Simplex Adapter: A simplex adapter allows the connection of two individual fibers, enabling a single-channel transmission. It is commonly used for single-mode or multi-mode applications where a single fiber connection is required. Note that the term fiber coupler is used with two different meanings: It can be an optical fiber device with one or more input fibers and one or more output fibers. Light from an input fiber can appear at one or more outputs. Thorlabs offers a varied selection of single mode (SM), polarization-maintaining (PM), multimode (MM), and double-clad fiber couplers, as well as 1x8 and 1x16 SM PLC splitters; 1x4, 1x8, and 1x16 PM PLC splitters; wideband multimode circulators; RGB combiners; and WDMs. The fibers are heated and pulled until they stick. This lets light move between the fibers.