Optical Module Ground Layout for Low-EMI Signal Transmission
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Solution Overview
Problem
Existing optical modules face challenges in efficiently transmitting high-frequency data signals over long distances while minimizing electromagnetic interference and signal crosstalk, which affects communication rates and optoelectronic performance.
Innovation Solution
The optical module incorporates a circuit board and spacer design with specific ground line connections, including GSG transmission mode, multiple connection lines, and ground holes to reduce parasitic inductance and electromagnetic interference, ensuring efficient signal transmission and improved communication rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional single ground line connection is used, then device complexity is reduced, but electromagnetic interference and signal crosstalk increase
Solution Approach 1:
The ground connection is segmented into multiple independent ground lines (first ground line, second ground line, third ground line) instead of using a single ground connection. Each ground line provides a separate return path for different signals, reducing electromagnetic interference and signal crosstalk between adjacent signals.
Solution Approach 2:
The second ground line acts as an intermediary shielding ground between the first ground line and the third ground line. This intermediate ground line blocks electromagnetic field coupling between adjacent signal-return paths, reducing crosstalk while maintaining a manageable structural complexity.
2Ease of manufacture
If longer connection lines are used, then ease of manufacture is improved, but parasitic inductance increases
Solution Approach 1:
Different connection lines are optimized with locally appropriate characteristics. The first connection line connecting the anode to the signal line is kept short to minimize inductance for high-frequency signals. The second and third connection lines connecting ground lines are routed to minimize loop areas, reducing parasitic inductance locally where it matters most for signal integrity.
Solution Approach 2:
The connection lines are arranged in a three-dimensional layout on the circuit board, utilizing vertical spacing and strategic routing paths. By changing the spatial arrangement rather than simply extending line lengths, the design achieves manufacturability while controlling parasitic inductance through minimized loop areas and optimized geometries.
3Reliability
If multiple ground lines with multiple connections are used, then signal transmission quality is improved, but device complexity increases
Solution Approach 1:
Multiple ground lines (first, second, and third ground lines) are merged and connected together at multiple points on the circuit board, forming a unified ground reference system. This merging approach provides multiple low-impedance return paths for signals while maintaining a single ground potential reference, improving signal quality without creating isolated ground systems that would increase complexity.
Solution Approach 2:
The multiple ground lines are connected through multiple ground connections to maintain equipotential conditions across the ground system. By ensuring all ground lines are at the same potential through multiple connection points, the design achieves low-impedance return paths and reduced ground loops, improving signal transmission while avoiding the complexity of differential ground systems.
4Reliability
If shorter connection lines are used, then parasitic inductance is reduced, but ease of manufacture decreases
Solution Approach 1:
The connection line design incorporates dynamic routing strategies that adapt to the specific layout requirements. Rather than using fixed rigid paths, the design allows for flexible routing that can be optimized during manufacturing for both length and geometry. This dynamic approach enables shorter effective electrical paths while maintaining manufacturability through standard PCB routing practices and acceptable manufacturing tolerances.
Data Source
AI summary
An optical module includes a circuit board and a light emitting assembly. The circuit board includes a first circuit board ground line, a second circuit board ground line and a circuit board signal line. The light emitting assembly is connected to the circuit board, and the light emitting assembly includes a spacer and a laser chip. The spacer includes a first spacer ground line, a second spacer ground line and a spacer signal line. The first spacer ground line is connected to the second spacer ground line through a fourth connection line; or the first spacer ground line is connected to the second circuit board ground line through a fifth connection line; or the second spacer ground line is connected to the first circuit board ground line through a sixth connection line; or the first circuit board ground line is connected to the second circuit board ground line through a seventh connection line.