Optical Modulator Bias Electrode Surface Acoustic Wave Interference
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Solution Overview
Problem
Optical modulators with multiple bias electrodes experience unstable bias control operations due to surface acoustic waves generated by dither signals, leading to fluctuations in optical characteristics and temperature drift compensation, which cannot be explained by electrical interference and are temperature-dependent.
Innovation Solution
The bias electrodes are designed to suppress electro-acoustic conversion efficiency and prevent electrical signals from being received through surface acoustic waves by varying electrode intervals and configurations, such as stepwise or linear changes, different characteristic frequencies, and angular displacements, to reduce interference between electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple bias electrodes are used for temperature drift compensation and bias control, then the optical modulation characteristics can be maintained under varying temperature conditions, but surface acoustic wave interference occurs between electrodes leading to unstable bias control operations
Solution Approach 1:
The patent introduces ground electrodes as intermediary elements positioned between the bias electrodes. These ground electrodes act as shields that block or absorb surface acoustic waves generated by dither signals, preventing them from propagating to adjacent bias electrodes. This intermediary structure maintains the necessary electrical isolation while allowing the bias electrodes to function effectively for temperature drift compensation without mutual interference.
Solution Approach 2:
The patent extracts and separates the ground electrode function from the bias electrode structure, creating distinct functional zones. By positioning ground electrodes independently between bias electrodes, the harmful surface acoustic wave propagation path is removed or interrupted, while the bias electrodes retain their temperature compensation function. This separation resolves the interference problem while preserving the reliability benefit of multiple bias electrodes.
2Stability of the object's composition
If dither signals are applied to bias electrodes for temperature drift compensation, then bias point stability can be maintained, but surface acoustic waves are generated that interfere with other bias electrodes
Solution Approach 1:
The patent converts the harmful surface acoustic waves into a beneficial shielding effect by strategically positioning ground electrodes. The ground electrodes, when subjected to dither signals, generate surface acoustic waves that cancel or absorb the waves from adjacent bias electrodes. This transforms the potentially harmful phenomenon into a protective mechanism that stabilizes bias control while maintaining temperature drift compensation functionality.
Solution Approach 2:
Ground electrodes serve as mediators that receive and dissipate surface acoustic wave energy between bias electrodes. By placing these intermediary elements in the acoustic wave propagation path, the harmful effects are intercepted and neutralized, allowing dither signals to be applied to bias electrodes for stability without causing interference to neighboring electrodes.
3Area of stationary object
If bias electrodes are positioned close to each other for compact device design, then device size is reduced, but surface acoustic wave interference between electrodes increases
Solution Approach 1:
The patent introduces ground electrodes as intermediary shielding elements positioned between closely spaced bias electrodes. These ground electrodes block the propagation of surface acoustic waves that would otherwise travel freely between adjacent bias electrodes in a compact configuration. This allows the device to maintain a small footprint while preventing harmful interference through the intermediary shielding structure.
Solution Approach 2:
The patent addresses the two-dimensional packing problem by introducing a vertical or intermediate dimensional solution. Ground electrodes are positioned in the space between bias electrodes, utilizing the available dimensional space to create acoustic wave barriers. This allows compact planar integration while adding a third dimension of protection against surface acoustic wave interference.
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 approach stabilizes bias control operations independent of dither signal frequencies and ambient temperature, enabling robust high-frequency and high-capacity optical communication by minimizing surface acoustic wave interference.
Implementation Method 1
The bias electrodes are constituted and/or disposed so that an electrical signal applied to one of the bias electrodes is prevented from being received by another one of the bias electrodes through a surface acoustic wave
Implementation Method 2
surface acoustic waves generated by dither signals
Implementation Method 3
a substrate having a piezoelectric effect
Implementation Method 4
LiNbO3 (hereinafter, also referred to as LN) having an electro-optic effect
Data Source
AI summary
A substrate (102) having a piezoelectric effect, optical waveguides (138a, 140a, 138b, 140b, and the like) formed on the substrate, and a plurality of bias electrodes (152a, 152b, and the like) that control an optical wave (s) which propagate through the optical waveguides are provided, and the bias electrodes are constituted and/or disposed such that an electrical signal applied to one of the bias electrodes is prevented from being received by another one of the bias electrodes through a surface acoustic wave.