Optical Fiber Tapered Coating Edge for Splice Reliability
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Solution Overview
Problem
In optical fibers with a two-layer coating structure, cracks often occur at the boundary between the primary and secondary resin layers during splicing, leading to increased transmission loss and reduced communication capacity due to the softness of the primary resin layer and the hardness of the secondary resin layer.
Innovation Solution
The method involves forming a tapered shape at the coating edge between the primary and secondary resin layers, with a length of the taper in the axial direction equal to or greater than 280 µm, and using a primary resin layer with a Young's modulus of 0.15 MPa or greater and 0.5 MPa or less, which reduces stress on the protective resin and prevents cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a soft primary resin layer is used to reduce nonlinearity and improve OSNR, then the effective cross-sectional area increases and nonlinearity decreases, but the coating layer becomes weak against side pressure and loss at bobbin winding increases
Solution Approach 1:
The patent employs a two-layer coating structure where the primary resin layer (soft, low Young's modulus) and secondary resin layer (hard, high Young's modulus) are combined. The soft primary layer reduces nonlinearity and improves OSNR, while the hard secondary layer provides mechanical strength to withstand side pressure during bobbin winding, thus resolving the contradiction between improving OSNR and reducing winding loss.
Solution Approach 2:
Different regions of the coating layer are assigned different mechanical properties: the inner primary resin layer has low Young's modulus (0.01-0.5 MPa) to reduce nonlinearity, while the outer secondary resin layer has high Young's modulus (100-1000 MPa) to provide mechanical strength. This local differentiation of material properties allows simultaneous optimization of both OSNR and mechanical durability.
2Reliability
If the effective cross-sectional area is increased to reduce nonlinearity, then OSNR improves, but the optical fiber becomes weak against side pressure and transmission loss increases
Solution Approach 1:
The two-layer coating structure combines materials with contrasting mechanical properties. The soft primary layer (low Young's modulus) enables larger effective cross-sectional area for reduced nonlinearity, while the hard secondary layer (high Young's modulus) compensates for the reduced side pressure resistance, thus resolving the contradiction between improving OSNR and maintaining mechanical strength.
Solution Approach 2:
The coating layer is divided into two regions with different mechanical properties: the primary resin layer close to the fiber core has low Young's modulus to facilitate stress distribution and reduce nonlinearity, while the secondary resin layer on the outer periphery has high Young's modulus to provide mechanical protection against side pressure, thereby resolving the strength-OOSNR trade-off.
3Reliability
If a tapered shape is formed at the coating edge to prevent peeling and cracking, then the protective resin is protected, but the manufacturing complexity increases
Solution Approach 1:
The coating edge is designed with an asymmetric tapered shape where the coating thickness gradually decreases toward the end portion. This asymmetric geometry prevents stress concentration at sharp edges, thereby preventing peeling and cracking of the protective resin, while the gradual transition simplifies the manufacturing process compared to more complex geometric modifications.
Solution Approach 2:
The coating edge is formed with a curved tapered shape instead of a sharp angular transition. This curvature distributes stress more evenly along the edge, preventing crack initiation and propagation in the protective resin. The smooth curved transition also simplifies manufacturing by avoiding sharp corners that would require complex tooling.
4Reliability
If the coating layer is made softer to reduce nonlinearity, then communication capacity increases, but the coating edge becomes more prone to cracking
Solution Approach 1:
The coating layer uses a composite structure where the primary resin layer has low Young's modulus (0.01-0.5 MPa) to reduce nonlinearity and increase communication capacity, while the secondary resin layer has high Young's modulus (100-1000 MPa) to strengthen the coating edge and prevent cracking. This composite approach resolves the contradiction between softness for capacity and strength for durability.
Solution Approach 2:
Different regions of the coating have different mechanical properties: the primary resin layer near the fiber core is soft to reduce nonlinearity and enhance communication capacity, while the secondary resin layer at the outer coating edge is hard to prevent cracking during handling and splicing, thus resolving the capacity-strength trade-off.
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
This approach effectively prevents cracks in the protective resin, enabling long-distance transmission with enhanced communication capacity by maintaining the quality of the optical fiber cable and reducing transmission loss.
Implementation Method 1
a primary resin layer on an inner peripheral side and having a Young's modulus of 0.15 MPa or greater and 0.5 MPa or less
Implementation Method 2
a coating edge of the primary resin layer and the secondary resin layer at an end portion of the optical fiber has a tapered shape which becomes narrower toward the end portion side
Implementation Method 3
end surfaces of glass fibers are fusion-spliced
Data Source
Figure 1A~2
Figure 3
Figure 4A~4B
AI summary
A method for manufacturing an optical fiber includes: a step of exposing a glass fiber by stripping a fiber coating layer at an end portion, on a splicing side, of each of a pair of optical fibers; a step of fusion-splicing end surfaces of the glass fibers; and a step of recoating a protective resin on a periphery of exposed portions of the glass fibers to protect the exposed portions. The fiber coating layer includes a primary resin layer on an inner peripheral side and having a Young's modulus of 0.5 MPa or less and a secondary resin layer on an outer peripheral side and having a Young's modulus of 800 MPa or greater, the step of exposing is a step of forming a shape of a coating edge of the fiber coating layer which includes the primary resin layer and the secondary resin layer into a tapered shape which becomes narrower toward the end portion side, and the step of recoating is a step of coating the protective resin to include the coating edge.