Segmented Optical Modulator High Frequency Line Impedance Matching
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Solution Overview
Problem
Optical modulators face challenges in efficiently inputting high frequency electrical signals due to impedance mismatching, leading to waveform deterioration and reduced modulation efficiency, particularly in traveling wave electrode type modulators where impedance matching is difficult to achieve.
Innovation Solution
The optical modulator incorporates high frequency lines with segments having different characteristic impedances and propagation constants, allowing for efficient input of high frequency signals and minimizing reflection, achieved through varying the width, thickness, or dielectric constant of the signal line and inter-electrode distance between segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the cross-sectional area of the wiring electrode is increased to reduce wiring resistance and propagation loss, then propagation loss is reduced, but impedance and phase velocity change causing impedance mismatching and velocity mismatching
Solution Approach 1:
The optical modulation high frequency line is divided into multiple segments with different cross-sectional areas. Each segment is designed to have a specific impedance value, creating a segmented structure that transitions smoothly from the driver IC to the optical modulator. This segmentation allows the line to achieve both low propagation loss and proper impedance matching by having each segment contribute differently to the overall signal transmission.
Solution Approach 2:
Different segments of the optical modulation high frequency line are designed with different local properties (cross-sectional areas, impedances). The first segment has a different cross-sectional area than the second segment, creating local variations in impedance along the transmission line. This local quality variation allows each segment to be optimized for its specific function while maintaining overall system performance.
2Loss of energy
If the cross-sectional area of the wiring electrode is increased to reduce propagation loss, then propagation loss is reduced, but phase velocity increases causing velocity mismatching
Solution Approach 1:
The transmission line is segmented into multiple sections with different cross-sectional areas and impedance values. This segmentation creates a distributed impedance structure that controls phase velocity at different locations along the line. By carefully designing the impedance progression across segments, the patent achieves both low propagation loss and controlled phase velocity to prevent velocity mismatching with the optical modulator.
Solution Approach 2:
The patent changes the physical parameters (cross-sectional area, impedance) of the transmission line segments to optimize both propagation loss and phase velocity. By varying these parameters along the transmission line rather than using uniform structures, the design achieves a balance between minimizing energy loss and controlling signal speed to match the optical modulator's requirements.
3Adaptability or versatility
If a traveling wave electrode is used to achieve broadband operation, then electrooptic band is widened, but impedance matching and velocity matching become difficult to achieve
Solution Approach 1:
The traveling wave electrode structure is enhanced by segmenting the optical modulation high frequency line into multiple sections with different impedance values. This segmentation allows the broadband traveling wave electrode to maintain impedance matching across a wider frequency range. Each segment can be designed to contribute to both broadband operation and proper impedance matching, resolving the contradiction between these two requirements.
Solution Approach 2:
The patent creates a dynamic impedance structure along the transmission line through segmentation, where the impedance varies continuously or in steps from the driver IC to the optical modulator. This dynamic impedance progression allows the system to adapt to different operating conditions and maintain both broadband operation and good impedance matching simultaneously, rather than using a static uniform structure.
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 enhances the modulation efficiency and extends the electrooptic band, enabling high-speed and large-capacity optical communication with reduced waveform deterioration and improved impedance matching.
Implementation Method 1
applies modulation to an optical signal due to an electrooptic (EO) effect in the optical modulation high frequency line 104
Data Source
AI summary
Provided is an optical modulator having an optical modulation high frequency line through which a high frequency electrical signal can be efficiently input to an optical modulation region and which is in a broadband. High frequency lines of an optical modulator, that is, an input high frequency line, an optical modulation high frequency line, and an output high frequency line have a line configuration in which each of the input high frequency line and the output high frequency line is divided into a plurality of segments, and adjacent segments of the plurality of the segments have different characteristic impedances and propagation constants. The input high frequency line and the output high frequency line may be implemented by changing a width or a thickness of a signal electrode formed on a dielectric forming a micro-strip line between adjacent segments. The characteristic impedances and the propagation constants may be changed by changing a dielectric constant of the dielectric instead of changing the width or the thickness of the signal electrode.