The workflow required to perform simulations with 64-bit 3D Simulator is almost the
same as for the “regular” 32-bit simulator(s):

Step Action
1 Create a New Layout

a.   Define the material and waveguide in profile designer b.   Set up the initial simulation domain

c.   Draw the waveguide

2 Define simulation parameters
3 Define input wave

a.   Set up time domain input

b.   Set up the transverse domain input

4 Observe the refractive Index
5 Set up the Observation Objects (data-detectors) to extract the field pattern and transmission/Reflection spectrum.
6 Launch 64-bit 3D Simulator (menu “Simulation->Simulate 3D using 64-bit Simulator…”).
7 Perform the post-simulation analysis

The 64-bit simulator differs from 32-bit mainly in the aspect of DFT calculations. The 32-bit simulators perform DFT calculations and time domain data are stored for the whole volume. However, the calculation domain of the 64-bit simulator can occupy TB (Terabytes) of computer memory. In this case, the amount of generated data would be enormous, which would be impractical and unmanageable. To resolve this issue, the DFT calculations are performed only for the Observation Areas, and time domain data are collected only for Observation Points.

You can configure the DFT settings in Simulation Parameters for 3D 64-bit Simulations. When you choose menu option “Simulation->Simulate 3D using 64-bit Simulator…” you will be presented with “3D Simulation Parameters” dialog box specific for the 64-bit simulator. OptiFDTD provides default configuration of Spectral DFT settings. See User Reference manual for description.


Performance of simulations on multiprocessor (multi-core) computers. In order to achieve the highest performance (speed) of the simulation, it is recommended that the computer is not used while the simulations are in progress:

The calculations are performed on all available processors in so called true-parallel algorithm (the only applicable parallel processing method for FDTD algorithm). In result the overall performance (speed) of the simulations depends on the processing speed of the slowest processor, since all other processors have to wait until the last processor completes its simulation sequence.

If the computer is used for other tasks during the simulations, the operating system will take some CPU time to support the user running his application (e.g. email, internet browser, word editors, etc.). It will decrease the CPU time spent by one (or more) of the processors on simulations.

DFT Calculations.

When performing simulations with 64-bit Simulator, make sure that the designed project has Observation Objects (Areas or Points) defined. Otherwise, the simulation results will not be stored for the post-simulation analysis.

All 32-bit simulators are also available under 64-bit machine. However, their memory usage is still limited to 2GB.