Optical Modulator Laser Layout for Low-Reflection Signal Transmission
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Solution Overview
Problem
High-frequency modulation signals in optical communication systems experience significant signal loss due to electrical reflection, which impedes effective transmission to the optical modulator.
Innovation Solution
The optical modulator integrated laser device incorporates a substrate with a laser unit, optical modulation unit, and terminating resistors, where signal pads receive differential signals, and terminating resistors are positioned close to the modulation electrodes to minimize electrical reflection by reducing impedance mismatch and conductive path lengths to less than ¼ of the modulation signal wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the conductive path length is reduced to less than 1/4 of the modulation signal wavelength, then electrical reflection is minimized and signal transmission efficiency is improved, but the device layout and impedance matching become more complex
Solution Approach 1:
The patent applies preliminary action by pre-positioning the terminating resistor at a specific location (distance less than 1/4 wavelength from the modulation electrode) before signal transmission occurs. This advance placement ensures that impedance matching is already optimized when the high-frequency modulation signal arrives, preventing electrical reflection before it can occur. The terminating resistor is integrated into the substrate during manufacturing, so the impedance matching condition is established in advance rather than requiring post-adjustment.
Solution Approach 2:
The patent utilizes parameter changes by carefully controlling the distance parameter between the modulation electrode and terminating resistor to be less than 1/4 of the modulation signal wavelength. This specific parameter range transforms the impedance characteristics of the conductive path, changing it from a reflective condition to a matched condition. By adjusting this geometric parameter during device design and manufacturing, the system achieves optimal signal transmission without requiring complex active impedance matching circuits.
2Reliability
If the terminating resistor is positioned close to the modulation electrode, then impedance mismatch is reduced and signal reflection is minimized, but the area available for other components is reduced
Solution Approach 1:
The patent applies merging by integrating the terminating resistor directly into the substrate structure in close proximity to the modulation electrode, rather than placing it as a separate distant component. This consolidation achieves two goals: it ensures the resistor is positioned within the critical distance less than 1/4 wavelength for optimal impedance matching, while also utilizing the substrate area efficiently. The terminating resistor shares the substrate real estate with other components, reducing the overall device footprint while maintaining signal transmission reliability.
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 significantly reduces signal loss due to reflection, enhances signal transmission efficiency, and maintains consistent heat generation, thereby improving communication performance in high-frequency applications.
Implementation Method 1
electrical reflection of the modulation signal at a first end of the first terminating resistor is reduced
Implementation Method 2
magnitude of inductance of the first bonding wire is smaller than that of inductance of the second bonding wire
Data Source
AI summary
An optical modulator integrated laser device comprising: a substrate; a laser unit provided on the substrate and configured to output laser light; an optical modulation unit provided on the substrate, including a modulation electrode supplied with one of modulation signals, and configured to modulate the laser light; a first signal pad provided on the substrate, configured to receive an input of the one of the modulation signals as a positive phase signal of a differential signal, and connected to the modulation electrode; a second signal pad provided on the substrate side by side with the first signal pad and configured to receive an input of another of the modulation signals as a negative phase signal of the differential signal; and a first terminating resistor provided on the substrate and including a first end connected to the first signal pad and a second end connected to the second signal pad.