Shariati, M.; Diamantopoulos, N.-P.; Klonidis, D.; Comellas, J.; Tomkos, I. International Conference on Transparent Optical Networks p. 1-4 DOI: 10.1109/ICTON.2017.8024961 Data de presentació: 2017-07-04 Presentació treball a congrés
Space division multiplexing (SDM) has been proposed to cost-effectively increase the capacity of optical transmission systems. The cost savings can be realized by introducing some levels of spatial integration of elements. However, spatial densification increases the crosstalk (XT) interactions among spatial channels. The XT is expected to be mitigated by MIMO processing, however, it increases the power consumption which in turn can make MIMO based SDM solutions impractical. This is a major issue for datacenters exploiting SDM solutions. Therefore, removing/lightening the burden imposed by MIMO processing can make SDM a more favorable solution. In this paper, we propose a datacenter interconnection network (DCIN), utilizing PAM-M transceivers, which can circumvent MIMO processing. It can be achieved by designing proper fibers (e.g. elliptical core FMF) in which the likelihood of mixing between mode-groups can be reduced. A key contribution of this work is the development of an analytical model to estimate the maximum reach that PAM-M (M = 4,8) signals can travel through coupled SDM fibers, targeting intra- and inter-DCs applications. We then demonstrate that FMF with MIMO-less PAM-M transceivers can significantly reduce the cabling complexity, and consequently, the cost of DCINs compared to single wavelength multi-mode or single-mode fibers based deployments.
Shariati, M.; Rivas-Moscoso, J.; Marom, D.; Ben, S.; Klonidis, D.; Velasco, L.; Tomkos, I. Journal of lightwave technology Vol. 35, num. 13, p. 2559-2568 DOI: 10.1109/JLT.2017.2692301 Data de publicació: 2017-07-01 Article en revista
Spatially integrated switching architectures have been recently investigated in an attempt to provide switching capability for networks based on spatial division multiplexing (SDM) fibers, as well as to reduce the implementation cost. These architectures rely on the following switching paradigms, furnishing different degrees of spectral and spatial switching granularity: independent switching, which offers full spatial-spectral flexibility; joint-switching, which treats all spatial modes as a single entity; and fractional-joint switching, whereby subgroups of spatial modes are switched together as independent units. The last two paradigms are categorized as spatial group switching solutions since the spatial resources (modes, cores, or single-mode fibers) are switched in groups. In this paper, we compare the performance (in terms of spectral utilization, data occupancy, and network switching infrastructure cost) of the SDM switching paradigms listed above for varying spatial and spectral switching granularities in a network planning scenario. The spatial granularity is related to the grouping of the spatial resources, whereas the spectral granularity depends on the channel baud rate and the spectral resolution supported by wavelength selective switches (WSS). We consider two WSS technologies for handling of the SDM switching paradigms: 1) the current WSS realization, 2) WSS technology with a factor-two resolution improvement. Bundles of single-mode fibers are assumed across all links as a near-term SDM solution. Results show that the performance of all switching paradigms converge as the size of the traffic demands increases, but finer spatial and spectral granularity can lead to significant performance improvement for small traffic demands. Additionally, we demonstrate that spectral switching granularity must be adaptable with respect to the size of the traffic in order to have a globally optimum spectrum utilization in an SDM network. Finally, we calculate the number of required WSSs and their port count for each of the switching architectures under evaluation, and estimate the switching-related cost of an SDM network, assuming the current WSS realization as well as the improved resolution WSS technology.
Sayyad, P.; Rivas-Moscoso, J.; Klonidis, D.; Tomkos, I.; Shariati, M.; Comellas, J. IEEE International Conference on Communications p. 5192-5197 DOI: 10.1109/ICC.2015.7249148 Data de presentació: 2015-06-11 Presentació treball a congrés
Elastic optical network (EON) technology arises as a promising solution for future high-speed optical transport networks, inasmuch as it can provide superior flexibility and scalability in the spectrum allocation for seamlessly supporting a disparity of services, while coping with the rapid growth of Internet traffic. Spectrally efficient lightpath establishment in EONs is enabled by recent developments in flex-grid transceivers and wavelength selective switches (WSS), which are the key players in determining the amount of spectrum that needs to be reserved for a connection as well as the guard band (GB) required between adjacent channels, since the imperfect shape of the filters degrades the spectrum utilization efficiency of the network. In this paper, we focus on the impact of the filter sharpness on the performance of EONs from the networking perspective. In this regard, we initially quantify the effect of the sharpness of a transmitter Nyquist shaping filter and an LCoSbased WSS filter on the amount of spectrum required for efficient connection establishment. Subsequently, we investigate the practicality of moving to finer frequency slot sizes and, based on extensive simulation results, evaluate the improvement in terms of network blocking probability that can be obtained by using sharper filters.
A heterodyne envelope (HE) receiver (RX) is investigated in the context of orthogonal frequency division multiplexing (OFDM) passive optical networks (PONs). Impacts of limited roll-off factor of shaping filter and required guard-band (GB) are studied through numerical simulations, showing that the Carrier to Signal Power Ratio (CSPR) value plays a significant role in the systems performance. For a QPSK system with 10 Gbps bitrate and for a bit error ratio (BER) quality threshold of 10-3 we show an improvement of 10.8 dB in sensitivity and 25% in spectral efficiency by using an optimum CSPR value as compared to unity CSPR.