Dual-Layer Optical Fiber Coating for Low-Loss Miniaturization
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Solution Overview
Problem
Reducing the diameter of optical fibers while maintaining lateral pressure resistance and low-temperature characteristics is challenging due to the thinning of the coating resin layer, which increases transmission loss and susceptibility to bending.
Innovation Solution
A glass fiber with a core and cladding, coated by a primary resin layer and a secondary resin layer, where the primary resin layer has a thickness of 5 μm or more and an elastic modulus of 0.1 MPa to 0.4 MPa, and the secondary resin layer has a thickness of 5 μm or more and an elastic modulus of 1200 MPa to 2800 MPa, with a maximum eccentricity amplitude of 10 μm or less, to stabilize the fiber and enhance resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the outer diameter of the optical fiber is reduced to 210 μm or less, then the fiber size is reduced for better adaptability, but the coating resin layer becomes thin causing deterioration of lateral pressure resistance characteristics
Solution Approach 1:
The coating resin layer is divided into two distinct layers: a primary resin layer (5-20 μm) with low elastic modulus (0.1-0.4 MPa) that provides lateral pressure resistance, and a secondary resin layer (5-15 μm) with high elastic modulus (1200-2800 MPa) that provides mechanical strength. This segmentation allows each layer to specialize in different protective functions, enabling the fiber to maintain strength while reducing overall diameter.
Solution Approach 2:
The patent uses composite material structure with two resin layers having vastly different elastic moduli. The primary resin layer uses soft material (low modulus) to resist lateral pressure, while the secondary resin layer uses hard material (high modulus) to provide mechanical strength. This composite approach allows the fiber to achieve both small size and high strength simultaneously, resolving the contradiction between fiber size reduction and lateral pressure resistance.
2Adaptability or versatility
If the coating resin layer is thinned to reduce fiber diameter, then the fiber becomes more flexible, but transmission loss increases due to micro-bending
Solution Approach 1:
The segmented coating structure with primary and secondary layers provides differentiated protection: the soft primary layer absorbs lateral pressure to prevent micro-bending, while the hard secondary layer maintains structural integrity. This segmentation enables the fiber to remain flexible with reduced diameter while preventing the micro-bending that causes transmission loss.
3Strength
If the primary resin layer elastic modulus is reduced to improve lateral pressure resistance, then the fiber becomes more resistant to bending, but low-temperature characteristics deteriorate
Solution Approach 1:
The segmentation of the coating into primary and secondary layers resolves this contradiction by assigning different functional roles to each layer. The primary layer with low elastic modulus handles lateral pressure resistance, while the secondary layer with high elastic modulus provides the structural support needed for low-temperature reliability. Together, they enable both bending resistance and low-temperature performance.
Solution Approach 2:
The composite material structure combines soft primary resin and hard secondary resin to achieve both lateral pressure resistance and low-temperature characteristics. The primary layer's low modulus provides bending resistance, while the secondary layer's high modulus maintains structural integrity at low temperatures, resolving the contradiction between these two performance requirements.
4Adaptability or versatility
If the glass fiber outer diameter is reduced to 80 μm, then the overall fiber size is reduced, but the coating layer thickness is reduced causing increased breakage frequency
Solution Approach 1:
The dual-layer composite coating structure provides enhanced protection for the reduced-diameter glass fiber. The primary resin layer (5-20 μm) with low elastic modulus cushions the glass fiber against lateral pressure and mechanical stress, while the secondary resin layer (5-15 μm) with high elastic modulus provides rigid structural support. This composite protection system enables the fiber to maintain low breakage frequency despite the reduced glass fiber diameter of 80 μm.
Data Source
AI summary
The optical fiber includes a glass fiber and a coating resin layer. The coating resin layer includes a primary resin layer and a secondary resin layer. The glass fiber has an outer diameter of from 79 μm to 81 μm. The secondary resin layer has an outer diameter of from 120 μm to 170 μm. The primary resin layer has an in situ elastic modulus of from 0.1 MPa to 0.4 MPa. The secondary resin layer has an in situ elastic modulus of from 1200 MPa to 2800 MPa. A maximum value of amplitude of an amount of eccentricity is 10 μm or less in a spectrum obtained by measuring the amount of eccentricity of the glass fiber and by applying Fourier transform to a waveform representing the amount of eccentricity.