Rotationally Biased Fiber Optic Gyroscope Mechanical Dithering
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Solution Overview
Problem
Standard interferometric fiber optic gyroscope (IFOG) systems face challenges with phase modulation, including unwanted side effects like residual intensity modulation and optical attenuation due to direct optical phase modulators, which affect sensitivity and accuracy.
Innovation Solution
A mechanical bias modulation technique is introduced, where the fiber optic coil is physically rotated or dithered to impart a phase bias, utilizing a dither motor and optical encoder to enhance sensitivity without intruding into the optical path, thus avoiding excess optical loss and secondary effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct optical phase modulators (lithium niobate electro-optic modulator or fiber-stretching piezo modulator) are used to impart phase modulation, then phase modulation is achieved, but unwanted side effects occur including residual intensity modulation, optical attenuation, and wavelength dependent loss
Solution Approach 1:
The patent replaces direct optical phase modulators with a mechanical dithering system that physically oscillates the fiber optic coil or gyro assembly. This mechanical approach substitutes optical/electro-optic modulation with mechanical motion, thereby eliminating the harmful side effects of direct optical modulation while achieving the required phase modulation through the Sagnac effect
Solution Approach 2:
The patent introduces a mechanical dithering mechanism as an intermediary between the control system and the optical path. Instead of directly modulating the optical phase, the system uses mechanical oscillation of the fiber coil as a mediator to induce the desired phase modulation indirectly, avoiding contamination of the optical signal with intensity modulation and attenuation
2Measurement precision
If optical phase modulators are placed in the optical path to achieve phase modulation, then phase biasing is achieved, but excess optical loss and secondary effects are introduced
Solution Approach 1:
The patent eliminates optical phase modulators from the optical path entirely by substituting them with a mechanical dithering system. The mechanical oscillation of the fiber optic coil produces the necessary phase modulation through the Sagnac effect without introducing optical loss, thereby resolving the contradiction between achieving phase biasing and minimizing energy loss
3Measurement precision
If standard interferometric fiber optic gyroscope design is used with direct optical phase modulators, then phase modulation is achieved, but the system complexity and potential failure points increase
Solution Approach 1:
The patent simplifies the system by replacing complex optical phase modulators with a straightforward mechanical dithering mechanism. This substitution reduces device complexity by eliminating electro-optic modulators, high-voltage drivers, and associated control electronics, while maintaining the required phase modulation functionality through mechanical motion
Solution Approach 2:
The patent extracts and removes the optical phase modulator component from the system entirely. By taking out the complex optical modulation subsystem and replacing it with a simple mechanical dithering mechanism, the overall system complexity is reduced while the essential function of phase modulation is preserved through alternative means
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 increases the sensitivity of the fiber optic gyroscope by effectively biasing the phase modulation mechanically, improving accuracy and reducing unwanted effects, allowing for simultaneous biasing of multiple coils and optimal signal strength with minimal noise.
Implementation Method 1
a fiber optic coil optically coupled to the light source and configured to impart a Sagnac phase shift proportional to rotation
Implementation Method 2
a motor that periodically rotates, vibrates, or dithers the fiber optic coil to impart a biasing phase modulation to the optical signal
Data Source
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AI summary
A system for rotationally biasing a fiber optic gyroscope includes a fiber optic gyroscope assembly comprising a light source that emits an optical signal, an optical coupler in optical communication with the light source, and a fiber optic coil in optical communication with the light source.The fiber optic coil receives the optical signal through the optical coupler and imparts a phase shift proportional to rotation. A rate sensing detector in optical communication with the fiber optic coil receives the optical signal from the fiber optic coil through the optical coupler. A motor coupled to the fiber optic coil applies a periodic rotation to the fiber optic coil to impart a biasing phase modulation to the optical signal. A signal processing unit is coupled to the fiber optic gyroscope assembly and the motor. The signal processing unit converts a measured intensity of the optical signal to rotation rate data.