Linearized Electro-Optical Modulator via Sub-Modulator Cascading
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Solution Overview
Problem
Electro-optical modulators exhibit inherent non-linearity in their transfer function between applied voltage and optical phase shift, limiting dynamic range and increasing system complexity and power consumption in applications such as radio over fibre, LIDAR, and communications.
Innovation Solution
A linearized electro-optical modulator is achieved by cascading multiple sub-modulators with different transfer functions, where the total transfer function is made substantially linear over a range of operating voltages by adjusting the geometry or doping levels of each sub-modulator, allowing for a superposition of independent phase shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single sub-modulator with a specific transfer function is used, then the device complexity is low, but the linearity of the transfer function is poor
Solution Approach 1:
The modulator is divided into multiple sub-modulators, each with a different transfer function characteristic (e.g., one with square-root characteristic and another with knee characteristic). By segmenting the single modulator into multiple functional units with complementary non-linear characteristics, the combined system achieves linearized transfer function while maintaining manageable complexity of individual components.
2Manufacturing precision
If multiple sub-modulators with different transfer functions are cascaded to achieve linearization, then the linearity of the transfer function is improved, but the device complexity increases
Solution Approach 1:
Multiple sub-modulators with different transfer function characteristics are combined in parallel or cascade configuration. Each sub-modulator contributes a complementary non-linear response that, when combined, cancels out the non-linearities and produces an overall linear transfer function. This merging approach achieves linearity through functional combination rather than requiring a single complex linearized structure.
3Adaptability or versatility
If the transfer function is made linear over a wider voltage range, then the dynamic range is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The transfer function characteristics of each sub-modulator are controlled by adjusting geometric parameters (such as waveguide dimensions, junction depths) and doping levels. By precisely controlling these physical parameters during fabrication, each sub-modulator achieves its intended non-linear transfer function, and their combination produces the desired linearized response over an extended voltage range, thereby expanding dynamic range while managing manufacturing precision requirements.
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 overcomes non-linearity issues, enhancing dynamic range and reducing system complexity and power consumption by achieving a linear transfer function across a wider range of voltages, improving performance in various applications.
Implementation Method 1
an electro-optical modulator which has been linearized with respect to a range of operating voltages... the combination of the transfer functions of each modulator is such that a total transfer function between an applied voltage and an optical phase shift of the modulation region is substantially linear
Data Source
AI summary
An electro-optical modulator. The electro-optical modulator comprising: an input waveguide, configured to guide light into a modulation region of the electro-optical modulator; a plurality of sub-modulators, within the modulation region, each sub-modulator having a transfer function between an applied voltage and an optical phase shift; and an output waveguide, configured to guide light out of the modulation region. The combination of the transfer functions of each sub-modulator is such that a total transfer function between an applied voltage and an optical phase shift of the modulation region is substantially linear over a range of operating voltages.