Suspended Hollow-Core Fiber Termination for Low-Reflection Protection
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Solution Overview
Problem
Hollow-core optical fibers with structured cladding face issues in termination due to mechanical fragility and contamination, which can degrade light-guiding properties and cause structural damage, and conventional fusing methods lead to Fresnel reflection losses and deformation of the cladding.
Innovation Solution
A nested-capillary configuration suspends the fiber-end of the hollow-core optical fiber inside an outer capillary with an inner capillary acting as a radial spacer, maintaining a non-zero distance from an endcap, allowing for precise positioning and antireflective coatings without direct contact, thus protecting the fiber-end and reducing reflection losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the fiber-end is directly contacted with the endcap for termination, then mechanical protection is provided, but the fragile fiber-end is susceptible to mechanical damage and contamination
Solution Approach 1:
The termination structure is segmented into multiple components: an outer capillary providing mechanical protection, an inner capillary acting as a radial spacer, and an endcap for light transmission. This segmentation allows the fiber-end to be protected without direct contact, preventing mechanical damage and contamination while maintaining structural integrity.
Solution Approach 2:
The inner capillary acts as an intermediary element between the fiber-end and the outer capillary/endcap assembly. It provides radial spacing that prevents direct contact, thereby mediating the mechanical protection function while avoiding the harmful effect of direct contact on the fragile fiber-end.
2Ease of manufacture
If conventional fusing methods are used to terminate the fiber, then connection is achieved, but Fresnel reflection losses occur and cladding deformation happens
Solution Approach 1:
The invention extracts the harmful thermal fusing process from the termination method. Instead of fusing the endcap directly to the fiber, the endcap is positioned adjacent to the outer capillary without direct thermal contact, eliminating Fresnel reflection losses and cladding deformation while maintaining mechanical connection.
Solution Approach 2:
The thermal fusing process is replaced with a mechanical positioning system using capillaries and spacers. The inner capillary provides precise radial spacing, and the outer capillary provides longitudinal positioning, replacing the thermal field with a mechanical field to achieve connection without damage.
3Loss of energy
If the fiber-end is suspended at a non-zero distance from the endcap, then antireflective coatings can be applied and reflection losses minimized, but precise positioning is required
Solution Approach 1:
The inner capillary serves as a self-positioning radial spacer that automatically maintains the required non-zero distance between the fiber-end and endcap. This self-service mechanism ensures precise positioning without requiring complex external alignment tools or procedures during manufacturing.
Solution Approach 2:
The nested capillary structure (inner capillary within outer capillary) provides multi-level positioning control. The inner capillary controls radial spacing while the outer capillary controls longitudinal positioning, creating a self-aligning nested system that achieves precise positioning through geometric constraints rather than active control.
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 protects the fragile fiber-end from mechanical damage, prevents contamination, and minimizes Fresnel reflection losses by allowing for antireflective coatings, enhancing the performance and ease-of-use of hollow-core fibers.
Implementation Method 1
Total internal reflection at the interface between the core and the cladding material causes light to be guided in the core
Implementation Method 2
conventional fusing methods lead to Fresnel reflection losses
Data Source
AI summary
A terminated hollow-core optical fiber includes an outer capillary having an end-face, a hollow-core optical fiber having a fiber-end located inside the outer capillary a non-zero distance away from the end-face of the outer capillary, a fiber jacket disposed on a surface of the hollow-core optical fiber, and an inner capillary disposed between the fiber jacket and an inner surface of the outer capillary. The inner capillary holds the hollow-core optical fiber via the fiber jacket such that the fiber-end protrudes from the inner capillary and is suspended inside the outer capillary. The terminated hollow-core optical fiber further includes an endcap adjacent the end-face of the outer capillary. This configuration positions the sensitive and potentially fragile fiber-end close to the endcap in a protected environment, while avoiding direct contact between the fiber-end and other mechanical structures, and can be realized without fusing anything to the light-transmitting surfaces of the endcap.