Maximally spatial-disjoint lightpaths in optical networks

Lightpaths enable end-to-end all-optical transmission between network nodes. For survivable routing, traffic is often carried on a primary lightpath, and rerouted to another disjointed backup lightpath in case of the failure of the primary lightpath. Though both lightpaths can be physically disjointed, they can still fail simultaneously if a disaster affects them simultaneously on the physical plane. Hence, we propose a routing algorithm for provisioning a pair of link-disjoint lightpaths between two network nodes such that the minimum spatial distance between them (while disregarding safe regions) is maximized. Through means of simulation, we show that our algorithm can provide higher survivability against spatial-based simultaneous link failures (due to the maximized spatial distance)

Optimization of system’s parameters for wavelength conversion of E-band signals

Current and future wireless communication systems are designed to achieve the user’s demands such as high data rate and high speed with low latency and simultaneously to save bandwidth and spectrum. In 5G and 6G networks, a high speed of transmitting and switching is required for internet of things (IoT) applications with higher capacity. To achieve these requirements a semiconductor optical amplifier (SOA) is considered as a wavelength converter to transmit a signal with an orthogonal frequency division multiplexing with subcarrier power modulation (OFDM-SPM). It exploits the subcarrier’s power in conventional OFDM block in order to send additional bits beside the normally transmitted bits. In this paper, we optimized the SOA’s parameters to have efficient wavelength conversion process. These parameters are included the injection current (IC) of SOA, power of pump and probe signals. A 7 Gbps OFDM-SPM signal with a millimeter waves (MMW) carrier of 80 GHz is considered for signal switching. The simulation results investigated and analyzed the performance of the designed system in terms of error vector magnitude (EVM), bit error rate (BER) and optical signal-to-noise ratio (OSNR). The optimum value of IC is 0.6 A while probe power is 9.45 and 8.9 dBm for pump power. The simulation is executed by virtual photonic integrated (VPI) software

Robustness metrics for optical networks

Telecommunication networks are vulnerable towards single or simultaneous nodes/links failures, which may lead to the disruption of network areas. The failures may cause performance degradation, reduced quality of services, reduced nodes/links survivability, stability, and reliability. Therefore, it is important to measure and enhance the network robustness, via the use of robustness metrics. This paper gives an overview of several robustness metrics that are commonly used for optical networks, from the structural, centrality and functional perspectives

Numerical analysis of UFMC and FBMC in wavelength conversion for radio over fiber systems using semiconductor optical amplifier

The 5G networks promise to use advanced access techniques and modulation formats to achieve new requirements of the huge number of users such as higher data, high speed, and low latency. Millimeter-wave (MMW) signal and new modulation schemes such as universal filtered multicarrier (UFMC) and filtered bank multicarrier (FBMC) are playing a fundamental role to accomplish these requirements. UFMC and FBMC are classified under multicarrier modulation formats which are considered as a suitable modulation scheme in 5G and replacing a well-known modulation format of filtered orthogonal frequency division multiplexing (OFDM) which was used in 4G. This interest in using UFMC and FBMC in 5G wireless systems is the reduction of out-of-band (OOB) spectrum in UFMC and reduction of sidelobe suppression in FBMC. The contribution of this paper is to propose a model of wavelength conversion using a semiconductor optical amplifier (SOA) for both schemes UFMC and FBMC- off-set quadrature amplitude (OQAM). In addition, we analyze and compare their performance in terms of bit error rate (BER) and error vector magnitude (EVM) for a wavelength conversion application. Finally, we investigate the main disadvantage of OFDM which is the high Peak to Average Power Ratio (PAPR) for both schemes, and compare between them. Photonic switching of a 4 Gbps 16-QAM UFMC and FBMC-OQAM signal centered at 50 GHz is performed. The optical single-sideband (OSSB) signal is generated with 18.85 dB of sideband suppression ratio (SSR). The results show that the best values of BER and EVM can be obtained when the injection current (IC) is 0.7–0.9A. For converted signal using FBMC-OQAM, it has power penalty ~ 2.5 dB at BER threshold 1 × 10-3and has also ~ 2 dB power penalty compared to the UFMC scheme at EVM threshold 5.6%. In addition, the wavelength switching system with FBMC and UFMC modulation schemes achieves the same PAPR

Optimization of system’s parameters for wavelength conversion of E-band signals

Current and future wireless communication systems are designed to achieve the user’s demands such as high data rate and high speed with low latency and simultaneously to save bandwidth and spectrum. In 5G and 6G networks, a high speed of transmitting and switching is required for internet of things (IoT) applications with higher capacity. To achieve these requirements a semiconductor optical amplifier (SOA) is considered as a wavelength converter to transmit a signal with an orthogonal frequency division multiplexing with subcarrier power modulation (OFDM-SPM). It exploits the subcarrier’s power in conventional OFDM block in order to send additional bits beside the normally transmitted bits. In this paper, we optimized the SOA’s parameters to have efficient wavelength conversion process. These parameters are included the injection current (IC) of SOA, power of pump and probe signals. A 7 Gbps OFDM-SPM signal with a millimeter waves (MMW) carrier of 80 GHz is considered for signal switching. The simulation results investigated and analyzed the performance of the designed system in terms of error vector magnitude (EVM), bit error rate (BER) and optical signal-to-noise ratio (OSNR). The optimum value of IC is 0.6 A while probe power is 9.45 and 8.9 dBm for pump power. The simulation is executed by virtual photonic integrated (VPI) software

Capacity-bounded lightpath routing in WDM optical networks

To meet the increasing user bandwidth demands, the ICT networks are constantly expanding. The optical fiber technology has completely revolutionized the bandwidth capacity of both the core networks and the access networks. In core networks, the optical links provide very high bandwidth connectivity over long distance. Thus, any link failure due to disastrous events like earthquake, flood, landslide etc. can lead to massive service outages and huge fiscal losses. Normally, optical fibers are laid in 1 + 1 configuration to route the traffic to the alternate path in such scenario. However, a natural disaster event may lead to simultaneous failure of multiple lightpaths. Therefore, routing algorithm, running on network nodes (routers or switches), are required in such case to establish new routes. Nevertheless, generally the routing schemes follow the least hop count and shortest distance approach to route the traffic to another backup path. Nonetheless, this approach may result in congestion on some links while other links may have unutilized capacity. This also makes it progressively tougher to fit more connection requests from the access network. Hence, implementation of more advanced path computation capabilities is required at the network nodes of the core network to ensure efficient routing of network traffic in disastrous scenario. This problem is referred to as capacity-bounded lightpath (CBL) problem. We proposed an exact algorithm which addresses this problem by considering the channel capacity of each link in addition to distances. The performance of the proposed algorithm is evaluated through simulation for three parameters: link capacity, connection requests and un-used links. It is revealed that existing shortest path algorithm improves the performance in terms of blocking probability of links and lightpaths at the cost of underutilization of the network capacity. Whereas, proposed algorithm regulates the capacity utilization by prioritizing link capacity over link length to establish more optimal shortest lightpath against connection requests

On spatially disjoint lightpaths in optical networks

The core network in the information communication technology infrastructure is based on the optical fiber technology. The core network is of prime importance because it connects all the central offices in the wired communication networks and the mobile switching centers in the wireless communication networks. The optical link between two network nodes is a lightpath, which offers very high speed, low loss, lower cost, highly reliable, secure and very high capacity, end-to-end communication over a very long distance. Any damage to a lightpath in the event of a disaster may lead to massive service interruptions and financial losses for the network operators. Therefore, survivable routing in these networks is very important. Generally, the survivability is ensured by having a backup lightpath to keep communication intact because the primary and the backup light paths are always disjoint. However, they may still fail simultaneously in the event of a large-scale disaster, if their separation distance in the physical plane is small. Hence, the spatial distance between the disjoint lightpaths should also be taken into consideration when establishing the lightpaths. Our contributions in this paper are twofold: (1) a routing algorithm is proposed for provisioning a pair of link-disjoint lightpaths between two network nodes such that their minimum spatial distance (while disregarding safe regions) is maximized, and (2) another routing algorithm is proposed for provisioning a pair of link-disjoint lightpaths such that the path weight of the primary lightpath is minimized, subject to the constraint that the backup lightpath has some particular geographical distance from the primary lightpath. Through extensive simulations, we show that our first algorithm can provide maximum survivability against spatial-based simultaneous link failures (due to the maximized spatial distance), whereas the second algorithm can tune the spatial distance between the lightpaths keeping in view the target survivability requirements and the path weight for the primary lightpath

Disaster-Resilient Optical Network Survivability: A Comprehensive Survey

Network survivability endeavors to ensure the uninterrupted provisioning of services by the network operators in case of a disaster event. Studies and news reports show that network failures caused by physical attacks and natural disasters have significant impacts on the optical networks. Such network failures may lead to a section of a network to cease to function, resulting in non-availability of services and may increase the congestion within the rest of the network. Therefore, fault tolerant and disaster-resilient optical networks have grasped the attention of the research community and have been a critical concern in network studies during the last decade. Several studies on protection and restoration techniques have been conducted to address the network component failures. This study reviews related previous research studies to critically discuss the issues regarding protection, restoration, cascading failures, disaster-based failures, and congestion-aware routing. We have also focused on the problem of simultaneous cascading failures (which may disturb the data traffic within a layer or disrupt the services at upper layers) along with their mitigating techniques, and disaster-aware network survivability. Since traffic floods and network congestion are pertinent problems, they have therefore been discussed in a separate section. In the end, we have highlighted some open issues in the disaster-resilient network survivability for research challenges and discussed them along with their possible solutions

Modelling and Performance Analysis of Visible Light Communication System in Industrial Implementations

Visible light communication (VLC) has a paramount role in industrial implementations, especially for better energy efficiency, high speed-data rates, and low susceptibility to interference. However, since studies on VLC for industrial implementations are in scarcity, areas concerning illumination optimisation and communication performances demand further investigation. As such, this paper presents a new modelling of light fixture distribution for a warehouse model to provide acceptable illumination and communication performances. The proposed model was evaluated based on various semi-angles at half power (SAAHP) and different height levels for several parameters, including received power, signal to noise ratio (SNR), and bit error rate (BER). The results revealed improvement in terms of received power and SNR with 30 Mbps data rate. Various modulations were studied to improve the link quality, whereby better average BER values of 5.55 × 10⁻¹⁵ and 1.06 × 10⁻¹⁰ had been achieved with 4 PAM and 8 PPM, respectively. The simulation outcomes are indeed viable for the practical warehouse model