How a fiber optic cable works and how to test it with a laser

Today, fiber optic cable is increasingly used to transmit the Internet signal, replacing the twisted pair cable. The signal in the fiber optic cable is transmitted using light (photons) that is modulated by a useful signal. Unlike the twisted pair cable, the signal via fiber optic is transmitted at a much higher speed and is not subject to electromagnetic interference, and the signal can also be transmitted over long distances

The basis of the fiber optic cable is the optical fiber, it is through it that the light is propagated by means of internal reflection. The optical fiber is similar to a fishing line and if you gently break it, you can feel a crunch, and the crunch is the core - quartz glass. The light propagates through the core of the optical fiber and is reflected from the shell

To test a fiber optic cable, I assembled a simple light source - a laser from a DVD-RW player, connected three optical fibers into a bundle and directed one end of the fiber to the laser and the other to the photodetector, modulating the laser with sound. The photodetector is connected to an amplifier and when it is illuminated, sound will be heard from the speaker. Using a powerful laser, you can test fiber optic cables

The fiber optic cable must not be bent at a certain angle, pressed on it, otherwise the fiber optic can be damaged. The photo shows the damaged fiber optic cable

Using fiber optics, light can be transmitted into a dark bunker. One end of the cable is directed towards the sun on the outside and the other into the dark room