Move the cursor in the LDE to Surface 3 to highlight the exit port within the 3D Layout.  It is apparent from the 3D Layout that the rays are being terminated at the exit port, which is a good indication that the positioning of the exit port is invalid.

The position of the exit port is controlled by the Exit Loc X, Y, Z and Exit Tilt X, Y, Z parameters on the NSC surface in the LDE.  Currently the Exit Loc Z is set to 50mm, while all other position and tilt parameters are set to zero.  The locations and tilts are relative to the entry port.  Since the Z length of both the core and clad are also 50mm, the exit port is currently co-located with the back face of the fiber.

The exit port must be separated by at least the Glue Distance from any portion of the non-sequential objects.

For the purposes of this design, it is not critical to place the exit port so close to the back face of the fiber.  We may simply change the Exit Loc Z of the exit port to 50.5, and absorb this added thickness by changing the Thickness on Surface 3 by -0.5mm.  Update the 3D Layout to verify that these changes did indeed affect the ray trace.

Lastly, turn the Ignore Error flag OFF from the NSC Editor menu to ensure that the geometry error has been fixed due to the changes that have been made.  Once the Ignore Errors flag is turned off, press Ctrl+Shift+U to update all windows.  ZEMAX should no longer issue a geometry error, and rays can now be evaluated at the image plane.