High Sampling Rate Optical Fiber Sensor Using Birefringence Modulation
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Solution Overview
Problem
Current optical fiber sensors, such as Bragg grating and Fabry-Perot sensors, face limitations in sampling rate due to the technology used in interrogators, which are typically limited to low frequencies (rarely exceeding 10 KHz), making them inadequate for measuring high-frequency perturbations like vibrations and mechanical stresses that can vary up to 100 KHz, and are sensitive to noise and require specific spectral alignment.
Innovation Solution
A fiber optical sensor system utilizing a broadband optical source, a polarization-maintaining fiber interferometer with a birefringence modulator, and a receiver configured to modulate and process high-frequency signals, allowing for high sampling rates without the need for spectral alignment, and using commercially available components to achieve flexibility and reduced noise sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If commercial interrogators based on spectral analysis with tuneable lasers or spectrometers are used, then many sensor elements can be read simultaneously through wavelength division multiplexing, but the sampling rate is limited to rarely exceeding 10 KHz
Solution Approach 1:
The patent replaces the traditional spectral analysis system (tuneable laser or spectrometer) with a Fourier transform-based optical processing system. This substitution enables simultaneous measurement of multiple sensor elements at high sampling rates by transforming the measurement domain from spectral analysis to temporal frequency analysis, achieving both multiplexing capability and high sampling rate (hundreds of kHz to MHz range).
Solution Approach 2:
The patent changes the fundamental measurement parameter from wavelength domain to time-frequency domain. By using Fourier transform to convert the optical signal from spectral representation to temporal frequency representation, the system achieves high-speed sampling while maintaining the ability to distinguish multiple sensor elements through their unique frequency signatures.
2Productivity
If high sampling rates of hundreds of kHz are required for measuring vibrations and mechanical stresses, then the limitations of commercial interrogators become critical, but achieving these rates requires specialized interrogation schemes
Solution Approach 1:
The patent replaces complex specialized interrogation hardware with a Fourier transform-based system that achieves high sampling rates using standard optical components. This substitution reduces device complexity while maintaining high sampling rate capability by leveraging mathematical transformation rather than specialized hardware.
3Productivity
If intensity-based measurement with linear filters is used to achieve high sampling rate, then the measurement spectrum becomes very limited and the system becomes very sensitive to noise
Solution Approach 1:
The patent replaces intensity-based linear filter measurement with Fourier transform-based optical processing. This substitution eliminates noise sensitivity issues by operating in the frequency domain where signal components can be clearly distinguished from noise, while simultaneously achieving high sampling rates through efficient optical Fourier transformation.
4Adaptability or versatility
If fiber-optic interferometers are used to achieve high sampling rates with adjustable FSR, then the system becomes sensitive to environmental noise and requires precise alignment
Solution Approach 1:
The patent replaces fiber-optic interferometer-based FSR adjustment with a Fourier transform-based system. This substitution eliminates environmental noise sensitivity while maintaining FSR adjustability through digital signal processing, as the measurement is performed in the frequency domain rather than relying on interferometric phase stability.
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 enables sampling rates of hundreds of kHz with reduced noise sensitivity and adaptability, allowing for accurate measurement of high-frequency perturbations using commercially available components at a low cost.
Implementation Method 1
The optical sensor is characterised in that the interferometer comprises at least one polarization-maintaining fiber (PMF), a birefringence modulator and a polarization controller. The birefringence modulator is suitable to receive signals modulated by said signal generator and to modulate consequently with high frequency the phase delay of both polarizations crossing said PMF fiber.
Implementation Method 2
the birefringence modulator is suitable to receive signals modulated by said signal generator and to modulate consequently with high frequency the phase delay of both polarizations crossing said PMF fiber
Implementation Method 3
Bragg grating sensors or Fabry-Perot sensors are highly versatile optical sensors as they respond well to many types of perturbations such as temperature variations, mechanical stresses, vibrations, pressure
Implementation Method 4
Fabry-Perot sensors are highly versatile optical sensors as they respond well to many types of perturbations
Data Source
AI summary
An optical fiber sensor includes optical sensor elements, for instance a plurality of multiplexed Bragg gratings, a broadband optical source, an interferometer with at least one polarization-maintaining fiber section with which a birefringence modulator, a signal generator and a receiver are associated. The optical birefringence in the propagation medium, i.e., in the polarization-maintaining fibre, combined with the birefringence of the birefringence modulator, produce in the interferometer the path difference and thereby the interference fringes which, appropriately processed according to the known technique, allow the measurement to be traced. The use of a birefringence modulator associated with the polarization-maintaining fiber allows a high-speed modulation of the interferometer, thus allowing high sampling rates of the sensor without having variations in responsivity depending on the alignment of the sensors with the interferential fringes of the interferometer.