At a casino where I was a slot tech we used fiber optics that went into a fiber converter module and then RJ-45.

Often I would look at the ends of the fiber connectors to see if they were lit or if the light looked odd.

They were quite low in power but I'm surprised at myself that I didn't think of the risk.

edit: optics not options

Patch fiber is usually using Class 1 or Class 1M lasers which are entirely safe to look at. Also the light spreads out very rapidly at the end of an unterminated fiber because there's no lens to focus it. So don't hold it directly up against your eye but like a foot away is fine. The lasers are less focused (i.e. cheaper) and the multi-mode fiber is wide so it spreads out very quickly. You can't actually see the IR light, the red light you see is just sidebands of the signal.

Fiber used for long hauls is much more powerful but uses a wavelength that the human eye is very good at blocking (so your eye dissipates more of the energy but what does get through could damage your retina). There are systems that will decrease the power if the link is lost (cut or unplugged) to protect eyes. The light will still dissipate in free space (because there's no lens) so you should be safe from a distance. Single-mode fiber uses a more focused laser and more narrow fiber so it will spread less over a free space distance so don't get too close.

Always better to just use a light meter (or a phone camera) if you're unsure but also just holding the end of the fiber against some paper or your palm may reflect enough of the visible light to let you know the fiber is live.

Just in case, always use the same eye to look into these things.

"Do not look into laser with remaining eye"

As an intern moving data centers the old networking guy told me to look into them; I used my right eye and now my eye is 20/40 a decade later whereas my left eye is still 20/20. I did hold it up to my eye because it was hard to see..

Some scientists used to look at the beam emitter to adjust the aim of old particle accelerators. The story I heard was that some of them eventually developed cataracts as a result. Come to think of it, with today's medical technology that's a lot less awful than punching holes into your retina with a laser, but I think the result back then was eventually blindness.

I met a scientist who looked into a particle accelerator; it was intention, part of a self-experiment to establish whether high energy particles can cause scintillations in the eye. In his case he very carefully calculated how to get a safe dosage.

On the other hand there's https://en.wikipedia.org/wiki/Anatoli_Bugorski

“Low power” lasers are sometimes wildly more powerful than they claim to be. I guess what do you expect when you buy a Chinese laser pointer on Amazon for 5 bucks.

Nd:YAG lasers such as the one in the article use an IR exciter into a crystal to achieve frequency doubling or tripling. Much of the energy from the fundamental exciter makes it past the crystal, so without good filtering, a "safe" class 2 or 3R laser can still produce blinding (but invisible) light. Lots of the cheap lasers don't have good filtering, so be careful what you buy.

Don't forget that the power rating of a laser pointer (unlike literally every other type of light you buy) is the output power, not the input power! More importantly, it's the output power of only the green laser!

The 1064nm exciter laser is pumped by an 808nm pump laser, and based on what I know about how inefficient lasers are, I can guarantee that those beams are way more powerful than the output beam! If those leak because the manufacturer cheaped out on filters, those lasers mat not visible, but they are still dangerous!

Oh yeah, that’s a real problem for cheap green lasers. IR diode laser, doubling crystal, and no IR filter is a good way to go blind.

One of the things I hate most in tourist hotspots these days are the people selling high powered laser pointers, normally selling them to kids, and they are shining it at their faces, in the faces of others, and at the neighbours.

I swear they never used to be so commonplace.

Having worked nightclub lighting a long time ago I have a deep appreciation for laser safety haha

When I was ~12 years old one boy pinned me down and another one shone a laser pointer in my eye just for fun. Needless to say, this has been my „bad eye“ ever since (I’m 39 now)

That's terrible, and I'm guessing they faced little if any consequences for it. I'm mad thinking about this, even though I wasn't involved and it was 27 years ago.

I would like to think that people would know today that laser pointers are weapons so this wouldn't happen, and that if it did happen, the schools' zero tolerance policies (the ones that you hear about used to stupidly expel someone for bringing a butter knife to eat their lunch with) would kick in, as school bullies literally damaging your body for life is completely unacceptable.

Not gonna lie: I would probably devote my life to revenge if someone did that to me. And this is the honest truth so y'all can stop flagging this, Jesus Christ...

Out of your ten comments, half are flagged. I propose that the lesson to take from that is to reread the guidelines¹ and adapt, not triple down on the same thing and complain.

¹ https://news.ycombinator.com/newsguidelines.html

And it would be a wasted life, just ask Jesus.

A friend of mine gave me a high power blue laser pointer, and it was fun for a night but I gave it back to him because I recognized that it was just too dangerous. One slip, one stray reflection, and I'd damage my eyesight or go blind. It's just too dangerous, and I'm a very careful person who takes precautions - I can't imagine kids with laser pointers are going to be able to see very well when they are older.