Mode Converter for Uniform Single-Mode to Multi-Mode Signal Coupling
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Solution Overview
Problem
Existing mode converters face challenges in accurately aligning optical fibers and uniformly coupling power from single-mode to multi-mode fibers, leading to high excess noise in optical communication networks, which restricts the number of subscribers in code division multiple access systems.
Innovation Solution
A mode converter comprising a single-mode optical waveguide, a mode scrambler with controlled mechanical protrusions and depressions, and a multi-mode optical waveguide with a multi-step or multi-graded refractive index distribution, integrated on a single substrate and connected via fusion splicing, to uniformly couple power from single-mode to multi-mode signals, reducing excess noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-mode optical fiber is directly connected to a multi-mode optical fiber through core axial displacement, then mode conversion occurs, but accurate alignment of optical fiber axes is very difficult to achieve
Solution Approach 1:
The patent introduces a mode converter as an intermediary device between single-mode and multi-mode optical fibers. This mode converter includes a single-mode optical waveguide, mode scrambler, and multi-mode optical waveguide that work together to facilitate mode conversion without requiring direct alignment between the single-mode and multi-mode fibers, thus solving the alignment precision problem
2Manufacturing precision
If optical fibers are cut at specific angles to improve mode coupling, then mode conversion efficiency improves, but the cutting and connecting processes become difficult to carry out
Solution Approach 1:
The patent replaces the mechanical cutting and angle-adjustment process with an integrated mode converter structure. Instead of physically cutting fibers at specific angles and manually aligning them, the mode converter provides a pre-configured structure with optimized geometry that achieves efficient mode coupling through its design, eliminating complex mechanical processes
3Reliability
If a tapered hollow optical fiber is used to convert single mode to multi-mode, then modal dispersion is reduced, but uniform power coupling to each mode becomes difficult
Solution Approach 1:
The patent employs a mode scrambler with specific structural characteristics that create localized variations in the optical path. The mode scrambler includes elements that selectively interact with different modes to achieve uniform power distribution, applying different local modifications to different parts of the optical field to accomplish uniform coupling
4Productivity
If excess noise is reduced to maximize subscribers in optical code division multiple access, then network capacity increases, but requiring complex noise reduction techniques
Solution Approach 1:
The patent converts the harmful excess noise generated by mode beating into a beneficial effect by using the mode converter to distribute power uniformly across multiple modes. This uniform distribution causes the beating effects to occur at different frequencies and phases, transforming the concentrated harmful noise into dispersed, less problematic noise components
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 effectively reduces excess noise by over 20 dB in optical communication networks, allowing for a higher number of modes to be converted and maximizing the number of subscribers, while simplifying the manufacturing process and reducing connection losses.
Implementation Method 1
a mode scrambler that converts the single-mode optical signal output from the single-mode optical waveguide to a multi-mode optical signal and uniformly couples the optical power of the single-mode optical signal to each mode of the multi-mode optical signal
Implementation Method 2
a multi-mode optical waveguide that transmits the multi-mode optical signal output from the mode scrambler
Implementation Method 3
connected via fusion splicing
Data Source
AI summary
A single-to-multi mode converter and an optical code division multiple access system using the same. The mode converter includes first, second, and third optical waveguides. The first optical waveguide is formed of a single-mode optical fiber and outputs a single-mode optical signal. The second optical waveguide converts the single-mode optical signal output from the first optical waveguide to a multi-mode optical signal and allows the optical power of the single-mode optical signal to be coupled to each mode of the multi-mode optical signal. The third optical waveguide is formed of a multi-mode optical fiber and transmits the multi-mode optical signal output from the second optical waveguide.