Abstract:
With the increasing demands on the capacity of WDM systems, cross-phase modulation
(XPM) has become the most significant nonlinear effect and limits the system
performance. On the other hand, group velocity dispersion (GVD) is one of the linear
effects in the optical fiber that also restricts bit rates. As a result, the combined effects of
GVD and XPM may cause further deterioration of transmission performance in a WDM
system. In this research work, an analytical model for a WDM system is developed
incorporating the combined effects of XPM, first- and second order GVD. The crosstalk
expression for the affected channel is derived in terms of system parameters for
standard single mode fiber (SSMF), dispersion shifted fiber (DSF) and large effective
area fiber (LEAF).
The spectral characteristics are strongly dependent on the channel spacing and GVD of
the fiber i.e. the crosstalk effect is more at narrow channel spacing and lower GVD. It is
found that at 10 GHz modulation frequency and 0.8nm channel spacing for 100 km
distance DSF suffers XPM crosstalk penalty 23 dB and 16 dB more than SSMF for first
order GVD and second order GVD respectively. The crosstalk effect due second order
GVD is found insignificant in presence of first order GVD in single span system, but at
high bit rate and long haul first order GVD compensated system, the effect of second
order GVD become significant and play a critical role in limiting the system
performance. Simulation results show that system suffers maximum penalty due to
XPM effect at zero dispersion coefficient and XPM interference is linearly dependent
on optical power of the injected signals in a very large range of system parameters. It is
also found that system bit error rate and eye opening penalty is high at higher value of
GVD. Among the 3-types of fiber, SSMF contributes least amount of XPM crosstalk
for the same amount of pumps and probe power. Thus the findings of this thesis can
predict accurate amount of crosstalk due to XPM and may be useful to design a WDM
optical communication system.
