Interferometric Fiber Optic Gyroscope Off-Frequency Modulation
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Solution Overview
Problem
Interferometric fiber-optic gyroscopes face challenges in isolating the bias phase modulator signal from the rotation rate detector signal, leading to interference and reduced sensitivity due to the high power requirements of the bias phase modulator signal, making it difficult to achieve the necessary isolation of up to 160 dB.
Innovation Solution
Generating an off-frequency bias phase modulator signal with negligible power at the eigenfrequency of the gyroscope and using an electronic circuit to convert it to a signal with substantial power at the eigenfrequency, thereby minimizing interference with the rotation rate detector signal by keeping the bias phase modulator signal out-of-band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large power bias phase modulator signal is transmitted at the eigenfrequency to achieve high gyroscope sensitivity, then measurement precision is improved, but signal interference increases making isolation extremely difficult
Solution Approach 1:
The patent applies preliminary action by generating the bias phase modulator signal at an off-frequency before transmission, ensuring that the signal does not interfere with the rotation rate detector signal at the eigenfrequency. The frequency conversion is performed in advance at the modulator location, preventing interference from occurring in the first place rather than attempting to isolate it afterward.
Solution Approach 2:
The patent changes the frequency parameter of the bias phase modulator signal from the eigenfrequency to an off-frequency. This parameter change allows the signal to be transmitted without causing interference to the rotation rate detector signal, resolving the contradiction between maintaining signal power for sensitivity and avoiding interference.
2Device complexity
If the bias phase modulator signal is routed throughout the system sharing connectors with the rotation rate detector signal, then device complexity is reduced, but signal isolation becomes nearly impossible to achieve
Solution Approach 1:
By changing the frequency parameter of the bias phase modulator signal to an off-frequency, the patent enables reliable signal transmission even when routing signals share common paths and connectors. The frequency differentiation ensures that the bias signal does not corrupt the rotation rate detector signal, maintaining reliability without requiring complex isolation infrastructure.
3Measurement precision
If the bias phase modulator signal is transmitted at eigenfrequency with substantial power, then gyroscope sensitivity is maintained, but noise in the rotation rate detector signal increases
Solution Approach 1:
The patent performs frequency conversion in advance at the bias phase modulator location, converting the signal to an off-frequency before transmission. This preliminary action prevents the generation of noise at the eigenfrequency in the rotation rate detector signal path, eliminating the need for complex noise filtering while maintaining sensitivity.
Solution Approach 2:
The off-frequency signal acts as an intermediary, allowing the bias phase modulator signal to be transmitted without directly interfering with the rotation rate detector signal. The frequency conversion creates an intermediate state that resolves the conflict between maintaining signal power and minimizing noise.
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 noise in the rotation rate detector signal output by isolating the bias phase modulator signal, allowing for higher sensitivity and accuracy in inertial rate detection without the need for extreme isolation, simplifying the gyroscope design.
Implementation Method 1
An integrated-optic bias phase modulator is used to introduce a non-reciprocal phase shift to counter-propagating light beams
Implementation Method 2
interferometric fiber-optic gyroscopes are used in inertial navigation applications... to measure the inertial rate of the gyroscope
Implementation Method 3
using an electronic circuit, or other mechanism, to convert this off-frequency bias phase modulator signal to a signal that has substantial signal power at or near the eigenfrequency of the gyroscope
Data Source
AI summary
Interference in a rotation rate detector signal of an interferometric fiber-optic gyroscope from a bias phase modulator signal may be reduced or substantially avoided by transmitting one or more off-frequency signals having a frequency other than the eigenfrequency of the gyroscope towards a bias phase modulator, generating the bias phase modulator signal having a frequency substantially equal to the eigenfrequency of the gyroscope, and driving the bias phase modulator with the bias phase modulator signal.