the transmission of bent waveguide simulation


dear all
I have want to do a sweep and get the relationship about the radius of the bent waveguide and the tranmission.bent 90_1.fsp (445.5 KB)
This above is my simulation.But I find some problem about my simulation.
**1…**First of all,the relationship between the transmission of the monitor(“T”) and the radius looks strange.

In my opinion,the transmission of the monitor(“T”) will not change with the radius of the bent waveguide because the light have not go through the bent waveguide.Where do I make an error?
2…I compare the transmission of monitor(“T1”) with that of monitor(“T2”),which as show below.
I found when the radius is large than 1.5 micrometer,the two curves nearly coincide,which mean that the transmission loss just happen in the first bent waveguide while there is no loss in the second bent waveguide
.furthermore,the transmission of monitor(“T1”) and monitor(“T2”) is larger than 1
when the bent radius is larger than 3.5 micrometer.I think it is not right. can you help me solve the two questions. Thanks a lot.


Dear @jbwei

It looks like your waveguides are not truncated by simulation region. As a result your waveguide will act like mirror with a big reflections at the end facets. That is one of the reason why your simulation took so long to reach the auto shutoff level. I adjusted for one case (r-Si=1um) and transmission was close to 1 rather than 0.7. Please see the image below for proper setting of simulation regions:

Please make the adjustments and let me know if you had any questions.


dear bkhanaliloo
I have tried as you said and the transmission extracted now is less than 1. Thanks for your help.:slight_smile:


Hi @bkhanaliloo,
In your setup, why do you use a 2 monitors; one after a 90 degree bend and the other after the 180 bend? I usually use the same setup but with one monitor at the input and the other at the output.



Hi @aya_zaki

I started with the simulation file of jbwei, and he/she used it because he/she was seeing some weird results at different monitors (the simulation region didn’t overlap with the geometry and there was reflection at the waveguide facet). I kept the original simulation file unchanged except the FDTD simulation region. I hope this answered your question.