These beamsplitters are created by coating the hypotenuse of dual prisms with a partially reflecting material and joining them with optical or epoxy cement. A beam splitter or beamsplitter is an optical device that splits a beam of light into a transmitted and a reflected beam. It is a crucial part of many optical experimental and measurement systems, such as interferometers, also finding widespread application in fibre optic telecommunications. Sample and Reference Paths: The sample path passes through the substance being analyzed, while the reference path does not.