Optical Fiber Multi-Layer Coating Plasticizer Resistance
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Solution Overview
Problem
Optical cables used in high-temperature environments with PVC electric cables suffer from cracking due to the migration of low molecular weight plasticizers into the optical fiber, leading to long-term deterioration.
Innovation Solution
The optical fiber is designed with a coating comprising multiple layers, where the inside coating layer has a smaller swelling rate and higher crosslink density than the outside coating layer, preventing cracking by managing swelling and stress distribution effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-layer coating is used on the optical fiber, then the structure is simple and easy to manufacture, but the coating cracks due to plasticizer migration in high-temperature environments
Solution Approach 1:
The coating is divided into multiple layers (first coating layer and second coating layer) with different swelling rates. The first layer has a smaller swelling rate to resist plasticizer migration, while the second layer has a larger swelling rate to accommodate expansion, preventing cracks that would occur in a single-layer coating.
Solution Approach 2:
Different regions of the coating have different properties: the inner layer near the optical fiber has low swelling rate for resistance to plasticizer, while the outer layer has high swelling rate for stress accommodation. This local differentiation allows the coating to simultaneously resist chemical migration and mechanical cracking.
2Object-affected harmful factors
If the coating layer has high crosslink density to resist plasticizer migration, then chemical resistance improves, but the coating becomes brittle and more prone to cracking
Solution Approach 1:
The coating is segmented into layers with different crosslink densities. The first layer has high crosslink density for plasticizer resistance, while the second layer has lower crosslink density for flexibility and crack prevention, allowing both chemical resistance and mechanical strength to be optimized separately.
Solution Approach 2:
Different regions of the coating have different crosslink densities tailored to their specific functions: the inner layer has high crosslink density for chemical resistance where plasticizer contact is greatest, while the outer layer has lower crosslink density for mechanical flexibility and stress distribution.
3Stress or pressure
If the coating layer has large swelling rate to accommodate plasticizer migration, then stress relief improves, but the coating swells excessively and loses structural integrity
Solution Approach 1:
The coating is divided into layers with graded swelling rates. The first layer has small swelling rate to maintain dimensional stability and prevent excessive expansion, while the second layer has larger swelling rate to accommodate stress, distributing the swelling burden across layers.
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 enables the optical cable to maintain its coating integrity without cracking, even in environments where low molecular weight plasticizers migrate into the optical fiber, ensuring long-term use without deterioration.
Implementation Method 1
two coating layers selected from a plurality of layers constituting the coating are designed as to swelling rates thereof with a plasticizer for polyvinyl chloride resin so that an inside coating layer closer to the glass fiber has the smaller swelling rate than an outside coating layer farther from the glass fiber
Implementation Method 2
as long as crosslink points of molecules are firm, the cable jacket 20 itself hardly becomes cracked even with the plasticizers migrating to cause swelling
Data Source
AI summary
The present invention relates to an optical fiber and an optical cable which can be used for a long term even under environments in which an oil content migrates into them, and the optical fiber has a glass fiber extending along a predetermined axis, and a coating. The coating is composed of a plurality of layers each of which is comprised of an ultraviolet curable resin or a thermosetting resin, and swelling rates of the respective coating layers are set so that they increase from an outer peripheral surface of the glass fiber to an outer peripheral surface of the cable jacket.