Multi-Electrode Optical DAC Modulator for Linearized Output
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Solution Overview
Problem
Current digital-to-analog converters, particularly those using Mach-Zehnder Interferometer modulators, face challenges with non-linearity, leading to limited dynamic range and resolution in analog signal conversion, which is critical for high-bandwidth applications like wireless communication and medical imaging.
Innovation Solution
A linearized optical digital-to-analog modulator is developed, utilizing an electrically controllable modulator with M actuating electrodes where M≥N, and an electrode actuating device that applies voltages based on multiple bits of the input data word, employing a digital-to-digital converter to optimize electrode actuation patterns and lengths for improved linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a Mach-Zehnder Interferometer modulator is used for digital-to-analog conversion, then the device can achieve high-speed modulation and long-haul transmission capability, but the inherent non-linear response limits the dynamic range and resolution
Solution Approach 1:
The modulator is divided into multiple independently controllable electrodes (M≥N) instead of a single electrode. Each electrode can be actuated with different voltages based on multiple bits of the input data word, allowing the system to segment the control function and achieve linearized response through coordinated actuation of multiple segments.
Solution Approach 2:
The patent changes the control parameters by applying voltages to multiple electrodes simultaneously based on multiple input bits, rather than using a single voltage control. This parameter transformation enables the system to overcome the inherent cosine-shaped non-linearity and achieve improved linearity and dynamic range while maintaining high-speed modulation capability.
2Measurement precision
If the modulation range is reduced to operate in a quasi-linear regime, then linearity is improved, but the dynamic range and bandwidth are limited
Solution Approach 1:
By segmenting the control into multiple electrodes, the system can distribute the modulation across several elements. This allows the overall modulation range to be expanded while each individual electrode operates in a more linear regime, thus achieving both improved linearity and increased dynamic range simultaneously.
Solution Approach 2:
The patent transitions from one-dimensional single-electrode control to multi-dimensional control involving multiple electrodes actuated by multiple input bits. This dimensional expansion allows the system to achieve linearized response without sacrificing dynamic range, as the additional control dimensions provide more degrees of freedom for optimization.
3Measurement precision
If an analog pre-distortion circuit is used to compensate for non-linearity, then linearity is improved, but the system complexity increases and digital signal processing capabilities are not fully utilized
Solution Approach 1:
The patent replaces the analog pre-distortion circuit approach with a digital control approach. Instead of using analog circuits to pre-compensate for non-linearity, the system uses digital-to-digital conversion and electronic control of multiple electrodes, leveraging digital signal processing capabilities to achieve linearization with reduced analog circuitry and lower overall system complexity.
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 solution achieves enhanced linearity and dynamic range in analog signal conversion, effectively addressing the non-linearity issues of existing converters, enabling higher performance in multi-GHz mixed-signal systems and supporting increased bandwidth demands.
Implementation Method 1
since the modulating voltage via the electro-optic effect controls the optical phase delay in a basically linear fashion
Data Source
AI summary
In a system for converting digital data into a modulated optical signal, an electrically controllable device, including a modulator having one or more actuating electrodes, provides an analog-modulated optical signal that is modulated in response to output data bits of a digital-to-digital mapping. A digital-to-digital conversion provides the mapping of input data words to the output data bits. The mapping enables adjustments to correct for non-linearities and other undesirable characteristics, thereby improving signal quality.