Tapered Mode-Selective Fiber Coupler for Low-Loss LP01/LP11 Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing mode-division multiplexing technologies face challenges with high multiplexing losses, narrow operating bandwidths, and complex designs in all-fiber mode-selective couplers, making them impractical for efficient mode multiplexing and demultiplexing.
Innovation Solution
A mode-selective optical fiber coupler design featuring tapered propagation waveguides with specific core and cladding configurations, optimized for low loss and cross-talk, allowing efficient separation and transmission of LP01 and LP11 modes within a wide spectral band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If free-space optics with bulk optics are used for coupling and beam splitting/combining, then mode multiplexing/demultiplexing can be implemented, but multiplexing losses are high making it impractical
Solution Approach 1:
The patent replaces free-space bulk optical systems with an all-fiber mode-selective coupler design. The fiber coupler uses evanescent field coupling between tapered fiber cores to achieve mode multiplexing/demultiplexing, eliminating the need for mechanical beam splitters and couplers in free space, thereby reducing multiplexing losses and improving practical implementability
Solution Approach 2:
The patent employs tapered fiber structures where the core diameter and separation distance vary along the length of the coupler. This parameter change enables adiabatic mode transformation and selective coupling between different modes (LP01, LP11, etc.), achieving low-loss mode multiplexing while maintaining a practical all-fiber configuration
2Loss of energy
If all-fiber mode-selective couplers are used to reduce multiplexing losses, then coupling efficiency improves, but operating bandwidth becomes narrow and design complexity increases
Solution Approach 1:
The patent uses dynamically varying parameters along the fiber coupler length, specifically the tapered core diameter and core separation distance. This dynamic structure enables the coupler to maintain low coupling losses across a broader spectral bandwidth by adapting the evanescent field overlap conditions for different wavelengths and modes throughout the coupler length
3Loss of energy
If all-fiber mode-selective couplers are designed to reduce multiplexing losses, then coupling efficiency improves, but design complexity increases making them difficult to manufacture
Solution Approach 1:
The patent divides the fiber coupler into distinct functional segments: input regions, tapered coupling regions with specific core separations for different modes, and output regions. Each segment is optimized for its specific function (mode excitation, mode coupling, mode separation), which simplifies the overall design process and manufacturing by allowing modular optimization of each section independently
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 coupler achieves low loss and cross-talk levels, enabling efficient mode multiplexing and demultiplexing with LP01 loss less than 1.0 dB and LP11 loss less than 1.5 dB across a 100 nm bandwidth from 800 nm to 950 nm, supporting high-capacity optical data transmission.
Implementation Method 1
a first propagation waveguide extending from the input face to the output face, the first propagation waveguide comprising a first core, a first inner cladding concentric with the first core, and a first outer cladding surrounding the first inner cladding... a second propagation waveguide extending from the input face to the output face, the second propagation waveguide comprising a second core, a second inner cladding concentric with the second core, and a second outer cladding surrounding the second inner cladding
Implementation Method 2
the first propagation waveguide and the second propagation waveguide are tapered from the input face and the output face to a midpoint of the coupler such that a tapered width dimension Wt of the coupler at the midpoint is less than a full width dimension Wf of the coupler at the input face and at the output face
Data Source
AI summary
In embodiments, a mode selective optical fiber coupler may include a first propagation waveguide and a second propagation waveguide joined along a coupling length L. The first propagation waveguide and the second propagation waveguide may be tapered from an input face and an output face of the coupler to a midpoint of the coupler. An LP01 mode of an optical signal with a wavelength of 800-950 nm coupled into the first propagation waveguide propagates through the first propagation waveguide and is emitted from the first propagation waveguide. An LP01 loss of the coupler at the output face is less than 1.0 dB. An LP11 mode of the optical signal coupled into the first propagation waveguide is cross-coupled to the second propagation waveguide and is emitted from the second propagation waveguide. An LP11 loss of the coupler at the output face is less than 1.5 dB.