Attach to the light source launch to the splitter and attach a receive launch reference cable to the output and the optical power meter, and then measure the loss. Non-polarizing beamsplitters are specified by their splitting ratio, i. Analogy: A beam splitter is like a fork in a river that channels part of the flow one way and part another, with some loss. 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.