Bend Insensitive Gradient Index Multimode Fiber
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Bend insensitive multimode light conducting fibers with refraction index trenches suffer from leakage mode conduction, which increases the length dependency of the optical core diameter and numerical aperture, leading to degraded coupling properties and misinterpretations in measurement parameters, especially under overfilled launch excitation conditions.
Innovation Solution
A bend insensitive GIMM light conducting fiber with a core, inner cladding, and outer cladding, featuring a refraction index trench and alpha refraction index profile, is designed to minimize leakage mode propagation by optimizing the dimensions of the core, trench, and cladding, reducing the length dependency of the optical core diameter and numerical aperture, while maintaining low macro-bend sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a refraction index trench is inserted to reduce macro-bend losses, then bend insensitivity is improved, but leakage mode conduction increases causing degraded coupling properties
Solution Approach 1:
The patent applies local quality by creating an inner cladding region with specific refraction index characteristics between the core and outer cladding. This inner cladding has a refraction index that is lower than the core but higher than or equal to the outer cladding, creating a localized refraction index distribution that confines leakage modes while maintaining bend insensitivity. The refraction index profile is specifically designed as dn(r) = dn1 * (r/R1)^2 for r < R1 and dn(r) = dn2 for r >= R1, where this localized variation in refraction index quality solves the contradiction between bend insensitivity and leakage mode suppression.
2Length of moving object
If the fiber length increases, then transmission distance is improved, but optical core diameter and numerical aperture decrease due to leakage mode attenuation
Solution Approach 1:
The patent applies parameter changes by carefully controlling the refraction index parameters dn1 and dn2, and their relationship. The key parameter relationship dn2 >= dn1 * (R2/R1)^2 is established to ensure that leakage modes are properly confined. By changing and optimizing these refraction index parameters within specific ranges, the patent maintains stable optical core diameter and numerical aperture over long fiber lengths, enabling transmission distances up to several kilometers while preserving coupling properties.
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
The fiber configuration achieves a reduction in optical core diameter and numerical aperture changes by less than 5% and 2.5% respectively over 2m to 300m lengths, and a bend-related attenuation increase of less than 0.2dB for two turns with a 7.5mm bend radius, enhancing the stability and accuracy of light conduction properties.
Implementation Method 1
a core, an inner cladding, and an outer cladding, featuring a refraction index trench and alpha refraction index profile
Implementation Method 2
the refraction index difference of the core relative to a surrounding cladding essentially a power function of the radius
Data Source
AI summary
The invention relates to a bend insensitive gradient index multimode light conducting fiber comprising a leakage mode dependent optical core diameter that is uniform over its length and numerical aperture that is uniform over its length, a core (1), an inner cladding (2), a refraction index trench (3) and an outer cladding (4), wherein the core (1) includes a core radius R1, an alpha-refraction index profile and a core refraction index difference dn1 with respect to the outer cladding (4), wherein the refraction index trench (3) includes a refraction index trench radius R3 and a trench refraction index difference dn3 with respect to the outer cladding (4), wherein the outer cladding (4) includes an outer cladding radius R4 and a refraction index between 1.40 and 1.55, wherein for a light wavelength of 850 nm and an overfilled launch (OFL), the optical core diameter for a fiber length in a range between 2 m and 300 m decreases by less than 5% and the numerical aperture decreases by less than 2.5% and the curvature related attenuation increase for two turns and a curvature radius of 7.5 mm is less than 0.2 db.