Fiber-Optic Communication

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Fiber-optic Communication refers to the transmission of information using pulses of light sent over an optical fiber. An optical fiber is a very thin fiber of plastic or glass that has a core and a cladding that promotes internal reflection, allowing it to carry light along its length. The pulses of light are modulated to carry the information. Fiber-optic communication systems were first developed in the 1970's, and have replaced conventional communication methods using copper wires in critical networks in many countries. Today, fiber-optic communication has found many applications, primarily in the realm of telephone, internet, and cable TV transmissions.

Fiber-optic communication basically consists of the following steps: 1) an optical signal is created and sent by an optical transmitter through the optical fiber; 2) the optical signal travels over the fiber, which is designed to minimize distortions or losses in the signal; 3) an optical receiver at the other end of the fiber recovers the optical signal; and 4) the optical signal is converted into an electrical signal for final use.

Based on this process, a basic fiber-optic communication system consists of: 1) an optical transmitter that converts an electrical signal into a digital optical signal and transmits it; 2) a system of routed fiber-optic cables that contain the bundles of optical fibers carrying the light signals; 3) optoelectronic repeaters and optical amplifiers to make up for optical transmission losses; and 4) an optical receiver that converts the received optical signal into an electrical signal.

Figure 1. Photos of bundles of optical fibers (left) and fiber-optic cables as used in a telephone system (right)

Optical fiber systems result in much lower attenuation and interference than copper wire systems, making fiber-optics the medium of choice when it comes to long-distance and high-demand applications. Unfortunately, fiber-optic systems are also more complex and expensive, not only in its installation but also in its maintenance. The relatively high cost of fiber-optic communication systems prevented its quick and massive deployment in many cities around the world. Nonetheless, the manufacturing costs of fiber-optic systems have continued to decrease in recent years, making such systems more and more cost-effective relative to copper-based systems.