Grid Job Routing Algorithms - Phosphorus

Grid Job Routing Algorithms4 Infrastructure Considerations and UserRelated RequirementsIn this section the most critical physical layer characteristics that should be considered by the routing algorithmsto provide optimized performance and overcome certain infrastructure related restrictions are presented andthoroughly analyzed. In addition, a number of user related requirements that should also be taken into accountby the routing algorithms to offer adequate network QoS are introduced.4.1 Physical layer performance considerationsIn all-optical networks it is usually assumed that all routes have adequate signal quality. Generally, this isobtained through some link budgeting procedures that, finally, impose limits to the geographic size of the allopticaldomain by evaluating all the physical features of the network (amplifiers, fibers, wavelengths, etc.).However, the increasing bit rates of the line transmissions impose an increase in the injected power, whichconsequently implies a major impact on optical impairments.Physical layer impairments may be classified as linear and non-linear. Linear impairments are independent ofthe signal power and affect each of the optical channels individually, whereas nonlinear impairments affect notonly each optical channel separately but they also cause disturbance and interference between them. In thissection we give a description of the origin and the impact of the impairments considered in the simulations.4.1.1 Linear impairmentsAmplified Spontaneous Emission noiseThe advent of practical optical amplifiers capable of simultaneously amplifying multiple signal wavelengths thatoccupy an appreciable range of the optical spectrum was the key technological advance that ushered in theWDM revolution. Optical amplifiers are used at the end of each fiber span to boost the power of the WDMsignal channels to compensate for fiber attenuation in the span.Project:PHOSPHORUSDeliverable Number: D.5.3Date of Issue: 31/06/07EC Contract No.: 034115Document Code: Phosphorus-WP5-D5.329