Optical Modulator Signal Line Impedance Matching
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Solution Overview
Problem
In optical modulator modules with multiple optical modulation units, the longer electrical length of signal supply lines leads to deterioration of modulation characteristics, especially in high-frequency bands, and requires complex adjustments to maintain transmission quality for high-speed communication.
Innovation Solution
The optical modulator module employs signal supply lines with varying electrical lengths by either widening the cross-sectional area or increasing the length of specific parts of the signal supply lines, preventing propagation loss and improving modulation characteristics without the need for additional delay lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of optical modulation units is increased to support multi-level modulation and multi-wavelength communication, then the information transmission capacity is improved, but the electrical length of signal supply lines becomes longer causing deterioration of modulation characteristics
Solution Approach 1:
The patent applies local quality by making different parts of the signal supply lines have different cross-sectional areas. Specifically, portions of the signal supply lines are designed with varying widths to compensate for electrical length differences, allowing each line to have appropriate impedance characteristics despite different lengths. This enables multiple optical modulation units to operate with consistent signal quality regardless of their position in the package.
2Length of stationary object
If signal supply lines are made longer to reach distant optical modulation units, then all units can be connected, but signal attenuation increases especially in high-frequency bands
Solution Approach 1:
The patent changes physical parameters of the signal supply lines, specifically the cross-sectional area (width) of different portions. By varying the line width along their length, the electrical characteristics of each signal supply line are adjusted to compensate for length differences. This parameter modification allows longer lines to maintain signal strength comparable to shorter lines, reducing attenuation effects in high-frequency bands.
3Reliability
If delay lines are added to equalize signal arrival times, then modulation characteristics are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of adding uniform delay lines to all signal paths, the patent applies local quality by selectively varying the cross-sectional areas of specific portions of signal supply lines. This creates different electrical characteristics in different parts of the system, allowing timing synchronization to be achieved through the inherent properties of the signal lines themselves rather than through additional delay components.
Solution Approach 2:
The patent extracts the delay function from separate delay line components and integrates it directly into the signal supply lines themselves. By incorporating impedance-matching portions with different cross-sectional areas directly into the signal supply path, the delay and impedance matching functions are combined, eliminating the need for separate delay line components and reducing overall device complexity.
4Loss of time
If all signal supply lines are made to have the same electrical length, then timing synchronization is achieved, but the physical layout becomes constrained and manufacturing becomes difficult
Solution Approach 1:
The patent changes the cross-sectional area parameter of signal supply lines to achieve electrical length equalization. Instead of forcing all lines to have identical physical lengths, the line width is varied to create equivalent electrical characteristics. This allows flexible physical routing and layout while maintaining timing synchronization, significantly improving ease of manufacture and layout flexibility.
Data Source
AI summary
Provided is an optical modulator module in which a modulation substrate having a plurality of optical modulation units is stored inside a package case. The optical modulator module includes a plurality of signal supply lines configured to supply a modulation signal to the optical modulation unit through a connector terminal which is introduced into the package case. At least two or more of the plurality of signal supply lines are set such that the signal supply lines have overall electrical lengths which are different from each other. A particular part of the signal supply line employs at least one of the following configurations (a) and (b):(a) setting the signal supply line having a longer overall electrical length to have a wider cross-sectional area of a surface perpendicular to a direction in which the modulation signal propagates; and(b) setting a cross-sectional area of the particular part to be wider than cross-sectional areas of parts other than the particular part and setting the signal supply line having a longer overall electrical length to have the particular part increased in length.