why is transmission negative in mode expansion?



Whenever I use the power monitors for varFDTDfrequency monitors, I get a negative value for transmission. Why is this?


Hi Sonia,
The sign of the transmission depends on the direction of propagation. The transmission gets negative when the power is flowing through the monitor in the negative direction.

I hope this helps.



Hi Gregory,
Is it possible to flip the monitor around? I don’t see how to do this.



No, the sign is actually defined based on the axis used in the software. The easiest, to get a positive value, is either to get the absolute value or apply a -1 factor. You can do that by scripting, when getting the data, or through the user interface, when visualizing the transmission: in the “Attributes”, there is a column “Scalar operation”, select “abs” or “-Re” instead of the default value (“Re”).


The reason I ask is that I want to run an optimization or sweep it would be nice to be able to maximize transmission instead of minimize it. I can do this with adding an analysis group but I was just hoping there was a simpler way of doing it.


Unfortunately, I can’t really think of any other way than using a structure group or making sure the light is propagating in the positive direction.