Nice piece kit for 20 bucks
To give some background on the fiber menu you showed in the video:
MM = multi-mode fiber
SM = single-mode fiber
SM is typically used for long(er) distance connections, up to 100-s of km. MM is up to a couple 100 meters.
On MM you normally see optical drivers at 780 or 850nm wavelength, this is dark red to the eye (but don't go and stare into laserbeams please...)
on SM you see 1310 or 1550nm wavelength drivers, this is infrared. Even while invisible to the naked eye, DON'T ever look into them, or into a laser that might carry laser light. SM fibers often carry considerable higher optical power than MM. You have 2 strikes on a high-power laser, one for each eye...
OK.. that said something about the diameters listed.
50/125 means a 50micrometer inner glass core, covered in a 125micrometer cladding. This is MM fiber. MM fiber can be graded index, or step-index. The difference is the 'abruptness' with which the optical index changes going from the core to the cladding.
50/125 MM you see being used for FibreChannel and Ethernet type connections. 62.5/125 MM is older style cable, they were used for FDDI rings and the like. 9/125 is SM cable. Oh, SM is much trickier given the very small inner core, 9 micron is really quite tiny.
Enjoy the toy!