why is transmission negative in mode expansion?


#1

Hi,

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


#2

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.

Greg


#3

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

Sonia


#4

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”).


#5

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.


#6

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.