Lightpath routing considering differentiated physical layer constraints in transparent WDM networks

Wavelength division multiplexing (WDM) technology is considered to be the ultimate answer to the rapidly growing capacity demand of next generation networks. Many routing and wavelength assignment (RWA) algorithms, proposed for lightpath provisioning, base their routing decisions on the availability of network resources, and assume that optical fibers and components are ideal. In reality, physical impairments degrade the quality of the optical signal propagating through fiber segments and optical components. To cope with this problem, Impairment Constraint Based Routing (ICBR) algorithms, that consider physical impairments during connection provisioning, are currently proposed to prevent selecting lightpaths with poor signal quality. However, these algorithms support only a single (highest) quality of transmission threshold, the same one for all connection requests. This does not fit well with the variety of services, with potentially disparate QoS requirements, that the next generation networks are expected to support. Consequently, the efficiency of network resource utilization is reduced. This paper demonstrates that a significant improvement, in terms of blocking probability, can be achieved when using an ICBR algorithm with differentiated physical layer constraints. Performance is compared with conventional impairment aware routing approaches when unprotected, shared path protected (SPP), and dedicated path protected (DPP) connection requests are considered. The achieved improvement is a result of more efficient resource utilization as unnecessary connection blocking can be avoided by selecting network resources offering optical signal quality that is “good enough”good enough to satisfy a specific connection request. to satisfy a specific connection request.