Perturbed Curved Optical Surface for Back Reflection Reduction
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Solution Overview
Problem
In high-speed optical communications networks, there is a trade-off between forward optical coupling efficiency and back reflection, which increases relative intensity noise (RIN) due to mode mismatching between laser light sources and multimode optical fibers, and existing solutions like optical isolators or angled fiber launches are either ineffective or increase complexity and cost.
Innovation Solution
An optical coupling system with a curved optical surface and perturbations that modify the light beam's phase to match the spatial and angular distribution of the optical waveguide modes, reducing back reflection and improving mode matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional optical coupling methods are used, then forward optical coupling efficiency is achieved, but back reflection increases causing RIN degradation
Solution Approach 1:
The patent applies local quality by creating perturbations (local structural variations) on specific regions of the curved optical surface. These perturbations are strategically positioned to locally modify the phase of reflected light beams, causing them to diverge away from the laser source while maintaining overall coupling efficiency. This localized modification resolves the contradiction by addressing back reflection at specific points rather than requiring global system changes.
Solution Approach 2:
The patent utilizes a curved optical surface (spheroidal or aspherical) instead of a flat surface to couple light from the laser source to the optical fiber. This curvature enables better mode matching between the laser beam and fiber modes, improving forward coupling efficiency. The curved surface inherently directs reflected light away from the source, reducing back reflection, while the perturbations on this curved surface further optimize the reflection pattern to minimize RIN.
2Productivity
If mode matching is improved between laser light source and optical fiber, then forward optical coupling efficiency increases, but back reflection into the laser source also increases
Solution Approach 1:
The perturbations on the curved optical surface create local phase modifications that selectively affect reflected light paths. By positioning these perturbations at specific locations on the curved surface, the patent locally alters the reflection characteristics to prevent back reflection while preserving the overall mode-matched coupling geometry that provides high forward efficiency.
Solution Approach 2:
The patent changes the surface parameters of the optical coupling element by introducing controlled perturbations (variations in surface height, curvature, or refractive index) on the curved optical surface. These parameter changes modify the optical path of reflected light to divert it away from the laser source, while the base curved surface parameters are optimized for mode matching to maintain high forward coupling efficiency.
3Reliability
If optical isolator or angled fiber launch is used to reduce back reflection, then RIN is reduced, but device complexity and cost increase
Solution Approach 1:
The patent merges the functions of back reflection reduction and optical coupling into a single integrated curved optical surface with perturbations. Instead of using separate components like optical isolators or angled fiber launches, the invention combines mode-matching curvature and back-reflection-diverting perturbations in one element, thereby reducing device complexity and cost while achieving the desired RIN performance.
Solution Approach 2:
The curved optical surface with perturbations is designed to automatically divert back reflection away from the laser source through its inherent geometric and optical properties. The structure serves itself by using the reflected light's own path to redirect it away from the source, eliminating the need for additional active isolation components or complex angled alignment mechanisms.
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 system enhances forward optical coupling efficiency and reduces RIN by creating a complex light beam shape that matches the optical waveguide modes, minimizing back reflection and improving data transmission performance.
Implementation Method 1
Each perturbation has a localized refractive effect on a portion of the light beam that is incident on the curved optical surface
Data Source
AI summary
An optical coupling system and method are provided for coupling light from a light source into an optical waveguide that reduce back reflection of light onto the light source and provide controlled launch conditions that increase forward optical coupling efficiency. The optical coupling system comprises at least one curved optical surface having perturbations formed therein over at least a portion of the curved optical surface that intersects an optical pathway. The perturbations have a lateral width and a maximum height that are preselected to improve forward optical coupling efficiency and to decrease back reflection of the light beam from the optical waveguide end face onto the light source aperture. The perturbations improve forward optical coupling efficiency by creating a complex light beam shape that is preselected to match a spatial and angular distribution of a plurality of light modes of the optical waveguide.