Optical waveguide coupler
Keywords
optical, bidirectional
Ports
Name | Type |
---|---|
port 1 | Optical Signal |
port 2 | Optical Signal |
port 3 | Optical Signal |
port 4 | Optical Signal |
Properties
General Properties
Name | Default value | Default unit | Range |
---|---|---|---|
name Defines the name of the element. |
Waveguide Coupler | - | - |
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). |
Waveguide Coupler | - | - |
description A brief description of the elements functionality. |
Optical waveguide coupler | - | - |
prefix Defines the element name prefix. |
C | - | - |
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 |
Waveguide Properties
Name | Default value | Default unit | Range |
---|---|---|---|
insertion loss Defines the insertion loss (attenuation). |
0 | dB | [0, +∞) |
input parameter Defines whether to provide the power coupling coefficient, measurements, or the cross over length. |
coupling coefficient | - | [coupling coefficient, length, table |
length The length of the waveguide. |
0 | m | [0, +∞) |
load from file Defines whether or not to load measurements from an input file or to use the currently stored values. |
false | - | [true, false] |
conjugate Defines whether to use the conjugate of the cross-coupling coefficients or not. |
false | - | [true, false] |
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 | - | - |
coupling coefficient 1 The power coupling coefficient corresponding to the first orthogonal identifier. |
0.5 | - | [0, 1] |
cross over length 1 The cross over coupling length corresponding to the first orthogonal identifier. |
1 | m | [0, +∞) |
measurement filename 1 The file containing the frequency dependent power coupling coefficients. |
- | - | - |
coupling coefficients 1 The table containing the frequency dependent power coupling coefficients. |
<2> [193.1e+012, 0.5] | - | - |
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 | - | - |
coupling coefficient 2 The power coupling coefficient corresponding to the second orthogonal identifier. |
0.5 | - | [0, 1] |
cross over length 2 The cross over coupling length corresponding to the second orthogonal identifier. |
1 | m | [0, +∞) |
measurement filename 2 The file containing the frequency dependent power coupling coefficients. |
- | - | - |
coupling coefficients 2 The table containing the frequency dependent power coupling coefficients. |
<2> [193.1e+012, 0.5] | - | - |
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, +∞) |
filter delay Defines the time delay equivalent to a number of coefficients for digital filter. |
0 | s | [0, +∞) |
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] |
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. |
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Implementation Details
The “Waveguide Coupler” (C) element represents a 2 x 2 directional waveguide coupler. Signals input into the ports are output to the two ports on the opposite side of the element. There is no reflection back out of the input port. The total power of the output signals is equal to the input power minus the “insertion loss”. The ratio between the power of the two output signals is determined by the power coupling coefficient. This coupling coefficient defines the fraction of the total output power that is output by the cross port.
The C element can be defined using several different methods, selected using the “input parameter” property:
- “coupling coefficient”: The coupling coefficient is directly defined as a single number.
- “length”: The coupling coefficient is defined based on the “length” and “cross over length” properties. The coupling coefficient is equal to sin(length/cross over length).
- “table”: The coupling coefficient is defined as a function of frequency with a table of values.
If the “table” option is selected there are two ways to define the table. If “load from file” is set to “false”, the coupling coefficients and frequencies can be modified in the matrix editor by clicking on the “Value” field of the “coupling coefficients 1”/”coupling coefficients 2” property in the Property View.
If “load from file” is set to “true”, a table from a text file can be imported. The required file format consists of a column of frequency values and a column of the corresponding power coupling coefficients, separated by tabs or spaces. An example is shown below:
1.930e+14 0.4
1.931e+14 0.5
1.932e+14 0.6
Once the table has been imported from a file, “load from file” can be set to “false” and the imported table can be modified in the matrix editor. However, if “load from file” is set to “true” when running the simulation, the file will be reloaded and any changes to the table will be overwritten by the values in the file.
A pi phase shift can be applied to the signal output from the cross port by setting “conjugate” to “true”. If “conjugate” is set to “false”, no phase shift is applied to the output signals. The C element can be changed between bidirectional and unidirectional operation with the “configuration” property.
Use in ring resonator circuits
The C element is commonly used for the coupling region of ring resonator circuits, as in the (ring resonator AG example). For sample mode transient simulations with these circuits it is best to use a single value for the coupling coefficients (in other words, a point coupler). A frequency dependent value defined using a table will introduce artificial delays to the circuit, which will lead to inaccurate results for the properties of the ring resonator.