They are really optical fiber splicers, “fusion” was coined early on to point out optical fibers are glass and a HV arc was required to melt, push together and “fuse” fiber into a single strand.
Early machines were huge with mechanical microscope viewers and needed a name as impressive as the price tag. In the early days there were no agreed standards for fiber manufacture so fusion splicer design moved from v-groove static designs, to more expensive “LID” (light injected), profile (fiber core edge), and core alignment versions – at one point we were paying as much as $20k per machine to “ensure” cores were aligned!
Odd how ribbon machine have alway been and will always be v-groove design and somehow produce “acceptable” loss results of .00 to .03 dB.
Since the turn of the century (17 years ago), manufacturing standards have been established and bulk fibers are pretty much uniform and all the extra gearing, calculation and views are pretty much a carry over mythical requirement. With a skilled cleaver and crimper, a mechanical splice will net you an average .3 to .7 dB loss when joining a fiber. With smaller, faster V-groove designs, and bigger core alignment machines, splices are easily 10 times better at .01 to .03 dB losses. This loss reduction is what installers and their clients are purchasing to reduce their loss budgets.
Did you know with the today’s typical MFD (core diameter) specification for single mode fiber at 9.2 ± 0.4 μm at 1310nm, even at the opposite extremes of this spec, losses due to core mismatch could only be as “large” as ≤ 0.033 dB?
Yet the core-alignment myth continues among non-real world installers. I had one manufacturer justify the need for core alignment in this decade with, “yeah, but if you combine a worst case MFD issue with a maximum core offset it would result in consistent 0.056 dB losses.” I think it would be more prudent to change bulk fiber vendors on the next job.