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The fiber-optic components described in earlier chapters are assembled into systems to provide communication services. This chapter takes a closer look at basic system concepts that were introduced in Chapter 3. To understand telecommunications systems and the emerging optical network, you need to learn both the specifics of how fiber-optic systems transmit signals and the tasks these systems perform. This chapter is the first of several that will teach you about optical networks and the services they provide.

Fiber-optic systems are no longer passive pipes that merely carry optical signals from point to point. Signals may be modulated in intensity, switched between fibers, shifted in wavelength, and modified in other ways. The potential of “optical networking” was over-promoted during the telecommunications bubble, but the need to operate on signals is growing with the volume of traffic and the size of the global telecommunications network. The devices that perform these operations on signals are called active components. You have already learned about several types of active components. Light sources, transmitters, receivers, optical amplifiers, and wavelength converters are all active components. In this chapter you’ll learn about optical modulators, optical switches, and other components that dynamically affect optical signals.

To date, undersea optical communication has been driven by wide-beam LED systems. Directional laser systems have several advantages | increased range, increased data rate, and better performance in solar background | but require a precise tracking system to maintain laser pointing through vehicle motion. We have demonstrated an underwater laser communication system with a bi-direction, all-optical pointing, acquisition, and tracking system. Laser communication terminals were mounted on two remotely operated vehicles that were piloted to the ends of a pool (a separation of 20 m), coarsely aligned to within about 10 degrees, and then set to autonomously acquire and track each other. Acquisitions occurred within a few seconds, and the link never broke during maneuvers. To our knowledge this is the first demonstration of a functional undersea laser tracking system between mobile vehicles. The demonstrated precision and robustness can enable 1+ Gbps data links between independent, moving vehicles, over several 100 meters in clear ocean water. Additionally, this approach provides precise (cm- class) relative positioning between the communicating parties, enabling relative position, navigation, and timing (PNT) distribution between independent vehicles. This technology is a crucial enabler of undersea wireless optical networking for manned and unmanned vehicles.

Internet of Things (IoT) is a network of interrelated physical objects that can collect and exchange data with one another through embedded electronics, software, sensors, over the Internet. It extends Internet connectivity beyond traditional networking devices to a diverse range of physical devices and everyday things that utilize embedded technologies to communicate and interact with the external environment. The IoT brings automation and efficiency improvement to everyday life, business, and society. Therefore IoT applications and market are growing rapidly. Contrary to common belief that IoT is only related to wireless technology, optical technologies actually play important roles in the growth of IoT and contribute to its advancement. Firstly, fiber optics provides the backbone for transporting large amount of data generated by IoT network in the core , metro and access networks, and in building or in the physical object. Secondly, optical switching technologies, including all-optical switching and hybrid optical-electrical switching, enable fast and high bandwidth routing in IoT data processing center. Thirdly, optical sensing and imaging delivers comprehensive information of multiple physical phenomena through monitoring various optical properties such as intensity, phase, wavelength, frequency, polarization, and spectral distribution. In particular, fiber optic sensor has the advantages of high sensitivity, low latency, and long distributed sensing range. It is also immune to electromagnetic interference, and can be implemented in harsh environment. In this paper, the architecture of IoT is described, and the optical technologies and their applications in the IoT networks are discussed with practical examples.

Optical networking adds another dimension to the concepts of system design you learned in Chapter 21 for the simple case of a single optical channel per fiber. This chapter covers systems that transmit two or more optical channels per fiber, where signals are managed by wavelength or optical channel. The extra optical channels increase the complexity of system design, and the number of factors that must be considered. This chapter opens with a review of optical networking concepts. It then explains how optical channels are packed together, contrasting wavelength-division and time-division multiplexing, and dense and coarse channel spacing. Then it covers the properties of optical fibers and optical amplifiers that affect optical networking design. Finally it covers optical switching and channel management, including the importance of wavelength conversion. Optical network design is still a young field, so we will not cover it in as much detail as we did single-channel design in Chapter 21.

Now that you have learned the ideas behind fiber-optic communication systems, it’s time to look at how they are designed. Design is a big topic, so it is split into two chapters. This chapter covers design of single-channel systems to meet loss and bandwidt requirements. Chapter 22 covers design considerations for wavelength-division multiplexing and optical networking. Loss budgets and transmission capacity, or bandwidth, are crucial in both single- and multichannel systems, but the basic principles are the same for both. You calculate loss budget to be sure that enough signal reaches the receiver to give adequate performance. Likewise, you must calculate pulse dispersion, or bandwidth, to be sure the system can transmit signals at the proper speed. Some simple guidelines will give you rough assessments. In the real world, you also must consider cost-effectiveness and make trade-offs among various approaches to find the best performance at the most reasonable cost. Single-channel design techniques can be applied to each channel in a multiwavelength system. These two chapters will not prepare you for heavy-duty system design. However, they will give you the basic understanding of design concepts and technical trade-offs you need to assess fiber-optic systems.

In this paper, a new conclusion based on rotating parabolic model and a different scheme of laser communication networking antenna system has been put forward in the paper. Based on rotating parabolic antenna, a new theory of the optical properties have been deduced, which can realize larger dynamic, duplex, networking communications among multiple platforms in 360° azimuth and pitch range. Meanwhile, depending on the operation mode of the system, multiple mathematical optimization models have been established. Tracking communication range, emission energy efficiency and receiving energy efficiency have been analyzed and optimized. Relationship among opening up and low apertures, the lens unit aperture, focal length of lens unit as well as rotating parabolic focal length have been analyzed. Tracking pitching range and emission energy utilization has carried on the theoretical derivation and optimization and networking platform link between energy receiver and transmitter has been analyzed. Taking some parameters of this new system into calculation, optimized results can be utilized with MATLAB software for its application and system of communication engineering. The rotating parabolic internal can form a hollow structure, which is utilized for miniaturization, light-weighted design and realize duplex communication in a wide range and distance. Circular orbit guidance is the modern way used in dynamic tracking system. The new theory and optical antenna system has widespread applications value as well.

Optical networking is evolving from classical service-provider base data-center centric (DCC) internetworking environment with massive capacity, hence demanding novel optical switching and interconnecting technologies. The traditional telecom networks are under a flattening transformation to meet challenges from DCC networks for massive capacity serving in order of multi-Pb/s. We present proposed distributed and concentric data center based networks and the essential optical interconnection technologies, from the photonic kernels to electronic and optoelectronic server clusters, in both passive and active structures. Optical switching devices and integrated matrices are proposed composing of tunable (bandwidth and center wavelength) optical filters and switches as well as resonant microring modulators (μRM)(switching and spectral demux/mux) for multi-wavelength flexible-bandwidth optical channels of aggregate capacity reaching Ebps. The design principles and some experimental results are also reported.

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 overall spectral efficiency in optical transmission systems needs to be enhanced by employment of advanced modulation, multiplexing, 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 discuss multidimensional modulation, multiplexing, and coding schemes, which are enablers not only of the information capacity increase, but also for the next generation elastic high-speed optical networking and outline possible future directions and application scenario in different networking segments.

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.

Orthogonal Frequency Division Multiplexing (OFDM) has recently been proposed as a modulation technique. For optical networks, because of its good spectral efficiency, flexibility, and tolerance to impairments, optical OFDM is much more flexible compared to traditional WDM systems, enabling elastic bandwidth transmissions, and optical networking is the future trend of development. In OFDM-based optical network the research of blocking rate has very important significance for network assessment. Current research for WDM network is basically based on a fixed bandwidth, in order to accommodate the future business and the fast-changing development of optical network, our study is based on variable bandwidth OFDM-based optical networks. We apply the mathematical analysis and theoretical derivation, based on the existing theory and algorithms, research blocking probability of the variable bandwidth of optical network, and then we will build a model for blocking probability.

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).

Present-day data networks are being challenged by the relentless growth of bandwidth demand. Most of this future growth, however, is not arising from more users with the same application bandwidth demands, but rather from the dramatic increase in bandwidth demand of emerging applications. The compounding of these two trends has set the stage for optical networking technology to make significant contributions in next-generation data network architecture. In this talk, we will explore key research problems of optical network architecture (such as flow switching) that, if properly exploited, will enable significant growth and cost-effective scalability of next-generation data networks.

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).

Quantum communications is an emerging field with many promising applications. Its usefulness and range of applicability in optical fiber will depend strongly on the extent to which quantum channels can be reliably transported over transparent reconfigurable optical networks, rather than being limited to dedicated point-to-point links. This presents a number of challenges, particularly when single-photon quantum and much higher power classical optical signals are combined onto a single physical infrastructure to take advantage of telecom networks built to carry conventional traffic. In this paper, we report on experimental demonstrations of successful quantum key distribution (QKD) in this complex environment, and on measurements of physical-layer impairments, including Raman scattering from classical optical channels, which can limit QKD performance. We then extend the analysis using analytical models incorporating impairments, to investigate QKD performance while multiplexed with conventional data channels at other wavelengths. Finally, we discuss the implications of these results for evaluating the most promising domains of use for QKD in real-world optical networks.

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.

The rapid and aggressive penetration of broadband access services such as fiber to the home (FTTH) has been accelerating the increase in IP traffic volume and new networking technologies are required in order to accommodate future traffic in a cost-effective manner. This paper overviews the advanced IP optical network architecture and technologies for very-large-scale IP backbone networks. These technologies are the key to accommodate the huge volumes of IP traffic expected and control network resources in an effective and dynamic manner. We describe advanced IP optical networking technologies which accommodate multiple service networks using multi-instance technologies, and enable multi-layer traffic engineering using virtual network topology technologies. The migration scenario is described from the existing networks to GMPLS networks; reference is made to the advanced Path Computation Element (PCE) which enables multi-layer traffic engineering and MPLS/GMPLS migration. New network concepts such as Layer 1 Virtual Private Network (L1VPN) and GMPLS interoperability issues, which are being discussed in IETF, are also described.

Multi-Granularity optical switching technology has only recently attracted attention from the optical networking industry for its practical importance in reducing port count, the associated control complexity, and the cost of optical cross-connects (OXC). In this paper, the advantage of MG-OXC comparing to the ordinary OXC is introduced and the Multi-Granularity Optical Switching test-bed based on ASON (Automatically Switching Optical Network) is presented. This test-bed is composed of three different plants, namely the transport plane, the control plane and the management plane. We have analyzed the architecture of MG-OXC and provided the scheme of multi-granularity optical switching node. In the end some experiments have been done. We firstly have done the experiment in the creation and release of optical path. The optical path could be a wavelength path or a waveband path. And the second experiment has been done to test the capacity of the traffic grooming in the multi-granularity optical networks. The last experiment is performed to test the protection and restoration under the conditions of the node failure, the wavelength failure and the waveband failure, etc. Finally the results are reported and they show that the test-bed can achieve the expected functions under the control of the control plane of ASON.

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.

Two important aspects of optical networking are to ensure transmission integrity when connecting optically transparent channels in real time for protection, and the handling of dynamic demand, especially when survivability considerations are added. The prevalent approach for providing protected dynamic lightpath services is signaling intensive, database dependent, and requires on-the-fly cross-connection of standby lightwave channels to form protection paths. With two inter-related new concepts, we address concerns about on-the-fly concatenation of transparent optical channels to form protection paths and improve the scalability, and reduce database dependence and signalling intensity associated with current methods. An extension of the p-cycles concept to end-to-end path protection, in conjunction with the concept of a protected working capacity envelope for dynamic provisioning (which has no per-connection signaling for backup path establishment) yields a highly efficient network architecture in which protection paths are fully pre-cross-connected prior to failure and only the two lightpath end-nodes need to detect path failure and switch the lightpath (or its traffic) into a corresponding pre-planned path-protecting p-cycle.

Spurred by the growth of the internet, Optical Telecommunications bandwidth, experienced unprecedented growth during late 1990's. During this time of great economic expansion, the creation of new enterprises was vast and the expansion of established component, system and services companies was breathtaking. Unfortunately, this positive economic state was short-lived. This period was followed in 2001-2004 by one of the most significant market crashes in history. During those 10 years of economic growth, about $20B in venture capital was invested in the optical telecom industry, most of this investment was lost in recent years. Many start-up industries which experienced unprecedented growth at the end of the 20 th century were lost at the start of the 21 st . (1) During this time many, innovative technologies were born and buried. However, many new capabilities emerged from this period of unrest; one such example is the advent of Optical MEMS (MOEMS). Many academics and corporate laboratories pursued the development of MOEMS during the economic boom and, in the author's view; MOEMS surfaced as a powerful and versatile tool set that has proved invaluable and in the last few years during economic downturn, stood the test of time. In the Telecommunications industry, for optical switching and wavelength management applications MOEMS has proven to be the technology of choice. (2) Variable Optical Attenuators (VOA), Wavelength Blockers (WB), Dynamic Gain Equalizers (DGE), and most recently Wavelength Selective Switches (WSS) are being used in the numerous recent network deployments. Moreover, agile networks of the future will have MOEMS at every node. This presentation will provide an overview of the history of MOEMS in Telecommunications, discuss its byproducts and offer a window into the future of the technology.

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.

Optical switches are among key devices for implementation of DWDM in optical networks. There are a number of technologies available to realize optical switches, including Micro-Electro-Mechanical System (MEMS) switches, Bubble-Based Waveguide Switches, Liquid Crystal on Silicon (LCOS) Switches, Electro-Optic Switches, and Thermo-Optic Switches. Among these technologies MEMS has received particular attention in recent years, initially using 2 dimensional (2D) switches and later progressing to 3D switches. This paper evaluates Liquid Crystal on Silicon (LCOS) as an alternative to MEMS for implementation of optical switches. The opportunities and challenges for LCOS in optical networking are discussed. Issues related to availability of LCs, switching speeds, voltage requirements, scalability, wavelength range, packaging and crosstalk are considered.

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.

Optical data transmission has undergone a tremendous evolution. Starting with unrepeated point-to-point transmission in the 80s the inventions of wavelength division multiplexing (WDM) and erbium doped fiber amplifiers (EDFAs) have let to an explosion of system capacity as well as of system reach. After the steep downturn of recent years network operators have now regained the strength to upgrade their networks and to implement new services. This paper will review current and upcoming technologies in the long haul (LH) and ultra long haul (ULH) data transmission. It will further discuss the future evolution of transparent optical networks towards dynamically routed meshed optical networks with respect to operator’s technical operational and economical requirements. Upgradeability turns out as a key issue as it on the one hand side facilitates low front investments for network providers and on the other hand side enables organic and flexible network growth.

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.