Optical Modulator Anti-Reflection Coating Stray Light Suppression
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Solution Overview
Problem
Stray light reflection in optical modulators lowers measurement accuracy in optical communication systems, particularly in Mach-Zehnder type modulators, due to the arrangement of input and output ports and waveguides, which affects the evaluation of extinction characteristics.
Innovation Solution
An optical modulator with a substrate having opposing faces, where one face has an anti-reflection coating to suppress stray light reflection, and an optical measurement apparatus using a multi-mode optical fiber with a larger core diameter and strategically positioned anti-reflection coatings to reduce stray light interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If anti-reflection coating is added to suppress stray light reflection, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The harmful reflection is extracted and eliminated by applying anti-reflection coating specifically on the second face (opposite to the first face) and on the waveguide surfaces. This targeted extraction of the reflection problem from specific locations resolves the contradiction by improving measurement precision through selective suppression of stray light without adding complex structures throughout the entire device.
Solution Approach 2:
The anti-reflection coating acts as an intermediary layer between the light and the substrate/waveguide surfaces. This intermediary prevents the harmful reflection from occurring at the interface, thereby improving measurement accuracy while maintaining the simplicity of the basic modulator structure.
2Volume of moving object
If waveguide is bent to arrange input and output ports on the same face for miniaturization, then device size is reduced, but stray light reflection increases
Solution Approach 1:
The patent accepts the bent waveguide configuration for miniaturization but converts the harmful effect of increased reflection into a manageable issue by applying anti-reflection coating on the second face and waveguide surfaces. The harmful reflection is transformed into a controlled parameter that can be suppressed through targeted coating application.
Solution Approach 2:
Instead of changing the overall bent waveguide structure, the patent applies local quality improvement by adding anti-reflection coating specifically on the second face and waveguide surfaces where reflection occurs. This localized treatment suppresses stray light while maintaining the compact bent configuration.
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 anti-reflection coatings effectively suppress stray light reflection, improving the measurement accuracy of optical modulator characteristics such as extinction characteristics by minimizing light contamination from stray reflections.
Implementation Method 1
a first anti-reflection coating provided on the second face
Data Source
AI summary
An optical modulator includes a substrate having a first face and a second face; an input port provided on the first face; a first waveguide provided on the substrate, the waveguide being connected to the input port; a first coupler provided on the substrate, the first coupler being optically connected to the first waveguide; an output port provided on the first face of the substrate, the output port being optically connected to the first coupler; and a first anti-reflection coating provided on the second face. The first face and the second face are arranged along a first direction. The first face and the second face extend in a direction intersecting the first direction. The first coupler extends in the first direction.