An optical multiplexer!
Video 1. Control Light with Sound! by Les' Lab (2021) Source.
Video 1. Fabry Perot Interferometer by JFC UCL (2016) Source. Description only, reasonable animations. Considers the case of two nearby beam splitters.
Video 2. Fabry-Perot Introduction by Williams College Physics (2020) Source.
Shows a working device. Confocal optical cavity, one of the mirrors scans back and forward moved by a piezoelectric motor, this is called a "scanning Fabry-Perot interferometer".
Does not produce an interference pattern, only an on/off blob, which is then fed into an oscilloscope for analysis. The oscilloscope shows both the mirror displacement (which is given by a voltage) and the light detector output.
Video 3. Aligning a Scanning Fabry-Perot Interferometer by University of South Florida (2016) Source. Very detailed, and shows of some nice equipment and techniques.
Figure 1. Source.
Video 1. The Story of Light by Bell Labs (2015) Source. A ultra quick and Bell Labs focused overview of the development of optical fibre.
For example, that is how most modern microscopes are prototyped, see for example Video "Two Photon Microscopy by Nemonic NeuroNex (2019)".
This is kind of why they are also sometimes called "optical breadboarbds", since breadboards are what we use for early prototyping in electronics. Wikipedia however says "optical breadboard" is a simpler and cheaper type of optical table with less/no stabilization.
Video 1. A simple refracting telescope built on an optical bench by plenum88 (2013) Source.