Optical Gating in Fiber Optic Gyroscopes for Spike Suppression
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Solution Overview
Problem
Fiber optic gyroscopes (FOGs) experience performance degradation due to periodic spikes in the interferometer output signal caused by rapid changes in phase modulation, leading to saturation of photodetectors, increased electronic noise, and spurious demodulation of angular random walk and drift.
Innovation Solution
Implement optical gating to controlably time modulate optical signals within the FOG, synchronizing with phase modulation to prevent spikes from reaching the photodetector, thereby stabilizing the electronics and reducing crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase modulation is implemented in the sensing coil to linearize response and increase sensitivity, then measurement precision is improved, but periodic spikes occur in the interferometer output signal causing photodetector saturation and increased electronic noise
Solution Approach 1:
An optical gate is introduced as an intermediary component between the phase modulator and the photodetector. This optical gate selectively blocks the periodic spikes generated by rapid phase modulation changes while allowing the useful interferometer output signal to pass through, thereby preventing photodetector saturation and reducing electronic noise without compromising measurement sensitivity
Solution Approach 2:
The harmful periodic spikes are extracted and removed from the interferometer output signal using the optical gate. By timing the optical gate to close during the periods when spikes occur (synchronized with the phase modulation frequency), the spikes are separated and eliminated from the signal path to the photodetector, leaving only the useful measurement signal
2Stability of the object's composition
If rapid phase modulation changes are applied to bias the interferometer, then linearization of response is achieved, but spurious demodulation of angular random walk and drift occurs
Solution Approach 1:
The optical gate serves as a mediator that filters out the spurious artifacts generated by rapid phase modulation. By blocking only the spike portions of the modulated signal while preserving the underlying interferometer output, the optical gate prevents false demodulation signals that would otherwise corrupt angular random walk and drift measurements
Solution Approach 2:
The optical gate operation is synchronized with the phase modulation through feedback control. The gating signal is derived from the same clock that drives the phase modulator, ensuring precise timing alignment. This feedback mechanism allows the optical gate to consistently block spikes at the correct moments while maintaining the integrity of the measurement signal for accurate demodulation
3Object-generated harmful factors
If optical gating is implemented to suppress spikes, then electronic noise is reduced and photodetector saturation is prevented, but device complexity increases
Solution Approach 1:
The optical gate is designed to perform multiple functions simultaneously: it blocks periodic spikes, prevents photodetector saturation, reduces electronic noise, and maintains signal integrity for accurate demodulation. By consolidating these multiple beneficial effects into a single component, the added complexity is justified by the multiple problems it solves
Solution Approach 2:
The optical gate provides an optical solution to an electronic problem (spike-induced photodetector saturation and electronic noise). Instead of using electronic filtering or clamping circuits that would add electronic complexity and potentially introduce additional noise, the patent uses an optical gating mechanism that operates in the optical domain, substituting electronic remediation with an optical approach
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
Optical gating effectively suppresses spikes, improving the stability and accuracy of FOGs by preventing saturation and reducing noise, thus enhancing sensitivity and reducing angular random walk.
Implementation Method 1
at least one optical gate configured to controllably time modulate the input optical signals and/or the first and second optical signals prior to being combined
Implementation Method 2
to phase modulate one or both of the first optical signal and the second optical signal
Implementation Method 3
transmit the combined first and second optical signals to at least one photodetector
Implementation Method 4
transmit the first optical signal and the second optical signal to the optical fiber coil such that the first and second optical signals counterpropagate through the optical fiber coil
Data Source
AI summary
A fiber optic gyroscope includes an optical fiber coil, at least one optical circuit, and at least one optical gate. The at least one optical circuit is configured to receive input optical signals generated by at least one optical source, to split each input optical signal into first and second optical signals, to phase modulate one or both of the first and second optical signals, to transmit the first and second optical signals to the optical fiber coil such that the first and second optical signals counterpropagate through the optical fiber coil, to receive the first and second optical signals after counterpropagating through the optical fiber coil, to combine the first and second optical signals after counterpropagating through the optical fiber coil, and to transmit the combined first and second optical signals to at least one photodetector. The at least one optical gate is configured to controllably time modulate the input optical signals and/or the first and second optical signals prior to being combined, said time modulating synchronized with said phase modulating.