Optical Fiber Telecommunications VA, 5th Edition

850 m (nonlinearity  = 20 W/1 km), BPF2 width of 0.5 nm centered at 1558.0 nm.

The amplifier boosts the noisy pulses up to a peak power level of 500 mW, sufficient

to induce XPM on the clock. The regenerator is followed by a variable attenuator VA2

to ensure the peak optical power is constant at a relatively high 2 mW, where shot and

thermal noises are negligible as verified by the BER being <<10

–13

(no errors) with

no ASE added. In contrast, with ASE noise we obtain 10

–10

< BER < 10

–2

, depending

on the OSNR. Signal spontaneous beat noise is the most prominent source of noise

when ASE is present. Figure 20.23 shows an improvement in BER from 3 10