Optoelectronic Module Interconnect Structure for Crosstalk Reduction
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Solution Overview
Problem
High-speed, high-density interconnect structures for optoelectronic modules suffer from significant cross-talk and signal integrity issues due to electromagnetic coupling between closely spaced signal lines, particularly in high-frequency applications like 25 Gbps data transmission systems.
Innovation Solution
The interconnect structure features signal and ground leads with significantly lower impedance for the ground leads compared to the signal leads, where the ground lines are at least five times wider and connected directly to a ground plane layer, reducing the impedance of the signal return path and minimizing cross-talk by guiding the return signal primarily through the ground lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If signal lines are closely spaced to achieve high-density interconnection, then the number of channels increases, but cross-talk between signal lines increases significantly
Solution Approach 1:
A ground line is introduced as an intermediary between adjacent signal lines to shield them from each other. This ground line acts as a mediator that redirects electromagnetic fields and return currents, preventing direct coupling between signal lines and thereby reducing cross-talk while allowing closely spaced signal lines for high-density interconnection
Solution Approach 2:
The impedance of the ground line is specifically designed to be lower than that of the signal lines. By changing the impedance parameter of the ground line (making it at least five times wider than signal lines), the return current is preferentially guided through the ground line rather than coupling to adjacent signal lines, thus reducing cross-talk in high-density configurations
2Area of stationary object
If signal lines are closely spaced to achieve high-density interconnection, then area utilization improves, but signal integrity deteriorates due to electromagnetic coupling
Solution Approach 1:
The ground line serves as a protective intermediary between closely spaced signal lines, shielding them from electromagnetic coupling. This allows the signal lines to be placed closer together for better area utilization while the ground line maintains signal integrity by redirecting electromagnetic fields and return currents away from adjacent signal lines
Solution Approach 2:
By changing the width parameter of the ground line to be at least five times wider than the signal lines, its impedance is reduced, creating a preferred path for return currents. This parameter change ensures that even when signal lines are closely spaced for area efficiency, the return currents flow through the low-impedance ground line rather than coupling to neighboring signal lines, preserving signal integrity
3Device complexity
If conventional interconnect structures are used, then device complexity is low, but cross-talk levels are high causing signal quality degradation
Solution Approach 1:
A ground line is introduced as a shielding intermediary between adjacent signal lines. This adds minimal structural complexity - essentially one additional conductive element per signal pair - but effectively reduces cross-talk by redirecting electromagnetic fields and return currents through the ground line, improving signal quality without significantly increasing device complexity
Solution Approach 2:
The ground line is designed with specific width parameters (at least five times wider than signal lines) to achieve lower impedance. This parameter change creates a preferential path for return currents, reducing cross-talk levels and improving signal quality while maintaining relatively simple interconnect structure complexity
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 configuration reduces cross-talk levels, resulting in improved signal integrity with less jitter, allowing for longer transmission links and better signal quality, as demonstrated by reduced s-parameter coupling coefficients and EYE diagram improvements.
Implementation Method 1
High-speed, high-density interconnect structures for optoelectronic modules suffer from significant cross-talk and signal integrity issues due to electromagnetic coupling between closely spaced signal lines
Data Source
AI summary
An optoelectronic module is provide and includes an electronic unit, an optical unit, and an interconnect structure. The electronic unit is capable of outputting and/or receiving electric signals, while the optical unit is capable of converting the electric signals into optical signals. The interconnect structure connects the electronic unit and the optical unit, and includes an electrically conducting substrate and a pair of transmission leads connecting electronic unit and the optical unit. The pair of transmission leads includes a signal lead and a ground lead having lower impedance than the signal lead.