Transmitter Optical Subassembly Impedance Element High Frequency Noise
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Solution Overview
Problem
Existing EA modulator integrated DFB lasers are affected by high frequency voltage components, which deteriorate the optical characteristics of the laser portion due to common electrodes for both the laser and modulation portions, leading to potential degradation in output performance.
Innovation Solution
A transmitter optical subassembly with a modulator integrated laser and an impedance element having self-resonant characteristics, where the impedance element is connected in series to minimize the impact of high frequency components, and the laser portion exhibits optimal emission intensity at the relaxation oscillation frequency, distinct from the self-resonant frequency by 10% or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a common electrode is used for both laser portion and modulation portion, then device complexity is reduced and ease of manufacture is improved, but high frequency voltage components from the modulation portion affect the laser portion and deteriorate optical characteristics
Solution Approach 1:
An impedance element is introduced as an intermediary component between the common electrode and the laser portion. This impedance element selectively blocks high frequency voltage components while allowing direct current to pass through, thereby protecting the laser portion from harmful high frequency interference while maintaining the simplicity of the common electrode structure
Solution Approach 2:
The impedance element's electrical characteristics are specifically designed to have different impedance values at different frequencies. By changing the impedance parameter based on frequency, the element allows direct current to flow freely to the laser portion while blocking high frequency voltage components that would otherwise deteriorate optical characteristics
2Object-affected harmful factors
If differential drive is applied to the modulation portion to diminish high frequency voltage amplitude, then the harmful impact on the laser portion is reduced, but the electrode potential change in the laser portion deteriorates optical characteristic
Solution Approach 1:
The impedance element serves as a mediator that directly addresses the high frequency voltage issue without requiring differential drive. It selectively filters high frequency components while maintaining stable electrode potential in the laser portion, avoiding the potential deterioration that would result from differential drive implementation
3Reliability
If an impedance element is added to block high frequency components, then optical characteristic is improved, but device complexity increases
Solution Approach 1:
A single impedance element is introduced as a simple intermediary component connected in series with the common electrode. This minimal addition provides effective high frequency filtering without significantly increasing device complexity, as the element integrates smoothly into the existing electrode structure
Solution Approach 2:
The impedance element is designed with specific electrical parameters (inductance and capacitance values) that create a self-resonant frequency matching the relaxation oscillation frequency of the laser. This parameter optimization allows effective high frequency blocking while maintaining a simple device structure with minimal additional components
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 effectively minimizes the impact of high frequency voltage components on the laser portion, maintaining optimal emission intensity and improving the quality of digital signals by reducing alternate current flow through the impedance element's self-resonant frequency.
Implementation Method 1
an impedance element with inductance and capacitance connected in parallel, the impedance element having a self-resonant characteristic exhibiting the highest impedance at a self-resonant frequency
Implementation Method 2
The impedance element is connected in series to the first electrode to minimize a flow of an alternate current
Implementation Method 3
a modulation portion for modulating the light by an electric field absorption effect
Data Source
AI summary
A modulator integrated laser has a laser portion for emitting light and a modulation portion for modulating the light by an electric field absorption effect. The modulator integrated laser has a semiconductor substrate of a conductivity type in which the laser portion and the modulation portion are integrated. An impedance element with inductance and capacitance connected in parallel. The impedance element has a self-resonant characteristic exhibiting the highest impedance at a self-resonant frequency. The laser portion has first and second electrodes for a direct current voltage to be applied therebetween. The modulation portion has third and fourth electrodes for an alternate current voltage to be applied therebetween. The second electrode and the fourth electrode are electrically connected to each other through the semiconductor substrate. The impedance element is connected in series to the first electrode to minimize a flow of an alternate current.