Theoretical and experimental studies of real-time interrogation of fiber Bragg grating (FBG) sensors based on chirped pulse compression with increased interrogation resolution and signal-to-noise ratio are presented. Two interrogation systems are proposed in this thesis. In the first interrogation system, a linearly chirped FBG (LCFBG) is employed as the sensing element. By incorporating the LCFBG in an optical interferometer as the sensor encoding system, employing wavelength-to-time mapping and chirped pulse compression technique, the correlation of output microwave waveform with a chirped reference waveform would provide an interrogation result with high speed and high resolution. The proposed system can provide an interrogation resolution as high as 0.25 μ at a speed of 48.6 MHz. The second interrogation system is designed to achieve simultaneous measurement of strain and temperature. In this system, a high-birefringence LCFBG (Hi-Bi LCFBG) is employed as a sensing element.

The development of communications technologies has led to an ever-increasing requirement for a wider bandwidth of microwave signal processing systems. To overcome the inherent electronic speed limitations, photonic techniques have been developed for the processing of ultra-broadband microwave signals. A dispersive delay line (DDL) is able to introduce different time delays to different spectral components, which are used to implement signal processing functions, such as time reversal, time delay, dispersion compensation, Fourier transformation and pulse compression. An electrical DDL is usually implemented based on a surface acoustic wave (SAW) device or a synthesized C-sections microwave transmission line, with a bandwidth limited to a few GHz. However, an optical DDL can have a much wider bandwidth up to several THz. Hence, an optical DDL can be used for the processing of an ultra-broadband microwave signal. In this thesis, we will focus on using a DDL based on a linearly chirped fiber Bragg grating (LCFBG) for the processing of broadband microwave signals. Several signal processing functions are investigated in this thesis. 1) A broadband and precise microwave time reversal system using an LCFBG-based DDL is investigated. By working in conjunction with a polarization beam splitter, a wideband microwave waveform modulated on an optical pulse can be temporally reversed after the optical pulse is reflected by the LCFBG for three times thanks to the opposite dispersion coefficient of the LCFBG when the optical pulse is reflected from the opposite ends. A theoretical bandwidth as large as 273 GHz can be achieved for the time reversal. 2) Based on the microwave time reversal using an LCFBG-based DDL, a microwave photonic matched filter is implemented for simultaneously generating and compressing an arbitrary microwave waveform. A temporal convolution system for the calculation of real time convolution of two wideband microwave signals is demonstrated for the first time. 3) The dispersion of an LCFBG is determined by its physical length. To have a large dispersion coefficient while maintaining a short physical length, we can use an optical recirculating loop incorporating an LCFBG. By allowing a microwave waveform to travel in the recirculating loop multiple times, the microwave waveform will be dispersed by the LCFBG multiple times, and the equivalent dispersion will be multiple times as large as that of a single LCFBG. Based on this concept, a time-stretch microwave sampling system with a record stretching factor of 32 is developed. Thanks to the ultra-large dispersion, the system can be used for single-shot sampling of a signal with a bandwidth up to a THz. The study in using the recirculating loop for the stretching of a microwave waveform with a large stretching factor is also performed. 4) Based on the dispersive loop with an extremely large dispersion, a photonic microwave arbitrary waveform generation system is demonstrated with an increased the time-bandwidth product (TBWP). The dispersive loop is also used to achieve tunable time delays by controlling the number of round trips for the implementation of a photonic true time delay beamforming system.

Deep-ocean pressure measurements are a necessary component for ocean characterization and oceanographic monitoring. Some principle applications such as tsunami detection and ocean floor subsidence are reliant on deep-ocean pressure measurement data. The deep ocean is a challenging environment especially for pressure measurements; discerning pressure changes that are a small fraction of the ambient pressure calls for intelligent engineering solutions. An ocean-deployable concept model of a pressure sensor is developed. The design is based on a diaphragm transducer intended for measuring hydrostatic pressure changes on the order of 1 centimeter of water (cmH2O) while exposed to ambient pressures several orders of magnitude greater for up to 2500 meters of water (mH2O). Two laboratory-scale pressure sensors are fabricated to test the fundamental principle of the proposed concept at lab-safe pressures. One is a single-sided sensor exposed to atmospheric pressure. The second sensor is a two-sided design that operates at a defined target depth pressure and measures the differential pressure across both faces of the diaphragm. The sensor design built for atmospheric pressure testing observed a mean experimental sensitivity of 6.05 pm/cmH2O in contrast to 6 pm/cmH2O determined theoretically. The percent error between the experimental and theoretical values is 0.83%. The second design was tested at target depth pressures of 10, 20, 40, and 60 psi (7, 14, 28, and 42 mH2O) and performance was within 5.8%, 2.8%, 0.7%, 4.0% respectively when considering percent error of the mean experimental and theoretical. The repeatability was sufficient for a given sample and pressure response within the range proposed in theory when a pressure preload was present to the diaphragm. Future work will aim at developing a design concept that incorporates a piston and is tested at a higher hydrostatic pressure system, and within ocean waters. A deployment plan and consideration of challenges associated with ocean testing will be accounted for. / Graduate

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23031号 / 理博第4708号 / 新制||理||1675(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 寺嶋 正秀, 教授 林 重彦, 教授 渡邊 一也 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

This master thesis deals with problematics of information transmission trough optical fiber and spreading of the electromagnetic field at wavelengths of light. There are analyzed characteristics of the optical signal, and described methods of measuring wavelength of the optical signal power and noise level of the useful signal. Another examined parameter is OSNR at the input and on the output of the optical fiber amplifier EFDA.

In this thesis by articles, I propose and demonstrate the full design, fabrication and characterization of optical biosensors based on (Bloch) Long Range Surface Plasmon Polaritons (LRSPPs). Gold waveguides embedded in CYTOP with an etched microfluidic channel supporting LRSPPs and gold waveguides on a one-dimensional photonic crystal (1DPC) supporting Bloch LRSPPs are exploited for biosensing applications. Straight gold waveguides embedded in CYTOP supporting LRSPPs as a biosensor, are initially used to measure the kinetics constants of protein-protein interactions. The kinetics constants are extracted from binding curves using the integrated rate equation. Linear and non-linear least squares analysis are employed to obtain the kinetics constants and the results are compared. The device is also used to demonstrate enhanced assay formats (sandwich and inhibition assays) and protein concentrations as low as 10 pg/ml in solution are detected with a signal-to-noise ratio of 20 using this new optical biosensor technology. CYTOP which has a refractive index close to water is the fluoropolymer of choice in current state of the art waveguide biosensors. CYTOP has a low glass transition temperature which introduces limitations in fabrication processes. A truncated 1D photonic crystal can replace a low-index polymer cladding such as CYTOP, to support Bloch LRSPPs within the bandgap of the 1DPC over a limited ranges of wavenumber and wavelength. Motivated by quality issues with end facets, we seek to use grating couplers in a broadside coupling scheme where a laser beam emerging from an optical fiber excites Bloch LRSPPs on a Au stripe on a truncated 1D photonic crystal. Adiabatic and non-adiabatic flared stripes accommodating wide gratings size-matched to an incident Gaussian beam are designed and compared to maximise the coupling efficiency to LRSPPs. The gratings are optimized, initially, through 2D modelling using the vectorial finite element method (FEM). Different 3D grating designs were then investigated via 3D modelling using the vectorial finite difference time domain (FDTD) method. Given their compatibility with planar technologies, gratings and waveguides can be integrated into arrays of biosensors enabling multi-channel biosensing. A multi-channel platform can provide, e.g., additional measurements to improve the reliability in a disease detection problem. Thus, a novel optical biosensor based on Bloch LRSPPs on waveguide arrays integrated with electrochemical biosensors is presented. The structures were fabricated on truncated 1D photonic crystals comprised of 15 period stack of alternating layers of SiO2/Ta2O5. The optical biosensors consist of Au stripes supporting Bloch LRSPPs and integrate grating couplers as input/output means. The Au stripes also operate as a working electrode in conjunction with a neighboring Pt counter electrode to form an electrochemical sensor. The structures were fabricated using bilayer lift-off photolithography and the gratings were fabricated using overlaid e-beam lithography. The planar waveguides are integrated into arrays capable of multichannel biosensing. The wafer is covered with CYTOP as the upper cladding with etched microfluidic channels, and wafer-bonded to a borofloat silica wafer to seal the fluidic channels and enable side fluidic interfaces. The proposed device is capable in principle of simultaneous optical and electrochemical sensing and could be used to address disease detection problems using a multimodal strategy.

This project focuses on wavelength division multiplexing passive optical network (WDM-PON) supervision using optical time domain reflectometer (OTDR) for detection and localization of any fault occurred in optical distribution network. The objective is to investigate the impact of OTDR monitoring signal on the data transmission in the WDM-PON based on wavelength re-use system, where the same wavelength is assigned for both upstream and downstream to each end user. Experimental validation has been carried out to measure three different schemes, i.e. back-to-back, WDM-PON with and without OTDR connection by using 1xN and NxN arrayed waveguide gratings. Furthermore, a comprehensive comparison has been made to trace out the effect of the monitoring signal which is transmitted together with the data through the implemented setup. Finally, the result has confirmed that the OTDR supervision signal does not affect the data transmission. The experiment has been carried out at Ericsson AB, Kista.

Volvo Cars is in a change of producing only electric and hybrid cars by 2025.Subcomponent testing is a crucial part to ensure the quality of the individual buildingblocks in an electric machine. Any way of making these tests more reliable and less timeconsuming is of great interest at Volvo. Force and temperature on bearings are especiallyhard to measure accurately, because of their placement and dynamic behavior. Accurateand reliable measurements is also a vital part in creating realistic Computer-AidedEngineering (CAE) models for simulation purposes. Simulations on bearings could lead tobetter bearing choices and accelerate the design process. This could increase bearing lifeand increase the Electrical Vehicle (EV) range due to minimized friction losses. FiberBragg Grating (FBG) sensors is a technology that has some key advantages overconventional sensors. They are immune to EMI, smaller in size, can have multiple sensorsin one fiber and can measure multiple physical quantities at the same time. Volvo Cars isinterested in investigating whether this sensor technology could be a candidate forreplacing some of the current measurement setup configurations.The project was divided into three parts, validating sensor equipment, find method forinstallation and measurement on a bearing and development of a CAE model for bearinglosses and heat transfer. To validate the sensor equipment a Measurement SystemAnalysis (MSA) was performed on two FBG fibers, one FBG isolated from strain fortemperature measurement and one FBG array with multiple sensing points. From theMSA it could be seen that the FBG temperature sensor had a total uncertainty of 3.4 °CThe FBG array had a strain uncertainty of 1.04 μ𝜀 and a temperature uncertainty of 0.4 °C.The uncertainty of both the FBG array and the FBG temperature sensor is highlydependent on the calibration of the sensitivity constant. The force measurement on thebearing was done with a concept based on the wavelength difference, produced by strain,between two FBG sensors. The concept was tested in a dynamic component rig where anaxial force could be applied, and the wavelength difference measured. The temperatureon the outer ring of the bearing was measured using an FBG isolated from strain. The testresults were promising, but since the FBG is sensitive to temperature and strain theincreased temperature difference between the two fibers affected the results. Thecalibration method needs to be compensated for the increased temperature differencebetween the fibers which is generated when the rotational speed is increased, and thiscould not be done with a single temperature measurement. The two developed CAEmodels was both constructed in MATLAB and showed similar behavior with experimentaltests done by others. To validate the models, physical test for heat transfer and bearinglosses should be performed.

Femtosecond laser direct writing in transparent materials such as glass and optical fibers has been used as a versatile tool in order to fabricate various 3-D photonic structures such as active and passive waveguides, couplers, gratings and diffractive optical elements (DOEs). This capability of patterning and refractive index modification in the bulk of transparent materials depends on the nonlinear absorption phenomenon. This practical technique has the potential to be used for cost effective and simplified manufacturing in various applications. This thesis examines three advanced manufacturing techniques that use ultrashort pulse filamentary propagation induced by nonlinear absorption in the transparent materials. First, a new gradient index lens fabrication method using femtosecond laser direct writing is introduced. Light that passes through the lens with refractive index change resulting from localized energy deposition is focused using a beam profiler. Second, wide welding area of glass samples are used to fabricate microfluidic devices with long channels by adopting customized fixture. The fixture making artificial pressure helps the two glass samples have wide optical contact area and the highly intensive pulse filamentation strongly joins glass slides. As an example of a more specific application, microfluidic samples with long grooves sealed by femtosecond laser welding were successfully fabricated as part of this project. Finally, a screw-shaped, long period grating sensor was fabricated by rotating the optical fiber. This technique enables the fiber core to have asymmetric refractive index change, resulting in higher sensitivity compared to conventional long period grating sensors. Also, a new long-period grating sensor with reverse bending effect has been demonstrated by producing complex pitches of refractive index change. / Graduate

Récemment, de nouvelles techniques ont été développées pour la fabrication des réseaux de Bragg à profil complexe. Ces composants photoniques sont utilisés dans plusieurs applications émergentes telles que la compensation de la dispersion pour les systèmes de communication de longue portée, les lasers à fibre, multiplexeurs et détecteurs optiques. Le diagnostic après inscription devrait fournir les informations nécessaires pour l’amélioration de la fabrication des réseaux de Bragg. Nous savons que les propriétés spectrales du réseau de Bragg sont liées au profil d’indice Δn. Les techniques de mesure directes, telles que la diffraction latérale de Krug, permettent de retrouver l’amplitude de modulation d’indice le long du réseau. Cependant, ces techniques sont insensibles aux fluctuations de phase. Une méthode alternative de caractérisation indirecte fondée sur l’algorithme de Layer-Peeling (LP) a été proposée. Toutefois elle ne peut pas être appliquée à la caractérisation des réseaux longs en raison de la propagation du bruit de calcul. Dans cette thèse nous avons présenté une nouvelle technique pour la mesure directe de l’amplitude et de la phase du profil d’indice le long du réseau de Bragg fondée sur la luminescence bleue (LB) induite par l’irradiation UV. Nos résultats expérimentaux de la mesure du profil de modulation d’indice sont en bonne correspondance avec la méthode de Krug. La méthode que nous proposons peut être appliquée à la caractérisation des réseaux longs. Elle permet de retrouver simultanément l’amplitude de modulation d’indice Δnac(z), la fonction du chirp et détecter le changement de l’indice moyen Δndc(z). / N the last decade new techniques were developed for fabrication of sophisticated Fiber Bragg Gratings (FGBs). This has been motivated by the emergence of many applications such as dispersion compensation for long-haul communication systems, DFB fiber lasers, optical add/drop multiplexers, and optical sensors. Post-fabrication diagnostics should provide relevant information to enhance the FBG fabrication process. It is well known that the FBG spectral properties are related to the index profile Δn. Direct measurement techniques, such as the side diffraction method reported by P. Krug, allow determining the index modulation amplitude along the FBG. Nevertheless, these techniques provide no information about phase fluctuations. An alternative method of indirect characterization, based on the Layer-Peeling (LP) algorithm, consists in Bragg grating profile reconstruction from its complex reflectivity. However, the LP method is unstable when applied to characterize long FBGs (>1mm) due to the error propagation effect. In this thesis we have shown the principle of a novel technique for the direct measurement of amplitude and phase variations of the index modulation along an FBG based on the blue luminescence (BL). Our experimental results are in a good agreement with the according Krug characterization. The proposed method of FBG characterization in amplitude and phase using the UV induced BL can be applied to long gratings (up to tens of centimeters) having complex index modulation profiles. It allows retrieving simultaneously the index profile modulation Δnac(z) and the chirp function, localizing phase shifts, and also detecting the mean index change Δndc(z).