(Caution: Fibre Optics use lasers, don’t look into the SFP, Optics or patch leads)
Ever wanted to know if your optics are working and you don’t have a fibre optic tester to hand? You can use the camera on your mobile phone. We always have that in our pocket these days.
Point the camera at the device ….
TaDa, you can ‘see’ the TX laser.
Note that this only works with Multimode optics ~850nm. Single mode optics tend to be beyond the range, but these digital cameras have good sensitivity to infrared, far greater than the human eye.