Resonator Fiber Optic Gyroscope Carrier Beat Frequency Tracking
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Solution Overview
Problem
Conventional resonator fiber optic gyros face difficulties in accurately tracking and measuring the beat frequency between carrier frequencies due to the presence of multiple sidebands, which complicates the determination of rotation rates.
Innovation Solution
The method involves modulating optical signals from two light sources to generate sidebands, combining a fraction of these signals to produce a combined signal, selecting a frequency range close to the carrier beat frequency, performing a fast Fourier transform (FFT) on the electrical signal, and tracking the carrier beat frequency to output a rate signal indicating the rotation rate of the resonator fiber optic gyroscope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical signals are modulated to generate sidebands for resonance tracking, then the ability to maintain resonance lock is improved, but the difficulty of detecting and measuring the carrier beat frequency increases due to sideband interference
Solution Approach 1:
The patent segments the frequency spectrum by applying a bandpass filter to isolate the carrier beat frequency from sideband frequencies. This separates the measurement target (carrier beat frequency) from interfering components (sidebands), enabling accurate frequency detection despite the presence of modulation sidebands in the optical signals
Solution Approach 2:
The patent introduces an intermediary processing step using a bandpass filter with specific frequency characteristics centered on the expected carrier beat frequency. This intermediary component mediates between the modulated optical signals containing multiple frequency components and the frequency measurement system, selectively passing only the carrier beat frequency for accurate measurement
2Adaptability or versatility
If multiple sidebands are present in modulated optical signals, then resonance frequency tracking capability is enhanced, but the precision of rotation rate measurement deteriorates due to frequency ambiguity
Solution Approach 1:
The patent extracts the carrier beat frequency signal from the composite modulated optical signal by using a bandpass filter tuned to the carrier frequency range. This extraction process removes sideband components that cause frequency ambiguity, isolating only the relevant carrier beat frequency information needed for precise rotation rate measurement
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 isolates and tracks the carrier beat frequency, providing accurate measurements of rotation rates despite the presence of sidebands, enhancing the measurement precision and reliability of rotation rate detection.
Implementation Method 1
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 2
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 interfere constructively at any point in the coil.
Implementation Method 3
The frequency difference, such as may be measured by tuning the CW beam and CCW beam frequencies to match the resonance frequency shift of the closed optical path due to rotation, indicates the rotation rate.
Data Source
AI summary
A method of measuring beat frequency comprises modulating a first optical signal and a second optical signal, wherein the first modulated optical signal includes a first carrier frequency and a first plurality of sideband frequencies and the second modulated optical signal includes a second carrier frequency and a second plurality of sideband frequencies. The method also comprises combining a fraction of the first modulated optical signal with a fraction of the second modulated optical signal into a combined signal and determining a carrier beat frequency. The method further comprises selecting a frequency range from the combined signal; performing a fast Fourier transform (FFT) on an electrical signal representing the selected frequency range; tracking the carrier beat frequency based on the FFT; and outputting a rate signal based on the tracked carrier beat frequency, the rate signal indicating a rotation rate of the resonator fiber optic gyroscope.