Multicore Amplifying Fiber Crosstalk Reduction
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Solution Overview
Problem
Multicore erbium doped fibers used for amplifying communication light experience significant crosstalk between adjacent cores, leading to communication troubles.
Innovation Solution
An amplifying optical fiber with a specific refractive index structure, including a plurality of cores with a higher refractive index than the first cladding, which is itself higher than the second cladding, and a two-layer cladding structure, optimizes inter-core distance and pumping light distribution to reduce crosstalk and enhance amplification efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a multicore EDF is used for amplification of communication light, then amplification capability is improved, but crosstalk between adjacent cores increases causing communication trouble
Solution Approach 1:
The patent applies local quality by creating different refractive index regions within the cladding structure. The first cladding has a higher refractive index than the second cladding, forming distinct optical confinement zones around each core. This localized refractive index differentiation suppresses evanescent field coupling between adjacent cores while maintaining effective amplification in each core, thereby reducing crosstalk below -30 dB
Solution Approach 2:
The patent utilizes parameter changes by optimizing the refractive index values of the cladding layers and their relative differences. By carefully controlling the refractive index relationship (n_core > n_first_cladding > n_second_cladding) and adjusting these parameters within specific ranges, the patent achieves both effective light confinement for amplification and sufficient isolation between cores to minimize crosstalk
2Object-generated harmful factors
If the inter-core distance is increased to reduce crosstalk, then crosstalk suppression is improved, but the outer diameter of the first cladding increases leading to higher breaking probability
Solution Approach 1:
The patent applies parameter changes by optimizing the inter-core distance Λ within a specific range that balances crosstalk suppression and mechanical strength. By controlling Λ to satisfy 5.8≦Λ/MFD(2λc/(λc+λop))≦8, the patent achieves sufficient core isolation for low crosstalk while maintaining an outer diameter of the first cladding at 225 μm or less, thereby preserving fiber mechanical strength and reducing breaking probability
Solution Approach 2:
The patent employs composite material structure with multiple cladding layers having different refractive indices. This composite structure allows the first cladding to provide optical confinement and the second cladding to provide additional mechanical protection and isolation, enabling the system to achieve both low crosstalk and high mechanical reliability without requiring excessive increases in outer diameter
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 solution effectively suppresses crosstalk below -30 dB, preventing communication troubles and improving amplification efficiency while maintaining a safe outer diameter for the optical fiber.
Implementation Method 1
a plurality of cores to which an active element is doped
Implementation Method 2
a refractive index of the core is provided higher than a refractive index of the first cladding, the refractive index of the first cladding is provided higher than a refractive index of the second cladding
Data Source
AI summary
A plurality of cores 51 is disposed around the center axis of a first cladding 52 in a state in which an inter-core distance Λ of cores adjacent to each other is equal, a refractive index n1 of the core 51 is provided higher than a refractive index n2 of the first cladding 52, and the refractive index n2 of the first cladding 52 is provided higher than a refractive index n3 of a second cladding 53. Moreover, 5.8≦Λ/MFD(2λc/(λc+λop))≦8 is satisfied, where the inter-core distance is defined as Λ, a mode field diameter of the core is defined as MFD, a cutoff wavelength is defined as λc, and a wavelength of communication light incident on the core 51 is defined as λop.