Integrated-optics planar components

Optical fiber architectures of the future are envisioned to employ extensive splitting of optical signals, as well as multiple wavelength division multiplexing and demultiplexing. These architectures and networks have motivated the development and commercialization of today's planar passive components. Beyond and including these applications, the prospects for new and exciting uses of planar devices are excellent. Planar passive components already are providing such functions in what is known as fiber-in-the-loop (FITL) systems. These applications are discussed     

Design and cost performance of the multistage WDM-PON accessnetworks

The advantages of employing passive optical architectures in the access network have been largely recognized. Particularly, recent developments in optical technologies have made the realization of wavelength division multiplexing passive optical networks (WDM PONs) feasible and cost-effective. These networks are more future-proof than conventional PONs, thanks to their intrinsic optical transparency and their extremely high transmission capacity. A very useful optical routing device, called waveguide grating router, is the basic building-block of new PON architectures capable of connecting a large number of users or to improve the use of the optical bandwidth. In this paper, we analyze the connectivity of WDM PONs composed of multiple stages of WGR devices. A design tool is also presented which is able to easily evaluate the connectivity functions of complex WDM PONs. The feasibility of these architectures is discussed by considering the costs and the technological limitations on the optical components     

Ethernet-based passive optical local-area networks for fiber-to-the-desk application

We introduce optical local-area network (LAN) architectures based on multimode optical fiber and components, short wavelength lasers and detectors, and the widely used fast Ethernet protocol. These architectures are designed to lower the costs associated with passive optical LAN implementation. Further reduction in overall cost is achieved through decreased network downtime, lower maintenance cost, extended geometrical spans, and larger headroom for future capacity increase. These optically transparent networks represent a novel approach for implementing fiber-to-the-desk.     

A survey of hybrid optical data center network architectures

This paper presents a survey of data center network architectures that use both optical and packet switching components. Various proposed architectures and their corresponding network operation details are discussed. Electronic processing-based packet switch architectures and hybrid optical–electronic-based switch architectures are presented. These hybrid optical switch architectures use optical switching elements in addition to traditional electronic processing entities. The choice of components used for realizing functionality including the network interfaces, buffers, lookup elements and the switching fabrics have been analyzed. These component choices are summarized for different architectures. A qualitative comparison of the various architectures is also presented.     

Multistage WDM access architecture employing cascaded AWGs

Here we propose passive/active arrayed waveguide gratings (AWGs) with enhanced performance for system applications mainly in novel access architectures employing cascaded AWG technology. Two technologies were considered to achieve space wavelength switching in these networks. Firstly, a passive AWG with semiconductor optical amplifiers array, and secondly, an active AWG. Active AWG is an AWG with an array of phase modulators on its arrayed-waveguides section, where a programmable linear phase-profile or a phase hologram is applied across the arrayed-waveguide section. This results in a wavelength shift at the output section of the AWG. These architectures can address up to 6912 customers employing only 24 wavelengths, coarsely separated by 1.6 nm. Simulation results obtained here demonstrate that cascaded AWGs access architectures have a great potential in future local area networks. Furthermore, they indicate for the first time that active AWGs architectures are more efficient in routing signals to the destination optical network units than passive AWG architectures.     

Self-protected time-division-multiplexed passive access networks in tree and ring topology architectures

In this investigation we propose and experimentally demonstrate the self-protected and survivable time-division-multiplexed passive optical networks (PONs) in tree and ring topology architectures against fiber fault. Here, the feasible protection access architectures for the tree- and ring-based PONs are studied and discussed. Furthermore, different scenarios of fault locations, such as in the feeder fiber and distribution fiber, are also studied in the optical distributed networks.     

Forward error correction in WDM PON using spectrum slicing

This paper presents experimental results of the introduction of FEC (forward error correction) in optical access network architectures operating at 625 Mb/s. We have first tested a Reed Solomon code on a point to point architecture to confirm the theoretical 3 dB gain in link budget. The innovative architecture is a wavelength division multiplexed passive optical network (WDM PON) using spectrum slicing and a reflective semiconductor optical amplifier (RSOA) to generate upstream signals. Optical carrier supply by spectrum slicing and modulation and amplification by RSOA is a way of reducing costs in WDM PON but it gives a noisy transmission due to excess intensity noise of broadband sources, Amplified Spontaneous emission of the SOA and beat noise at detection. In this case, adding FEC has more effect and it results in an increased link budget of 5.5 dB. FEC are a simple and efficient solution to compensate for penalties introduced by low cost components in innovative architectures like WDM PON.     

Passive optical subscriber loops with multiaccess

Deployment of optical fiber in the subscriber loop may eventually lead to a full-scale deployment of the broadband network. A network architecture that can be introduced inexpensively to meet the near-term demand and upgraded smoothly to support future needs is desired. The feasibility of applying multiaccess architectures to subscriber loops is studied, and five architectures for passive optical subscriber loops that meet this need are presented. All of these architectures use a double-star topology and dense wavelength division multiplexing in the downstream direction; however, various topologies and multiaccess techniques are used in the upstream direction. Limitations on node size, frame synchronization, cost, privacy and security, and standards are discussed     

Architectures for large nonblocking optical space switches

This paper introduces three architectures for optical space switches that are based on a multiplicity of fiber interconnected optical components. The architectures eliminate the need for optical waveguide Crossovers and reduce the complexity required in the individual elements. The architectures are strictly nonblocking and allow for easy control and routing. Architecture type 1 exhibits a low system attenuation and a high system signal-to-noise ratio for very large switch dimensions. Architectures 2 and 3 are alternatives for realizing broadcast and point-to-point architectures.     

New architectures for optical TDM switching

A systematic theoretical study of architectures for optical TDM switching, using lithium niobate optical switches and optical fiber delay lines for storage, is undertaken. The architectures allow the bit rate and wavelength transparency of these devices to be exploited. A technique involving recursive definition and proof is used to define the networks, which are mathematically related to Benes and Waksman networks. This produces architectures that are very different from existing optical TDM networks. They exhibit economical use of components, which reaches the theoretical minimum in some cases. The use of feed-forward rather than feed-back delays give these networks superior crosstalk performance and more uniform attenuation than existing designs.<>     

Guest editorial broadband access networks: architectures and protocols

The 13 papers in this special issue cover a diversity of topics on the design of network architectures and protocols for passive optical networks (PONs), WiMAX networks, and integrated optical and wireless access networks.     

Nonlinear optic phase conjugation

An overview of the field of nonlinear optical phase conjugation is given. The basic properties of a phase-conjugate mirror are discussed, and examples of how this technology can be applied to the areas of high-power lasers, optical communication systems, and optical data processing (including neural networks) are presented. It is shown that the massively parallel data processing capabilities inherent in nonlinear optical interactions, coupled with their passive, all-optical nature, make this class of system potentially useful for the next generations of advanced laser systems, remote sensors, and communications systems, as well as optical data processors and network systems architectures     

From IP over WDM to all-optical packet switching: economical view

In this paper, a technoeconomical study of several (optical) packet-switching node architectures is described. Therefore, different architectures proposed in IST-WASPNET and IST-LASAGNE projects as well as a standard optical circuit switching approach are considered, and their economical impact is estimated by means of cost comparisons between the different technologies. The switching architectures all use optical fiber as a transport medium, but each of them uses a different technology to process switching. Their cost is evaluated as a function of most characteristic parameters for each technology. In the all-optical approaches, the main cost is that related to the fiber assembly, whereas for electronic processing, the most expensive cost is related to the optical-electronic-optical (OEO) conversions. The results show that the integration of optical components is crucial to make all-optical packet-switching nodes feasible.     

Flexible hybrid WDM/TDM PON architectures using wavelength selective switches

For building an optical access network, we propose some new hybrid WDM/TDM passive optical network (PON) architectures that use wavelength selective switches (WSSs) at the remote node to improve flexibility, data security and power budget. Through simulations we demonstrate that the switching capabilities of a WSS can provide additional gains in terms of wavelength usage by a better statistical multiplexing. Several WSS-based hybrid WDM/TDM PON variants are proposed and assessed. These architectures are also compared with the more commonly used hybrid WDM/TDM PONs consisting of power splitters and/or arrayed wavelength gratings (AWGs), in terms of cost and power budget.     

Jitter performance in ethernet passive optical networks

Ethernet passive optical networks (EPONs) have emerged as one of the most promising access network technologies. Propelled by rapid price declines in fiber optics and Ethernet components, these architectures combine the latest in optical and electronic advances and are poised to become the dominant means of delivering gigabit broadband connectivity to homes over a unified single platform. As this technology matures, related quality of service (QoS) issues are becoming a key concern. This paper proposes a novel dynamic scheduling algorithm, termed hybrid granting protocol (HGP), to support different QoS in EPON. Specifically, the proposed dynamic scheduling algorithm minimizes packet delay and jitter for delay and delay-variation sensitive traffic (e.g., voice transmissions) by allocating bandwidth in a grant-before-report (GBR) fashion. This considerably improves their performance without degrading QoS guarantees for other service types. Detailed simulation experiments are presented to validate the effectiveness of the proposed algorithm.     

Wavelength-tolerant optical access architectures featuringN-dimensional addressing and cascaded arrayed waveguide gratings

This paper describes two- and three-stage wavelength routed optical access networks, which offer wavelength tolerance by using coarse passband-flattened arrayed waveguide grating routers. An N-dimensional addressing strategy enables 6912 customers to be bidirectionally accessed with multi-Gb/s data using only 24 wavelengths and 1.6 nm spacing. These architectures are designed to map onto standard access network topologies, allowing elegant upgradability from legacy passive optical network (PON) infrastructures at low cost     

Optical computing and interconnects

This paper discusses the present status of optical computing and interconnects, including device technology, and recent progress in three types of optical computing-analog, digital, and neural-is introduced. Examples of technologies used in an analog computing system, a technique for the optimal design of coherent phase-only spatial filters, and a new version of incoherent filtering are presented. The use of the modified sign digit number representation and its applications to digital optical computing are also described. Some architectures for optical neural computing are introduced, and the importance of optical interconnect technology in parallel computing is stressed. Permutation techniques, the board-to-board level interconnection techniques, and switching techniques are reviewed. Recent developments in optoelectronic devices and passive optical elements are outlined and finally some technological issues in optical computing and interconnects for practical use are discussed     

Tree-type photonic switching networks

The enormous bandwidth offered by optical systems makes photonic switching a very attractive solution for broadband communications. Tree-type architectures play an important role in the design of photonic switching networks. The authors present and discuss all known tree-type space-division photonic switching networks architectures in a unified framework, and propose a number of new solutions. The discussed networks can be implemented with guided-wave-based switching elements, or laser diodes and passive splitters and combiners. The following network types are considered: conventional, simplified, and two-active stage networks. Techniques for improving SNR as well as waveguide crossover minimization are presented and discussed     

Optical beam forming techniques for phased array antennas

Three optical beam forming techniques are identified as applicable to large spaceborne phased array antennas. They are 1) the fiber replacement of conventional RF phased array distribution and control components, 2) spatial beam forming, and 3) optical beam splitting techniques. Two novel optical beam forming approaches, i.e., the spatial beam forming with a “smart pixel” spatial light modulator (SLM) and the optical beam splitting approaches are conceived with integrated quasi-optical components. Also presented are the transmit and receive array architectures with the new SLM.     

Next-generation PONs: a performance investigation of candidate architectures for next-generation access stage 1 - [Topics in optical communications]

Driven by bandwidth-demanding video applications, next-generation access stage 1, proposed by FSAN as the first stage of next-generation passive optical networks, increases the subscriber bandwidth by upgrading the current GPON network. To reduce the upgrading cost, NGA1 conforms to the standardized GPON and the deployed optical distribution network. This article presents the investigation of five candidate NGA1 architectures from the perspective of the MAC-layer bandwidth allocation including the analysis of the traffic characteristics of the subscribers? applications and the criteria in mapping them into proper transmission containers. Extensive simulations were conducted to investigate and compare the performances of the five candidate NGA1 architectures.