Optical Fiber Cladding Diameter and Refractive Index Profile
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Solution Overview
Problem
There is a demand for optical fibers that have high compatibility with the G.652 standard and a smaller diameter than conventional optical fibers, while maintaining optimal refractive index profiles and coating layers to reduce microbending loss.
Innovation Solution
An optical fiber with a core and cladding made of silica-based glass, featuring a primary and secondary coating layer structure, where the cladding diameter is less than 100 µm, a relative refractive-index difference of 0.33% to 0.40%, and a mode field diameter of 8.6 µm to 9.2 µm at 1310 nm, along with a reduced effective cutoff wavelength and microbending loss, achieved through specific refractive index profiles and coating thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the cladding diameter is reduced to implement a small diameter optical fiber, then the cable density is improved, but the microbending loss increases
Solution Approach 1:
The patent applies parameter changes by optimizing the relative refractive-index difference (Δ1) of the core portion to be 0.33% to 0.40%, which is a specific range different from conventional values. This parameter adjustment allows the optical fiber to maintain low microbending loss despite the reduced cladding diameter of less than 100 μm, resolving the contradiction between small diameter and low loss
Solution Approach 2:
The patent implements local quality by creating a trench layer with a specific refractive index profile (Δ2 between -0.20% and 0%) at a defined position relative to the core. This localized structural modification with specific refractive index characteristics helps control microbending loss in the critical region near the core, enabling small diameter while maintaining performance
2Volume of moving object
If the relative refractive-index difference is increased to reduce diameter, then the fiber diameter is reduced, but the compatibility with G.652 standard deteriorates
Solution Approach 1:
The patent carefully selects the relative refractive-index difference parameter Δ1 within the specific range of 0.33% to 0.40%. This parameter optimization achieves the dual goal of reducing fiber diameter while maintaining compatibility with G.652 standard, as the mode field diameter (8.6-9.2 μm at 1310 nm) and effective cutoff wavelength (≤1260 nm) meet standard requirements
Solution Approach 2:
The patent segments the refractive index profile into distinct regions: the core portion with relative refractive-index difference Δ1, and the trench layer with relative refractive-index difference Δ2. This segmentation allows independent optimization of each region's parameters to simultaneously achieve small diameter and G.652 compatibility
3Area of moving object
If the core area is increased to improve transmission capacity, then the transmission capacity is improved, but the microbending loss increases
Solution Approach 1:
The patent applies local quality by introducing a trench layer with specific refractive index characteristics (Δ2 between -0.20% and 0%) positioned at a specific distance from the core center. This localized structural feature with controlled refractive index creates a potential well that confines the optical mode, allowing larger core area for high capacity while the trench structure prevents microbending loss by stabilizing the mode distribution
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 optical fiber achieves high compatibility with the G.652 standard, a smaller diameter, and reduced microbending loss, making it suitable for high-density optical fiber cables with improved transmission characteristics.
Implementation Method 1
an optical fiber including: a core portion (1a) made of silica based glass; a cladding portion (1b) made of silica based glass and configured to cover an outer periphery of the core portion (1a), the cladding portion (1b) having a refractive index that is lower than a maximum refractive index of the core portion (1a)
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
To provide an optical fiber having high compatibility with respect to G.652 standard and a further smaller diameter, the optical fiber includes a core portion made of silica based glass; a cladding portion made of silica based glass and configured to cover an outer periphery of the core portion, the cladding portion having a refractive index that is lower than a maximum refractive index of the core portion; and a coating portion configured to cover an outer periphery of the cladding portion, the coating portion including a primary coating layer located on the cladding portion side and a secondary coating layer located on an outer peripheral side of the primary coating layer. An outer diameter of the cladding portion is less than 100 µm, a thickness of the primary coating layer is larger than or equal to 15 µm, a mode field diameter at a wavelength of 1310 nm is larger than or equal to 8.6 µm and smaller than or equal to 9.2 µm, an effective cutoff wavelength is smaller than or equal to 1260 µm, and a bending loss at a wavelength of 1550 nm when bending is made at a diameter of 60 mm is smaller than or equal to 0.1 dB/100 turn.