I printed a few parts to route fiber optics, once upon a time. I'll start by pointing out these were the first (real-use/not for fun) parts I ever designed to be additively manufactured, and the first that I wasn't doing the printing myself or able to iterate. I did the design, shopped them out to a print house, and paid dearly (several grand each) for them because they were pretty large. If I were to attempt it now, I'm confident it would work out a lot better.
I had a really hard time getting anything to come close to even holding on tight, much less providing any type of seal. The fiber optics I was using were very high end, and very consistent in OD. My design parameters dictated a two-piece clamshell to clamp the fiber optics in place. The material shrinkage from one side of the clamp to the other was extremely inconsistent, and varied pretty widely from hole to hole. There were about 12 light pipes running through the clamp, and every hole on three of the clamps was a dramatically different fit. Some had to be drilled out, some were horribly oversized. Ultimately, the pieces went in the trash and I came up with an ugly Rube Goldberg solution for free, and counted myself lucky to not lose my job over the money wasted haha.
Like I said, I guarantee somebody who has half a clue about printing could do a far better job of the design than I did. If you also control the printer, you'll be more able to control the results as well.
I do think you'll have a hard time printing anything that will seal right off the printer. If anything, I'd print the holes slightly oversized and epoxy your fiber optics in place after the fact. This is how we do it to make vacuum tight passthroughs in aluminum, pulling moderate vacuum to a few tens of mTorr.