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Mentor Interoperability - Imbalanced MZM

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cover_picture_mentor_interop_imbalanced_mzm_zoom33In this layout-driven flow example, we calculate the optical spectrum of the imbalanced Mach-Zehnder Modulator (MZM) previous designed in Tanner L-Edit Photonics, as a function of the bias voltage. The transmission at the operating wavelength is also studied as a function of the bias voltage. Then move on to a time do main simulation with the imbalanced MZM, the eye diagram result is studied.  

 

This example requires the GPIC CML to be installed.

Files and Required Solvers

 

download-example

 

INTERCONNECT Tanner Interoperability

 

Minimum product version: 2019a r2

Contents

Overview

Run and results

Important model settings

Updating the model with your parameters

Taking the model further

Additional resources

Overview

Understand the simulation workflow and key results

workflow_mentor_mzm_zoom78

We are considering a layout-driven workflow where the circuit layout is designed in Tanner L-Edit Photonics and the circuit is simulated in INTERCONNECT.

 

The circuit is an imbalanced MZM, composed of waveguides, bend waveguides, directional couplers, edge couplers, tapers, phase shifters, terminators and bond pad elements (electrical contact).

 

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 behaviour, however they are not calibrated to a foundry process. Lumerical cannot provide any guarantee with respect to the model accuracy and completeness.

 

Step 1: Layout design and netlist extraction (Tanner L-Edit Photonics)

The circuit layout is designed in Tanner L-Edit Photonics using the GPIC iPDK, a generic photonic PDK. The netlist is then extracted.

The example files (layout, GPIC iPDK, etc.) are provided with the Tanner install package.

 

Step 2: Circuit simulation frequency domain test bench (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 obtain the gain spectrum of the imbalanced MZM under varied bias voltages.

 

Step 3: Circuit simulation time domain (INTERCONNECT)

We then conduct a time domain simulation with the imbalanced MZM cathode1 driven by a non-return to zero signal based on a pseudo-random bit sequence. An Eye Diagram Analyzer is used to obtain the eye diagram of the received time signal.

Run and results

Instructions for running the model and discussion of key results

Step 1: Layout and netlist extraction (Tanner L-Edit Photonics)

1.Open the MZM_imbalanced example (…/TannerEDA/TannerTools_vxxxx.x/Designs/MZM_imbalanced/lib.defs)

2.Open the desired layout cell, MZM_imbalanced

3.Export the netlists using the Lumerical header file (GPIC/models/lumerical/headerFile.spi)

 

This example is part of the Tanner installation package. We will not cover here the layout design or netlist export. Please refer to the documentation provided with Tanner for more information.

mentor_interop_imbalanced_mzm_layout_zoom33

Step 2: Circuit simulation frequency domain test bench (INTERCONNECT)

1.Open the simulation file Mentor_Interoperability_MZM_ONA.icp

Note: users will get the "Error loading reference" errors if the GPIC CML is not installed at this point. Users can manually install this CML or, run the script in the next step to get it installed automatically.

2.Open the script file Mentor_Interoperability_MZM_ONA.lsf

3.Click the run script button

4.Results are plotted automatically and can be accessed from the result view and the script workspace.

 

This Application Gallery example is provided with the netlist (Mentor_Interoperability_MZM_imbalanced.spi)

 

Gain spectrum

We use an Optical Network Analyzer (ONA) to calculate the gain spectrum (transmission in dB) for the MZM under different bias voltages (0V to 5V):

mentor_interop_imbalanced_mzm_gain_zoom25

 

Transmission vs. bias voltage

As the bias voltage “DC_1” is swept from 0V to 5V, the optical spectrum red shifts. Then we track the transmission at the operating wavelength (1550.26 nm) as we sweep through the bias voltage from 0V to 5V and generate the following plot:

mentor_interop_imbalanced_mzm_lambda_zoom25

Step 3: Circuit simulation time domain (INTERCONNECT)

1.Open the simulation file Mentor_Interoperability_MZM_EYE.icp

2.Open the script file Mentor_Interoperability_MZM_EYE.lsf

3.Click the run script button

4.Results are plotted automatically and can be accessed from the result view and the script workspace.

 

This Application Gallery example is also provided with the netlist (Mentor_Interoperability_MZM_imbalanced.spi)

 

Eye diagram

The eye diagram result will be generated by the above example files. The eye diagram resulting from the time domain simulation is quite open. This is because 1) a low bit rate is used (5 Gbits/s) and 2) because the phase shifter GPIC CML model implements a high speed model that is representative of behaviour with travelling-wave electrodes, instead of a low speed model that is representative of the lumped electrode implementation used here. As mentioned above, the GPIC is intended for demonstration purposes only. In a foundry CML, the phase shifter model would be calibrated to the intended implementation.

mentor_interop_imbalanced_mzm_eye_zoom25

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_v1.0.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

Optical Network Analyzer (ONA) settings

The ONA settings allow you to control:

Input power (0dBm)

Number of points (10000)

Plot kind (frequency or wavelength)

ona_settings_zoom31

 

Note: This circuit is designed to operate in the C-band (1546nm to 1559nm), TE mode. Care should be taken if you modify the ONA settings, to make sure you stay in the operating domain of the components.

 

The ONA simulation bandwidth (frequency range) need to match the time domain sample rate setting. In this case, we set the ONA “frequency range” to inherit the “sample rate” property to link the property values.

 

Some models of the GPIC CML include temperature sensitivity. The simulation temperature (300K) is set in the “Root Element” properties.

 

Time domain simulation settings

User can update the time domain simulation with the following parameters:

Set the wavelength of interest in the Laser Source.

Set the bit rate.

Set the electrical signal level (amplitude) of the non-return to zero Pulse Generator (NRZ).

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 layout in Mentor Tanner L-Edit Photonics, 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.

 

Import netlist from user interface:

1.Select the compound element

2.Import the netlist (*.spi) from File->Import->Import SPICE netlist

import_netlist_zoom30

 

Import netlist from script:

Use the "importnetlist" command

importnetlist(COMPOUND_NAME, "Mentor_Interoperability_Interferometer_50u.spi");

 

Where COMPOUND_NAME is the name of the compound element hosting the circuit.

 

Note: The same methodology can be applied to other circuits designed in Mentor Tanner L-Edit Photonics.

 

Use other test-bench circuits

In this example, the imbalanced MZM is studied using a frequency domain and a time domain test bench.  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

Related KB pages:

Mentor Interoperability - Interferometer

Install a Compact Model Library

Optical Network Analyzer (ONA)

Video:

Mentor and Lumerical partner with Towerjazz to advance Photonic IC design

Related Lumerical University courses:

Course_INT100 Course_SCRIPTING_v1

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