Optical Waveguide Taper Design for Low-Loss Fiber Coupling
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Solution Overview
Problem
The existing silicon rib type optical waveguides face significant coupling loss when connected to single mode fibers due to differences in principal mode sizes, and conventional spot-size converters often result in transmission losses and longer optical waveguide lengths.
Innovation Solution
The optical waveguide design incorporates a first rib with a taper part and a second rib with laminated layers, connected by a barrier layer, where the barrier layer's ends are wider than the rib ends, allowing for continuous mode conversion with reduced loss and eliminating the need for additional taper structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a barrier layer is introduced between the optical waveguide region and the spot size conversion function region, then the manufacturing process is simplified by allowing separate formation of regions, but transmission loss increases due to coupling to higher-order modes and reflection
Solution Approach 1:
The optical waveguide is divided into distinct regions: a first region with a first barrier layer for separate manufacturing, and a second region with a second barrier layer for spot size conversion. This segmentation allows independent formation of each region while minimizing interference between them, resolving the contradiction between ease of manufacture and transmission loss.
Solution Approach 2:
Taper structures are introduced as intermediary elements between the barrier layers and the optical waveguide regions. These tapers act as mediators that gradually transition the mode profile, reducing abrupt changes and minimizing coupling to higher-order modes and reflection, thus reducing transmission loss while maintaining the barrier layer's manufacturing advantages.
2Loss of energy
If taper structures are introduced before and behind the barrier layer to suppress transmission loss, then transmission loss is reduced, but the optical waveguide length increases
Solution Approach 1:
Taper structures are placed only at specific locations where mode transition is needed, rather than throughout the entire waveguide. The first taper is positioned between the first barrier layer and the optical waveguide, and the second taper is positioned between the second barrier layer and the optical waveguide. This localized approach reduces transmission loss while minimizing the overall length increase.
Solution Approach 2:
The tapers are designed with optimized geometries in multiple dimensions, creating gradual mode transitions through three-dimensional shape variations. This allows effective mode conversion and loss suppression without requiring excessive length in the one-dimensional propagation direction.
3Loss of energy
If the principal mode size of the rib type optical waveguide is made large to reduce coupling loss with single mode fiber, then coupling loss is reduced, but the waveguide structure becomes more complex and longer
Solution Approach 1:
The spot size conversion function is pre-formed in the second region with a core layer that gradually widens from the barrier layer toward the optical fiber connection point. This preliminary action prepares the waveguide structure in advance to match the larger mode size of single mode fibers, reducing coupling loss without requiring complex additional components.
Solution Approach 2:
The second barrier layer and core layer structure serves multiple functions: it acts as a barrier to prevent mode coupling, provides a gradual spot size conversion function, and enables efficient coupling with single mode fibers. This multi-functionality reduces the need for separate components, simplifying the overall device while achieving the desired coupling loss reduction.
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
This design reduces transmission loss and coupling loss, suppresses polarization-dependent loss, and shortens the optical waveguide length, enhancing the efficiency and cost-effectiveness of the manufacturing process.
Implementation Method 1
the first rib including a first taper part having a width widening from a first end in the one side to a second end connected with the barrier layer
Implementation Method 2
a barrier layer being connected between the first rib and the second rib
Implementation Method 3
the second rib including a first layer and a second layer laminated on a face of the slab layer in turn
Data Source
AI summary
An optical waveguide of the present invention is an optical waveguide having a first rib and a second rib being provided on a slab layer along one direction from one side to the other side and a barrier layer being connected between said first rib and said second rib, in which: the first rib includes a first taper part having a width widening from a first end in said one side to a second end connected with said barrier layer; and the second rib includes a first layer and a second layer laminated on a face of said slab layer in turn.