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Photonic crystal fiber is a category of optical fibers, getting great attention by its promise to offer a range of optical characteristics that are not achievable in conventional optical fibers. Engineered dispersion and nonlinear characteristics of photonic crystal fiber (PCF) make it an attractive candidate for nonlinear optics and advanced optical networking in the all-optical domain. An optical network consists of different optical components such as laser sources, amplifiers, regenerators, and convertors for proper signal transmission over long distances. In recent years, the performance of the components has been improving by employing the appealing properties of PCF. The PCF's application on such components is discussed, and the simulated results on gain amplification, regeneration, conversion, fiber laser are reviewed. These developments reveal that the enhanced performance provided by PCF makes it suitable for different optics applications. [ABSTRACT FROM AUTHOR]

All-optical networks (AON) assured a large bandwidth, high-speed switching, and QoS (Quality of Service) support. But due to the development of applications and services, new requirements are created in terms of, specifically resource utilization and QoS provision. To meet these demands, AON enabled core node architecture with multiple wavelength converters’ types involving full range wavelength converter (FRWC) having a significant cost. To reduce the cost, a hybrid AON with composite node architecture combining wavelength converters (WC), Fiber delay line (FDL), and wavelength range (WR) are introduced. In this architecture, fixed and limited wavelength converters (FXWC, LRWC) are utilized while the FRWC converter is replaced by FDL. The proposed architecture decreased the presence and usage of WC, FDL, and WR while assuring QoS support. A lightpath cost formulation is computed based on WR, WC, and FDL enabled in the proposed node architecture to decrease converter and FDL numbers. The cost also managed the wavelength availability to ensure lightpath control and QoS support using real-time requirements, especially loss and blocking delay. The obtained results in the comparative study, conducted in the simulation work, showed that the novel approach performed better than the existing approaches. Moreover, our proposal optimized AON resources, particularly node architecture design, while providing QoS support according to the traffic parameters and requirements.

The protection of wavelength division multiplexed (WDM) networks can be achieved very successfully by pre-configured protection cycles (p-cycles). In these networks there is requirement of 100% wavelength conversion for working paths as well as for p-cycle protection paths requiring wavelength converters at every node. As wavelength converter is costly device so there is a need to use them efficiently. In this paper, we propose a heuristic approach of Optimal Wavelength Converter for p-Cycle (OWCP) to choose p-cycles with optimal wavelength converters. The developed algorithm gives cost effective solution of protecting WDM network using p-cycles with lesser number of converters. It reduces the optimization complexity and provides effective solution with reduction in computational time. [ABSTRACT FROM AUTHOR]

The pre-configured protection cycles (p-cycles) plays an important role in providing protection to WDM networks. In these networks working paths and protection paths via p-cycles should possess 100% wavelength conversion capability. This will necessitate the presence of wavelength converters at every node for both paths. The use of many converters will make the network highly expensive due to its high cost. We are investigating p-cycle protection with the use of optimal number of wavelength converters. It is found that instead of full wavelength conversion, changing the routing of working traffic with lesser converters path and dedicating single wavelength to every protected p-cycle will employ lesser converters. This will make the network less costly as fewer converters will be used for establishing working paths and p-cycles. However, spare capacity required will increase thereby increasing the fiber length. But this fiber added will cost much lesser as compared to high cost converters. [ABSTRACT FROM AUTHOR]

Abstract Background Liquid filled hollow core fiber Raman wavelength converters are devices enabling to red-shift the wavelength of laser beams delivered by either fixed wavelength or tunable lasers. Most of the reported converters operate in a pulsed regime with pulse durations comprised between a few hundreds of picoseconds and up to a few nanoseconds, and energy of a few micro-Joules. However, and depending on the pulse duration, the optimization of Raman converters turns to be rather challenging since the desired forward Raman scattering may compete with counter-propagating nonlinear effects like Raman and Brillouin back-scatterings. The Brillouin back-scattering is especially hard to cancel since the Brillouin gains are usually larger than the Raman gains. Techniques have already been investigated but are not fully satisfactory. Our aim in this paper is to propose a technique to optimize the Raman forward scattering and to minimize these back-scattering effects. Methods We compare the interaction lengths in the forward and backward directions in the above-mentioned temporal regimes. If the fiber length is higher that the backward effective length of interaction then the backward effects should decrease at the benefit of the forward Raman scattering. Numerical simulations enable to estimate more precisely how long the fiber should be to get large Raman conversion efficiency and negligible Brillouin scattering. Results and discussion To validate this technique we build two identical Raman converters differing only by the fiber lengths (0.5 m and 1.5 m). We present the experimental setup. The experimental results are confronted to the numerical simulations. As expected increasing the fiber length strongly decreases the Brillouin scattering. Conclusions We have proposed a simple and efficient solution to minimize Brillouin back-scattering in Raman wavelength converters by optimizing the fiber length. The experimental demonstration was conducted with low energy (≈ 6 μJ) but the energies should scale with the fiber effective area if more energy is needed, without affecting the conversion efficiencies.

We experimentally demonstrate, for the first time, the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm to improve the receiver performance of wavelength converting 40-Gb/s 16-quadrature amplitude modulation (16-QAM) and 30-Gb/s 64-QAM using four-wave mixing in semiconductor optical amplifier (SOA). Two novel modified DBSCAN methods are proposed, in which “un-clustered” received constellation points that are considered to be noisy points are further processed using method-(1) K-means and method-(2) the minimum distance between an unlabeled point and the clustered points. DBSCAN is more effective for distorted signals due to optical nonlinearities at higher than 25 and 30 dB of optical signal-to-noise ratios (OSNR) for 16- and 64-QAM, respectively. We find that DBSCAN can result in improvements in Q-factor by ~ 0.8 dB at optimum power when compared to linear equalization. The soft-clustering ability of DBSCAN method-(2) is particularly useful at high OSNR (30 dB) and high input signal powers in the SOA where excessive nonlinearity causes rotation of the outer-constellation points. Method-(1)’s hard clustering is valuable at lower input signal powers, where the clusters maintain a Gaussian-circular shape. [ABSTRACT FROM AUTHOR]

An all-fiber integrated nonlinear silicon photonic wavelength converter has been proposed and fabricated using the silicon core fiber platform. The silicon fiber was spliced directly to a conventional single mode fiber, facilitated via an inverse tapered nano-spike that helped to reduce the mode mismatch between the different core materials. Four-wave mixing-based wavelength conversion with an efficiency as high as −22.1 dB has been achieved for selected wavelengths across the C-band in a device length of only ~ 1 cm. Successful conversion of quadrature phase-shift keying signals at a 20-Gb/s bitrate, with a 1 to 2 dB penalty level at the bit error ratio $\text {(BER)} =3.8\times 10^{-3}$ , was used to demonstrate the suitability of the silicon fiber device for the construction of ultra-compact, all-fiber-based optical signal processing systems. [ABSTRACT FROM AUTHOR]

In this paper, we deal with the wavelength assignment and the converter placement problem in wavelength-routed optical WDM Mesh networks. Our objective is to try to assign wavelengths in an efficient manner with/without wavelength conversion to get a very low blocking probability and optimize the performance of the overall network. Thus, we implement and compare the performance of two proposed algorithms namely DWA "Dynamic Wavelength Assignment" and SWA "Static Wavelength Assignment" with well-known algorithms. We first present a literature review about previously proposed approaches, and then we introduce and evaluate our implemented approaches. We also discuss the wavelength converter placement problem in mesh networks. We finally corroborate our theoretical findings through extensive simulations. [ABSTRACT FROM AUTHOR]

Wavelength converters placement (WCP) in all-optical WDM networks belongs to the class of hard combinatorial optimization problems. So far, this problem has been solved by various heuristic strategies or by application of metaheuristic approaches such as genetic algorithms (GA), particle swarm optimization (PSO), differential evolution (DE), etc. In this paper, we introduce the application of Bee Colony Optimization (BCO) metaheuristic to solve the WCP problem in all-optical WDM networks. Numerous studies prove that BCO is a fast, robust and computationally efficient tool in tackling complex optimization problems. The objective of the proposed BCO-WCP algorithm is to find the best placement of limited number of wavelength converters in given optical network such that the overall network blocking probability is minimized. To evaluate the performances of the BCO-WCP algorithm, numerous simulation experiments have been performed over some realistic optical network examples. The blocking probability performance and computational complexity are compared with optimal solution obtained by exhaustive search (ES) approach as well as with DE and PSO metaheuristics. It will be shown that the BCO-WCP algorithm is not only be able to produce high quality (optimal) solution, but significantly outperforms the computational efficiency of other considered approaches.

We report the first demonstration of a single-pass dual-orthogonal-pump four-wave mixing-based wavelength conversion scheme in a silicon-based waveguide. The silicon germanium waveguide used was designed to exhibit strong TE/TM mode similarity across a broad wavelength range as well as a large nonlinear coefficient. A polarization-dependent loss of just 0.42 dB was measured, and the conversion of 40-Gb/s differential phase-shift keying signals was demonstrated with 1.5-dB power penalty at a bit error ratio of 10^-9 . [ABSTRACT FROM PUBLISHER]

In this letter, we demonstrate, for the first time, successful four wave mixing (FWM)-based wavelength conversion of binary phase shift keyed (BPSK) and quadrature phase shift keyed (QPSK) signals, at 20-Gb/s bitrate, in a 1-mm long amorphous silicon waveguide. A maximum FWM-efficiency of −26 dB was achieved by employing a pump power of just 70 mW, establishing this technology as a contender for the development of ultra-compact, low power, silicon photonics wavelength converter. Bit error ratio measurements demonstrated successful conversion with less than 1 dB penalty level, for both BPSK and QPSK signals (at \textrm BER = 10^-5 ). [ABSTRACT FROM PUBLISHER]

As Internet traffic will further increase in coming years, the current optical network infrastructure will have to grow along in terms of capacity. To this end, optical packet/burst switching have been proposed, allowing more efficient use of the available fibre capacity. To resolve packet contention in the involved optical switches, Fibre Delay Lines (for delay assignment) and wavelength converters (for wavelength conversion) are used to reschedule the contending packets, by means of a scheduling algorithm. Existing algorithms are effective in minimizing packet loss when employed with an infinite number of converters, but generally perform poorly when the number of wavelength converters is small, as is the case in most switch prototype architectures. In this paper, several parametric cost-based scheduling algorithms for a limited number of wavelength converters are proposed that take scarcity of both FDLs and converters into account. Results obtained by Monte Carlo simulation show that these algorithms not only enable improved performance (in terms of packet loss probability), but also reduce the usage of the wavelength converters, and thus, the switch׳s overall energy consumption. The new algorithms are of the same implementation complexity as existing cost-based algorithms, and thus are of immediate value to switch designers. [ABSTRACT FROM AUTHOR]

With ever-increasing demands for bandwidth, optical packet/burst switching is used to utilize more of the available capacity of optical networks. In existing prototypes of optical switches, packet contention is resolved by combining time and wavelength multiplexing by means of fiber delay lines and wavelength converters. Although optical switches dissipate less energy than their electronic counterparts, their consumption remains substantial. Since wavelength converters contribute significantly to the switches overall energy consumption, they should be powered only when needed. Existing scheduling algorithms, however, do not take the usage of wavelength converters (and the related energy consumption) into account. To this end, we developed and evaluated new cost-based scheduling algorithms, which take both gap and delay into account to schedule an incoming packet. The performance improvement of these algorithms over existing algorithms can be traded off for a significant reduction in up-time of the wavelength converters by introducing a conversion cost in the involved cost function. This is backed by Monte Carlo simulation results, in which the algorithms are applied both in a void-filling and non-void-filling setting. The algorithms are of the same implementation complexity as existing algorithms, and thus of immediate value to switch designers. [ABSTRACT FROM AUTHOR]

Multichannel wavelength conversion is experimentally demonstrated for high-speed 128 Gb/s dual-polarization quadrature phase-shift keying signals using four-wave mixing in a polarization diversity circuit with silicon nanowires as nonlinear elements. The wavelength conversion performance is investigated for both single- and three-channel input signals, showing quality factors well >9.8 dB (corresponding to bit-error-ratios better than 10^\mathrm \mathbf -3 ) and with a negligible power penalty compared with the back-to-back case. [ABSTRACT FROM PUBLISHER]

This study investigates a heuristic routing and wavelength assignment (RWA) scheme for an optical‐carrier‐reusable ring network. This network has two unique features. First, only one light source, called the multi‐carrier light source, is required which eases the difficulty of controlling many light source devices. Second, optical carriers are reused in order to improve the efficiency of wavelength usage. Given the target of wavelength‐resource‐efficient channel establishment, performance of the heuristic RWA scheme is evaluated. To realise efficient wavelength usage, the authors formulate the RWA problem as an integer linear programming (ILP) problem of obtaining the minimum number of required wavelengths for given requests. With the ILP approach, the calculation process is not tractable in practical time. The heuristic RWA scheme introduced in this study solves the RWA problem. This scheme consists of two algorithms. Channel routes are obtained by the routing algorithm, and the wavelength assignment algorithm is then performed to assign a wavelength to each route. Moreover, two candidates, considering the shortest path and considering the avoidance of wavelength conversion, for the routing algorithm are examined. Numerical results show that the first candidate is more suitable in terms of reducing the number of required wavelengths than the second candidate. [ABSTRACT FROM AUTHOR]

In the wavelength-division multiplexing network, high-performance optical wavelength converters are desired. This article will report very stable second harmonic generation by using tellurite glasses, second harmonic generation comparison in glass materials, and time-dependent change of second harmonic generation. We obtained 9 times larger second harmonic generation using TeO2 (60 mol%)–WO3 (30 mol%)–Bi2O3 (10 mol%) than using TeO2 (60 mol%)–WO3 (30 mol%)–PbO (10 mol%) glass. This value corresponds to 4.6 times higher than d11 constant of Y-cut quartz (0.4 pm/V). We have succeeded permanent poling by measurement of time-dependent change of second harmonic generation because there could not be found second harmonic generation intensity change after 6 months of poling at room temperature, and there was no decay of second harmonic generation intensity after 4 h of heating at 100°C. [ABSTRACT FROM PUBLISHER]

Abstract: This paper proposes new analytical models to study optical packet switching architectures with multi-fiber interfaces and shared wavelength converters. The multi-fiber extension of the recently proposed Shared-Per-Input-Wavelength (SPIW) scheme is compared against the multi-fiber Shared-Per-Node (SPN) scheme in terms of cost and performance for asynchronous traffic. In addition to using Markov chains and fixed-point iterations for modeling the mono-fiber case, a novel state aggregation technique is proposed to evaluate the packet loss in asynchronous multi-fiber scenario. The accuracy of the performance models is validated by comparison with simulations in a wide variety of scenarios with both balanced and imbalanced input traffic. The proposed analytical models are shown to remarkably capture the actual system behavior in all scenarios we tested. The adoption of multi-fiber interfaces is shown to achieve remarkable savings in the number of wavelength converters employed and their range. In addition, the SPIW solution allows to save, in particular conditions, a significant number of optical gates compared to the SPN solution. Indeed, SPIW allows, if properly dimensioned, potential complexity and cost reduction compared to SPN, while providing similar performance. [Copyright &y& Elsevier]

Optical Networks are data networks built on Fiber-Optics technology, which sends data digitally, as light through connected fiber strands. A Reconfigurable Optical Add-Drop Multiplexer (ROADM) is a form of optical add-drop multiplexer that adds the ability to remotely switch traffic from a Wavelength Division Multiplexing (WDM) system at the wavelength layer. In an optical packet network with optical packet switches interconnected with optical fibers running Wavelength Division Multiplexing (WDM), packets are transmitted from source to destination without any Optical- Electrical-Optical (O/E/O) conversion. The optical fiber entering an optical packet switch carries several wavelengths for packet transmission. [ABSTRACT FROM AUTHOR]

Powerful computing systems interconnected via high-bandwidth wavelength division multiplexing (WDM) fibers are becoming inevitable to meet the needs of emerging computation and communication applications. Enabling multicast over WDM links requires the use of multicast-capable optical cross-connects (MC-OXCs) equipped with power splitters to replicate and interconnect an input signal on a particular wavelength to one or more output fibers, possibly on different wavelengths. All existing design approaches for FW× FW strictly nonblocking MC-OXCs with F fibers, each carries W wavelengths require the use of power splitters with a fan-out degree of O( FW). For typical large values of F and W, complex and power-consuming active devices are needed to compensate for the lost power due to splitting. In this paper, we propose a new class of strictly nonblocking MC-OXC, namely, the Convert-and-Deliver (CAD) cross-connect to reduce power consumption. The new CAD OXC uses power splitters with a fan-out degree of only O( F) instead of O( FW). It is shown that, making the fan-out degree independent of W in the proposed design does not only reduce splitting power loss considerably, but it also enhances the scalability of the design. In particular, for any value of F, upgrading the number of wavelengths per fiber does not incur any changes to the fan-out degree or the power loss in the used splitters; a feature that cannot be obtained with any existing MC-OXC design approach. [ABSTRACT FROM AUTHOR]

Wavelength routing algorithms (WRAs) aware of Physical layer impairments (PLIs) have been proposed in order to manage the establishment of optical paths in wavelength-switched optical networks. However, if optical nodes incorporate regenerators/wavelength converters, PLI-aware WRAs should be devised in order to incorporate error accumulation in the signal in the PLI estimation and relaxation of the wavelength continuity constraint in the path calculation. In this paper, we utilize a new bit error rate performance estimation in combination with the PLI-aware WRA in order to systematically investigate the role of regeneration and wavelength conversion in optical networks. Based on the outcomes of the study, we also propose a path establishment algorithm that is based on the “instant” physical properties of the path and can dynamically adapt to the network state. This is proven beneficial as far as the blocking performance is concerned as it circumvents the weaknesses that appear in the traditional shortest distance path establishment algorithms in a PLI-aware environment that operates without the wavelength continuity constraint. [ABSTRACT FROM PUBLISHER]

Optical packet switching (OPS) is a promising technology to enable next-generation high-speed IP networks. A major issue in OPS is packet contention that occurs when two or more packets attempt to access the same output fiber. In such a case, packets may be dropped, leading to degraded overall switching performance. Several contention resolution techniques have been investigated in the literature including the use of fiber delay lines (FDLs), wavelength converters (WCs), and deflection routing. These solution typically induce extra complexity to the switch design. Accordingly, a key design objective for OPS is to reduce packet loss without increasing switching complexity and delay. In this paper, we investigate the performance of contention resolution in asynchronous OPS architectures with shared FDLs and WCs in terms of packet loss and average switching delay. In particular, an enhanced FDL-based and a novel Hybrid architecture with shared FLDs and WCs are proposed, and their packet scheduling algorithms are presented and evaluated. Extensive simulation studies show that the performance of proposed FDL-based architecture outperforms typical OPS architectures reported in the literature. In addition, it shown that, for the same packet loss ratio, the proposed hybrid architecture can achieve up to 30% reduction in the total number of ports and around 80% reduction in the overall length of fiber as compared to the FDL-based architectures. [ABSTRACT FROM AUTHOR]

The performance of relatively complex photonic integrated circuits (PICs) is now reaching such high levels that the long sought goal of realizing low-cost, –size, -weight, and -power chips to replace hybrid solutions seems to have been achieved for some applications. This tutorial traces some of the evolution of this technology that has led to an array of high-functionality InP-based PICs useful in optical sensing and communication applications. Examples of recent high-performance PICs that have arisen out of these developments are presented. [ABSTRACT FROM PUBLISHER]

A multi-wavelength copy interconnect is a switching network capable of replicating a signal arriving at the input on a specific wavelength to one or more outputs possibly on different wavelengths. Such an interconnect can be useful in building optical multicast switches for wavelength division multiplexing (WDM) networks. In this article, we investigate, for the first time, the problem of designing copy networks that can simultaneously multicast input signals to a set of outputs while changing the wavelength of the replica according to the required routing pattern. We propose a novel multi-wavelength crossbar (MWX) switch that can switch an input signal on a specific wavelength to two different output wavelengths. The proposed MWX is used as a building block to construct two classes of multi-log2 N copy networks, namely, baseline and Beneš interconnects. The design space of the proposed interconnect classes is characterized and their hardware complexity is analyzed. We show that the proposed interconnects are transparent to existing multicast routing algorithms, and present simple routing algorithms for routing of multicast requests over the proposed designs. Comparisons with existing designs confirm that the proposed interconnects require a smaller number of space switches and wavelength conversion processes as compared to most conventional copy networks. In particular, for a large number of wavelengths and for any number of fibers the proposed design requires 50% less switching elements as compared to best available designs. [ABSTRACT FROM AUTHOR]

Wavelength-routed all-optical networks have emerged as a popular architectural solution for wide area networks and are being conceived for future broadband communications. Call connection probability in such networks depends on the number of WDM wavelengths employed and on the capability for wavelength conversion at network nodes. Equipping all the network nodes with wavelength conversion capability to reduce the blocking probability is not a cost effective solution due to the high cost of wavelength converters (WC). Hence, networks equipped with converters at only some of the nodes are more practical. However, these nodes should be identified optimally so that network blocking probability is minimized. In this paper, wavelength converters based on four wave mixing (FWM) in semiconductor optical amplifiers (SOAs) is considered. In WDM all-optical networks, in-band crosstalk is regarded as one of the major transmission impairments. In-band crosstalk usually arises when multiple signals at identical or adjacent wavelengths pass through an optical crossconnect node. In-band crosstalk leads to increased receiver BER. This paper considers in-band crosstalk arising in a network which is equipped with wavelength converters. For every dynamically arriving connection request, a route is determined using Dijikstra’s algorithm and a free wavelength is determined using the random wavelength assignment. If no common free wavelength is available, connection is tried using wavelength converters, if available, on the given route. If wavelength assignment does not succeed, the call is blocked. If wavelength assignment succeeds, the BER at the destination node is computed before establishing the lightpath. If the estimated BER exceeds 10−12, the call is blocked. Otherwise, the call is admitted. The results reveal that wavelength converters are not useful in networks that already suffer from crosstalk conditions. [ABSTRACT FROM AUTHOR]

Abstract: Routing in wavelength-routed all-optical WDM networks has received much attention in the past decade, for which fixed and dynamic routing methods have been proposed. Taking into account the observation that wavelength-routed all-optical WDM networks are similar to circuit-switched voice networks, except with regard to wavelength conversion, we propose an adaptive alternate routing (AAR) scheme for wavelength-routed all-optical WDM networks. A major benefit of AAR is that it can operate and adapt without requiring an exchange of network status, i.e., it is an information-less adaptive routing scheme. The scope of this work is to understand this scheme in its own right since no other dynamic routing schemes are known to have the information-less property. In this paper, we conduct a systematic study of AAR with regard to factors such as the number of converters, load conditions, traffic patterns, network topologies, and the number of alternate paths considered. We observe that the routing scheme with multiple alternate routes provides more gain at a lower load instead of requiring any nodes to be equipped with wavelength converters. On the other hand, the availability of wavelength converters at some nodes, along with adaptive routing, is beneficial at a moderate to high load without requiring all nodes to be equipped with wavelength converters. We also observed that a small number of alternate routes considered in a network without wavelength converters gives a much better performance than a network with full wavelength converters and fewer alternate routes. Throughout this study, we observed that the proposed adaptive alternate routing scheme adapts well to the network traffic condition. [Copyright &y& Elsevier]

All-optical switched networks (AOSN), mainly optical label switching (OLS), guaranteed fast data transfer QoS support and network resource supervision. However, the emergence of new applications and services, having variable and various requirements, are produced new demands, notably in terms of QoS support and resource control. To meet these demands, a hybrid virtual topology (HVT), with multiple core node architectures employing wavelength converters (WC), fiber delay line (FDL), and deflection path (DP), is proposed. This HVT enables various node architectures to manage the availability and usage of the components, covering fixed, limited, and full range converters (FXWC, LRWC, and FRWC) also FDL. An advanced DP improves signaling and switching to supervise the potential HVT and AOSN resources while assuring QoS support. A lightpath cost is formulated to determine the potential lightpaths utilized to build the HVT guaranteeing AOSN resources and advanced traffic management. The obtained results of the conducted simulation and comparative study show that the optimized (O-HVT) approach performed better than the enhanced (E-HVT) and initial (I-HVT) approaches. Moreover, the O-HVT method optimizes AOSN resources, mainly core node architecture range, while providing QoS support for high load traffic with variable demands. [ABSTRACT FROM AUTHOR]

In this paper, we present a model that fully describes the quasi-stationary behavior of coherent anti-Stokes Raman scattering (CARS) in an anti-Stokes Raman converter operating at exact Raman resonance. We demonstrate that the CARS mechanism actually comprises two opposite and competing interactions, which respectively create and annihilate phonons in the Raman medium. Furthermore, we show that both the phase mismatch of the CARS four-wave mixing process and the level of pump depletion determine which of these two interactions takes place along the converter path length. In addition, we demonstrate that our CARS model is fully in line with seemingly contradictory findings in Raman conversion experiments. Finally, we discuss the fundamental differences between our CARS interpretation and the CARS models presented earlier. [ABSTRACT FROM AUTHOR]

In this paper, we study shortest-path routing in wavelength-routed optical networks with an objective to optimize the average-case running time for path computation. Four fast routing algorithms are proposed for dynamically computing the shortest lightpaths or semilightpaths in a network with or without wavelength converters. To reduce the average-case running time for path computation, sequential search, backward routing, and informed search are used in the algorithm design. Simulation results show that the proposed algorithms can significantly reduce the average-case computational overhead for path computation as compared with existing algorithms. [ABSTRACT FROM PUBLISHER]

We present an architecture for implementing optical buffers, based on the feed-forward-buffer concept, that can truly emulate input queuing and accommodate asynchronous packet and burst operation. The architecture uses wavelength converters and fixed-length delay lines that are combined to form either a multiple-input buffer or a shared buffer. Both architectures are modular, allowing the expansion of the buffer at a cost that grows logarithmically with the buffer depth, where the cost is measured in terms of the number of switching elements, and wavelength converters are employed. The architectural design also provides a tradeoff between the number of wavelength converters and their tunability. The buffer architectures proposed are complemented with scheduling algorithms that can guarantee lossless communication and are evaluated using physical-layer simulations to obtain their performance in terms of bit-error rate and achievable buffer size. [ABSTRACT FROM PUBLISHER]

An all-optical wavelength converter with a large wavelength hopping range is proposed and demonstrated. This converter consists of multistage cascaded wavelength converters using semiconductor optical amplifiers each with different gain band. Each of the cascaded wavelength converters enables us to perform both noninverted (NIV) and inverted (IV) operations. Conversion performance is compared at NIV and IV operations in terms of static characteristics as a function of input/output power of the converter. While good conversion performances are achieved at both operations, the IV wavelength conversion has better cascadability to obtain a high-quality converted signal for the cascaded scheme. Moreover, signal amplitude regeneration is demonstrated by repeating the IV wavelength conversion. Finally, we successfully demonstrate, for the first time, ultrawideband wavelength conversion, including over 300-nm wavelength hopping to the shorter wavelength side with a triple-stage cascaded wavelength converter [ABSTRACT FROM PUBLISHER]

We present the first monolithic widely tunable 40-Gb/s transceivers. The devices integrate sampled grating distributed Bragg reflector (SG-DBR) lasers, quantum-well electroabsorption modulators (EAM), low-confinement semiconductor optical amplifiers (SOA), and uni-traveling carrier (UTC) photodiodes for state-of-the-art light generation, modulation, amplification, and detection. A relatively simple high-flexibility fabrication scheme combining quantum-well intermixing (QWI) and blanket metal-organic chemical vapor deposition (MOCVD) regrowth was used to integrate components with performance rivaling optimized discrete devices. The SG-DBR/EAM transmitters demonstrate 30 nm of tuning, 39-GHz bandwidth, low-drive voltage, and low power penalty 40-Gb/s transmission through 2.3 km of fiber. The SOA/UTC photodetector receivers provide 23-28 dB of gain, saturation powers up to 18.6 dBm, and -20.2 dBm of chip-coupled sensitivity at 40 Gb/s. By connecting the transmitters and receivers off-chip, we demonstrate 40-Gb/s wavelength conversion [ABSTRACT FROM PUBLISHER]

Abstract: In this paper, we investigate the problem of enhancing dual-failure restorability in path protected mesh-restorable optical Wavelength Division Multiplexed (WDM) networks. Recent studies have demonstrated the need to survive simultaneous dual-link failures and have also provided solutions for handling such failures. A key finding of these early efforts is that designs providing complete (i.e. 100%) protection from all dual-failures need almost triple the spare capacity compared to a system that protects against all single-link failures. However, it has also been shown that systems designed for 100% single-link failure protection can provide reasonable protection from dual-link failures [M. Clouqueur, W. Grover, Mesh-restorable networks with 74 enhanced dual-failure restorability properties, in: Proc. SPIE OPTICOMM, Boston, MA, 2002, pp. 1–12]. Thus, the motivation for this work is to develop a hybrid mechanism that provides maximum (close to 100%) dual-failure restorability with minimum additional spare capacity. The system architecture considered is circuit-switched with dynamic arrival of sessions requests. We propose an adaptive mechanism, which we term active protection, that builds upon a proactive path protection model (that provides complete single-failure restorability), and adds dynamic segment-based restoration to combat dual-link failures. The objective is to optimize network survivability to dual-link failures while minimizing additional spare capacity needs. We also propose a heuristic constraint-based routing algorithm, which we term best-fit, that aids backup multiplexing among additional spare paths towards this goal. Our findings indicate that the proposed active protection scheme achieves close to complete (100%) dual-failure restorability with only a maximum of 3% wavelength-links needing two backups, even at high loads. Moreover, at moderate to high loads, our scheme attains close to 16% improvement over the base model that provides complete single-failure restorability. Also, the best-fit routing algorithm is found to significantly assist backup multiplexing, with around 15%–20% improvement over first-fit at all loads. The segment-based restoration algorithm reiterates the importance of utilizing wavelength converters in protection and is seen to provide around 15%–20% improvement over link restoration especially at moderate to high loads. [Copyright &y& Elsevier]