SBS Ring Laser Gyroscope with Fixed Pump Separation
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Solution Overview
Problem
Conventional He-Ne ring laser gyroscopes are unsuitable for thermally extreme, high-shock, and high-vibration applications due to their reliance on fragile moving parts, which can lead to resonance frequency locking issues at small rotation rates, preventing effective measurement of angular rotation.
Innovation Solution
A ring-laser gyroscope design utilizing Stimulated Brillouin Scattering (SBS) with two optical pump beams propagating in opposite directions, separated by one Free Spectral Range (FSR), to prevent resonance frequency locking and generate a beat signal for measuring angular rotation without moving parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dither motor is used to prevent resonance frequency degeneration in conventional RLGs, then resonance frequency stability is improved, but device reliability deteriorates due to fragile moving parts in high-shock and high-vibration applications
Solution Approach 1:
The patent removes the dither motor from the system entirely, extracting the problematic moving part that causes reliability issues in high-shock and high-vibration environments. The solution uses a stationary optical resonator with integrated waveguides that eliminates mechanical components while maintaining the necessary frequency stability through optical path design.
Solution Approach 2:
The patent replaces the mechanical dither motor system with an optical-based solution using integrated waveguides on a silicon substrate. The frequency stability previously achieved mechanically is now maintained through optical resonance properties and waveguide design, eliminating moving parts while preserving the anti-degeneration function.
2Measurement precision
If two resonance frequencies are kept close together to measure small rotation rates, then measurement precision is improved, but the frequencies lock together preventing measurement
Solution Approach 1:
The patent introduces asymmetry in the optical path by using a non-reciprocal phase modulator that applies different phase shifts to clockwise and counter-clockwise propagating beams. This asymmetric modulation creates a frequency offset between the two resonance frequencies, preventing them from locking together while still allowing precise measurement of small rotation rates through the beat frequency signal.
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 allows for robust, high-performance angular rotation measurement in extreme environments without the need for dither motors, ensuring accurate rotation detection even at small rotation rates and tolerating high shock and vibration.
Implementation Method 1
an optical ring resonator configured to generate, in response to the first optical pumped beam, a first back-scattered Stimulated Brillouin Scattered (SBS) beam propagating in a direction opposite to a direction in which the first optical beam is propagating
Implementation Method 2
a detector coupled to the optical ring resonator and configured to determine an optical beat signal in response to the first and second back-scattered optical beams
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A ring-laser gyroscope which generates in an optical ring resonator and in response to a first pump beam, a first back-scattered beam propagating in a direction; generates in the optical ring resonator and in response to a second pumped beam, a second back-scattered beam propagating in an opposite direction; determines a first difference between the frequencies of the first and second back-scattered beams; reverses the directions of the first and second back-scattered beams; determines a second difference between the frequencies of the first and second back-scattered beams; determines a third difference between the first and second differences; and determines a rotation of the optical ring resonator in response to the third difference.