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We present an analytical model for studying optical bistability in semiconductor lasers that exhibit a logarithmic dependence of the optical gain on carrier concentration. Model results are shown for a Fabry–Pérot quantum-well laser and compared with the predictions of a commercial computer-aided design (CAD) software tool.

Este proyecto introduce un nuevo modelo para el análisis de obras cinematográficas usando como estructura las Redes Hipermedia. En él se aprovecha el poder de estas estructuras para dotar al análisis de una mayor funcionalidad y visualidad que la que ofrece el simple análisis textual. Con ello se pretende utilizar el poder de análisis de la información mediante las tecnologías de información, adaptado al arte más importante e influyente en la actualidad, el cine. La teoría de la Deconstrucción desarrollada a finales de los años sesenta es la principal base sobre la que se construye el mismo. Se propone también la implementación de una aplicación desarrollada en Java, cuyo diseño está basado en el patrón MVC (Modelo, Vista, Controlador) que utiliza bibliotecas como Swing, Jgraph y Jdom. Con ésta se da la posibilidad al usuario de exportar sus análisis, incluyendo material multimedia, a un formato HTML. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- This work introduces a new model for Film Analysis, using as basic structure Hypermedia Networks. With this structure the visual and functional power are increased improving the results obtained by a simple textual analysis. So the information technologies are used in order to improve the analysis of the cinema, nowadays one of the most important and influential art. The Deconstruction theory developed at the end of the sixtiesis the root for building this model. The implementation of one desktop application is also proposed, following the MVC pattern (Model, View, Controller) using libraries such as Swing, Jgraph and JDOM, where the user can export the analysis made to HTML format, including Multimedia files. Ingeniería Técnica en Informática de Gestión

En el presente trabajo se ha intentado obtener una visión, lo más exacta posible, de cuál ha sido el currículo académico seguido por los miembros de algunas de las universidades más prestigiosas en todo el mundo. Para ello se han tomado 36 centros, todos ellos impartiendo la misma titulación de "Electrical Engineering", situados entre los 50 más importantes del mundo.

La importancia de la biestabilidad óptica activa es un hecho conocido, pero el uso de este efecto no lineal requiere de una correcta caracterización del dispositivo, que nos permita determinar las condiciones de polarización del mismo, para una función dada, entre las diversas aplicaciones que ofrece. El presente trabajo describe la metodología empleada para la caracterización de un diodo láser mediante herramientas CAD comerciales. Se presentan los resultados de los parámetros más característicos, contraste y anchura de histéresis, en las condiciones estándar para poder identificar los márgenes de eficiencia.

As it is known, there are five types of neurons in the mammalian retinal layer allowing the detection of several important characteristics of the visual image impinging onto the visual system, namely, photoreceptors, horizontal cells, amacrine, bipolar and ganglion cells. And it is a well known fact too, that the amacrine neuron architecture allows a first detection for objects motion, being the most important retinal cell to this function. We have already studied and simulated the Dowling retina model and we have verified that many complex processes in visual detection is performed with the basis of the amacrine cell synaptic connections. This work will show how this structure may be employed for motion detection.

Photonics logic devices are currently finding applications in most of the fields where optical signals are employed. These areas range from optical communications to optical computing, covering as well as other applications in photonics sensing and metrology. Most of the proposed configurations with photonics logic devices are based on semiconductor laser structures with "on/off" behaviors, operating in an optical amplifier configuration. They are able to offer non-linear gain or bistable operation, being these properties the basis for their applications in these fields. Moreover, their large number of potential affecting parameters onto their behavior offers the possibility to choose the best solution for each case.

In this work we present a new way to mask the data in a one-user communication system when direct sequence - code division multiple access (DS-CDMA) techniques are used. The code is generated by a digital chaotic generator, originally proposed by us and previously reported for a chaos cryptographic system. It is demonstrated that if the user's data signal is encoded with a bipolar phase-shift keying (BPSK) technique, usual in DS-CDMA, it can be easily recovered from a time-frequency domain representation. To avoid this situation, a new system is presented in which a previous dispersive stage is applied to the data signal. A time-frequency domain analysis is performed, and the devices required at the transmitter and receiver end, both user-independent, are presented for the optical domain.

In this paper we propose to employ an instability that occurs in bistable devices as a control signal at the reception stage to generate the clock signal. One of the adopted configurations is composed of two semiconductor optical amplifiers arranged in a cascaded structure. This configuration has an output equivalent to that obtained from Self-Electrooptic Effect Devices (SEEDs), and it can implement the main Boolean functions of two binary inputs. These outputs, obtained from the addition of two binary signals, show a short spike in the transition from "1" to "2" in the internal processing. A similar result is obtained for a simple semiconductor amplifier with bistable behavior. The paper will show how these structures may help recover clock signals in any optical transmission system.

Switching of a signal beam by another control beam at different wavelength is demonstrated experimentally using the optical bistability occurring in a 1.55 mm-distributed feedback semiconductor optical amplifier (DFBSOA) working in reflection. Counterclockwise (S-shaped) and reverse (clockwise) bistability are observed in the output of the control and the signal beam respectively, as the power of the input control signal is increased. With this technique an optical signal can be set in either of the optical input wavelengths by appropriate choice of the powers of the input signals. The switching properties of the DFBSOA are studied experimentally as the applied bias current is increased from below to above threshold and for different levels of optical power in the signal beam and different wavelength detunings between both input signals. Higher on-off extinction ratios, wider bistable loops and lower input power requirements for switching are obtained when the DFBSOA is operated slightly above its threshold value.

The optical bistability occurring in laser diode amplifiers is used to design an all-optical logic gate capable to provide the whole set of logic functions. The structure of the reported logic gate is based on two connected 1550nm laser amplifiers (Fabry-Perot and distributed feedback laser amplifiers).

This paper analyzes the behavior of a neural processing unit based on the optical bistable properties of semiconductor laser amplifiers. A similar unit to the reported here was previously employed in the simulation of the mammalian retina. The main advantages of the present cell are its larger fan-out and the possibility of different responses according to the light wavelength impinging onto the cell. These properties allow to work with larger structures as well as to obtain different behaviors according to the light characteristics. This new approach gives a possible modeling closer to the real biological configurations. Moreover, a more detailed analysis of the basic cell internal behavior is reported

The study of the Vertical-Cavity Semiconductor Optical Amplifiers (VCSOAs) for optical signal processing applications is increasing his interest. Due to their particular structure, the VCSOAs present some advantages when compared to their edge-emitting counterparts including low manufacturing costs, high coupling efficiency to optical fibers and the ease to fabricate 2-D arrays of this kind of devices. As a consequence, all-optical logic gates based on VCSOAs may be very promising devices for their use in optical computing and optical switching in communications. Moreover, since all the boolean logic functions can be implemented by combining NAND logic gates, the development of a Vertical-Cavity NAND gate would be of particular interest. In this paper, the characteristics of the dispersive optical bistability appearing on a VCSOA operated in reflection are studied. A progressive increment of the number of layers compounding the top Distributed Bragg Reflector (DBR) of the VCSOA results on a change on the shape of the appearing bistability from an S-shape to a clockwise bistable loop. This resulting clockwise bistability has high on-off contrast ratio and input power requirements one order of magnitude lower than those needed for edge-emitting devices. Based on these results, an all-optical vertical-cavity NAND gate with high on-off contrast ratio and an input power for operation of only 10|i\V will be reported in this paper.

We present simulation results on how power output-input characteristic bistability in Distributed FeedBack -DFB semiconductor laser diode SLA can be employed to implemented Boolean logic device. Two configurations of DFB Laser diode under external optical injection, either in the transmission or in the reflective mode of operation, is used to implement different Optical Logic Cells (OLCs), called the Q- and the P-Device OLCs. The external optical injection correspond to two inputs data plus a cw control signal that allows to choose the Boolean logic function to be implement. DFB laser diode parameters are choosing to obtain an output-input characteristic with the values desired. The desired values are mainly the on-off contrast and switching power, conforming shape of hysteretic cycle. Two DFB lasers in cascade, one working in transmission operation and the other one in reflective operation, allows designing an input-output characteristic based on the same respond of a self-electrooptic effect device is obtained. Input power for a bit "1" is 35 μW(70μW) and a bit "0" is zero for all the Boolean function to be execute. Device control signal range to choose the logic function is 0-140 μW (280 μW). Q-device (P-device)

Protecting signals is one of the main tasks in information transmission. A large number of different methods have been employed since many centuries ago. Most of them have been based on the use of certain signal added to the original one. When the composed signal is received, if the added signal is known, the initial information may be obtained. The main problem is the type of masking signal employed. One possibility is the use of chaotic signals, but they have a first strong limitation: the need to synchronize emitter and receiver. Optical communications systems, based on chaotic signals, have been proposed in a large number of papers. Moreover, because most of the communication systems are digital and conventional chaos generators are analogue, a conversion analogue-digital is needed. In this paper we will report a new system where the digital chaos is obtained from an optically programmable logic structure. This structure has been employed by the authors in optical computing and some previous results in chaotic signals have been reported. The main advantage of this new system is that an analogue-digital conversion is not needed. Previous works by the authors employed Self-Electrooptical Effect Devices but in this case more conventional structures, as semiconductor laser amplifiers, have been employed. The way to analyze the characteristics of digital chaotic signals will be reported as well as the method to synchronize the chaos generators located in the emitter and in the receiver.

Sensing systems in living bodies offer a large variety of possible different configurations and philosophies able to be emulated in artificial sensing systems. Motion detection is one of the areas where different animals adopt different solutions and, in most of the cases, these solutions reflect a very sophisticated form. One of them, the mammalian visual system, presents several advantages with respect to the artificial ones. The main objective of this paper is to present a system, based on this biological structure, able to detect motion, its sense and its characteristics. The configuration adopted responds to the internal structure of the mammalian retina, where just five types of cells arranged in five layers are able to differentiate a large number of characteristics of the image impinging onto it. Its main advantage is that the detection of these properties is based purely on its hardware. A simple unit, based in a previous optical logic cell employed in optical computing, is the basis for emulating the different behaviors of the biological neurons. No software is present and, in this way, no possible interference from outside affects to the final behavior. This type of structure is able to work, once the internal configuration is implemented, without any further attention. Different possibilities are present in the architecture to be presented: detection of motion, of its direction and intensity. Moreover, some other characteristics, as symmetry may be obtained.

The semiconductor laser diodes that are typically used in applications of optical communications, when working as amplifiers, present under certain conditions optical bistability, which is characterized by abruptly switching between two different output states and an associated hysteresis cycle. This bistable behavior is strongly dependent on the frequency detuning between the frequency of the external optical signal that is injected into the semiconductor laser amplifier and its own emission frequency. This means that small changes in the wavelength of an optical signal applied to a laser amplifier causes relevant changes in the characteristics of its transfer function in terms of the power requirements to achieve bistability and the width of the hysteresis. This strong dependence in the working characteristics of semiconductor laser amplifiers on frequency detuning suggest the use of this kind of devices in optical sensing applications for optical communications, such as the detection of shifts in the emission wavelength of a laser, or detect possible interference between adjacent channels in DWDM (Dense Wavelength Division Multiplexing) optical communication networks

Output bits from an optical logic cell present noise due to the type of technique used to obtain the Boolean functions of two input data bits. We have simulated the behavior of an optically programmable logic cell working with Fabry Perot-laser diodes of the same type employed in optical communications (1550nm) but working here as amplifiers. We will report in this paper a study of the bit noise generated from the optical non-linearity process allowing the Boolean function operation of two optical input data signals. Two types of optical logic cells will be analyzed. Firstly, a classical "on-off" behavior, with transmission operation of LD amplifier and, secondly, a more complicated configuration with two LD amplifiers, one working on transmission and the other one in reflection mode. This last configuration has nonlinear behavior emulating SEED-like properties. In both cases, depending on the value of a "1" input data signals to be processed, a different logic function can be obtained. Also a CW signal, known as control signal, may be apply to fix the type of logic function. The signal to noise ratio will be analyzed for different parameters, as wavelength signals and the hysteresis cycles regions associated to the device, in relation with the signals power level applied. With this study we will try to obtain a better understanding of the possible effects present on an optical logic gate with Laser Diodes.

The nonlinear optical properties of many materials and devices have been the main object of research as potential candidates for sensing in different places. Just one of these properties has been, in most of the cases, the basis for the sensing operation. As a consequence, just one parameter can be detected. In this paper, although just one property will be employed too, we will show the possibility to sense different parameters with just one type of sensor. The way adopted in this work is the use of the optical bistability obtained from different photonic structures. Because this optical bistability has a strong dependence on many different parameters the possibility to sense different inputs appears. In our case, we will report the use of some non-linear optical devices, mainly Semiconductor Optical Amplifiers, as sensing elements. Because their outputs depend on many parameters, as the incident light wavelength, polarization, intensity and direction, applied voltage and feedback characteristics, they can be employed to detect, at the same time, different type of signals. This is because the way these different signals affect to the sensor response is very different too and appears under a different set of characteristics.

Laser Diodes have been employed many times as light sources on different kinds of optical sensors. Their main function in these applications was the emission of an optical radiation impinging onto a certain object and, according to the characteristics of the reflected light, some information about this object was obtained. Laser diodes were acting, in a certain way, just as passive devices where their only function was to provide the adequate radiation to be later measured and analyzed. The objective of this paper is to report a new concept on the use of laser diodes taking into account their optical bistable properties. As it has been shown in several places, different laser diodes as, for example, DFB lasers and FP lasers, offer bistable characteristics being these characteristics a function of different parameters as wavelength, light polarization or temperature. Laser Bistability is strongly dependent on them and any small variation of above parameters gives rise to a strong change in the characteristics of its non-linear properties. These variations are analyzed and their application in sensing reported. The dependence on wavelength, spectral width, input power and phase variations, mainly for a Fabry-Perot Laser structure as basic configuration, is shown in this paper.

Possible switching architectures, with Optically Programmable Logic Cells - OPLCs - will be reported in this paper. These basic units, previously employed by us for some other applications mainly in optical computing, will be employed as main elements to switch optical communications signals. The main aspect to be considered is that because the nternal components of these cells have nonlinear behaviors, namely either pure bistable or SEED-like properties, several are the possibilities to be obtained. Moreover, because their properties are dependent, under certain condition, of the signal wavelength, they are apt to be employed in WDM systems and the final result will depend on the orresponding optical signal frequency. We will give special emphasis to the case where self-routing is achieved, namely to structures of the Batcher or Banyan type. In these cases, as it will be shown, there is the possibility to route any packet input to a certain direction according to its first bits. The number of possible outputs gives the number of bits needed to route signals. An advantage of this configuration is that a very versatile behavior may be allowed. The main one is the possibility to obtain configurations with different kinds of behavior, namely, Strictly Nonblocking, Wide-Sense Nonblocking or Rearrangeably Nonblocking as well as to eliminate switching conflicts at a certain intermediate stages.

Cuando se introduce una no linealidad óptica dentro de una cavidad resonante, se pueden producir efectos de conmutación rápida entre dos estados diferenciados de transmisión. Este fenómeno se conoce por biestabilidad óptica, caracterizado porque la salida de los dispositivos con este tipo de comportamiento constan de dos estados estables diferenciados y una región asociada a un ciclo de histéresis en la cual el sistema es inestable. En dicha región la salida posee valores diferentes para un mismo valor de entrada en función de la historia del dispositivo.

Optical signal processing in any living being is more complex than the one obtained in artificial systems. Cortex architecture, although only partly known, gives some useful ideas to be employed in communications. To analyze some of these structures is the objective of this paper. One of the main possibilities reported is handling signals in a parallel way. As it is shown, according to the signal characteristics each signal impinging onto a single input may be routed to a different output. At the same time, identical signals, coming to different inputs, may be routed to the same output without internal conflicts. This is due to the change of some of their characteristics in the way out when going through the intermediate levels. The simulation of this architecture is based on simple logic cells. The basis for the proposed architecture is the five layers of the mammalian retina and the first levels of the visual cortex.

This paper reports a model of the mammalian retina as well as an interpretation of some functions of the visual cortex. Its main objective is to simulate some of the behaviors observed at the different retina cells depending on the characteristics of the light impinging onto the photoreceptors. This simulation is carried out with a simple structure employed previously as basic building block of some optical computer architectures. Its possibility to perform any type of Boolean function allows a wide range of behaviors.

En este trabajo se ha evaluado la influencia del valor del tiempo de recombinación de portadores en el comportamiento de un dispositivo biestable. Queda patente el compromiso existente entre la velocidad de respuesta alcanzable y la cantidad de potencia necesitada para el funcionamiento de estos dispositivos. Una elección adecuada de este parámetro determinará si un dispositivo podrá ser utilizado en aplicaciones de alta velocidad, o bien en aplicaciones que requieran poca potencia y alto grado de procesamiento en paralelo.

A major research area is the representation of knowledge for a given application in a compact manner such that desired information relating to this knowledge is easily recoverable. A complicated procedure may be required to recover the information from the stored representation and convert it back to usable form. Coder/decoder are the devices dedicated to that task. In this paper the capabilities that an Optical Programmable Logic Cell offers as a basic building block for coding and decoding are analyzed. We have previously published an Optically Programmable Logic Cells (OPLC), for applications as a chaotic generator or as basic element for optical computing. In optical computing previous studies these cells have been analyzed as full-adder units, being this element a basic component for the arithmetic logic structure in computing. Another application of this unit is reported in this paper. Coder and decoder are basic elements in computers, for example, in connections between processors and memory addressing. Moreover, another main application is the generation of signals for machine controlling from a certain instruction. In this paper we describe the way to obtain a coder/decoder with the OPLC and which type of applications may be the best suitable for this type of cell.

Most of the present digital images processing methods are related with objective characterization of external properties as shape, form or colour. This information concerns objective characteristics of different bodies and is applied to extract details to perform several different tasks. But in some occasions, some other type of information is needed. This is the case when the image processing system is going to be applied to some operation related with living bodies. In this case, some other type of object information may be useful. As a matter of fact, it may give additional knowledge about its subjective properties. Some of these properties are object symmetry, parallelism between lines and the feeling of size. These types of properties concerns more to internal sensations of living beings when they are related with their environment than to the objective information obtained by artificial systems. This paper presents an elemental system able to detect some of the above-mentioned parameters. A first mathematical model to analyze these situations is reported. This theoretical model will give the possibility to implement a simple working system. The basis of this system is the use of optical logic cells, previously employed in optical computing.

Nowadays, in order to take advantage of fiber optic bandwidth, any optical communications system tends to be WDM. The way to extract a channel, characterized by a wavelength, from the optical fiber is to filter the specific wavelength. This gives the systems a low degree of freedom due to the fact of the static character of most of the employed devices. In this paper we will present a different way to extract channels from an optical fiber with WDM transmission. The employed method is based on an Optically Programmable Logic Cells (OPLC) previously published by us, for other applications as a chaotic generator or as basic element for optical computing. In this paper we will describe the configuration of the OPLC to be employed as a dropping device. It acts as a filter because it will extract the data carried by a concrete wavelength. It does depend, internally, on the wavelength. We will show how the intensity of the signal is able to select the chosen information from the line. It will be also demonstrated that a new idea of redundant information it is the way of selecting the concrete wavelength. As a matter of fact this idea is apparently the only way to use the OPLC as a dropping device. Moreover, based on these concepts, a similar way to route signals to different routes is reported. The basis is the use of photonic switching configurations, namely Batcher or Bayan structures, where the unit switching cells are the above indicated OPLCs.

In living bodies, the correct perceptual representation of size constancy requires that an object's size appear the same when it changes its location with respect to the observer. At the same time, it is necessary that objects at different locations appear to be the same size if they are. In order to do that, the perceptual system must recover from the stimuli impinging on the individual, from the light falling on the retina, a representation of the relative sizes of objects in the environment. Moreover, at the same time, image perception is related to another type of phenomena. It corresponds to the well known perceptual illusions. To analyze this facts, we propose a system based on a particular arrays of receptive points composed by optical fibers and dummy fibers. The structure is based on the first layers of the mammalians primary visual cortex. At that part of the brain, the neurons located at certain columns, respond to particular directions. This orientation changes in a systematic way as one moves across the cortical surface. In our case, the signals from the above-mentioned array are analyzed and information concerning orientation and size of a particular line is obtained. With this system, the Muelle-Lyer illusion has been studied and some rules to interpret why equal length objects give rise to different interpretations are presented.

Optical logic cells, employed in several tasks as optical computing or optically controlled switches for photonic switching, offer a very particular behavior when the working conditions are slightly modified. One of the more striking changes occurs when some delayed feedback is applied between one of the possible output gates and a control input. Some of these new phenomena have been studied by us and reported in previous papers. A chaotic behavior is one of the more characteristic results and its possible applications range from communications to cryptography. But the main problem related with this behavior is the binary character of the resulting signal. Most of the nowadays-employed techniques to analyze chaotic signals concern to analogue signals where algebraic equations are possible to obtain. There are no specific tools to study digital chaotic signals. Some methods have been proposed. One of the more used is equivalent to the phase diagram in analogue chaos. The binary signal is converted to hexadecimal and then analyzed. We represented the fractal characteristics of the signal. It has the characteristics of a strange attractor and gives more information than the obtained from previous methods. A phase diagram, as the one obtained by previous techniques, may fully cover its surface with the trajectories and almost no information may be obtained from it. Now, this new method offers the evolution around just a certain area being this lines the strange attractor.

The type of signals obtained has conditioned chaos analysis tools. Almost in every case, they have analogue characteristics. But in certain cases, a chaotic digital signal is obtained and theses signals need a different approach than conventional analogue ones. The main objective of this paper will be to present some possible approaches to the study of this signals and how information about their characteristics may be obtained in the more straightforward possible way. We have obtained digital chaotic signals from an Optical Logic Cell with some feedback between output and one of the possible control gates. This chaos has been reported in several papers and its characteristics have been employed as a possible method to secure communications and as a way to encryption. In both cases, the influence of some perturbation in the transmission medium gave problems both for the synchronization of chaotic generators at emitter and receiver and for the recovering of information data. A proposed way to analyze the presence of some perturbation is to study the noise contents of transmitted signal and to implement a way to eliminate it. In our present case, the digital signal will be converted to a multilevel one by grouping bits in packets of 8 bits and applying conventional methods of time-frequency analysis to them. The results give information about the change in signals characteristics and hence some information about the noise or perturbations present. Equivalent representations to the phase and to the Feigenbaum diagrams for digital signals are employed in this case.

The main objective of this paper is to present some tools to analyze a digital chaotic signal. We have proposed some of them previously, as a new type of phase diagrams with binary signals converted to hexadecimal. Moreover, the main emphasis will be given in this paper to an analysis of the chaotic signal based on the Lempel and Ziv method. This technique has been employed partly by us to a very short stream of data. In this paper we will extend this method to long trains of data (larger than 2000 bit units). The main characteristics of the chaotic signal are obtained with this method being possible to present numerical values to indicate the properties of the chaos.

A new method to analyze the influence of possible hysteresis cycles in devices employed for optical computing architectures is reported. A simple full adder structure is taken as the basis for this method. Single units, called optical programmable logic cells, previously reported by the authors, compose this structure. These cells employ, as basic devices, on-off and SEED-like components. Their hysteresis cycles have been modeled by numerical analysis. The influence of the different characteristic cycles is studied with respect to the obtained possible errors at the output. Two different approaches have been adopted. The first one shows the change in the arithmetic result output with respect to the different values and positions of the hysteresis cycle. The second one offers a similar result, but in a polar diagram where the total behavior of the system is better analyzed.

We proposed an optical communications system, based on a digital chaotic signal where the synchronization of chaos was the main objective, in some previous papers. In this paper we will extend this work. A way to add the digital data signal to be transmitted onto the chaotic signal and its correct reception, is the main objective. We report some methods to study the main characteristics of the resulting signal. The main problem with any real system is the presence of some retard between the times than the signal is generated at the emitter at the time when this signal is received. Any system using chaotic signals as a method to encrypt need to have the same characteristics in emitter and receiver. It is because that, this control of time is needed. A method to control, in real time the chaotic signals, is reported.

A new proposal to have secure communications in a system is reported. The basis is the use of a synchronized digital chaotic systems, sending the information signal added to an initial chaos. The received signal is analyzed by another chaos generator located at the receiver and, by a logic boolean function of the chaotic and the received signals, the original information is recovered. One of the most important facts of this system is that the bandwidth needed by the system remain the same with and without chaos.

A new method to study large scale neural networks is presented in this paper. The basis is the use of Feynman- like diagrams. These diagrams allow the analysis of collective and cooperative phenomena with a similar methodology to the employed in the Many Body Problem. The proposed method is applied to a very simple structure composed by an string of neurons with interaction among them. It is shown that a new behavior appears at the end of the row. This behavior is different to the initial dynamics of a single cell. When a feedback is present, as in the case of the hippocampus, this situation becomes more complex with a whole set of new frequencies, different from the proper frequencies of the individual neurons. Application to an optical neural network is reported.

A proposal for a model of the primary visual cortex is reported. It is structured with the basis of a simple unit cell able to perform fourteen pairs of different boolean functions corresponding to the two possible inputs. As a first step, a model of the retina is presented. Different types of responses, according to the different possibilities of interconnecting the building blocks, have been obtained. These responses constitute the basis for an initial configuration of the mammalian primary visual cortex. Some qualitative functions, as symmetry or size of an optical input, have been obtained. A proposal to extend this model to some higher functions, concludes the paper.

A chaotic output was obtained previously by us, from an Optical Programmable Logic Cell when a feedback is added. Some time delay is given to the feedback in order to obtain the non-linear behavior. The working conditions of such a cell is obtained from a simple diagram with fractal properties. We analyze its properties as well as the influence of time delay on the characteristics of the working diagram. A further study of the chaotic obtained signal is presented.

A method to study some neuronal functions, based on the use of the Feynman diagrams, employed in many-body theory, is reported. An equation obtained from the neuron cable theory is the basis for the method. The Green's function for this equation is obtained under some simple boundary conditions. An excitatory signal, with different conditions concerning high and pulse duration, is employed as input signal. Different responses have been obtained.

A first study in order to construct a simple model of the mammalian retina is reported. The basic elements for this model are Optical Programmable Logic Cells, OPLCs, previously employed as a functional element for Optical Computing. The same type of circuit simulates the five types of neurons present in the retina. Different responses are obtained by modifying either internal or external connections. Two types of behaviors are reported: symmetrical and non-symmetrical with respect to light position. Some other higher functions, as the possibility to differentiate between symmetric and non-symmetric light images, are performed by another simulation of the first layers of the visual cortex. The possibility to apply these models to image processing is reported.

A possible approach to the synchronization of chaotic circuits is reported. It is based on an Optically Programmable Logic Cell and the signals are fully digital. A method to study the characteristics of the obtained chaos is reported as well as a new technique to compare the obtained chaos from an emitter and a receiver. This technique allows the synchronization of chaotic signals. The signals received at the receiver, composed by the addition of information and chaotic signals, are compared with the chaos generated there and a pure information signal can be detected. Its application to cryptography in Optical Communications comes directly from these properties. The model here presented is based on a computer simulation.

In this paper an approach to the synchronization of chaotic circuits has been reported. It is based on an optically programmable logic cell and the signals involved are fully digital. It is based on the reception of the same input signal on sender and receiver and from this approach, with a posterior correlation between both outputs, an identical chaotic output is obtained in both systems. No conversion from analog to digital signals is needed. The model here presented is based on a computer simulation.

A model of the mammalian retina and the behavior of the first layers in the visual cortex is reported. The building blocks are optically programmable logic cells. A model of the retina, similar to the one reported by Dowling (1987) is presented. From the model of the visual cortex obtained, some types of symmetries and asymmetries are possible to be detected.

Tras una serie de consideraciones sobre el papel de los paradigmas en Ciencia y Tecnología, se presenta uno de los posibles avances que podrá tener lugar en los próximos años, basado en el estudio de los sistemas biológicos como modelos para la realización de funciones concretas. Según se muestra, este nuevo planteamiento podría desarrollar una forma mucho más efectiva de consecución de objetivos que la actualmente obtenida con sistemas artificiales. Como ejemplo concreto se muestra el caso de la visión en los mamíferos

Digital chaotic behaviour in an Optical-Processing Element is reported. It is obtained as the result of processing two fixed trains of bits. Period doublings in a Feigenbaum-like scenario have been obtained. A new method to characterize digital chaos is reported

Digital chaotic behavior in an optically processing element is analyzed. It was obtained as the result of processing two fixed trains of bits. The process is performed with an optically programmable logic gate. Possible outputs, for some specific conditions of the circuit, are given. Digital chaotic behavior is obtained, by using a feedback configuration. Different ways to analyze a digital chaotic signal are presented.

One of the most challenging problems that must be solved by any theoretical model purporting to explain the competence of the human brain for relational tasks is the one related with the analysis and representation of the internal structure in an extended spatial layout of múltiple objects. In this way, some of the problems are related with specific aims as how can we extract and represent spatial relationships among objects, how can we represent the movement of a selected object and so on. The main objective of this paper is the study of some plausible brain structures that can provide answers in these problems. Moreover, in order to achieve a more concrete knowledge, our study will be focused on the response of the retinal layers for optical information processing and how this information can be processed in the first cortex layers. The model to be reported is just a first trial and some major additions are needed to complete the whole vision process.

Several works have been published in the last years concerning the modelling and implementation of the visual cortex operation. Most of them present simple neurons with just two different responses, namely inhibitory and excitatory. Some of the different types of visual cortex cells are simulated in these configurations.

Hay un hecho que resulta evidente: la ISDN (Red Digital de Servicios Integrados) sólo podrá penetrar de forma efectiva en la sociedad cuando esta vea que los servicios que puede proporcionar satisfacen un amplio conjunto de necesidades reales

A new proposal to the study of large-scale neural networks is reported. It is based on the use of similar graphs to the Feynman diagrams. A first general theory is presented and some interpretations are given. A propagator, based on the Green's function of the neuron, is the basis of the method. Application to a simple case is reported.

De una manera general, se plantea la posible necesidad de adoptar un enfoque diferente al tomado hasta hoy, de una progresiva especialización en la Ciencia y la Tecnología. De acuerdo con algunos de los planteamientos existentes para el estudio de ambas, y más en concreto de los derivados de la Teoría del Caos o de la Complejidad, se postula la necesidad de adoptar unos enfoques más interdisciplinarios que los existentes hasta hoy. Un más rápido avance de todas las ramas del conocimiento se cree puede ser resultado de este nuevo enfoque.