Optical Sensing Fiber With Integrated Reflective Structures
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Solution Overview
Problem
Current methods for producing gratings in optical telecommunication fibers are limited by costly equipment, high manufacturing costs, and degradation of fiber strength due to coating removal, and are not suitable for multiplexing serial sensors.
Innovation Solution
The method involves using a near ultra-violet or visible laser to create reflective structures within the fiber core or cladding through the existing fiber coating, without damaging it, allowing for the fabrication of Type I FBGs with periodic refractive index variations and reducing laser costs by focusing the beam to achieve high refractive index changes without damaging the coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If excimer laser is used to write FBGs through the fiber coating, then the grating can be written, but the fiber coating must be removed and recoated which degrades fiber strength and increases manufacturing time and cost
Solution Approach 1:
The patent changes the laser wavelength parameter from infrared (excimer laser) to visible range (405nm), which fundamentally alters the interaction with the fiber coating. The visible wavelength laser can write gratings through the coating without requiring coating removal, thereby maintaining fiber strength while achieving the desired grating quality.
Solution Approach 2:
The patent employs a relatively inexpensive visible laser (405nm diode laser) instead of expensive infrared excimer lasers. This cost-effective laser source achieves the grating writing function through the coating without requiring the costly coating removal and recoating process, reducing both equipment investment and manufacturing costs.
2Manufacturing precision
If excimer laser is used to write FBGs, then gratings can be formed, but costly infrared lasers are required which limits accessibility and increases system cost
Solution Approach 1:
The patent changes the laser wavelength from infrared to visible range (405nm), enabling the use of inexpensive diode lasers instead of costly excimer lasers. This parameter change maintains grating formation capability while dramatically reducing equipment cost and improving accessibility.
Solution Approach 2:
The patent replaces expensive infrared excimer lasers with affordable visible wavelength diode lasers. This substitution maintains the essential grating writing function while significantly reducing system cost, making FBG fabrication more accessible and economically viable.
3Productivity
If fiber drawing speed is increased to improve productivity, then more fiber can be produced, but control on grating characteristics and fabrication yield are limited
Solution Approach 1:
The patent applies preliminary action by writing the FBG gratings after the fiber is drawn and coated, rather than during the drawing process. This allows for precise control of grating characteristics using stationary or slowly moving fiber, ensuring high fabrication yield while maintaining high overall productivity through continuous manufacturing.
Solution Approach 2:
The patent segments the manufacturing process into distinct stages: fiber drawing, coating application, and subsequent grating writing. This segmentation allows each process to be optimized independently, enabling high-speed drawing while maintaining precise grating control in the subsequent writing stage.
4Adaptability or versatility
If multiple reflective structures are written in series to enable distributed sensing, then sensing capability is improved, but the reflectance of each structure must be low (10% or less) which complicates the design
Solution Approach 1:
The patent changes the reflectance parameter of each grating to be low (10% or less) to enable effective distributed sensing with multiple serial gratings. This parameter optimization allows light to propagate through multiple gratings while still providing sufficient reflection for sensing, balancing the needs of distributed sensing with practical detection requirements.
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 the creation of optical sensing fibers with serial reflective structures that maintain fiber integrity, allow for distributed sensing, and reduce the cost of laser systems while enabling the multiplexing of many reflective structures in a single fiber.
Implementation Method 1
A source of electromagnetic radiation is provided having a wavelength in the range of 390-600 nm, and a selected wavelength of the electromagnetic radiation is delivered through the coating layer to a selected location within the fiber core or cladding such that the delivered electromagnetic radiation alters the core or cladding to create at least one reflective structure
Implementation Method 2
The at least one reflective structure may include a change in refractive index at the selected location, which may be in the range of 1×10−10 to 0.32
Implementation Method 3
The at least one reflective structure may include a change in refractive index at the selected location... The reflectance of the at least one reflective structure may be 10% or less
Data Source
AI summary
Method for creating an optical sensing fiber having a reflective structure integrally disposed therein, comprising: providing an optical fiber having a core and a cladding layer disposed in optical contact with the core, and having a polymer coating layer disposed in contact with and surrounding the cladding layer, the coating layer at least partially transparent in the wavelengths of 390-600 nm; providing a source of electromagnetic radiation having a wavelength in the range of 390-600 nm; and delivering a selected wavelength of the electromagnetic radiation through the coating layer to a selected location within the fiber core or cladding such that the delivered electromagnetic radiation alters the core or cladding to create at least one reflective structure in the core or cladding at the selected location.