Optical Fiber Bundle Core Ratio Control to Prevent Crosstalk
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Solution Overview
Problem
The optical fiber bundle structure disclosed in Japanese Patent No. 5738275 experiences crosstalk due to reduced core distances when a taper rate of 3 to 10 is achieved, making it unsuitable for connecting single-mode or few-mode fibers to a multi-core fiber.
Innovation Solution
An optical fiber bundle structure is designed with a glass fiber portion and resin coated portion, where the diameter ratio (d2/d1) of the core at the distal end to the core at the rear end of the capillary is set between 0.57 and 1, and the fibers are connected through a capillary using a specific manufacturing method involving melting and drawing to prevent crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a taper rate of 3 to 10 is achieved by melting and drawing the capillary and glass fiber portion, then the connection between single-mode fibers and multi-core fiber is established, but the distances between cores are reduced causing crosstalk
Solution Approach 1:
The patent changes the diameter ratio parameter d2/d1 from the conventional range (which would produce taper rates of 3-10) to a specific range of 0.95 to 1.05. This parameter modification maintains the connection stability between single-mode fibers and multi-core fiber while preventing core distance reduction that causes crosstalk. The capillary and glass fiber portion are melted and drawn with this controlled diameter ratio to achieve the desired effect.
2Reliability
If the core diameter is reduced at the distal end to improve coupling, then the coupling efficiency improves, but crosstalk increases due to reduced core distances
Solution Approach 1:
The patent modifies the core diameter ratio parameter d2/d1 to fall within 0.95 to 1.05, which maintains nearly constant core distances throughout the fiber bundle. This prevents the harmful reduction in core spacing that would cause crosstalk, while still achieving effective coupling between single-mode fibers and multi-core fiber through the controlled melting and drawing process of the capillary structure.
3Manufacturing precision
If a high taper rate is used to maintain core alignment, then the alignment accuracy improves, but the core distances are reduced causing waveguide mode leakage
Solution Approach 1:
The patent changes the diameter ratio parameter d2/d1 to a range of 0.95 to 1.05, which maintains stable core distances throughout the fiber bundle structure. This prevents waveguide mode leakage caused by excessive core distance reduction, while the melting and drawing process of the capillary and glass fiber portion ensures accurate core alignment is maintained during manufacturing.
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 solution effectively prevents crosstalk and maintains stable connections between single-mode optical fibers and a multi-core fiber, ensuring high light resistance and reducing waveguide mode leakage.
Implementation Method 1
melting and drawing the capillary and the glass fiber portion inserted in the capillary such that d2/d1 is equal to or larger than 0.57 and smaller than 1
Implementation Method 2
melting and drawing the capillary and the glass fiber portion inserted in the capillary
Data Source
AI summary
An optical fiber bundle structure includes: a plurality of optical fiber core wires; and a capillary, wherein each of the optical fiber core wires includes a glass fiber portion including a core and a clad, and a resin coated portion, the glass fiber portions are inserted in the capillary, and d2/d1 is equal to or larger than 0.57 and smaller than 1, where d1 is a diameter of the core of each of the glass fiber portions in a rear end portion of the capillary and d2 is a diameter of the core of each of the glass fiber portions in a distal end portion of the capillary.