Optical Modulator Asymmetrical Ground Patterns Reduce Crosstalk
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Solution Overview
Problem
In optical modulators, leaked microwaves from component mounting portions on the relay substrate cause noise and crosstalk between high-frequency electrical signals, affecting the modulation characteristics, especially in high-frequency applications like DP-QPSK modulation.
Innovation Solution
The optical modulator design incorporates asymmetrical ground conductor patterns around component mounting areas on the relay substrate, with varying separation distances, widths, and presence/absence of vias to redirect and reduce the intensity of leaked microwaves, thereby minimizing crosstalk between signal conductor patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical circuit elements are mounted on the relay substrate to improve high-frequency characteristics, then the modulation performance is improved, but leaked microwaves cause noise and crosstalk between signal lines
Solution Approach 1:
The patent applies asymmetry by configuring ground conductor patterns with different shapes, sizes, and positions on either side of the component mounting portion. Specifically, the ground conductor pattern on the first side has a different configuration than the ground conductor pattern on the second side, creating an asymmetric microwave leakage path that directs leaked microwaves away from adjacent signal lines, thereby reducing crosstalk while maintaining modulation performance
Solution Approach 2:
The patent converts the harmful effect of microwave leakage into a beneficial outcome by strategically designing the asymmetric ground conductor patterns to redirect leaked microwaves toward safe discharge paths. The leaked microwaves that would normally cause noise and crosstalk are instead channeled through the asymmetric ground structures to dissipate in controlled directions, transforming a harmful phenomenon into a managed design feature
2Reliability
If component mounting portions are provided on the relay substrate for mounting electrical circuit elements, then high-frequency characteristics are improved, but the structure becomes more complex
Solution Approach 1:
The patent applies local quality by providing asymmetric ground conductor patterns specifically at the component mounting portions where electrical circuit elements are mounted, while other areas of the relay substrate maintain standard symmetric configurations. This localized application of asymmetry targets only the specific regions where microwave leakage occurs, improving high-frequency characteristics without unnecessarily complicating the entire relay substrate structure
Data Source
AI summary
An optical modulator includes a relay substrate having signal conductor patterns that connect signal input terminals and signal electrodes of an optical modulation element and ground conductor patterns, and a housing, in which the signal conductor pattern includes a component mounting portion including an electrical circuit element. Two ground conductor patterns sandwiching the signal conductor pattern are formed in an asymmetrical shape in a plan view within a component mounting area having a square shape in the plan view centered on the component mounting portion. A direction of a side of the component mounting area having the square shape is same as the extending direction of the signal conductor pattern and a length of a side of the component mounting area is equal to a distance from a center of the component mounting portion to a portion on an adjacent signal conductor pattern closest to the center.