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In this paper, slow light features of an engineered photonic crystal waveguide are presented. The combined effect of lattice shift, lattice twist and introduction of ring-like holes (rings) in the innermost rows on the slow light features is studied. The rings are introduced in the first and second innermost rows of the waveguide. Slow light is characterized by calculating group index, second and fourth-order dispersions, and delay-bandwidth products. MIT Photonic Bands software is used for simulation. With rings in the innermost rows, a flat band of 17.71 nm is observed with a group index value of 12.72 and a flat band of 40.16 nm with a group index of 7.77. The normalized delay bandwidth product (NDBP) is observed as 0.1378 in the first structure and 0.1874 in the second structure with the proposed effects. These values are nearly 4.3 times higher in comparison with the NDBP value of the base structure (0.0436) and approximately 2 times higher than the engineered structure (0.0927). These structures are useful in slow light applications. [ABSTRACT FROM AUTHOR]

Optical buffer is a key technology to control optical routing and solve channel competition, which directly determines the performance of information processing and storage. In this study, a switchable optical buffer using the nonreciprocal silicon-on-insulator (SOI) magneto-optical micro-ring (MOMR) array coupled with Sagnac ring was introduced, which can exceed the time-bandwidth limitation. The transmission equations and propagation characteristics of optical signal in 1 × 3 micro-rings and Sagnac ring coupled 1 × 3 micro-rings based on two kinds of phase-change materials were studied. The group time delay, effective buffer time and readout operation in the buffer were also investigated. [ABSTRACT FROM AUTHOR]

Phase-change materials (PCMs) have become as promising elements in silicon photonic systems. We propose an optical buffer device based on vanadium dioxide (VO2) embedded on silicon-on-insulator waveguides with a microring resonator. The upload straight waveguide is for coupling light signal from the input port into VO2 embedded on microring resonator and the download straight waveguide with VO2 films is for coupling the storage signal to the output port. The optical characteristics of optical buffer device under different structural parameters are analyzed by using finite difference mode simulation (MODE). By controlling the phase state of VO2 in two coupling regions, the buffer speed of the device can be up to 0.5 ps and buffer time up to 78.28 ps. The optical buffer based on VO2 is a new way for PCM optical buffer.

Dispersion engineering of photonic crystal waveguides is attractive due to their potential applications in linear and nonlinear phenomena. Here, we present a comprehensive and systematic study to achieve the increased control over the dispersion curve of the waveguide, operating at telecom wavelengths. The effect of the radius of air cylinders, and their lattice position on the dispersion features is studied chiefly in a line-defect photonic crystal waveguide. For this purpose, perturbations were introduced in the radius and position of the air cylinders. With the help of MIT Photonic Bands software, group index and dispersion coefficients were calculated to characterize the features of the waveguide. Ring like structures were introduced in the innermost rows to increase the impact to further level. With this systematic study, one can tune the waveguide with desired range of group index and bandwidth with controlled dispersion properties. Present study resulted with a constant group index in the range of 31.42 to 7.64 over a bandwidth of 7.97 nm to 30.41 nm with very low dispersion. The developed structures may find applications in optical delays, optical buffers and nonlinear applications. [ABSTRACT FROM AUTHOR]

Optical buffer is a key technology to control optical routing and solve channel competition, which directly determines the performance of information processing and storage. In this study, a switchable optical buffer using the nonreciprocal silicon-on-insulator (SOI) magneto-optical micro-ring (MOMR) array coupled with Sagnac ring was introduced, which can exceed the time-bandwidth limitation. The transmission equations and propagation characteristics of optical signal in 1 × 3 micro-rings and Sagnac ring coupled 1 × 3 micro-rings based on two kinds of phase-change materials were studied. The group time delay, effective buffer time and readout operation in the buffer were also investigated.

Phase-change materials (PCMs) have become as promising elements in silicon photonic systems. We propose an optical buffer device based on vanadium dioxide (VO2) embedded on silicon-on-insulator waveguides with a microring resonator. The upload straight waveguide is for coupling light signal from the input port into VO2 embedded on microring resonator and the download straight waveguide with VO2 films is for coupling the storage signal to the output port. The optical characteristics of optical buffer device under different structural parameters are analyzed by using finite difference mode simulation (MODE). By controlling the phase state of VO2 in two coupling regions, the buffer speed of the device can be up to 0.5 ps and buffer time up to 78.28 ps. The optical buffer based on VO2 is a new way for PCM optical buffer. [ABSTRACT FROM AUTHOR]

A tunable optical buffer composed of a side-coupled racetrack microring resonator (RMRR) sequence and phase change material vanadium dioxide (VO2) films has been designed and simulated with pass-through and drop functions. By optically induced phase transition of VO2, the number of coupled RMRRs is dynamically controlled to realize the required delay time and the ultra-fast response. Simulation results show that the buffer with 12 RMRRs achieves a tunable delay of up to 309.6 ps, a working bandwidth of 306 GHz, and a super-fast response of 0.62 ps. The delay loss and power consumption are 0.012 dB / ps and 0.194 mW / ps, respectively. These findings suggest a new approach to realizing tunable delay in all-optical networks. [ABSTRACT FROM AUTHOR]

Temporal cavity solitons (CSs) have been proposed to store the information in the form of optical bits in a single-pump Kerr micro-resonator. However, such optical buffers (OBs) realized using a single-pump are essentially asynchronous in nature. In this paper, we show that dual-pump scheme can lead to both synchronous and robust OB. Numerical simulations reveal the resilience in the performance of the OB against the writing jitters and third-order dispersion induced temporal drift. The impact of nonideal operating conditions, such as unequal pump amplitudes and pump detuning mismatch on the performance of the synchronous OB, are evaluated and the robustness of the OB with respect to these aspects are explored both analytically and numerically. As an interesting application of the proposed dual-pump scheme, we have demonstrated the capability to perform simultaneous logic operations (AND, OR) of the proposed device. All the conclusions are supported by analytical and semi-analytical approaches. [ABSTRACT FROM AUTHOR]

One of the main problems in all-optical packet switched networks is the buffering of packets. A popular solution for buffering packets is to use a set of fiber delay lines attached to a switch. A priority queue is one of the most general buffering schemes that allows the packet with the highest priority to depart the buffer on a departure request and dropping of the lowest priority packet if a new packet arrives when the buffer is full. We present a recursive algorithm for constructing optical priority queues of polynomial size from a switch with linear number of inputs/outputs and fiber delay lines. The best known lower bound allows the construction of a priority queue of size 2^M using a switch of size M . However, the best known upper bound constructs a priority queue of size M^{3} using a switch of size M . We show that it is possible to construct a priority queue of size O(M^c) for a fixed constant c using a switch of size $O(M)$ . [ABSTRACT FROM AUTHOR]

In optical packet/burst switching, fibre-loop optical buffers provide a compact and effective means of contention resolution. In case of fixed packet length, the involved loop length is typically chosen matched (equal to the packet length), and the loops are arranged in parallel, constituting a single-stage buffer. In this contribution, we investigate the performance of such a buffer in an asynchronous network setting, assuming batch-Poisson arrivals and assuming a so-called void-avoiding schedule. We show that by time-discretisation, the fibre-loop dynamics can be captured by a particular type of exhaustive polling model. We obtain performance measures such as the moments of the optical queue content and packet delay for the discretised model as well as for the asynchronous optical buffer. We illustrate our approach by various numerical examples.

Microring resonator optical buffer is attractive in high-speed optical network system, but ordinary microring resonator use strip waveguide as its basic light guide medium, which cannot provide small footprint, low dispersion and high delay-bandwidth product (DBP) simultaneously. Double-slot waveguide structure was first proposed to construct racetrack-microring resonators. It was found that cascading multiple microrings can increase the delay-bandwidth and lower the dispersion of the resonators by optimizing the structure parameters. Optical buffer cascaded by 8 microrings with flat bandwidth of 20 GHz provided the delay of 150 ps and the dispersion of ~10 ps/nm over 1530-1630 nm, and the footprint of each microring was about 51μm. This study can provide design methods and theoretical basis support for practical application. [ABSTRACT FROM AUTHOR]

In the optical packet switching network, optical buffer is an important device. Microring resonator optical buffers provide good delay performance and flexibility in design. By cascading multiple microring resonators, higher delay-bandwidth product is obtained, but the requirements of high integration and low dispersion are hard to satisfy simultaneously. Double-slot waveguide was proposed to construct highly integrated racetrack microring resonators in this study. Based on dispersion analysis of the thickness of each layer of a waveguide, the structure of waveguide was optimized to reach flat and low dispersion. Average dispersions of straight and 3 μm bend waveguides were 5.1 ps/(nm∙km) and 4.4 ps/(nm∙km), respectively. Besides, the additional loss from coupling was greatly reduced when applying proper relative displacement between straight and bend waveguides. Theoretical and design basis provided in this paper will help to develop multi-microring optical buffers in the future. [ABSTRACT FROM AUTHOR]

We consider optical delay line buffer as a solution to reduce the number of lost burst in optical burst switching, one of the promising candidates for future networks. Such network takes burst loss as an important performance criteria in the design step. Network performance, however, cannot be captured efficiently using traditional queueing models, because they often ignore the impatience of messages traveling through optical switches which is one of the popular issues in communication networks. In this paper, we develop an analytic model for this system using queueing theory and considering special impatience features. Simulation results show that (i) the developed model with impatience features can decrease burst loss probability ( ≃ 10 %) compared with other approaches, and (ii) applying that model, we demonstrate that shared buffer architecture in optical burst switching network with optical buffer often achieves lower burst loss probability than dedicated buffer way in several different scenarios. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This letter proposes a new type of photonic crystal waveguide (PCW) called oval-shaped-hole PCW (OPCW). In the proposed structure, the circle-shaped holes are replaced by oval-shaped holes. In order to find the best possible structural parameters, the recently proposed multiobjective framework called MoMIR is employed. The calculation results show that the proposed optimized OPCWs are able to outperform the best current PCW in the literature significantly. [ABSTRACT FROM PUBLISHER]

An optical packet and circuit integrated network (OPCInet) provides both high-speed, inexpensive services and deterministic-delay, low-data-loss services according to the users' usage scenarios, from the viewpoint of end users. From the viewpoint of network service providers, this network provides large switching capacity with low energy consumption, high flexibility, and efficient resource utilization with a simple control mechanism. This paper presents the recent progress made in the development of OPCInet and its extension to software-defined networking (SDN). We have developed OPCI nodes, which are capable of layer 3 switching from/to an Ethernet frame to/from an optical packet in the optical packet edge part and a burst-tolerant optical amplifier and an optical buffer with optical fiber delays in 100 Gbps optical packet switching part. The OPCI node achieves a packet error rate less than 10-4 and is used as a node in a lab-network that has access to the Internet. A distributed automatic control works in a control plane for the circuit switching part and in a moving boundary control between optical packet resources and circuit resources. Our optical system for packet and circuit switching works with a centralized control mechanism as well as a distributed control mechanism. We have shown a packet-based SDN system that configures mapping between IP addresses and OPCI node identifiers and switching tables according to the requests from multiple service providers via a web interface. [ABSTRACT FROM PUBLISHER]

Optical interconnects are considered as a very appealing solution for future high speed interconnections in core networks and parallel computers. In this paper, we study multicast scheduling in all-optical packet interconnects/switches. We first propose a novel optical buffer called multicast-enabled fiber-delay-lines (M-FDLs), which can provide flexible delay for copies of multicast packets using only a small number of FDL segments. We then present a Low Latency Multicast Scheduling (LLMS) Algorithm that considers the schedule of each arriving packet for multiple time slots. We show that LLMS has several desirable features, such as a guaranteed delay upper bound and adaptivity to transmission requirements. To relax the time constraint of LLMS, we further propose a pipeline and parallel architecture for LLMS that distributes the scheduling task to multiple pipelined processing stages, with N processing modules in each stage, where N is the size of the interconnect. Finally, by implementing it with simple combination circuits, we show that each processing module can complete the packet scheduling for a time slot in O(1) time. The performance of LLMS is evaluated extensively against statistical traffic models and real Internet traffic traces, and the results show that the proposed LLMS algorithm can achieve superior performance in terms of average packet delay and packet drop ratio. [ABSTRACT FROM PUBLISHER]

This letter proposes a novel framework for designing photonic crystal waveguides (PCWs), in which three components optimize and analyze the structure of PCWs. The proposed components are a multi-objective formulator, a multi-objective optimizer, and a multi-objective analyzer. A ring-shaped hole PCW is chosen as the case study, but the proposed framework is applicable to designing any kind of PCW. The results show that the proposed framework is able to find a significantly wider range of optimized designs and reveals the physical behavior of PCW structure. [ABSTRACT FROM PUBLISHER]

Currently, optical cross-connects working on wavelength division multiplexing systems are based on optical fiber delay lines buffering. We designed and analyzed a novel photonic crystal optical memory, which replaces the fiber delay lines of the current optical cross-connect buffer. Optical buffering systems based on random photonic crystal optical memory have similar behavior to the electronic buffering systems based on electronic RAM memory. In this paper, we show that OXCs working with optical buffering based on random photonic crystal optical memories provides better performance than the current optical cross-connects. [ABSTRACT FROM AUTHOR]

Abstract: Programmable variable delay lines have been developed, so as to delay packets in variable durations by combining several lengths of Fiber Delay Lines (FDLs) in optical packet switch. In practice, Two-stage variable optical packet switch with this programmable variable delay lines has been proposed. This switch has two buffers. The one is the programmable variable delay lines (Look-ahead Buffer). The other is the fixed FDLs that re-input a packet from the output to the input (Loop-back Buffer). The switch can foresee following packets and avoid contentions effectively by using two buffers. However, existing studies only focus on the Look-ahead Buffer. Intelligent usage of the Loop-back Buffer is actually out of concern. This paper proposes a sophisticated scheduling method in the Two-stage switch. The proposed method controls both the Look-ahead Buffer and the Loop-back Buffer cooperatively and improves the utilization of the switching process. The proposed method uses the Loop-back Buffer adaptively and distributes traffics in time and space domain. The effectiveness of the proposed method is evaluated through extended simulation experiments and basic hardware design. [Copyright &y& Elsevier]

We propose a novel design of optical buffer to generate slow light based on delay time. In the framework of the nonlinear waveguide, we investigate propagation of solitons through microring resonators. Dynamical control over slow-light solitons is realized via controlling fields generated by bright soliton and Gaussian pulse. The nonlinear dependence of the velocity of the signal on the controlling field is analytically described. The buffering effect is achieved by slowing the optical signal using an external control light source to vary the dispersion characteristic of the medium via microring resonators. A graphical approach with a signal flow graph method is used to derive the optical transfer functions in z-domain of filters. The characteristics of the optical buffer devices including the transmittance and time delay of the through and drop port are simulated. Simulated results show the criteria of achieving slow light in semiconductor microring resonators. Finally, output signal shows the delay time rate by propagation through the semiconductor microring resonators. [ABSTRACT FROM AUTHOR]

Abstract: Burst-outputted performance will be affected by the outputting scheme in optical burst switching (OBS) core nodes. In this paper, we have evaluated the performance of an improved burst-outputted scheme in an OBS core node, in which fiber delay lines (FDLs) based limited optical buffer has been equipped. Different from the previous works which only consider the same probability to select output-port for burst, the proposed scheme gives a burst-outputted process based on different port selected probability. Simulation results have indicated that, performance evaluation parameters are changed with the output-port selected probability and the different number of FDLs in an optical buffer. [Copyright &y& Elsevier]

An all-optical network still remains a long way from realistic deployment. However, all-optical packet switches, in which optical packets are buffered and routed in optical form, are still expected to solve the problems of electronic bottlenecks and large power consumption in electronic routers. An approximation is presented for blocking probabilities and delays of optical buffers, where optical packet arrival process is Poisson and packet-length distribution is general. The approximation aims at providing a simple calculation tool for optical buffer design without requiring computer simulations or extensive iterative computations. An approximation for the cumulative distribution function of the waiting time for general packet-length distributions was obtained that holds when the waiting time is sufficiently large and the traffic load is heavy. The difference in the blocking probabilities between the approximation and the simulation results was found to be less than 10% when the offered load was greater than 0.7. The approximation can be applied to investigate multiclass optical buffers for priority queueing and to design wavelength-division-multiplexing optical packet switches and networks with the maximum throughput. [ABSTRACT FROM PUBLISHER]