[CST] Loss Calculation - Gaussian Excitation

Hi all,
I just started some weeks ago working with CST and have a question concerning F-Parameters.
I want to calculate losses which occur if you want to couple light from a laser into a waveguide. For this i used a gaussian excitation (Home->Solver->Sources->Gaussian Excitation) as source and placed a waveguide above it. Afterwards I placed a port at the output of the waveguide in order to obtain the F-Parameter for that. After the simulation the corresponding F-Parameter which is defined as FourierTransform(Output_Signal)/FourierTransform(reference_Signal) gives me a value of -20 dB which is far too low. The losses shouldn't be higher than 2 dB.
So I did another simulation with only a gaussian excitation and a port placed just above it. I still obtain losses of about 12 dB (Loss = F-Parameter), even though there should be no losses in that case.
Does anyone know what could be the reason for that?
Thanks in Advance!

So, here's a dropbox link to 2 CST files:
https://www.dropbox.com/sh/cfag0wkxw...gL8EGAvea?dl=0
The E-field and 1D-results are already calculated.
The 2 Cst files contain two different cases:
1.) Gaussian Beam as excitation source with 1 μm radius and a port just above it. I wanted to see the F-Parameter for that case and there should be no losses -> F=0dB. This is not the case here.
2.) Gaussian Beam as excitation source with 1μm radius and a mirror above is to reflect the beam. On the right face you can see a port to obtain the F-parameter...
The refractive index of the background material was set to 1.53 in order to have total reflection on the mirror...

Normally moderators would issue a warning about "Inappropriate Use of External Servers and File Sharing Services" because you are uploading your attachments to dropbox. But it's OK not to upload > 100 MB simulation results to Edaboard.
Will anybody read it? I don't know.

I found another way of calculating the losses.
1.) Set up faces on those places in the model where the power should be calculated
2.) Set up a power monitor
3.) Solver run
4.) Calculate the integral of the power field calculated by the power monitor on the faces.
You can do this by "Template Based Post Processing" ->"2D and 3D field results" -> "Evaluate Field on Face" and chose the face and the power monitor as the field which should be evaluate. After that click on "evaluate" and you will get the integral value which corresponds to the total power. This works well for my model...
This method is described in a more detailed way in the following link: https://www.cst.com/content/events/d...t_euc_2012.pdf
If the mesh number is too high the simulation could take a lot of time since we use a power monitor for this method.
Maybe there's an easier way of calculating the power. I will look for another method. It would be nice if someone could describe his method if he knows of another way of calculating the power on different faces.
The problem concerning the F-Parameters:
I think I get the problem (higher losses than expected) since the reference signal is just a rectangular signal in the time domain whereas the output signal in the port is gaussian. Normally for the S-Parameters a gaussians function is taken as reference, but in case of a gaussian excitation a rectangular signal is taken as reference, which might lead to the high losses - I'm not sure.
My question is: What is the definition of the F-parameters. How can I find out the power/ losses with the help of F-Parameters while using a gaussian excitation as source?
Thanks in Advance