In this example, we calculate the gain spectrum and Free Spectral Range (FSR) of a Mach-Zehnder interferometer designed in Siemens EDA Tanner S-Edit as part of the schematic-driven flow.
This example requires the GPIC CML to be installed.
Overview
Understand the simulation workflow and key results
We are considering a schematic-driven workflow where the circuit layout is designed in Siemens EDA Tanner S-Edit and the circuit is simulated in INTERCONNECT.
The circuit is an imbalanced Mach-Zehnder interferometer, composed of waveguides, directional couplers, grating couplers and terminator elements.
| Note: The GPIC compact model library (CML) used here is intended for demonstration purpose only. The models are intended to be representative of typical component behavior, however, they are not calibrated to a foundry process. Ansys Lumerical cannot provide and guarantee with respect to the model accuracy and completeness. |
Step 1: Schematic design and netlist extraction (Siemens EDA Tanner S-Edit)
The circuit schematic is designed in Siemens EDA Tanner S-Edit using the GPIC iPDK, a generic photonic process design kit. The netlist is then extracted for the interferometer with a path length difference of 100 microns.
The example files (schematic, GPIC iPDK, etc.) are provided with Siemens EDA Tanner installation package.
Step 2: Circuit simulation (INTERCONNECT)
We import the netlist in an INTERCONNECT test-bench simulation file. The test-bench is composed of an Optical Network Analyzer (ONA) that is used to measure the gain spectrum as well as the free spectral range (FSR).
Run and results
Instructions for running the model and discussion of key results
Step 1: Schematic and netlist extraction (Siemens EDA Tanner S-Edit)
| Note: This example is part of the Siemens EDA Tanner installation package. We will not cover the circuit design or netlist extraction with Tanner S-Edit. Please refer to the documentation provided with Siemens EDA Tanner for additional information. |
- Open the interferometer example (.../TannerEDA/TannerTools_vxxxx.x/Designs/Interferometer/lib.defs)
- Open the interferometer schematic view to see the circuit design. This interferometer has a path length difference of 100 microns.
- Export the netlist using the SPICE netlist export tool (File/Export/SPICE)
The Export SPICE session should be configured as shown below. Ensure that “Export as” is set to “Subcircuit definition,” and the “Export control property” is set to “SPICE lumerical.” The netlist will be saved in the specified location.
For more information on Tanner S-Edit netlist extraction for INTERCONNECT, please visit the Siemens EDA interoperability guide .
Step 2: Circuit simulation (INTERCONNECT)
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Open the simulation file, SiemensEDA_S-Edit_Interoperability_Interferometer.icp
Note: users will get the "Error loading reference" errors if the GPIC CML is not installed at this point. Users must install this CML before opening this file. For more information, please visit the Install Compact Model Library page. - Open the script file, SiemensEDA_S-Edit_Interoperability_Interferometer.lsf
- Click the run script button
Results are plotted automatically and can be accessed from the result view and the script workspace.
This Application Gallery example is provided with the following netlist:
- SiemensEDA_S-Edit_Interoperability_Interferometer_100u.spi (\(100\mu m\) path length difference)
We use an Optical Network Analyzer (ONA) to calculate the gain spectrum (transmission in dB) for the TE mode.
The ONA can also extract the Free Spectral Range (FSR), representing the spacing between each peak of the transmission spectrum.
The script will output the mean FSR for the 100 micron path length difference in the script prompt.
For such Mach-Zehnder interferometer, the FSR is given by:
$$FSR = \frac{\lambda^2}{\Delta L n_g}$$
where \(\Delta L\) is the path length difference, and \(n_g\) is the group index of the waveguide.
Important model settings
Description of important objects and settings used in this model
This example requires the GPIC compact model library (CML) to be installed before running the example files. This example is provided with the CML file GPIC_v2.0.cml.
See the Install Compact Model Library page on the Knowledge Base for more information on how to install the CML.
Updating the model with your parameters
Instructions for updating the model based on your device parameters
Interferometer circuit design
Various components, including waveguides, grating couplers, and directional couplers are used to build the interferometer circuit in this example. These components have various parameters that can be updated based on your device parameters, including:
- Waveguide lengths (i.e., interferometer path length difference)
- Waveguide width/height
- Directional coupler splitting ratio (i.e., tuning the length/gap)
These component parameters can be updated by changing the values in Tanner S-Edit and exporting a new netlist to INTERCONNECT. Any parameters changed in S-Edit will be automatically updated in INTERCONNECT from the new netlist.
Optical Network Analyzer (ONA) settings
The ONA settings allow you to control:
- Input power (0dBm)
- Simulation bandwidth (start and stop frequency, 1565nm to 1530nm)
- Number of points (1000)
- Plot kind (frequency or wavelength)
- Polarization (orthogonal identifier, 1 for TE, 2 for TM)
| Note: This circuit is designed to operate in the C-band (1530nm to 1565nm), TE mode. Care should be taken if you modify the ONA settings to make sure your stay in the operating domain of the components. |
Some models of the GPIC CML include temperature sensitivity. The simulation temperature (300K) is set in the "Root Element" properties.
Taking the model further
Information and tips for users that want to further customize the model
Use updated/new netlist
You can modify the circuit in Siemens EDA Tanner S-Edit, export the new netlist and import it back to your INTERCONNECT test-bench circuit to verify how the modifications affect the behavior of the circuit. For more information on importing a netlist from Tanner S-Edit to INTERCONNECT, please visit Lumerical INTERCONNECT and Tanner L-Edit & S-Edit driven flows - User Guide .
Use other test-bench circuits
In this example, the interferometer is connected to an ONA to calculate its transmission spectrum and FSR.
Other circuits can be used. You can create different test-bench simulation files that you can use depending on the results you want to extract.
Additional resources
Additional documentation, examples and training material
See also
- Install a Compact Model Library
- Optical Network Analyzer (ONA)
- Design for manufacturability using CompoundTek’s PDK and Siemens-Ansys photonic layout-driven design flow (hosted by Siemens)
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