it sounds like a joke that we use a device cost less than 1 $ to test fiber cable. a LED(Low Emitting Diode) with 2 1.5V AAA bateries while solving fiber cable problem..
anybody knows that in information technology filed. there are 2 types of fiber cable, multi-mode fiber and single mode fiber cable.
multimode is what i we use very often as it is suit for low cost, short distance connection. usually less than 5 Kilometer.
it use LED device to send/receive the light.