Resonator Fiber Optic Gyroscope Laser Phase Noise Reduction
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Solution Overview
Problem
Conventional fiber optic gyros face challenges in accurately measuring rotation rates due to pathlength differences and noise in counter-propagating light beams, which affect the accuracy and stability of rotational rate measurements.
Innovation Solution
A resonator gyroscope design that includes tunable light sources, a Sagnac resonator, and resonance tracking electronics to generate beat frequencies from counter-propagating light beams, minimizing frequency drift and jitter by locking laser frequencies to resonance frequencies, and using a hollow core optical fiber to reduce measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fiber optic gyros use standard laser sources, then device complexity is reduced, but phase noise in counter-propagating light beams increases, degrading measurement precision
Solution Approach 1:
A reference laser is introduced as an intermediary component to mediate between the slave lasers and the resonator. The reference laser provides a stable frequency reference that enables phase locking of multiple slave lasers to the resonator frequency, thereby reducing phase noise in the counter-propagating light beams without requiring each slave laser to be individually ultra-stable
Solution Approach 2:
Phase locking feedback loops are implemented where the interference signal from combining counter-propagating beams is used to adjust the frequencies of slave lasers. The feedback mechanism continuously corrects frequency deviations and maintains phase coherence, reducing phase noise while preserving measurement accuracy
2Measurement precision
If multiple slave lasers are locked to a reference laser, then phase noise is reduced and measurement precision improves, but device complexity increases
Solution Approach 1:
Multiple slave lasers are merged into a common frequency reference system by locking them all to the same reference laser. This consolidation allows a single reference laser to stabilize multiple beams simultaneously, reducing the overall complexity compared to having independent stabilization systems for each laser while maintaining high measurement precision
3Measurement precision
If hollow core optical fiber is used, then pathlength differences are reduced and measurement precision improves, but manufacturing complexity increases
Solution Approach 1:
The optical fiber structure is changed from traditional solid core to hollow core configuration. This parameter change in the fiber's physical structure allows light to propagate through air rather than glass, significantly reducing pathlength differences between counter-propagating beams and improving measurement precision, despite the increased manufacturing complexity
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 design enhances the accuracy and stability of rotational rate measurements by minimizing noise and pathlength differences, allowing for precise determination of rotation rates with improved sensitivity and reduced costs using less expensive laser technology.
Implementation Method 1
The resonance frequencies for each of the CW and CCW paths through the coil are based on a constructive interference condition such that all light-waves having traversed the coil a different number of times interfere constructively at any point in the coil
Implementation Method 2
A rotation about the axis of the coil produces a different pathlength for clockwise and counterclockwise propagation, thus producing a shift between the respective resonance frequencies of the resonator, and the frequency difference indicates the rotation rate
Data Source
AI summary
A resonator gyroscope comprises a reference laser generator to produce a reference light; a first slave light source to produce a first slave light locked to the reference light; a second slave light source to produce a second slave light locked to the reference light; a resonator coupled to said first and second light sources, the resonator having first and second counter-propagating directions and resonance tracking electronics coupled to the Sagnac resonator to generate a first beat frequency based on a first resonance frequency for the first counter-propagating direction, a second beat frequency based on a second resonance frequency for the second counter-propagating direction, and a third beat frequency based on a third resonance frequency for the second counter-propagating direction; wherein the rotational rate of the resonator gyroscope is a function of the first, second and third beat frequencies.