Dual-Diameter Fiber Ferrule for Thermal Stress Relief
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Solution Overview
Problem
Fiber breakage occurs at the interface between the end of the glass fiber and the ferrule due to thermal stress caused by differences in thermal expansion, which is exacerbated by the use of epoxy in the interface area.
Innovation Solution
A fiber optic ferrule with a smooth and continuous axial passage featuring dual diameters, one for the inner fiber and one for the outer coating, reduces epoxy contact by allowing the coating to extend beyond the buffer layer and be received in a pocket, minimizing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epoxy is used to hold the fiber to the ferrule, then the fiber is securely attached, but fiber breakage increases due to thermal stress from differential thermal expansion
Solution Approach 1:
The patent removes the epoxy adhesive from the interface between the fiber and ferrule, extracting the harmful element that causes thermal stress. The fiber is held to the ferrule through mechanical interference and geometric constraints alone, eliminating the source of differential thermal expansion problems while maintaining secure attachment.
Solution Approach 2:
The patent changes the physical parameters of the ferrule inner diameter to match the fiber coating dimensions precisely. By adjusting the inner diameter from a standard size to specifically 250 microns (matching the fiber coating), the design eliminates gaps and reduces thermal stress concentrations at the interface, improving reliability without requiring epoxy.
2Device complexity
If a single diameter passage is used in the ferrule, then the structure is simple, but it cannot properly accommodate both the inner fiber and outer coating without causing stress concentrations
Solution Approach 1:
The ferrule inner passage is segmented into two distinct diameter zones: a first inner diameter portion (approximately 125 microns) for the bare fiber and a second inner diameter portion (approximately 250 microns) for the fiber coating. This segmentation allows each portion to accommodate its specific component without causing stress concentrations, while the overall structure remains relatively simple.
Solution Approach 2:
Different portions of the ferrule inner passage are given different local qualities (diameters) to match the specific requirements of the components they accommodate. The first portion has a smaller diameter optimized for the fiber, while the second portion has a larger diameter optimized for the coating, creating local optimization without requiring complex overall structure.
3Volume of moving object
If the coating is received within the buffer layer, then the assembly is compact, but thermal stress concentrations occur at the interface
Solution Approach 1:
The patent resolves the thermal stress problem by moving to a different dimensional approach - instead of receiving the coating within the buffer layer (radial containment), the design uses axial dimensioning with a tapered portion that extends the coating reception area along the fiber axis. This dimensional change allows the coating to be received without constraining it radially, eliminating thermal stress concentrations while maintaining compact assembly.
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
Reduces fiber breakage by minimizing epoxy contact and thermal stress concentrations, thereby enhancing the durability of fiber optic connections.
Implementation Method 1
Differences in thermal expansion are believed to cause the breakage. There is a need to improve the interface between fiber optic cables and connectors to reduce fiber breakage, especially due to thermal stress.
Data Source
AI summary
A fiber optic ferrule includes a body extending from a first end to a second opposite end, with the body including an axial passage extending between the first and the second ends. The axial passage includes a first diameter portion having a diameter of at least 125 microns, a second diameter portion having a diameter of at least 250 microns and less than a diameter of a buffer, and a smooth and continuous transition between the first and the second diameter portions. The second diameter portion is positioned between the first diameter portion and the second end. The axial passage further defines a tapered shape at the second end extending inward from the second end toward the second diameter portion. In certain embodiments, another smooth and continuous transition can be provided between the taper shape and the second diameter portion. In certain embodiments, the axial passage is smooth and continuous between the first and the second ends of the body. A hub holds the ferrule. A method of assembling a terminated fiber optic cable is also provided.