In transparent Wavelength Division Multiplexing (WDM) networks, the signal is transported from source to destination
in the optical domain through all-optical channels, or lightpaths. A lightpath may traverse several fiber segments and
optical components that in general degrade the optical signal. This effect introduces the need for considering physical
layer impairments during the connection-provisioning phase. Physical layer impairments can be divided into linear and
non-linear. Both types of impairments are highly dependent on the fiber characteristics, which in turn are sensitive to
length, temperature and age. A close look at the fiber infrastructure of today's network operators reveals a situation
where old and newly deployed fibers coexist in the network. This heterogeneous fiber plant presents a challenge. A
tradeoff should be found between the QoS requirements of connection requests and the use of the available (old and
new) network resources. This calls for a provisioning mechanism able to adapt to the various fiber composition
scenarios.
In parallel, given the need for service differentiation, the authors recently proposed an Impairment Constraint Based
Routing (ICBR) algorithm, referred to as ICBR-Diff, supporting differentiation of services at the BER (Bit Error Rate)
level in a network with a homogeneous fiber infrastructure. In this paper the ICBR-Diff algorithm is extended to
heterogeneous network; particularly, it is evaluated in WDM networks with fiber links having varying Polarization Mode
Dispersion characteristics, i.e., with old and new fiber coexisting. Simulation results show that the ICBR-Diff algorithm
exhibits high adaptability in a heterogeneous fiber composition scenario. This translates into improved performance in
terms of blocking probability, when compared to traditional impairment aware routing algorithms.
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" to satisfy a specific connection request.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.