Specialty Optical Fibers Handbook

of nonlinearities across the entire system. Three critical aspects need to be

considered. First, precise dispersion compensation across the amplifier band-

width is crucial to permit cost-effective 40-Gbps transmission. This requires

excellent chromatic dispersion compensation and minimizing PMD. Second,

the contributions to nonlinearity from each element of the transmission line

must be considered, and the nonlinearity of the composite transmission line

should be minimized. Third, Raman amplification is a key enabling technology

for improving OSNR for high-bit-rate ultralong haul transmission.

5.5.1 Precise Dispersion Compensation

Pulse spreading due to the nonzero spectral width of the laser and dispersion

of the Tx fiber must be compensated in