Three-Frequency Resonant Optical Gyrometer Backscattering
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Solution Overview
Problem
Resonant passive optical gyrometers face challenges due to backscattering-induced coupling between counter-rotating modes, leading to non-linearity in frequency response and performance degradation, which has hindered their industrial application.
Innovation Solution
A 3-frequency resonant passive optical gyrometer design that uses three beams at different frequencies, with one beam slaved to a cavity mode and the others to counter-propagating modes, minimizing coupling effects by ensuring sufficient frequency separation, and employs optical phase locking devices to maintain resonance, eliminating the need for acousto-optic modulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a passive resonant cavity is used to eliminate the need for gaseous amplifying medium and high-voltage electrodes, then device complexity is reduced, but backscattering-induced coupling between counter-rotating modes degrades measurement precision
Solution Approach 1:
The patent applies parameter changes by using three different optical frequencies (f1, f2, f3) instead of a single frequency. Each frequency is separated by an integer multiple of the free spectral interval of the cavity. This frequency parameter change allows independent probing of counter-rotating modes, preventing backscattering-induced coupling and non-linearity while maintaining the simplicity of the passive resonant cavity structure.
2Measurement precision
If three beams at different frequencies are used to probe counter-rotating modes, then measurement precision is improved by eliminating backscattering effects, but device complexity increases due to multiple lasers and frequency control
Solution Approach 1:
The patent implements multi-functionality by using a single laser source that generates three different optical frequencies. This single laser performs multiple functions: probing the cavity length through one frequency and measuring rotation through the other frequencies. The system also measures both cavity length and rotation speed simultaneously using the three frequencies, reducing the need for separate measurement systems and overall device complexity.
3Measurement precision
If frequency separation between beams is increased to minimize coupling effects, then measurement precision is improved, but the bandwidth requirement for photodiodes increases
Solution Approach 1:
The patent optimizes the frequency separation parameter by setting it to an integer multiple of the free spectral interval of the cavity. This specific parameter choice ensures sufficient frequency separation to minimize coupling effects between counter-rotating modes while keeping the absolute frequency differences within the bandwidth capabilities of standard photodiodes. The frequency differences are carefully selected to be compatible with photodiode bandwidth requirements.
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 design enhances the gyrometer's sensitivity and compactness, reduces thermal sensitivity, and is compatible with integrated optics, overcoming the limitations of backscattering and enabling more accurate angular velocity measurements.
Implementation Method 1
Each frequency is separated from the other two frequencies by a value corresponding to an integer multiple of the free spectral interval of the cavity
Implementation Method 2
Optical gyrometers are based on the principle of measuring the Sagnac effect. The latter induces, under the effect of rotation, a difference in travel time between two electromagnetic signals propagating in opposite directions along a ring path
Data Source
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AI summary
The invention relates to a resonant passive optical gyroscope (50) comprising a cavity (C) and operating with three frequencies, and comprising: - a first injection laser (L1) configured to inject a first optical beam (F1) into the cavity in a first direction, - a second injection laser (L2) configured to inject a second optical beam (F2) into the cavity in a direction opposite to the first direction, - a third injection laser (L3) configured to inject a third optical beam (F3) into the cavity in one of the two aforementioned directions, one laser among one of the injection lasers being chosen as the master laser (L1) having a master frequency (f1), the two other injection lasers being respectively designated first (L2) and second (L3) slave lasers having respectively a first (f2) and a second (f3) slave frequency,- a master control device (DA1) - a first control stage comprising a first (D2) and a second (D3) slave device, - a second control stage comprising a first (OPLL2-1) and a second (OPLL3-1) optical phase-locking device comprising respectively a first (Osc2) and a second (Osc3) slave oscillator configured to generate a first and a second radio frequency offset signal.