Gyrometer Intensity Noise Compensation via Adaptive Weighting
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Solution Overview
Problem
Interferometric fiber optic gyrometers face significant noise interference from intensity noise in broad-spectrum light sources, which affects the accuracy of rotational speed measurements.
Innovation Solution
A measurement system that employs a servo-control mechanism to optimize the weighting coefficient for compensating intensity noise, using a digital signal processing unit to modulate the phase difference with a multi-state periodic square modulation and apply sequential digital demodulation codes to isolate and reduce the noise impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a broad-spectrum light source amplified by stimulated emission is used, then spatial coherence is improved and coupling efficiency is enhanced, but intensity noise increases and measurement precision deteriorates
Solution Approach 1:
The light source output is divided into two separate beams: a measurement beam that passes through the interferometer and a reference beam that bypasses it. This segmentation allows independent processing of the two beams, enabling noise cancellation by comparing the measurement beam (affected by intensity noise) with the reference beam (unaffected by intensity noise but affected by common-mode environmental variations).
Solution Approach 2:
A reference beam is introduced as an intermediary element. This reference beam carries the same intensity noise characteristics as the measurement beam but without the phase modulation effects. By subtracting the reference beam signal from the measurement beam signal, the common intensity noise is cancelled out, improving measurement precision while maintaining the benefits of the ASE source.
2Measurement precision
If intensity noise compensation is implemented using conventional methods, then measurement accuracy is improved, but device complexity increases due to additional optical components and signal processing requirements
Solution Approach 1:
The reference beam path is merged with the measurement beam path at a beam splitter, combining both beams into a single detection channel. This merging allows the use of a single photodetector for both measurement and reference signals, reducing the number of required optical components and simplifying the overall system architecture while maintaining noise compensation capability.
Solution Approach 2:
The system uses itself to compensate for noise by generating an internal reference beam from the same light source. This self-service approach eliminates the need for external reference sources or complex additional compensation hardware, as the system's own light source and optical paths provide the necessary reference information for noise cancellation.
3Device complexity
If the weighting coefficient for noise compensation is fixed, then device complexity is reduced, but adaptability deteriorates when temperature or long-term changes occur
Solution Approach 1:
A feedback mechanism is implemented where the weighting coefficient is continuously adjusted based on the correlation between the measurement beam and reference beam signals. The system monitors the intensity noise characteristics in real-time and dynamically optimizes the compensation weight, enabling adaptation to temperature variations, aging effects, and other environmental changes without requiring manual recalibration or complex predictive models.
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
Effectively compensates for intensity noise, improving the accuracy of rotational speed measurements by minimizing statistical deviations and maintaining optimal compensation despite temperature or long-term changes in the interferometer.
Implementation Method 1
This coil creates the rotational speed dependence Ω via the Sagnac-Laue effect
Implementation Method 2
a phase modulator is placed at one end of the coil
Data Source
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AI summary
The invention relates to a system for the interferometric measurement of a physical parameter, comprising a spontaneous emission light source amplified through a stimulated emission, optically connected to a Sagnac ring interferometer, and two detectors, each supplying a measurement signal (SOUT) representative of the light output from the interferometer, and a reference signal (SREF) representative of the light output emitted by the source, which is affected by an excess relative intensity noise. According to the invention, this measurement is obtained from a difference between the measurement and reference signals, weighted by a weighting coefficient (β) which is controlled to minimise the statistical deviation of an additional weighted difference between signals (D RIN-OUTJ DRIN-REF) obtained by demodulating the measurement and reference signals by means of an additional digital demodulation sequential code (CSDN-RIN) insensitive to said parameter. The invention also relates to a gyrometer comprising such a measuring system.