In MMF, the diameter of the core is larger than SMF that is 50 to 100 microns. Also, multiple modes of light can be propagated through the fiber optic path. Due to large core of MMF, coupling light becomes susceptible. MNIF uses inexpensive light emitting diodes (LEDs) as light sources. MMF can be classified into two types, such as graded-index and stepped-index, on the basis of refractive index. In the graded-index MMF, the refraction index of the core gradually decreases toward the outside of the core while increases toward the center of the core. This property results in abbreviating the modal dispersion of a signal. On the other hand, in the stepped-index MMF, the refraction index of the core remains uniform but with a small reduction at the core-cladding interface. Also, a lower bandwidth is supported by the stepped-index MMFs in comparison to that of the graded-index MMFs.
MMFs are available in various sizes. The mostly recommended MMF size for networking is the 62.5/125 micron where 62.5 deals with the core diameter and 125 specify the cladding. However, some other common NINIFs sizes are 50/125 microns and 100/140 microns. In addition, MMF supports a segment length of 2000 meters for Ethernet having a data transmission rate of 10 and 100 Mbps. It can also support segment length of 550 meters for Ethernet having a data transmission rate of 1Gbps.