The Y70 Fusion Splicer is capable of splicing SM MM DS NZDS EDF EXF fibers, but what do all these letters mean?

SM and MM are just Singlemode (also known as G.652) and Multimode, and are most common to Datacoms applications.

The others fiber types are specific to Telco applications, where they are looking to extend the distance or the bandwidth.

DS is Dispersion Shifted fiber. Whereas standard SM fiber has zero chromatic dispersion near 1310 nanometres, fiber doping and additional cladding enable a shift to the 1550nm range.

NZDS (also known as G.655) is Non Zero Dispersion Shifted fibre. It has its zero dispersion wavelength either around 1530nm or 1570nm.

EDF is Erbium Doped Fiber. EDF has broad, flat performance spectra required for high efficiency in DWDM (multiple signals over the once fibre.