Fiber Bragg Grating Interrogator With Overlapping Spectral Ports
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Solution Overview
Problem
The existing fiber Bragg grating (FBG) and arrayed waveguide (AWG) health monitoring systems face challenges in sensitivity due to the difficulty in precisely positioning the initial Bragg wavelength between the center wavelengths of the AWG output ports and the large dynamic range of the FBG, which can cause wavelength shifts outside the spectral range of the output ports, leading to inaccurate wavelength determination.
Innovation Solution
A fiber Bragg grating interrogator assembly with a spectrally selective device having multiple output ports with overlapping spectral ranges, ensuring the Bragg wavelength falls within the spectral ranges of at least three successive ports over the dynamic range, enhancing sensitivity and allowing accurate wavelength determination by distributing the power spectrum across these ports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the initial Bragg wavelength is positioned precisely between the center wavelengths of two output ports to maximize sensitivity, then the sensitivity is improved, but the difficulty of installation and positioning increases
Solution Approach 1:
The spectral range is divided into multiple overlapping output ports (at least three successive ports) instead of using only two ports. This segmentation allows the Bragg wavelength to be distributed across multiple ports, eliminating the need for precise positioning between two ports while maintaining sensitivity through the overlapping spectral ranges.
2Adaptability or versatility
If the Bragg wavelength is allowed to shift over a large dynamic range, then the measurement range is improved, but the wavelength may shift outside the spectral range of output ports causing inaccurate determination
Solution Approach 1:
Multiple output ports with overlapping spectral ranges are configured to collectively cover the entire dynamic range of the Bragg wavelength. Each port contributes to monitoring a portion of the spectral range, and the overlapping regions ensure continuous and accurate wavelength determination across the full dynamic range without gaps or losses.
3Device complexity
If only two output ports with non-overlapping spectral ranges are used, then the device complexity is reduced, but signal power may be lost between the ports
Solution Approach 1:
The system transitions from a two-dimensional spectral allocation (two non-overlapping ports) to a multi-dimensional overlapping allocation (at least three successive ports with mutual overlap). This dimensional change ensures that every portion of the spectral range, including the overlapping regions, is captured by multiple ports, preventing any signal power loss.
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
This configuration increases the sensitivity and accuracy of Bragg wavelength determination, maintaining constant sensitivity throughout the dynamic range and preventing signal loss or hiding of the response within spectral ranges, thus overcoming the limitations of the conventional systems.
Implementation Method 1
a fiber Bragg grating (FBG)... configured to illuminate the fiber Bragg grating to solicit a response therefrom
Implementation Method 2
a spectrally selective device having an input port and a plurality of output ports... configured to provide a spectral energy distribution of a response of the FBG that is received on the input port, onto the output ports
Data Source
AI summary
A fiber Bragg grating interrogator assembly is described. Examples of the fiber Bragg grating interrogator assembly include an optical fiber including a fiber Bragg grating having a variable Bragg wavelength (λB) and a dynamic range of interest (Δλdyn,B) over which the Bragg wavelength (λB) can shift during use. The fiber Bragg grating interrogator assembly also includes a response analyzer having a spectrally selective device with an input port to which the optical fiber is operably connected, and a plurality of output ports of which each output port is associated with a respective spectral range (Δλn). The spectral ranges (Δλn, Δλn+1, Δλn+2) of each at least three successive output ports partially overlap, such that the FBG's Bragg wavelength (λB) falls inside the spectral ranges (Δλn, Δλn+1, Δλn+2) of at least three successive output ports over the dynamic range of interest (Δλdyn,B) of the FBG.