Bend-Insensitive Multimode Fiber Leaky Mode Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional multimode optical fibers with depressed trenches improve bend-loss resistance but introduce leaky modes that affect optical characteristics, such as core size and numerical aperture measurements, leading to compatibility issues and inaccurate characterization.
Innovation Solution
A multimode optical fiber design with a refractive graded-index profile and a depressed trench within the cladding, where the trench width, inner cladding width, and trench index difference are optimized to satisfy specific inequalities, reducing the impact of leaky modes on optical characteristics while maintaining high bend-loss resistance and modal bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a depressed trench is added to improve bend-loss resistance, then bend-loss resistance is improved, but leaky modes are introduced that affect optical characteristics
Solution Approach 1:
The patent optimizes specific parameters of the depressed trench structure including the width W between 0.6-1.6 μm, the negative refractive index difference Δn_t, and the position of the trench. By carefully controlling these parameters, the design achieves bend-loss resistance while minimizing the generation and propagation of leaky modes that would otherwise distort optical characteristic measurements.
2Reliability
If a depressed trench is added to improve bend-loss resistance, then bend-loss resistance is improved, but compatibility with conventional fibers is reduced
Solution Approach 1:
The patent carefully controls the trench parameters (width W between 0.6-1.6 μm, depth Δn_t, and position) to ensure that while bend-loss resistance is improved, the overall fiber characteristics remain compatible with conventional multimode fibers. The optimized parameters ensure that leaky mode impact on numerical aperture and core size measurements remains within acceptable tolerances for interconnection.
3Measurement precision
If leaky mode impact is reduced through optimized trench parameters, then measurement accuracy is improved, but bend-loss resistance may be compromised
Solution Approach 1:
The patent achieves a balanced optimization where the trench width W (0.6-1.6 μm) and negative refractive index difference Δn_t are simultaneously tuned to satisfy both requirements: minimizing leaky mode generation for accurate measurements while maintaining sufficient bend-loss resistance. The specific parameter ranges represent the optimal compromise between these two competing requirements.
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 optimized design achieves a better trade-off between leaky mode resistance and bending losses, providing accurate core size measurements and improved compatibility with conventional fibers, while being simple and cost-effective to manufacture.
Implementation Method 1
the refractive index of the core, n c , is greater than the one of the cladding, n g . An optical fiber is generally characterized by a refractive index profile that associates the refractive index n with the radius r of the optical fiber
Implementation Method 2
the optical core having a refractive graded-index profile
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a multimode optical fiber comprising an optical core and an optical cladding surrounding the optical core, the optical core having a refractive graded- index profile, the optical cladding comprising: an inner layer surrounding said optical core, an intermediate layer, called "depressed trench", surrounding said inner layer, an outer layer surrounding said depressed trench and having a constant refractive index, said depressed trench having a width W and a negative refractive index difference Δnt with respect to the outer layer, and being designed so as to satisfy the following inequality: |0.585677 - 114.681 x S + 13.7287 x S 2 + 18.7343 x S x W - 4.61112 x S x Δn t.103 - 0.913789 x W x Δn t.103| +2 x W x Δn t.103 < -30 wherein: S is the width of the inner cladding, which is comprised between 0.6 μm and 1.6 μm; Δnt is comprised between -11.10-3 and -4.10-3; W x Δn t.103 is lower than -25 μm.