The work presented in this thesis, investigating two novel optical fibre sensor systems, was carried out as part of industrially sponsored (Radiodetection Ltd) and supported applied research project. The first sensor determines the longitudinal position of acoustic disturbances acting on an extended length of optical fibre cable and the second system locates the lateral position of a buried dielectrically-sheathed fibre cable. The second system is believed to be the first optically-based sensor for the location of buried fibre optic cables. An RF electromagnetic field, emitted from above the cable, radiates through the ground and modulates the polarisation state of the light guided by the optical fibre, via the Faraday effect. The lateral position of the buried cable can then be inferred by observing the peak in the amplitude of modulation as the locator is traversed across the buried position of the fibre allowing, for the first time, dielectrically-sheathed optical cables to be located non-intrusively.

Eine sensorbasierte Überwachung des Anlagenzustands stellt eine Voraussetzung für die zustandsabhängige Instandhaltung dar. Ein kabelloses funkbasiertes Messsystem senkt den Installationsaufwand erheblich und ermöglicht Messungen auch an schwer zugänglichen Orten. Zudem reduziert ein energieautarkes System den Wartungsaufwand, da zum Beispiel Batteriewechsel überflüssig werden. Das vorliegende Werk beschreibt die softwareseitige Optimierung eines solchen bestehenden Sensorkonzepts. Zu diesem Zweck wurde ein Messkonzept zur Bestimmung der zur Datenübertragung benötigten Sendedauer entwickelt, welches einen Vergleich mit dem bestehenden Sensorkonzept ermöglicht.:Abbildungsverzeichnis ... VII Tabellenverzeichnis ... IX Abkürzungsverzeichnis ... X 1 Einleitung ... 1 2 Stand der Technik ... 3 3 Gegenstand und Untersuchung ... 9 3.1 Verwendete Hardwarekomponenten ... 9 3.1.1 Kommunikationszentrum und Zentralorgan des Sensornetzwerks ... 9 3.1.2 Leitwerte ... 11 3.1.3 Sensorknoten ... 11 3.2 Netzwerkkommunikation mit HTTP ... 18 3.3 Beschreibung des messtechnischen Basiskonzepts ... 21 3.4 Gesamtenergiebilanz des Sensorknotens und Optimierungspotentiale ... 24 4 Darstellung und Bewertung von IT-Konzepten zur Verbesserung der Energieeffizienz ... 27 4.1 OSI-Schichtenmodell und Einordnung des bestehenden Sensorkonzepts ... 27 4.2 Alternativen in den transportorientierten Schichten ... 29 4.3 Alternativen in den anwendungsorientierten Schichten ... 32 4.4 Übersicht und Vergleich der vorgestellten Protokolle ... 35 4.5 Auswahl des MQTT-Protokolls ... 38 5 IT-Konzept zur kommunikationstechnischen Optimierung des Basiskonzepts ... 43 5.1 Softwaretechnische Implementierung der Datenübertragung mittels MQTT-Protokoll ... 43 5.2 Softwaretechnische Anpassung der Leitwerte ... 45 5.3 Beschreibung des Gesamtkonzepts im Sollzustand ... 48 6 Messtechnische Untersuchung ... 51 6.1 Messtechnische Strategie zur Ermittlung der Sendeleistung und der Sendedauer ... 51 6.1.1 Messschaltung ... 51 6.1.2 Übersicht über gesamten Messaufbau ... 58 6.2 Ergebnisse der Untersuchung und Gegenüberstellung der Resultate ... 60 6.3 Nachbetrachtungen ... 66 7 Zusammenfassung und Ausblick ... 69 Inhaltsverzeichnis ... 71

This thesis presents the development and test of an integrated ion camera chip for monitoring highly localised ion fluxes of electrochemical processes using an ion sensitive sensor array. Ionic concentration fluctuations are shown to travel across the sensor array as a result of citric acid injection and the BZ-reaction. The imaging capability of non-equilibrium chemical activities is also demonstrated monitoring self-assembling micrometre sized polyoxometalate tubular and membranous architectures. The sufficient spatial resolution for the visualisation of the 10-60 µm wide growing trajectories is provided by the dense sensor array containing 64×64 pixels. In the case of citric acid injection and the BZ-reaction the ion camera chip is shown to be able to resolve pH differences with resolution as low as the area of one pixel. As a result of the transient and volatile ionic fluxes high time resolution is required, thus the signal capturing can be performed in real.time at the maximum sampling rate of 40 µs per pixel, 10.2 ms per array. The extracted sensor data are reconstructed into ionic images and thus the ionic activities can be displayed as individual figures as well as continuous video recordings. This chip is the first prototype in the envisioned establishment of a fully automated CMOS based ion camera system which would be able to image the invisible activity of ions using a single microchip. In addition the capability of detecting ultra-low level pH oscillations in the extracellular space is demonstrated using cells of the slime mould organism. The detected pH oscillations with extent of ~0.022 pH furthermore raise the potential for observing fluctuations of ion currents in cell based tissue environments. The intrinsic noise of the sensor devices are measured to observe noise effect on the detected low level signals. It is experimentally shown that the used ion sensitive circuits, similarly to CMOS, also demonstrate 1/f noise. In addition the reference bias and pH sensitivity of the measured noise is confirmed. Corresponding to the measurement results the noise contribution is approximated with a 28.2 µV peak-to-peak level and related to the 450 µV +/- 70 µV peak-to-peak oscillations amplitudes of the slime mould. Thus a maximum intrinsic noise contribution of 6.2 +/- 1.2 % is calculated. A H+ flickering hypothesis is also presented that correlates the pH fluctuations on the surface of the device with the intrinsic 1/f noise. The ion camera chip was fabricated in an unmodified 4-metal 0.35 µm CMOS process and the ionic imaging technology was based on a 64×64-pixel ion sensitive field effect transistor (ISFET) array. The high-speed and synchronous operation of the 4096 ISFET sensors occupying 715.8×715.8 µm space provided a spatial resolution as low as one pixel. Each pixel contained 4 transistors with 10.2×10.2 µm layout dimensions and the pixels were separated by a 1 µm separation gap. The ion sensitive silicon nitride based passivation layer was in contact with the floating gates of the ISFET sensors. It allowed the capacitive measurements of localised changes in the ionic concentrations, e.g. pH, pNa, on the surface of the chip. The device showed an average ionic sensitivity of 20 mV/pH and 9 mV/pNa. The packaging and encapsulation was carried out using PGA-100 chip carriers and two-component epoxies. Custom designed printed circuit boards (PCBs) were used to provide interface between the ISFET array chip and the data acquisition system. The data acquisition and extraction part of the developed software system was based on LabVIEW, the data processing was carried out on Matlab platform.

This thesis describes an investigation into the suitability of complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) devices for scientific imaging applications. CMOS APS offer a number of advantages over the established charge-coupled device (CCD) technology, primarily in the areas of low power consumption, high-speed parallel readout and random (X-Y) addressing, increased system integration and improved radiation hardness. The investigation used a range of newly designed Test Structures in conjunction with a range of custom developed test equipment to characterise device performance. Initial experimental work highlighted the significant non-linearity in the charge conversion gain (responsivity) and found the read noise to be limited by the kTC component due to resetting of the pixel capacitance. The major experimental study investigated the contribution to dark signal due to hot-carrier injection effects from the in-pixel transistors during read-out and highlighted the importance of the contribution at low signal levels. The quantum efficiency (QE) and cross-talk were also investigated and found to be limited by the pixel fill factor and shallow depletion depth of the photodiode. The work has highlighted the need to design devices to explore the effects of individual components rather than stand-alone imaging devices and indicated further developments are required for APS technology to compete with the CCD for high-end scientific imaging applications. The main areas requiring development are in achieving backside illuminated, deep depletion devices with low dark signal and low noise sampling techniques.

La détection de l'hydrogène est une priorité environnementale. De nombreux capteurs à hydrogène ont déjà été développés, mais aucun d’eux ne répond aux exigences de l'industrie. Les capteurs à fibres optiques, électriquement isolés, sont d’excellents candidats pour fonctionner dans des environnements explosifs. Notre objectif est de développer un capteur à fibres optiques intrinsèque par Résonance de Plasmon de Surface pour la détection d’hydrogène. Dans cette thèse, nous étudions deux designs de capteurs à hydrogène. Le premier, basé sur la modulation d'amplitude, se compose d'une couche mince de Pd déposé sur le cœur de la fibre multimode, après avoir enlevé la gaine optique. Dans le second, basé sur la modulation de longueur d'onde, nous remplaçons la couche de Pd par un empilement de couches (Au / SiO 2 / Pd). Dans cette thèse, nous démontrons que les capteurs plasmoniques peuvent être une solution pour développer des capteurs à hydrogène fiables et rapides. Enfin, nous étudions des alliages de Mg comme matériaux sensibles à l’hydrogène afin d’optimiser la plage de détection des capteurs à hydrogène. / Hydrogen detection is an environmental priority. Numerous hydrogen sensors have been developed, but none of them meet the industry requirements. Optical fiber sensors, electrically isolated, are excellent candidates for operating in explosive environments. Our goal is to develop an intrinsic optical fiber sensor based on Surface Plasmon Resonance. In this thesis, we study two optical fiber hydrogen sensors. The first sensor, based on amplitude modulation, consists of a thin Pd layer deposited on the multimode fiber core, after removing the optical cladding. The second design, based on wavelength modulation, consists of replacing the single Pd layer by a Au/ SiO2/ Pd multilayer stack. We demonstrate in this thesis that plasmonic sensors may be a solution to develop fast and reliable fiber hydrogen sensors. Finally, we study Mg alloys as hydrogen sensitive material in order to improve the detection range of hydrogen sensors.