In this section, we begin by opening up ZEMAX.  Choose File...Open and then go to the Samples/Physical Optics folder to open Fiber Coupling.zmx.  You can select any of the analysis features, including the 2D layout to see how the rays focus to a point. 

Figure 1: ZEMAX setup for fiber coupling lens

Select Analysis/Physical Optics/Physical Optics Propagation to see a 2 mm input waist Gaussian being focussed at the image plane of the lens:



Figure 2:ZEMAX screen with field pattern

From here we can tell ZEMAX to output the beam files we will need to convert into the RSoft format.  Press the Settings option on the top of the physical optics propagation window and then select the Display tab and click on the Save Output Beam To: option.  Next, set the name of the file to be Fiber_output.zbf.  Press OK.

 
Figure 3: Display settings for physical optics propagation

These files are typically saved in the ZEMAX/POP/Beamfiles directory so you can find the file there.