2×2 photonic node for all-optical packet switching networks

This paper presents PLATO, an analytical technique to model the performance in all-optical packet-switched networks with various topologies and node architectures. Using this technique, we propose a two-part algorithm, incorporating mathematical analysis and a numeric method, to model the network's traffic flow and the local packet-loss probability inside each node. The PLATO technique has demonstrated excellent accuracy with two different representative network topologies and node architectures. It has considerably reduced the time required to evaluate the performance of all-optical packet-switched networks.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We propose and demonstrate a novel ultrafast label processor that can recognize multiple spectral amplitude coded (SAC) labels using four wave mixing (FWM) sideband allocation and selective optical filtering. Our proposed solution favors hardware simplicity over bandwidth efficiency in order to achieve ultrafast label recognition at reasonable cost. Our implementation, unlike all other optical label processing techniques, does not require time gating, envelope detectors, or serial-to-parallel converters. Labels are transmitted simultaneously with the payload, improving temporal efficiency at the expense of spectral efficiency. Note that bandwidth efficiency can be improved through a frequency management scheme that uses irregular spacing of wavelengths for payload and label, a complexity overhead in management similar to that in long-haul networks employing irregular spacing of carriers to avoid FWM products. We present two experiments of the single processor for ultrafast forwarding using first optoelectronic and then all-optical switches. In the first experiment, we use 10 SAC labels with minimum bin separation of 25 GHz, 10 Gb/s variable-length data packets, and forward packets over 200 km using electrooptical switches. In the second experiment, all-optical switching at 40 Gb/s is demonstrated using a SAC family for up to 36 labels. We present details on the families of spectral codes for label recognition, using unequally spaced frequency bins. A code family with weight 2 and length 9 uniquely identifies 36 labels. Hardware complexity is moderate compared with short-pulse code labels (mode-locked laser) techniques. Two stable tunable lasers are required for label generation of this code family; all other hardware is commercial, off-the-shelf components such as semiconductor optical amplifiers, array waveguide gratings, optoelectronic switches, and photodetectors. </para>

Multi-wavelength optical buffer will be a key element in Wavelength Division Multiplexing (WDM) system and all-optical packet-switched networks. In this paper we have presented and demonstrated the dual-wavelength signal buffering in Dual-Loop Optical Buffer (DLOB) based on Semiconductor Optical Amplifier (SOA). The dual-wavelength packets are written in and read out of DLOB by single control signal. As the power of the control signal increasing, the output of the signals is better. In simulation confirmed by experiments, we obtained suitable control power, where the gain and phase-shift difference between "1" bit and "1+1" bit is minimum. More than 12 cycles' buffering results have been obtained and the power loss is lower than 4db.

This paper presents a comparative study of contention-resolution schemes based on wavelength, time, and space domains in an unslotted optical packet-switched network with a large irregular mesh topology consisted of 15 nodes. For the first time, to the best of our knowledge, we investigated the effect of selective deflection and limited wavelength conversion. Features and performances of different combinational schemes are listed and compared. While simulation results show the effectiveness of wavelength conversion for resolving contentions over optical buffering and space deflection, physical explanations of the different effectiveness in resolving contentions of these schemes are also discussed.

We propose and experimentally demonstrate the concurrent generation of an optical code label and payload data by use of off-the-shelf optical intensity and phase modulators in a tandem structure. This technique is capable of reconfigurable generation of an arbitrarily long optical code label of phase-shift keying concurrently with the generation of payload data, without the need for a special class of optical encoder. This technique will be powerful for all-optical packet switching networks, based on scalability and compactness, for optical code labels.

With emerging trends for ubiquitous data services, the IP-optical convergence networks are gradually becoming a preferred technology. In optical transport networks (OTNs), a major obstacle in realizing all-optical switched IP network is due to the large processing delays of optical switching nodes that still need OEO conversion at the optical header (label) processing. The proposed labeling scheme requires neither table lookup nor label replacing in the stateless all-optical switching node, labeled packets/bursts will be forwarded through self-routing, and the only operation in optical switching nodes is to strip off its label part which represents the output port. Thus, the whole processing has been completed in the optical domain. The purposes of this paper are to shed light on a very active field of research on next generation all-IP photonics telecommunication and Internet, as well as to contribute on everyone’s modern style of living.

The performance of an optical burst switching network is determined by the comprehensive effect of various parameters. This paper presents analysis results of an all-optical burst switching network which consists of edge nodes, which are responsible for traffic aggregation and distribution, and core nodes, which transmit payload data burst in the optical domain. Some essential parameters are compared on their effects on implementing switching operation, contention resolution and routing functions. We have examined the interrelationship of these parameters. Typical performance criteria are investigated in a sample OBS network.

The so-called media convergence to the Internet is foreseen. As a consequence of this convergence, MANs will face new demands not only in terms of bandwidth, but also in terms of services. To meet these new demands, new MAN architectures are required. WDM-based MAN architectures that tackle the first problem are available not only in the literature, but also on the market. In this paper we deal with the second problem. Specifically, we describe a novel WDM-based MAN architecture that supports group communication, a service that is expected to increase considerably as new applications converge to the Internet. Based on packet switching, the architecture supports both point-to-point and point-to-multipoint communication in the optical domain.

Single femtosecond optical laser pulses, of sufficient intensity, are demonstrated to reverse magnetization in a process known as all-optical switching. Gold two-wire antennas are placed on the all-optical switching film TbFeCo. These structures are resonant with the optical field, and they create a field enhancement in the near-field which confines the area where optical switching can occur. The magnetic switching that occurs around and below the antenna is imaged using resonant X-ray holography and magnetic circular dichroism. The results not only show the feasibility of controllable switching with antenna assistance but also demonstrate the highly inhomogeneous nature of the switching process, which is attributed to the process depending on the material's heterogeneity.

Random access memories (RAM) are fundamental in conventional electronic switches and routers to manage short-term congestion and to decrease data loss probabilities. Switches in all-optical networks (AONs), however, do not have access to optical RAM, and therefore are prone to much higher loss levels than their electronic counterparts. Fiber-delay-lines (FDLs), able to delay an optical data packet a fixed amount of time, have been proposed in the literature as a means to alleviate those high loss levels. However, they are extremely bulky to manage, so their usage introduces a trade-off between practicality and performance in the design and operation of the AON. In this paper we study the influence that FDLs have in the performance of flows crossing an all-optical switch that acts as their bottleneck. We show how extremely low numbers of FDLs (e.g., 1 or 2) can help in reducing losses by several orders of magnitude in several illustrative scenarios with high aggregation levels. Our results therefore suggest that FDLs can be a practical means of dealing with congestion in AONs in the absence of optical RAM buffers or of suitable data interchange protocols specifically designed for AONs.

Resource contention in packet switched all-optical networks is being addressed in this paper through the combined use of fiber delay lines and 2/spl times/2 space photonic switches. With this basic approach, also known as Quadro or switched fiber delay lines (SDL), the solution efficiency is linked to its storage capacity, determined by the combined length of the fiber delay lines. In the past, this capacity was given by the number of 2/spl times/2 photonic switches used, i.e., the number of stages in the receiver, which limited the solution by cost, mainly determined by the switch component, and by the signal power loss and crosstalk introduced by each switch. This work presents and analyzes the use of multibuffer fiber delay lines, in Quadro, so termed since in it multiple packets are allowed to be concurrently stored (propagated) on each delay line. In this way the total storage capacity is increased, while the proposed design utilizing novel switch control is shown to significantly improve receiver and network performance, without increasing the number of the 6/spl times/2 space photonic switches in the system, i.e., its cost.

This paper investigates the implementing techniques concerning 2-to-1 node receiver for all-optical packet switching. We point out that the state-of-the-art technologies introduced in the literatures are all associated with one main limitation, i.e., even if two incoming packets are directed to the different ports and thus no contention will occur, they can not be directed to the output ports simultaneously. To overcome this problem, a novel node receiver model is proposed in this paper. This work presents a solution that makes use of fiber delay-lines (FDLs) which allow multiple packets to be concurrently stored or transmitted. With a novel switch control, it is shown that this solution is very efficient to resolve contention, and overcomes the limitation existing in the current models (e.g., Quadro, M-Quadro and COD architectures). We describe and analyze the concrete scheduling of the switches. Simulation results based on bursty and non-bursty traffic scenarios demonstrate that the proposed node architecture (1) performs well in terms of performance metrics such as packet loss probability; (2) has a simple control requirement. In addition, we find that the required number of the recirculating time of the packets is minimal.

All-optical packet switching can overcome limitations of electronic switches in terms of power consumption, speed, cost, and footprint. Switch architectures combining wavelength converters and fiber delay lines provide tunable routing and contention resolution when used with an N×N arrayed waveguide grating (AWG), a key passive optical component to bypass electronic processing limitations. An AWG passively routes either single or multiple input port wavelengths to output ports. A single wavelength per port strategy reduces crosstalk within the AWG, but drastically increases the dimensionality of the device. AWG design constraints due to bandwidth limitations and fabrication processes limit the port number for the foreseeable future to under 100. In order to scale optical switches to emerging network requirements, we must use multiple wavelengths per port. In this paper, we examine several optical router architectures for data center applications using multiple wavelengths per port, and quantify the physical layer impairments. We consider not only the AWG crosstalk, but also Q-factor degradation caused by the multiple wavelength conversions occurring when a packet is buffered for contention resolution. We present the results as a function of the number of recirculations for on–off-keying (OOK) signal formats. While previous work has addressed this issue in terms of accumulated loss, we focus on accumulated intensity noise due to crosstalk and amplified spontaneous emission (ASE). We compare the routing performance of each architecture, and we point out that the AWG crosstalk and accumulated ASE noise during packet recirculation are both critical to the routing performance.

The paper presents the 3D videoconference system requires the transport network such as high bandwidth, ultra-low latency and ultra-low jitter. For enabling the optical packet switches it focuses on optimised 2x2 EO switch to enable scalability and building a practical optical buffer enabling an OPS. This work also organized in 3 phases implementing each of the switching paradigms.

All-optical switches are expected to become one of key elements in future ultrafast and flexible all-optical communication networks. And it has been generally believed that such all-optical devices would require very fast, as well as very efficient, nonlinear optical material (or phenomena). In fact, the well-known and often discussed figure of merit for nonlinear materials [n2/(ατ), where n2 is the nonlinear refractive index change coefficient, α is the linear absorbance, and τ is the relaxation time] implies that it is the chosen nonlinear material that determines the basic device performance such as the switching speed and energy. In this paper, we show that this is not necessarily the case; the speed of a nonlinear optical switch proposed by the authors1,2 not restricted by the slow relaxation time of high efficiency incoherent nonlinearities.