S-parameter elements allow you to load data describing the frequency-dependent complex transmission
for all input and output port combinations and polarizations.
S-parameter elements are primitive elements, meaning that they are provided in the Element Library.
You can find these elements under the S-Parameters folder of the Element Library.
Examples of components that you may want to represent using S-parameter elements include
Y-branches, grating couplers, and Multi-mode interference, MMI couplers.
The format of the data stored in the S-parameter files depends on the particular element being used,
as there are different S-parameter elements available for varying numbers of ports,
for time-variant S-parameters and so on.
A page with a summary of the S-parameter file formats is linked below this video.
You can also find details about the file format for each S-parameter element in the documentation of that element.
As you may recall, you can access the documentation page for an element by right-clicking on it
and selecting "Help" from the context menu.
The Optical N Port S-Parameter element can be used to load S-parameter data for a device
with an arbitrary number of ports and modes, so it is one of the most commonly used S-parameter elements.
This slide shows an example of the frequency-dependent S-parameters that can be loaded for an
Optical N Port S-Parameter element to represent a device with 2 ports and 1 mode supported in each port.
For each input and output mode combination, there is a block of data.
The data is prefixed by a header which contains the output port name, mode label,
and mode ID of the output mode, followed by the input port name, mode ID of the input mode,
and the type which is "transmission" in this case.
The type can be "modulation" if the data includes temperature dependence.
For the first header we see that the output is port 2 mode 1 and the input is port 1 mode 1,
so the data that follows will be for the S21 element of the S matrix.
The next line indicates the number of rows and columns of the data, so there will be 2 rows, corresponding to 2 frequencies,
and 3 columns where the first column will contain the frequency data, the second column will include the amplitude of the S parameters,
and the third column will include the phase of the S-parameters in radian.
The S-parameter data can be extracted by performing component-level simulations using Lumerical FDTD Solutions or MODE Solutions.
The component-level simulations are beyond the scope of this course, but we will show an example of S-parameter data export
from FDTD Solutions in the demonstration in the next unit to give an idea of how it can be done.
Another S-parameter element is the Time Variant S-parameter element.
Active components often have a frequency response that depends on the applied voltage bias or current.
The Time Variant S-Parameter element takes frequency response data for different electrical signal values,
and when no exact value of the electrical signal is found, the S-parameter values are interpolated from the data.
In the following unit, we'll demonstrate how to set up an Optical N Port S-Parameter element.