Optical Transmitter Drive Circuit for Multilevel Modulation Linearity
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Solution Overview
Problem
The existing optical modulator modules with segmented electrode structures face limitations in achieving large-scale multilevel modulation due to a limited number of segmented electrodes, leading to uneven spacing of signal intensity levels and non-linear signal intensity with respect to input digital signals, making it difficult to ensure linearity of output light.
Innovation Solution
An optical transmitter system with a plurality of phase modulation regions, a decoder to decode digital signals, and a drive circuit with multiple DACs that output drive signals with amplitudes adjustable by a control circuit to achieve phase velocity matching and impedance matching, ensuring linearity of signal intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of segmented electrodes is increased to achieve large-scale multilevel modulation, then the modulation capacity is improved, but the device complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The electrode is divided into multiple segmented electrodes along the optical propagation direction, allowing independent control of each segment to achieve multilevel modulation. This segmentation enables the system to achieve high modulation capacity without requiring an excessive number of electrodes by optimizing the segmenting strategy and control algorithm.
Solution Approach 2:
The patent transitions from controlling multiple electrodes in one dimension to using a combination of fewer segmented electrodes with multi-level voltage control. By adding the voltage level dimension, the system achieves high modulation capacity with reduced electrode count, thereby lowering device complexity.
2Productivity
If segmented electrodes are used to achieve multilevel modulation, then the spectral efficiency is improved, but the signal intensity levels become uneven and linearity is degraded
Solution Approach 1:
The patent employs dynamic control of drive signal amplitudes applied to each segmented electrode. By adjusting the voltage levels dynamically based on the desired modulation state, the system achieves uniform signal intensity levels and maintains linearity between input digital signals and output optical intensity, resolving the uneven spacing problem inherent in static segmented electrode designs.
Solution Approach 2:
The patent changes the electrical parameters (voltage amplitude and phase) applied to each segmented electrode to optimize the optical output. By carefully controlling the magnitude and phase of drive signals, the system achieves uniform signal intensity levels and linear response characteristics while maintaining the spectral efficiency benefits of multilevel modulation.
3Power
If a traveling-wave type electrode is used to increase effective interaction length, then the modulation efficiency is improved, but the impedance matching becomes more difficult to maintain
Solution Approach 1:
The patent applies different electrical characteristics to different segments of the electrode structure. Each segmented electrode can have optimized impedance and voltage characteristics tailored to its specific position and function, allowing the system to maintain good impedance matching across the entire structure while achieving high modulation efficiency through the traveling-wave configuration.
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 system effectively adjusts the linearity of signal intensity in output light, enabling efficient multilevel modulation and overcoming the limitations of the segmented electrode structure by allowing for precise control of drive signal amplitudes and phase modulation.
Implementation Method 1
an optical modulator that includes an optical transmission line through which an optical signal propagates, a plurality of phase modulation regions being formed on the optical transmission line
Implementation Method 2
waveguide-type optical phase modulators are embedded into an optical waveguide-type MZ interferometer
Data Source
AI summary
The present invention provides an optical transmitter, an optical transmission/reception system, and a drive circuit, which are capable of adjusting linearity of signal intensity of output light. The optical transmitter includes an optical transmission lines through which an optical signal propagates, phase modulation regions being formed on the optical transmission line. A decoder decodes an input digital signal and outputs signals according to a decoded value. A drive circuit outputs drive signals level of which is equal to or more than three to the each of the plurality of phase modulation regions based on the signals. A control circuit adjusts full-scale amplitude of each of the drive signals by controlling the drive circuit.