tical fiber to be routed within a building without having to worry about the location of sources of elec- tromagnetic radiation, such as fluorescent ballasts. In addition, immuni- ty from EMI optical cable avoids one of the most common causes of transmission errors. Thus, you can normally expect a fiber-optic trans- mission system to have a bit error rate considerably lower than that achievable with a copper-cable-based system. Another advantage of the immunity of optical fiber from EMI is the fact that multiple cables in close proximity to one another do not gener- ate crosstalk as do copper cables. This means that multiple fibers can be bundled together without requiring special shielding and provides another option for the use of an optical transmission system. Low-Signal Attenuation In a copper cable signal, attenuation is directly proportional to frequency, with high frequencies attenuating more rapidly than lower frequencies. In comparison, the flow of light in the form of photons in an optical fiber does not exhibit the characteristics described above, and the attenuation in the signal is relatively independent of the frequency. In comparison to copper-based transmission systems, the lack of signal loss at high frequencies permits fiber-optic systems to transmit informa- tion for longer distances before requiring the signal to be amplified. Chapter One Environment Utilization In a copper-based system, the flow of electrons can result in a spark or shock. This means, for example, that the routing of copper cable in an oil refinery or grain elevator environment could result in an explosion if the wires short-circuit. In comparison, the routing of optical fiber through such locations prevents the risk of ignition caused by faulty wiring as light, instead of electrons, now circulates through the danger- ous environment. While only a small percentage of optical fiber may be used in refineries, chemical plants, and grain elevators, the use of optical fiber in an office environment is now commonly encountered and