FBG Sensor Array Intensity Equalization via Reflectivity Tuning
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Solution Overview
Problem
Wavelength multiplexed optical sensing systems using broadband light face challenges due to spectral non-uniformities in input light, leading to non-uniform intensity of reflected signals from fiber Bragg grating (FBG) sensors, which can enhance noise characteristics and complicate signal separation.
Innovation Solution
A compensated sensor array is implemented on an optical fiber, where FBG sensors have different optical characteristics such as reflectivity or attenuation values to equalize the intensity of reflected signals, addressing spectral non-uniformities and scattering losses, thereby reducing the signal-to-noise ratio differences between sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wavelength multiplexed optical sensing systems use broadband light input, then multiple FBG sensors can be disposed along a single optical fiber for simultaneous sensing, but spectral non-uniformities in the input light cause non-uniform intensity of reflected signals from different FBG sensors
Solution Approach 1:
The patent applies local quality by assigning different optical characteristics (reflectivity or attenuation values) to different FBG sensors based on their position in the wavelength multiplexed system. Sensors experiencing higher input light intensity are given lower reflectivity or higher attenuation, while sensors experiencing lower intensity are given higher reflectivity or lower attenuation. This local customization of optical properties compensates for the spectral non-uniformities and equalizes the output signal intensities across all sensors.
2Ease of manufacture
If FBG sensors have uniform optical characteristics, then manufacturing is simplified, but spectral non-uniformities enhance noise characteristics and complicate signal separation
Solution Approach 1:
The patent implements parameter changes by deliberately varying the optical characteristics (reflectivity or attenuation) of different FBG sensors to compensate for spectral non-uniformities in the broadband light source. By adjusting these parameters based on the expected input light intensity at each sensor's wavelength band, the system equalizes output signal intensities, thereby improving signal-to-noise ratio and facilitating better signal separation while maintaining manufacturing feasibility through controlled parameter variations.
3Adaptability or versatility
If FBG sensors are positioned at different locations along the optical fiber, then wavelength multiplexed sensing is enabled, but scattering losses cause non-uniform intensity distribution among sensor signals
Solution Approach 1:
The patent applies local quality by tailoring the optical characteristics of each FBG sensor according to its specific position along the optical fiber and the corresponding scattering losses at that location. Sensors positioned where scattering losses are higher are compensated with higher reflectivity or lower attenuation, while sensors in positions with lower losses have lower reflectivity or higher attenuation. This position-dependent optimization ensures uniform output signal intensities across all sensors despite the non-uniform scattering losses.
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 compensated sensor array ensures more uniform intensity of reflected light from FBG sensors, reducing noise and improving signal separation by equalizing the intensity of output signals, which can be within 10% or 20% of each other, thereby enhancing the accuracy and reliability of sensing data.
Implementation Method 1
each FBG sensor reflecting a different wavelength band
Implementation Method 2
The optical characteristic may comprise attenuation of input light
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
A sensor system includes an optical fiber. A set of wavelength shift sensors are inscribed on the optical fiber. The set includes at least one first wavelength shift sensor configured to reflect a first wavelength band of input light as a first optical output signal. The first wavelength shift sensor has a first value of an optical characteristic that modifies intensity of the first optical output signal. At least one second wavelength shift sensor is configured to reflect a second wavelength band of input light as a second optical output signal. The second wavelength shift sensor has a second value of the optical characteristic that modifies intensity of the second optical output signal, wherein the second value is different from the first value.