RFOG Optical Circuit Using Beat Note Compensation for Lead Fluctuations
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Solution Overview
Problem
Resonator fiber optic gyros (RFOGs) face bias errors due to temperature fluctuations and time-varying electrical phenomena, which cause fluctuations in the optical frequencies of input light, leading to incorrect rotation rate measurements.
Innovation Solution
An optical circuit is implemented in the RFOG that includes a tapping device to pick off optical signals from within the resonator, a combiner to combine these signals, and photodetectors to generate a beat note signal. This setup compensates for lead fluctuations and reduces bias errors by processing the beat note signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical signals are circulated through multiple turns of the fiber optic coil to improve measurement sensitivity, then the rotation rate measurement precision is improved, but the bias errors due to temperature fluctuations and electrical phenomena increase
Solution Approach 1:
The patent implements a feedback mechanism where the beat note signal from photodetectors is processed to generate compensation signals. These compensation signals are fed back to correct the bias errors in the rotation rate measurement, thereby maintaining measurement reliability while preserving the enhanced sensitivity from multiple coil turns
Solution Approach 2:
The patent introduces an intermediary optical circuit including a tapping device, combiner, and photodetectors. This intermediary system extracts a portion of the circulating optical signals, combines them to generate a beat note, and uses this beat note as an intermediate measurement to detect and compensate for lead fluctuations, thereby isolating the main measurement from temperature and electrical interference
2Measurement precision
If the optical path length is increased by using multiple coil turns to enhance the Sagnac effect, then the rotation detection sensitivity is improved, but the system becomes more sensitive to lead line fluctuations
Solution Approach 1:
The tapping device extracts a portion of the optical signals from the resonator as an intermediary measurement. This intermediary signal path allows detection of lead fluctuations without disrupting the main circulating signals, enabling separate compensation of the harmful lead line effects while preserving the enhanced Sagnac effect
Solution Approach 2:
The patent extracts a portion of the optical signals from the resonator using a tapping device. This extracted signal is then combined with a reference signal to generate a beat note that specifically indicates lead fluctuations. By taking out this diagnostic signal, the system can identify and compensate for harmful lead line effects independently
3Reliability
If a tapping device is added to extract optical signals from the resonator for compensation, then the bias error compensation is improved, but the device complexity increases
Solution Approach 1:
The tapping device and combiner are designed to serve multiple functions: they simultaneously enable bias error compensation through beat note generation, maintain the resonator's primary rotation sensing function, and provide diagnostic information about lead fluctuations. This multi-functionality justifies the added complexity by delivering multiple benefits from a single added circuit
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
The optical circuit effectively reduces bias errors in RFOG measurements by accurately compensating for lead fluctuations, thereby providing more precise rotation rate information.
Implementation Method 1
When the RFOG is experiencing rotations, the two counter-propagating (e.g., CW and CCW) optical signals experience different path lengths while propagating around a rotating closed optical path within the coil. The difference in the two path lengths is proportional to the rotational rate 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, where light waves that traverse the coil a different number of times are in-phase or add constructively at any point in the coil.
Implementation Method 3
one or more photodetectors coupled to receive the combined output from the combiner, wherein the one or more photodetectors generate a beat note signal from the combined output
Data Source
AI summary
Systems and methods for compensating optical lead fluctuations in an RFOG include sources for generating first and second optical signals; an optical resonator; first and second lead lines connected to the sources and the resonator, wherein the sources couple the first and second optical signals into the first and second lead lines, and the first and the second lead lines couple the first and second optical signals into the optical resonator for propagation within the optical resonator in opposite directions; a tapping device coupled to the optical resonator that couples portions of the first and second optical signals out of the optical resonator; a combiner that combines the portions of the first and second optical signals to produce a combined output; and a photodetector that generates a beat note signal from the combined output.