Small-Diameter Single-Mode Optical Fiber With Double Transitional Cladding
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Solution Overview
Problem
The demand for smaller diameter single-mode optical fibers with excellent geometric and optical performance is increasing due to the need for higher bandwidth and space-efficient communication systems, while maintaining compatibility with conventional communication optical fibers.
Innovation Solution
A small-diameter single-mode optical fiber design featuring a germanium-doped core layer and a double transitional cladding layer structure with parabolic and polynomial line shape descents, which reduces stress and microcracks, and enhances compatibility with existing fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the diameter of the optical fiber is reduced to meet space utilization demands, then space efficiency is improved, but the optical fiber becomes more susceptible to external interference and loses geometric and optical performance
Solution Approach 1:
The patent applies parameter changes by precisely controlling the refractive index distribution profile through polynomial line shape descent functions. The relative refractive index difference is designed to decrease along the radial direction according to specific polynomial equations, which optimizes the balance between small diameter and maintained optical performance. This mathematical parameter optimization allows the fiber to maintain single-mode operation and low attenuation even at reduced diameters.
Solution Approach 2:
The patent employs composite materials by creating a multi-layer cladding structure with different refractive indices. The cladding layer comprises an inner region and an outer region with distinct refractive index characteristics, forming a composite structure that provides both mechanical strength and optical performance. This composite approach allows the fiber to maintain geometric stability and optical properties despite the reduced overall diameter.
2Area of stationary object
If the coating layer is thinned to reduce fiber diameter, then space utilization is improved, but the optical fiber becomes more susceptible to external interference
Solution Approach 1:
The patent uses parameter changes by optimizing the refractive index distribution profile in the cladding layer. The polynomial line shape descent function carefully controls the relative refractive index difference to decrease radially, which maintains the waveguide properties and protects against external interference. This mathematical optimization allows thinner coating while maintaining performance.
Solution Approach 2:
The patent introduces an intermediary approach by creating a transition region between the core and cladding with specific refractive index characteristics. The polynomial line shape descent acts as an intermediary function that smoothly transitions the refractive index, reducing stress concentrations and protecting the core from external interference while maintaining the compact diameter.
3Ease of operation
If existing cutting and welding equipment is used to maintain compatibility with conventional fibers, then ease of operation is improved, but the optical fiber size must meet equipment requirements while achieving performance improvement
Solution Approach 1:
The patent applies parameter changes by optimizing the outer cladding layer diameter to fall within the range acceptable to existing equipment while maintaining smaller core dimensions. The refractive index distribution is carefully controlled through polynomial functions to ensure that the overall fiber size remains compatible with conventional cutting and welding equipment, while the core size and optical properties achieve the desired improvement.
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 design achieves improved long-term reliability, reduced attenuation, and compatibility with conventional single-mode optical fibers, while maintaining low butt splice losses and bending insensitivity.
Implementation Method 1
achieves a smooth transition between the germanium-doped core layer and the outer quartz cladding layer through two waveguide structures: parabolic descent and polynomial line shape descent, which reduces the stress between the core and cladding, thereby minimizing the microcracks inside the optical fiber caused by stress
Implementation Method 2
a refractive index of the first transitional cladding layer is less than that of the germanium-doped core layer, and is greater than that of the second transitional cladding layer; and from inside to outside along the radial direction, a relative refractive index difference of the first transitional cladding layer is decreased in a first polynomial line shape, and the relative refractive index difference of the second transitional cladding layer is decreased in a second polynomial line shape
Data Source
Figure 1~2
Figure 3
AI summary
A small-diameter single-mode optical fiber, comprising a germanium-doped core layer (1), a first transitional cladding layer (2), a second transitional cladding layer (3) and an outer quartz cladding layer (8), which are sequentially arranged from inside to outside in the radial direction, wherein the refractive index of the first transitional cladding layer (2) is less than that of the germanium-doped core layer (1), and is greater than that of the second transitional cladding layer (3); and the relative refractive index difference of the first transitional cladding layer (2) linearly decreases from inside to outside in the radial direction in a first polynomial form, and the relative refractive index difference of the second transitional cladding layer (3) linearly decreases from inside to outside in the radial direction in a second polynomial form. The first transitional cladding layer (2), the relative refractive index difference of which linearly decreases in the first polynomial form, and the second transitional cladding layer (3), the relative refractive index difference of which linearly decreases in the second polynomial form, are designed around the germanium-doped core layer (1), such that a waveguide structure having two smoothly transitional cladding layers is formed, and the capability of the small-diameter optical fiber resisting external disturbance is enhanced; and smooth transition between the germanium-doped core layer (1) and the outer quartz cladding layer (8) is realized, such that stress between core packages is reduced, and micro cracks in the optical fiber caused by the stress are reduced, thereby improving the long-term reliability of the optical fiber.