Optical Fiber Dual-Layer Coating for Lateral Pressure Resistance
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Solution Overview
Problem
Optical fibers with large effective areas required for high-speed digital coherent communication technologies face challenges in maintaining resistance against lateral pressure and minimizing transmission loss when wound on bobbins, leading to increased defective proportions and longer annealing times.
Innovation Solution
An optical fiber design featuring a core and clad with a primary resin layer having a Young's modulus of 0.7 MPa or lower and a secondary resin layer with a modulus of 600-1500 MPa, along with specific outer diameter ranges, to enhance resistance against lateral pressure and reduce transmission loss differences when wound on a bobbin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the effective area of the optical fiber is increased to improve OSNR, then the optical signal-to-noise ratio is improved, but the resistance against lateral pressure deteriorates and transmission loss when wound on a bobbin increases
Solution Approach 1:
The coating layer is divided into two distinct layers: a soft primary resin layer (0.01-0.7 MPa) that provides lateral pressure resistance and protects the large-effective-area optical transmission member, and a hard secondary resin layer (0.7-1.5 GPa) that provides mechanical strength and dimensional stability. This segmentation allows each layer to specialize in different protective functions, resolving the contradiction between protecting the large effective area and maintaining lateral pressure resistance.
Solution Approach 2:
The patent uses a composite coating structure combining two resin materials with vastly different mechanical properties. The primary resin layer uses soft material (low Young's modulus) to cushion lateral pressure, while the secondary resin layer uses hard material (high Young's modulus) to maintain structural integrity. This composite approach allows the optical fiber to simultaneously achieve large effective area for high OSNR and sufficient mechanical strength for lateral pressure resistance.
2Reliability
If the effective area of the optical fiber is increased to improve OSNR, then the optical signal-to-noise ratio is improved, but the transmission loss when wound on a bobbin increases and relaxation time becomes longer
Solution Approach 1:
The soft primary resin layer is applied beforehand to cushion and distribute the lateral pressure exerted during the winding process on the bobbin. This pre-cushioning prevents excessive point loads on the optical transmission member that would cause microbending losses, thereby reducing transmission loss even when the fiber is wound with large effective area.
Solution Approach 2:
The patent carefully controls the Young's modulus of the primary resin layer to be between 0.01-0.7 MPa, which is soft enough to provide cushioning during winding but firm enough to maintain shape. This parameter optimization allows the fiber to tolerate winding stresses without excessive transmission loss while maintaining the large effective area needed for high OSNR.
3Reliability
If the effective area of the optical fiber is increased to improve OSNR, then the optical signal-to-noise ratio is improved, but the relaxation time becomes longer and defective proportion increases
Solution Approach 1:
The dual-layer coating structure provides dynamic response to mechanical stresses: the soft primary layer deforms easily during winding to absorb stress, then gradually relaxes without causing permanent damage to the optical transmission member. The hard secondary layer maintains overall dimensional stability throughout the relaxation process. This dynamic behavior reduces both relaxation time and defective proportion while allowing large effective area for high OSNR.
Data Source
AI summary
An optical fiber 1A comprises an optical transmission member 10 including a core 12 and a clad 14, a primary resin layer 22, and a secondary resin layer 24. The effective area of the optical transmission member 10 is 130 μm2 or larger. The transmission loss of the optical transmission member 10 at a wavelength of 1550 nm is 0.165 dB/km or smaller. The Young's modulus of the primary resin layer 22 is 0.7 MPa or lower, and the Young's modulus of the secondary resin layer 24 is 600 MPa or higher and 1500 MPa or lower. The difference between the transmission loss when the optical fiber 1A is wound at a tension of 80 g around a bobbin on which a metal mesh member having vertical wires of a 50-μm diameter and horizontal wires of a 50-μm diameter are wound and spaced at a pitch of 150 μm, and the transmission loss of an optical fiber coil is 1.0 dB/km or smaller.