Optical nonlinear time variant s-parameter element
Keywords
optical, bidirectional
Ports
| Name | Type |
|---|---|
| input | Electrical Signal |
| port 1 | Optical Signal |
| port 2 | Optical Signal |
Properties
General Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
name Defines the name of the element. |
Optical Nonlinear S-Parameter | - | - |
|
annotate Defines whether or not to display annotations on the schematic editor. |
true | - | [true, false] |
|
enabled Defines whether or not the element is enabled. |
true | - | [true, false] |
|
type Defines the element unique type (read only). |
Optical Nonlinear S-Parameter | - | - |
|
description A brief description of the elements functionality. |
Optical nonlinear time variant s-parameter element | - | - |
|
prefix Defines the element name prefix. |
SPAR | - | - |
|
model Defines the element model name. |
- | - | - |
|
library Defines the element location or source in the library (custom or design kit). |
- | - | - |
|
local path Defines the local path or working folder $LOCAL for the element. |
- | - | - |
|
url An optional URL address pointing to the element online help. |
- | - | - |
Standard Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
configuration Defines the bidirectional or unidirectional element configuration. |
bidirectional | - | [bidirectional, unidirectional |
|
load from file Defines whether or not to load s-parameters from an input file or to use the currently stored s-parameters. |
false | - | [true, false] |
|
s parameters filename The file containing the s-parameters. Refer to the Implementation Details section for the format expected. |
- | - | - |
Waveguide/Mode 1 Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
orthogonal identifier 1 The first identifier used to track an orthogonal mode of an optical waveguide. For most waveguide, two orthogonal identifiers '1' and '2' are available (with the default labels 'TE' and 'TM' respectively). |
1 | - | [1, +∞) |
|
label 1 The label corresponding to the first orthogonal identifier. |
TE | - | - |
Waveguide/Mode 2 Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
orthogonal identifier 2 The second identifier used to track an orthogonal mode of an optical waveguide. For most waveguide, two orthogonal identifiers '1' and '2' are available (with the default labels 'TE' and 'TM' respectively). |
2 | - | [1, +∞) |
|
label 2 The label corresponding to the second orthogonal identifier. |
TM | - | - |
Numerical Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
time constant Defines the time constant use to estimate the average the input power. |
0 | s | [0, +∞) |
|
convert noise bins Defines if noise bins are incorporated into the signal waveform. |
true | - | [true, false] |
|
automatic seed Defines whether or not to automatically create an unique seed value for each instance of this element. The seed will be the same for each simulation run. |
true | - | [true, false] |
|
seed The value of the seed for the random number generator. A value zero recreates an unique seed for each simulation run. |
1 | - | [0, +∞) |
Numerical/Digital Filter Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
single tap filter Defines whether or not to use a single tap digital filter to represent the element transfer function in time domain. |
false | - | [true, false] |
|
number of taps estimation Defines the method used to estimate the number of taps of the digital filter. |
fit tolerance | - | [disabled, fit tolerance, group delay |
|
filter fit tolerance Defines the mean square error for the fitting function. |
0.001 | - | (0, 1) |
|
window function Defines the window type for the digital filter. |
rectangular | - | [rectangular, hamming, hanning |
|
number of fir taps Defines the number of coefficients for digital filter. |
256 | - | [1, +∞) |
|
maximum number of fir taps Defines the number of coefficients for digital filter. |
4096 | - | [1, +∞) |
|
initialize filter taps Defines whether to use the initial input signal to initialize filter state values or to set them to zero values. |
false | - | [true, false] |
|
fractional delay Defines whether to use a fractional delay filter or force the delay to be an integer multiple of the sample period. |
true | - | [true, false] |
|
delay compensation The number of delays to compensate for latency. |
0 | - | [0, +∞) |
Diagnostic Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
run diagnostic Enables the frequency response of the designed filter implementation and the ideal frequency response to be generated as results. |
false | - | [true, false] |
|
diagnostic size The number of frequency points used when calculating the filter frequency response. |
1024 | - | [2, +∞) |
Results
| Name | Description |
|---|---|
| diagnostic/response #/transmission | The complex transmission vs. frequency corresponding to the ideal and designed filter. |
| diagnostic/response #/gain | The gain vs. frequency corresponding to the ideal and designed filter. |
| diagnostic/response #/error | Mean square error comparing the frequency response of the designed filter implementation with the ideal frequency response. |
====================================
Implementation Details
The Optical Nonlinear S-Parameter element is used when the output signal power varies with both electrical signal level and input optical signal power. It is especially useful when modeling saturable absorber. This element only works for two-port element (1 by 1 element) at this stage and the optical powers defined in the s-parameter file need to follow the order of port1 mode1, port1 mode2, port2 mode1 and port2 mode2, respectively.
The Optical Nonlinear S-Parameter file format is shown below:
("output port name","mode label",mode ID (out),"input port name",mode ID (in),"type","voltage;Pport1mode1;Pport1mode2;Pport2mode1;Pport2mode2")
(number of frequency points, 8)
\(voltage_1\) Pport1mode1 Pport1mode2 Pport2mode1 Pport2mode2 \(f_1\) abs(s) angle(S)
\(voltage_1\) Pport1mode1 Pport1mode2 Pport2mode1 Pport2mode2 \(f_2\) abs(s) angle(S)
...
\(voltage_1\) Pport1mode1 Pport1mode2 Pport2mode1 Pport2mode2 \(f_N\) abs(s) angle(S)
\(voltage_2\) Pport1mode1 Pport1mode2 Pport2mode1 Pport2mode2 \(f_1\) abs(s) angle(S)
\(voltage_2\) Pport1mode1 Pport1mode2 Pport2mode1 Pport2mode2 \(f_2\) abs(s) angle(S)
...
\(voltage_2\) Pport1mode1 Pport1mode2 Pport2mode1 Pport2mode2 \(f_N\) abs(s) angle(S)
...
...
...
\(voltage_M\) Pport1mode1 Pport1mode2 Pport2mode1 Pport2mode2 \(f_N\) abs(s) angle(S)
Note that with this file format, the s-parameter is not only time-variant (with different specified voltage values) but also nonlinear (with different input optical signal power). The following example uses the Optical Nonlinear S-Parameter element to simulate an absorber that saturates at a certain input signal power.
Example files:
optical_nonlinear_s_parameter.icp
The circuit in the example file is shown below:
In the circuit, two Gaussian pulses pass the absorber and the waveform before and after the absorber are being measured. The following figure shows the results of the absorber with the driving voltage of 0 V, -2V and -5V, respectively, overlay with the original signal. We can see that the output signal saturates at some input power levels.