Coupling into multimode fibers

For fiber coupling, either the fiber couples type 60FC-A19.5 or the collimators of type 60FC can be used.
If a collimator is selected then it can be used for fiber-coupling by using it in reverse mode and placing it in an adjustable mirror mount (or other mechanics providing the same degrees of freedom). This gives all degrees of freedom to achieve a high coupling efficiency.

Selection of coupling focal length for a circular beam

When using a multimode fiber, the coupling focal length is calculated from the beam diameter and the nominal fiber NA

{!{!{f\prime=\frac{0.5\cdot\emptyset_{beam}}{NA}}!}!}
A coupling focal length too long can cause insufficient mode mixing, resulting in unwanted beam characteristics, while a focal length too short will reduce the coupling efficiency.