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Small silicon photonics micro-resonator modulators and filters hold the promise for multi-terabit per-second interconnects at energy consumptions well below 1 pJ/bit. To date, no products exist and little known commercial development is occurring using this technology. Why? In this talk, we review the many challenges that remain to be overcome in bringing this technology from the research labs to the field where they can overcome important commercial, industrial, and national security limitations of existing photonic technologies.

As the bit rates of routed data streams exceed the throughput of single wavelength-division multiplexing channels, spectral and spatial traffic aggregation become essential for optical network scaling. These aggregation techniques reduce network routing complexity by increasing spectral efficiency to decrease the number of fibers, and by increasing switching granularity to decrease the number of switching components. Spectral aggregation yields a modest decrease in the number of fibers but a substantial decrease in the number of switching components. Spatial aggregation yields a substantial decrease in both the number of fibers and the number of switching components. To quantify routing complexity reduction, we analyze the number of multi-cast and wavelength-selective switches required in a colorless, directionless and contentionless reconfigurable optical add-drop multiplexer architecture. Traffic aggregation has two potential drawbacks: reduced routing power and increased switching component size.

The traffic carried by core optical networks grows at a steady but remarkable pace of 30-40% year-over-year. Optical transmissions and networking advancements continue to satisfy the traffic requirements by delivering the content over the network infrastructure in a cost and energy efficient manner. Such core optical networks serve the information traffic demands in a dynamic way, in response to requirements for shifting of traffics demands, both temporally (day/night) and spatially (business district/residential). However as we are approaching fundamental spectral efficiency limits of singlemode fibers, the scientific community is pursuing recently the development of an innovative, all-optical network architecture introducing the spatial degree of freedom when designing/operating future transport networks. Spacedivision- multiplexing through the use of bundled single mode fibers, and/or multi-core fibers and/or few-mode fibers can offer up to 100-fold capacity increase in future optical networks. The EU INSPACE project is working on the development of a complete spatial-spectral flexible optical networking solution, offering the network ultra-high capacity, flexibility and energy efficiency required to meet the challenges of delivering exponentially growing traffic demands in the internet over the next twenty years. In this paper we will present the motivation and main research activities of the INSPACE consortium towards the realization of the overall project solution.

The overall spectral efficiency in optical transmission systems need to be enhanced by employment of advanced modulation and coding schemes as well as the advanced detection techniques. In parallel, novel networking concepts with the griddles and elastic bandwidth allocation are needed to increase the network dynamics and flexibility. In this paper we provide an overview of these techniques and concepts, which have been or may be used in the next generation high-speed optical network.

In order to solve capacity and energy-efficiency problems of future Internet technologies simultaneously, in this paper, we propose the use of energy-efficient N-dimensional (ND) orbital angular momentum (OAM) coded-modulation. The energy-efficient signal constellation is obtained by employing the energy-efficient signal constellation design algorithm. This scheme can achieve beyond 100 Gb/s transmission while employing the state-of-the-art 10 Gb/s technology. The proposed scheme significantly outperforms conventional M-ary PAM. The proposed scheme represents a promising candidate for indoor optical wireless communication, terrestrial free-space optical (FSO) communication, data center applications and can be used as enabling technology for heterogeneous optical networking, thanks to its transparency to both free-space optical and few-mode/multimode fiber links.

Silicon photonics is an emerging technology offering novel solutions in different areas requiring highly integrated communication systems for optical networking, sensing, bio-applications and computer interconnects. Silicon photonicsbased communication has many advantages over electric wires for multiprocessor and multicore macro-chip architectures including high bandwidth data transmission, high speed and low power consumption. Following the INTEL's concept to "siliconize" photonics, silicon device technologies should be able to solve the fabrication problems for six main building blocks for realization of optical interconnects: light generation, guiding of light including wavelength selectivity, light modulation for signal encoding, detection, low cost assembly including optical connecting of the devices to the real world and finally the electronic control systems.

As the demand for higher capacity and longer reach of optical access networks is garnering momentum in recent years, coherent access technology attracts renewed interests in high-capacity optical networking. In this paper, designs of various coherent access networks are investigated and compared. From our results, it may be the most promising solution with high capacity at optimized cost. When coherent detection is employed in access network, the laser linewidth is a key design issue for optimized performance and cost as laser phase noise is larger with lower bit rate. One of our objectives is to examine the feasibility of employing a conventional DFB as carrier sources. We evaluated the performance of ultra-dense WDM access networking system. Experimental results show that 2.5GB/s QPSK data can be transmitted over 35-km SMF-28 with 6.5GHz channel spacing using DFB lasers.

The demand for 100 Gb/s optical links is rapidly spreading across all levels of the optical networking infrastructure. Many of the first deployments will be in the local area network (LAN) and metro-core and regional network environments. To address needs in LAN, the upcoming IEEE standard (IEEE P802.3ba) seeks 100 Gb/s over distances up to 40km. Furthermore metro-core/regional dense wavelength division multiplexing (DWDM) architectures require reach of several hundred km and the ability to pass through ten or more ROADMs. However, a number of fundamental challenges remain including the selection of appropriate modulation formats that are robust to a variety of nonlinearities, are sufficiently spectrally efficient, and able to withstand the strong optical filtering of cascaded ROADMs. Here we compare a variety of single-carrier quaternary modulation formats, each providing 2 bits/symbol/polarization and each likely to provide some advantages at 100Gb/s. Each format is presented with an appropriate MZM-based transmitter, and constrained by practical signal fidelity limitations that also enable comparison to experimental results from our 100G testbed. We primarily examine direct detection for cost-sensitive metro networks; however we also quantify the performance of coherent receivers, where applicable. Simulation results demonstrate the relative OSNR penalty (at a pre-FEC BER of 10-3) for a range of launch powers and adjacent channel formats.

In this paper, we review recent developments in coherent, spectral phase encoded optical code-division multiplexed (OCDM) systems employing integrated micro-ring resonator coding technologies and consider its application to data confidentiality in optical networks. In addition, we discuss how such systems can be designed to be compatible with conventional dense wavelength-division multiplexing (DWDM) networking, and review our experimental progress in advanced modulation formats for improved spectral efficiency (up to 0.87 b/s/Hz) as well as the capability for long transmission distances (up to 400 km).

Despite the initial skepticism of OEM companies regarding reliability, MEMS-based devices are increasingly common in optical networking. This presentation will discuss the use and reliability of MEMS in a variety of network applications, from tunable lasers and filters to variable optical attenuators and dynamic channel equalizers. The failure mechanisms of these devices will be addressed in terms of reliability physics, packaging methodologies, and process controls. Typical OEM requirements will also be presented, including testing beyond of the scope of Telcordia qualification standards. The key conclusion is that, with sufficiently robust design and manufacturing controls, MEMS-based devices can meet or exceed the demanding reliability requirements for telecommunications components.

We have experimentally demonstrated how to generate, transmission and switching 100Gbit/s packet signals. The performance of transmission, switching, and label erasure has also been evaluated.

Scientific research shows an ever-growing demand for more and higher quality network services. In 2001 the idea began to take hold at SURFnet that we had reached the boundaries of using ever faster connections and ever larger routers to satisfy this demand and that the heavy scientific utilisation of the network posed a growing risk for regular Internet traffic. SURFnet concluded that a simple extrapolation of then current layer3 networks would most likely not be the right answer. This presentation describes how SURFnet started to explore end-to-end lightpath provisioning as an alternative. This exploration has led to the realisation of SURFnet6 as a hybrid optical and packet switching infrastructure, NetherLight as an Open Lightpath Exchange and GLIF as a global facility for lambda networking.

We have designed and experimentally demonstrated optical networking technologies for generating, transmitting and switching 100Gbit/s packet signals in optical networks. The performance of 100Gb/s packet transmission over cascaded ROADM nodes with WSSs and over label switched metro networks are discussed.

Recently, optical burst switching (OBS), which represents a balance between circuit and packet switching, has opened up some exciting new dimensions in optical networking. Burstification is an important process in OBS networks. Due to the burstification, there are two opposite effects on TCP throughput in OBS networks: delay penalty and amplification effects. In this paper these two effects are experimentally investigated simultaneously for the first time based on an OBS mesh network testbed and some valuable experimental results are achieved. Experimental results show that when BTT is less than 1.5ms, and BLT is in the BLT window, the positive effect on TCP throughput is dominant. On the other hand, if BTT is larger than 1.5ms, the BLT window will be closed, thus the delay penalty will become the dominant effect in the OBS networks.

The unprecedented proliferation of packet-based services such as numerical television, video on demand, is pushing Metropolitan Area Networks (MANs) providers to reconsider their network infrastructures. The existing circuit-based networks are becoming inefficient and costly in supporting the new requirements in terms of quality of service and bandwidth of sporadic packet-based traffic. To solve this problem, new MAN infrastructures are needed. Many propositions of new network solutions were made during the last decade in order to respond to the aforementioned issues, such as Next Generation SONET/SDH, Resilient Packet Ring (RPR). Among others, the optical networking technology appears as a technology of choice for the next generation MANs. The main benefit of optical technology can be resumed in the following terms: huge transmission capacity, high reliability, and high availability. This paper is devoted to provide an overview of the MAN infrastructure, and particularly to its evolution towards optical packet switching (OPS) networks, during the last decades. It also highlights performance issues in optical networking in metro area in terms of optical packet format, medium access control (MAC) protocol and quality of service (QoS), as well as traffic engineering issues. We first begin with a brief state-of-the-art and perspective on optical networking in metropolitan area. Next, we provide the necessary arguments for an answer to the problem of the choice of packet format (fixed format versus variable format) to be adopted in future metropolitan optical packet switching networks. Comparison of different optical packet formats at the electronic to optical (E/O) interface is carried out, followed by the analysis of the impact of optical packet format choices on overall network performance. Then, we explore the performance issue at MAC layer and discuss improvement mechanisms for MAC protocol. Here, fairness and bandwidth utilization issues are specifically investigated. Finally, we discuss about how to guarantee QoS in optical packet switching OPS metro networks, illustrated by a few mechanisms allowing the transport of TDM traffic over packet switching networks (e.g., Circuit Emulation Service - CES).

Internet Traffic has been growing multifold with time, as more and more people are getting online for communication, education, entertainment, etc. Expanding fiber optic networks through optical networking is seen as the key to fulfilling consumer demand for internet bandwidth. Optical networking is severely handicapped by the unavailability of high performance low cost optical components. Developing economical methods for fabricating optical switches, connectors and other networking components is the key to the realization of an all-optical network vision. Using silicon MEMS technology to produce optical components provides some compelling advantages of integration with electronic devices and packaging. Simple, low-cost fabrication of the integrated optical components such as waveguides, splitters, combiners, reflectors and lenses on silicon substrate is reviewed. Specially designed novel dispensing equipment is used to fabricate these optical components. An integrated optoelectronic switch is designed using silicon V-grooves with reflective taps and dispensed polymer waveguides. Propagation losses of 0.15 dB/cm at 633 nm and 0.45 dB/cm at 1300 nm are reported. Coupling losses of less than 1 dB can be achieved. The fabrication being economical and having lower propagation losses makes this technology very attractive for networking applications.

In spite of its long term promise, all-optical switching is still plagued by high cost, low efficiency when handling bursty data traffic, immature management and protection and poor output port contention resolution leading to heavy loss. Given the current situation, hybrid approaches that keep the best features of optics, reverting to the electrical plane when expedient, constitute sensible interim steps that can offer cost-effective solutions along the road to an eventual all-optical core. Two such approaches developed in the framework of the European IP project NOBEL are presented in this work. The first is a quite mature solution that extends present day concepts to achieve multiplexing gain while keeping all the management and restoration benefits of SDH. The other mimics early LANs in executing a distributed switching via its electrical control plane using two-way reservations, thus restricting its applicability to smaller domains. Combining the two leads to a system fulfilling most of today's requirements for Tb/s core networks.

Optical networking attracted a lot of interest in the telecommunication industry during the late 1990s. This interest has weakened since the downturn of this industry in 2000-2001 and throughout the post bubble years. Today, there are signs that optical networking is coming back. In this paper, we examine the current status of optical networking and switching, in terms of deployment in communication networks. We provide a status update in the telecommunication and cable industries. We also discuss today's trend toward relying on optical networks in advanced research and education (R&E) networking initiatives.

Due to the recent outstanding advancement of optical networking technology, pervasive Grid computing will be a feasible option in the near future. As Grid infrastructure, optical networks must be able to handle different Grid traffic patterns with various traffic characteristics as well as different QoS requirements. With current optical switching technology, optical circuit switching is suitable for data-intensive Grid applications while optical burst switching is suitable to submit small Grid jobs. However, there would be high bandwidth short-lived traffic in some emerging Grid applications such as multimedia editing. This kind of traffic couldn't be well supported by both OCS and conventional OBS because of considerable path setup delay and bandwidth waste in OCS and inherent loss in OBS. Quasi-Circuit OBS (QCOBS) is proposed in this paper to address this challenge, providing one-way reserved, nearly lossless, instant provisioned wavelength service in OBS networks. Simulation results show that QCOBS achieves lossless transmission at low and moderate loads, and very low loss probability at high loads with proper guard time configuration.

IP+Optical networking technology is a key technology for realizing high-performance Internet backbone networks. Dynamic optical path cut through can create high-throughput as well as low power consumption networks. National Institute of Information and Communications Technology (NICT) Kei-han-na Info-Communication Open Lab, Interoperability Consortium, is shooting for the leading edge photonic Generalized Multi-protocol Label Switching (GMPLS) Inter-Carrier Interface that utilizes wide-bandwidth, cost-effective photonic technology to implement IPcentric managed networks. Kei-han-na Open Lab is a consortium for researching the GMPLS protocol and advancing a de facto standard in this area. Its experiments, new ideas, and protocols are submitted to standardization bodies such as International Telecommunications Union-Telecommunication standardization sector (ITU-T), Internet Engineering Task Force (IETF), and Optical Internetworking Forum (OIF). This paper details a nationwide GMPLS field trial that used multi-vender, multi-switching capable equipment.

Broadband wireless access operating in the microwave and millimeter-wave frequency windows has been actively investigated for future ultra broadband communications. The drastic increase in the throughout of each base station in these systems necessitates the use of an optical fiber backbone to provide broadband interconnections between the central office and all the antenna base stations. With such a network layout, significant reduction of the antenna base station complexity can be achieved by moving the routing, switching and processing functionalities to the central office. By taking advantage of optical networking techniques such as wavelength division multiplexing (WDM), the total capacity of the hybrid fiber-wireless network can be greatly enhanced and efficient optical fiber architectures can be realized. In this paper we present an overview of the research that has been carried out in fiber-wireless networks incorporating WDM, with a particular focus on the optical interfaces in such networks.

Optical communications technologies are being actively explored by the defense and security communities as a potential solution to alleviate bandwidth bottlenecks and to provide covert, jam resistant communications without spectrum restrictions. While static fiber-optic networks are widely deployed in the Department of Defense (DoD) communications network, the integration of wireless, free space optical (FSO) communications technology is required to provide end-to-end high bandwidth paths to support mobile defense and security operations. This paper presents an analysis of inherent benefits of optical wireless communications technologies in enabling net-centric applications and discusses specific technology and architectural challenges that need to be overcome before these technologies can be seamlessly integrated in the Global Information Grid (GIG) to fully realize the net-centric vision.

Optical communication systems have evolved from simple point-to-point transmission systems in the late 1970's to today's multi-channel DWDM systems integrated with optical switching. These advanced DWDM systems have very stringent optical performance, system reliability, and cost requirements. As a result, deployment of these systems has been limited to date. This situation has started to change recently and a lot of industry interest is now focused on deploying advanced optical systems in high performance telecommunication environments. Integrating optical functions in a single opto-electronic integrated circuit (OEIC) has the potential to accelerate this deployment by reducing manufactured costs, reducing physical card size, and increasing reliability. This paper will describe a specific instance of a DWDM transport and optical switching system, and its functional decomposition into individual cards. The requirements that are then imposed on the optical components placed on these cards are described. We will show the function of advanced switching and optical monitoring. Initial validation of a system card was made using off-the-shelf discrete optical components and then replaced with an OEIC implementation. Results of the integration experience will be presented.

This paper motivates the combination of optical burst switching (OBS) networks with wavelength-routed networks which provide a virtual topology. Opportunities for advanced network design, support for important future transport network scenarios, and resilience as well as capacity adaptation functionality are among its key benefits. The paper discusses principal trade-offs, both qualitatively and quantitatively, regarding virtual topologies and statistical multiplexing in order to derive guidelines for resource efficient topology design. Then, the OBTN architecture is described, which can efficiently transport burst data over a virtual topology of lightpaths and can reduce the port count of optical burst-switched nodes. Finally, the OBTN dimensioning process is outlined and results of a unified performance and cost comparison are presented.

To date, the mainstream Ethernet Passive Optical Network (EPON) bandwidth allocation schemes as well as the new IEEE 802.3ah Ethernet in the First Mile (EFM) Task Force specifications have been centralized, relying on a component in the central office, Optical Line Termination (OLT), to provision upstream traffic. Hence, the OLT is the only device that can arbitrate time-division access to the shared channel. Since the OLT has global knowledge of the state of the entire network, this is a centralized control plane in which the OLT has centralized intelligence. One of the major problems associated with a centralized architecture is the "single-point of failure" problem that is the failure of the OLT software will bring down the whole access network. It is the purpose of this work to propose a distributed solution to this problem, and to devise and experimentally demonstrate the feasibility of implementing a novel Ethernet over Star Coupler-based PON architecture that uses a fully distributed time division multiple access arbitration schemes. Specifically, we assess the viability of implementing a distributed control plane architecture that facilitates internetworking among connected users. In addition to the added flexibility and reliability associated with distributed control plane architecture, as well as emulating shared LAN capability among different users, the distributed networking architecture and the associated bandwidth allocation algorithms have characteristics that make them far better suited for provisioning Quality of Service (QoS) schemes necessary for multimedia services over a single line.

The different flavors of today's and future multilayer transmission networks are analyzed highlighting the main infrastructure, capital expenditure (CAPEX) and operational expenditure (OPEX) contributions to total cost of ownership (TCO). Depending on different carrier requirements, critical parameters and general design rules for optimum overall cost positions are discussed. To illustrate and evaluate the impact of given boundary conditions, some case studies will be presented where new technologies lead to significant OPEX/CAPEX savings.

Quantum key distribution (QKD) is an emerging technology for secure distribution of keys between users linked by free-space or fiber optic transmission facilities. QKD has usually been designed for and operated over dedicated point-to-point links. However, the commercial world has been developing increasingly sophisticated fiber networks, with basic networking functions such as routing and multiplexing performed in the optical domain. One of the most important practical questions for the future of QKD is to what extent it can benefit from these trends, either to expand the capabilities of dedicated quantum networks, or to avoid the need for dedicated networks by combining quantum and conventional optical signals onto a single infrastructure. In this paper, we report on systematic investigations of these issues using a 1310-nm weak-coherent, phase-encoded B92 prototype QKD system developed by Los Alamos that includes the implementation of error correction, privacy amplification, and authentication. We have demonstrated reconfigurability of QKD networks via optical switching and successful QKD operation in the presence of amplified DWDM signals over 10 km of fiber. We have identified anti-Stokes Raman scattering of the DWDM signals in the fiber as a dominant transmission impairment for QKD, and developed filtering architectures to extend transmission distances to at least 25 km. We have also measured noise backgrounds and polarization variations in network fibers to understand applicability to real-world networks. We will discuss the implications of our results for the choice of QKD wavelengths, wavelength-spacing between QKD and conventional channels, and QKD network architectures.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Presently, formerly independent autonomous optical links are growing increasingly into meshed networks making measures for performance monitoring and automated error analysis a necessity. At the same time adaptive electronic equalizers are becoming integrated by default into optical receivers in order to mitigate distortions which are ubiquitous on every fiber link. In this paper we investigate the possibility of using these already available components for identifying and quantifying optical distortions and thus, performing network monitoring without additional expensive optical equipment.

This paper introduces a design for a high capacity multicasting capable Optical Packet Switched Router (OPSR). It incorporates an Arrayed Waveguide Grating (AWG) as its core switching matrix to manage the ever increasing packet switched traffic within the optical network. The OPSR has the capability to switch optical packet traffic through the AWG with a switching speed of a few nano-seconds (nsec) at a bit rate of 10Gbps and above with multicasting capability. The capabilities offered by this OPSR will speed up all-optical packet switching and reduce packet latency and consequently packet loss.

Currently existing dense wavelength division multiplexing (DWDM) networks start to migrate from numerous point-to-point links towards meshed, transparent, optical networks with dynamically routed light paths. This increases the need for appropriate network monitoring and supervision methods. Optical performance monitoring (OPM) has to be cost-effective. Thus additional spendings for OPM have to be significantly smaller than the savings in OPEX due to increased reliability and ease of operation, administration, and maintenance (OAM). We elaborate on different advanced monitoring concepts. First, we discuss general failure scenarios in meshed networks. Then we describe software based failure root cause analysis and its implementation. We conclude that by implementing appropriate software algorithms in the network hardware effort can be significantly reduced. Finally, we assess different advanced OPM methods which may show up as useful to enable OPM in future optical networks.

All-optical modules are devices which process and transport optical signals without transforming to electronic signals. They get more attention as the optical communication network becomes more and more complicated. Among them, OADM (optical add drop module) is one of the most important devices in the optical DWDM (dense wavelength division multiplex) network. It plays the role of a node in network to upload/download signals or to route signals for optical performance monitoring. Applied broadly in projection display systems, DLP TM (Digital Light Processing TM ) from Taxes Instruments turns out to be a versatile device for optical signal processing. The working principle of DLP is based on so called switched-blazedgrating. Part of its micro-mirror array can be formed as a dynamic blazed grating with a period of 14 µm by tilting the micro-mirrors at an angle of 12 degrees. It is expected to function as either a switch or an attenuator by directing total or part of the incident light between the 2 nd and –2 nd diffraction orders. In this paper, we investigate the optical characteristics of a switched-blazed-grating, its application as a re-configurable OADM, and the performance of such a device. Ray tracing and optical analysis of the OADM are made by using package software ASAP TM from Breault Research Organization. In conclusion, as a mature and reliable MEMS device, DLP TM -based switched-blazed-grating provides a very versatile platform for digital optical signal processing and can be

Evolving carrier networks are starting to include optical networking, but current optical elements form islands of communications, not the utopian “global intelligent optical network” that is the end goal. Although dense wavelength division multiplexer (DWDM) technology leverages the cost and availability of fiber, each wavelength in DWDM links needs its own transponder, an expensive O-E-O (opto-electrical-opto) device in which optical signals are converted back to their electrical (binary) format to process the information. In today’s carrier networks, O-E-O is needed to terminate each optical end point in order to deliver it in its correct format to the specific addressees using high-level format-dependent protocols. The presentation will discuss how 60-80% of all traffic that passes through an O-E-O switch at midpoints in a network typically does not require processing at those points and, in fact, get re-converted and re-transmitted. The equipment that does this costs millions of dollars; takes up more space; uses a lot of power (expense and heat); and creates additional opportunities for network failures. Adding O-O-O (photonic, or all–optical) switches to the architecture as needed allows higher speeds, less real estate, lower capital and operational expenditures, improved network reliability, and better customer response.

Current optical communication systems are more and more relying on the advanced opto-electronic components. A series of revolutionary optical and optoelectronics components technology accounts for the fast progress and field deployment of high-capacity telecommunication and data-transmission systems. Since 1990s, the optical communication industry in China entered a high-speed development period and its wide deployment had already established the solid base for China information infrastructure. In this presentation, the main progress of optoelectronics components and technology in China are reviewed, which includes semiconductor laser diode/photo receiver, fiber optical amplifier, DWDM multiplexer/de-multiplexer, dispersion compensation components and all optical network node components, such as optical switch, OADM, tunable optical filters and variable optical attenuators, etc. Integration discrete components into monolithic/hybrid platform component is an inevitable choice for the consideration of performance, mass production and cost reduction. The current status and the future trends of OEIC and PIC components technology in China will also be discuss mainly on the monolithic integration DFB LD + EA modulator, and planar light-wave circuit (PLC) technology, etc.

To explore the need for a graduate level engineering course in optical networking, a needs assessment consisting of (i) an investigation of 14 existing optical networking courses, (ii) an analysis of online surveys among the networking community and the ASU electrical engineering department, (iii) faculty interviews, and (iv) focus groups was conducted. Survey responses from a total of 61 respondents were received and analyzed. The results support the need for a graduate level course in optical networking. Our analyses indicate that a graduate course in optical networking should (i) focus on the basic mechanisms and current trends in optical networking, (ii) be based on a text book and instructor slides combined with collections of examples and problems. Regarding the optimal delivery method it was found that current students and faculty strongly prefer face-to-face delivery complemented by on-line readings and assignments, whereas working engineering professionals are more open to the idea of online courses.

Future multi-terabit/s optical core networks require optical technologies capable of managing ultra-high bit rate OTDM/DWDM (optical time division multiplexing/dense wavelength division multiplexing) channels at 160 Gbit/s or higher bit rates. The key functionalities in ultra-high speed network nodes are all-optical wavelength conversion, 3R-regeneration and demultiplexing of OTDM signals. Advanced optical networking techniques (optical add-drop multiplexing and optical routing) are studied in simulations and their performance evaluated considering 160 Gbit/s OTDM/DWDM channels. Performance comparison results for both OADM (optical add-drop multiplexer) and OXC (optical cross-connect) node networking functionalities are shown considering different technologies: semiconductor-optical-amplifier-based symmetric Mach-Zehnder interferometers (SOA-MZI) for wavelength conversion, signal regeneration and demultiplexing, electroabsorption-modulator-based demultiplexers, and wavelength converters based on four-wave mixing in dispersion-shifted fiber. The simulation results show that the SOA-MZI is a promising technology for all-optical signal processing in network nodes mainly due to its signal regeneration capability. At ultra-high bit rates, however, the relaxation time of SOAs considerably limits the operation. A solution to mitigate this problem is to use a differential scheme at the input of the device. Error-free wavelength conversion, signal regeneration and demultiplexing of 160 Gbit/s OTDM signals employing a SOA-MZI with a differential scheme is demonstrated by means of simulations. Furthermore, the parameters of this architecture are optimized to obtain the best performance for each optical networking functionality in OADM and OXC network nodes.

Recent laboratory experiments have demonstrated that distributed Raman amplification, advanced modulation formats, optimized dispersion maps, and forward error correction are key technologies for 10-Gb/s and 40-Gb/s DWDM terrestrial transmission over 2000 to 6000 km. The transmission fiber's Raman gain efficiency and dispersion properties are thus important parameters. Future high-bit-rate, high-capacity installed systems will require advanced transmission fibers to extend their reach to at least 2000 km, a distance also specified by a high-profile U.S. government optical networking project. This paper will address a number of the enabling fiber properties, including dispersion, dispersion slope, Raman gain efficiency, and polarization mode dispersion. In addition, several recent experiments will be reviewed, including demonstrations of high-spectral-efficiency terrestrial transmission at 10 Gb/s and 40 Gb/s over 4000 km and 3200 km, respectively, and 10-Gb/s transmission over 2400 km using 200-km spans.

Vertical Cavity Surface Emitting Lasers (VCSELs) are now essentially the only source used in short distance high bit rate data communications over multimode optical fiber. First commercially realized in 1996 by Honeywell, the primary application has been single channel links operating Ethernet or Fibre Channel protocols in the LAN and SAN environments. Today, the total bandwidth throughput is being raised to more than 10Gbps per channel, with the potential of several channel operation to yield more than 100Gbps. 850nm VCSELs are beginning to emerge in relatively new application arenas and wavelengths. This paper describes the market readiness for VCSELS in a wide variety of optical networking applications.

Optical networking, with its almost unlimited bandwidth, is the only technology that can support communication new applications with high demand for bandwidth such as remote visualization, teleimmersion, collaborative e-science etc. In the optical networks presently deployed, each link is optically isolated by transponders doing O/E/O conversions. But these transponders are quite expensive and lack transparency; hence there is a strong motivation to use large all-optical networks. In all-optical networks, all routes need not have adequate signal quality. To provide reliable and transparent service, there is a strong interest in the industry for routing protocols that take into consideration the impairments of optical layer that degrade quality of the signal. We present a new routing protocol that uses information about the quality of signal to select paths in an all-optical network. Our simulations confirm that this new protocol reaches higher network utilization compared to existing ones.

Optical amplification and dense wavelength division multiplexing (DWDM) have fundamentally changed optical transport networks. Now that these technologies are widely adopted, the bottleneck has moved from the outside line plant to nodal central offices, where electrical switching equipment has not kept pace. While OEO technology was (and still is) necessary for grooming and traffic aggregation, the transport network has dramatically changed, requiring a dramatic rethinking of how networks need to be designed and operated. While todays transport networks carry remarkable amounts of bandwidth, their optical layer is fundamentally static and provides for only simple point-to-point transport. Efficiently managing the growing number of wavelengths can only be achieved through a new breed of networking element. Photonic switching systems (PSS) can efficiently execute these functions because they are bit rate, wavelength, and protocol transparent. With their all-optical switch cores and interfaces, PSS can switch optical signals at various levels of granularity wavelength, sub band, and composite DWDM fiber levels. Though cross-connect systems with electrical switch cores are available, they perform these functions at very high capital costs and operational inefficiencies. This paper examines enabling technologies for deployment of intelligent optical transport networks (OTN), and takes a practical perspective on survivability architecture migration and implementation issues.

Optical ADD/DROP multiplexers (OADM) are incorporated into all-optical network structures that provide fixed access to a subset of the wavelengths in Wavelength Division Multiplexer (WDM) systems. The rapid growth of broadband data communications and the drive toward cost reduction have made optical MEMS (Micro-Electro-Mechanical Systems) an extremely attractive technology for applications in optical communications. This paper will present theoretical analysis, simulation and testing results of an ADD/DROP multiplexer based on the MEMS-based micro-actuators. The micro-actuator is a MEMS-based compound grating (MCG) with a reconfigurable surface that couples the mechanical motion with optical diffraction. The diffraction patterns depend on the wavelength, incident angle and the grating structural parameters. This property is used to design an OADM that can be applied to broad areas in optical communication. A theoretical analysis is presented to establish the relationship between diffraction beams and the structural parameters of the grating, the wavelength of incident light, incident angle. Prototypes of these micro-actuators have been fabricated. The initial testing demonstrated the feasibility of using the MCG as an OADM. New designs of the MCG for application to the 1.55um optical telecommunication standard will be discussed.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The electromechanical characteristics of a novel micro torsion-mirror actuator and the optical properties about the light scattering and reflection of its micro-mirror under the influence of mirror surface roughness are investigated experimentally and theoretically. The electrostatic yielding voltages for driving the metal-coated polysilicon or single crystal silicon micro-mirrors suspended by elastic torsion beams to tilt from 0° to 90° spontaneously are in the range of 270~290 V and the minimum holding voltages for keeping the tilting angle of the mirrors to be in 90° are found 55 V or so when the thickness of the torsion-beams is about 1 ?m. The lifetime and the estimated shortest actuating time of the micro torsion-mirror actuators can reach 108 at least and less than 2 ms, respectively. The maximum value of the surface roughness of the micro-mirrors is 69.443 nm and the distribution of the surface roughness is smooth, which is acceptable for wavelength division multiplexing applications basically. In general, the novel torsion-mirror actuators can be applied as optical switches for optical networking.

In this work, we review several different types of optical signal processors utilizing liquid-crystal technologies. These optical components include optical switches, voltage-controlled variable attenuators and optical harmonic equalizers for WDM (wavelength-division-multiplexing) applications.

Optical network Survivability in the backbone, or core, network has been an active area of research. As optics move closer to the edge and to end users, the core network is now used not only to provide connections across a wide area,but also to provide connections for local and metropolitan area networks (LANs and MANs). While optical backbone networks are generally concerned with providing end-to-end circuits based upon whole wavelengths, optical LANS and MANs generally provide shared access to a small number of wavelengths. In this paper, we consider the issue of robustness for optical access networks built as overlays on optical mesh networks. The problem of optical access network robustness is that of maintaining connectivity among nodes of the access networks after a link (or possibly node). We survey three methods of providing robustness to optical access networks. The first method consists of building access networks as covers of rings. The second method builds folded bus overlays and use a combination of optical switches and electronic routers to provide reliability. The third generalizes the concept of buses to build tree-based robust collection and distribution routes over mesh networks. Optical access networks are beginning to be deployed at the edge of the optical backbone network to support access by the high-end users that drive increased bandwidth demands. This development in the applications of optical networking poses new challenges in the areas of medium access, topology design and network management. In this article, we survey access network architectures and outline the issues associated with providing reliability for these architectures.

Bossnet is an in-ground testbed for developing optical networking techniques that enable new applications. The use of in-ground fiber (as opposed to laboratory experiments) allows new applications that require high data-rate communications over long distances to be tested. For the experiments described here, the light path includes ten spans of optical fiber with distances varying between 40 km and 73 km located on telephone poles and in the ground near railroad tracks and roadways. After each link, the light is amplified, filtered, and chromatic dispersion compensated. The experiment operates one 40-Gb/s RZ (return-to-zero format) channel at 193.5 THz and seven other channels with 10-Gb/s NRZ (non-return-to-zero format) modulation over a distance of 295 km from Lincoln Laboratory to New London, CT. These channels are dropped from the southbound fiber in New London and are added on the northbound fiber back to Lincoln Laboratory. This experimental arrangement allows the transmitter and receiver to be located in the same laboratory. A ninth channel, at 193.8 THz, carries Gigabit Ethernet traffic in both directions between Lincoln Laboratory and Washington, DC. Model calculations for the optical network produce eye diagrams in excellent agreement with the experimental results.

When light propagates through optical elements (such as lenses), it undergoes a transform. The input and the output data take the form of light and optical elements that perform different mathematical operations on light represent th linear transform. The transform is performed not on the discrete elements of the data but on the whole vector at once, and most significantly, at the speed of light. The great advantages offered by optical processing are that it offers enormous parallelism, operating on all data points simultaneously, very low latency, a high transform rate and low power dissipation. The outcome is enormously increased speed and a reduction in the amount of associated cooling required. The Optical Signal Processor (OSP) increases the speed of processing transforms by many orders of magnitude. The Signal Processor is also reconfigurable and can be dynamically tailored to the required transform type. One advantage of an optical processor is that it allows software designers to work at a much higher level of abstraction. This is because the device executes transforms instead of the ordinary MACs in the case of DSPs. Instead of handling algorithms at individual data points, algorithms for handling the entire vector could be processed, shortening the computational complexity and speeding the time-to-market for new products. An optical filter can be represented as a generic function, the most fundamental of the optical processor. The impulse response of this filter is defined with respect to frequency of light. Any transform on light can be represented as a combination of linear transforms. This is fundamentally the law of optical signal processing. The most important application of an OSP in Optical Networking is pattern recognition, and this can easily be done by the usual cross-correlation technique that is common in digital signal processing. The OSP can be programmed to autocorrelate against specific temporal reference waveforms, viz. Data. The decoding is done without electronic processing. And of course, the routing of optical signals is based on content. This paper provides insight to this efficient and novel method of computation and signal processing.

We present an accurate model for burst traffic characteristics inside optical burst switched networks. At the edges of such networks, a number of IP packets are collected before being injected into the core as a single unit. The sizes of these so-called bursts critically impact the performance of the various network elements, so that a good understanding of their characteristics is an essential step in network performance engineering. A further abstraction of this assembly process results in a straightforward simulation model that can eliminate the need for packet level simulation, and thus reduce model complexity and simulation cost.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A design methodology for an optical mesh network has recently been developed. For a given backbone packet network, we assume that a traffic matrix and an underlying optical fiber network are given. It is necessary to establish logical links between backbone nodes using optical wavelengths over the fiber network. The methodology chooses and sizes logical backbone links, chooses the physical paths for these logical links, and determines traffic routings over logical links under both normal and failure conditions. The methodology utilizes a linear programming engine embedded within a heuristic framework. This work presumes an optical networking environment utilizing dense wavelength division multiplexing (DWDM) and intelligent optical switch (lOS) equipment. It can be used to study potential future networks with high levels of traffic, e.g., in which demand entering the network at any given instant may be measured in terabits per second. In this paper, we describe the optical mesh network design problem that is addressed, outline the solution methodology and discuss some computational experience.

The demand in optical networking for photonic components that meet performance criteria as well as economic requirements has opened the door for novel technologies capable of high-yield low-cost manufacturing while delivering high performance and enabling unique functions. The most promising new technologies are based on integrated optics. Integration permits the parallel production of complex multi-function photonic circuits on a planar substrate. Polymeric materials are particularly attractive in integrated optics because of their ability to be processed rapidly, cost-effectively, and with high yields; because they enable power-efficient dynamic componentry through thermo-optic and electro-optic actuation; and because they allow to form compact optical circuits by offering large refractive index contrasts (index difference values between waveguide core and cladding). We compare the properties of optical polymers with those of other material systems utilized in integrated optics. We present an up-to-date snapshot of the global effort in optical polymer material development. We describe the criteria that optical polymers need to meet in order to be viable for commercial deployment. We review the state of the art in polymeric integrated optical components including switches, attenuators, filters, polarization controllers, modulators, lasers, amplifiers, and detectors. We further emphasize the practicality aspect by conveying which technologies have been productized successfully, which ones are ready for commercial introduction, and which ones are still under development in research laboratories.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Wireless communications are rapidly becoming the means of data and information transfer for a broad range of applications. As wireless communication applications continue to expand, the information transfer rates are evolving toward the Gigabit per second data rate and, for some applications, there is even a need for terabit per second data rate transfer in the wireless network. In addition, wireless terminals often require instantaneous switching and communications between network members. For most applications directional antennas are needed to support the high data throughput requirements, and phased array antennas are the only high gain, directional antennas that can be rapidly switched to provide instantaneous communications among network members scattered geographically. Wireless terminal equipment is currently designed to operate in the 1 to 60 GHz frequency range and, traditionally, these equipment are designed with RF hardware. More recently, optics technology has been demonstrated to play an important role in RF systems as the True-Time-Delay in the phased array antenna, and, for some systems operating at high data rates, optical interconnects at the baseband level require E-O and O-E conversions. This paper discusses the considerations in using optics technology in the design of the wireless terminal network including optical signal processing, optical backplanes, optical networking, optical interconnects, and optical components. This paper also describes the architecture of an RF wireless communications network using a range of optical technologies.

Optical code division multiple access (O-CDMA) uses very narrow transmission pulses and is thus susceptible to fiber optic link impairments. When the O-CDMA is implemented as wavelength/time (W/T) matrices which use wavelength division multiplexing (WDM) sources such as multi-frequency laser transmitters, the susceptibility may be higher due to: (a) the large bandwidth utilized and (b) the requirement that the various wavelength components of the codes be synchronized at the point of the data modulation and encoding as well as after (optical) correlation. A computer simulation based on the nonlinear Schroedinger equation (developed to study optical networking on the National Transparent Optical Network (NTON)) was modified to characterize the impairments on the propagation and decoding of W/T matrix codes over a link of the NTON. Three critical impairments were identified by the simulation: group velocity dispersion (GVD); the flatness of the optical amplifier gain; and the slope of the GVD. Subsequently, experiments were carried out on the NTON link to verify and refine the simulations as well as to suggest improvements in the W/T matrix signal processing design. The NTON link measurements quantified the O-CDMA dispersion compensation requirements. Dispersion compensation management is essential to assure the performance of W/T matrix codes.