Optical Modulator Relay Substrate Groove Crosstalk Suppression
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Solution Overview
Problem
In high-speed optical fiber communication systems, especially those using DP-QPSK modulators, crosstalk between high-frequency signal lines on the relay substrate becomes a significant issue due to increased transmission rates, which cannot be adequately suppressed by existing methods like vias and ground electrode strengthening, leading to signal energy leakage and mode conversion.
Innovation Solution
The optical modulator incorporates a relay substrate with grooves in the ground conductor patterns between signal conductor patterns, where the grooves extend from the signal input side and are deeper at the input side, potentially penetrating to the rear surface, and are designed to suppress radiation microwaves generated by mode conversion, thereby reducing crosstalk without increasing the modulator's size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the distance between adjacent high-frequency signal lines is increased to suppress crosstalk, then crosstalk is reduced, but the relay substrate size increases contrary to downsizing demands
Solution Approach 1:
The patent introduces ground electrodes as intermediary shielding structures between adjacent signal lines. These ground electrodes act as mediators that intercept and redirect electromagnetic fields, preventing direct coupling between signal lines while maintaining compact spacing. The ground electrodes are connected to reference potential, creating equipotential regions that reduce voltage differences and crosstalk between neighboring signals.
Solution Approach 2:
The patent adds a vertical dimension to crosstalk suppression by forming grooves that extend through the substrate thickness. These grooves create three-dimensional isolation structures that compartmentalize electromagnetic fields in both horizontal and vertical directions. By utilizing the depth dimension, the patent achieves effective signal isolation without increasing the horizontal footprint of the relay substrate.
2Productivity
If transmission rate is increased to meet high-speed communication demands, then communication capacity improves, but crosstalk between signal lines becomes more severe
Solution Approach 1:
The patent implements crosstalk suppression structures (ground electrodes and grooves) in advance, before high-frequency signals are transmitted. These structures are pre-configured in the relay substrate layout to anticipate and prevent electromagnetic coupling issues that would arise at high transmission rates. The shielding geometry is designed beforehand to handle the expected frequency range and signal power levels.
Solution Approach 2:
The patent modifies geometric parameters of the relay substrate structures, including ground electrode dimensions, groove depth and width, and spacing configurations. By optimizing these physical parameters, the patent adjusts the electromagnetic field distribution and impedance characteristics to minimize crosstalk while supporting high transmission rates. The parameters are tuned to achieve optimal performance at the target frequency range.
3Object-affected harmful factors
If existing crosstalk suppression methods (vias and ground electrode strengthening) are used, then some crosstalk is reduced, but suppression is insufficient at high transmission rates like 400 Gb/s
Solution Approach 1:
The patent combines multiple crosstalk suppression mechanisms into a composite shielding structure: ground electrodes provide horizontal shielding, grooves provide vertical compartmentalization, and via connections provide reference potential pathways. This multi-component composite approach creates synergistic effects that achieve superior crosstalk suppression compared to any single method alone, ensuring signal integrity at 400 Gb/s transmission rates.
Solution Approach 2:
The patent divides the continuous ground plane into segmented ground electrode regions separated by grooves. This segmentation creates isolated shielding zones that more effectively contain electromagnetic fields within specific areas. The divided structure prevents electromagnetic energy from spreading across the entire substrate, enhancing localization of field confinement and improving crosstalk suppression at high frequencies.
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 suppresses crosstalk between signal conductor patterns, maintaining good optical modulation characteristics even at higher transmission rates, such as 400 Gb/s, while adhering to the demand for downsizing and maintaining manufacturability at or below the cost of existing solutions.
Implementation Method 1
mode conversion at the high-frequency signal input part (signal input part) of the relay substrate
Implementation Method 2
signal propagation mode conversion... mainly at the high-frequency signal input part (signal input part) of the relay substrate... leakage of the high-frequency signal at the input portion
Data Source
AI summary
An optical modulator includes an optical modulation element having a plurality of signal electrodes; a plurality of signal input terminals each of which inputs an electrical signal to be applied to each signal electrode; a relay substrate on which a plurality of signal conductor patterns electrically connecting the signal input terminals and the signal electrodes, and a plurality of ground conductor patterns are formed; and a housing that houses the optical modulation element and the relay substrate, in which the relay substrate has at least one groove extending from the signal input side on which the signal input terminal is connected to the signal conductor pattern, in at least one ground conductor pattern formed between adjacent signal conductor patterns, and the groove is formed such that a length extending from the signal input side is longer than a length of the signal input terminal extending on the signal conductor pattern.