Fiber Optic cables are key aspect of modern age as they play a major role to transmit data from one country to many other nations on the globe. We hear the term Fiber Optics whenever it concerns with telephone system, Internet or the cable TV system. Unfolding the cables, we get tiny strands of optical pure glass that are arranged to carry digital information to long distances with the amazing speed of multi-terabits per second. Fiber Optics cables have several advantages over traditional metal cables. This article will light on how Fiber Optic cable functions? The basic working principle whether it is glass or plastic fiber is the same. An optical transmitter, LESAR or LED diode, sends light signals in the core, the hallway path where the pulse travels, the light bounces off the cladding (mirror coated) walls of core, a phenomenon known as Total Internal Reflection and ultimately reaches at the other terminal, where the signal are received. The Total Internal Reflection sends down 100 percent of the signals transmitting form one side as cladded core doesn’t absorb any wave of light, hence the signals can travel on amazingly long destinations. However, one thing should be noticed that if the glass contains any impurities the signals could be degrade, depending upon the extent of impurities. Taking advantage of total internal reflection scientists are able to send data over large distances, for instance Trans-Pacific Fiber Optic or Trans-Atlantic Fiber Optic. The parts of Fiber Optics are organized as follow, Core: Tiny strands or fibers of glass center, where the light travels Cladding: The outer optical material surrounding the core, it bounds light in the core. Jacket: The external protective coating, usually of PVC, that protects fiber from damages.