A beam splitter is a device that splits a single beam of light into two or more beams. However, there are several other synonyms for "beam splitter". One of them is "optical splitter", which is a common term used in the field of fiber optics. Another synonym is "optical coupler", which is also a device used in fiber optic communication. A third synonym for beam splitter is "dichroic mirror", which is a type of mirror that reflects certain wavelengths of light while allowing other wavelengths to pass through. Lastly, "beam combiner" is another synonym for beam splitter, as it is a device that combines two or more beams of light into a single beam.