Abstract:
The combined effect of crosstalk and noise on Bit Error Rate (BER) of a multi-hop
Wavelength Division Multiplexing (WDM) transmission system with Limited Wavelength
Interchanging Cross Connects (L-WIXC) are investigated in this thesis. In an all-optical
WDM network, the route to be followed and the wavelength to be used by the signal along
the selected route is designated by an L-WIXC. But, propagation through the switching
elements of an L-WIXC results in signal degradation and induces crosstalk both due to
device intrinsic losses and their imperfect operation. Moreover, in a long-haul
communication system, the cumulative loss of signal strength is restored using optical
amplifiers which further degrade the signal due to spontaneous emission that adds noise to
the signal during its amplification. In this thesis, the signal to crosstalk plus noise ratio at
the receiver output of a multi-hop WDM network is derived for various L-WIXC
architectures. An improved mathematical modelling is developed for the analysis of
network performance in terms of BER and the mathematical formulations are then used to
evaluate Bit Error Rate (BER) performance of the system in terms of parameters like
number of hops, number of wavelength channels per fiber and number of fibers.
Accordingly, the power penalty for different system parameters due to accumulated
crosstalk and noise is determined at a given BER of 10-9. Results show that there is a
significant power penalty due to accumulated crosstalk and noise depending on the number
of hops. Subsequently, the maximum allowable number of hops that a signal can travel,
sustaining a specific level of power penalty for any combination of wavelength channels
and input fibers, is evaluated numerically. A Comparative study of the system performance
is also depicted for all architectures of L-WIXC which will provide a guideline for system
design in choosing the most effective one while designing a WDM network.
