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We present a constraint-based routing (CBR) approach for real-time operation considering both linear as well as nonlinear signal quality degrading effects in a heterogeneous network infrastructure. Different novel routing algorithms are assessed regarding their blocking probabilities. Furthermore, regenerator pools are placed at a limited number of nodes selected by a heuristic algorithm taking into account the physical impairments. It is shown that CBR together with intelligent regenerator placement can decrease the blocking probability significantly.

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A novel constraint-based routing (CBR) algorithm taking into account the dominant linear and nonlinear fiber optical transmission impairments has been analyzed. It is shown that CBR and intelligent regenerator placement decrease the blocking probability significantly. IntroductionIn future transparent optical transmission systems automatic wavelength switching will be introduced (automatically switched optical network, ASON). The rapidly increasing traffic demands require solutions, which reduce the operational expenditure by efficient routing. In the past, opaque (employing optoelectronic conversions at each node), fully-transparent or translucent (with selective regeneration) networks have been investigated. Because of the high cost of optoelectronic conversions and limited reach in fully-transparent networks the translucent topology seems to be the most promising candidate for future wavelength agile longhaul networks.Physical degradation effects such as noise, linear impairments and nonlinear fiber effects affect the signal quality along the transmission path. Depending on the channel load and transmission distance some paths cannot be set up fully transparently because the transmission quality requirements (i.e. pre-FEC bit error ratio (BER) = 10 -9 or Q-factor = 15.56 dB) cannot be fulfilled. In the last couple of years the inclusion of physical layer effects in the network operation and routing has been a topic of intensive research (e.g., [1],[2]). In this paper we propose a combined approach of regenerator placement based on the estimated signal degradation along the links and nodes and constraint-based routing (CBR) to set up paths according to the demands. We show -for the first time to our knowledge -that the combined approach of regenerator placement and routing, both based on physical degradation effects, may significantly decrease the blocking probability in a realistic network scenario with a varying dispersion map and different span lengths. Investigated networkFor the investigations the COST266 reference network (large topology) has been chosen [3]. This network has pan-European dimensions (37 nodes and 57 links) in a mesh topology (Fig. 1, left). System simulations have shown that for very long paths in the COST266 network the nonlinear fiber effects of cross-phase modulation (XPM) and four-wave mixing (FWM) cannot be neglected when 10 Gb/s NRZ-OOK modulation is employed (Fig. 2). This is why we included the analytical models presented in [4] in our CBR approach to assess XPM and FWM. From Fig. 2 an average transparent reach of approximately 1820 km for SSMF can be observed. However, there are short paths with poor signal quality (min. 1280 km) and long paths with good quality (max. 2220 km) making an accurate assessment of the actual signal quality desirable. In the COST266 reference network only link lengths and demands have been defined. For the assessment of the signal quality, however, it is essential to know the physical parameters of the links. For this purpose a heuristic ap...

An experimental demonstration of direct-detection single-sideband Nyquist-pulse-shaped 16-QAM subcarrier modulated (Nyquist-SCM) transmission implementing a receiver-based signal-signal beat interference (SSBI) cancellation technique is described. The performance improvement with SSBI mitigation, which compensates for the nonlinear distortion caused by square-law detection, was quantified by simulations and experiments for a 7 × 25 Gb/s WDM Nyquist-SCM signal with a net optical information spectral density (ISD) of 2.0 (b/s)/Hz. A reduction of 3.6 dB in the back-to-back required OSNR at the HD-FEC threshold was achieved. The resulting reductions in BER in single channel and WDM transmission over distances of up to 800 km of uncompensated standard single-mode fiber (SSMF) achieved are presented.

Nonlinear distortion has always been a challenge for optical communication due to the nonlinear transfer characteristics of the fiber itself. The next frontier for optical communication is a second type of nonlinearities, which results from optical and electrical components. They become the dominant nonlinearity for shorter reaches. The highest data rates cannot be achieved without effective compensation. A classical countermeasure is receiver-side equalization of nonlinear impairments and memory effects using Volterra series. However, such Volterra equalizers are architecturally complex and their parametrization can be numerical unstable. This contribution proposes an alternative nonlinear equalizer architecture based on machine learning. Its performance is evaluated experimentally on coherent 88 Gbaud dual polarization 16QAM 600 Gb/s back-to-back measurements. The proposed equalizers outperform Volterra and memory polynomial Volterra equalizers up to 6th orders at a target bit-error rate (BER) of 10 − 2 by 0.5 dB and 0.8 dB in optical signal-to-noise ratio (OSNR), respectively.

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Future 5G networks will bring important challenges to network operators such as the traffic load increase mainly due to the proliferation of mobile broadband communications. This will force Mobile Network Operators (MNOs) redesigning and investing on their infrastructures (e.g., new equipment for Radio Access Network-RAN-, backhaul, etc.) to cope with such data growth. Aiming at lowering both CapEx and OpEx, current networking trends on network virtualization, Software Defined Networking (SDN) and Network Function Virtualization (NFV) provide an appealing scenario to flexibly deal with MNO's increase of traffic without over-dimensioning the deployed network resources. To this end, we rely on an implemented SDN/NFV orchestrator which automatically serves MNO capacity requests by computing and allocating virtual backhaul tenants. Such backhaul tenants are built over a common physical aggregation network, formed by heterogeneous technologies (e.g., packet and optical) that may be owned by different infrastructure providers. MNO's RAN traffic is transported towards mobile core network (i.e. Evolve Packet Core, EPC) where required backhaul resources are tailored to the capacity needs. The EPC functions are virtualized within the cloud (i.e., vEPC) leveraging the NFV advantages. This increases MNO flexibility where cloud resources are instantiated according to EPC needs. The goal of the SDN/NFV orchestrator is to jointly allocate both network and cloud resources deploying virtual backhaul tenants and vEPC instances for a number of MNOs with different service and capacity requirements. Each MNO's backhaul is isolated and controlled independently via a virtualized SDN controller (vSDN) deployed in the cloud. The SDN/NFV orchestrator architecture is detailed and experimentally validated in a setup provided by CTTC and ADVA. Specifically, upon an MNO request the orchestrator instantiates the vEPC and vSDN functions in the cloud and then composes the MNO's backhaul tenant over a multi-layer (packet and optical) aggregation network.