Optical straight waveguide
Keywords
optical, bidirectional
Ports
| Name | Type |
|---|---|
| port 1 | Optical Signal |
| port 2 | Optical Signal |
Properties
General Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
name Defines the name of the element. |
Straight Waveguide | - | - |
|
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). |
Straight Waveguide | - | - |
|
description A brief description of the elements functionality. |
Optical straight waveguide | - | - |
|
prefix Defines the element name prefix. |
WGD | - | - |
|
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 |
|
frequency Central frequency of the waveguide. A Taylor expansion around this frequency is performed to estimate the propagation transfer function of the waveguide. |
193.1 |
THz* *std. unit is Hz |
(0, +∞) |
|
length The length of the waveguide. |
10e-006 | m | [0, +∞) |
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 | - | - |
|
loss 1 The loss corresponding to the first orthogonal identifier. |
0 | dB/m | [0, +∞) |
|
effective index 1 The effective index corresponding to the first orthogonal identifier. |
1 | - | (-∞, +∞) |
|
group index 1 The group index coefficient corresponding to the first orthogonal identifier. |
1 | - | [0, +∞) |
|
dispersion 1 The dispersion coefficient corresponding to the first orthogonal identifier. |
0 | s/m/m | (-∞, +∞) |
|
dispersion slope 1 Defines the dispersion slope corresponding to the first orthogonal identifier. |
0 | s/m^2/m | (-∞, +∞) |
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 | - | - |
|
loss 2 The loss corresponding to the second orthogonal identifier. |
0 | dB/m | [0, +∞) |
|
effective index 2 The effective index corresponding to the second orthogonal identifier. |
1 | - | (-∞, +∞) |
|
group index 2 The group index coefficient corresponding to the second orthogonal identifier. |
1 | - | [0, +∞) |
|
dispersion 2 The dispersion coefficient corresponding to the second orthogonal identifier. |
0 | s/m/m | (-∞, +∞) |
|
dispersion slope 2 Defines the dispersion slope corresponding to the second orthogonal identifier. |
0 | s/m^2/m | (-∞, +∞) |
Waveguide/Mode 1/Thermal Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
effective index temperature sensitivity 1 Defines the ratio between effective index variation and temperature. |
0 | /K | (-∞, +∞) |
|
excess loss temperature sensitivity 1 Defines the ratio between loss variation and temperature. |
0 | /K | [0, +∞) |
Waveguide/Mode 2/Thermal Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
effective index temperature sensitivity 2 Defines the ratio between effective index variation and temperature. |
0 | /K | (-∞, +∞) |
|
excess loss temperature sensitivity 2 Defines the ratio between loss variation and temperature. |
0 | /K | [0, +∞) |
Thermal Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
thermal effects Defines whether or not to enable thermal effects. |
false | - | [true, false] |
|
temperature Defines the temperature. |
%temperature% | K | (-∞, +∞) |
|
nominal temperature Defines the nominal temperature where temperature sensitivity values are measured. |
300 | K | (-∞, +∞) |
|
thermal fill factor The waveguide length ratio affected by the thermal effects. |
1 | - | [0, 1] |
Numerical/Digital Filter Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
digital filter Defines whether or not to use a digital filter to represent the element transfer function in time domain. |
false | - | [true, false] |
|
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
An optical straight waveguide is a physical structure that confines light waves (electromagnetic waves) in an optical spectrum. Fiber is also a common type of optical straight waveguide. The two orthogonal identifiers "1" and "2" (with the default labels "TE" and "TM", respectively) have the following definition for group index and dispersion coefficient.
|
Group Index |
$$ n_{g}=\frac{c}{v_{g}}=c \frac{\partial k}{\partial \omega}=\frac{\partial}{\partial \omega}\left(\omega n_{eff}(\omega)\right)=n_{eff}(\omega)+\omega \frac{\partial n}{\partial \omega} $$ |
(1) |
|
Dispersion Coefficient |
$$ D_{\lambda} = - \frac{2 \pi c}{\lambda^2} \cdot \frac{\partial^2 k}{\partial \omega^2} $$ |
(2) |
Due to the refractive index change when light enters the waveguide from other media, the speed and phase of the light will change accordingly. Hence the optical straight waveguide is always used as a phase shifter or an optical delay line. The phase change and time delay introduced by a piece of straight waveguide of length L, effective and group indices of neff and ng can be calculated by the equations listed below, where c is the speed of light:
|
$$ \Delta \varphi = \frac{2 \pi n_{eff}}{\lambda} \cdot L $$ |
(3) |
|
$$ \Delta t = \frac{L \cdot n_{g}}{c} $$ |
(4) |
The optical straight waveguide can be used in numerous structures for different design and application purposes. In the example file straight_waveguide.icp, the ONA measures the delay and phase shift introduced by the waveguide. The following figure shows the system in the example file with the straight waveguide has the properties shown on the right hand side:
|
|
|
In the system shown above, the optical signal inputs to the first Y branch is split into two identical signals. The waveguide in the upper branch introduces a periodic phase shift to the signal with respect to wavelengths. The measurements of the gain and phase of the two branches are shown below.
|
|
|
By recombining the two branches, the phase difference of signals in the two arms will construct and destruct the signal periodically with respect to wavelength (frequency). This gives an interferometer effect. The gain (intensity transmission frequency response) and phase of the signal outputs from the second Y branch are shown below:
|
|
|
|