RFOG Resonance Hopping for Wide-Temperature Frequency Tracking
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Solution Overview
Problem
Resonator fiber optic gyros (RFOGs) face challenges in maintaining accurate rotation rate measurements due to temperature-induced resonance frequency shifts, which can exceed the limited tuning range of laser frequencies, especially in large environmental temperature changes, leading to operational issues.
Innovation Solution
Implementing resonance hopping by using a master laser to adjust the frequency of slave lasers within the fiber optic resonator, allowing the system to move between resonant modes and maintain operation within the laser's operational range, thereby compensating for temperature-dependent frequency changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the resonance frequency of the fiber optic resonator is maintained at a fixed mode, then the laser can operate stably under normal temperature conditions, but the system fails when temperature changes cause the resonance frequency to shift beyond the laser's tuning range
Solution Approach 1:
The patent implements dynamic resonance mode hopping, allowing the system to transition between different resonant modes as temperature changes. Instead of being locked to a single fixed resonance frequency, the system dynamically adjusts to new resonance modes when temperature-induced frequency shifts exceed the laser's tuning range, thereby maintaining operational reliability across varying temperature conditions
Solution Approach 2:
The system changes the resonance parameter by hopping between different resonant modes of the fiber optic resonator. When temperature causes the resonance frequency to shift beyond the laser's tuning capability, the system transitions to a different resonant mode with a shifted frequency baseline, effectively resetting the operating point and enabling continued stable operation under new temperature conditions
2Reliability
If thermoelectric coolers are used to stabilize laser frequency, then temperature stability is improved, but system cost and complexity increase
Solution Approach 1:
The system uses the natural resonance properties of the fiber optic resonator itself to provide frequency stabilization. By monitoring the resonance condition and automatically hopping to appropriate resonant modes, the system self-regulates its operating frequency without requiring external active stabilization components like thermoelectric coolers, thereby reducing system complexity while maintaining frequency stability
Solution Approach 2:
The patent removes the need for expensive thermoelectric cooler components by extracting the frequency stabilization function from active temperature control hardware and implementing it through passive resonance-based frequency reference and automated mode hopping logic, significantly reducing system complexity and cost
3Measurement precision
If the laser frequency is continuously tuned to track resonance frequency shifts, then frequency tracking accuracy is maintained, but the laser operates near its tuning limits where performance degrades
Solution Approach 1:
The system proactively hops to a new resonant mode before the laser tuning range is exhausted. By detecting when the current resonant mode is approaching the laser's tuning limits, the system preemptively transitions to a different resonant mode that provides a fresh frequency range, ensuring the laser always operates within its optimal performance envelope rather than continuously pushing at the boundaries
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 stabilizes the laser frequencies across a wide temperature range, reducing the need for expensive thermoelectric coolers and maintaining accurate rotation rate measurements even in extreme temperature variations.
Implementation Method 1
a coil of optical fiber coupled to the beam generating device that encircles an area... guide light along a solid glass core of the fiber
Implementation Method 2
The two counter-propagating (e.g., CW and CCW) beams experience different pathlengths while propagating around a rotating closed optical path, and the difference in the two pathlengths is proportional to the rotational rate that is normal to the enclosed area
Implementation Method 3
The resonance frequencies for each of the CW and CCW paths through the coil are based on a constructive interference condition such that all light-waves having traversed the coil a different number of times, are in phase, or add constructively, at any point in the coil
Implementation Method 4
the counter-propagating light beams are typically highly coherent and circulate through multiple turns of the fiber optic coil
Data Source
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AI summary
Systems and methods for performing resonator fiber optic gyroscope (RFOG) resonance hopping are described herein. For example, an RFOG includes a fiber optic resonator. The RFOG also includes a plurality of laser sources that each launch a respective laser for propagation within the fiber optic resonator. Further, the RFOG includes a threshold detector that determines when the operation of at least one laser source in the plurality of laser sources exceeds a threshold associated with the operational range of an aspect of the at least one laser source. Additionally, the RFOG includes a hop control logic that adjusts the frequency of at least one laser produced by the at least one laser source one or more resonant modes of the fiber optic resonator such that the aspect of the at least one laser moves away from the threshold towards a nominal value within the operational range.