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This work proposes a photonic method to generate optical pulses with a triangular wave shape using a low coherence source. We modulate this source using a sinusoidal radio frequency signal as a local oscillator. We eliminate the second harmonic of the spectral components generated by the modulation process tuning a reject filter to get a triangular wave. We implement the filter using an interferometer with a delay line in one of their branches. To tune the filter, the only adjustment required is over the optical delay line. We developed our scheme in a simulation environment but based on the use of optical and optoelectronic elements with parameters of commercial devices, some of them available in our laboratory. We generate triangular waveform signals with pulse frequencies of 100, 150, 250, and 300 MHz as proof of concept. The proposed scheme has the advantage of being low cost and easy to use because it does not require bias control nor adjustment to Vpi voltage. Usually, other authors must vary these parameters to get the desired electrical signal. Still, we generate the triangular waveform by adjusting only the local oscillator frequency and the optical delay line. Therefore, because we use a broad-spectrum optical source and do not require a strictly controlled variable voltage, our system will be cheaper.

Stamping and deep drawing precuts are normally produced using cut to length and blanking lines. Within these process chains, the shearing process represents an essential process operation that controls the final quality of the cutting edge and the precision and flatness of the precut sheet. Since the use of high strength steels is continuously increasing in the automotive industry, the tool and machine builders need to consider more aggressive processes and higher shearing forces. In this paper, the cutting force of several steels has been experimentally measured using different shearing angles. For that, a new tool has been constructed where the shearing force and stroke can be monitored using a mechanical press. These measurements have been used to calculate the specific cutting coefficient for the different alloys and angles. As a result analytical methods for the calculation of the maximum shearing force are obtained.

We present a BPSK coherent optical wireless link in a multiple-beam, multiple-aperture configuration. The data are recovered using the signal obtained by the coherent addition of a set of maximum likelihood optical phase estimates and a select-largest stage. The proposal offers higher performance than the combining methods commonly used in optical wireless systems with diversity transmission and coherent detection.

We evaluate the performance of a sub-optimum optical phase estimator obtained using a state variable description of the optical channel and stochastic estimation techniques. We implement the estimator for an urban wireless communications network.

We first study the state of polarization of the superposition of partially polarized, statistically independent optical fields with application in coherent detection systems with emphasis on heterodyne configurations and obtain the DOP of the mixture of wave fields. Next we obtain the available heterodyne power after photodetection. Finally we obtain the spectrum of the photocurrent process resulting from the coherent detection of partially polarized amplitude-stabilized fields.

This paper describes the research activities undertaken at CICESE, B.C., Mexico, for the human resource training and for the development of optical quantum communication systems for different quantum channels such as the optical fiber and for the free-space. As a sample of our more recent work in such field we describe the processes realized to get the synthesis, characterization and implementation of the different subsystems required for the operation of a quantum channel with a low number of photons using coherent optical detection in the receiving stage and the binary optical phase modulation in the transmitter side.

Mexican Space Agency (AEM) formation is triggering a series of actions to coordinate research groups, companies and governmental agencies together, in order to develop in a more orderly fashion technology, services and space applications. The aim is to produce conditions for establishing an industrial environment that will allow Mexico to integrate into the International Community of countries with quality space research and development. A strategy for the initial phase is presented, based on a series of projects for developing micro and nano satellites projects for LEO using COTS technology. An network focused on Space R&D supported by CONACYT (National R&D Council of Mexico), integrated by Universities, companies and R&D centers is working together with the AEM for this purpose. In order to define some projects that would help leading the countries development in this initial stage is hazardous however the networking model coupled with the general strategy set by AEM will allow the development an integration of a healthy environment for space R&D and industrial development in the Mexican space area.

Structures having symmetrically centered microstrip lines enclosed in a metallic waveguide are analyzed by the finite-element method. Single and combined shielding effects on the microstrip effective dielectric constant due to a top cover and two side walls are investigated. A finite-element computer program has been written in Fortran for a supercomputer to obtain very accurate numerical results by means of the solution of a very large system of linear equations. In addition, a new set of accurate empirical equations adequate for CAD to take both effects into account has been developed. Results are compared with other numerical and empirical methods, and discussions are also presented. © 1994 John Wiley & Sons, Inc.

Using the Poincare sphere and wavelength scanning it is possible to determine if the fiber birefringence corresponds to that of a linear, circular or elliptical retarder, as well as to obtain an approximate measurement of the polarization beatlength. This method is useful for low birefringence single-mode fibers. It is applied to erbium-doped fibers.

Erbium-doped monomode optical fibers are widely used to build amplifiers, lasers, incoherent light sources and sensors. Since the performance of these devices can be modified by its spectral birefringence, it is important to characterize it. In the case of an elliptical retarder the determination of the sign of the linear birefringence and the relative value of the linear and circular distributed birefringence is not obvious. In this work we analyze the anisotropic response of erbium fibers assuming that they are uniform and behave as a distributed retarder with linear and circular birefringence. Taking advantage of the geometric properties of the Poincare sphere it is possible to separate the linear birefringence contribution from that of the circular birefringence and to determine their signs and relative values.

In this work we present a polarimetric method that uses a polarization description based on the Poincare sphere. The erbium fiber is modeled assuming that it is uniform and behaves as a distributed retarder with linear and circular birefringences. We show that taking advantage of the geometric properties of the Poincare sphere it is possible to separate the linear birefringence contribution from that of the circular birefringence while the measurement precision is optimized. The experimental procedure here presented provides reproducible results for the measurement of the linear and circular distributed birefringences in erbium-doped fibers.

"In this work we describe the design and implementation of a CDMA transmitter with application on thirdgeneration mobile and personal communication systems. We present several experimental results."

The SATEX I project, is a Mexican effort with the purpose of design, construct and operate an experimental microsatellite in low-earth orbit, in a university and multi-institutional environment. The scientific mission is focused on electronic telecommunications research with a Ka band experiment and the optical payload; also, a CCD camera is included for remote image acquisition. The SATEX Optical Payload (SOP) is an experimental system aimed to perform BER and attenuation measurements. The SOP consists in a laser transmitter in the 830 nm and a quad-photo receiver in the 530 nm. The experiment is divided in two features: the downlink where the measurements will be performed and the uplink that will be used to perform the pointing of the experiment. The SOP has a control system to establish and keep a link by opto-electro-mechanical means, which tracks and acquires the optical beacon. This beacon is a non-modulated light source generated by the earth station. When the satellite receives it, it is then used to acknowledge the location of the earth station; therefore, the modulated laser beam can be transmitted to Earth. The technical looks of design of all the subsystems and the prototype obtained are presented and the link calculation is discussed.

We present two configurations of new fiber optic Bragg grating sensor developed for petroleum hydrocarbon detection. The sensor includes FBG attached to the special polymer swelling in the hydrocarbon presence. This polymer reversibly strains the fiber section with the Bragg grating inside. The first sensor configuration employs a single grating and standard demodulation technique to determine a strain induced shift of the Bragg wavelength. The second sensor configuration make a use of double grating interferometric sensor consisting of a reference grating free from axial strain and a sensitive one, attached to the polymer. A new demodulation technique is based on monitoring of energy of the interference term in the reflection spectrum. We demonstrated experimentally that such configuration is free from temperature influence. The paper presents the results of the swelling-behavior test of the sensitive polymer material and the results of the experimental investigation of the hydrocarbon sensor performance.

In this paper, we present a new fiber optic Bragg grating sensor for petroleum hydrocarbon leak detection. The developed sensor includes fiber section with imprinted in the fiber core Bragg grating covered by special polymer material. This polymer reversibly swells under hydrocarbon influence and strains the fiber section with the Bragg grating inside. As a result of the fiber elongation, the Bragg wavelength shifts to aside longer wavelength. Experimentally demonstrated shift of the grating resonant wavelength was more than 2 nm for 20-min gasoline influence, which significantly exceeds a shift due to possible environmental temperature variation and the width of the grating reflection spectrum, which was about 0.5 nm. The paper presents also the results of the swelling-behavior test of the loaded and unloaded sensitive polymer material under liquid and vapor gasoline influence and the results of the theoretical and experimental investigation of the hydrocarbon sensor performance.

Several models have been developed to describe the interaction between neighboring ions in heavily doped erbium fibers. All of them are based on the anomalous saturation of the pump power. In this work we present experimental results of the anomalous behavior of the gain saturation in an EDFA, induced by the signal's power. This additional information shows us that energy migration is also induced by phonons.

In this work we present an analysis of the birefringence effects induced by external fields on passive fibers and, on the basis of this information, we propose an explanation for some effects observed in active fibers. To modify the passive fiber birefringence we have used external forces. The photo-elastic description of the birefringence induced by simple stresses is verified for short circuit cylindrical samples of silica glass (step-index and GRIN). Phase and polarization changes of light transmitted through these samples were studied using holographic interferometry and polarimetry. Using these results, a proposal is made to understand the polarization sensitivity of EDFAs. In the case of active fibers its birefringence was altered changing its geometrical shape. The amplifying performance of an EDFA built with a helically-wound active fiber was compared with that of an EDFA built with an irregularly wound erbium fiber.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Multitask bus for small satellites is being developed at the University of Mexico (UNAM) for the conduction of LEO communications, remote sensing, and astronomical missions. The first prototype, SATEX-1, to be launched by Ariane in mid 1994, is a 50 Kg engineering test satellite with a primary communications payload and a CCD camera for low resolution imaging, as a secondary payload. SATEX-1 has been under design and development for several years and will be constructed by several research institutions, under finance from the Ministry of Communications (SCT/IMC). The structure is made of hybrid materials, including light aluminum alloys and composites. It has a three axis stabilization system. Attitude detection is realized by means of several sun and earth sensors. Electrical power is collected by two solar panels that are stowed for take-off, and deployed after separation. Thermal design is based mostly on passive components including radiators, shielding and orientation, but flat heaters are used in several places. Solid-state temperature sensors are used throughout the s/c to test and calibrate thermal models.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A remote temperature sensor has been developed to measure the temperature of a metal alloy in microgravity conditions, on board an automatic and sealed experimental station in the Space Shuttle. The device is composed of an optical system, that allows thermal radiation from the hot body to pass through an orifice in the oven, and focus onto an infrared detector whose output photocurrent is a function of temperature. The experiment is fully microcomputer controlled, and temperature data is both, utilized to control the heating path, and stored in the memory for postflight analysis. In this paper, design, construction, calibration, testing and performance of the system are described.

The experimental development of an optical payload for free space communications is presented. This payload is designed to operate in the SATEX I mission that consists of an experimental LEO microsatellite development for technological and research purposes. This experiment consists of the design and implementation of a transmitter in 830 nm like the information channel (downlink) and a photoreceiver in the 530 nm that collects the Earth station beacon (uplink) for acquisition and pointing purposes. We have projected as primary goal BER and attenuation measurements in the downlink channel. The technical aspects of the design of all the subsystems are presented, including the link calculation, the characterization of the prototype and the expected performance.

In PHEMT chip characterization, the parasitic elements due to the chip carrier have to be de-embedded prior to the extraction of the intrinsic elements. At frequencies lower than 5 GHz, the chip carrier is modeled by a “π” capacitive network; however, at frequencies around 10 GHz, a resonance on the Y21-parameter of the chip carrier alone is observed, and the “π” capacitive circuit is no longer valid. In this work, an improved circuit for modeling the chip carrier in the frequency range of 0.045–26.5 GHz is proposed. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 20: 233–236, 1999.

En el presente trabajo de investigación se estudia el procesamiento de información cuántica utilizando estados coherentes con fotones agregados (PACS). Se parte de un estudio de la superposición general de PACS con $n$, $m$ fotones agregados a los estados coherentes $\ket{\alpha}$ y $\ket{\beta}$ de la forma $\ket{\psi} \propto u \ket{{\alpha},m}\ket{{\beta},n }+ v \ket{{\beta},n}\ket{{\alpha},m}$ cuyo entrelazamiento es caracterizado por medio de la concurrencia. Se obtuvieron las condiciones generales para entrelazamiento no nulo, así como una familia de estados máximamente entrelazados mediante expresiones analíticas de la concurrencia y, se estudió el efecto de un canal despolarizante simple sobre esta superposición. En la siguiente etapa, los estados generales se restringen a los que pueden obtenerse experimentalmente, en donde se ha agregado sólo un fotón en uno de los subistemas de la forma $\ket{\psi}_{\text{dp,pa}}=\mathcal{N} (\hat{a}^\dagger \mp \hat{b}^\dagger )\ket{\alpha}\ket{\alpha}$, por lo que son superposiciones de PACS individuales (SPACS). Estas superposiciones se denominan canal de fotones desplazados (DPC) para la ``-", y de fotones agregados (PAC) para la ``+". Las características no clásicas de los DPC y PAC sometidos a la influencia de ruido por esparcimiento y fluctuaciones de fase se estudian a través de la perturbación inducida por una medición homodina (MID homodino) y la discordia cuántica (QD). Se obtuvieron expresiones analíticas que relacionan el QD con una observable para casos sin ruido y con ruido. La observable utilizada son las fluctuaciones de la cuadratura del campo de un subsistema. Los canales DPC y PAC se utilizan como recurso entrelazado para realizar procesamiento de información cuántica a través de un protocolo de teleportación híbrido basado en detección de fotones individuales y detección homodina. Se analizó la capacidad del canal a través de la fidelidad para teleportar un estado, y se obtuvieron expresiones tanto para el caso puro como el caso con ruido. La fidelidad se calcula para cada estado a teleportar y como un promedio para evaluar la capacidad de teleportación del canal. Finalmente, se propone la generación de los canales estudiados en la banda de telecomunicaciones a través de fotones o SPACS anunciados generados en una fibra óptica no lineal mediante el proceso de la mezcla espontánea de cuatro ondas (SFWM) y mezclados en un divisor de haz con el vacío. Se prueba la viabilidad de generar SPACS me In this work, we study quantum information processing with photon added coherent states (PACS). First, the general superposition of $n,m$ added photons to the coherent states $\ket{\alpha}$ and $\ket{\beta}$ of the form $\ket{\psi} \propto u \ket{{\alpha},m}\ket{{\beta},n }+ v \ket{{\beta},n}\ket{{\alpha},m}$ is studied, whose entanglement is characterized by means of Concurrence. The general conditions for non-null entanglement as long as a family of maximally entangled states were obtained. The decoherent effect a simple depolarization channel was also analyzed. As a second part of the study, the states are restricted to the easiest experimentally feasible, in which only one photon is added to each subsystem in the form $\ket{\psi}_{\text{dp,pa}}=\mathcal{N} (\hat{a}^\dagger \mp \hat{b}^\dagger )\ket{\alpha}\ket{\alpha}$ forming superpositions of single PACS (SPACS). These superpositions are named displaced photons channel (DPC) for ``-", and photon added channel (PAC) for ``+". The non-classical character of DPC and PAC affected by noise sources of scattering and phase fluctuation are studied by means of homodyne measurement induced disturbance (homodyne MID) and quantum discord (QD). Analytical expressions that relate QD and one observable were obtained for pure and noise-influenced cases. The observable used is field-quadrature fluctuations for one subsystem. DPC and PAC channels are used as an entangled resource to perform quantum information process through a hybrid quantum teleportation protocol based on single photon and homodyne detections. The channel capacity was analyzed with the fidelity to teleport a state, and closed expressions were obtained for the pure and mixed cases. Fidelity was calculated for each state to teleport and as an average as well to evaluate the teleportation capacity of the channel. Finally, the generation of the studied channels is proposed in the telecommunications band with heralded single photons or SPACS generated within a non-linear fiber optic by spontaneous four wave mixing (SFWM) that are mixed in a beamsplitter with vacuum. The viability of SPACS generations with SFWM was also proved. The generated channels have spectral properties related withe the non-linear process. The non-classical signature of the channel is evaluated by means of the teleportation fidelity for defined spectral windows. Average fidelities of $ \mathcal{F}>0.8 $ were obtained for some spectral windows, which proves the viability of this prop

En este trabajo se realiza el estudio teórico-experimental de los sistemas de comunicaciones ópticas cuánticas con aplicaciones satelitales. Se describe en primer lugar la teoría pertinente a dichos sistemas cuánticos y en base, a los requerimientos y características de este tipo de sistemas, se propone y se diseña un esquema de comunicación óptica cuántica para enlaces en espacio libre empleando estados ópticos coherentes fuertemente atenuados modulados en fase. Este sistema fue implementado utilizando dispositivos ópticos en espacio libre. Por conveniencia, se emplea un esquema auto-homodino que consta de un láser operando a 1550 nm, del cual se obtiene la señal de datos y el oscilador local. La señal de datos es modulada en fase y atenuada fuertemente para simular las pérdidas presentes en un enlace en espacio libre a largas distancias, logrando potencias ópticas equivalentes a 0.25 (12x10-15 watts) y 5 fotones (200x10-15 watts) por pulso con una velocidad de transmisión de 350 KHz. El esquema de recepción hace uso de los estados de polarización de la señal de datos y el oscilador local, lineal a 45 grados y circular, respectivamente, para permitir la medición simultánea de los componentes en cuadratura del campo óptico, también conocido como híbrido óptico de 90 grados. Además, se diseñó e implementó una estructura de sincronización de fase por medio de un lazo de Costas, la cual fue optimizada considerando el ruido de amplitud y de fase. Usando la estructura de sincronización de fase optimizada, se obtuvieron los parámetros de desempeño del sistema completo, los cuales estuvieron en buen acuerdo con el análisis teórico para bajo número de fotones. Además, se implementó un esquema semejante al mencionado, solo que ahora usando un hibrido óptico de 90 grados fibrado y dos fuentes láseres independientes con un ancho de línea angosto (