Single-mode and multimode optical fibers cannot be directly fused together due to their different core diameters. Glass can carry the signal a greater distance, but plastic is cheaper. It is possible to connect the two different cable types; however, a media converter must be used to adapt the core sizes and optical. But what happens when you need to connect an existing multi-mode campus network to a new single-mode service provider link? You can't just splice them together. This is where fiber conversion comes in. Mechanical Splicing: With this. Installing an optical cable involves selecting the right fiber type, carefully routing it without damaging the glass inside, terminating the ends with connectors, and testing the finished link for signal loss.
[pdf] A theoretical analysis shows that the effect occurs in both single-mode and multimode fibers and depends on fiber end face separation, the source spectrum, and the modal power distribution in the fiber. Multi-mode optical fiber is a type of optical fiber mostly used for communication over short distances, such as within a building or on a campus. Multi-mode fiber has a fairly large core diameter that enables multiple light modes to be. Multimode fibers are fibers having multiple guided modes at the operating wavelength — sometimes only a few (→ few-mode fibers), but often many. This is made possible by its relatively large core diameter, typically 50 or 62. 5 microns, compared to the ~9-micron core in single-mode fiber. (Basically, what we have just described is wavelength division.
[pdf] 
