FBG Sensor Array Spectral Overlap Resolution
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Solution Overview
Problem
Existing fiber-optic sensor systems using Fiber Bragg Grating (FBG) sensors face challenges in accurately resolving and identifying multiple sensors operating within the same or overlapping spectral ranges, leading to limitations in sensor density and measurement dynamic range due to ambiguity in sensor identification.
Innovation Solution
The system employs a broadband or tunable optical source and wavelength-selective photodetectors to separate overlapping responses from FBG sensors by analyzing their unique Gaussian or near-Gaussian reflection profiles, allowing for identification and separation of individual sensor responses even when they occupy the same or partially overlapping wavelength ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple FBG sensors operate in overlapping wavelength ranges, then sensor density and measurement dynamic range increase, but sensor identification accuracy deteriorates due to spectral ambiguity
Solution Approach 1:
The patent segments the overlapping spectral responses by iteratively identifying and subtracting individual sensor profiles from the composite spectrum. Each sensor's Gaussian response is isolated through sequential processing, allowing accurate identification even when sensors operate in overlapping wavelength ranges. This segmentation transforms the ambiguous composite signal into distinct, identifiable components.
Solution Approach 2:
The system performs preliminary spectral profiling of each sensor's response characteristics before composite analysis. By pre-characterizing the Gaussian parameters (center wavelength, bandwidth, amplitude) of individual sensors, the system establishes reference profiles that enable accurate decomposition of overlapping spectra. This preliminary characterization is stored and used during iterative subtraction to maintain identification accuracy.
2Quantity of substance
If FBG sensors are positioned closer together to increase sensor density, then the number of sensors per fiber increases, but spectral resolution deteriorates due to reduced wavelength spacing
Solution Approach 1:
The patent transitions from relying solely on wavelength dimension separation to utilizing the temporal/iterative processing dimension. Instead of requiring spectral separation in the wavelength domain, the system processes the composite spectrum through iterative identification and subtraction steps, adding a temporal processing dimension that resolves overlaps. This allows sensors to be positioned closer together in wavelength while maintaining resolution through computational separation.
Solution Approach 2:
The system changes the operational parameters by allowing spectral overlap beyond traditional non-overlapping constraints. By modifying the assumption that sensors must operate in strictly separated wavelength bands, and instead using iterative profile subtraction with Gaussian parameter fitting, the system enables denser sensor positioning while maintaining identification accuracy through parameter-based separation rather than spectral gap requirements.
3Ease of manufacture
If the optical bandwidth is reduced to lower system cost, then system cost per sensor decreases, but the maximum number of resolvable sensors deteriorates
Solution Approach 1:
The patent replaces the mechanical/optical approach of requiring large spectral spacing between sensors with a computational signal processing approach. Instead of using broader optical bandwidths to physically separate sensor responses, the system uses iterative mathematical identification and subtraction algorithms to separate overlapping Gaussian profiles. This substitution of computational methods for optical separation enables more sensors to be resolved within narrower bandwidths, reducing system cost while maintaining sensor capacity.
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 approach enables a higher sensor density and increased measurement dynamic range within a given optical bandwidth, reducing system costs by allowing multiple FBG sensors to operate within the same wavelength range, while maintaining accurate identification and measurement capabilities.
Implementation Method 1
an optical source, such as either a broadband optical source or a tunable narrowband optical source such as a tunable laser source, sufficient to generate optical energy over at least one operating range of wavelengths
Implementation Method 2
FBG sensing element which reflects a relatively narrowband spectral slice (typically a fraction of 1 nanometer up to few nanometers) of optical power centered at a wavelength, known as Bragg wavelength
Implementation Method 3
examination of reflected optical energy by wavelength-selective photodetectors to form a spectral reflection profile
Data Source
AI summary
An optical sensing system including an optical interrogator is operative with an array of reflective sensors, each sensor providing a separable reflected spectral response parameter such as a unique Gaussian standard deviation or reflected response compared to other sensors in the same operating wavelength range. The optical interrogator provides narrowband swept or broadband continuous optical power source to the array of FBG sensors, and an optical interrogator generates a g(x) representation of power vs wavelength of the reflected optical power and decomposes the representation into the wavelength of the individual sensors, thereby allowing operation of two or more FBG sensors in the same operating wavelength range.