Trench-Assisted Multimode Fiber Leakage Loss Reduction
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Solution Overview
Problem
Multimode optical fibers with depressed graded-index profiles face challenges in minimizing leakage losses and maintaining bandwidth and core size consistency due to the presence of additional leaky modes introduced by trenches in the cladding, which complicates manufacturing and connectivity.
Innovation Solution
A trench-assisted depressed graded-index multimode fiber design is proposed, where the trench is strategically positioned and dimensioned to minimize leakage losses while controlling the presence of additional leaky modes, maintaining the core size and bandwidth by optimizing the refractive index differences and trench volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a trench is added to the cladding of a depressed graded-index multimode fiber, then leakage losses are reduced, but additional leaky modes are introduced which complicates manufacturing and connectivity
Solution Approach 1:
The patent applies parameter changes by precisely controlling the trench depth (Δn between -0.003 and -0.008) and width (between 2 and 10 μm) to optimize the balance between reducing leakage losses and limiting additional leaky modes. By adjusting these parameters within specific ranges, the fiber achieves reduced leakage without excessive complexity in connectivity and manufacturing.
2Ease of manufacture
If the external cladding is brought closer to the graded-index core, then manufacturing costs are reduced, but leakage losses increase and fiber characteristics become inconsistent
Solution Approach 1:
The trench acts as an intermediary structure between the graded-index core and the external cladding. It provides a controlled refractive index transition zone that allows the external cladding to be positioned closer to the core (reducing manufacturing cost) while simultaneously preventing excessive leakage losses and maintaining fiber characteristic consistency through its specific depth and width parameters.
3Loss of energy
If the trench depth and width are increased to further reduce leakage losses, then more additional leaky modes are generated, worsening manufacturing and connectivity
Solution Approach 1:
The patent applies parameter changes by establishing optimal ranges for trench depth (Δn between -0.003 and -0.008) and width (between 2 and 10 μm). These parameter specifications ensure sufficient leakage loss reduction while preventing excessive generation of additional leaky modes that would complicate connectivity operations.
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 reduces leakage losses and fiber length dependence of bandwidth, core size, and numerical aperture, while reducing manufacturing costs by bringing the external cladding closer to the graded-index core without compromising fiber characteristics.
Implementation Method 1
the refractive indices of the core n core and the cladding n cladding are such that n core >n cladding
Data Source
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AI summary
It is proposed a multimode optical fibre comprising: - a core region with a first radius (R1) and a profile alpha with a maximum optical core index, - an inner depressed cladding extending radially from the first radius (R1) to a second radius (R2), - a trench extending from the second radius (R2) to a third radius (R3), - an outer depressed cladding extending radially from the third radius (R3) to a fourth radius (R4), - an external cladding extending radially from the fourth radius (R4), wherein: - the volume of the trench is comprised between 1650 x 10-3 µm2 and 4500 x 10-3 µm2, - the difference in distance between the second radius (R2) and the first radius (R1) is comprised between 0.6 µm and 3.5 µm, - the fourth radius (R4) is comprised between 30 µm and 47 µm. The multimode fibre enables to reduce the down-doped cladding to be deposited without increasing the leakage losses of the modes.