This paper quantifies the benefit of next-generation 800 Gb/s coherent pluggable interfaces for examples of German, Indian and North American core WDM networks thanks to PCS modulation and better performance than the OpenROADM specifications.

As deploying large amounts of monitoring equipment results in elevated cost and power consumption, novel low-cost monitoring methods are being continuously investigated. A new technique called Power Profile Monitoring (PPM) has recently gained traction thanks to its ability to monitor an entire lightpath using a single post-processing unit at the lightpath receiver. PPM does not require to deploy an individual monitor for each span, as in the traditional monitoring technique using Optical Time-Domain Reflectometer (OTDR). In this work, we aim to quantify the cost and power consumption of PPM (using OTDR as a baseline reference), as this analysis can provide guidelines for the implementation and deployment of PPM. First, we discuss how PPM and OTDR monitors are deployed, and we formally state a new Optimized Monitoring Placement (OMP) problem for PPM. Solving the OMP problem allows to identify the minimum number of PPM monitors that guarantees that all links in the networks are monitored by at least n PPM monitors (note that using n>1 allows for increased monitoring accuracy). We prove the NP-hardness of the OMP problem and formulate it using an Integer Linear Programming (ILP) model. Finally, we also devise a heuristic algorithm for the OMP problem to scale to larger topologies. Our numerical results, obtained on realistic topologies, suggest that the cost (and power) of one PPM module should be lower than 2.6 times that of one OTDR for nation-wide and 10.2 times for continental-wide topology.

Operators are constantly faced with the need to increase optical-network capacity to accommodate rapid traffic growth while minimizing the cost-per-bit and power-per-bit. The drastic reduction of the power consumption of IP routers and ZR/ZR+ pluggable transponders seen in the past several years has renewed the interest in “opaque” optical-network architectures, where no optical bypassing is allowed. In this work, we aim to quantify and compare the power consumption of four “IP over wavelength division multiplexing” (IPoWDM) transport network architectures employing ZR/ZR+ modules versus long-haul muxponders, considering different grooming, regeneration, and optical bypassing capabilities. We first propose a power consumption model for different IPoWDM node architectures with ZR/ZR+ modules and long-haul muxponders. Then, to obtain the power consumption of different architectures, we propose a compact auxiliary-graph-based network-design algorithm extensible to different network architectures. Moreover, we investigate how the continuous decrease in the power consumption of ZR/ZR+ and IP routers can impact the power consumption of different architectures through a sensitivity analysis. Illustrative numerical results on networks of different sizes show that, despite drastic reductions of power consumption at the IP layer, optical bypassing is still the most power-efficient solution, reducing consumption by up to 48%.

We quantify and compare the power consumption of four IPoWDM transport network architectures employing ZR/ZR+ modules, considering different grooming, regeneration, and optical bypass capabilities. Results show that optical bypass is still the most power-efficient solution, reducing consumption by up to 30%.

We examine how the ultimate performance of WDM networks is affected when the wavelength assignment strategy aims at minimizing their number of colorless/directionless add/drop blocks, and so why contentionless optical node layout is preferable.

We demonstrate a novel agent for optical disaggregated optical networks. When the Monitoring and Data Analytics detects a degradation, it recommends the SDN controller to trigger a network reconfiguration computed by a novel planning tool.

Network operators have cope with the never stopping traffic growth and also with the new service dynamicity, due to the increase of data-center and 5G traffic, video service and caching. With multimedia traffic more and more dominant with respect to voice, network operators have reduced their revenues and need to reduce the overall network costs associated to the management. To deal with traffic and operator requirements, new control and management paradigms became necessary and are based mainly on software-defined networking (SDN) architecture, which improve network flexibility and manageability. In this paper we presented SMART-A, an SDN-application prototype able to reconfigure the optical network in case of defragmentation, due to the sub-optimal spectrum resource occupation, and re-routing, due to optical connection failure caused by physical degradation of the optical medium.

Traffic requests are becoming more heterogeneous and dynamic causing the so-called spectrum fragmentation. We propose a reactive defragmentation algorithm to mitigate this issue which degrades the network performance. Three strategies are suggested to compact the spectrum comb, taking into account the minimization of the disrupted services and their reconfiguration times. An accurate Rerouting strategy allows the set-up of a higher amount of traffic, obtaining more capacitive networks.

We present a new strategy of regenerator placement along with traffic growth in the elastic WDM networks, by introducing additional regenerators on the already allocated connections only from when needed to accommodate extra demand of capacity.

Disaggregated optical technologies have the potential to provide cost-effective and vendor-neutral optical node solutions especially suitable for metro networks. Differently from the conventional proprietary networks, specific design, modelling, control and management operations have to be carefully defined and standardized. This paper first presents the most relevant disaggregated optical devices such as transponders, reconfigurable optical add-drop multiplexers (ROADMs), and amplifiers, and it discusses the corresponding vendor-neutral YANG models and NETCONF control. Then, the implementation of the related software agents is presented, along with a Software Defined Networking (SDN) controller based on the ONOS open-source framework. The implementations are validated in a disaggregated optical network testbed, showing successful interoperability and experimentally demonstrating transmission with optical power configurations.

This study illustrates the benefit of “opportune” regeneration while WDM networks are becoming more elastic in terms of spectral efficiency versus transmission reach of optical carriers.

For two WDM core elastic networks, we study whether mixing 50-GHz and 75-GHz carrier spaces brings enough extra network capacity to offset the related complexity of wavelength allocation.

We investigate the progressive regenerator deployment throughout traffic growth in two WDM core networks, by illustrating how this strategy is more profitable with 64 GBaud Elastic Optical Transponders (EOT) than with 32 GBaud EOTs.

This paper illustrates the relevance of specific allocation of flexible opto-electronic regeneration for ultimate spectral efficiency in the core elastic WDM networks: up to 2.5 times more traffic can be transported with sophisticated regeneration strategies versus basic 100Gb/s routing.

The cost of translucent optical networks is mainly associated to the deployed optoelectronic devices, some of them used for traffic insertion, others (3R devices) for coping with optical layer transmission constraints (regeneration and wavelength conversion). When designing a network with a required traffic resiliency, operators want to reduce the overall number (hence the cost) associated to optoelectronic devices at the optical layer without incurring in traffic blocking. In generalized multiprotocol label switching (GMPLS)-based optical networks the computation and set-up of alternative paths after fiber failures (restoration) ensure traffic survivability. In such networks 3Rs can be either associated to a specific nominal path (nominal-3Rs) or shared among several restoration paths (restoration-3Rs). An effective computation of restoration paths allows to maximize restoration-3Rs sharing, hence to minimize the network cost. In this work, we focused on the path computation of restoration paths to improve restoration3Rs sharing. To this aim, we propose an adaptive alternative routing algorithm which is aware of the already deployed restoration-3Rs and favors the computation of alternative restoration paths able to reuse already installed 3Rs. The advantages of the proposed method are estimated by comparing the number of restoration-3Rs with respect to another method available in the literature.

We compare the cost efficiency of optical networks based on elastic transponders when accounting for link margins due to network ageing and on fixed 100 Gb/s PDM-QPSK interfaces technologies. Germany50 and Italian photonic backbone networks are used for providing results during a 10-year period given different throughputs, traffic growth rates and the cost erosions of elastic optical transponders. We also investigate the distribution of the ageing margins and modulation schemes that might be changed during the life of the network, before its end-of-life (EoL).

This chapter reviews the basics of Dense Wavelength Division Multiplexing (DWDM) and shows how this will be superseded by a more flexible use of the optical fibre spectrum, together with more flexible transponders offering multiple bit rates from the same device. The chapter explains the benefits of this new approach and examines the optical filter technology that enables it. Finally, the chapter looks at how networks will migrate towards this new network operating paradigm.

We propose and analyze a new load-aware reach maximization procedure based on the Gaussian Noise model for dispersion-uncompensated optical networks with coherent detection. We estimate the opto-electronic regeneration savings with respect to the standard full-load reach approach, and find examples where significant savings can be achieved. The load aware reach and its corresponding optimal power can be computed in real time by the routing and wavelength assignment unit to make statistical decisions about setting-up new lightpaths or regenerating existing ones.

We present a method that easily dimension an elastic multi-layer networks based on an extension of a single-datarate multi-layer model. The computation time and optoelectronic resources are compared for single- and multi-layer scenarios.