Fig. 7.
and (b) corresponds to trace (b) in Fig. 6.
XPM power transfer functions: (a) cotresponds to trace (c) in Fig. 6
Ia order to understand better the features in the timedomain
waveforms obtained with different system configurations,
Fig. 7 shows the XPM power transfer functions in the
frequency-domain corresponding to the trace (b) and the trace
(c) in Fig. 6. In the single span case, the crosstalk indeed has
a simple high-pass characteristic. For the three-span system,
however, the XPM power transfer function has a notch at
the frequency close to the half bit rate, which suppresses the
crosstalk of “OlOl” bit pattern in the time-domain.
It is worth mentioning that the crosstalk waveforms shown
in Fig. 6 were calculated before an optical receiver. In reality,
the transfer function and the frequency bandwidth of the
receiver will reshape the crosstalk waveform and may have a
strong impact in the system performance. After introducing a
receiver transfer function, XPM induced eye closure “eyeclo”
in the receiver of a system can be evaluated from the amplitude
in the crosstalk waveform for the probe channel. The worst