Mach-Zehnder Optical Modulator Compact Design
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Solution Overview
Problem
Mach-Zehnder interferometer type optical modulators have a large device length, making them difficult to integrate into small-size optical modules, and they require stable operation with varying reflective characteristics that differ between devices, leading to inconsistent modulated signal requirements.
Innovation Solution
A modified Mach-Zehnder interferometer type optical modulator design featuring a single optical coupler, phase shifting sections with upper electrodes to control light phase, and a reflecting portion with distributed Bragg reflectors to adjust phase differences and compensate for production errors, allowing for reduced device length and stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional Mach-Zehnder interferometer type optical modulator is used, then high-speed modulation capability is achieved, but the device length becomes large making it difficult to integrate into small-size optical modules
Solution Approach 1:
The optical waveguide is divided into multiple sections with different functions: input waveguide section, phase shifting section, and output waveguide section. The phase shifting section is further segmented into multiple phase shifting units, each contributing to the overall phase modulation while keeping individual sections compact.
Solution Approach 2:
The patent introduces a vertical dimension by forming the optical waveguide in a three-dimensional structure with upper and lower cladding layers and a core layer, allowing the waveguide to extend in multiple spatial dimensions rather than a single linear direction, thereby reducing the footprint area.
2Ease of manufacture
If reflective characteristics vary between devices, then manufacturing tolerance is relaxed, but stable operation and consistent modulated signal requirements become difficult to achieve
Solution Approach 1:
The patent introduces a feedback mechanism where the phase shifting section actively adjusts the phase of light to compensate for variations in reflective characteristics. By monitoring and adjusting the phase difference, the system maintains stable operation despite manufacturing variations.
Solution Approach 2:
The patent changes the refractive index parameter of the core layer by controlling the doping concentration and type (n-type or p-type) to optimize the phase shifting characteristics. This parameter optimization ensures stable operation across different devices while maintaining manufacturing tolerance.
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
The design enables the modulator to be compactly integrated into small-size optical modules with high-speed operation and stable performance by controlling light phase and compensating for reflective differences, achieving efficient modulation and reduced device capacitance.
Implementation Method 1
a phase shifting section that controls a phase of light propagating in at least one of the third and fourth optical waveguides
Implementation Method 2
a reflecting portion with distributed Bragg reflectors to adjust phase differences
Implementation Method 3
distributed Bragg reflectors to adjust phase differences and compensate for production errors
Data Source
AI summary
A Mach-Zehnder interferometer type optical modulator includes a first end facet and a reflecting portion opposing the first end facet; a single optical coupler including input and output ports, the optical coupler being disposed between the first end facet and the reflecting portion; first and second optical waveguides that are connected to the input ports of the optical coupler; third and fourth optical waveguides that are connected to the output ports of the optical coupler; and a phase shifting section disposed between the optical coupler and the reflecting portion. The phase shifting section includes a first optical waveguide structure constituting part of the third optical waveguide; a first upper electrode on the first optical waveguide structure; a second optical waveguide structure constituting part of the fourth optical waveguide; and a second upper electrode on the second optical waveguide structure.