Multi-Core Optical Fiber W-Shaped Refractive Index Profile
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Solution Overview
Problem
Current technologies face challenges in simultaneously increasing transmission capacity, restraining non-linear phenomena, and optimizing effective core area in optical fibers, making it difficult to support further capacity enhancements through spatial multiplexing, mode-multiplexing, and effective-core-area-enlarging technologies separately.
Innovation Solution
A multi-core optical fiber design with a W-shaped refractive index profile, where center core portions have a higher refractive index than outer periphery core portions, which are lower than the cladding, allowing for propagation of multiple modes with effective core areas of at least 120 μm² at 1550 nm, thereby achieving spatial multiplexing, mode multiplexing, and enlarged effective core areas simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spatial multiplexing technology using multi-core optical fiber is used to increase transmission capacity, then transmission capacity is improved, but non-linear phenomenon increases and effective core area is reduced
Solution Approach 1:
The optical fiber is divided into multiple core portions (at least two cores) within a single cladding structure. Each core portion has a dedicated refractive index profile optimized for specific propagation modes, allowing spatial separation of different signal channels while maintaining large effective core areas that reduce non-linear effects in each individual core.
Solution Approach 2:
Different core portions are assigned different refractive index profiles tailored to their specific functions. The refractive index is locally optimized in each core region to support specific propagation modes with large effective core areas, while the cladding provides a uniform lower refractive index boundary. This local optimization allows each core to operate with reduced non-linearity while contributing to overall high transmission capacity.
2Productivity
If mode-multiplexing technology using multi-mode optical fiber is used to increase transmission capacity, then transmission capacity is improved, but mode coupling and dispersion increase
Solution Approach 1:
The fiber structure segments different propagation modes into distinct core portions with different refractive index profiles. This segmentation reduces unwanted mode coupling between cores by providing clear refractive index boundaries, while still allowing multiple modes to propagate within each core portion with optimized confinement.
Solution Approach 2:
The refractive index parameters are specifically designed and optimized for each core portion to control propagation characteristics. By adjusting the refractive index profiles in different core regions, the fiber supports specific propagation modes with reduced dispersion and controlled mode coupling, enabling reliable mode-multiplexing transmission.
3Object-generated harmful factors
If effective core area is enlarged to reduce non-linear phenomenon, then non-linearity is reduced, but transmission capacity is limited
Solution Approach 1:
Multiple core portions with large effective core areas are merged into a single multi-core optical fiber structure. Each core maintains its large effective area to reduce non-linear effects, while the combination of multiple cores provides the aggregate transmission capacity needed for high-speed communication systems.
Solution Approach 2:
The fiber structure transitions from a single-core two-dimensional cross-section to a multi-core three-dimensional arrangement. This dimensional expansion allows multiple large effective core areas to coexist within a compact fiber structure, simultaneously achieving reduced non-linearity in each core and increased total transmission capacity through the additional spatial dimension.
4Area of moving object
If W-shaped refractive index profile is used to enlarge effective core area, then effective core area is increased, but manufacturing precision requirements increase
Solution Approach 1:
The W-shaped refractive index profile is implemented with locally optimized parameters in each core portion. The refractive index distribution is tailored in each core region to achieve the desired large effective core area while maintaining compatibility with standard manufacturing processes. This local optimization allows flexibility in achieving target performance without requiring uniform ultra-precise control across the entire fiber structure.
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 realizes simultaneous spatial multiplexing, mode multiplexing, and enlarged effective core areas, enhancing transmission capacity while minimizing bending and micro-bending losses, and maintaining low non-linearity and good connectivity with other optical fibers.
Implementation Method 1
a cladding portion positioned at outer peripheries of the plurality of core portions, the cladding portion having a refractive index lower than a maximum refractive index of each of the core portions, in which each of the core portions propagates light
Data Source
AI summary
A multi-core optical fiber includes a plurality of core portions, and a cladding portion positioned at outer peripheries of the plurality of core portions, the cladding portion having a refractive index lower than a maximum refractive index of each of the core portions, in which each of the core portions propagates light only with predetermined number, which is equal to or greater than 2, of propagation modes, and an effective core area at wavelength of 1550 nm of each of the propagation modes is equal to or greater than 120 μm2.