Capillary Tube Cladding Filter for Evanescent Light Suppression
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Solution Overview
Problem
Existing optical fiber cladding optical filters face challenges in suppressing unwanted evanescent laser light that escapes from the cladding, often causing damage to the fiber core during acid etching processes.
Innovation Solution
The use of an elongated capillary tube with a grating pattern formed on its outer surface, closely matching the optical fiber's diameter, which surrounds the fiber and suppresses light exiting transverse to its longitudinal axis, combined with an adhesive matching the fiber's refractive index, effectively mitigates evanescent light leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acid etching is used to modify the cladding surface, then light suppression effectiveness is improved, but the fiber core surface may be damaged
Solution Approach 1:
The patent introduces an intermediary substance (adhesive or coating material) between the cladding and the surrounding environment. This intermediary has a refractive index matched to the core material, creating a protective barrier that suppresses evanescent light without requiring direct acid contact with the core, thus resolving the contradiction between light suppression effectiveness and core surface protection
Solution Approach 2:
The patent replaces the chemical etching process with a physical/optical solution using materials of specific refractive indices. Instead of using acid to modify the cladding surface, the invention uses carefully selected adhesive or coating materials whose optical properties achieve the same light suppression function without the harmful chemical effects
2Reliability
If high refractive index adhesives are used between cladding and heat sink, then light suppression is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies homogeneity by using a single adhesive material throughout the entire assembly rather than multiple materials with different refractive indices. The adhesive's refractive index is specifically matched to the core material, creating a uniform optical interface that simplifies manufacturing while maintaining effective light suppression
Solution Approach 2:
The adhesive serves multiple functions simultaneously: it provides mechanical bonding between the cladding and heat sink, and it provides optical functionality by suppressing evanescent light through refractive index matching. This multi-functionality reduces manufacturing complexity by eliminating the need for separate optical and mechanical components
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 solution prevents unwanted evanescent laser light from escaping, reducing the risk of damage to the fiber core and improving the effectiveness of optical fiber cladding optical filters by utilizing a non-destructive method to manage light exiting the cladding.
Implementation Method 1
A grating or grating pattern is formed on the outer surface of the elongated capillary tube... the grating suppresses light exiting the optical fiber transverse to a longitudinal axis of the optical fiber
Implementation Method 2
An adhesive may be disposed between the inner surface of the capillary tube and an exterior surface of the optical fiber... the refractive indices of the adhesive and the fiber core of the optical fiber may match or be the same
Data Source
AI summary
An optical fiber cladding optical filter includes an elongated capillary tube including an inner surface positioned surrounding an elongated optical fiber proximate or adjacent an exterior surface of the optical fiber and an outer surface positioned spaced from the exterior surface of the optical fiber. A grating formed on the outer surface of the elongated capillary tube aids in suppressing evanescent laser light that exits the optical fiber transverse to a longitudinal axis of the optical fiber. The elongated optical fiber and surrounding elongated capillary tube can include one or more curves along a length thereof to aid in the removal of one or more higher order laser modes as evanescent laser light that exits the optical fiber. The one or more curves can be received in a container to prevent or avoid evanescent laser exiting the optical fiber from propagating into an ambient environment.