Optical Modulator Amplitude Control via Electrode Length Ratios
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Solution Overview
Problem
Existing optical modulators face challenges in easily adjusting light intensity ratios for QAM formats of 2n values and in managing dither signal frequencies, leading to increased complexity and sensitivity to manufacturing deviations.
Innovation Solution
The optical modulator features multiple Mach-Zehnder type optical waveguides disposed in parallel on a substrate, with a unified modulation signal applied to each unit, and mechanical structures adjusted to achieve specific amplitude and phase differences, allowing for simplified light intensity adjustment and reduced dither signal frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional light intensity adjusting units (attenuators, MZ optical waveguides) are added to make the amplitude ratio of optical outputs constant, then the light intensity adjustment precision is improved, but the device complexity and size increase
Solution Approach 1:
The patent extracts the light intensity adjustment function from separate external components (attenuators, additional MZ waveguides) and integrates it directly into the modulation electrode structure of the optical modulation unit. By forming modulation electrodes with different lengths (e.g., 2:1 ratio) on the same substrate, the amplitude ratio control is built-in, eliminating the need for additional light intensity adjusting units and reducing overall device complexity while maintaining precise amplitude ratio control
Solution Approach 2:
The patent combines the modulation function and light intensity adjustment function into a single integrated structure. The modulation electrodes are directly formed on the optical waveguide substrate with specific length ratios, merging the phase modulation capability with the amplitude ratio control in one component, thereby reducing the total number of components while achieving both functions simultaneously
2Device complexity
If asymmetrical branching ratio in optical waveguide is used for light intensity adjustment, then the device structure is simplified, but the manufacturing precision and reliability deteriorate due to sensitivity to manufacturing deviations
Solution Approach 1:
The patent changes the geometric parameter (length) of the modulation electrodes to achieve the desired amplitude ratio. By setting specific length ratios (e.g., 2:1) for modulation electrodes on the same substrate, the system achieves precise amplitude control through well-defined geometric parameters that are easier to control during manufacturing compared to asymmetrical branching ratios, thereby improving reliability while maintaining structural simplicity
3Productivity
If multiple dither signal frequencies are applied to multiple optical modulation units for simultaneous bias control, then the bias control speed is improved, but the device complexity and frequency management difficulty increase
Solution Approach 1:
The patent makes a single dither signal frequency serve multiple functions by applying it simultaneously to multiple optical modulation units. This unified frequency approach allows simultaneous bias control of all modulation units without requiring separate frequencies for each unit, reducing frequency management complexity while maintaining fast bias control speed. The same frequency can be used across different units with different mechanical structures, achieving universal control
4Adaptability or versatility
If multiple optical modulation units with different mechanical structures are used to achieve specific amplitude ratios, then the light intensity adjustment flexibility is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent achieves different amplitude ratios by changing a single geometric parameter (length) of the modulation electrodes while keeping other parameters consistent. This approach provides flexibility in achieving various amplitude ratios (e.g., 2:1, 1:1) while maintaining relatively loose manufacturing precision requirements, as only the length parameter needs to be controlled with specific ratios rather than multiple complex mechanical dimensions
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 enables stable and efficient adjustment of light intensity ratios, reduces the need for additional components, and allows for simultaneous bias control of optical modulation units with fewer frequency inputs, enhancing the modulator's performance and miniaturization.
Implementation Method 1
a modulation electrode for modulating light waves propagating through the Mach-Zehnder type optical waveguide
Data Source
AI summary
The optical modulator includes optical modulation units. The plurality of optical modulation units is disposed in parallel on the same substrate. One input waveguide branches off to be connected to the Mach-Zehnder type optical waveguide of each optical modulation unit, and an entire optical waveguide is formed such that outputs from the Mach-Zehnder type optical waveguides are combined and output through one output waveguide. A modulation signal with the same intensity is applied to a modulation electrode of each optical modulation unit. In at least some of the optical modulation units, mechanical structures including the modulation electrodes of the optical modulation units are configured such that an amplitude value of an optical output modulated by the modulation signal of the optical modulation unit is ½n (n is a natural number) of a maximum amplitude value in other optical modulation units.