1,973 research outputs found

    European Union Acts project MIDAS: objectives and progress to date

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    Introduction to the ACTS program: Advanced Communications and Technology and Services, known simply as ACTS, is one of the specific programmes of the "Fourth Framework Programme of European Community activities in the field of research and technological development and demonstration (1994-1998)". It provides the main focus of the European Unions research effort to accelerate deployment of advanced communications infrastructures and services, and is complemented by extensive European research in the areas of information technology and telematics. The stated objectives of ACTS are to "develop advanced communication systems and services for economic development and social cohesion within Europe, taking account of the rapid evolution of technologies, the changing regulatory situation and opportunities for development of advanced transeuropean networks and services". Within ACTS, the emphasis of the work has shifted from the exploration of fundamental concepts and detailed system engineering, as it had been in earlier programs such as RACE (Research and development in Advanced Communication technologies for Europe), to issues relating to implementation of advanced systems and generic services, and applications which demonstrate the potential use of advanced communications in Europe. A key feature of the ACTS program is that the research be undertaken in the context of real-world trials. Work within the program is divided into six technical areas: Interactive digital multimedia services, photonic technologies, high speed networking, mobility and personal communication networks, intelligence in networks and services and quality, safety and security of communication systems and services. The total EU budget for the ACTS program is approximately 670 MECU, covering around 160 projects, with over 1000 individual organisations participating within the program, thereby illustrating the scale of the activities. MIDAS is one of five projects in the technical area of photonic technologies concerned with high speed transmission, the others being ESTHER, UPGRADE, HIGHWAY and SPEED, each concerned with various aspects or approaches to the development of 40 GBit/s transmission systems within the European arena. A full list of project descriptions and objectives, as well as those of the ACTS program as a whole, are to be found in Ref [1]. The MIDAS consortium consists of the following organisations: Chalmers University of Technology (Sweden), CSELT (Italy), Thomson LCR (France), United Monolithic Semiconductor (France), Telia (Sweden), Kings College London (UK), University of Athens (Greece), ORC University of Southampton (UK). The project started in September 1995 and is currently scheduled to finish in September 1998

    Fiber laser systems shine brightly

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    Describes the advancements in active fiber laser systems. Outline of cladding pumping technique for enhanced power scaling; Improved energies and peak powers; Extended wavelength range; Frequency doubling with fiber sources

    Slowing of pulses to c/10 with subwatt power levels and low latency using Brillouin amplification in a bismuth-oxide optical fiber

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    We report the generation of slow light using Brillouin amplification in a short length of highly nonlinear bismuth-oxide fiber. By using just 2m of fiber, we demonstrate a five-fold reduction in group velocity for ~200ns pulses, which we believe to be a record for a slow-light propagation in an optical fiber. Moreover, by virtue of the high nonlinearity per unit length of this fiber, we achieve this at a very modest pump power level of just ~400mW and with a low inherent device latency of 14ns. These results highlight both the merits and practicality of using high nonlinearity nonsilica fibers for slow-light devices

    High quality 5ps pulse generation at 10 Gbit/s using a fibre Bragg grating compensated gain-switched laser diode

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    A fibre Bragg grating is designed to spectrally filter and perfectly compensate the chirped pulses from a gain-switched laser diode. This design is based on the exact characterisation of the intensity and phase profiles using an electro-optic pulse characterisation technique. This results in a compact pulse source that should produce high quality 5 ps duration pulses with a 50 dB pedestal suppression

    SEM characterization of mm-long nanowires

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    The fabrication of optical fibre nanowires has recently attracted much attention [1-5]. Nanowires longer than 110mm [2] and with diameters smaller than 20 nm [5] have now been fabricated using a top-down approach. Because of the extraordinarily large ratio between length and diameter (>100000), the characterization of optical fibre nanowires requires instrumentation capable of measuring lengths over a range spanning more than five orders of magnitude. In our experiments dimensional characterization along the nanowire has been performed using an SEM and calibrated references. The samples are first attached to conductive carbon pads to avoid electrostatic build-up. Charging makes accurate metrology difficult because the electron beam can be deflected by the induced electric field on the sample. Fig. 1 illustrates a nanowire with a radius r=30nm wrapped around a microfibre with r=2µm. Variations in radius of another nanowire along its length are shown in fig. 2

    All-optical pulse reshaping and retiming systems incorporating pulse shaping fiber Bragg grating

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    This paper demonstrates two optical pulse retiming and reshaping systems incorporating superstructured fiber Bragg gratings (SSFBGs) as pulse shaping elements. A rectangular switching window is implemented to avoid conversion of the timing jitter on the original data pulses into pulse amplitude noise at the output of a nonlinear optical switch. In a first configuration, the rectangular pulse generator is used at the (low power) data input to a nonlinear optical loop mirror (NOLM) to perform retiming of an incident noisy data signal using a clean local clock signal to control the switch. In a second configuration, the authors further amplify the data signal and use it to switch a (low power) clean local clock signal. The S-shaped nonlinear characteristic of the NOLM results in this instance in a reduction of both timing and amplitude jitter on the data signal. The underlying technologies required for the implementation of this technique are such that an upgrade of the scheme for the regeneration of ultrahigh bit rate signals at data rates in excess of 320 Gb/s should be achievable

    Detailed comparison of injection-seeded and self-seeded performance of a 1060nm gain-switched Fabry-Perot laser diode

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    We investigate and compare the performance of a gain-switched picosecond Fabry-Perot laser diode operated at 1.06 µm under both injection- and self-seeded conditions. Our experiments show that comparable performance can be obtained for both modes of operation, with the self-seeding arrangement offering overall benefits in terms of reduced system complexity and cost, providing the associated quantization of available pulse repetition rate can be tolerated

    A microstructured wavefront filter for the Darwin nulling interferometer

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    The European Space Agency's space-based Darwin mission aims to directly detect extrasolar Earth-like planets using nulling interferometry. However, in order to accomplish this using current optical technology, the interferometer input beams must be filtered to remove local wavefront errors. Although short lengths of single-mode fibre are ideal wavefront filters, Darwin's operating wavelength range of 4 - 20µm presents real challenges for optical fibre technology. In addition to the fact that step-index fibres only offer acceptable coupling efficiency over about one octave of optical bandwidth, very few suitable materials are transparent within this wavelength range. Microstructured optical fibres offer two unique properties that hold great promise for this application; they can be made from a single-material and offer endlessly single-mode guidance. Here we explore the advantages of using a microstructured fibre as a broadband wavefront filter for 4 - 20 µm

    Microstructured cladding elements to enhance performance and flexibility of large mode area leakage channel fibers

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    Large mode area fibers are imperative for scaling up the average power of fiber lasers. Single-mode behavior and low FM loss are the crucial functionalities for these fibers. However, for key applications such as picosecond pulsed lasers, the device length needs to at least a few meters. This makes a certain degree of bend tolerance a prerequisite in the fiber design. While rod-type PCFs have been very successful in offering large mode areas, their rigid configuration limits their application domain. Alternatively, leakage channel fibers (LCFs) have shown a great potential for offering substantial bend tolerance along with large mode areas. However, the proposed use of Fluorine-doped rods in the all-solid version limits their practical design space. Here, we propose a novel design concept to attain single-material, large mode area fibers (mode area >~ 1000µm2) with effectively single mode operation coupled with bending characteristics comparable to all-solid LCFs and greater design flexibility and easier splicing that is comparable to rod-type PCFs

    High performance architecture design for large scale fibre-optic sensor arrays using distributed EDFAs and hybrid TDM/DWDM

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    A distributed amplified dense wavelength division multiplexing (DWDM) array architecture is presented for interferometric fibre optic sensor array systems. This architecture employs a distributed erbium doped fibre amplifier (EDFA) scheme to decrease the array insertion loss, and employs time division multiplexing (TDM) at each wavelength to increase the number of sensors that can be supported. The first experimental demonstration of this system is reported including results which show the potential for multiplexing and interrogating up to 4096 sensors using a single telemetry fibre pair with good system performance. The number can be increased to 8192 by using dual pump sources
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