Setting FDE Simulation Control Panel #

This section describes the FDE simulation control panel.

After adding the FDE solver and setting the project, click To run button in the FDE tab. Simulation control panel is displayed automatically on the right side of the software interface, and mode analysis is set within the simulation control panel.

Simulation Control Interface #

Mode Analysis Window #

The simulation control panel of FDE solver is shown in the figure below, which mainly consists of mode list, modes workspace, mode display and mode analysis setting.

Number	Class	Description
1	Mode list	Display mode parameters obtained from mode-solving.
2	Modes workspace window	Data repository; stores all information required to perform complex operations such as mode coupling.
3	Mode display window	Select information such as result type and components to be plotted.
4	Setting calculation parameters	Input parameters of mode analysis and run mode solving.

Frequency Sweep Analysis #

Set Analysis type tab to Frequency sweep analysis. The frequency analysis window is then displayed as follows:

Number	Class	Description
1	Frequency analysis display interface	Select information such as result type and components to be plotted.
2	Setting calculation parameters	Customize parameters for frequency analysis and run mode solving.

Mode Coupling Window #

When switching to Overlap, enter mode coupling interface, which displays the profile of currently selected mode and result of mode coupling.

Basic Setting of FDE Simulation Control Panel #

Mode List #

The Mode list tab displays mode information resulting from mode-solving.

Name	Description
Mode#	The serial number of a mode.
Effective index	The effective refractive index of a mode.
TE/TM fraction	The ratio between TE and TM energy distribution in a mode.
Loss	Transmission loss of a mode, namely, energy attenuation of optical signals caused by absorption, scattering and other factors in waveguide devices.
Wavelength	The wavelength of mode-solving.
Mode name	The name of a mode.

Effective Index #

Calculate the effective index of the mode using the following formula (Effective Index):

$n_{eff}= \frac{c}{v}=\frac{\beta}{k_0}$

Where $c$ is the speed of light in vacuum, $v$ is group velocity of the mode, $\beta$ is the propagation constant of the mode, $k_0$ is the wave vector in free space $k_0=\frac{2\pi}{\lambda}$.

TE/TM Fraction #

TE/TM fraction (TE/TM fraction(%)): The ratio between TE and TM energy distribution in a mode. Calculate it using the following formula:

$\text{ TE fraction } = 1-\frac{\int\left|E_{\perp}\right|^{2} dA_{||}}{\int\left(|E|^{2}\right) dA_{||}}$

$\text{TM fraction } =  1-\frac{\int\left|H_{\perp}\right|^{2} dA_{||}}{\int\left(|H|^{2}\right) dA_{||}}$

Wherein, $E_{\perp}$ is the electric field component along the propagation direction, $H_{\perp}$ is the magnetic field component along the propagation direction, and $A_{||}$ is the integrated area over the mode cross-section of an optical waveguide.

Loss #

Calculate transmission loss of the mode using the following formula (Loss(dB/cm))：

${Loss (dB/cm)} = -0.2log_{10}(e^{-2\pi / \lambda})$

Modes Workspace #

Modes workspace is a data repository that stores all information required to perform complex operations (such as mode overlap). Stored data may be from Mode list or imported by the user.
The following section demonstrates how to load data to the Modes workspace window.

Storing Data in the Mode List #

In the Mode list, right-click and select mode required, and click Add to model space to load data of the mode to Modes workspace.

Storing Data Files Imported by User #

In the Modes workspace window, right-click, and then click Load to select a data file to be loaded to Modes workspace.

Name	Description
Name	The name of data.
Dimensions	The dimensions of data.

Mode Analysis #

In Analysis type tab, select Model analysis, which consists of setting calculation parameters and result profile.

Beam Profile #

The Beam profile tab displays profile of the mode.

Name	Description
Results	Specify the type of the data to be plotted. Select two data types, namely Mode fields and Index from the dropdown list.
Components	When selecting Mode fields from Results, you can select E Magnitude, Ex, Ey, Ez, H Magnitude, Hx, Hy, and Hz from Component. When you select Index from Results, you can select Index_x, Index_y, and Index_z from Component.
Scalar	Abs: Modulus of the selected component; Re: Real part of the selected component; Im: Imaginary part of selected component; Phase: Argument of selected component.
Refresh	Refresh the profile.
Visualize data	Open Visualize data window.
Plot in new window	Plot profile in a new window.

Setting Calculation Parameters #

Name	Description
Total modes	Maximum number of modes to be solved.

• Frequency

Name	Description
Frequency	Frequency of mode solving, a read-only parameter.
Wavelength	Wavelength of mode solving, a read-only parameter.

• Guess

Name	Description
Use max refractive index	Use maximum refractive index of structure for mode calculations.
Guess value	Specify the target refractive index calculated by the mode. Calculate modes close to user-defined effective index values. This parameter is enabled when Use max refractive index is unchecked.

• Bent waveguide

This parameter is enabled when mode in bent waveguide is solved.

Name	Description
Bend radius	Radius of curvature of a bent waveguide.
Bend waveguide width	Width of a bent waveguide.

• TE/TM

Name	Description
Quasi-TE	The electric field in Quasi-TE mode is mainly concentrated perpendicular to propagation direction (transverse direction), and there may be some non-zero electric field components in the propagation direction (longitudinal direction). The electric field in the TE mode is completely concentrated perpendicular to propagation direction (transverse direction), that is, there is no electric field component in transmission direction (longitudinal direction).
Quasi-TM	The magnetic field in the Quasi-TM mode is mainly concentrated perpendicular to propagation direction (transverse direction), and there may be some non-zero magnetic field components in propagation direction (longitudinal direction). The magnetic field in the TM mode is completely concentrated perpendicular to propagation direction (transverse direction), that is, there is no magnetic field component in transmission direction (longitudinal direction).
All	All modes.

• Modes Solver Status

Name	Description
Solve modes	Click this button. The modes solver will solve the mode according to parameters set by the user.

Frequency Analysis #

Select the analysis type as Frequency sweep analysis, and the system will automatically switch to the frequency analysis window. This window consists of two parts: setting calculation parameters and result images. Frequency analysis performs mode solutions at different frequency points to obtain optical properties such as group refractive index, dispersion, and loss.

The calculation parameter settings for frequency analysis are similar to those for mode analysis. For specific configurations, please refer to the relevant instructions in the Mode Analysis section above.

Track Selected Mode #

Frequency analysis requires mode solutions at multiple frequency points within the wavelength range, so it is necessary to set Wavelength Point. If you need to track a specific mode, enable the Track Selected Mode function.

The steps to use this function are as follows:

• Determine the mode to track. Perform frequency analysis without checking Track selected mode, and select the mode to track from the results (e.g., mode#9).
• Check the Track selected mode option and enter the wavelength range. The minimum wavelength will be automatically set to the wavelength of the selected mode, and the maximum wavelength can be manually entered.
• Click Solve Modes to perform mode solution again.

After the solution is completed, you can view the following in the frequencysweep results: the best mode overlap (overlap) of all modes at each frequency point, the mode ID of the selected mode at each frequency point, and the corresponding effective refractive index (neff). Additionally, the mode fields of the selected mode at each frequency point are retained.

Mode Coupling #

In the window, click Overlap to switch to mode coupling window. Overlap tab is used to solve mode coupling.

Name	Description
Solve overlap	Calculate coupling of the mode in the mode list to the mode in the modes workspace.
Components	Select a field component from the dropdown list, which includes E Magnitude, Ex, Ey, Ez, H Magnitude, Hx, Hy, and Hz.
Scalar	Abs: Modulus of the selected component; Re: Real part of the selected component; Im: Imaginary part of selected component; Phase: Argument of selected component.
Table mode profile selected	The mode profile in the currently selected mode list.
Workspace mode profile selected	The mode profile in the currently selected modes workspace.

Case: SMF-28 Fiber #

SMF-28 Fiber