alt Hacker NewsI was a fiber installer once upon a time in the 00s. A guy I worked with who was "the splicer" for our team and has years of experience using the little easy bake oven thing swore by going off the smell to know when it's "ready". Probably not the greatest thing for your health considering he did at least 10-12 of these a day.
Modern fiber splicers are fully automatic, so you don't need to smell :-) The only thing that's still mostly by hand is the cutting (mostly stripping away the various layers of insulation).