A fiber optic coupler splits or combines optical signals within an optical fiber. Unlike fiber combiners, which only merge light, couplers can both combine and split signals. 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. Three fabrication methods are employed: fusion, micro-optics, and planar lightwave circuit. Within OZ Optics' series of beamsplitters and combiners, the two most common types of splitters offered are polarizing beamsplitters and polarization maintaining (PM) beamsplitters.