Multimode Optical Fiber Trench Cladding Bandwidth
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Solution Overview
Problem
Multimode optical fibers experience higher transmission loss and limited bandwidth due to group delay differences between propagation modes, and are prone to damage and increased bending loss during installation, especially in short-haul communication applications.
Innovation Solution
A graded index-type multimode optical fiber with a refractive index profile that decreases continuously from the central axis, featuring a trench region with a low refractive index and a thin hard plastic coated silica fiber, which reduces group delay differences and enhances resistance to bending-induced fluctuations, incorporating a coating member with a higher refractive index than the core region to facilitate leakage of higher-order modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a multimode optical fiber uses a conventional structure with core and cladding regions, then it enables short-haul communication with easy connection, but it suffers from limited bandwidth due to large group delay difference between propagation modes
Solution Approach 1:
The optical fiber structure is segmented into multiple functional regions: core region, first cladding region, second cladding region (trench part), and third cladding region. This segmentation allows each region to serve specific purposes - the core for light transmission, the first cladding for basic confinement, the second cladding for reducing group delay difference through low refractive index, and the third cladding for mechanical protection, thereby resolving the contradiction between ease of connection and bandwidth limitation.
Solution Approach 2:
The patent applies local quality by creating a trench part (second cladding region) with specifically lower refractive index than both the core and first cladding regions. This localized modification of refractive index properties in the second cladding region directly addresses the group delay difference issue and expands bandwidth, while the overall fiber structure remains compatible with standard connection procedures.
2Ease of operation
If a multimode optical fiber is subjected to fusion splice and installation with small bend, then connection is achieved, but the probability of damage increases compared to single mode optical fiber
Solution Approach 1:
The patent provides beforehand cushioning by designing a multi-layer cladding structure where the second cladding region (trench part) with lower refractive index acts as a protective barrier. This structural cushioning prevents stress concentration and crack propagation during installation and handling, reducing damage probability while maintaining ease of installation through standard fusion splicing procedures.
3Ease of operation
If a multimode optical fiber is bent during installation, then installation flexibility is improved, but bending loss increases unavoidably
Solution Approach 1:
The cladding structure is segmented into multiple regions with different refractive indices. The second cladding region (trench part) with lower refractive index acts as a stress-relief zone that reduces the impact of bending on the core region, thereby minimizing bending loss while maintaining installation flexibility.
Solution Approach 2:
By creating a localized low refractive index trench part in the second cladding region, the patent provides local quality enhancement that specifically addresses bending loss. This localized structural modification allows the fiber to maintain flexibility for installation while the trench structure prevents excessive light leakage during bending, reducing energy loss.
4Reliability
If the refractive index profile is optimized to reduce group delay difference, then bandwidth is expanded, but the fiber becomes more sensitive to bending-induced transmission fluctuations
Solution Approach 1:
The patent segments the cladding into multiple functional regions, where the second cladding region (trench part) with lower refractive index serves as a buffer zone. This segmentation allows the core region to have an optimized refractive index profile for reduced group delay difference and expanded bandwidth, while the second cladding region simultaneously provides protection against bending-induced transmission fluctuations.
Solution Approach 2:
The patent applies local quality by creating a specific low refractive index trench part in the second cladding region. This localized structural feature with refractive index lower than both the core and first cladding regions simultaneously achieves two objectives: it reduces group delay difference to expand bandwidth while also reducing sensitivity to bending, thereby resolving the contradiction between bandwidth expansion and bending sensitivity.
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 achieves reduced group delay differences, inhibited failure probability, and minimized bending loss, thereby enabling wider bandwidth and improved reliability in multimode optical fibers for short-haul communication.
Implementation Method 1
a graded index (GI)-type multimode optical fiber having GI-type refractive index profile including a region in which the refractive index continuously decreases from the central axis in a radial direction
Implementation Method 2
the trench part has a refractive index that is lower than the refractive index of the cladding region, and offers, to the multimode optical fiber, resistance against fluctuation in the transmission properties caused by bending
Implementation Method 3
the coating member surrounding the core region has a refractive index that is higher than a minimum refractive index in the glass fiber
Data Source
AI summary
The present invention relates to a multimode optical fiber including a glass fiber, and a coating member provided on an outer periphery of the glass fiber. The glass fiber extends along a predetermined central axis, and includes at least a core region having a GI-type refractive index profile. The coating member has a refractive index that is higher than a minimum refractive index of the core region. According to this configuration, leakage of a higher-order mode with a large group delay difference to the coating member side is facilitated.