Review of Physical Layer Related Issues in WDM Networks: Part -Ⅰ

摘要

In order to increase the transmission capacity there has been a growing interest in WDM for optical networks. The factors affecting the physical layer of the optical network are the nonlinear effects, the necessity to have in-line optical amplification and the requirement of placing wavelength converters. This paper, which is the first part in a series of two, reviews the nonlinear effects present in optical fiber emphasizing those which result in degradation in WDM system. In-line amplifiers are used in WDM systems to overcome the losses incurred by the signal while propagating through the medium. This paper also reviews different types of amplifiers available, their limitations and those used in long haul WDM systems. The noise generated by the amplifiers limits the number of amplifiers used in WDM systems. The algorithms used for optimal placement of in-line amplifier has also been discussed. While designing the long haul WDM system, wavelength converters play a major role in reducing the blocking probability of optical network. The second part of this paper [1] reviews the effect of using wavelength converters, the benefits in term of decreased probability of blocking, the routing and wavelength assignment schemes and the various algorithms for their optimal placement.