Simple Scheduling Algorithms for Use with a Waveguide Grating Multiplexer Based Local Optical Network

Single-hop wavelength-division-multiplexing (WDM) networks based on a central passive star coupler (PSC) or arrayed-waveguide grating (AWG) hub have received a great deal of attention as promising solutions for the quickly increasing traffic in metropolitan and local area networks. These single-hop networks suffer from a single point of failure: if the central hub fails, then all network connectivity is lost. To address this single point of failure in an efficient manner, we propose a novel single-hop WDM network, the AWG/spl par/PSC network. The AWG/spl par/PSC network consists of an AWG in parallel with a PSC. The AWG and PSC provide heterogeneous protection for each other; the AWG/spl par/PSC network remains functional when either the AWG or the PSC fails. If both AWG and PSC are functional, the AWG/spl par/PSC network uniquely combines the respective strengths of the two devices. By means of analysis and verifying simulations we find that the throughput of the AWG/spl par/PSC network is significantly larger than the total throughput obtained by combining the throughput of a stand-alone AWG network with the throughput of a stand-alone PSC network. We also find that the AWG/spl par/PSC network gives over a wide operating range a better throughput-delay performance than a network consisting of either two load sharing PSCs in parallel or two load sharing AWGs in parallel.

The authors propose a star topology for multihop lightwave networks in which the conventional N*N passive star coupler is replaced by fixed wavelength division multiplexing (WDM) cross-connects. The proposed topology overcomes three major limitations of the conventional star topology. First, it reduces the number of wavelengths needed in a (p,k) ShuffleNet from kp/sup k+1/ wavelengths in the conventional topology to p wavelengths in the proposed one. Second, the signal power loss due to the 1/N power splitting at the star coupler no longer exists in the WDM cross-connects and, therefore, the restriction on the supported number of users by the star network is alleviated. Third, it completely eliminates the need for wavelength filtering at the input to the receivers, as is the case in the conventional star topology. The use of 2*2 WDM lapped couplers as a cheap WDM cross-connect for a (2,k) ShuffleNet is investigated. A p*p star coupler followed by p fiber Fabry-Perot filters can be used as a p*p WDM cross-connect for a (p,k) ShuffleNet at the expense of using p/sup 2/ rather than p wavelengths. >

A network with N stations connected via a passive star coupler using wavelength division multiplexing (WDM) is considered. Each station is equipped with a transmitter, transmitting at a fixed frequency, and a tunable receiver, capable of receiving frequencies over the entire transmitting spectrum. Two reservation-based protocols are proposed for a local area network (LAN) environment: the dynamic allocation scheme (DAS), which dynamically assigns slots on a packet-by-packet basis, and the hybrid TDM scheme (HTDM) which is a combination of TDM and the DAS, allowing both preassigned slot and dynamic slot assignment. Analytical results are derived for the delay performance of the two schemes and these results are compared with that of the TDM. It is shown that the performance of DAS is close to optimal when the propagation delay is zero. However, it requires a large signaling bandwidth. On the other hand, HTDM has lower signaling needs, provides lower delays when compared to TDM (particularly under nonuniform traffic conditions), and is capable of handling bursty data traffic. Thus, HTDM offers a more practical solution for implementation for LANs. >

With the proliferation of the world-wide-web (WWW), current local and wide area networks can hardly cope with the huge demand for network bandwidth. As a result, there is a world-wide effort in upgrading current networks with high-capacity fiber-optic links that can potentially deliver Tera-bits/sec bandwidth. The Wavelength-Division-Multiplexing (WDM) is an effective technique for utilizing the large bandwidth of an optical fiber. By allowing multiple simultaneous transmission over a number of channels, WDM has the potential to significantly improve the performance of optical networks. The nodes in the network can transmit and receive messages on any of the available channels by employing one or more tunable transmitter(s) and/or tunable receiver(s). Several topologies have been proposed for WDM networks. Of particular interest to us in this chapter is the single-hop topology where a WDM optical network is configured as a broadcast-and-select network in which all the input nodes are combined using a passive star coupler, and the mixed optical information is broadcast to all destinations. To unleash the potential of single-hop WDM passive star networks, effective medium access control (MAC) protocols are needed to efficiently allocate and coordinate the system resources. In this chapter, we present a comprehensive survey of state-the-art MAC protocols for WDM networks so as to give the reader an overview of the research efforts conducted in this area for the past decade. In addition, it can serve as a starting point for further investigation into ways of coping with the current and the anticipated explosion of multimedia information transfer.

A novel wavelength division multiplexers is designed and demonstrated to achieve doubled channel number and halved channel spacing for an arrayed-waveguide grating by utilizing an optical interleaver integrated.

Wavelength Division Multiplexing (WDM) has been widely used for studying the performance of optical networks, especially those employing optical passive star couplers. Many models have been proposed for WDM on an optical passive star coupler, such as each station equipped with a single tunable transmitter and a single fixed wavelength receiver, and each station with multiple tunable transmitters and multiple tunable receivers. The current technology only allows the transceivers to be tunable in a small range, a fact ignored in previous studies. In this paper, we focus on the design of WDM optical passive star networks with tunable transmitters of limited tuning range and fixed wavelength receivers. The limited tuning range has effects on the maximum delay, the total number of wavelengths which can be used, and the topological embedding. Complete graphs, meshes, and hypercubes are the three topologies studied in this paper. The relationship between the total number of wavelengths which can be utilized and the embedded topology is established. The bound for the maximum delay is analyzed. The optimal embedding algorithms are given for the systems embedded with one of the three topologies.

A new network architecture, called MultiS-Net, is proposed to provide packet-switched services to a large number of bursty users connected to a multichannel broadcast medium in a local environment. An example physical network would consist of a passive star coupler to which nodes are connected via two-way fibers, and wavelength division multiplexing (WDM) is used to create multiple, parallel optical channels. A separate channel, called a control channel, is established to coordinate data packet transmissions on the other channels (called data channels). To allow low network interfacing costs, each node in MultiS-Net is only equipped with a single tunable transmitter and a single tunable receiver, both of which are responsible for data channel access as well as control channel access, and both of which are rapidly tunable. MultiS-Net incorporates a simple medium access mechanism, and it can also achieve high system throughput. In addition, MultiS-Net is scalable, i.e. it can accommodate a variable number of nodes as well as time-varying load. >

Future LANs and MANs may be based upon multichannel, single-hop network architectures constructed using wavelength-division-multiplexing (WDM) and passive star couplers. Due to device limitations, the number of available channels may be smaller than desired. In this case, wavelength spatial re-use will be required to support an acceptable number of stations and performance. Recently, hierarchical wavelength re-use architectures have been proposed for this purpose [1].

Multicasting plays an important role in internet networks. Supporting wavelength division multiplexed (WDM) multicasting in an IP over WDM network poses interesting problems because some WDM switches may be incapable of switching an incoming signal to more than one output interface. Although some multicast applications, such as audio/video conferencing can tolerate packet error or loss, other applications such as one-to-many file transfer and military applications do not. Hence, an inevitable need for reliable multicasting arises. The reliable multicast protocol ensures the eventual delivery of multicast data to all multicast group members. The reliable multicast is receiver initiated NACK-based and it makes use of feedback suppression in order to avoid NACK and retransmission implosion. The loss recovery burden is distributed over the multicast group members in order to reduce recovery latency and end-to-end delay. The proposed protocol is evaluated in terms of performance metrics for an IP/WDM optical network which will be the candidate for the next generation internet networks.

In this paper, we propose and implement a novel bidirectional wavelength add-drop multiplexer (B-WADM) to provide dynamic wavelength allocation employing tunable fiber Bragg gratings (FBGs) and self-protecting function under link failure. This device can be used to improve the efficient use of wavelengths under burst traffic load as well as increase network reliability. The experimental results demonstrate that this B-WADM device can provide robust, flexible and cost-effective characteristics in the wavelength division multiplexing (WDM) fiber-radio ring access network.

PHASARs or Arrayed Waveguide Grating (AWG) multiplexers for application in Dense Wavelength Division Multiplexing optical networks have been realized using silica-waveguide technology. Using waveguide tapers, a flat-top passband characteristic is obtained. Using Fourier transform spectroscopy employing a low coherence interferometer, the power-distribution coefficients and the phase error distribution in such components is evaluated. Because of the coherence length of the used light source being smaller than the optical path length difference in the PHASAR, it is possible to resolve individual waveguides of the array. Thus, the transfer functions of the individual optical paths are accessible to the measurement, enabling the full simulation of the PHASAR transmission spectrum. It is demonstrated that the measured phase error distribution in tapered PHASAR devices consists of contributions from both tapered waveguides and arrayed waveguide grating regions. An evaluation method suitable for investigating both contributions separately is developed. Phase shift introduced by the waveguide tapers is in good agreement with simulation calculations based on the Beam Propagation Method. An analytic transmission calculation based on measured phase and power-distribution coefficients enables a full simulation of PHASARs including insertion loss, bandwidth and crosstalk performance. Excellent agreement with transmission measurements is performed.

A collision-avoidance WDM optical star network

In this PhD dissertation multi-rate models are examined for the performance analysis of telecommunication networks through mathematical analysis and simulation. Particular emphasis is given to optical networks. The main goal is the development of analytical models for the calculation of network performance metrics, such as blocking probabilities, transmission delay and utilization of the common channel. The proposed analytical models are distinguished according to the network technologies. Three different technologies are considered: A) Wavelength routed optical networks. B) Optical access networks. C) Wireless Internet access networks. Multi-rate loss models are proposed for the performance evaluation of wavelength routed optical networks. Firstly, the case of a single link is considered and then a mesh all-optical network is examined. In addition, analytical models are proposed for Optical Packet Switching (OPS) networks, for the case of an all-optical OPS switch and of an OPS mesh network. Multi-rate analytical models are proposed for the evaluation of the performance of Passive Optical Networks (PONs) implementing different multiple access methods. For the case of Time Division Multiple Access (TDMA) the Ethernet PON is studied, which supports multiple service-classes. Regarding the Wavelength Division Multiplexing (WDM) PONs a hybrid WDM-TDMA PON is considered and the call-level performance is evaluated. Calls are distinguished by their arrival process, which can be random or quasi random, by their bandwidth requirements, which can be fixed of elastic and by their behavior during their service, which can be calls of fixed transmission rate or calls that alternate between ON and OFF periods. Finally multi-rate loss models are proposed for the case of Optical Code Division Multiple Access (OCDMA) PONs that take into account the user activity and the presence of additive noise in the transmission channel. For the performance analysis of wireless Internet access networks analytical models are proposed, which implement the IEEE 802.11 protocol or the IEEE 802.11e protocol. The proposed analysis calculated the saturation throughput and the end-to-end packet delay as a function of the Medium Access Control (MAC) delay and the queueing delay. In all cases the accuracy of the proposed models is validated through simulation.

The scalability of quantum communication networks requires compact, fiber-integrated, easy-to-deploy, and efficient wavelength-division-multiplexed (WDM) sources for multi-user secure key distribution. Here, we demonstrate such a multi-channel source of polarization-entangled photon pairs in the low-loss telecom C-band based on type-0 spontaneous parametric downconversion in a fiber-coupled Zn-indiffused MgO-doped periodically poled lithium-niobate (MgO:PPLN) ridge waveguide in the Sagnac configuration. The source can be easily tuned to generate the |Φ+⟩ or |Φ−⟩ Bell state in 14 channel pairs of the International Telecommunication Union dense WDM (100-GHz spacing) grid around 1550-nm with a raw fidelity of ≳89%, with a maximum value of ≳94%. The raw concurrence is ≳0.8 for both Bell states in all channel pairs, and the observed S-parameter (>2.56 ± 0.04 in all 14-channel pairs) shows a strong violation of CHSH-Bell’s inequality. The source’s suitability for long-distance entanglement transmission is also demonstrated by the successful transfer of entangled photons up to 100 km while maintaining fidelity >85% and quantum bit error rate <9%. The effect of polarization mode dispersion on entanglement distribution among remote users is also studied in detail. All these performance metrics are measured using conventional room-temperature semiconductor-based single-photon avalanche detectors, and these are the best reported with these detectors. Our highly flexible source can support up to ∼40 user pairs to communicate simultaneously, and it can be easily deployed into the current metro-area fiber-optic telecom infrastructure to form a complete WDM-based quantum communication network.

For future wavelength-division-multiplexed (WDM) networks, optical frequency conversion will enable the flexible and efficient use of optical frequency bandwidth. However, the signal degradation at frequency converters limits the maximum size of the network. Noise due to optical frequency conversion using nearly degenerate four wave mixing in a semiconductor optical amplifier is investigated, and it is found that the crosstalk from one of the two pump lasers can impose the power penalty on the bit error rate (BER) characteristics after optical frequency conversion. Analytical expressions for BER are developed and used to evaluate the receiver sensitivity penalty caused by optical frequency conversion. On the basis of these results the optimal setting of the frequency difference between the signal and pump lasers and the power ratio of the two pump lasers are discussed. A 155-Mb/s frequency-shift keying (FSK) transmission with 1750-GHz (14 nm) optical frequency conversion has been carried out, using a novel phase noise cancellation method. The BER performance is in good agreement with the calculated results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>