Fiber-Optic Fabry Perot Demodulation System for High-Speed Phase Measurement
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Solution Overview
Problem
Traditional demodulation methods for fiber-optic Fabry Perot sensors, particularly those with multiple reflective surfaces, face challenges in achieving high demodulation speed for dynamic parameters like vibration and acoustic/ultrasonic signals due to limitations in hardware, making it difficult to meet the requirements for fast and accurate phase change parameter measurement.
Innovation Solution
A demodulation system and method that utilizes a light splitting module with broadband filters to divide and filter reflected light beams into multiple central wavelength beams, reducing the influence of fiber jitter and interference, and calculates phase change parameters using these signals, allowing for improved demodulation speed and accuracy by compensating the target phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional high-speed demodulation methods are used for fiber-optic Fabry Perot sensors with multiple reflective surfaces, then the demodulation speed can be maintained, but the measurement accuracy deteriorates due to interference from multiple cavities and fiber jitter
Solution Approach 1:
The patent segments the complex reflected light signal containing multiple cavity interference patterns into separate spectral components using a spectrum analyzer. By dividing the wavelength range into multiple segments and analyzing each segment independently with narrowband filters, the system can extract phase information from each cavity separately, eliminating interference between cavities while maintaining high demodulation speed through parallel processing of segmented signals.
Solution Approach 2:
The patent introduces a spectrum analyzer as an intermediary device between the light source and the detection system. This intermediary separates the complex reflected light into its spectral components, allowing the system to identify and process signals from different cavities at distinct wavelengths. The spectrum analyzer acts as a mediator that transforms the problematic multi-cavity interference into separable spectral channels, enabling accurate phase measurement without sacrificing demodulation speed.
2Measurement precision
If Fourier transform method is used to demodulate multi cavity FP sensor signals, then the measurement accuracy improves by handling multiple frequencies, but the demodulation speed deteriorates due to computational complexity
Solution Approach 1:
The patent replaces the computational Fourier transform method with an optical filtering approach. Instead of using complex mathematical algorithms to separate multiple frequencies, the system uses physical narrowband filters at different wavelengths to directly isolate signals from individual cavities. This substitution of optical processing for computational processing dramatically reduces processing time while maintaining the ability to measure multiple parameters simultaneously, achieving both high accuracy and high speed.
Solution Approach 2:
The patent changes the approach from temporal-spectral analysis (Fourier transform) to spatial-wavelength separation using fixed wavelength filters. By selecting specific wavelength parameters corresponding to each cavity's resonance peak and using narrowband filters centered at these wavelengths, the system directly extracts phase information without requiring computationally intensive transformation algorithms, thereby achieving fast demodulation of multi-parameter signals.
3Measurement precision
If cross-correlation method is used to find maximum value by correlating sensor spectrum with ideal spectrum, then the measurement accuracy improves, but the demodulation speed deteriorates due to processing time
Solution Approach 1:
The patent performs preliminary spectral separation using narrowband filters before detection, rather than performing correlation processing after signal acquisition. By pre-filtering the reflected light at specific wavelengths corresponding to each cavity's resonance peak, the system obtains clean, isolated signals that directly represent the phase information. This preliminary action eliminates the need for time-consuming cross-correlation computations, achieving both high accuracy and high speed through optical pre-processing.
4Measurement precision
If non-scanning cross-correlation method is used with low coherent interference, then the measurement accuracy improves by obtaining maximum intensity position, but the demodulation speed deteriorates due to hardware limitations
Solution Approach 1:
The patent exploits the periodic resonance characteristics of Fabry-Perot cavities at specific wavelengths. By using narrowband filters tuned to the resonance wavelengths of different cavities, the system periodically selects and detects signals at these predetermined wavelengths. This periodic filtering approach leverages the natural resonance periods of the cavities, enabling fast extraction of phase information without requiring scanning or complex correlation operations, thus achieving high speed and high accuracy simultaneously.
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 system effectively reduces the impact of fiber jitter and interference, enabling accurate and fast demodulation of phase change parameters for dynamic parameters, thereby meeting the high-speed demodulation requirements for applications like vibration and acoustic/ultrasonic signals.
Implementation Method 1
a filter module, a receiving module and a processing module. Said transmitting module transmits a light beam with a predetermined wavelength range, said fiber-optic Fabry Perot sensor receives said light beam and forms a reflected light beam, said light splitting module includes at least three ports including a first port connecting said transmitting module, a second port connecting said fiber-optic Fabry Perot sensor and a third port connecting said filter module, said filter module includes a first filter unit which filters said reflected light beam to obtain a first light beam with a first central wavelength, a second filter unit which filters said reflected light beam to obtain a second light beam with a second central wavelength and a third filter unit which filters said reflected light beam to obtain a third light beam with a third central wavelength
Implementation Method 2
Fiber-optic Fabry Perot (FP) sensors have the advantages of small size, high temperature resistance, corrosion resistance, anti-electromagnetic interference, high sensitivity and high measurement accuracy
Data Source
AI summary
Some embodiments of the disclosure provide a demodulation system for obtaining phase change parameters by a fiber-optic Fabry Perot sensor. In an embodiment, the demodulation system includes a transmitting module, a fiber-optic Fabry Perot sensor, a light splitting module, a filter module, a receiving module, and a processing module. The transmitting module transmits a beam with a predetermined wavelength range. The fiber-optic Fabry Perot sensor receives the beam and forms a reflected light beam. The light splitting module is arranged between the transmitting module and the fiber-optic Fabry Perot sensor. The filter module obtains the first light beam, the second light beam, and the third light beam. The filter module has a broadband filter. The receiving module receives the first light beam, the second light beam, and the third light beam and converts them into the first signal, the second signal, and the third signal.