Showing papers presented at "International Conference on Transparent Optical Networks in 2003"

Phononic crystals

Abstract: The phononic crystals properties are compared with those of semiconductors and photonic crystals. A photonic band gap appears when all channels of phonons propagation are suppressed. In order to achieve this requirement, the material parameters must fulfill certain conditions. In a nanostructured material, besides the acoustic phonons, localized optic-like, "mixed " and "Bragg" induced modes propagate.

Optical add/drop multiplexers and optical cross-connects for wavelength routed networks

Abstract: WDM optical communication systems are evolving from simple point-to-point links to complex network architectures. In wavelength routed networks switching is performed through optical add/drop multiplexer (OADM) and optical cross-connect (OXC) nodes. These nodes provide provisioning capabilities as well as protection and restoration at the optical layer. Routing and management of the traffic demands are applied through the generalised multiprotocol label switching (GMPLS) a control plane offering intelligence at the optical layer. A central subject of debate has been the comparison of optical and electrical switching technologies, however transparent solutions offer attractive features associated with reduced unnecessary optoelectronic conversions supporting transparent networks with reduced capital and operational cost. A number of different OADM and OXC architectures based on various technologies have been proposed to date. A detailed discussion on the different architecture and technology choices supporting a variety of features are given and specific design and implementation examples are analysed. The impact of impairments introduced by transparent elements present in the network, such as OADM and/or optical switches, is discussed and optimised solutions introducing low penalties proposed. In addition, the use of novel modulation formats improving the concatenation performance of such elements is covered.

Plastic electronics

Abstract: Summary form only given. Plastic electronics is a rapidly growing activity owing to the big economic impact expected from the new generation of organic electroluminescent screens. We have specialized in Angers into some aspects of the technology, which promises great technological development although still demanding fundamental and technological research: plastic solar cells, organic lasers, field effect transistors. The analysis of the problem requires in each situation a multiscale approach. I will illustrate in detail this multiscale approach in the case of plastic solar cells in which each basic process appears to be associated with a particular scale which is almost the range of the interaction: absorption, exciton diffusion, charge transfer, charge transport, electric properties. This approach permits to define the limits of the process and also the direction in which we can expect improvement of the devices. Our today's devices reach 1% solar power efficiency in bilayer structures, 2% efficiency with co-deposited molecules and 3% efficiency with polymer blends.

Security model and authentication protocol in EPON-based optical access network

Abstract: An EPON (Ethernet passive optical network), which is progressing to standardization in IEEE 802.3ah, consists of an OLT (optical line termination) and multiple ONUs (optical network units) using passive optical components. This network is susceptible to various security threats, such as eavesdropping, masquerading, denial of service, and so on. We propose a security model and a security protocol to support authentication in an EPON based optical access network. We analyze security threats and security models in the EPON reference model. After considering these models, we propose that an encryption layer is placed at the RS layer. The paper proposes an authentication protocol based on public key exchange and a key establishment protocol. User authentication and ONU authentication are performed separately to give efficient key management and a strong authentication service.

Sensitivity of holey fiber based sensors

Abstract: We analyze the mechanisms contributing to the overall sensitivity of optical sensors based on holey fibers. For this purpose we investigate the shift of the Bragg-matched wavelength in a sensor with a Bragg grating as well as the change of birefringence in a polarimetric sensor. For the sake of simplicity we concentrate on the response of the sensor to temperature. We show that the change of refractive index of silica is not always the dominating source of the sensor's response.

Coupling, scattering, and perturbation theory: Semi-analytical analyses of photonic-crystal waveguides

Abstract: Although brute-force simulations of Maxwell's equations, such as FDTD methods, have enjoyed wide success in modelling photonic-crystal systems, they are not ideally suited for the study of weak perturbations, such as surface roughness or gradual waveguide transitions, where a high resolution and/or large computational cells are required. Instead, we suggest that these important problems are ideally suited for semi-analytical methods, which employ perturbative corrections (typically only needing the lowest order) to the exactly understood perfect waveguide. However, semi-analytical methods developed for the study of conventional waveguides require modification for high index-contrast, strongly periodic photonic crystals, and we have developed corrected forms of coupled-wave theory, perturbation theory, and the volume-current method for this situation. In this paper, we survey these new developments and describe the most significant results for adiabatic waveguide transitions and disorder losses. We present design rules and scaling laws for adiabatic transitions. In the case of disorder, we show both analytically and numerically that photonic crystals can suppress radiation loss without any corresponding increase in reflection, compared to a conventional strip waveguide with the same modal area, group velocity, and disorder strength.

Securing all-optical networks

Abstract: All-optical networks (AONs) are a relatively new technology for high data-rate communications. They contain only optical components and are intrinsically different from optical networks currently being used. More specifically, AONs provide transparent features that allow routing and data switching without necessitating the interpretation or regression of signals within the network. Consequently, AON components and architectures bring forth a set of new challenges in network security. The paper presents an overview of security issues in AONs and proposes the design criteria for network management in AONs. In addition, there is a discussion concerning the implementation of such a system within the authors' research group.

Laser diode linewidth measurements

Abstract: A spectrum of laser diode radiation forms a qualitative criterion of the laser diode applicability as a fiber telecommunications source. Hence, there is need to measure/estimate its spectral linewidth. Having a few different commercial laser sources at the range of third telecommunication window we developed laser linewidth measurements. The presentation of our current experimental diagnostic systems based on heterodyne methods is given.

Recent progress on S-band fiber amplifiers

Abstract: The internet boom in the 1990's led to an exponential increase of the bandwidth demands on optical long-haul transmission links and the introduction of WDM and DWDM systems. However, the gain bandwidth of usual fiber amplifiers is limited to a maximum of 80 nm in the C- and L-band. Todays optical senders and receivers are limited to a spectral efficiency of not more than 1 bit/s/Hz which results in a total capacity of about 10 Tbit/s in the C- and L-bands. Meanwhile the crash of the telecom market damped the bandwidth growth somewhat, but it is still an important task to work on solutions for transmission systems at extremely high bitrates beyond 10 Tbit/s. One of these solutions is the use of larger parts of the low attenuation window of the transmission fibers. It seems to be consensus that the first step towards this direction will be the S- and S/sup +/-band at 1450-1530 nm. Here we will give an overview of the current status and new developments in the field of S-band fiber amplifier technologies. As usual, the term S-band will be used for Sand S/sup +/-band in this work.

ORION: a novel hybrid network concept: overspill routing in optical networks

Abstract: As more and more packets needs to be handled in the network, wavelength switched optical networks reduce the number of packets that need to be handled. However, this results in inefficient wavelength usage. Furthermore, it can only cope with traffic variations on a larger time scale. On the other hand, optical packet/burst switching (OPS/OBS) can cope better with traffic variations, but there is the contention resolution problem and the large number of handled packets. Is it really necessary to make this choice between black and white, or is it possible for these two to meet in the (gray) middle? We propose a novel networking architecture, trying to find a working marriage between these two - overspill routing in optical networks (ORION) - a network that is basically wavelength switched, but traffic can spill over in a packet switched modus, which allows a way to cope better with variable traffic profiles.

Optical modulation formats for high-speed DWDM systems

Abstract: State-of-the-art of high-capacity optical modulation formats used in high-speed DWDM transmission systems are presented. Simulations of 320 km transmission of DWDM signal show that DQPSK modulation is superior to CS-RZ (carrier-suppressed return-to-zero) and duobinary phase modulation with respect to signal degradation due to Kerr nonlinearities.

An adaptive service differentiation algorithm for optical packet switched networks

Abstract: The paper presents a novel adaptive service differentiation algorithm for optical packet switched (OPS) networks. Previous research has aimed at presenting algorithms that achieve service differentiation in OPS networks by utilizing the wavelength domain. However, simulations show that these algorithms result in fluctuating packet loss rate as the system load is varied. The adaptive algorithm proposed here measures the packet loss rate for high priority traffic over a time interval and adjusts the number of wavelength converters reserved for high priority traffic accordingly in order to achieve a constant packet loss rate. However, due to the self-similarity of Internet traffic, special considerations must be taken into account in order to avoid oscillations in the number of wavelength converters reserved for high priority traffic.

Semiconductor devices for all-optical regeneration

Abstract: We review different implementations of semiconductor devices for all-optical regeneration. A general model is presented for all-optical regeneration in fiber links, taking into consideration the trade-off between non-linearity and noise. Furthermore we discuss a novel regenerator type, based on saturable gain and absorption in a waveguide structure.

Some open issues in the optical networks control plane

Abstract: The growth of bandwidth demand for data traffic drives the evolution of current transport networks towards the introduction of the automatic switched optical network (ASON). Introducing automatic switching capabilities in optical networks means designing and implementing control functionalities. Such functionalities are hosted at the network control plane, and mainly consist of providing signalling and routing mechanisms distributed throughout the network. The paper addresses some issues still under discussion on the definition of a suitable control plane for optical core networks. Specifically, we deal with the routing protocol, which defines the distribution of topology information, the path selection and the association of nodes in a network; and with the routing mechanism, which allows selection of the path according to the attributes of connection requests and the available resources in the network. We also deal with the traffic engineering strategies used to optimise the use of these resources and give a quick view of future trends in optical networks.

Fabrication and characterization of photonic crystal slab waveguides and application to ultra-fast all-optical switching devices

Abstract: Current status of two-dimensional photonic crystal (2D-PC) slab waveguide technologies and application to a photonic integrated circuit (PIC) has been reviewed. The emphasis is placed on our recent advancement on theoretical design, fabrication and characterization of the 2D-PC-based defect-waveguides such as straight, 60/spl deg/-bend, coupled-cavity waveguides and directional coupler, essential for the PIC application. A research scenario and technical key issues for application to an ultra-fast and ultra-small symmetrical Mach-Zehnder (SMZ)-type all-optical switch are also addressed.

Organic optoelectronics

Abstract: Organic materials offer great potential for a wide range of applications in both linear (e.g., organic light-emitting diodes, photodetectors, polarizers, polarized light-emitting sources, birefringent optical memories) and nonlinear optics (e.g., waveguide second-harmonic generation, electro-optic modulators, directional couplers). Among the different accessible geometries, planar microcavities are interesting structures in which to study the optical properties of organic materials. Planar microcavities are one-dimensional photonic structures which result in strong modifications; of the spectral and spatial distribution of photon fields, which in turn give rise to major changes in light-matter interactions. The strong coupling between excitons and photons is one of the manifestations of such modifications and results in the formation of coupled-mode states, two-dimensional exciton polaritons. Organic molecular compounds are very attractive materials for opto-electronics applications.

The ring-based resonant router

Abstract: The resonant router (ReR) is an integrated optics crossbar matrix based on ring resonators. Depending on the characteristics of the rings the ReR can operate as cross-connect (X-ReR) or as wavelength router (/spl lambda/-ReR). The analysis of the device, the spectral characteristics and the impact on a high bit rate signal are presented and discussed both on a theoretical and experimental basis. The ReR can add flexibility and extend the capabilities of a node of a transparent optical network.

Nonlinear optics in photonic crystals

Abstract: Photonic crystals provide novel concepts and opportunities for molding and controlling the flow of light. In this paper I will review some of our experimental efforts to utilize the distinctive properties of photonic crystals to enhance nonlinear optical processes or use the nonlinear optical processes to tune the photonic crystal properties. Examples related to second harmonic generation, Kerr nonlinearities and plasma switching will be given for 1-D and 2-D systems.

Super-channel architectures for in-service capacity expansion of CWDM/DWDM systems

Abstract: Super-channel architectures enable many narrow spaced wavelengths to be nested into one CWDM (coarse WDM) or DWDM channel at the rates up to 10 Gb/s. This gives a low-cost, growth on demand, capacity upgrades as an overlay to existing CWDM/DWDM systems.

Performance analysis of the simple prioritized buffering algorithm in optical packet switch for DiffServ assured forwarding

Abstract: The paper addresses the problem of providing QoS management for an optical packet switch. In particular, we propose the simple prioritized buffering algorithm (SPBA) for prioritized buffer management, which aims to guarantee different packet loss probabilities to different packet streams. In contrast to other solutions, SPBA does not need any resource reservation or threshold dropping, but only makes use of priority scheduling. A theoretical model of SPBA with K classes of service applied to an optical packet switch with fiber-delay line buffers and tunable wavelength converters is presented. The analytical model is verified by simulations.

Trends of optical networking technologies

Abstract: Optical layer networking, such as wavelength routing, switching and restoration/protection in an optical layer is a major trend of future optical networks to achieve highly scaleable and survivable optical backbone networks. In this paper, optical layer networking using MEMS-based optical switches both for ring and mesh networks is discussed. Fast protection time of about 20 ms for IP layer has been achieved by the optical layer protection with the optical network protection equipment using a 2D-MEMS in a 500 km bidirectional wavelength path switching ring network. The obtained switching time was comparable to that of optical cross connect using electrical switching fabrics. Regarding the intelligent optical network using the generalized multi-protocol label switching (GMPLS) protocols, interworking between a photonic cross connect based on a 3D-MEMS and an IP/MPLS router has been confirmed. Fast wavelength path provisioning as well as proper path restoration has been also achieved with the GMPLS testbed including three photonic cross connect nodes and 1000 km bidirectional transmission line. Finally, the feasibility of the transparent all-optical network has been demonstrated with the GMPLS testbed.

Coding gain of basic FEC block-codes in the presence of ASE noise

Abstract: We investigate the performance of Hamming and BCH block codes for the case of ASE (amplified spontaneous emission) noise as the dominating impairment. Numerical results obtained by Monte-Carlo simulations show excellent agreement with theoretical considerations.

Supercontinuum generation in a photonic crystal fibre using picosecond pulses at 1550 nm

Abstract: Supercontinuum (SC) generation is demonstrated in a photonic crystal fibre (PCF) at 1550 nm with pulse widths of 0.3 to 2.5 ps. Subsequent band-pass filtering of the generated SC spectrum enables the realisation of an optical clock frequency translator continuously tunable up to the L-band.

Modeling of highly birefringent photonic fiber with rectangular air holes in square lattice

Abstract: High birefringence of the order of 2*10/sup -3/ has been predicted in silicate microstructured fibers with rectangular air capillaries ordered in a square grid. With sensor applications in mind, the rectangular geometry was chosen to increase the photonic crystal fiber sensitivity to deformation. The numerical simulations were made with full-vector mode solver using the biorthonormal basis method and confirmed using 3D FDTD technique software.

Subcarrier multiplexed optical label swapping based on subcarrier multiplexing: a network paradigm for the implementation of optical Internet

Abstract: We introduce and review the main features of subcarrier multiplexed label swapping techniques as a supporting technology for the implementation of the optical Internet. The efforts that are currently being made under the framework of the EU funded IST-LABELS project are also described.

Three-dimensional comprehensive self-consistent simulation of a room-temperature continuous-wave operation of GaAs-based 1.3-/spl mu/m quantum-dot (InGa)As/GaAs vertical-cavity surface-emitting lasers

Abstract: The comprehensive self-consistent three-dimensional optical-electrical-gain-thermal self-consistent model of the oxide-confined long-wavelength 1.3-/spl mu/m (InGa)As/GaAs quantum-dot vertical-cavity surface-emitting laser is presented. The model has been used to modify and optimise VCSEL structure to reduce its anticipated room-temperature continuous-wave lasing threshold. Some essential guidelines for designers of laser sources for the second-generation 1.3-/spl mu/m communication systems are given.

Survivability of wavelength-routed optical burst-switched networks with guaranteed IP services

Abstract: The paper discusses the problem of ensuring QoS performance in wavelength-routed optical burst-switched (WR-OBS) networks under single link failures. The provision of IP services run over high-speed optical backbones should be resilient to faults in the network, hence the importance of a WR-OBS survivability investigation. A failure-compensating scheduling, residing in the WR-OBS control node, is proposed and analysed in terms of burst blocking probability and burst scheduling delay increment. The WR-OBS wavelength over-provisioning for maintaining guaranteed QoS is also studied as a function of network physical connectivity.

Design of automatically switched optical networks

Abstract: Due to the advances in optical component technology and the desired integration of the technological network layers, more significant professional attention is being paid to the concept and the emerging technology of automatically switched optical networks (ASON). The intelligent switching capabilities enable more dynamic networking, which may change the network characteristics significantly. The study of these changing characteristics is required in order to provide a firm basis for strategic network development decisions. After a brief overview of the ASON technology, the paper illustrates the potential advantages and drawbacks due to the dynamic behavior of the optical network. The analysis of numerical results from small network examples helps to highlight the main networking features of dynamic provisioning of optical channels. Based on the results of network simulations, a comparison of semi-permanent and switched connection based services is performed, taking into account different source activities. Finally, a quantitative analysis is given of the expected network resource savings originating from the statistical gains of automatic switching.

GMPLS extensions for supporting advanced optical networking technologies

Abstract: In response to the need for higher flexibility in optical networks, a generalised multiprotocol label switching (GMPLS) protocol suite is currently under standardisation. However, in these standards a label switched path (LSP) hierarchy is defined that only considers circuit-switched optical networks. The paper aims at broadening the scope of this hierarchy to more advanced optical networking technologies.

Numerical methods for fiber Bragg gratings

Abstract: In this work several numerical methods, usually used to obtain the reflectivity spectrum of Bragg gratings, are studied and general conditions required for each method are analyzed and evidenced. The results are validated by comparison with a closed form analytical solution. For gratings where the solution is not evident, Rouard's method was used as the reference solution.