Dynamic Bias Offset in Resonator Fiber Optic Gyroscopes
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Solution Overview
Problem
Resonator fiber optic gyroscopes (RFOGs) face bias instability due to backscattered light, which decreases sensitivity at low rotation rates and increases error signals, making it difficult to accurately measure rotation rates.
Innovation Solution
Implementing a dynamic bias offset operation by introducing an offset frequency between the two light waves propagating in opposite directions within the fiber optic resonator, which is dynamically adjusted to ensure the interference is always outside the rotation rate signal frequency, thereby filtering out errors and increasing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the laser beams are tuned to the resonance frequencies of the fiber optic ring resonator, then the measurement precision is improved, but backscattered light causes bias instability and decreases sensitivity at low rotation rates
Solution Approach 1:
The patent applies preliminary anti-action by introducing an offset frequency between the CW and CCW laser beams before they enter the resonator. This pre-established frequency difference prevents backscattered light from interfering with the measurement signal, as the offset frequency shifts the interference signals outside the rotation rate measurement bandwidth. The offset is applied in advance through frequency modulation of one of the laser beams, creating a protective frequency separation that eliminates bias instability caused by backscatter.
Solution Approach 2:
The patent implements parameter changes by dynamically modulating the frequency of one laser beam at an offset frequency. This changes the frequency parameter of the light wave from a static resonance frequency to a dynamically varying frequency with an offset component. The offset frequency acts as a modulation parameter that separates the interference signals from the measurement band, allowing the system to maintain high measurement precision while eliminating bias instability through parameter transformation.
2Device complexity
If backscattered light is present in the resonator, then the device complexity remains simple, but the sensitivity at low rotation rates decreases and error signals increase
Solution Approach 1:
The patent maintains device simplicity while improving low rotation rate sensitivity by changing the frequency parameter of the laser beams. Instead of adding complex physical components to eliminate backscatter, the solution modifies the operational parameter (frequency) of the existing laser beams. By applying an offset frequency through modulation, the system separates interference signals from the measurement band, thereby maintaining sensitivity at low rotation rates without increasing device complexity.
Solution Approach 2:
The patent replaces potential mechanical or physical modifications to eliminate backscatter with an optical frequency modulation approach. Rather than introducing complex mechanical isolation systems or modifying the resonator structure, the solution uses optical parameter control (frequency offset) to achieve the same effect. This substitution maintains the simplicity of the mechanical structure while solving the sensitivity problem through optical domain manipulation.
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 reduces bias instability and enhances the gyroscope's ability to accurately measure low rotation rates by filtering out interference, improving overall performance and reducing errors.
Implementation Method 1
a first servo loop configured to lock the first optical beam to a resonance frequency of the fiber optic resonator, wherein the first servo loop comprises a modulator that modulates the first optical beam at a first resonant tracking frequency
Implementation Method 2
a second servo loop configured to lock the second optical beam to a resonance frequency of the fiber optic resonator, wherein the second servo loop comprises a modulator that modulates the first optical beam at a second resonant tracking frequency
Implementation Method 3
a filter configured to attenuate signals that result from the interference of the first optical beam with the second optical beam
Data Source
AI summary
Systems and methods for dynamic bias offset operation in RFOGs are provided. In certain embodiments, an RFOG system includes a fiber optic resonator; laser sources that launch first and second optical beams into the fiber optic resonator in opposite directions; a first servo loop configured to lock the first optical beam to a resonance frequency, the first servo loop including a modulator that modulates the first optical beam at a first resonant tracking frequency; a second servo loop configured to lock the second optical beam frequency, on average, to a resonance frequency, the second servo loop including a modulator that modulates the second optical beam at a second resonant tracking frequency, wherein the second optical beam is further modulated by a modulation frequency; and a filter configured to attenuate signals that result from the interference of the first and second optical beams.