All optical Networks

In this paper, we have proposed a new approach of routing and wavelength assignment algorithms, called Possible Available Wavelength (PAW) algorithm. The weight of a link is used as the main factor for routing decision in PAW algorithm. The weight of a link is defined as a function of hop count and available wavelengths. This function includes a determination factor of the number of wavelengths that are being used currently and are supposed to be available after a certain time. The session requests from users will be routed on the links that has the greatest number of link weight by using Dijkstra's shortest path algorithm. This means that the selected lightpath will has the least hop count and the greatest number of possible available wavelengths. The impact of proposed link weight computing function on the blocking probability and link utilization is investigated by means of computer simulation and comparing with the traditional mechanism. The results show that the proposed PAW algorithm can achieve the better performance in terms of the blocking probability and link utilization.

In this paper, we have proposed the new link-weight calculating function using for routing decision in WDM networks. The proposed link-weight calculating functions includes following factors those are available wavelengths per link, distance loss, total wavelengths, and limited wavelength conversion. The calculated link-weight is applied into the algorithm of routing decision in order to determine the available lightpath that qualifies user requests. The objective is to improve the performance of wavelengths assignment with fast determining the suitable lightpath by using the proposed link-weights calculating function. The analytical model of WDM switching networks is introduced for numerical analysis. The link-weight calculating function is performed. Finally, the performance of proposed algorithm is displayed with numerical results in term of the blocking probability, the probability that connection requests from users are rejected due to there are no available lightpath to be assigned for them. It is also shown that the blocking probability is varied in depending on the number of available wavelengths and the degree of wavelength conversion. The numerical results also show that the proposed link-weight calculating function is more cost-effective choice for the routing decision in WDM switching networks.

In this paper, we have proposed the new link-weight calculating function using for routing decision in WDM networks. The proposed link-weight calculating functions includes following factors those are available wavelengths per link, distance loss, total wavelengths, and limited wavelength conversion. The calculated link-weight is applied into the algorithm of routing decision in order to determine the available lightpath that qualifies user requests. The objective is to improve the performance of wavelengths assignment with fast determining the suitable lightpath by using the proposed link-weights calculating function. The analytical model of WDM switching networks is introduced for numerical analysis. The link-weight calculating function is performed. Finally, the performance of proposed algorithm is displayed with numerical results in term of the blocking probability, the probability that connection requests from users are rejected due to there are no available lightpath to be ass...

We have studied the tunneling of a circularly polarized optical vortex (OV) in parallel strongly spun el liptical fibers. In this case it is possible to route the OV in a pure state from one of the fibers to another. We have determined the power efficiency of this process and have shown that such a directional coupler can serve for inversion of the topological charge of the incoming vortex.

Optical networking, with its almost unlimited bandwidth, is the only technology that can support communication new applications with high demand for bandwidth such as remote visualization, teleimmersion, collaborative e-science etc. In the optical networks presently deployed, each link is optically isolated by transponders doing O/E/O conversions. But these transponders are quite expensive and lack transparency; hence there is a strong motivation to use large all-optical networks. In all-optical networks, all routes need not have adequate signal quality. To provide reliable and transparent service, there is a strong interest in the industry for routing protocols that take into consideration the impairments of optical layer that degrade quality of the signal. We present a new routing protocol that uses information about the quality of signal to select paths in an all-optical network. Our simulations confirm that this new protocol reaches higher network utilization compared to existing ones.

Abstract— In this paper an all-optical serial-to-parallel converter (SPC) based on the symmetric Mach-Zehnder (SMZ) interferometers operating at 80 Gb/s is presented. The proposed SPC is simulated and in particular its crosstalk (CXT) characteristics is investigated for a range of ...

The complexity of battery-powered autonomous devices such as Internet of Things (IoT) nodes or Unmanned Aerial Vehicles (UAV) and the necessity to ensure an acceptable quality of service, reliability, and security, have significantly increased their energy demand. In this paper, we discuss using a diffusion approximation process to approximate the dynamic changes in the energy content of a battery. We consider the case when energy harvesting sources are constantly charging the battery. The model assumes a probabilistic consumption and delivery of energy, giving the time-dependent distributions of the energy at the battery, of the time remaining until it becomes empty, the time required to charge the battery to its total capacity, or the time it is operational between two moments of complete depletion. When possible, we compare the diffusion approximation results with corresponding Markovian models.

The performance of tunable all-optical wavelength converters based on four-wave mixing in optical fibers is experimentally tested in a field-trial network. Two converters were built with two different fibers. The first one was made with a small variation in the zero-dispersion wavelength (ZDW) dispersion shifted fiber and the second one with a highly nonlinear fiber that presents great ZDW variations. In order to compare the tuning ranges obtained in both cases we present an experimental spectral analysis. Numerical simulations that consider the influence of both the dispersion slope and the long-scale ZDW variations of the fiber complement the experiments. The tuning bandwidth was larger in the highly nonlinear fiber case. For a set of different optical signal-to-noise ratios, the measurements of the Q-factor of the signal and those of the converted wave are our main results. These results show that the penalty imposed by the converters is different for each converted wavelength. The maximum penalty obtained for the Q-factor was $6 dB, but it was 63 dB for most cases. In all experiments we used a technique based on a dynamic polarization controller in order to avoid power fluctuations in the converted wave caused by polarization induced variations in the signal.

Abstract: We survey the theoretical results obtained for wavelength routing in all–optical networks, present some new results and propose several open problems. In all–optical networks the vast band-width available is utilized through wavelength division multiplexing : a ...

The shortest path problem exists in variety of areas. There are many algorithms to solve the shortest path problems. Dijkstra's algorithm is the most popular algorithm among that. It is an optimal and efficient algorithm till date and follows the label-setting paradigm. Dijkstra’s algorithm finds the optimum shortest-path and so it is a type of greedy algorithm. Many algorithms are modified and improved based on this algorithm. This paper presents a survey of improved algorithms based on Dijkstra’s algorithm that are applied in different application areas.

A deflection routing algorithm that can be applied to a novel self-routing address scheme for networks with arbitrary topology is proposed. The proposed deflection routing algorithm can be implemented all-optically using bitwise optical logic gates. Besides the primary output link selection, alternate output link choices by a packet at each node in case of deflection are also encoded in the address header. Priority classes can also be defined in the proposed address scheme. The performance of the deflection routing algorithm is studied using the AT&T North America OC-48 optical fiber network topology.

Optical network is an emerging technology for data communication inworldwide. The information is transmitted from the source to destination through the fiber optics. All optical network (AON) provides good transmission transparency, good expandability, large bandwidth, lower bit error rate (BER), and high processing speed. Link failure and node failure haveconsistently occurred in the traditional methods. In order to overcome the above mentioned issues, this paper proposes a robust software defined switching enabled fault localization framework (SDSFLF) to monitor the node and link failure in an AON. In this work, a novel faulty node localization (FNL) algorithm is exploited to locate the faulty node. Then, the software defined faulty link detection (SDFLD) algorithm that addresses the problem of link failure. The failures are localized in multi traffic stream (MTS) and multi agent system (MAS). Thus, the throughput is improved in SDSFLF compared than other existing methods like tra...

The utilization of a bismuth-substituted iron garnet as a magnetooptic Faraday rotator (MOFR) has been reported for all-optical networking purposes as well as for other applications. Our measurements and observations demonstrate that the MOFR saturates once a significantly large magnetic field (>225 G) is applied. After the applied magnetic field enters the saturation region, the material's magnetic domains can become pinned at intermediate levels of magnetization. Pinning in this form has not been reported nor well studied for this application. In this paper, a method to detect and describe anomalous pinning in terms of Faraday rotation is presented. Measurements on the changes in the state of polarization that a pinned material produces are examined. This paper will also present practical methods for unpinning the MOFR material, which are traditionally considered to be challenging.

This paper describes the problematic of filter narrowing effect in the context of next generation elastic optical networks. First, three possible scenarios are introduced: the transition from actual fixed-grid to a flexi-grid network; the generic full flexi-grid network; and a proposal for filterless optical network. Next, we investigate different transmission techniques and evaluate the penalty introduced by the filtering effect when considering: Nyquist WDM, SSB DD-OFDM and symbol-rate variable DP-4QAM. Also, different approaches to compensate for the filter narrowing effect are discussed. Results show that the specific needs per each scenario can be fulfilled by the aforementioned technologies and techniques, or a combination of them, when balancing performance, network reach and cost.

Optical time division multiplexing is an emerging and promising alternative for future high-speed photonic networks because of its ability to accommodate higher bit rate and flexible bandwidth. Symmetric Mach-Zehnder (SMZ) have been found to be the most suitable switching element than all the available de-multiplexing switches because of compact size, thermal stability, and low-power operation. In this paper, we simulate eight-channel OTDM systems (all-channel multiplexer and de-multiplexer (DEMUX)) with a Mach-Zehnder modulator and SMZ de-multiplexer to investigate the impact of control signal power and to calculate the crosstalk.

Optical network is an emerging technology for data communication inworldwide. The information is transmitted from the source to destination through the fiber optics. All optical network (AON) provides good transmission transparency, good expandability, large bandwidth, lower bit error rate (BER), and high processing speed. Link failure and node failure haveconsistently occurred in the traditional methods. In order to overcome the above mentioned issues, this paper proposes a robust software defined switching enabled fault localization framework (SDSFLF) to monitor the node and link failure in an AON. In this work, a novel faulty node localization (FNL) algorithm is exploited to locate the faulty node. Then, the software defined faulty link detection (SDFLD) algorithm that addresses the problem of link failure. The failures are localized in multi traffic stream (MTS) and multi agent system (MAS). Thus, the throughput is improved in SDSFLF compared than other existing methods like tra...

Optical network is an emerging technology for data communication
inworldwide. The information is transmitted from the source to destination through the fiber optics. All optical network (AON) provides good transmission transparency, good expandability, large bandwidth, lower bit error rate (BER), and high processing speed. Link failure and node failure haveconsistently occurred in the traditional methods. In order to overcome the above mentioned issues, this paper proposes a robust software defined switching enabled fault localization framework (SDSFLF) to monitor the node and link failure in an AON. In this work, a novel faulty node localization (FNL) algorithm is exploited to locate the faulty node. Then, the software defined faulty link detection (SDFLD) algorithm that addresses the problem of link failure. The failures are localized in multi traffic stream (MTS) and multi agent system (MAS). Thus, the throughput is improved in SDSFLF compared than other existing methods like traditional routing and wavelength assignment (RWA), simulated annealing (SA) algorithm, attackaware RWA (A-RWA) convex, longest path first (LPF) ordering, and biggest source-destination node degree (BND) ordering. The performance of the proposed algorithm is evaluated in terms of network load, wavelength utilization, packet loss rate, and burst loss rate. Hence, proposed SDSFLF assures that high performance is achieved than other traditional techniques.

We present two routing algorithms based on deflection and convergence, which are able to provide high bandwidth and an ending guarantee for the end-to-end delay in a core network. We study the performance of these routing techniques by using simulations, and we prove the bounds on the delay.

This paper describes the problematic of filter narrowing effect in the context of next generation elastic optical networks. First, three possible scenarios are introduced: the transition from actual fixed-grid to a flexi-grid network; the generic full flexi-grid network; and a proposal for filterless optical network. Next, we investigate different transmission techniques and evaluate the penalty introduced by the filtering effect when considering: Nyquist WDM, SSB DD-OFDM and symbol-rate variable DP-4QAM. Also, different approaches to compensate for the filter narrowing effect are discussed. Results show that the specific needs per each scenario can be fulfilled by the aforementioned technologies and techniques, or a combination of them, when balancing performance, network reach and cost.

We have developed a data transparent optical packet switch prototype employing wavelength conversion based on four-wave mixing. The switch is composed of an electro-optical control unit and an all-optical switching segment. To achieve higher switching efficiencies, Ge-doped silica suspended-core and chalcogenide arsenicselenide single-mode fibers were experimentally evaluated and compared to conventional highly-nonlinear fiber. Improved connectorization technology has been developed for Ge-doped suspended-core fiber, where we achieved connection losses of 0.9 dB. For the arsenic-selenide fiber we present a novel solid joint technology, with connection losses of only 0.25 dB, which is the lowest value presented up-todate. Conversion efficiency of -13.7 dB was obtained for the highly-nonlinear fiber, which is in perfect correlation with previously published results and thus verifies the functionality of the prototype. Conversion efficiency of -16.1 dB was obtained with arsenic-selenid...

he editorial calendar of IEEE Communications Magazine contains several topics relating to optical networking. This witnesses the increasing interest in optical technology to provide networking solutions for the huge growth of traffic. We would like to mention here the motivations for this feature topic specifically dedicated to optical networking solutions for next-generation Internet networks. The first issue is the significant growth of data traffic, mainly driven by Internet-based services. Several statistics and forecasts have already been reported in the literature, comparing the evolution of CP traffic to that of traditional telephone traffic. As usual, such predictions can fail in the details, the crossing points get shifted in the time frame: however, it is clear that data traffic will play a dominant role in the future of telecommunications. Actually, the traditional telecom and datacom worlds are converging. The revolution in what is generally named the "infocom" area is having an impact on the market, industrial, and scientific environments. Several solutions have been introduced so far providing optical transport of 1P packets. In particular, under the acronym IPoWDM (for IP over wavelength-division multiplexing(, different solutions are already a reality in the telecom/datacom market. However, on one hand the features of optical networking, and on the other the properties of the packet switched networks are still not adequately exploited. Optical technology is used only to provide transport in the backbone. However, several research activities have been carried out on the topic of photonic packet switching, with the aim of fully exploiting the optical technology characteristics and the advantages of packet switching. Unfortunately, the technology for optical memory seems not yet mature enough to consider this viable, at least in the short/medium term. Solutions based on optical packet switching cannot be provided soon. These considerations push for networking solutions somewhere between simple optical transport (e.g., IPoWDM) and optical packet switching. For instance,

2 Abstract- In this paper, we present self-switching mechanism using Semiconductor Optical Amplifier (SOA)-assisted Mach-Zehnder interferometer (MZI) considering dynamic gain response of the SOA. The effect of key structural and input pulse parameters of an all-optical MZI self-switches is identified and their role in the operation of self-switch is analyzed. The optimum values of these parameters must be correctly selected and adapted so as to ensure the satisfaction of the best operating conditions. Simulation results demonstrate that key parameters must be suitably must be modified to the specific all-optical self-switching application.

Στην παρούσα ερευνητική εργασία παρουσιάζεται η εφαρμογή των αλγόριθμων Dijkstra και Bellman-Ford στο χώρο των εγκαταστάσεων της πανεπιστημιούπολης Σερρών του Διεθνούς Πανεπιστημίου Ελλάδος, για την προσέγγιση των συντομότερων διαδρομών από επιλεγμένες θέσεις, σε διάφορα κτίρια. Οι εγκαταστάσεις του εκπαιδευτικού ιδρύματος αναπαραστάθηκαν με τη μορφή γράφου, του οποίου οι κορυφές είναι επιλεγμένες θέσεις και κτίρια, ενώ οι ακμές είναι οι διαδρομές, με τα βάρη τους να αντιπροσωπεύουν τα μήκη τους. Η λήψη αποφάσεων για τη δημιουργία των βέλτιστων διαδρομών και ο σχεδιασμός χαρτών με αποτυπωμένες τις προτεινόμενες διαδρομές, αποτελούν ένα πολύπλοκο πρόβλημα το οποίο μπορεί να επιλυθεί με την εφαρμογή αλγόριθμων συντομότερων μονοπατιών. Συμπερασματικά, η εφαρμογή των αλγόριθμων Dijkstra και Bellman-Ford έδειξε ότι είναι αποτελεσματικοί για την προσέγγιση των βέλτιστωνσυντομότερων διαδρομών και μπορούν να εφαρμοστούν με επιτυχία στο σχεδιασμό πολυπλοκότερων διαδρομών. Τέλος η εφαρμογή δύο διαφορετικών αλγορίθμων που προσεγγίζουν το ίδιο πρόβλημα επιτρέπει την επιβεβαίωση της εγκυρότητας των αποτελεσμάτων τους. Λέξεις κλειδιά: αλγόριθμος Dijkstra, αλγόριθμος Bellman-Ford, γράφοι, συντομότερη διαδρομή, χάρτες διαδρομών.

This research deals with applying the Dijkstra algorithm and Welch-Powell algorithm to on-campus bus transportation problems. This research aims to determine the optimal solution of campus bus transportation routes in the shortest routes and schedules. In determining the fastest way, each intersection represented as a node, and the path described as the sides. The shortest path obtained    V1 - V2 - V5 - V8 - V9 - V10 - V13 - V16.  In determining the optimal schedule, the number of buses represents the vertices, and the time expresses the side that connects each node. The optimal program of the bus starts from 06.30 am to 5.00 pm. Every bus gets four sessions of departure and four sessions return with travel time each session is 60 minutes.

Στην παρούσα ερευνητική εργασία παρουσιάζεται η εφαρμογή των αλγόριθμων Dijkstra και Bellman-Ford στο χώρο των εγκαταστάσεων της πανεπιστημιούπολης Σερρών του Διεθνούς Πανεπιστημίου Ελλάδος, για την προσέγγιση των συντομότερων διαδρομών από επιλεγμένες θέσεις, σε διάφορα κτίρια. Οι εγκαταστάσεις του εκπαιδευτικού ιδρύματος αναπαραστάθηκαν με τη μορφή γράφου, του οποίου οι κορυφές είναι επιλεγμένες θέσεις και κτίρια, ενώ οι ακμές είναι οι διαδρομές, με τα βάρη τους να αντιπροσωπεύουν τα μήκη τους. Η λήψη αποφάσεων για τη δημιουργία των βέλτιστων διαδρομών και ο σχεδιασμός χαρτών με αποτυπωμένες τις προτεινόμενες διαδρομές, αποτελούν ένα πολύπλοκο πρόβλημα το οποίο μπορεί να επιλυθεί με την εφαρμογή αλγόριθμων συντομότερων μονοπατιών. Συμπερασματικά, η εφαρμογή των αλγόριθμων Dijkstra και Bellman-Ford έδειξε ότι είναι αποτελεσματικοί για την προσέγγιση των βέλτιστωνσυντομότερων διαδρομών και μπορούν να εφαρμοστούν με επιτυχία στο σχεδιασμό πολυπλοκότερων διαδρομών. Τέλος η εφαρμογή δύο διαφορετικών αλγορίθμων που προσεγγίζουν το ίδιο πρόβλημα επιτρέπει την επιβεβαίωση της εγκυρότητας των αποτελεσμάτων τους. Λέξεις κλειδιά: αλγόριθμος Dijkstra, αλγόριθμος Bellman-Ford, γράφοι, συντομότερη διαδρομή, χάρτες διαδρομών.

The performance of microphotonic-silicon devices in a geographically-distributed optical fiber network is experimentally investigated. Two different devices are tested: an optical filter based on a silicon ring resonator and an all-optical wavelength converter based on four-wave mixing in a dispersion-tailored highly nonlinear silicon waveguide. The evaluation of the devices is performed by means of eye diagrams and measurements of the bit error rate.

We present the approach of cognition applied to heterogeneous optical networks developed in the framework of the EU project CHRON: Cognitive Heterogeneous Reconfigurable Optical Network. We introduce and discuss in particular the technologies and techniques that will enable a cognitive optical network to observe, act, learn and optimizes its performance, taking into account its high degree of heterogeneity with respect to quality of service, transmission and switching techniques.

All-optical networks have been largely investigated due to their high data transmission rates. The key to the high speeds in alloptical networks is to maintain the signal in optical form, to avoid the overhead of conversion to and from electrical form at the intermediate nodes. In the traditional WDM technology the spectrum of light that can be transmitted through the optical fiber has been divided into frequency intervals of fixed width with a gap of unused frequencies between them. In this context the term wavelength refers to each of these predefined frequency intervals. An alternative architecture emerging in very recent studies is to move towards a flexible model in which the usable frequency intervals are of variable width. Every lightpath is assigned a frequency interval which remains fixed through all the links it traverses. Two different lightpaths using the same link have to be assigned disjoint sub-spectra. This technology is termed flex-grid or flex-spectrum. The introduction of this technology requires the generalization of many optimization problems that have been studied for the fixed-grid technology. Moreover it implies new problems that are irrelevant or trivial in the current technology. In this work we focus on bandwidth utilization in path toplogy and consider two wavelength assignment, or in graph theoretic terms coloring, problems where the goal is to maximize the total profit. We obtain bandwidth maximization as a special case.

The article presents a diffusion approximation model applied to investigate the process of filling a large optical packet by smaller and coming irregularly electronic packets. The use of diffusion approximation enables us to include the general distributions of interarrival times, also the self-similarity of the input process, as well as to investigate transient states. We propose a novel diffusion process with jumps representing the end of the filling the buffer due to arrival of too large packet and we give the transient solution to this process. The model allows us to study the distribution of interdeparture times and the distribution of the space occupied in the optical packet.

This paper investigates offline planning and scheduling in transparent optical networks for a given periodic traffic demand. The main objective is to minimize the number of transceivers needed which make up for the main network cost. We call this problem "Scheduled Virtual Topology Design" and consider two variants: non-reconfigurable and reconfigurable equipment. We formulate both problems as exact MILPs (Mixed Integer Linear Programs). Due to their high complexity, we propose a more scalable tabu search heuristic approach, in conjunction with smaller MILP formulations for the associated subproblems. The main motivation of our research efforts is to assess the benefits of using reconfigurable equipment, realized as a reduction in the number of required transceivers. Our results show that the achieved reductions are not very significant, except for cases with large network loads and high traffic variability. Index Terrms-All-optical networks, virtual topology design, multilayer optimization, scheduling, tabu search. I.

All-optical exclusive OR (XOR) gate with semiconductor optical amplifier (SOA)-Mach-Zehnder interferometer (MZI) and delayed interferometer (DI) is demonstrated at 320 Gb/s through numerical simulation and analysis. The performance of the XOR gate is investigated and evaluated against the quality factor (QF). The obtained results indicate that placing the DI in series with the SOA-MZI renders acceptable QF of the XOR outcome at the target data rate, as opposed to the case without the DI, where the achievement of the same goal is not possible.

New generations of robotic systems capable of taking care of human-level tasks are becoming more and more desirable especially if considering the lack of human support in health-care assistance for the elderly. Assistive Robotics is a growing research field that is also applied to support both older adults and caregivers in a variety of situations and contexts. It leverages and integrates results from different research areas like e.g., Artificial Intelligence (AI), Cognitive Systems, Psychology and of course Robotics. Concerning AI, many of the technological skills that assistive robots could benefit of to achieve their objectives represent important challenges for that field. Some of the most relevant are the capability of monitoring and understanding information coming from the environment, the capability of interacting with humans in a flexible and human-compliant way, the capability of proactively performing supporting tasks inside the environment and also the capability of per...

Abstract: We survey the theoretical results obtained for wavelength routing in all–optical networks, present some new results and propose several open problems. In all–optical networks the vast band-width available is utilized through wavelength division multiplexing : a ...

A novel all-optical set/reset flip flop ͑AOFF͒ based on a symmetric Mach-Zehnder switch with a feedback loop and multiple forward set/reset signals is presented. The proposed flip flop has a fast response, a flat output gain, and a short switching-on interval of a few hundreds of picoseconds regardless of the associated feedback-loop delay. It is shown that a high on/off constrast ratio at the AOFF output is achieved above 20 dB.

The performance of microphotonic-silicon devices in a geographically-distributed optical fiber network is experimentally investigated. Two different devices are tested: an optical filter based on a silicon ring resonator and an all-optical wavelength converter based on four-wave mixing in a dispersion-tailored highly nonlinear silicon waveguide. The evaluation of the devices is performed by means of eye diagrams and measurements of the bit error rate.

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 Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Numerical simulations and experiments demonstrate the equivalence of two self-switches based on semiconductor optical amplifiers, namely the nonlinear polarization switch and the Mach-Zehnder interferometer. This equivalence is highlighted by introducing a one-to-one functional similarity among the switch components. By means of a detailed study on gain and phase difference variations in both switches, we introduce a method to determine the configurations in which the switches exhibit an equivalent power transfer function. Their operational equivalence is experimentally confirmed.

The paper introduces a new analytical approach for estimating blocking probabilities in all-optical networks. The assumptions of the classical Lee approximation are discussed and their effects are evaluated. The paper proposes a better substitute for the independent link assumption. The new assumption takes all active paths, as well as all free links, as independent objects on the network topology. The new model is shown to generate estimates that fit exactly the blocking probabilities obtained through simulations on linear topologies using Poissonian, spatially homogeneous traffic. A extension to regular meshes is presented that is asymptotically good for very small and very large nodal degrees. Finally, the independent wavelength assumption is also evaluated for two different wavelength assignment algorithms.

All-optical networks with multiple fibers lead to several interesting optimization problems. In this paper, we consider the problem of minimizing the total number of fibers necessary to establish a given set of requests with a bounded number w of wavelengths, and the problem of maximizing the number of accepted requests for given fibers and bounded number w of wavelengths. We study both problems in undirected tree networks T = (V, E) and present approximation algorithms with ratio 1 + 4|E| log |V |/OPT and 4 for the former and with ratio 2.542 for the latter. Our results can be adapted to directed trees as well.

In this paper, we propose and experimentally demonstrate a novel technique to generate ultrawideband (UWB) doublet pulses by exploiting the cross-phase modulation (XPM) in a semiconductor optical amplifier (SOA). The key component in the proposed system consists on an integrated SOA Mach-Zehnder interferometer (MZI) pumped with a Gaussian pulse modulated optical carrier. The transfer function of the nonlinear conversion process leads to the generation of UWB doublet pulses through the control of the biasing point of the SOA-MZI.

Full measurement of the polarization of light at the nanoscale is expected to be crucial in many scientific and technological disciplines. Ideally, such measurements will require miniaturized Stokes polarimeters able to determine polarization nondestructively, locally, and in real time. For maximum robustness in measurement, the polarimeters should also operate optimally. Recent approaches making use of plasmonic nanostructures or metasurfaces are not able to fulfill all these requirements simultaneously. Here, we propose and demonstrate a method for subwavelength-footprint Stokes nanopolarimetry based on spin-orbit interaction of light. The method, which basically consists on a subwavelength scatterer coupled to a (set of) multimode waveguide(s), can fully determine the state of polarization satisfying all the previous features. Remarkably, the nanopolarimetry technique can operate optimally (we design a nanopolarimeter whose polarization basis spans 99.7% of the maximum tetrahedro...

Plug and play optical (PPO) nodes may be used to facilitate the deployment of optical networks. PPO nodes must be able to learn about the signal propagation properties of the surrounding optical fibers and make their wavelength routing decisions based on the collected data. This paper discusses what are the open challenges that must be overcome to provide cost effective and performing ad hoc networking solutions based on PPO nodes.

The paper presents a novel N-channel chained symmetric-Mach-Zehnder-interferometers demultiplexer (CSMZI) for high-speed OTDM networks. The proposed scheme offers parallel demultiplexing capability with reduced complexity. Simulation results show that low bit error rate performance is achieved with low power penalty.

The magneto-optical (MO) effects not only are a powerful probe of magnetism and electronic structure of magnetic solids but also have valuable applications in high-density data-storage technology. Yttrium iron garnet (Y$_3$Fe$_5$O$_{12}$) (YIG) and bismuth iron garnet (Bi$_3$Fe$_5$O$_{12}$) (BIG) are two widely used magnetic semiconductors with strong magneto-optical effects and have also attracted the attention for fundamental physics studies. In particular, YIG has been routinely used as a spin current injector. In this paper, we present a thorough theoretical investigation on magnetism, electronic, optical and MO properties of YIG and BIG, based on the density functional theory with the generalized gradient approximation plus onsite Coulomb repulsion. We find that both semiconductors exhibit large MO effects with their Kerr and Faraday rotation angles being comparable to that of best-known MO materials such as MnBi. Especially, the MO Kerr rotation angle for bulk BIG reaches -1.2...