Amplifiers and Repeaters
Although fiber optic cable is often chosen over co-ax because it can transmit signals over longer distances, there are certainly limitations to how far fiber transmission systems can carry a signal without amplification.
When the desired transmission distance exceeds the maximum distance that a system is designed to support, amplifiers or repeaters are required.
In an AM- or FM-based system, amplifiers are used to boost the strength of an attenuated signal so that it can be transmitted along an additional length of fiber.
Fiber-optic amplifiers are very similar to their traditional electrical counterparts. The transmitted light beam is captured by the amplifier, converted back to a voltage for amplification purposes, and then relaunched as light for transmission over the next span of fiber.
As in copper-based systems, fiber optic amplifiers do pass on any distortions and interference that have been acquired by the signal throughout the transmission, and those distortions are amplified along with the signal.
Therefore, if a signal is amplified enough times, it will become greatly distorted.
This problem is eliminated when using a digital transmission system, as transmission length is extended through the use of repeaters instead of amplifiers.
When a fiber optic system uses digital signaling techniques, a repeater converts the transmitted light beam back into its electrical equivalent, in digital format, and then launches a brand new fiber-optic signal based on the regenerated digital electrical signal. (Note that the signal does not return to its baseband format until it reaches its final destination.)
Because of the digital nature of the transmitted signal, no distortions are picked up by the repeater or passed on in the repeating process. Therefore, theoretically, digital repeaters could be used to transmit a signal over an infinite length of fiber.
This is a significant advantage over traditional AM and FM systems and is not limited to systems designed for the transmission of digital baseband signals. Today, there are fiber-optic systems that use all-digital signaling and processing to transmit traditional analog video, audio and data signals, and do so at a competitive price.
Summary
With a little practice, laying and terminating fiber cable should become just as simple as using co-ax, and the advantages are innumerable.
For more information on fiber optic technology, read the educational guides Introduction to Fiber Optics, Fiber Optic Cables and Connectors and Advantages of Digital Fiber Optic Systems, available at the Communications Specialties website.