Using light pulses sent along a flexible glass strand, fiber optic cables transmit data and signals faster and with increased bandwidth compared to traditional copper or aluminum cables. Accommodating a wide range of data transmission applications and able to send data over very long distances, optical fiber provides a popular choice for analog and high-definition televisions, telecommunications and networking industries.
The term fiber optic cable encompasses two types: a single-mode cable consisting of one glass fiber per cable and a multi-mode cable of two or more strands. Stronger than steel, fiber optic cable resists a high pulling tension of eight times that of Category 5 coaxial cable. Using a lens, the fiber optic cable guides light sent from a transmitter, consisting of either an injection-laser diode or a light-emitting diode, along its length as the light source pulsates on and off. A light-sensitive receiver on the terminating end converts the light pulses into digital data identical to the original signal.
Single-mode cable comes in diameters of 8.3 to 10 microns, where 1 micron is the equivalent to 1/250th the diameter of a strand of human hair. Larger multi-mode cable allows for diameters ranging from 50 to 100 microns, not including the thickness of the surrounding layers of protective material used to strengthen and buffer the signal.
A thin layer of fiber cladding covers the the inner core of single or multiple glass fibers in each cable and acts as a boundary to contain light waves, enabling their refraction and transmission along the strand. A thermoplastic overcoating, or buffer, and aramid strengthening fibers surround the cladding, helping to resist kinking and absorb shock, tension and crushing forces. Aramid is the yarn used in bulletproof vests. Finally, typically an orange, black or yellow PVC or fluoride co-polymer jacket covers the cable. Available at a lower cost, the optical fiber core of glass can be substituted for plastic fiber that performs like single-mode glass cable for transmissions along shorter distances.
Compared to copper cables, fiber optic cables cost less to purchase and maintain, though they require more expensive connectors than their copper counterparts. With a larger bandwidth capacity, fiber optic cable can operate at higher speeds of multiple gigabits while providing increased resistance to electromagnetic interference from radios and other cables. To fortify and refresh the light signal over very long distances, some fiber optic cables require light strengtheners, called repeaters, in certain situations.
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