Resonator Fiber Optic Gyroscope Intensity Modulation Control
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Solution Overview
Problem
Resonator fiber optic gyros face significant rotation errors due to intensity modulation generated during frequency or phase modulation, which existing technologies struggle to mitigate effectively, requiring high-speed and costly intensity modulators to reduce modulation by 60 dB at resonance detection frequencies.
Innovation Solution
A resonant fiber optic gyroscope system with a residual intensity modulation controller, featuring an intensity modulator optically coupled to a laser source and an optical tap device, utilizes a feedback servo generating a sinusoidal signal to adjust the amplitude and phase of the intensity modulator, canceling out residual intensity modulation at the resonance detection frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If high-speed intensity modulators (e.g., Lithium Niobate waveguides) are used to reduce intensity modulation by 60 dB, then intensity modulation is suppressed effectively, but optical loss increases, device size increases, and cost increases
Solution Approach 1:
The patent replaces high-speed electronic intensity modulators with acousto-optic modulators that use acoustic waves to modulate light. This substitution uses acoustic field control instead of high-speed electronic control, achieving intensity modulation suppression without requiring high-speed modulators, thereby reducing device complexity while maintaining effectiveness
Solution Approach 2:
The patent changes the operating parameters by using acoustic frequency modulation instead of direct high-speed electronic intensity modulation. The acousto-optic modulator uses acoustic waves at specific frequencies to achieve the desired intensity modulation suppression, transforming the control mechanism from electronic to acoustic domain
2Object-generated harmful factors
If high-speed intensity modulators are used to reduce intensity modulation, then intensity modulation is suppressed, but optical loss increases significantly
Solution Approach 1:
The patent substitutes high-speed electronic intensity modulators with acousto-optic modulators that have lower optical loss characteristics. The acoustic wave interaction with light in the acousto-optic modulator achieves the required intensity modulation suppression with significantly reduced optical energy loss compared to Lithium Niobate waveguide modulators
3Loss of energy
If low-loss intensity modulators are used, then optical loss is reduced and device size is minimized, but the speed is insufficient for prior art intensity servos
Solution Approach 1:
The patent replaces the requirement for high-speed electronic modulation with acousto-optic modulation. The acousto-optic modulator uses acoustic waves to control light intensity, achieving sufficient modulation speed for the intensity servo while maintaining low optical loss characteristics, thus resolving the speed-loss tradeoff
Solution Approach 2:
The patent employs periodic acoustic waves to modulate the light intensity in the acousto-optic modulator. This periodic acoustic action provides the necessary modulation speed through the acoustic frequency, achieving the required performance without needing ultra-high-speed electronic modulators
4Measurement precision
If existing frequency or phase modulators are used, then resonance detection is enabled, but intensity modulation errors are generated that limit RFOG performance
Solution Approach 1:
The patent introduces an acousto-optic modulator as an intermediary component between the frequency/phase modulator and the resonator. This intermediary uses acoustic waves to control the light intensity, suppressing the harmful intensity modulation errors generated by frequency or phase modulation while enabling resonance detection to proceed
Solution Approach 2:
The patent substitutes the direct frequency or phase modulation approach with an acousto-optic modulation approach. By using acoustic field interaction to control light intensity, the system achieves resonance detection capability while eliminating the intensity modulation errors that would otherwise limit RFOG performance
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 suppresses residual intensity modulation, reducing rate bias errors in the gyroscope without the need for high-speed intensity modulators, thereby enhancing performance and reducing costs.
Implementation Method 1
an intensity modulator optically coupled to receive a light beam from a laser source... a feedback servo... generating a sinusoidal feedback signal to the intensity modulator
Implementation Method 2
an optical tap device optically coupled to the intensity modulator
Implementation Method 3
the demodulating feedback servo generating a sinusoidal feedback signal... based on a residual intensity modulation detected by the demodulating feedback servo
Implementation Method 4
probing the resonator resonance frequency and determining rotation
Data Source
AI summary
Systems and methods for improved resonator fiber optic gyroscope intensity modulation control are provided. In one embodiment, a resonant fiber optic gyroscope (RFOG) having a residual intensity modulation (RIM) controller is provided. The controller includes an intensity modulator optically coupled to receive a light beam from a laser source modulated at a resonance detection modulation frequency, and an optical tap device optically coupled to the intensity modulator. The controller also includes a feedback servo coupled to the optical tap device and the intensity modulator, the demodulating feedback servo generating a sinusoidal feedback signal to the intensity modulator. The feedback servo adjusts an amplitude and phase of the sinusoidal feedback signal provided to intensity modulator based on a residual intensity modulation detected by the demodulating feedback servo.