Optical Networking Best Practices Handbook

4.5. EXTENDING PERFORMANCE

There are difficulties in getting light to travel from point A to point B. This section offers suggestions on how performances can be extended.

4.5.1. Regeneration

While light in a fiber travels at about 200,000 km/s, no light source can actually travel that far and still be interpreted as individual 1s and 0s. One reason for this is that photons can be absorbed by the cladding and not arrive at the receiving end. Since increasing the power of single-mode lasers can decrease the output, it is necessary to extend the reach of the photons in the fiber through regeneration [1].

4.5.2. Regeneration: Multiplexing

This process of regenerating an optical signal can take two forms: optical-electrical-optical (OEO) or fiber amplifiers (FA). OEO systems, also called optical repeaters, take the optical signal, demultiplex it and convert it into electrical pulses. The electrical signal is amplified, groomed to remove noise, and converted back into optical pulses. It is necessary for it then to be multiplexed back on the line and continue on its journey. Regenerators are often placed about every 1500 miles [1].

4.5.3. Regeneration: Fiber Amplifiers

The second method of regeneration to extend the reach of photons is the use of FAs that convert the photons into an electrical signal, which is done by doping a section of the fiber with a rare-earth element, such as erbium. Doping is the process of adding impurities during manufacturing; a fiber-optic cable already ...