Open the file "Samples > Physical Optics > Fiber Coupling.zmx". This file demonstrates the use of the Physical Optics Propagation capabilities of ZEMAX to compute fiber coupling.

Observe that fiber coupling information is listed at the bottom of the POP window that opens with this file (make sure "Use Session Files" is checked). Presently, the coupling is excellent with an efficiency that exceeds 99%!

 

The beam being coupled, as shown in the "Beam Definition" tab of the POP window settings, is a Gaussian beam with a waist size of 2 mm. To see how the receiving fiber is defined, take a look at the "Fiber Data" tab of the POP window settings. Observe that the receiving fiber mode is Gaussian and has a waist of 8 microns. Notice also that the "Compute Fiber Coupling Integral" is checked. ZEMAX will only display fiber coupling information if this box is checked. Otherwise, pilot beam data will be displayed at the bottom of the POP window.



To simulate coupling into a narrower fiber, try changing the receiving fiber mode. In the "Fiber Data" tab, change "Waist x" and "Waist y" to 0.004 and then click "OK". The coupling will be recomputed.



As expected, coupling into a narrow fiber has reduced the efficiency.

TIP:  Users of the full, licensed version of ZEMAX can optimize fiber coupling based on Physical Optics Propagation calculations using the FICP merit function operand

Licensed users can also explore single-mode fiber coupling in further detail in the Knowledge Base article, "How to Model Coupling Between Single-Mode Fibers".