Position the "beam splitter" at a 45° angle to the laser beam, atop the marks on the interferometry table. There should now be two sets of bright dots on the viewing screen; one set comes from the fixed mirror (adjustable mirror) and the other comes from the movable mirror. It is a crucial part of many optical experimental and measurement systems, such as interferometers, also finding widespread application in fibre optic telecommunications. This article and its illustrations will go a long way toward making the correct choice less of a risk. All curves show typical performance. An optical distribution network (ODN) mainly has primary splitting and secondary splitting, or centralized splitting and cascade splitting.