Reflective Long Period Grating Sensor with Metal Coating
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Solution Overview
Problem
Traditional reflective long period grating (LPG) sensors face limitations in measuring environmental parameters from long distances and in small spaces due to interference from bending of optical fibers, and existing coating methods are expensive, time-consuming, and challenging to apply to long lengths of delicate sensors.
Innovation Solution
A reflection mode sensor system with multiple LPGs along the optical fiber core, each with a different grating period, and a metal coating applied to the end facet and side surface of the optical fiber cladding, allowing for simultaneous measurement of temperature, strain, and refractive index using reflected light, and enabling longer metal coating lengths without complex processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If thermal evaporation/sputtering technique or electroless and electroplating process are used to create reflective LPG, then the reflection power is improved, but the manufacturing cost increases and the process time is extended
Solution Approach 1:
The patent uses a simple metal coating applied to the end facet of the optical fiber instead of complex thermal evaporation or electroplating processes. This simpler, more economical approach achieves sufficient reflectivity without requiring expensive equipment or time-consuming procedures, directly resolving the contradiction between reflection power and manufacturing efficiency
2Loss of energy
If thermal evaporation/sputtering technique or electroless and electroplating process are used to create reflective LPG, then the reflection power is improved, but the manufacturing cost increases
Solution Approach 1:
The patent employs a simple metal coating method that is significantly cheaper than thermal evaporation or electroplating techniques. This approach uses readily available materials and processes, eliminating the need for expensive specialized equipment while achieving adequate reflective performance for sensor applications
3Device complexity
If a single LPG is used in the optical fiber, then the device complexity is reduced, but the measurement capability for multiple parameters simultaneously is limited
Solution Approach 1:
The patent divides the optical fiber into multiple segments, each containing an LPG with a distinct grating period. This segmentation allows each LPG to respond to different environmental parameters or provide redundant measurement capabilities, enabling simultaneous multi-parameter sensing while maintaining manageable system complexity through modular design
Solution Approach 2:
The patent creates a multi-functional sensor system where multiple LPGs with different grating periods can simultaneously measure different parameters (temperature, strain, refractive index) or provide enhanced measurement capabilities for the same parameters. This universal design allows a single optical fiber assembly to perform multiple sensing functions
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
Enables stable and simultaneous measurement of multiple parameters by reducing interferometric fringe interference and extending the length of metal coating, improving measurement accuracy and reducing costs compared to traditional methods.
Implementation Method 1
a metal coating applied to an end facet of the combined optical fiber core and optical fiber cladding, wherein the metal coating covers a side surface of the optical fiber cladding along a length from the end facet
Implementation Method 2
LPG sensors work by coupling light from fundamental core mode to the cladding modes
Data Source
AI summary
A reflection mode sensor system may include an optical fiber core and an optical fiber cladding. A first long period grating (LPG) may be positioned along the optical fiber core having a first grating period, a second LPG may be positioned along the optical fiber core having a second grating period, and a third LPG may be positioned along the optical fiber core having a third grating period. The grating periods may enable sensing of multiple parameters simultaneously. A metal coating may be applied to an end facet of the combined optical fiber core and optical fiber cladding. The metal coating may also cover a side surface of the optical fiber cladding along a length from the end facet. The metal coating may include a paste applied to the optical fiber core and the optical fiber cladding, where the paste has been cured, and includes a metal.