ss costly to maintain once they are installed. This is because bits are carried on non- electrical light pulses. These pulses are analogous to the light emitted by quickly turning a flashlight on and off. Because the pulses are non-electrical, there is no resistance from electromagnetic interference (EMI). Resistance associated with EMI in networks made up of copper cabling causes fading over relatively short distances of about 2 miles. This is analogous to water www.TechnicalPDF.com pressure from a hose weakening over short distances. Consequently, amplifiers are needed every mile and a half to 2 miles to boost electrical signals carried on copper-based networks. The absence of resistance from electrical interference is fiber's main advantage over copper cabling. Moreover, once installed, amplifiers must periodically be replaced and maintained. Because data on fiber-optic cabling is carried as non- electric pulses of light, amplification is only needed after 80 to 120 kilometers (49 to 74.4 miles). This means that in many short fiber runs to homes or apartment buildings, no amplification is needed. In long-haul networks, those between cities, states, and countries, fewer amplifiers are required to boost optical signals after they have faded than are required in copper networks. The non-electric light pulses on fiber-optical cabling can travel about 400 kilometers, or 248 miles, before having to be regenerated. This is another savings in labor because fewer technicians are needed to install regenerators. This lowers the cost for network providers who lay miles of fiber between cities, within cities, and under the ocean. In short fiber runs, regeneration is not needed if the cable runs are less than 4,000 kilometers. Lighter and Smaller than Copper Cabling In addition to the absence of electrical interference, fiber-optic cabling is lighter and smaller than copper cabling. Because of its size, it takes up less space than copper cabling in conduits (hollow pipes in which cables are run) that are located under stree