Convergence problem in FDTD


saber_tmpass3.fsp (1.8 MB)
Hi, I am using mode expansion monitor in the attached simulation but getting T_forward more than 1 (1.017 to be exact) in the “monitor_3_x”. I have tried using finer mesh size (mesh accuracy=7) and stabilized PML. But it didn’t work. Can you please help me solve the issue.


Hi, @md.saber,

Apparently, this issue has been described already.
Here are the relevant links:

If it does not resolve your problem, please write here.


Hi @md.saber
I run your FDTD file with PML accuracy 2 and i plot T_forward in the monitor_3_x. Here is the plot :

The maximum value for T_forward is 1.0017 and for T_total is 1.00213. Could you please explain to me, why do you want only the T_forward ? Let’s investigate it. I think that happens due to the fact that there is another waveguide in close proximity. Maybe, there is mutual exchange between the two waveguides.