Small Diameter Optical Fiber Grating Formation
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Solution Overview
Problem
Conventional single-mode optical fibers have low Rayleigh scattering intensity, limiting the resolution and sensitivity of distributed optical fiber sensors, and existing methods for increasing scattering either fail to significantly enhance backscattering or introduce fiber attenuation and reliability issues.
Innovation Solution
The development of small diameter single-mode optical fibers with gratings, where a high-modulus or low-modulus coating layer is applied, allowing for the formation of optical gratings within the core through ultraviolet radiation exposure without the need to remove and reapply the coating, thereby enhancing Rayleigh backscattering while minimizing fiber attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the numerical aperture (NA) of the fiber is raised to increase capture efficiency for backscattered light, then Rayleigh backscattering is improved, but the improvement is limited to less than 2 dB within practical single mode fiber design space
Solution Approach 1:
The patent changes the physical state of the fiber core by introducing periodic refractive index variations through UV exposure, creating Bragg gratings that enhance backscattering through constructive interference rather than relying solely on increasing NA
Solution Approach 2:
UV radiation acts as an intermediary to modify the fiber core properties, creating a permanent grating structure that enhances backscattering without requiring changes to the fiber's numerical aperture or other structural parameters
2Illumination intensity
If scattering particles are added to increase scattering, then Rayleigh backscattering is improved, but fiber attenuation increases
Solution Approach 1:
The patent replaces the mechanical approach of adding physical scattering particles with an optical field-based solution using UV-induced refractive index modulation, creating gratings that enhance backscattering through wave interference rather than particle scattering
Solution Approach 2:
The patent modifies the refractive index parameter of the fiber core in a controlled, periodic manner to create Bragg gratings, achieving enhanced backscattering without introducing the attenuation effects associated with adding scattering particles
3Length of stationary object
If UV exposure is performed during fiber draw to fabricate gratings, then gratings can be formed over long lengths, but aligning the laser system with the fiber is difficult due to fiber vibration
Solution Approach 1:
The patent performs the grating fabrication after the fiber draw and coating application are complete, eliminating the alignment difficulties associated with working with vibrating fibers during the draw process
Solution Approach 2:
The patent uses the already-applied coating as a protective intermediary layer that allows UV exposure to proceed without requiring removal or disruption of the coating, simplifying the fabrication process
4Ease of manufacture
If coating is removed and reattached after grating fabrication, then gratings can be formed, but the coating applied during fiber draw is wasted and coating removal may introduce defects on glass surface
Solution Approach 1:
The patent uses the coating as a protective intermediary layer that enables UV exposure to proceed without compromising the glass surface, eliminating the need for coating removal and preventing surface defects
Solution Approach 2:
The coating serves dual purposes: protecting the fiber during handling and enabling the grating fabrication process, eliminating the need for separate coating removal and reapplication steps
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 significantly increases Rayleigh backscattering, improving the resolution and sensitivity of distributed optical fiber sensors without compromising fiber reliability or increasing attenuation, enabling more effective detection of changes in temperature, strain, and other parameters.
Implementation Method 1
exposing the core, through the coating, to a pattern of ultraviolet radiation to form an optical grating within the core
Implementation Method 2
Rayleigh-based distributed optical fiber sensors (DOFSs) are useful for detecting changes in temperature, strain, pressure, relative humidity, chemical concentration, radiation, etc.
Data Source
AI summary
Embodiments of the current disclosure include small diameter single-mode optical fibers having gratings and methods of forming thereof. In some embodiments, methods of forming a small diameter single-mode optical fibers having gratings include providing an optical fiber having a core and cladding with a combined outer diameter of 100 μm to 125 μm and a coating having a thickness of less than or equal to 20 μm, wherein the coating comprises one of: (i) a high-modulus coating layer surrounding the cladding region; or (ii) a low-modulus coating layer surrounding the cladding region and a high-modulus coating layer surrounding the low-modulus coating layer; and exposing the core, through the coating, to a pattern of ultraviolet radiation to form an optical grating within the core.