Four-Core Optical Fiber Layout Using Two-Stage Cladding to Limit Crosstalk
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Solution Overview
Problem
Existing multicore optical fibers with a standard cladding diameter of 125 μm face limitations in transmission distance due to inter-core crosstalk, restricting the number of cores to two for thousands of kilometers, making it difficult to dispose three or more cores while maintaining compatibility with existing optical interfaces and ensuring low crosstalk.
Innovation Solution
A multicore optical fiber design with two-stage claddings of different refractive indices, featuring four cores in a square lattice shape, a first cladding region with a specific refractive index difference, and a second cladding region with a higher refractive index difference, optimized to reduce crosstalk and maintain a cladding diameter of 125 μm, allowing for long-distance transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the cladding diameter is increased to 150-230 μm to reduce inter-core crosstalk, then crosstalk is reduced, but productivity decreases significantly
Solution Approach 1:
The patent changes the refractive index parameters of the cladding regions to achieve crosstalk reduction without increasing cladding diameter. By optimizing the refractive index difference between cores and cladding, and between different cladding regions, the patent achieves low crosstalk while maintaining standard 125 μm cladding diameter, thus resolving the contradiction between crosstalk reduction and productivity.
2Object-affected harmful factors
If the cladding diameter is increased to 150-230 μm to reduce inter-core crosstalk, then crosstalk is reduced, but peripheral parts need re-design
Solution Approach 1:
The patent maintains the standard 125 μm cladding diameter by optimizing refractive index parameters rather than increasing physical dimensions. This ensures compatibility with existing peripheral parts and connectors, avoiding the need for re-design while achieving low crosstalk through refractive index optimization.
3Quantity of substance
If four cores are disposed in a standard 125 μm cladding diameter fiber, then transmission capacity increases, but inter-core crosstalk deteriorates
Solution Approach 1:
The patent introduces a two-stage cladding structure with different refractive indices around each core. The first cladding region has a specific refractive index difference Δ1 and the second cladding region has a different refractive index difference Δ2. This local differentiation of refractive index properties allows for reduced inter-core crosstalk while maintaining four cores in a standard 125 μm cladding diameter configuration.
Solution Approach 2:
The patent employs a composite cladding structure with two different refractive index materials arranged in stages around each core. This composite structure enables simultaneous achievement of high core density (four cores) and low inter-core crosstalk by leveraging the different optical properties of the two cladding regions.
4Object-affected harmful factors
If the core interval is increased to reduce inter-core crosstalk, then crosstalk is reduced, but the fiber length decreases
Solution Approach 1:
The patent changes the refractive index parameters to reduce crosstalk without increasing core interval. By optimizing the refractive index difference between cores and cladding regions, the patent achieves effective crosstalk suppression while maintaining appropriate core spacing, thus preserving fiber length.
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 design enables a multicore optical fiber with four cores and a cladding diameter of 125 μm, supporting transmission over several thousands of kilometers with reduced crosstalk, compatible with existing optical fibers, and increasing transmission capacity and reducing power consumption.
Implementation Method 1
a first cladding region disposed around the core and having a radius a2 with a refractive index lower than the refractive index of the core
Implementation Method 2
a second cladding region disposed on an outer periphery of the first cladding region and having a refractive index higher than the refractive index of the first cladding region and lower than the refractive index of the core
Data Source
AI summary
It is an object of the present invention to provide a multicore optical fiber, a design method for the multicore optical fiber and an optical transmission method using the multicore optical fiber including four cores having a standard cladding diameter of 125±1 μm for an existing single mode optical fiber covering several thousands of kilometers of transmission. The multicore optical fiber according to the present invention disposes two-stage claddings with different refractive indices around each core, and designates as a predetermined range, a core radius a1, a radius a2 of a first cladding region surrounding each core, specific refractive index Δ1 relative to the core of the first cladding region and a specific refractive index Δ2 relative to the core of a second cladding region including four cores and the first cladding region.