Graded-Index Multimode Fiber for VCSEL Dispersion Control
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Solution Overview
Problem
Current multimode fibers are limited in supporting high-speed communication over long distances due to dispersion effects, especially when used with high-modulation-rate signals from Vertical Cavity Surface Emitting Lasers (VCSELs), as they have a low bandwidth-length product and require tight alignment, increasing costs and complexity.
Innovation Solution
Optimized graded-index multimode fibers with a specific core diameter and numerical aperture product, supporting a lower number of spatial modes, allowing for extended propagation distances and relaxed alignment tolerances, thereby enabling cost-effective high-speed VCSEL-based communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional multimode fiber is used to support high-modulation-rate signals from VCSELs, then multi-mode signals can be transmitted, but dispersion effects limit propagation distance and bandwidth-length product
Solution Approach 1:
The patent applies parameter changes by optimizing the graded-index profile of the multimode fiber, specifically controlling the refractive index variation across the core to minimize modal dispersion. By adjusting the index gradient parameter g and core diameter, the fiber achieves extended bandwidth-length product while maintaining compatibility with VCSEL modulation rates, thereby resolving the contradiction between high-speed transmission and long-distance propagation.
2Productivity
If traditional multimode fiber is used for high-speed communication, then multi-mode signals are supported, but alignment tolerances are tight, increasing cost and complexity
Solution Approach 1:
The patent changes the fiber parameters including core diameter (25-50 micrometers) and numerical aperture to achieve relaxed alignment tolerances while maintaining high bandwidth-length product. By optimizing these geometric parameters, the system achieves both high-speed communication capability and reduced alignment complexity, resolving the contradiction between productivity and device complexity.
3Length of stationary object
If single-mode fiber is used, then extended propagation distances are supported, but it does not support multi-mode signals from high-speed VCSELs
Solution Approach 1:
The patent applies local quality by creating a graded-index structure where the refractive index varies locally across the fiber core. This allows the fiber to support multiple propagation modes like multimode fiber while maintaining low dispersion characteristics similar to single-mode fiber, thereby achieving both extended propagation distance and multi-mode signal compatibility.
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 fibers support high data modulation rates over distances exceeding traditional multimode fibers by a factor of 10, reducing costs and complexity by allowing relaxed alignment tolerances and improved bandwidth-length products, while minimizing dispersion issues.
Implementation Method 1
Optical fibers may be used for communication of signals
Implementation Method 2
Optimized graded-index multimode fibers with a specific core diameter and numerical aperture product
Data Source
AI summary
Examples include generating a signal using a modulatable source. The signal may be propagated using a multi-mode fiber to receive the signal from the modulatable source. The fiber has a diameter d and a far-field divergence angle associated with the propagated signal that corresponds to a product of the diameter (d) and the far-field divergence angle. The product may be substantially between 1 micron radian and 4 micron radian. In some examples, the propagated signal may be received at a receiver from the multi-mode fiber.