LCML - Y branch based on FDTD simulation results | lcml_y_strip_1550


This Y branch element is built by using simulation results from FDTD Solutions. The Y branch structure can be imported from a GDS file into FDTD.

Example Test File

y_branch.icp (259.8 KB)

User Guide

lcml_y_strip_1550 (y)

LCML: Y branch.


Name Type
opt_1 Optical Signal
opt_2 Optical Signal
opt_3 Optical Signal

Model Development

FDTD Solutions
1.Download the LCML_Ybranch.gds file from the LCML_resource folder. Open an FDTD Solutions simulation file and import the gds file, or download the four FDTD files that are for the combine and split TE and TM modes from the same LCML_resource subfolder.

2.The four .fsp files (LCML_Ybranch_TE_combine.fsp, LCML_Ybranch_TE_split.fsp, LCML_Ybranch_TM_combine.fsp and LCML_Ybranch_TM_split.fsp) need to be pre-run to have the results stored and then to get the s-parameter extracted. After run and save the .fsp files, open and run the script file lcml_y_s_extraction.lsf in the FDTD project file. This script will open the four pre-simulated FDTD files and extract the s-parameters and write the results one by one to a text file. All files can be found in the LCML_resource folder from the download page.

1.In INTERCONNECT, create a compound element.

2.Add three bidirectional optical ports namely “opt_1” (left), “opt_2” (right) and “opt_3” (right) and auto-arrange for their positions. Set the compound “model” to “lcml_y_strip_1550” and the compound “prefix” to “y”.

3.Expand the compound element, drag and drop an Optical N Port S-Parameter element to the schematic editor and load the lcml_ybranch.txt to it. Then connect the the corresponding relays and ports.

4.Back to the compound element and set icon.


Download the simulation file y_branch.icp from the top of this page. In this simulation file, the compact model of the Y-Branch is connected to and measured by an Optical Network Analyzer (ONA). Click on the “run” button and the ONA will be populated with measurement data. To view the simulation results, user can right click on the results and select “Visualize”.

Ports in FDTD for two modes(TE,TM)
Lumerical Compact Model Library (LCML)


Could you share these FDTD fsp files with us ?
Thanks a lot.


Hi @jwang026,

You can find all the resource files on the product dowload page:


Thank you.
Already download.