IQ Optical Modulator RF Extension Line Alignment
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Solution Overview
Problem
Conventional IQ optical modulators face challenges in achieving high-speed operation over a wide band due to increased electrical loss and skew in differential signal transmission lines, which deteriorate frequency response and cause crosstalk, especially at high baud rates.
Innovation Solution
The IQ optical modulator is designed with an optimized functional block layout where the RF extension line is aligned in the same direction as the optical waveguide stripe, reducing skew and loss by minimizing the length of the RF extension line and integrating a differential output driver amplifier to reduce transmission line loss and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the RF extension line is bent by 90 degrees to supply power to the modulation region, then the optical input can be orthogonal to the high frequency line, but skew and propagation delay occur causing frequency response deterioration and crosstalk
Solution Approach 1:
The patent repositions the RF extension line to extend in the same direction (longitudinal dimension) as the optical waveguide stripe rather than bending it 90 degrees perpendicular to the optical input. This dimensional alignment eliminates skew and propagation delay between the RF signal path and optical modulation region, resolving the frequency response deterioration and crosstalk issues while maintaining high modulation speed
2Power
If the RF extension line length is increased to reach the modulation region, then power can be supplied to the modulation electrode, but transmission line loss increases deteriorating modulation band
Solution Approach 1:
The RF extension line is pre-configured to extend in the same direction as the optical waveguide stripe from the beginning of the device structure, rather than requiring a 90-degree bend later. This preliminary alignment minimizes the total length of the RF extension line needed to reach the modulation region, reducing transmission line loss and improving modulation band while ensuring adequate power supply to the modulation electrode
3Object-generated harmful factors
If LiNbO3 is used for the optical waveguide, then electro-optical effect can be achieved, but light confinement is weak requiring 90 degree bending of high frequency line
Solution Approach 1:
The patent employs asymmetric positioning where the RF extension line is aligned with the optical waveguide stripe in the same longitudinal direction, while the optical input remains orthogonal to this direction. This asymmetric configuration allows LiNbO3 to provide its electro-optical effect without requiring a 90-degree bend of the RF line, as the RF signal path is optimally positioned from the start, improving both light confinement and eliminating frequency response issues
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 higher modulation speed and wider band operation with reduced power consumption and minimized skew, achieving efficient differential signal transmission and improved modulation characteristics.
Implementation Method 1
an RF signal is inputted to a modulation electrode provided along the child MZM 56 of an optical waveguide configured by dielectric material such as LiNbO3 to thereby generate an electro-optical effect to perform a phase modulation upon two polarized light signals propagating in the optical waveguide of the child MZM 56
Data Source
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AI summary
An IQ optical modulator including: a parent Mach-Zehnder type (MZM) optical waveguide; child MZM optical waveguides constituting two arms of the parent MZM; two electrode transmission lines provided along the two arms of the child MZM, respectively, and receiving modulation signal to phase-modulate an optical signal; an RF extension line connected to the two electrode transmission lines, respectively; a first optical splitter branching light into the two arms of the parent MZM; a second optical splitter branching light into the two arms of the child MZM; and a first optical multiplexer multiplexing light from the two arms of the child MZM, wherein stripe direction of the child MZM optical waveguide is same as the RF extension line, the second optical splitter, and the first optical multiplexer, and is orthogonal to the first optical splitter.