What is 50-125 62.5-125 9-125?

Here can be divided into single-mode and multimode when the light transferring through optical fiber. The multimode fiber core diameter has two specification 50μm and 62.5μm. The outer diameter of the cladding is 125μm, so here comes out 50/125μm and 62.5/125μm. For the 9/125μm, it’s under the single-mode.