Optical Modulator Terminator High-Frequency Reflection Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In optical modulator modules, reflection characteristics deteriorate in high frequency regions above 10 GHz due to strong capacitance and inductance of the Mach-Zehnder modulator chip, making it difficult to match with the terminator, and open collector type driver ICs are sensitive to reflection, leading to ripples in frequency response.
Innovation Solution
The optical modulator module incorporates a terminator with additional capacitance components, including signal electrodes, midpoint electrodes, and GND electrodes on a substrate, along with resistors, to increase the number of capacitance components, optimizing the electrode pattern for improved matching and reduced reflection at high frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional terminator with resistors is used to match the MZ modulator chip, then low frequency reflection characteristics (10 GHz or less) are sufficiently reduced, but high frequency reflection characteristics (above 10 GHz) deteriorate due to strong capacitance and inductance of the chip
Solution Approach 1:
The terminator is divided into multiple segments: signal electrodes, midpoint electrodes, and GND electrodes arranged in a specific pattern. This segmentation creates multiple capacitance components distributed across the terminator structure, enabling effective impedance matching across a broader frequency range including high frequencies above 10 GHz
Solution Approach 2:
Different regions of the terminator are designed with different electrode configurations and capacitance values. The signal electrodes, midpoint electrodes, and GND electrodes are positioned to create localized capacitance variations that collectively improve matching characteristics across the entire frequency spectrum
2Use of energy by moving object
If open collector type driver IC is used to reduce power consumption, then energy efficiency is improved, but the system becomes more sensitive to reflection causing ripples in frequency response
Solution Approach 1:
The terminator structure is designed in advance with specific electrode patterns and capacitance distributions to preemptively counteract reflection effects. By establishing proper impedance matching before signals reach the driver IC, the system prevents reflection-induced ripples from affecting the open collector type driver IC's frequency response
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 design effectively suppresses reflection characteristics even at frequencies above 10 GHz, improving the E/O response characteristics by increasing the number of capacitance components in the terminator, thereby reducing ripples in the frequency response.
Implementation Method 1
increase the number of capacitance components, thereby suppressing reflection at the terminator
Implementation Method 2
reflection at the terminator is suppressed
Data Source
AI summary
In a terminator, a midpoint electrode is provided between a first signal electrode and a second signal electrode, a first resistor is connected between the first signal electrode and the midpoint electrode, a second resistor is connected between the second signal electrode and the midpoint electrode, a first GND electrode is provided on a side opposite to the side where the first resistor is provided with the first signal electrode interposed therebetween, a second GND electrode is provided on the side opposite to the side where the second resistor is provided with the second signal electrode interposed therebetween, and capacitances in the terminator are formed between the first signal electrode and the midpoint electrode, between the second signal electrode and the midpoint electrode, between the first signal electrode and the first GND electrode, and between the second signal electrode and the second GND electrode.