Optical Fiber Trench Cladding for Modal Interference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optical fibers with increased core diameters to reduce nonlinearity face signal degradation due to modal interference, and existing refractive index profiles that enhance effective area often result in complex designs and increased bending loss, making mass production challenging.
Innovation Solution
The optical fiber features a controlled variation in glass outer diameter during the drawing process, maintaining a cable cut-off wavelength below 1530 nm and achieving an effective area of 110-180 μm² at 1550 nm with reduced transmission loss by adjusting the refractive index profiles and outer diameter variation, allowing for increased effective area without excessive complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the core diameter of the optical fiber is increased to reduce nonlinearity and increase effective area, then the nonlinearity is reduced, but modal interference occurs between fundamental-mode light and high-order-mode light causing signal degradation
Solution Approach 1:
The patent applies local quality by creating a trench-type refractive index profile where the cladding region has a lower refractive index than the core, forming a localized refractive index difference that confines light to the core region. This local refractive index modification prevents high-order-mode propagation while maintaining a large core diameter for reduced nonlinearity.
Solution Approach 2:
The patent changes the refractive index parameter by introducing a trench structure with deliberately lowered refractive index in the cladding region. This parameter change (refractive index profile modification) enables the optical fiber to maintain large core diameter for high effective area while suppressing high-order modes through the refractive index barrier.
2Reliability
If complex refractive index profiles are used to increase effective area while maintaining cut-off wavelength, then the effective area increases, but the design complexity and manufacturing difficulty increase
Solution Approach 1:
The patent segments the cladding region into multiple zones with different refractive indices: an inner cladding region surrounding the core and an outer cladding region surrounding the inner cladding. The trench structure divides the cladding into functional zones that independently control mode propagation, simplifying the overall design while achieving the desired effective area and cut-off wavelength characteristics.
Solution Approach 2:
The patent employs composite material structure by combining regions with different refractive indices (core with higher index, inner cladding with intermediate index, outer cladding with lower index) to create a trench-type profile. This composite approach allows independent optimization of each region's properties to achieve both large effective area and controlled cut-off wavelength without excessive complexity.
3Manufacturing precision
If the glass outer diameter variation is reduced to improve manufacturing precision, then the manufacturing precision improves, but the productivity and mass production efficiency decrease
Solution Approach 1:
The patent changes the parameter of glass outer diameter variation by allowing controlled variation (3σ between 0.1-0.5 μm) rather than maintaining extremely tight tolerances. This parameter relaxation enables faster drawing speeds and more efficient mass production while the trench-type refractive index profile compensates for diameter variations to maintain consistent optical performance and cut-off wavelength.
Data Source
AI summary
The optical fiber has an effective area that is greater than or equal to 110 μm2 and less than or equal to 180 μm2 at a wavelength of 1550 nm and a cable cut-off wavelength of less than or equal to 1530 nm. An average value of a glass outer diameter in a longitudinal direction is 125±0.5 μm. When σ is a standard deviation of the glass outer diameter in the longitudinal direction, 3σ is greater than or equal to 0.1 μm and less than or equal to 0.5 μm.