When a beam splitter divides the incoming light, some of the energy is inevitably lost, leading to a decrease in signal strength. It is a crucial part of many optical experimental and measurement systems, such as interferometers, also finding widespread application in fibre optic telecommunications. a laser beam) into two (or sometimes more) beams, which may or may not have the same optical power (radiant flux). They come in three basic forms: plate, pellicle, and cube.