5 research outputs found
On the offline physical layer impairment aware RWA algorithms in transparent optical networks: state-of-the-art and beyond
In transparent optical networks with no regeneration, the problem of capacity allocation to traffic demands is called "Roting and Wavelength Assignment". Much work on this topic recently has focused on the dynamic case, whereby demands arrive and must be served in real-time. In addition, due to lack of regeneration, physical impairments accumulate as light propagates and QoT may become inappropiate (e.g., too high Bit Error Rate). Considering the physical layer impairments in the network planning phase gives rise to a class of RWA algorithms: offline Physical Layer Impairment Aware- (PLIA-)RWA. This paper makes a survey of such algorithms, proposes a taxonomy, and a comparison between these algorithms for common metrics. We also propose a novel offline PLIA-RWA algorithm, called POLIO-RWA, and show through simulations that it decreases blocking rate compared with other PLIA-RWA algorithms.Postprint (published version
Scalable Impairment-Aware Anycast Routing in Multi-Domain Optical Grid Networks
ABSTRACT In optical Grid networks, the main challenge is to account for not only network parameters, but also for resource availability. Anycast routing has previously been proposed as an effective solution to provide job scheduling services in optical Grids, offering a generic interface to access Grid resources and services. The main weakness of this approach is its limited scalability, especially in a multi-domain scenario. This paper proposes a novel anycast proxy architecture, which extends the anycast principle to a multi-domain scenario. The main purpose of the architecture is to perform aggregation of resource and network states, and as such improve computational scalability and reduce control plane traffic. Furthermore, the architecture has the desirable properties of allowing Grid domains to maintain their autonomy and hide internal configuration details from other domains. Finally, we propose an impairment-aware anycast routing algorithm that incorporates the main physical layer characteristics of large-scale optical networks into its path computation process. By integrating the proposed routing scheme into the introduced architecture we demonstrate significant network performance improvements. Keywords: Grid computing, routing algorithms, optical networks, physical impairments, anycast routing. INTRODUCTION Today, the need for network systems to support storage and computing services for science and business, is often satisfied by relatively isolated computing infrastructure (clusters). Migration to truly distributed and integrated applications requires optimization and (re)design of the underlying network technology to create a Grid platform for the cost and resource efficient delivery of network services with substantial data transfer, processing power and/or data storage requirements. Optical networks offer an undeniable potential for the Grid, given their proven track-record in the context of high-speed, long-haul, networking. Not only eScience applications dealing with large experimental data sets (e.g. particle physics) but also business/consumer oriented applications can benefit from optical Grid infrastructure [1]: both the high data rates typical of eScience applications and the low latency requirements of consumer/business applications (cf. interactivity) can effectively be addressed. When using transparent WDM as such network technology, signals are transported end-to-end optically without being converted to the electrical domain in between. Connection provisioning of all-optical connections (lightpaths) between source and destination nodes is based on specific routing and wavelength assignment algorithms (RWA). Traditional RWA schemes only account for network conditions such as connectivity and available capacity, without considering physical layer details. However, in transparent optical networks covering large geographical areas, the optical signal experiences the accumulation of physical impairments through transmission and switching, possibly resulting in unacceptable signal quality Another emerging and challenging task in distributed and heterogeneous computing environments, is job scheduling: when and where to execute a given Grid job, based on the requirements of the job (for instance a deadline and minimal computational power) and the current state of the network and resources. Traditionally, a local scheduler optimizes utilization and performance of a single Grid site, while a meta-scheduler is distributes workload across different sites. Current implementations of these (meta-)schedulers only account for Grid resource availability In this paper we propose a novel architecture to support impairment-aware anycast routing for large-scale optical Grid networks. Section 2 discusses general approaches to support multi-domain networks. We then proceed to introduce a novel architecture, which can provide anycast Grid services in a multi-domain scenario (Section 3). Simulation analysis is used to demonstrate the improved scalability without incurring significant performance loss. Furthermore, Section 4 shows how to incorporate physical layer impairments, to further improve the performance of optical Grid networks. Conclusions are presented in Section 5
Adaptive routing and wavelength assignment in all-optical networks
In WDM all-optical networks without wavelength conversion capabilities, signals must travel on the same wavelength over long distances. During transmission the signal quality gets degraded due to linear and non-linear physical layer impairments resulting in high BER. Many PLI aware RWA algorithms have been proposed in the literature, which consider the effect of the impairments on the signal quality. We consider the effect of component crosstalk and ASE noise. The adaptive RWA algorithm presented incorporates QoS information at both the routing and wavelength assignment steps to mitigate the effect of crosstalk. Different routing strategies are used in the algorithm to compare the computational complexity and the blocking performance of the network
Design and optimization of optical routing techniques and devices
Doutoramento em Engenharia ElectrotécnicaEste trabalho apresenta três estudos principais acerca do desenvolvimento e
aplicação de sistemas de monitorização óptica avançados com base na
análise de histogramas assíncronos, conversão de comprimento de onda de
sinais de débito elevado e o impacto das não-linearidades das fibra ópticas em
sistemas utilizando técnicas avançadas de transmissão. Mostra-se que a
comparação de histogramas assíncronos com histogramas de referência pode
ser usada para extrair informação a respeito da qualidade e do ruído que
afecta o sinal em análise. O método proposto é validado através de simulação
numérica e experiência.
Um modelo analítico para a computação das limitações em frequência da
modulação cruzada de fase (XPM) em conversores de comprimento de onda
de fibra é proposto e validado através de simulação numérica até frequências
de modulação acima de 1 THz. O modelo proposto permite a derivação de
regras de engenharia para o dimensionamento de conversores de
comprimento de onda compostos por espelhos de fibra não linear. O
dimensionamento de um novo filtro para a optimização da conversão da XPM
em modulação de intensidado é proposto e validado por simulação numérica.
O impacto das não-linearidades na transmissão em fibra óptica de sinais de
banda lateral única a 10 Gb/s com compensação de dispersão concentrada é
avaliado através de simulação numérica. Mostra-se que as não-linearidades
intra-canal levam a severa degradação do desempenho. A degradação de
sinais de chaveamento por desvio diferencial de fase (DPSK) a 40 Gb/s devida
a XPM com sinais de chaveamento por desvio de amplitude herdados de
sistemas anteriores é também analisada. Uma análise bomba-sonda mostra
que a degradação do sinal resulta da modulação de intensidade induzida por
XPM. Este resultado permite a derivação de um modelo para estimar a
probabilidade de erro dos sinais DPSK degradados por XPM. Finalmente, é
apresentada uma abordagem analítica baseada em pequenas perturbações
para o estudo de não linearidades intra-canal em fibra óptica em sinais com
razão de extinção finita. Este estudo permite a identificação de duas novas
formas de degradação tomando a forma de impulsos entre diferentes símbolos
e fluctuações temporais e de amplitude.This work presents three main studies regarding the development and
application of advanced optical monitoring systems based on the analysis of
asynchronous amplitude histograms, the wavelength conversion of ultra-high
bit-rate signals, and the impact of fiber nonlinearities in systems employing
advanced transmission techniques. It is shown that asynchronous amplitude
histograms may be numerically compared with reference histograms to extract
information regarding quality and the noise degrading the signal under analysis.
The proposed method is validated through numerical simulation and
experiment.
An analytical model to compute the frequency limitations of cross-phase
modulation (XPM) in all-optical fiber wavelength converters is proposed and
validated using numerical simulation at modulation frequencies exceeding 1
THz. The proposed model allows deriving engineering rules for the
dimensioning of wavelength converters using nonlinear optical loop mirrors. A
novel filter design to optimize the conversion of XPM-induced phase
modulation in intensity modulation is proposed and validated using numerical
simulation.
Numerical simulation is used to evaluate the impact of fiber nonlinearities in the
transmission of 10 Gb/s single sideband signals in links using concentrated
electrical or optical dispersion compensation. It is shown that, intra-channel
fiber nonlinearities severely degrade the performance. The degradation of 40
Gb/s differential phase-shift-keying (DPSK) signals due to XPM with legacy
amplitude-shift keying signals is also analyzed. Pump-probe analysis show that
the signal degradation results from XPM-induced intensity modulation. This
allows deriving and validating a novel analytical model to estimate the bit-error
probability of the XPM-degraded DPSK signals. Finally, an analytical smallperturbations
approach to the study of intra-channel fiber nonlinearities in
signals with finite extinction ratio is presented. It allows the identification of two
new forms of degradation taking the form of impulses between symbols and
amplitude and temporal jitter