FIBER OPTICS

Author: DÍAZ HERRERA NATALIA.
Year: 2004.
University: COMPLUTENSE DE MADRID [www.ucm.es].
Place of defense: FACULTAD DE CIENCIAS FÍSICAS.
Place of preparation: FACULTAD DE CIENCIAS FÍSICAS.

Summary: This work has incorporated the technology of fiber-optic sensors to the identification and control automátíco situ physical parameters of the aquatic environment. Specifically, it has developed and made several point fiber-optic sensors for the simultaneous determination of the degree of salínidad and water temperature, applicable to any environment and able to function independently based on the different physical effects of the sensors commercial. The sensors manufactured based on fiber estrechadas by fusíón and stretching (tapers), were designed to exploit the different qualities of these fibers estrechadas to on the one hand, to characterize the behavior of tapers on the basis of those qualities, and on the other next, check for the wide range of possibilities offered by these fibers for use as sensors. It has characterized the behavior of fibers estrechadas collar uniform respect to its two most important characteristics: sensitivity to changes in the refractive index and the strong external dependence geometry taper, by choosing appropriate transducers that enhance these effects with the purpose of measuring the temperature and variations in the refractive index. It has been tested an initial proposal for temperature sensor consisting of the deposition of a material termocrómíco, lofina on a fiber narrower neck uníforme since this material is hídrófobo and changes its absortancia with temperature. It has been tested a second proposal temperature sensor, which takes advantage of the high sensitivity to changes in the curvature of the tapered fiber, which consists of setting a uniform taper neck on the inside of a cylinder capillary. It has also tested a proposed sensor refractive index, which exploits the sensitivity showing fiber tapered to changes in the refractive index of the external environment, based on the resonance of plasmones surface due to the deposit of an asymmetric double coating (metal - dielectric) on a fiber tapered neck uniform. Also, there have been campaigns field with the optical fiber sensor for determining the degree of salinity situ developed in the past by the research group, and has successfully demonstrated its use in measuring actual conditions in the field. The designs of the proposed sensors are simple and small, with a view to enabling tools are portable, easy to handle and suitable for use in situ different scenarios, including high seas, coastal and river basin management platform.

Author: MATEO RODRÍGUEZ EDUARDO FABÍA.
Year: 2004.
University: SANTIAGO DE COMPOSTELA [www.usc.es].
Place of defense: ESCUOLA UNIVERSITARIA DE ÓPTICA Y OPTOMETRÍA.
Place of preparation: ESCUELA UNIVERSITARIA DE ÓPTICA Y OPTOMETRÍA.

Summary: The investigative work reflected in this report, within the framework devoted to the theory and design of integrated nonlinear optical devices. Destined to operate in a fully optical, its operations will be geared to the achievement of key operations within the communications and computing totally optics. Based on the study of a new type of integrated non-linear guides called CKS (Coefficient Kerr Phased), based on the gradualness of the index emotional as well as distribution inhomogenea of non-linearity, new schemes have been studied spreading copropagación and contrapopagación ( through a new variational formulation of the problem refractivo-disipativo) highly specific to fully optical devices, under the influence of such inhomogeneidad and cash rate gradually over the spread of non-linear optical field. Moreover, it has been proposed combining mechanism automodulación and cross modulation amplitude in non-linear guides CKG with the mechanism of modulation of intensity by the so-called Link Modal Cross (AMT), as confirming an overall strategy and efficient for projecting and designing integrated devices compatible with fiber optics, and ultra insensitive to phase and frequency. Ultimately, the study of a new type of integrated guides, a new variational formulation of the problem of propagation disipativo, and finally, a new mechanism optical intensity modulation nonlinear modal cross coupling, has been achieving devices biestables logical and routing of high strategic value in the development of transmission systems and optical processing completely.

Author: SPADARO SALVATORE.
Year: 2004.
University: POLITÉCNICA DE CATALUÑA [www.upc.edu].
Place of defense: EDIFICI VÈRTEX, PRIMERA PLANTA, AULA 101.
Place of preparation: EDIFICI D6 DESPATX 206 Campus NORD.

Summary: The architecture of transport networks is based on current transport technology SDH (Synchronous Digital Hierarchy). The SDH networks have been designed and are optimized primarily for the transport of voice traffic. Today, it is experiencing an exponential growth in the volume of data traffic. This growth is due to the IP protocol is being consolidated as a layer of integration for multiple services, some of the requirements for Quality of Service (QoS), and also the introduction of technology to access high speed. The statistical characteristics of data traffic are different with respect to those of telephone traffic. In fact, the IP traffic is characterized not only by their asymmetry, but by its dynamic nature, as it has spikes or fluctuations are difficult to predict in advance. As a result, there is a need to migrate from existing networks to a more flexible and dynamic, optimized for the transport of data traffic. The evolution of existing transport networks move includes all features (SDH switching, monitoring of signal quality, protection against failures) optical level. The result will consist of a network of optical transport (Optical Transport Network, OTN) based on DWDM technology, Optical Cross Connects (OXC) to route optical channels are permanently or switched (Automatic Switched Optical Network, ASON). One of the major problems solved by the operators network is the efficient management of available capacity, and thus avoid the one hand the need to oversize the transport network and on the other to optimize the use of resources by defining strategies engineering traffic. The introduction of transport networks to automatic switching (ASON), capable of providing optical connections on demand, it is considered a network solution that can provide fast and flexible supply of bandwidth. This feature, made possible by defining a level of control based on the paradigm GMPLS, can be used to proactively manage the resources available, both SDH and optical level, responding efficiently to the vagaries of traffic generated the network client. However, the problem that arises is designing a mechanism to automatically trigger requests for establishment of circuits SDH / optical switched channels. In this sense, the first contribution of this thesis is the design of a firing mechanism of petitions circuit SDH / optical channels based on the prediction and monitoring network traffic (IP) client. In addition, the mechanism design includes defining policies of traffic engineering for the optimization of the use of high bandwidth provided by optical connections. Specifically, the mechanism design is characterized by interoperability between client layer and the transport layer. The thesis also includes a contribution on the design of a methodology for the design of ASON networks based on the characterization of the traffic of incoming requests for networking through its mean value and factor peakedness. Moreover, optimization of the available resources is very critical when a fault occurs in the network infrastructure because of the need to find alternative routes for traffic affected. Because of the large volume of traffic to transport, a failure in the network infrastructure could have serious economic consequences.

Author: GUALDA MANZANO EMILIO JOSE.
Year: 2005.
University: POLITÉCNICA DE CATALUÑA [www.upc.edu].
Place of defense: Aula Teleensenyament-Edifici B-3-Campud Nord.
Place of preparation: EDIFICI D4 Campus NORD.

Summary: The fundamental objective of this thesis, entitled Optimizing the performance of submarine optical links and high-capacity long distance by controlling the dispersion is the analysis, characterization, and theoretical and experimental optimization of optical fiber links submarines large capacity (hundreds of gigabits per second) and long distance (thousands of kilometers). The contents of this thesis is divided into four parts. First, we present the relevant physical phenomena that determine the characteristics of the spread of the signal via fiber optics. Specifically, we will analyze the influence of the dispersion of second and third order, non-linearity of the fiber, attenuation, gain and noise introduced by the EDFA (Erbium Doped Fiber Amplifiers), as well as the effects of PMD (Polarization Mode Dispersion). We present numerical simulation models used for the characterization of all effects mentioned above: the beam propagation method (BPM, beam propagation method) that accurately describe the propagation of the signal in the fiber, and coupled mode theory, which describes the behavior of FBG (Fiber Bragg Gratings). Here, we consider a link optical submarine long distance (L = 2000 km), with a transmission capacity of 640 gigabits per second (64 channels, 10 gigabits per second per channel). To make possible the transfer of this huge amount of information, it is necessary to control the release of the maps through fiber dispersion (Dispersion Management), ie links alternating sections of fiber-optic normal and anomalous dispersion, so that dispersion total is zero or very small, allowing at the same time that the dispersion at each point of liaison is different from zero. With this scheme is obtained control the negative influence of non-linearity of the fiber and the interference between channels (Four Wave Mixing, FWM). In this section, there have been theoretical analysis, numerical simulations of the link, and experiments in laboratories Pirelli Submarine Telecom Systems in Milan. This is an example of the need to properly simulate the link to the process of designing efficient and useful. In the third part, we analyze an optical link of a single channel with a capacity of 100 Gbps, taking into account issues such capacity building represents. Especially harmful are the negative effects of PMD and the third-order dispersion. Specifically, we focus on the distortion suffering pulses formatted RZ (return to zero) due to the dispersion of the third order, identifying a system for which the transfer is impossible, but compensates the dispersion of the third order properly. We propose a scheme to compensate for the dispersion of the third order based on the concatenation of two Fiber Bragg Gratings (FBG), properly designed to improve the performance of the system. Despite the low insertion losses, nearly linear performance and versatility of design, the FGB have some limitations, such as the degradation of the signal due to defects in the manufacture of the FGB (Group Delay Ripples), whose influence it will be analyzed and quantified. Finally, we consider the generation of ultrashort pulses, high-bandwidth, through the compression of the pulses generated by a laser Ti: sapphire after spread in a segment of singlemode optical fiber. We present two new technical characterization of short duration pulses that combines the benefits of the methods and interferometric methods temporal-frecuenciales, CFROG and MEFISTO.

Author: Chantada Santodomingo Laura.
Year: 2005.
University: SANTIAGO DE COMPOSTELA [www.usc.es].
Place of defense: Facultad de Física.
Place of preparation: Facultade de Física y Escola Universitaria de Óptica e Optometría.

Summary: The effect is temporary Talbot counterpart temporary effect of the well-known Talbot space. It is therefore consistent with a phenomenon that occurs when a sequence of periodic pulse propagates through linear dispersive half of the first order. When the accumulated dispersion is equal to a certain basic level, you get a replica of the original pulse train, in what is known as Talbot whole effect. When the accumulated dispersion is a fraction of that you get a basic scale replica of the original pulse train but with a higher rate of repetition, as long as the pulses are sufficiently narrow as to avoid overlap. This effect is known as fractional Talbot effect. In this paper, thesis presents an analysis of spectral effect Talbot. From this standpoint, the devices Talbot behave like filters paso-banda manifold, where each bandwidth interference between pulses represents a number of separate periods unit. Thus, the divisional lines Talbot filtered harmonics spectrum power outside the output signal, thus giving rise to an increase in the rate of repetition of the pulse train. The removal or rejection of these harmonics is only accurate to within the limit of pulses and transformed devices Talbot semi-enteros. In the particular case of pulses gaussianos, resulting conditions which guarantee that the filter Talbot provides a train of pulses without fluctuations in intensity even when the means with second-order dispersion. It also undertakes an analysis of tolerance and stability of the filters before Talbot slight variations of the scattering medium and the cumulative period of the pulse train. When the bandwidth of the input signal is large, small variations in the dispersion lead to a significant widening of the pulse train resulting deterioration in the functioning of the device Talbot due to the interference between pulses. Moreover, when the spectral width of the initial train is moderate changes in the dispersion deteriorate markedly harmonics filtering waste (those who do not belong to the train departure) may well generate fluctuations in intensity. When bandwidth train entry, as measured width at half height (FWHM), which is twice the rate of recurrence of the train output stability of the device is optimal. Much of the work is devoted to the study of Talbot as corrective devices or softeners imperfections pulse train input. In particular, he examines a pulse train with timing jitter and a train dice (pulse train randomly distributed). In both cases, the power spectrum is a series of bands interns around the harmonic filter noise broadband. Reducing the noise of timing jitter are analyzed through a variance, and through integration of the RF noise skirts around the harmonics. Finally discusses the influence the consistency of source devices Talbot. The inconsistency of the source acts as a filter paso-baja serving on the harmonic intensity, which in the time domain resulting in a softening of the pattern of intensities. The increase in the dispersion or reducing the coherence time of the source, reduces the bandwidth of the filter, resulting in the loss of information on a small scale of a world pattern intensity. The analysis of partial coherence of the source is also from a matrix and entrópico.