Optical Fiber with Cladding Down-Doped Region for Bend Loss Reduction
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Solution Overview
Problem
Existing optical fibers face challenges in achieving optimum optical parameters and reducing manufacturing costs, particularly in network access applications where high-density cables with low bend losses are required.
Innovation Solution
The optical fiber features a core region with an up-doped structure and a cladding region with a precisely located down-doped region and an undoped region, optimizing the mode field diameter and cable cut-off while minimizing macro bend losses and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a depressed layer is placed between core and cladding to achieve bend insensitivity, then macro bend loss is reduced, but optical parameters such as mode field diameter and cable cut-off cannot achieve optimum values
Solution Approach 1:
The patent applies local quality by creating a down-doped region with specific refractive index characteristics only in the cladding region adjacent to the core, rather than using a depressed layer between core and cladding. This localized modification achieves bend insensitivity while preserving optimal optical parameters in the core region.
Solution Approach 2:
Instead of placing a depressed layer between core and cladding as in conventional designs, the patent inverts the approach by creating a down-doped region within the cladding region itself, adjacent to the core boundary. This inversion allows the core-cladding interface to maintain optimal optical characteristics while still achieving bend insensitivity through the cladding's modified refractive index profile.
2Object-affected harmful factors
If conventional optical fiber design is used for FTTH applications, then bend insensitivity is achieved, but manufacturing cost increases and optical parameters are not optimized for network access applications
Solution Approach 1:
The patent changes the refractive index parameters by creating a down-doped region in the cladding with specific depth and extent, rather than using the deeper trench structures of conventional FTTH fibers. This parameter modification achieves adequate bend insensitivity while reducing manufacturing complexity and cost for network access applications.
Solution Approach 2:
The patent applies partial action by creating a down-doped region that is sufficient to achieve bend insensitivity for network access applications, but not as extensive as conventional FTTH fiber designs. This partial modification reduces manufacturing cost while providing adequate performance for the intended application.
3Object-affected harmful factors
If trench depth is increased to reduce bend loss, then macro bend loss decreases, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies local quality by concentrating the refractive index modification in a specific region of the cladding adjacent to the core, rather than creating deep trenches throughout the fiber structure. This localized approach reduces manufacturing complexity while maintaining bend insensitivity.
Solution Approach 2:
The patent uses partial action by creating a down-doped region with moderate depth in the cladding, sufficient to achieve bend insensitivity for network access applications without the excessive trench depth of conventional designs. This reduces manufacturing complexity and cost.
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
This design achieves low attenuations across various wavelengths, reduced macro bend losses, and compatibility with high-density networks, making it cost-effective and suitable for advanced network access applications.
Implementation Method 1
a radial position of minimum relative refractive index of the optical fiber is within three micrometers (μm) from an interface between the down doped region and the undoped region
Data Source
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Figure 1C
AI summary
The present disclosure relates to an optical fiber (100, 101, 103, 105, 107) having a core region (102) and a cladding region (104). In particular, the cladding region (104) has exactly one down-doped region (210, 310) and an undoped region (212, 312). The down doped region (210, 310) is a continuous region adjacent to core region (102) such that radial position of minimum relative refractive index (214, 314) of the optical fiber (100, 101, 103, 105, 107) is within 3 micrometers (µm) from interface between the down doped region (210, 310) and the undoped region (212, 312). Further, the mode field diameter of the optical fiber (100, 101, 103, 105, 107) is in range of 8.8 µm to 9.6 µm at a wavelength 1310 nanometres (nm), and cable cut-off of the optical fiber (100, 101, 103, 105, 107) is less than or equal to 1260 nm.