causing signal fluctuations, but rotation rate measurement stability deteriorates
Solution Approach 1:
The patent converts the harmful double back-reflection interference into a beneficial cancellation effect by introducing a second reflection point that generates an error signal equal in magnitude but opposite in phase to the original error signal. This transforms the harmful interference into a self-correcting mechanism where the reflected light waves, originally causing instability, now produce canceling signals that eliminate the rotation rate measurement errors.
2Measurement precision
If environmental factors cause path length variation, then relative phase changes between interfering beams occur, but rotation rate instability increases
Solution Approach 1:
The patent implements a feedback mechanism where the error signal generated by double back-reflections is detected and used to adjust the optical system. The second reflection point creates an error signal that provides real-time compensation for path length variations caused by environmental factors, allowing the system to maintain measurement precision despite external disturbances.
3Reliability
If multiple laser beams with frequency separation are used, then beat noise frequencies move to high frequency region, but device complexity increases
Solution Approach 1:
The patent extracts and addresses the specific problem of double back-reflection interference separately from the general signal stability issue. Instead of implementing complex multi-beam frequency separation, the invention focuses on eliminating the harmful reflected components through strategic placement of reflection points, thereby maintaining signal stability with a simpler single-beam configuration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces rotation rate errors by several orders of magnitude, stabilizing the RFOG performance and improving its accuracy in high-end applications by minimizing the impact of double reflection-induced instabilities.
Implementation Method 1
use of optical isolators to prevent back-reflections
Implementation Method 2
monochromatic lightwaves from separately tunable lasers are typically phase modulated
Implementation Method 3
A fraction of the circulating lightwaves are coupled out of the ring cavity and directed to photodetectors to generate photocurrent (or voltage) signals
Implementation Method 4
senses rotation rates by measuring rotation induced resonance frequency difference of the RFOG ring cavity in two counter-propagating directions
Data Source
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AI summary
A resonator fiber optic gyroscope (RFOG) is disclosed that reduces rotation rate error instability. In one embodiment, the RFOG comprises a resonator optical ring cavity, a first light source in optical communication with the ring cavity and configured to generate a clockwise optical signal, and a second light source in optical communication with the ring cavity and configured to generate a counter-clockwise optical signal. The RFOG also includes a first optical component in optical communication with the first light source and the ring cavity. The first optical component is configured to prevent the clockwise optical signal from being back-reflected to the first light source. A second optical component is in optical communication with the second light source and the ring cavity. The second optical component is configured to prevent the counter-clockwise optical signal from being back-reflected to the second light source. In addition, a first optical detector and a second optical detector are optically coupled to the ring cavity.