Digital Coherent Receivers and Advanced Optical Modulation Formats in 100 and 200 Gb/s DWDM Systems

Recent advances in coherent optical receivers is reviewed. Digital-Signal-Processing (DSP) based phase and polarization management techniques make coherent detection robust and feasible. With coherent detection, the complex field of the received optical signal is fully recovered, allowing compensation of linear and nonlinear optical impairments including chromatic dispersion (CD) and polarization-mode dispersion (PMD) using digital filters. Coherent detection and advanced optical modulation formats have become a key ingredient to the design of modern dense wavelength-division multiplexed (DWDM) optical broadband networks. In this paper, firstly we present the different subsystems of a digital coherent optical receiver, and secondly, we will compare the performance of some multi-level and multi-dimensional modulation formats in some physical impairments and in high spectral-efficiency (SE) and high-capacity DWDM transmissions, simulating the DSP with Matlab and the optical network performance with OptiSystem software.

Uncertainty in optical bio-sensors due to the spectral displacement of the interference modes of the transduction signal. Incertidumbre en bio-sensores ópticos asociada al desplazamiento espectral de los modos de interferencia de la señal de transducción

The analysis of the interference modes has an increasing application, especially in the field of optical biosensors. In this type of sensors, the displacement Δν of the interference modes of the transduction signal is observed when a particular biological agent is placed over the biosensor. In order to measure this displacement, the position of a maximum (or a minimum) of the signal must be detected before and after placing the agent over the sensor. A parameter of great importance for this kind of sensors is the period Pν of the signal, which is inversely proportional to the optical thickness h0 of the sensor in the absence of the biological agent. The increase of this period improves the sensitivity of the sensor but it worsens the detection of the maximum. In this paper, authors analyze the propagation of uncertainties in these sensors when using least squares techniques for the detection of the maxima (or minima) of the signal. Techniques described in supplement 2 of the ISO-GUM Guide are used. The result of the analysis allows a metrological educated answer to the question of which is the optimal period Pν of the signal. El análisis del comportamiento de los modos de interferencia tiene una aplicación cada vez más amplia, especialmente en el campo de los biosensores ópticos. En este tipo de sensores se observa el desplazamiento Δν de los modos de interferencia de la señal de transducción al reconocer un de-terminado agente biológico. Para medir ese desplazamiento se debe detectar la posición de un máximo o mínimo de la señal antes y después de dicho desplazamiento. En este tipo de biosensores un parámetro de gran importancia es el periodo Pν de la señal el cual es inversamente proporcional al espesor óptico h0 del sensor en ausencia de agente biológico. El aumento de dicho periodo mejora la sensibilidad del sensor pero parece dificultar la detección del mínimo o máximo. Por tanto, su efecto sobre la incertidumbre del resultado de la medida presenta dos efectos contrapuestos: la mejora de la sensibilidad frente a la dificultad creciente en la detección del mínimo ó máximo. En este trabajo, los autores analizan la propagación de incertidumbres en estos sensores utilizando herramientas de ajuste por MM.CC. para la detección de los mínimos o máximos de la señal y técnicas de propagación de incertidumbres descritas en el suplemento 2 de la Guía ISO-GUM. El resultado del análisis permite dar una respuesta, justificada desde el punto de vista metrológico, de en que condiciones es conveniente o no aumentar el periodo Pν de la señal.

Ground and airborne level optical sensors: is it possible to estimate maize crop N status?

Adjusting N fertilizer application to crop requirements is a key issue to improve fertilizer efficiency, reducing unnecessary input costs to farmers and N environmental impact. Among the multiple soil and crop tests developed, optical sensors that detect crop N nutritional status may have a large potential to adjust N fertilizer recommendation (Samborski et al. 2009). Optical readings are rapid to take and non-destructive, they can be efficiently processed and combined to obtain indexes or indicators of crop status. However, other physiological stress conditions may interfere with the readings and detection of the best crop nutritional status indicators is not always and easy task. Comparison of different equipments and technologies might help to identify strengths and weakness of the application of optical sensors for N fertilizer recommendation. The aim of this study was to evaluate the potential of various ground-level optical sensors and narrow-band indices obtained from airborne hyperspectral images as tools for maize N fertilizer recommendations. Specific objectives were i) to determine which indices could detect differences in maize plants treated with different N fertilizer rates, and ii) to evaluate its ability to identify N-responsive from non-responsive sites.

Study of the effects of moving targets in SAR images for their detection.

Synthetic Aperture Radar’s (SAR) are systems designed in the early 50’s that are capable of obtaining images of the ground using electromagnetic signals. Thus, its activity is not interrupted by adverse meteorological conditions or during the night, as it occurs in optical systems. The name of the system comes from the creation of a synthetic aperture, larger than the real one, by moving the platform that carries the radar (typically a plane or a satellite). It provides the same resolution as a static radar equipped with a larger antenna. As it moves, the radar keeps emitting pulses every 1/PRF seconds —the PRF is the pulse repetition frequency—, whose echoes are stored and processed to obtain the image of the ground. To carry out this process, the algorithm needs to make the assumption that the targets in the illuminated scene are not moving. If that is the case, the algorithm is able to extract a focused image from the signal. However, if the targets are moving, they get unfocused and/or shifted from their position in the final image. There are applications in which it is especially useful to have information about moving targets (military, rescue tasks,studyoftheflowsofwater,surveillanceofmaritimeroutes...).Thisfeatureiscalled Ground Moving Target Indicator (GMTI). That is why the study and the development of techniques capable of detecting these targets and placing them correctly in the scene is convenient. In this document, some of the principal GMTI algorithms used in SAR systems are detailed. A simulator has been created to test the features of each implemented algorithm on a general situation with moving targets. Finally Monte Carlo tests have been performed, allowing us to extract conclusions and statistics of each algorithm.

Development and fabrication of optical biosensors based on biophotonic sensing cells (BICELLs)

El objetivo de esta tesis es el desarrollo y caracterización de biosensores ópticos sin marcado basados en celdas sensoras biofotónicas (BICELLs). Éstas son un nuevo concepto de biosensor desarrollado por el grupo de investigación y consiste en la combinación de técnicas de interrogación vertical, junto a estructuras fotónicas producidas usando métodos de micro- y nanofabricación. Varias conclusiones son extraídas de este trabajo. La primera, que se ha definido una BICELL estándar basada en interferómetros Fabry-Perot (FP). Se ha demostrado su capacidad para la comparación de rendimiento entre BICELLs estructuradas y para la realización de inmunoensayos de bajo coste. Se han estudiado diferentes técnicas de fabricación disponibles para la producción de BICELLs. Se determinó que la litografía de contacto a nivel de oblea produce estructuras de bajo coste, reproducibles y de alta calidad. La resolución alcanzada ha sido de 700 nm. El estudio de la respuesta a inmunoensayos de las BICELLs producidas se ha desarrollado en este trabajo. Se estudió la influencia de BICELLs basadas en diferentes geometrías y tamaños. De aquí resulta un nuevo enfoque para predecir el comportamiento de respuesta para la detección biológica de cualquier biosensor óptico estructurado, relacionando su superficie efectiva y su sensibilidad óptica. También se demostró una técnica novedosa y de bajo coste para la caracterización experimental de la sensibilidad óptica, basada en el depósito de películas ultradelgadas. Finalmente, se ha demostrado el uso de BICELLs desarrolladas en esta tesis, en la detección de aplicaciones reales, tales como hormonas, virus y proteínas. ABSTRACT The objective of this thesis is the development and characterization of optical label-free biosensors based on Bio-Photonic sensing Cells (BICELLs). BICELL is a novel biosensor concept developed by the research group, and it consists of a combination of vertical interrogation optical techniques and photonic structures produced by using micro- and nano-fabrication methods. Several main conclusions are extracted from this work. Firstly, a standard BICELL is defined based on FP interferometers, which demonstrated its capacity for accomplishing performance comparisons among different structured BICELLs, as well as to achieve low-cost immunoassays. Different available fabrication techniques were studied for BICELL manufacturing. It is found that contact lithography at wafer scale produce cost-effective, reproducible and high quality structures. The resolution achieved was 700 nm. Study on the response of developed BICELLs to immunoassays is performed within this work. It is therefore studied the influence of BICELLs based on different geometries and sizes in the immunoassay, which resulted in a new approach to predict the biosensing behaviour of any structured optical biosensor relating to its effective surface and optical sensitivity. Also, it is demonstrated a novel and low-cost characterization technique of the experimental optical sensitivity, based on ultrathin-film deposition. Finally, it is also demonstrated the capability of using the developed BICELLs in this thesis for real applications detection of hormones, virus and proteins.