Optical Fiber Refractive Index Structure for Low Bend Attenuation
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Solution Overview
Problem
Conventional optical fiber manufacturing processes using the OVD method result in a refractive index profile with a center line dip, leading to degraded bend performance and bend-induced attenuation, particularly in G657 category fibers, without effective solutions to control or reduce this issue.
Innovation Solution
The optical fiber design features a core region with a first core having a higher refractive index peak than a second core, surrounded by claddings with varying dopants and radial dimensions, including up-doped and down-doped silica, to enhance bend performance and reduce attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the OVD process is used to manufacture optical fiber, then the deposition rate is high and large fiber base material can be made, but the refractive index profile has a center line dip which degrades bend performance
Solution Approach 1:
The patent applies local quality by creating distinct regions within the fiber structure with different refractive index characteristics. Specifically, it introduces a first core region with higher refractive index and a second core region with lower refractive index, along with a cladding region. This localized differentiation of optical properties allows the fiber to maintain the benefits of OVD processing while compensating for the center line dip through the higher index first core region, thereby improving bend performance without sacrificing productivity.
2Ease of manufacture
If the center line dip is present in the refractive index profile, then the OVD process is simplified, but bend induced attenuation increases
Solution Approach 1:
The patent converts the harmful effect of the center line dip into a beneficial structure by intentionally creating a two-core configuration where the first core region with higher refractive index is positioned to counteract the dip. The dip region itself becomes part of the second core region with lower refractive index. This transformation maintains the simplicity of the OVD manufacturing process while the engineered refractive index distribution compensates for the dip's negative effects, reducing bend-induced attenuation.
3Device complexity
If a single core structure is used, then the fiber structure is simple, but bend performance is degraded
Solution Approach 1:
The patent applies segmentation by dividing the core into two distinct regions: a first core region with higher refractive index and a second core region with lower refractive index. This segmentation allows each region to serve different functions - the first core region provides strong light confinement and bend resistance, while the second core region maintains compatibility with standard splicing processes. The segmented structure improves bend performance without excessive complexity, as both regions can be formed using modified OVD techniques.
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 improved refractive index profile achieves reduced macro-bend losses and enhanced bend insensitivity, maintaining optimal signal confinement and minimizing attenuation during bending.
Implementation Method 1
An optical fiber (i.e., a glass fiber typically surrounded by one or more coating layers) conventionally includes an optical fiber core, which transmits and/or amplifies an optical signal, and an optical cladding, which confines the optical signal within the core. Accordingly, the refractive index of the core nc is typically greater than the refractive index of the optical cladding ng (i.e., nc>ng).
Implementation Method 2
Commonly used methods for fabricating optical fiber base materials include Modified Chemical Deposition (MCVD), OVD, Vapor Phase Axis Deposition (VAD), and Plasma Chemical Vapor Deposition (PCVD). Among them, the OVD method is one of the widely used methods because it has a high deposition rate and an advantage of making a fiber base material large. In the OVD process, a soot preform is deposited on a mandrel
Data Source
AI summary
The present invention relates to an optical fiber with improved bend performance and manufacturing method thereof. The optical fiber (100) comprises a core region (108) defined by a core refractive index profile (200) and a cladding region (106) surrounding the core region defined by a cladding refractive index profile (400). Particularly, the core region has a first core (102) defined by a first core refractive index (RI) profile (202) and a first core RI max (Δpeak) and a second core (104) defined by a second core RI profile (204) and a second core RI max (Δcore). Moreover, the cladding region further comprises a first cladding (106) and a third cladding (110) composed of pure silica and a second cladding (108) composed of a down-doped silica, where the down-dopant is fluorine.