W-Shaped Refractive Index Optical Fiber for Large Core Area
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Solution Overview
Problem
Conventional optical fibers face challenges in enlarging the effective core area to suppress nonlinear optical phenomena while maintaining low bending loss, especially when using fundamental and higher-order propagation modes for transmission.
Innovation Solution
The optical fiber design features a core and cladding structure with a W-shaped refractive index profile, where the outer core portion has a lower refractive index than the cladding, achieving an effective core area of at least 120 μm² for the fundamental mode and 170 μm² for the first higher-order mode, with an effective refractive index of the higher-order mode exceeding the cladding refractive index by at least 0.0005, thereby minimizing bending loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the effective core area is enlarged to suppress nonlinear optical phenomena, then nonlinear effects are suppressed, but bending loss increases
Solution Approach 1:
The patent applies local quality by creating a W-shaped refractive index profile where the outer core portion has a lower refractive index than the cladding. This localized variation in refractive index allows different regions to serve different functions: the center core maintains high refractive index for confinement while the outer core portion reduces bending loss through its lower index, thus simultaneously suppressing nonlinear effects and reducing bending loss.
Solution Approach 2:
The patent changes the refractive index parameter by introducing a W-shaped profile with specific characteristics: the outer core portion has a refractive index lower than the cladding by a controlled amount. This parameter change enables the fiber to achieve both large effective core area (for nonlinear suppression) and low bending loss, resolving the traditional trade-off between these two properties.
2Productivity
If the effective core area is enlarged to support higher-order propagation modes, then transmission capacity increases, but mode interference increases
Solution Approach 1:
The W-shaped refractive index profile creates local quality variations that selectively guide different propagation modes. The outer core portion with lower refractive index acts as a barrier that confines higher-order modes while allowing fundamental modes to propagate, thus increasing transmission capacity through mode-division multiplexing while reducing unwanted mode interference.
Solution Approach 2:
The outer core portion with its uniquely lower refractive index acts as an intermediary structure between the center core and cladding. This intermediary layer selectively manages different propagation modes, enabling the fiber to support multiple modes for increased capacity while using the refractive index contrast to minimize harmful mode coupling and interference.
3Ease of manufacture
If conventional optical fiber structure is used, then manufacturing is simple, but effective core area cannot be sufficiently enlarged
Solution Approach 1:
The patent segments the core into two distinct portions: a center core and an outer core portion. This segmentation allows independent optimization of each region's refractive index properties. The center core can be designed for standard manufacturing while the outer core portion introduces the W-shaped profile feature to enlarge the effective core area, thus achieving both manufacturability and enhanced performance.
Solution Approach 2:
The W-shaped refractive index profile introduces local quality variation specifically in the outer core portion, differentiating it from the center core. This localized modification enables the fiber to achieve a larger effective core area without fundamentally changing the overall fiber structure or manufacturing process, maintaining ease of manufacture while enhancing the effective core area through controlled local refractive index changes.
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 design achieves a large effective core area with small bending loss in both propagation modes, reducing interference between modes and enhancing optical transmission capacity while suppressing nonlinear effects.
Implementation Method 1
an optical fiber including a core portion and a cladding portion formed on an outer periphery of the core portion... an effective refractive index of the first higher-order propagation mode of larger than a refractive index of the cladding portion
Data Source
AI summary
An optical fiber includes a core portion and a cladding portion that is formed on an outer periphery of the core portion and has a refractive index lower than a maximum refractive index of the core portion. Characteristics at a wavelength of 1550 nm are an effective core area of a fundamental propagation mode of equal to or larger than 120 μm2, an effective core area of a first higher-order propagation mode of equal to or larger than 170 μm2, and an effective refractive index of the first higher-order propagation mode of larger than the refractive index of the cladding portion by equal to or larger than 0.0005.