The role of the RM-ODP computational viewpoint concepts in the MDA approach

An MDA design approach should be able to accommodate designs at different levels of platform-independence. We have proposed a design approach previously (in [2]), which allows these levels to be identified. An important feature of this approach is the notion of abstract platform. An abstract platform is determined by the platform characteristics that are relevant for applications at a certain level of platform-independence, and must be established by considering various design goals. In this paper, we define a framework that makes it possible to use RM-ODP concepts in our MDA design approach. This framework allows a recursive application of the computational viewpoint at different levels of platform-independence. This is obtained by equating the RM-ODP notion of infrastructure to our notion of abstract platform

Estimating the Performance of Direct-Detection DPSK in Optical Networking Environments Using Eigenfunction Expansion Techniques

WOS:000281971100002 (Nº de Acesso Web of Science)“Prémio Científico ISCTE-IUL 2011”In-band crosstalk, due to multiple interferers, has been identified as one of the most severe impairments in optical transparent networks, especially in the ones with a large number of nodes and a high wavelength density. Due to its robustness to in-band crosstalk differential phase-shift keying (DPSK) emerges as an attractive modulation scheme to be used in such environments. This paper proposes a rigorous formulation to estimate the performance of direct-detection DPSK receivers using an eigenfunction expansion technique in the time domain. The method takes into account both the in-band crosstalk, due to an arbitrary number of interfering terms, and the amplified spontaneous emission noise and is able to deal with any combination of optical and electrical filter shapes. Using this method the accuracy of an approximation based on the wideband optical filtering assumption was evaluated and shown that the approximation, although not providing reliable results for the error probabilities, can be used with confidence to compute power penalties due to in-band crosstalk. Furthermore, the crosstalk tolerance of DPSK over on-off keying was quantified and shown that this tolerance is reduced when the number of interferers increases

Applying the skew-normal distribution to model coherent MPI and to evaluate its impact on PAM signals

We statistically model the coherent multipath interference (MPI) using an extended skewnormal distribution, with the results showing a good agreement with published experimental data. This distribution is very flexible and permits to model data with large skewness values, which is a typical feature in coherent MPI histograms. Furthermore, the developed model was applied to estimate the impact of coherent MPI on PAM-4 systems, with the results showing a 1-dB Q-penalty for an MPI level of -24 dB and a bit error ratio of 10^-3.info:eu-repo/semantics/acceptedVersio

CPO - Carteira de projetos online.

bitstream/CNPT-2010/40597/1/p-co232.pd

A framework for analyzing in-band crosstalk accumulation in ROADM-based optical networks

Reconfigurable optical add-drop multiplexers (ROADMs) are central pieces in building transparent optical transport networks. However, due to physical limitations, these devices can be a source of in-band crosstalk, which affects the quality of the lightpaths routed and the network performance. Hence, to efficiently design optical networks it is important to study how this impairment is generated and to understand its dependency on relevant network parameters, such as the number of wavelengths used and the node degree. In this paper, we propose a framework to analyze the in-band crosstalk accumulation inside of ROADM-based networks. The framework computes the number of accumulated crosstalk terms in each link of a lightpath considering different physical topologies, as well as different routing and wavelength assignment strategies. An empirical formula is also derived for computing the maximum number of accumulated crosstalk terms as a function of the network parameters. We observe that in the majority of the studied cases, there is a complete agreement between the results of the proposed framework and the empirical formula.info:eu-repo/semantics/acceptedVersio

Implications of in-band crosstalk on DQPSK Signals in ROADM-based metropolitan optical networks

Metropolitan optical networks can be designed to transport a multitude of signals with different bit rates and modulations formats. In this way, in-band crosstalk signals, originated from imperfect isolation inside ROADM (Reconfigurable Optical Add and Drop Multiplexer)-based optical nodes, will potentially have a different modulation format than the primary signal. In this paper, the origin of in-band crosstalk in a typical ROADM is analysed and its impact on differential quadrature phase-shift keying (DQPSK) signals is assessed through an analytical formalism based on the moment generating function (MGF) of the receiver decision variable. Various scenarios are analysed including the case of multiple interfering terms with different modulation formats, namely the on-off keying (OOK). It is concluded that the OOK interferer is more detrimental than the DQPSK interferer for DQPSK systems, or than the differential phase-shift keying (DPSK) interferer for DPSK systems.info:eu-repo/semantics/publishedVersio

Theoretical Insights into the Impact of Coherent and Incoherent Crosstalk on Optical DPSK Signals

WOS:000283247600001 (Nº de Acesso Web of Science)“Prémio Científico ISCTE-IUL 2011”This paper provides new theoretical insights into the properties of direct detection differential phase-shift keying (DPSK) signals impaired by coherent and incoherent crosstalk. Coherent crosstalk is due to multiple replicas originated while a data signal is routed through an optical network, whereas the source of incoherent crosstalk resides on the interference from other DPSK signals. A special emphasize has been put on modeling the multipath coherent crosstalk, with analytical expressions being derived and presented for both the moment generating function of the decision variable and the average error probability. A rigorous analysis, capable of dealing with arbitrary filtering, is also presented, which is used afterwards to assess the accuracy of the analytical formulas. A detailed comparison with incoherent crosstalk is also performed. Using also an exact treatment for this type of crosstalk it is shown that for low OSNR penalties the coherent crosstalk leads, in some circumstances, to slightly worse results than the incoherent one, but this situation is reversed when the total crosstalk level and the number of interferers increase

Quantifying the influence of crosstalk-crosstalk beat noise in optical DPSK systems

In-band crosstalk, due to multiple interferers, is one of the most severe physical impairments in optical transparent networks. Differential phase-shift keying (DPSK) has been identified as an attractive modulation scheme to be used in such environments due to its robustness to in-band crosstalk. At the output of the receiver photodiode, which is assumed to behave as a square law device, the in-band crosstalk interferes with the signal, resulting in the signal-crosstalk beat noise and the crosstalk-crosstalk beat noise. Usually this last noise contribution is neglected, but in this paper the impact of the crosstalk-crosstalk beating terms is considered and quantified. It is concluded that these terms have a growing influence as the optical signal-to-noise ratio (OSNR) value increases.info:eu-repo/semantics/acceptedVersio