Optical Transmitter Module Impedance Matching
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Solution Overview
Problem
Optical transmitter modules face challenges in achieving uniform high-frequency characteristics and expanded modulation bandwidth, particularly in maintaining high-frequency signal modulation for efficient data transmission.
Innovation Solution
The optical transmitter module incorporates an electro-absorption modulated laser (EML) chip with a ground structure, impedance matching resistor, and bonding wires, along with a capacitor to block direct current, ensuring uniform high-frequency characteristics and efficient signal modulation by optimizing the layout and materials used, such as Cu, W, or SUS for the ground plate and Au coatings, and using SMD-type resistors and capacitors for impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the modulation bandwidth is expanded to high frequency range to improve transmission speed, then the data transmission efficiency is improved, but the uniformity of high-frequency characteristics deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the impedance value of the matching resistor (set to 50Ω to match standard transmission line impedance) and adjusting the physical dimensions of the ground structure and bonding wires. These parameter adjustments ensure uniform high-frequency characteristics across the expanded bandwidth range, resolving the contradiction between transmission speed and characteristic uniformity.
Solution Approach 2:
The patent introduces an impedance matching resistor as an intermediary component between the EML chip and the transmission line. This resistor acts as a mediator to match impedance levels, reducing reflections and standing waves that would otherwise cause non-uniform high-frequency characteristics, thereby maintaining reliability while enabling high-speed transmission.
2Reliability
If an impedance matching resistor is added to improve high-frequency characteristics, then the signal quality is improved, but the device complexity increases
Solution Approach 1:
The patent merges the impedance matching resistor with the ground structure by electrically connecting the resistor to the ground layer through bonding wires. This integration approach combines multiple functions (impedance matching, grounding, and signal reference) into a unified structure, reducing overall device complexity while maintaining improved high-frequency characteristics.
Solution Approach 2:
The ground structure in the patent serves multiple functions simultaneously: it provides the reference potential for signal transmission, establishes proper impedance matching through the connected resistor, and acts as a return path for high-frequency signals. This multi-functionality reduces the need for separate components, thereby reducing device complexity while maintaining reliability.
3Reliability
If a ground structure with ground plate and supports is used to improve high-frequency characteristics, then the signal stability is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent segments the ground structure into distinct functional components: a ground plate for signal reference, support structures for mechanical stability, and bonding wires for electrical connection. This segmentation allows each component to be optimized and manufactured separately using standard processes, reducing overall manufacturing complexity while maintaining signal stability through proper assembly.
Solution Approach 2:
The ground plate and ground layer are designed to maintain equipotential conditions across the device by providing a continuous low-impedance reference plane. This equipotential design stabilizes high-frequency signals by eliminating potential differences that would cause signal distortion, while the modular construction keeps manufacturing feasible through standard PCB and wire bonding techniques.
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 enhances the optical transmitter module's high-frequency characteristics, prevents degradation of optical output and wavelength stability, and reduces manufacturing costs by using SMD-type components, thereby improving data transmission efficiency.
Implementation Method 1
an electro-absorption modulated laser (EML) chip disposed on the ground layer to generate an optical signal
Implementation Method 2
a capacitor disposed on the ground structure and electrically connected to the ground structure... wherein the capacitor may block a direct current (DC) flowing through the matching resistor
Data Source
AI summary
Provided is an optical transmitter module. The optical transmitter module includes a substrate, a ground layer disposed on the substrate, an electro-absorption modulated laser (EML) chip disposed on the ground layer to generate an modulated optical signal, a ground structure disposed on the EML chip and electrically connected to the ground layer, a matching resistor disposed on the ground structure, and a first bonding wire disposed between the EML chip and the matching resistor to electrically connect the EML chip to the matching resistor.