Semiconductor IQ Modulator Layout for Low-Crosstalk Compact Chips
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor IQ optical modulators face challenges in downsizing and reducing driving voltage while maintaining high bandwidth and suppressing crosstalk, particularly due to the need for ground electrodes that increase chip size and limit layout flexibility.
Innovation Solution
The proposed solution involves using an SS differential radio frequency line configuration without ground electrodes, optimizing the layout of phase modulation electrodes and RF lines, and ensuring a minimum distance between phase modulation units and DC phase adjustment electrodes to maintain crosstalk suppression and reduce chip size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ground electrodes (GND lines) are arranged in GSSG or GSGSG differential line configuration to suppress crosstalk, then crosstalk suppression is improved, but chip size increases and layout flexibility is reduced
Solution Approach 1:
The patent removes ground electrodes from the differential line configuration, extracting the harmful element (ground electrodes that occupy space) while maintaining the essential function of differential signaling. The SS line configuration achieves crosstalk suppression through the differential nature of the signals themselves and precise spacing, without requiring ground electrodes, thus reducing chip size while maintaining crosstalk suppression performance of -30 dB or less up to 70 GHz.
Solution Approach 2:
The patent changes the configuration parameter from GSSG/GSGSG (with ground electrodes) to SS (without ground electrodes). This parameter change involves modifying the line structure by removing ground electrodes and adjusting the spacing between signal lines to 60 μm or less, which maintains electromagnetic field containment and crosstalk suppression through optimized geometric parameters rather than through ground electrode shielding.
2Object-affected harmful factors
If ground electrodes are arranged symmetrically with respect to signal lines to suppress crosstalk, then crosstalk suppression is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent extracts ground electrodes from the structure, eliminating the need for symmetric arrangement around signal lines. This removal of ground electrodes simplifies the layout design process and increases manufacturing flexibility, as the SS line configuration only requires maintaining a minimum spacing of 60 μm between differential signal lines without the additional constraint of symmetric ground electrode placement.
3Area of stationary object
If phase modulation units are placed close together to reduce chip size, then chip size is reduced, but crosstalk between channels increases
Solution Approach 1:
The patent optimizes the spacing parameter between phase modulation units and differential signal lines, setting it to 60 μm or less. This parameter optimization allows close placement of functional units to reduce chip size while maintaining crosstalk suppression through the combined effect of differential signaling and optimized spacing, achieving near-end and far-end crosstalk characteristics of -30 dB or less.
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 achieves a compact semiconductor IQ modulator with excellent radio frequency characteristics, reducing chip size and maintaining crosstalk suppression, with near-end and far-end crosstalk characteristics of -30 dB or less up to 70 GHz.
Implementation Method 1
The polarization multiplexing type IQ optical modulator inputs an RF modulated electrical signal to one end of a modulation electrode provided along the arm optical waveguide of the child MZM, thereby generating an electro-optical effect and applying phase modulation to two optical signals propagating in the optical waveguide of the child MZM.
Data Source
AI summary
A semiconductor IQ optical modulator in which a phase modulation unit is configured by a differential capacitively loaded traveling-wave electrode structure based on an SS line configuration, phase modulation units of adjacent channels are spaced apart from each other by 400 μm or more, a distance between main signal lines of the capacitance loading type structure is 60 μm or less, a DC phase adjustment electrode and a PAD are provided between an I side phase modulation unit and a Q side phase modulation unit, the DC phase adjustment electrode is spaced apart by at least 80 μm or more from a signal line of the phase adjustment unit, and a crosstalk characteristic between the adjacent channels is −30 dB or less in a required frequency band.