Optical Fiber Trench Coating for Bending Loss Reduction
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Solution Overview
Problem
Conventional optical fibers with trench structures face challenges in reducing bending loss while maintaining low material costs and efficient manufacturing, particularly due to the need for high refractive index differences and complex manufacturing techniques, which increase costs and connection losses.
Innovation Solution
An optical fiber design featuring a core, internal cladding, a trench coating with multiple layers of different refractive indices, and an outermost cladding, where the highest refractive index layer is at the outermost position in the trench coating, and the lowest refractive index layer is at the innermost position, optimizing refractive index differences and layer configurations to reduce bending loss and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a trench structure is used to reduce bending loss, then bending loss is reduced, but manufacturing cost increases due to complex manufacturing techniques and high refractive index differences
Solution Approach 1:
The patent applies parameter changes by optimizing the refractive index differences and layer thicknesses in the trench coating. Specifically, it uses a first trench coating with refractive index difference Δt1 and a second trench coating with refractive index difference Δt2, where both are controlled within specific ranges (0.003<Δt1≤0.006 and 0.003<Δt2≤0.006). This parameter optimization achieves effective bending loss reduction while avoiding the need for extreme refractive index differences that would increase manufacturing complexity and cost.
Solution Approach 2:
The patent segments the trench coating into multiple layers with different refractive index characteristics. It employs a first trench coating layer and a second trench coating layer, each with specific refractive index differences relative to the cladding. This segmentation allows each layer to contribute differently to the overall bending loss reduction, achieving effective performance while using moderate refractive index differences that are easier and less costly to manufacture.
2Loss of energy
If the MFD is reduced to decrease bending loss, then bending loss is reduced, but connection loss increases and MFD deviates from ITU-T G.652 recommendations
Solution Approach 1:
The patent segments the bending loss reduction function between the core-cladding structure and the multi-layer trench coating. The core maintains a standard MFD (8.6-9.5 μm at 1310 nm) for reliable connections, while the trench coating layers provide the bending loss reduction. This segmentation allows independent optimization of connection performance and bending resistance.
Solution Approach 2:
The trench coating acts as an intermediary structure between the core and the outer cladding. It provides the bending loss reduction function without requiring changes to the core MFD, thereby maintaining compatibility with standard connection requirements while achieving enhanced bending performance.
3Ease of manufacture
If a single-layer trench coating is used, then manufacturing is simpler, but bending loss reduction is insufficient compared to multi-layer structures
Solution Approach 1:
The patent optimizes the parameters of each trench coating layer to achieve effective bending loss reduction. By controlling the refractive index differences (Δt1 and Δt2) within specific ranges and setting appropriate thickness ratios (0.45≤(rtmax−rin)/(rout−rin)≤0.9), the multi-layer structure achieves superior bending loss reduction compared to single-layer designs, while maintaining manufacturability through controlled parameter ranges.
Solution Approach 2:
The patent employs a composite trench coating structure with two different layers, each having distinct refractive index characteristics. This composite structure leverages the complementary properties of the two layers to achieve enhanced bending loss reduction that would be difficult to attain with a single-layer design, while the controlled parameter ranges ensure the composite structure remains manufacturable.
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 low-bending loss comparable to conventional trench structures at a lower cost by optimizing refractive index profiles and layer configurations, reducing the amount of dopants needed and enhancing manufacturing efficiency, while effectively attenuating higher order modes.
Implementation Method 1
an optical fiber including: a core (11) provided at a central portion; an internal cladding coat (12) provided around the core (11), having a refractive index less than a refractive index of the core (11); a trench coating (13) provided at a periphery of the internal cladding coat (12) and constituted of two or more layers (15, 16) having refractive indexes different from each other
Data Source
AI summary
An optical fiber of the invention satisfies Δcore>Δic>Δtmax>Δtmin, −0.15%≧Δtmax>Δtmin≧−0.7%, and 0.45≦(rtmax−rin)/(rout−rin)≦0.9 where the relative refractive index difference of the core is Δcore, the relative refractive index difference of the internal cladding coat is Δic, the relative refractive index difference of a highest refractive index layer in the trench coating is Δtmax, the relative refractive index difference of a lowest refractive index layer in the trench coating is Δtmin, the radius of an internal edge of the trench coating is rin, the radius of an external edge of the trench coating is rout, and the radius of an internal edge of a highest refractive index layer in the trench coating is rtmax and where the relative refractive index differences are based on a refractive index of the outermost cladding coat.