In this unit we are going to take a look at the different time-dependent sources in INTERCONNECT
that can be used for time domain simulations and learn about their settings.
We will start by taking a close look at the CW laser source within the "Sources" folder
of the element library.
This is a time-dependent source, and INTERCONNECT will automatically run a time domain simulation
when it's present in a circuit.
We can set the signal processing method through the "output signal mode" property
under the "Simulation" section (show in the property editor).
We can see that the property is set to sample, and is greyed out, which means that the value
can't be edited.
This is because value is inherited from the "Root Element" using an expression.
We can check the value of the "output signal mode" property of the Root Element by selecting
it in the Element Tree.
You can also click on any empty space in the design window to select the "Root Element".
By default, the "output signal mode" property is set the "sample".
Let's set the "output signal mode" property to "block".
Going back to the CW laser element we can see that the signal processing method is now
set to "block", consistent with the change we made in the Root Element.
We can also define the value directly in the source element.
To do this we will first have to delete the expression.
Once the expression is deleted, we can use the drop down menu to select the mode we want.
We can also right click on the property and choose to inherit the value from the "Root
This is a safe approach, as the best practice is to have same solver type for all sources.
Only advanced users should consider using different solver modes in the same simulation.
We can modulate the optical signal from a CW laser using the amplitude modulator element
and by applying a modulating electrical signal to the modulation port.
There are multiple electrical sources available in the Element Library that can be used to
provide the modulating signal.
For example, we can use a sine wave source, or we can use
an electrical pulse generator like the non-return to zero pulse generator element.
When combined with the pseudo-random bit sequence generator, or PRBS, the electrical pulse generator
can provide a time-varying digital electrical signal to the modulation port.
There is also an electrical impulse generator in the Elements Library.
Note that all of these time dependent sources have the "output sample mode" property and
they inherit the value from the Root Element by default.
The ONA can also be used to run time domain simulations.
Under the "Simulation" section you can see that the "output signal mode" property is disabled.
Now, if we set the "analysis type" to "impulse response" then the ONA becomes a time-dependent
source and the "output signal mode" property becomes available.
The default option is "sample" mode.
Let's add a straight waveguide and connect it to the ONA to simulate its optical transmission.
Run the simulation. Let's plot the transmission in dB from the ONA results.
Next we'll switch analysis type to "scattering data" in the ONA to run a frequency domain
simulation for the same waveguide.
Plot the transmission in dB on the same window.
Since we have not optimized the filter properties of the waveguide, we can see that the transmission
is only correct at the center frequency.
In the Transient Sample Mode simulation setup tips subsection we will learn how to
set up the digital filter of the waveguide element for a sample mode time domain simulation.