Coated Optical Fiber Microbend Loss Suppression
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Solution Overview
Problem
Existing optical fibers with high microbend sensitivity, such as BI fibers with large effective core cross-sectional areas, face challenges in suppressing transmission loss due to microbend-induced stresses, as adjusting the elastic modulus of coating layers alone is insufficient.
Innovation Solution
A coated optical fiber design featuring a primary layer and a secondary layer with specific thermal expansion coefficients and elastic moduli, where the product of the primary layer's thermal expansion coefficient and elastic modulus is ≥600, and the ratio of the secondary layer's elastic modulus to the primary layer's is ≤1000, ensuring appropriate mobility and rigidity to mitigate microbend-induced transmission loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the elastic modulus of the primary layer is reduced and the elastic modulus of the secondary layer is increased to suppress transmission loss, then microbend resistance is improved, but it becomes difficult to suppress transmission loss in high microbend sensitivity fibers (BI fibers with large Aeff)
Solution Approach 1:
The invention introduces a new parameter relationship (βP×PISM≥600) that changes the approach from simply adjusting elastic modulus values to optimizing the product of thermal expansion coefficient and elastic modulus. This parameter transformation enables effective suppression of transmission loss in high microbend sensitivity fibers where conventional elastic modulus adjustment fails.
Solution Approach 2:
The invention uses a composite coating structure with two layers having different material properties. The primary layer has high thermal expansion coefficient and elastic modulus product, while the secondary layer has controlled elastic modulus. This composite approach allows the primary layer to provide microbend suppression through thermal-mechanical coupling while the secondary layer provides structural support, solving the limitation of single-layer or conventional two-layer designs for BI fibers.
2Quantity of substance
If the coating thicknesses are reduced to attain high density and high fiber count in optical cables, then cable density is improved, but lateral pressure characteristics deteriorate
Solution Approach 1:
By changing the design parameter from elastic modulus alone to the product of thermal expansion coefficient and elastic modulus (βP×PISM≥600), the invention enables thinner coating layers to achieve the same or better microbend suppression performance. This allows reduced coating thickness while maintaining lateral pressure resistance, enabling higher fiber count and cable density.
Solution Approach 2:
The primary layer is designed with specific local properties (high thermal expansion coefficient and elastic modulus product) that concentrate the microbend suppression function in a thin layer. This localized optimization allows the coating to be thinner overall while maintaining sufficient lateral pressure resistance, supporting higher cable density.
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 coated optical fiber effectively suppresses transmission loss to 1.0 dB/km or less, even in high microbend-sensitive fibers, by optimizing the degree of freedom and rigidity of the coating layers, thereby reducing microbend loss and maintaining fiber integrity.
Implementation Method 1
a thermal expansion coefficient of the primary layer is βP (/K)... a relationship of the following equations (I) and (II) is established: βP×PISM≥600 (I)
Implementation Method 2
an elastic modulus (primary elastic modulus) of the primary layer is PISM (MPa), and an elastic modulus (secondary elastic modulus) of the secondary layer is SISM (MPa)... the degree of freedom of a primary layer represented by the equation (I) and the rigidity of a secondary layer represented by the equation (II)
Data Source
AI summary
Provided is a coated optical fiber and an optical fiber cable capable of suppressing transmission loss (microbend loss) even in an optical fiber having high microbend sensitivity.In the present invention, the degree of freedom of a primary layer 11 represented by the equation (I) and the rigidity of a secondary layer 12 represented by the equation (II) are set in specific ranges, respectively. Thus, the present invention provides a coated optical fiber 1 capable of suppressing the transmission loss even when an optical fiber 10 having high microbend sensitivity such as a BI fiber having a large effective core cross-sectional area Aeff of an optical fiber is used. The present invention can be widely used as a coated optical fiber 1 constituting a coated optical fiber ribbon or as a coated optical fiber 1 housed in an optical fiber cable. Further, an optical fiber cable including such coated optical fibers 1 enjoys the effect of the above-described coated optical fiber 1. [Math. 1]βP×PISM≥600 (I)(S/P)×(SISM/PISM)≤1,000 (II)