Optical Modulator Wiring Equal Length Design
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Solution Overview
Problem
Optical modulators face excessive optical loss due to signal electrodes crossing optical waveguides, particularly in high-frequency systems like those above 100 GHz, leading to variations in optical loss across modulation regions.
Innovation Solution
The optical modulator design arranges input portions of all signal electrodes on one side of the substrate and output portions on the other, with equal wiring lengths between signal electrodes, and includes termination substrates with termination circuits and DC wiring to minimize electrode crossings and optical loss. Additionally, a resistor is used in the DC wiring, and light reception elements are integrated to monitor light waves, with a groove or conductor between termination circuits and wiring to reduce crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If signal electrodes are arranged to cross optical waveguides to access modulation regions, then electrical connection to modulation portions is achieved, but optical loss increases due to absorption and scattering by electrodes
Solution Approach 1:
The patent transitions from a planar electrode arrangement to a three-dimensional stacked configuration. Signal electrodes are positioned on different substrates (first substrate for input, second substrate for output) separated by a spacing structure, allowing electrical connection without planar crossing of optical waveguides. This dimensional change eliminates the trade-off between electrical access and optical loss.
Solution Approach 2:
A spacing structure acts as an intermediary element between the first and second substrates. This mediator maintains precise spacing between substrates while allowing signal electrodes to extend through the spacing structure to contact modulation portions, enabling electrical connection without direct electrode crossing of optical paths.
2Device complexity
If multiple signal electrodes are concentrated on one side of the substrate, then wiring complexity is reduced, but variation in optical loss across modulation regions increases
Solution Approach 1:
The patent segments the electrode arrangement into two separate groups: signal electrodes for first modulation portions on the first substrate, and signal electrodes for second modulation portions on the second substrate. This segmentation allows each group to be independently optimized, reducing wiring complexity while maintaining uniform optical loss through symmetric positioning relative to their respective optical waveguides.
Solution Approach 2:
The patent employs asymmetric substrate stacking where the first and second substrates are positioned at different locations relative to the optical waveguides, with each substrate's signal electrodes symmetrically arranged relative to their respective modulation portions. This asymmetric overall structure with symmetric local arrangements optimizes both wiring complexity and optical loss uniformity.
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 significantly reduces the number of control electrodes crossing optical waveguides, thereby minimizing optical loss and stabilizing modulation characteristics, enhancing the performance of high-frequency optical modulators.
Implementation Method 1
an optical waveguide and a control electrode for controlling light waves propagating through the optical waveguide
Implementation Method 2
a control electrode for controlling light waves propagating through the optical waveguide
Data Source
AI summary
The objective of the present invention is to provide an optical modulator adapted for use with various modulating units and various modulation regions, and with which variability in optical losses is limited as far as possible. An optical modulator in which an optical waveguide and a control electrode for controlling an optical wave propagating through the optical waveguide are provided in a substrate, characterized in that: the optical waveguide is provided with a first branching portion which causes one input light beam to branch into two light beams; each of a first and a second modulating portion connected to two branched waveguides which branch at the first branching portion is provided with a structure in which one or more Mach-Zehnder type optical waveguides are combined; the control electrode comprises signal electrodes which apply modulated signals to the first and second modulating portions; input portions of all the signal electrodes are disposed on either the left or the right of the substrate relative to the direction in which the optical wave propagates; and in relation to output portions of the signal electrodes, the output portions of the signal electrodes led out from each modulating portion are disposed on the side on which the first or second modulating portions are disposed, relative to the direction in which the optical wave propagates.