Plastic Optical Fiber Core Structure for Low Bending Loss Bandwidth
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Solution Overview
Problem
Plastic optical fibers (POFs) with trenches designed to reduce bending loss degrade signal bandwidth, particularly in short-distance applications, as light reflected by the trench causes significant band degradation, with existing techniques failing to effectively improve bandwidth in such scenarios.
Innovation Solution
A POF design featuring a core with a first region having a decreasing refractive index and a second region with a constant refractive index, both surrounded by a trench with a lower refractive index, where the second region's thickness is between 2 μm and 5 μm, minimizing light reflection and maintaining signal integrity over short distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a trench is provided on the outer circumference of the core to reduce bending loss, then bending loss decreases, but band degradation occurs due to light reflection at the trench
Solution Approach 1:
The patent introduces a second region with constant refractive index as an intermediary layer between the first region (decreasing refractive index) and the trench. This intermediate layer with refractive index n2 (where n1 ≥ n2 > n3) reduces the abrupt refractive index difference at the core-trench interface, thereby minimizing light reflection and band degradation while preserving the bending loss reduction benefit of the trench structure
Solution Approach 2:
The patent optimizes the thickness of the second region to be 2 μm or more and less than 5 μm. This specific parameter range controls the reflection characteristics at the trench interface, achieving a balance between reducing bending loss and minimizing band degradation through precise parameter control
2Length of moving object
If the POF extends over a shorter distance, then it is more suitable for terminal section use, but band degradation from trench reflection becomes more significant
Solution Approach 1:
The patent introduces a second region with constant refractive index and optimizes its thickness to 2-5 μm. This parameter change in the refractive index profile modifies the light propagation characteristics, reducing reflection at the trench interface and thereby improving band performance in short-distance applications
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 configuration achieves a bandwidth of 40 MHz-km or more over 5 meters with reduced bending losses, specifically 3.0 dB or less at a 1.5 mm bending radius and 0.5 dB or less at a 2.0 mm radius, enhancing signal transmission in short-distance applications.
Implementation Method 1
the first region having a refractive index n1 decreasing in a direction from a center of the core toward an outer edge of the core, the second region being positioned on an outer circumference of the first region, the second region having a refractive index n2 being constant
Implementation Method 2
a refractive index n3 of the trench is lower than the refractive index n2 of the second region
Data Source
AI summary
A plastic optical fiber of the present disclosure includes a core and a trench disposed on an outer circumference of the core. The core includes a first region and a second region, the first region having a refractive index n1 decreasing in a direction from a center of the core toward an outer edge of the core, the second region being positioned on an outer circumference of the first region, the second region including the outer edge of the core, the second region having a refractive index n2 being constant. The refractive index n2 of the second region is equal to or lower than the refractive index n1 of the first region, a thickness of the second region is 2 μm or more and less than 5 μm, and a refractive index n3 of the trench is lower than the refractive index n2 of the second region.