Fiber optic cables come in several sizes, which can confuse new users.  The most common three are 62.5/125 and 50/125, which are multimode, and 9/125, which is single mode.  The difference between the three is actually crucial when using the cables to connect equipment.  Use the wrong cable type and you risk intermittent or completely dropped connections. Fortunately, most equipment is pretty specific about what type to use.  Do you have a question about fiber optic terminology?