This page summarizes the S-parameter file formats for all the S-parameters elements.
| [[Note:]] The unit of the angle of the S-parameter (∠S) is the radian. |
Optical N Port S-Parameter
The Optical N Port S-Parameter element has two types available: "transmission" and "modulation."
Format for "transmission" type
Default
Option 1: with number of ports on the left and right sides of the element defined in the header
Option 2: with port name and position defined for individual port
This option should be used when you want to define the port name and port position in the S-parameter file. If not specified, the port names will follow the order "port 1", "port 2" etc.
Option 3: Group delay
An option is available to isolate the group delay, or linear, contribution to the phase. This makes it easier to keep track of intervals of \(2\pi\) in the phase data for long structures, where the phase changes quickly as a function of frequency. The header requires the group delay value, evaluated at the center frequency of the S-parameter frequency data in units of seconds. The phase angle in the third column is the total phase angle minus the group delay phase change relative to the center frequency. If the group delay phase contribution is not removed from the total phase, the group delay will be double-counted in the simulation. The group delay phase change for data point \(i\) is \(2 \pi \tau_g \times (f_i-f_c)\), where \(f_i\) is the frequency for data point \(i\), \(f_c=(f_1+f_N)/2\) is the center frequency, \(N\) is the number of frequency points and \(n_g\) is the group delay. The process for removing the group delay phase change is described in greater detail in this application example.
Option 4: sweep s-parameter file
Another option is available to sweep the s-parameter file. This makes it faster to load the right interpolated s-parameter to the element than using the lookup-table option because it eliminates the file loading process.
S-Parameter file sweep option (the group delay values are optional):
To further fasten the s-parameter file sweep process, user can use the convertnportsparametersweep command to convert the s-parameter sweep file from .txt format to a binary format (.idat).
User can also use the readnportsparameterat command to generate the interpolated s-parameter from the s-parameter sweep file based on given parameters and then assign it to the s-parameter element.
Option 5: Touchstone file format
In 2021R1.1 and later: The Optical N Port S-Parameter element supports Touchstone format S-parameter files:
- supports single mode with an arbitrary number of physical ports
- supports format with and without group delay (be able to read this from comments in Touchstone format)
For more information on touchstone file format details, please refer to the Electrical N Port S-Parameter section below.
Format for "modulation" type
For the Optical N Port S-Parameter element with "type" = "modulation", the file format is shown below. This format is used when the s parameter is temperature-dependent.
| [[Note:]] Only the "mode label" for the output port needs to be defined in the S-parameter file. That is because this "mode label" will be used to display the result in the analyzers. The "mode label" for the input port is defined in the sources or the Optical Network Analyzer (ONA) so there is no need to specify it in the file. |
Optical 1xN S-Parameter
This format applies to a single input port and \(N\) output ports.
In the case of \(N = 1\), the format looks as follows:
Optical S-Parameter
This format applies to a single input and a single output port.
If the S-parameters are symmetric (\(S_{11}=S_{22}\) and \(S_{21}=S_{12} \)), the following format can be used.
If all the S-parameters apart from \(S_{21}\) are zero, the following format can be used.
Optical N Port Propagation Parameter
For the Optical N Port Propagation Parameter element with "type" = "propagation", the file format is defined as:
Optical Time Variant S-Parameter
For the Optical Time Variant S-Parameter element with "type" = "modulation" and control input signal a, the file format is defined as:
Optical Nonlinear S-Parameter
The Optical Nonlinear S-Parameter element only works for 2 port (1 by 1) element at this stage, and with "type" = "transmission", the file format is defined as:
| [[Note:]] The optical powers for port1 mode1, port1 mode2, port2 mode1, and port2 mode2 need to be defined in this specific order. |
Electrical N Port S-Parameter
The file format follows the standard Touchstone file format. Users can choose between "magnitude angle" file format and "real imaginary and dB angle" file format.
The following example is a magnitude angle file format for a 4-port element:
The following example is a real imaginary and dB angle file format for a 2 port element:
The option line is required at the beginning of the file to specify the format of the data in the file. The option line starts with a "#" and has the format of:
where
Electrical Time Variant S-Parameter
The file format is shown below:
