Essay --

IMPAIRMENT AWARE ROUTING In WDM technology, the capacity of a fiber is divided into several subscribers by using light paths. In these paths traffic flows. Traffic between a pair of nodes may not fill up the available bandwidth of a light path. The network performance is affected by the transmission impairments which are due to the non ideal optical components. Since we have optical amplifier, optical switches and other optical devices and soon we have all optical equipments with the time and it is possibility that the entire network will be optical network. Transparent Optical Network Opaque Network There are two types of networks. These are opaque network and transparent network. In opaque network we have to do Optical-Electrical-Optical conversion at all nodes in the path. This type of network is costly because if we make a nationwide network then we will have to use a large no. of routers. But to make it less expensive we can use translucent network. In translucent network the regeneration is done only on a few nodes instead of all nodes. Transparent Network The other network that is transparent is less costly because there is no need of OEO conversion at the intermediate nodes. We can send analog signal in the transparent network. The size of transparent network is determined by impairments effects such as Chromatic dispersion (CD), attenuation, crosstalk, noise etc. Effects of Transmission Impairments on Routing and Wavelength Assignment When signal travels from source to destination then it may be ruined by linear and non-linear impairments. Linear impairments are amplifier noise, Group velocity dispersion (GVD), polarization mode dispersion (PMD), component crosstalk. The nonlinear impairments are self-phase modulation... ...s called Physical layer blocking. Advantages ïÆ'Ëœ Network load decreases by using IABP and IAFF ïÆ'Ëœ About 30 % reduction in blocking ïÆ'Ëœ Call admission criteria not only depends on the resource availability but also on quality of light path’s signal ïÆ'Ëœ A light path with good signal quality ïÆ'Ëœ Network resources are in intelligent control ïÆ'Ëœ Network used more efficiently Disadvantages ïÆ'Ëœ This technology cannot compute a route with minimal impairments ïÆ'Ëœ To find a qualified route path for the connection request it needs more than one trial ïÆ'Ëœ Algorithm does not consider residual-dispersion accumulation, power divergence, polarization-dependent loss gain (PDLIPDG), filter concatenation, signal transient, fiber nonlinearities. ïÆ'Ëœ When the data rate increases to 40 Gbps and furthermore, impairments become even more difficult ïÆ'Ëœ As load increases the call blocking increases