There are currently five types of OM fiber—OM1, OM2, OM3, OM4 and OM5. OM1 fiber was the de facto choice for fiber throughout the 1980s and 1990s, and was still installed into the early 2000s. OM1 has a core diameter of 62.5 µm while OM2, OM3, OM4 and OM5 all feature a 50 µm core.
