
rate doubling, (3) dispersion tolerance decreasing by 6 dB for each data rate
doubling, (5) in-line optical filtering, and (4) system software upgrades.
12.4.5 Optical Amplifiers
Optical signal loss in metro networks accumulates from three components: trans-
mission fiber, optical components embedded in the frequent add/drop nodes, and
passive fiber segment connections. Metro networks are generally deployed in very
active environments, and while not very long, they are subject to frequent mechan-
ical disturbances and breaks. Metro network fiber accumulates passive loss due to
frequent repairs and splicing.
There are three main optical amplifier choices ...