RFOG Polarization Bias Error Reduction via Electro-Optic Phase Modulation
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Solution Overview
Problem
Resonator fiber optic gyroscopes (RFOGs) face bias instability due to light propagating in two polarizations, causing errors from interference between polarization states, which affects the accuracy of rotation rate measurements.
Innovation Solution
The system includes a fiber optic resonator with an electro-optically tunable device that modulates the phase difference between polarization components, stabilizing the interference between polarization states by adjusting the path length difference using a 90-degree rotation within the resonator and an electro-optically tunable device to reduce temperature-induced changes, thereby minimizing bias instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If light propagates in two polarizations in the resonator, then the RFOG can operate with standard fiber optic components, but polarization interference causes bias instability and measurement errors
Solution Approach 1:
The patent extracts and eliminates the harmful polarization interference by using a polarization controller to convert both polarization states into a single linear polarization state, thereby removing the source of bias instability while maintaining compatibility with standard fiber optic components
Solution Approach 2:
The patent changes the polarization state parameter by using an electro-optically tunable device to modulate the phase difference between polarization components, transforming the light from two polarization states to a stabilized single polarization state, thus resolving the measurement precision issue
2Device complexity
If the phase difference between polarization components is not stabilized, then the system structure remains simple, but temperature changes cause bias drift and instability
Solution Approach 1:
The patent implements a feedback control system where a processing unit receives electrical signals from photodetectors, calculates the rotation rate, and provides drive signals to the electro-optically tunable device to actively stabilize the phase difference between polarization components, compensating for temperature-induced changes
Solution Approach 2:
The patent replaces mechanical temperature compensation methods with an electro-optically tunable device that uses electrical signals to modulate the phase difference, providing more precise and rapid stabilization of polarization states against temperature variations
3Device complexity
If polarization interference is not compensated, then the system operates without additional components, but bias errors affect navigation accuracy
Solution Approach 1:
The patent introduces a polarization controller as an intermediary component that mediates between the dual-polarization light output and the detection system, converting the problematic two-polarization state into a stable single-polarization state to eliminate interference while maintaining system reliability
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 effectively reduces polarization-related bias errors by stabilizing the interference between polarization states, leading to more accurate rotation rate measurements and improved stability of the gyroscope output.
Implementation Method 1
an electro-optically tunable device in the resonator path configured to modulate the phase difference between polarization components in the first optical beam and polarization components in the second optical beam
Implementation Method 2
a photodetector that outputs an electrical signal that varies as a function of optical intensity
Implementation Method 3
errors arise because the light that propagates in the two polarization states of the resonator interfere with each other at the gyro output
Data Source
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AI summary
Systems and methods for reducing polarization-related bias errors in RFOGS are described herein. In certain implementations, an RFOG system includes a fiber optic resonator, one or more laser sources, wherein light from the laser sources launches first and second optical beams into the fiber optic resonator in opposite directions, and an electro-optically tunable devices in the resonator path configured to modulate the phase difference between polarization components in the first and second optical beams as the optical beams propagate within the fiber optic resonator. The system further includes at least one photodetector, wherein the polarization components of the first and second optical beams are incident on the photodetector, wherein the at least one photodetector provides an electrical signal, and at least one processing unit configured to receive the electrical signal and calculate a rotation rate for the RFOG and provide a drive signal for the electro-optically tunable device.