Ever need to know if the IR LEDs in your UniFi Camera are operating? How about seeing if the SFP is putting out light or not? Or if you're getting light transmitted down the fiber you just installed LC connectors on? Turns out the piece of test equipment you need is probably in your pocket right now...
The camera in your smart phone is actually sensitive to Infrared light (just like the G3 camera above). But unlike a full-fledged camera, most Smartphones don't have an IR cut filter - not enough space and it's really not needed. This means it can see infrared which your eye can not. So just point your camera at the IR source and see if it shows up
This is a photo of an SFP module plugged into a switch - an 850nm MM one in this case. And again the IR clearly shows up as a red dot. And this works with nore than just MM units:
Here is a SingleMode 1310nm SFP - smaller red dot, but it's clearly there. Much smaller because this is single mode, but still clearly visible.
Works at the fiber end too - the camera picks it right up. No more guessing if the cable is good or if there's light getting all the way to your end - you can clearly see it. And this works with any IR device you have - want to see if the TV remote is working?
A general warning - never look directly into the SFP port with the naked eye, especially single mode ones - the IR level can damage your eye. But with the camera that issue goes away. I wouldn't shove the fiber end right into the camera lens, but leaving a few inches allows enough dispersion that it's safe.