Optical Modulator Intermediate Substrate Signal Routing
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Solution Overview
Problem
In optical modulators with multiple Mach-Zehnder type modulation sections arranged in parallel on a single substrate, high-frequency propagation loss and narrow modulation bandwidth issues arise due to curved signal electrode lines, leading to increased power consumption and noise, while attempts to reduce substrate width exacerbate crosstalk and deteriorate high-frequency response characteristics.
Innovation Solution
The optical modulator employs a configuration with separate intermediate substrates for signal lines corresponding to each optical modulation section, allowing for side-by-side input and output connections with varying electrical lengths to synchronize modulation signals, and uses a detour pattern for signal lines on the intermediate substrate to reduce propagation loss and prevent crosstalk, while maintaining a narrow substrate width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If signal electrode lines are arranged directly above optical waveguides for high-speed modulation, then modulation bandwidth is improved, but high-frequency propagation loss increases and noise increases
Solution Approach 1:
The patent introduces an intermediate substrate as a mediator between the main substrate and the signal electrode lines. The signal electrode lines are formed on the intermediate substrate rather than directly on the main substrate, allowing for optimized electrical connections while reducing high-frequency propagation loss and noise. This intermediary structure enables the signal lines to be positioned optimally for both electrical performance and optical modulation requirements.
2Area of stationary object
If substrate width is reduced to decrease device size, then device compactness is improved, but crosstalk between adjacent modulation sections increases
Solution Approach 1:
The patent divides the signal electrode lines into separate segments on the intermediate substrate, with each segment corresponding to a specific optical modulation section. This segmentation allows for independent optimization of each signal line path, enabling the use of detour patterns that route signals away from adjacent sections, thereby reducing crosstalk while maintaining compact substrate dimensions.
Solution Approach 2:
The patent utilizes the vertical dimension by forming signal electrode lines on an intermediate substrate layered above the main substrate. This dimensional separation allows the signal lines to be routed in three-dimensional space, using detour patterns that exploit the vertical layering to avoid adjacent modulation sections and reduce crosstalk without increasing the horizontal substrate footprint.
3Loss of time
If signal electrode lines are made longer to synchronize modulation signals, then signal synchronization is improved, but propagation loss increases
Solution Approach 1:
The patent changes the electrical parameters of the signal electrode lines by forming them on the intermediate substrate with specific detour patterns. This allows for adjustment of electrical length and propagation characteristics to achieve signal synchronization. The detour patterns enable optimization of path length while managing propagation loss through careful routing that minimizes exposure to loss-prone regions.
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 ensures synchronized modulation light output with a wide modulation band, reduced noise, and lower power consumption, enabling cost-effective production by allowing for narrower substrate widths and improved high-frequency response.
Implementation Method 1
an optical waveguide device which uses an electro-optic crystal such as lithium niobate (LiNbO3) or lithium tantalate (LiTaO2)... due to the electric field generated between the signal electrode 131 and the earth electrode 132, the refractive indices of the branching waveguides 123 and 124 respectively change
Implementation Method 2
the output end T2 of the signal electrode 131 is connected to the earth electrode 132 via a resistance (not illustrated in the figure) to make a travelling wave electrode... By changing the cross-section shape of the signal electrode 131 to control the effective refractive index of the microwave electric signal RF, and by matching propagation speeds of the light and the microwave electric signal with each other
Data Source
AI summary
In an optical modulator, an intermediate substrate is provided separate from a main substrate on which a plurality of optical modulation sections are provided in parallel, and signal lines corresponding to the optical modulation sections are formed on the intermediate substrate. The signal lines are connected to signal electrodes corresponding to the main substrate, and have electrical lengths that are different from each other. Furthermore, the propagation loss per unit length in the signal lines on the intermediate substrate is preferably less than the propagation loss per unit length in the signal electrodes on the main substrate. As a result, even if a plurality of optical modulation sections are arranged in parallel, and the input ends of the signal electrodes of the optical modulation sections are arranged side by side on one side face of the substrate, synchronized modulation light of a low noise at a wide band width can be output from the optical modulation sections.