Step Index Core Optical Fiber with Depressed Cladding for Low Bend Loss
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Solution Overview
Problem
Current single mode optical fibers face challenges in achieving low attenuation and excellent macrobend loss performance, particularly in designs compatible with G.657 and G652 specifications, especially when bent around small diameters, which affects their ability to efficiently transmit data over long distances with minimal signal loss.
Innovation Solution
The development of a single mode optical fiber with a silica-based core having a step refractive index profile, incorporating Cl, Ge, or both, and specific cladding regions with controlled refractive indices, resulting in a mode field diameter greater than 9 microns, zero dispersion wavelength less than 1300 nm, and significantly reduced bend losses when bent around mandrels of various diameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single mode optical fiber is designed with small core radius to achieve low attenuation, then transmission distance is improved, but macrobend loss increases when bent around small diameters
Solution Approach 1:
The patent applies local quality by creating a depressed index cladding region with specific refractive index characteristics surrounding the core. This localized modification of the cladding region's optical properties enables the fiber to maintain low bend loss while preserving the core's small radius for low attenuation, directly resolving the technical contradiction between these two parameters.
Solution Approach 2:
The patent changes the refractive index parameter of the cladding region by introducing a depressed index layer with refractive index lower than both the core and outer cladding. This parameter modification allows the fiber to achieve both low attenuation and low macrobend loss by altering the optical confinement characteristics without changing the core radius.
2Object-affected harmful factors
If mode field diameter is increased to reduce macrobend loss, then bend performance is improved, but compatibility with standard single mode transmission fibers decreases
Solution Approach 1:
The depressed index cladding region creates a localized optical field distribution that effectively increases the mode field diameter for better bend performance, while the core dimensions remain standardized for compatibility. This local modification achieves the dual goal of improved bend performance and maintained compatibility.
Solution Approach 2:
The depressed index cladding region acts as an intermediary structure between the core and outer cladding, mediating the optical field distribution to achieve an effective mode field diameter larger than the core radius while maintaining standard interface dimensions for compatibility with existing fiber infrastructure.
3Object-affected harmful factors
If a depressed index cladding region is introduced to reduce bend loss, then macrobend performance is improved, but device complexity increases
Solution Approach 1:
The cladding is segmented into two distinct regions: an inner depressed index cladding region and an outer standard cladding region. This segmentation allows the depressed index region to specifically address bend loss while the outer region maintains standard structure, achieving performance improvement with controlled complexity.
Solution Approach 2:
The depressed index cladding region is localized to a specific radial distance from the core, creating a targeted solution for bend loss reduction. This local modification approach improves bend performance while limiting the complexity increase to only the necessary region, rather than redesigning the entire fiber structure.
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 optical fiber achieves very low bend losses and attenuation levels compatible with standard single mode transmission fibers, ensuring efficient data transmission with minimal signal degradation even when subjected to bends, thereby meeting stringent specifications like G.657 and G652.
Implementation Method 1
Low attenuation is an important characteristic of standard single mode optical transmission fibers configured to efficiently transmit data over large distances
Implementation Method 2
a silica based core having a step refractive index profile with an alpha of greater than 10, a relative refractive index Δ1MAX
Data Source
AI summary
A single mode optical fiber, comprising: (i) a silica based core having a step refractive index profile with an alpha of greater than 10, a relative refractive index Δ1MAX, and an outer radius r1, wherein 6.25 microns>r1≥4.75 microns, the core further comprising Cl, Ge, or a combination thereof; (ii) a first cladding region in contact with and surrounding the core, the first cladding region having a relative refractive index Δ2MIN, an inner radius r1, and an outer radius r2, wherein r2<20 microns; and (iii) an outer cladding region surrounding the first cladding region, the outer cladding region having a relative refractive index Δ3. The fiber<1300 nm, a 22m cable cutoff wavelength<1260 nm; and a bend loss<0.005 dB/turn when the optical fiber is bent around a 30 mm mandrel; <0.5 dB/turn when the fiber is bent around a 20 mm mandrel.