Optical Fiber Coating Structure for Lower Microbend Loss
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Solution Overview
Problem
Existing approximation formulas for calculating microbend loss in optical fibers are inaccurate for diameters other than 125 µm, leading to increased deviations between calculated and actual microbend loss values, particularly in fibers with smaller diameters.
Innovation Solution
An optical fiber design with specific relationships between lateral rigidity D and flexural rigidity H, defined by Formula (3), along with a coating concentricity error of 8 µm or less, to reliably reduce microbend loss, using a glass fiber with a core and resin layers with specified radii and moduli, and a secondary resin layer thickness of 5 µm or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the optical fiber diameter is reduced to achieve smaller cable diameter and higher density, then the transportation and laying costs are reduced, but the microbend loss increases
Solution Approach 1:
The patent applies parameter changes by establishing specific mathematical relationships between the lateral rigidity D and flexural rigidity H of the optical fiber. Formula (3) defines precise parameter ranges: 0.003 ≤ D/H² ≤ 0.006 when 0.06 ≤ H ≤ 0.12, and 0.006 < D/H² ≤ 0.012 when 0.12 < H ≤ 0.24. By controlling these rigidity parameters within specified ranges, the patent reduces microbend loss while maintaining reduced fiber diameter, thus resolving the contradiction between smaller size and lower energy loss.
Solution Approach 2:
The patent employs composite materials through the resin coating structure consisting of a primary resin layer and a secondary resin layer with different mechanical properties. The primary resin layer has specific Young's modulus ranges (0.01-0.8 MPa) and the secondary resin layer has different properties (Young's modulus 100-3000 MPa). This composite coating structure provides both flexibility to reduce microbend loss and sufficient mechanical strength, enabling the fiber to maintain low microbend loss at reduced diameters.
2Device complexity
If the approximation formula from Patent Literature 1 is used for calculating microbend loss, then the calculation is simplified, but the accuracy decreases for fibers with diameters other than 125 µm
Solution Approach 1:
The patent improves calculation accuracy by introducing diameter-dependent parameter changes. The new Formula (3) adjusts the D/H² ratio ranges based on the flexural rigidity H values, creating specific parameter ranges for different fiber types. This parameter adaptation allows accurate microbend loss estimation across various fiber diameters (75-130 µm) while maintaining computational simplicity, thus resolving the contradiction between calculation ease and accuracy.
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 reduces microbend loss in optical fibers with diameters ranging from 75 µm to 130 µm, maintaining low deviation between calculated and measured values, and prevents damage to the coating and breakage from foreign matter.
Implementation Method 1
a Young's modulus of the glass fiber is denoted by E0, a Young's modulus of the primary resin layer is denoted by E1, and a Young's modulus of the secondary resin layer is denoted by E2
Data Source
Figure 1
AI summary
An optical fiber includes a glass fiber including a core and a cladding surrounding the core, a primary resin layer surrounding the glass fiber, and a secondary resin layer surrounding the primary resin layer. In the optical fiber, in a case where a radius of the glass fiber is denoted by R0 [m], a Young's modulus of the glass fiber is denoted by E0 [N/m2], a radius of the primary resin layer is denoted by R1 [m], a Young's modulus of the primary resin layer is denoted by E1 [N/m2], a radius of the secondary resin layer is denoted by R2 [m], and a Young's modulus of the secondary resin layer is denoted by E2 [N/m2], a relationship between a lateral rigidity D [N/m2] of the optical fiber represented by Formula (1) and a flexural rigidity H [N·m2] of the optical fiber represented by Formula (2) satisfies Formula (3), and a coating concentricity error is 8 µm or less. D=c11−R0R2c2+c3E2−E110∑i,j,kcijklog10R2−R1R2−R0ilog10E1E2jlog10R0R2k+E11H∝πR04E0+πR24−R14E22D/H2N−1⋅m−6≦6.6×1018N−1⋅m−63