Bend Resistant Multimode Optical Fiber With Depressed Index Annular Region
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Solution Overview
Problem
Current multimode optical fibers face challenges in achieving high bandwidth and bend resistance, with existing designs often compromising on either performance due to limitations in refractive index profiles and cladding structures.
Innovation Solution
The development of multimode optical fibers with a graded index glass core and a depressed index annular region, where the depressed index region surrounds the core and is surrounded by an outer cladding, enhancing bend resistance and bandwidth through specific refractive index profiles and dopant compositions, such as fluorine or germanium, to achieve low macrobend attenuation and high overfilled bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional multimode optical fiber design is used, then the fiber can transmit light signals, but the bandwidth is limited and bend performance is poor
Solution Approach 1:
The patent applies local quality by creating a depressed index annular region with specific refractive index characteristics immediately adjacent to the core. This localized modification of the cladding region's refractive index profile (with minimum refractive index delta Δ2MIN and moat volume greater than 120 μm²) provides enhanced bend resistance in that specific region while maintaining high bandwidth through the graded index core structure with maximum relative refractive index delta of about 1%.
2Productivity
If the core refractive index delta is increased to improve bandwidth, then bandwidth increases, but bend losses increase
Solution Approach 1:
The depressed index annular region acts as an intermediary between the graded index core and the outer cladding. It mediates the optical field distribution by providing a refractive index buffer zone that reduces macrobend-induced mode coupling and radiation losses. This intermediary region with its specific moat volume (greater than 120 μm²) and refractive index profile allows the core to maintain high bandwidth while the depressed index region protects against bend losses.
3Ease of manufacture
If the cladding structure is simplified, then manufacturing is easier, but bend performance deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the refractive index profile parameters of the cladding regions. The depressed index annular region is defined by specific parameters: minimum refractive index delta Δ2MIN, inner radius extending from the core boundary, and moat volume greater than 120 μm². The outer cladding region has refractive index delta Δ3 where Δ1MAX > Δ3 > Δ2MIN. These parameter specifications provide enhanced bend resistance while maintaining manufacturability through standard doping techniques (fluorine, boron, or germanium).
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
These fibers exhibit very low bend-induced attenuation while maintaining high overfilled bandwidth, with numerical aperture and spectral attenuation optimized across various wavelengths, demonstrating improved performance in both macrobend resistance and high-frequency transmission capabilities.
Implementation Method 1
a graded index glass core having an optical core radius between 21 and 27 microns and a maximum refractive index delta at 850 nm, Δ1MAX... A depressed index annular region surrounds the multimode core and exhibits minimum refractive index delta at 850 nm, Δ2MIN
Data Source
AI summary
Bend resistant multimode optical fibers are disclosed herein. Multimode optical fibers disclosed herein comprise a core region and a cladding region surrounding and directly adjacent to the core region, the cladding region comprising a depressed-index annular region, wherein the inner boundary of said depressed index region is an extension of the graded index core, the depressed region having a moat volume greater than 105%-um2.