The objective of this thesis was to develop applications of monolithic fiber devices and actively controlled fibers. A special twin-core fiber known as a ‘Gemini’ fiber was used to construct equal arm-length fiber interferometers, impervious to temperature and mechanical perturbations. A broadband add/drop multiplexer was constructed by inscribing fiber Bragg gratings in the arms of a Gemini Mach-Zehnder interferometer. A broadband interferometric nanosecond switch was constructed from a micro-structured Gemini fiber with incorporated metal electrodes. Additionally, a Michelson fiber interferometer was built from an asymmetric twin-core fiber and used as a high-temperature sensor. While the device could be readily used to measure temperatures below 300 °C, an annealing process was required to extend the range up to 700 °C. The work included development, construction and evaluation of the components along with numerical simulations to estimate their behaviors and to understand the underlying processes. The thesis also explored the use of electrically controlled fibers for filtering in the microwave domain. An ultra-narrow phase-shifted fiber Bragg grating inscribed in a fiber with internal electrodes was used as a scanning filter to measure modulation frequencies applied to an optical carrier. A similar grating was used inside a dual-wavelength fiber laser cavity, to generated tunable microwave beat frequencies. The studied monolithic fiber interferometers and actively controlled fibers provide excellent building blocks in such varied field as in microwave photonics, telecommunications, sensors, and high-speed switching, and will allow for further applications in the future. / Syftet med denna avhandling var att utveckla tillämpningar av monolitiska fiber komponenter samt aktivt kontrollerbara fiber. En speciell tvillingkärnefiber, även kallad ’Geminifiber’ användes för att konstruera fiber interferometrar med identisk armlängd som ej påverkas av termiska och mekaniska variationer. En bredbanding utbytarmultiplexor konstruerades genom att skriva in fiber Bragg gitter inuti grenarna på en Gemini Mach-Zehnder interferometer. Geminifibrer med interna metallelektroder användes för att konstruera en bredbandig nanosekundsnabb interferometrisk fiberomkopplare. Därtill användes en tvillingkärnefiber som en hög-temperatursensor. Även om komponenten direkt kan användas upp till 300 °C, måste den värmebehandlas för att kunna användas upp till 700 °C. Arbetet har innefattat utveckling, konstruktion och utvärdering av komponenterna parallellt med numeriska simuleringar för att analysera deras beteenden samt få insikt om de underliggande fysikaliska processerna. Avhandlingen behandlar även tillämpningar av en elektriskt styrbar fiber för att filtrera radiofrekvenser. Ett ultrasmalt fasskiftat fiber Bragg gitter skrevs in i en fiber med interna elektroder och användes som ett svepande filter för att mäta modulationsfrekvensen på en optisk bärfrekvens. Ett liknande gitter användes inuti en laserkavitet för att generera två olika våglängder samtidigt. Dessa två våglängder användes sedan för att generera en svävningsfrekvens i mikrovågsbandet. De undersökta monolitiska fiberinterferometrarna och de aktivt styrbara fibrerna erbjuder en utmärkt byggsten inom så pass skiljda områden som Mikrovågsfotonik, Telekommunikation, Sensorer samt Höghastighets-omkopplare och bör kunna användas inom många olika tillämpningar i framtiden. / <p>QC 20130226</p>

With the rapid and ongoing developments in telecommunication and electronic warfare technology, faster and more flexible systems are in demand. Wideband signal processing is thus needed to implement such systems. Microwave photonics has been introduced as a tool for achieving such ultra broadband signal processing. Instantaneous Frequency Measurement (IFM) receivers play an important role in electronic warfare. They have been developed as a means of obtaining a rapid indication of the presence of a threat and to roughly identify the frequency of the threat signals. They also have the advantages of low-cost, compactness and moderate to good sorting capability in an interference-free environment. The main limitation of the traditional RF IFM receivers is constrained bandwidth. Microwave Photonic IFMs have been considered, but the main disadvantages of photonic realization of the recent IFM receiver is cost. This work aims to propose and demonstrate low-cost photonic IFM receivers with a broad frequency measurement range. The proposed methods are based on the use of photonic mixing to down-convert the RF modulated optical signals to DC. In a RADAR warning receiver, usually a bank of IFMs is required. Increasing the numbers of IFMs requires an increase in the number of photo-detectors. Thus if low-frequency, low-cost detectors can be used, then the net system cost will be reduced significantly. The concept is proven and the issues arising are analyzed. In the proof of concept system, measurement of the RF frequency required advance knowledge of the RF power. Secondly, the use of co-axial RF cables as delay elements limited the bandwidth and increased bulk. Using a photonic hybrid approach to achieve orthogonal measurements was demonstrated as a means of dentifying both RF frequency and power simultaneously and independently. Employing all optical mixing removed the need for co-axial RF cables delays using non-linear optical devices such as Semiconductor Optical Amplifier (SOA) and Highly Non-Linear Fiber (HLNF). The last investigation is to improve the sensitivity of the implemented IFM system. The sensitivity of the implemented system is characterized first and a lock-in technique is employed to improve the sensitivity of the system. The final system achieves a sensitivity of -41 dBm which is comparable with the traditional RF IFM receivers.

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.

Los efectos de la luz lenta y luz rápida (SFL) han mostrado unas capacidades excepcionales sobre el control dinámico de la velocidad de la luz en diferentes medios. Una de las motivaciones más estimulantes redica en la potente aplicación de estos sistemas en el marco del procesado fotónico de señales de radio frecuencia (RF). En esta tesis doctoral, se evalúan las prestaciones de las plataformas de SFL actuales para desarrollar múltiples tareas que se requieren en el campo de la fotónica de microondas (MWP) con el valor añadido de sintonizabilidad y operación en banda ancha. En esta contexto, el scattering de Brillouin estimulado (SBS) tanto en fibra estándar como en fibra mantenedora de polarización (PMF), de redes Bragg (FBG), amplificadores ópticos de semiconductor (SOA) y cristales fotónicos (PhC) han sido las tecnologías bajo estudio. Desde escalas del orden de km hata mm, estas plataformas de SFL representan la evolución hacia la consolidación de componentes y subsistemas de MWP en circuitos fotónicos integrados (PIC). Diversos modelos analíticos y numéricos se han desarrollado con el objetivo de entender los procesos físicos que goboernan la porpagación a través de las diferentes plataformas de SFL, así como para describir los enfoques de MWP propuestos. Además, a través de las plataformas presentadas se ha llevado a cabo el análisis de las prestaciones de dos de las funcionalidades clave que se requieren para el procesado fotónico de señales de microondas, desfasadores sintonizables y retardos verdaderos (TTD). Se ha propuesto un sistema de TTD basado en la llamada técnica de sintonización separada de la portadora (SCT) a través de los efectos de SBS en fibrras estándr. Se ha evaluado la interacción del SBS en PMF con el propósito de desarrollar redes de Brillouin dinámicas (DBG), cuya fase generada ha sido fruto de estudio. Por otro lado, también se ha demostrado un sistema de densado distribuido basado en la reflexión continua de un pulso estrecho a lo la / Sancho Durá, J. (2012). Photonic-assisted RF Signal Processing based on Slow and Fast Light Technological Platforms [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16471 / Palancia

In this work we propose the apodization or windowing of the coupling coefficients of the unit cells conforming a coupled resonator device as a mean to reduce the level of secondary sidelobes in the case of SCISSOR configuration [7] or reducing the passband ripples in the case of CROW configuration [8]. This technique is regularly employed in the design of digital filters [18] and has been applied as well in the design of other photonic devices such as corrugated waveguide filters [9] and fiber Bragg gratings [19]. We also propose a novel technique for the apodization of coupled resonator structures by applying a longitudinal offset between resonators in order to modify the power coupling constant, which alleviates the technical requirements required for the production of these devices. We will demonstrate the design, fabrication and characterization of CROW structures employing the apodization through the aforementioned technique. / Doménech Gómez, JD. (2013). Apodized Coupled Resonator Optical Waveguides: Theory, design and characterization [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/32278 / TESIS

[ES] Con el continuo desarrollo de materiales y tecnologías de fabricación durante las últimas tres décadas, la atenuación de la transmisión de las fibras ópticas de polímero (POF) se ha reducido considerablemente. Las POF son ventajosas para las redes domésticas, así como para las interconexiones de almacenamiento, y tienen ventajas significativas para muchas aplicaciones de detección, que incluye el límite alto de tensión elástica, alta resistencia a la fractura, alta flexibilidad en la flexión, alta sensibilidad a la tensión y coeficientes termoópticos negativos. Esta tesis consigue mejorar la tecnología de irradiación con láser para POF e investiga dispositivos especiales basados en redes de difracción en POF para comunicaciones ópticas, microondas, fotónica y detección. En particular, desarrollamos la tecnología de fabricación rápida de FBGs en POF con un estudio detallado y la optimización de los parámetros de fabricación de redes de difracción de Bragg en fibra (FBG). Los resultados más destacados incluyen un FBG uniforme de 8 dB con un solo pulso láser Nd: YAG (26 nsm) (8 ns) basado en fibra dopada con BDK, que es el tiempo más corto presentado hasta ahora para la fabricación de FBGs en POF. La irradiación de fibras ópticas de polímero utilizando diferentes materiales basado en el láser KrF a 248 nm permitió demostrar un mejor rendimiento en comparación con el sistema que emplea el láser He-Cd a 325 nm. Además, se fabricaron FBGs uniformes en POFs de índice escalón dopadas con TS en menos de 1 segundo mediante la repetición de pulsos con baja energía. Finalmente, el estudio de la irradiación UV con pulsos de baja energía para la fabricación de redes de difracción estables permitió ahorrar energía en el proceso de fabricación de FBGs en POF, como uno de los principales requisitos para la producción en masa. Basándonos en la tecnología de fabricación mejorada, nos centramos en la fabricación de redes de difracción con diferentes estructuras: se fabricó un FBG con desplazamiento de fase utilizando dos pulsos de 15 ns a 248 nm KrF superpuestos por el método de Moiré; el primer FBG con chirp sintonizable se logró utilizando un solo pulso corto del láser, que abrió nuevas perspectivas a las aplicaciones basadas en redes de difracción con chirp en POF; también se propuso un nuevo método basado en gradientes térmicos para obtener FBG con chirp en POF basadas en FBG uniformes, y se demostró como la forma más conveniente publicada hasta la fecha para lograr este tipo de FBGs no uniformes en POF; y, finalmente, también se han fabricado redes de difracción de largo período utilizando un proceso de fabricación de corto tiempo, especialmente en comparación con investigaciones anteriores. En la última parte de la tesis, y en base a los dispositivos basados en redes de difracción obtenidos a lo largo de este trabajo, se han propuesto varias aplicaciones . De manera similar a los FBG en fibra de sílice, los FBGs con chirp en POF tienen muchas aplicaciones futuras en las áreas de comunicaciones ópticas y de los sensores. Este documento describe la aplicación de detección de tensión basada en una FBG con chirp sintonizable en POF, su aplicación para detección térmica en sistemas biomédicos; e ilustra el potencial de los dispositivos de dispersión sintonizables en el campo de las comunicaciones ópticas, bien como compensación de dispersión o en fotónica de microondas. / [CAT] Amb el continu desenvolupament de materials i tecnologies de fabricació durant les últimes tres dècades, l'atenuació de la transmissió de les fibres òptiques de polímer (POF) s'ha reduït considerablement. Els POF són avantatjosos per a les xarxes domèstiques, així com per a les interconnexions d'emmagatzematge, i tenen avantatges significatius per a moltes aplicacions de detecció, inclosos els límits de tensió elàstica alta, alta resistència a la fractura, alta flexibilitat en la flexió, alta sensibilitat a la tensió i potencials coeficients termoópticos negatius. Aquesta tesi va millorar la tecnologia d'irradiació amb làser per a POF i va investigar dispositius basats en xarxes difracció de Bragg (FBG) especials en POF per a comunicació òptica, microones, fotònica i detecció. En particular, desenvolupem la tecnologia de fabricació ràpida de FBG en POF amb un estudi detallat i l'optimització dels paràmetres per a la seua fabricació. Els punts destacats dels resultats inclouen un FBG uniforme de 8 dB amb un sol pols del làser Nd: YAG (266 nm) (8 ns) basat en fibra dopada amb BDK, que és el temps més curt reportat per a la fabricació de POF FBG. La irradiació de fibres òptiques de polímer utilitzant diferents materials sota el sistema de làser KrF a 248 nm va permetre demostrar un millor rendiment en comparació amb el sistema de làser Kimmon de 325 nm. A més, els FBG uniformes en el POF dopat amb TS d'índex escalonat es van aconseguir amb menys d'1 segon mitjançant la repetició de polsos de control i l'energia baixa de pols. Finalment, l'estudi de la irradiació d'energia de pols per a la fabricació de FBGs estables va permetre estalviar energia en el procés de fabricació de FBGs en POF, com un dels principals objectius de la producció en massa. Basant-nos en la tecnologia de fabricació millorada, ens centrem en la fabricació de diferents estructures de xarxes de difracció: es va fabricar un FBG amb desplaçament de fase utilitzant dos polsos de 15 ns a 248 nm KrF superposats pel mètode de Moiré; el primer FBG amb chirp sintonitzable es va aconseguir utilitzant un sol pols curt de làser, que va obrir les aplicacions basades en FBG amb chirp en POF; també es va proposar un nou mètode amb gradients tèrmics per a obtindre FBG en POF basat en FBG uniformes, i es va demostrar com la forma més convenient publicada fins hui per a aconseguir FBG POF estimulada; i, finalment, també s'han aconseguit xarxes de llarg període utilitzant un procés de fabricació de curt temps, especialment en comparació amb investigacions anteriors. Finalment, sobre la base dels dispositius de xarxes de difracció obtinguts al llarg d'aquest treball, s'han proposat diverses aplicacions potencials en aquesta tesi. De manera similar que per als FBG amb silici, el FBG amb chirp en POF té moltes aplicacions potencials en comunicacions òptiques i a l¿àrea de sensors. Aquest document descriu l'aplicació de detecció de tensió basada en FBG amb chirp sintonitzable en POF; a més, l'aplicació de detecció tèrmica en sistemes biomèdics; i el potencial dels dispositius de dispersió sintonitzables en les comunicacions òptiques, com per eixample a la compensació de dispersió o a la fotònica de microones. / [EN] With the continuing development of material and fabrication technologies over the last three decades, the transmission attenuation of polymer optical fibers (POF) has been greatly decreased. POFs are advantageous for home networks as well as storage interconnections and have significant advantages for many sensing applications, including high elastic strain limits, high fracture toughness, high flexibility in bending, high sensitivity to strain and potential negative thermo-optic coefficients. This thesis improved the laser irradiation technology for POF and investigated special grating devices in POF for optical communication, microware photonics and sensing. In particular, we developed fast POF grating fabrication technology with a detailed study and optimization of the polymer optical fiber Bragg grating (POFBG) fabrication parameters. Highlights of the results include an 8 dB uniform POFBG with one single Nd:YAG (266nm) laser pulse (8 ns) based on BDK doped fiber, which is the shortest time ever reported for POFBG fabrication. The irradiation of polymer optical fibers using different materials under 248 nm KrF laser system allowed to demonstrate a better performance compared with 325 nm Kimmon laser system. Furthermore, uniform FBGs in step-index TS doped POF were achieved with less than 1 second by means of controlling pulse repetition and low pulse energy. Finally, the study of low UV pulse power irradiation for fabricating stable gratings allowed to save energy in the POF grating fabrication process, as one of the main goals for mass production. Based on the improved fabrication technology, we focused on the fabrication of different grating structures: a phase-shifted FBG was fabricated by using two 15 ns 248 nm KrF pulses overlapped by Moiré method; the first tunable chirped FBG was achieved by using a single laser short pulse, which opened the applications based on chirped POF BGs; also a novel thermal annealing method was proposed to obtain chirped POFBGs based on uniform FBGs, and proved as the ever published most convenient way to achieve chirped POFBG; and finally, long period gratings have been also achieved by using a short time fabrication process, specially when compared with previous research. Finally, based on the grating devices obtained throughout this work, several potential applications have been proposed in this thesis. Similarly, to silica chirped FBG, chirped FBG in POF have many potential applications in optical communications and sensing area. This document described the potential strain sensing application based on tunable chirped POFBG; also, the thermal detection application in bio-medical systems; and the potential of tunable dispersion devices in optical communications, i.e., dispersion compensation or microwave photonics. / Min, R. (2019). Polymer optical fiber gratings for microwave photonics and communications application [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/125473 / TESIS

This thesis proposes research of novel hybrid photonic signal processing systems in the areas of optical communications, test and measurement, RF signal processing and extreme environment optical sensors. It will be shown that use of innovative hybrid techniques allows design of photonic signal processing systems with superior performance parameters and enhanced capabilities. These applications can be divided into domains of analog-digital hybrid signal processing applications and free-space--fiber-coupled hybrid optical sensors. The analog-digital hybrid signal processing applications include a high-performance analog-digital hybrid MEMS variable optical attenuator that can simultaneously provide high dynamic range as well as high resolution attenuation controls; an analog-digital hybrid MEMS beam profiler that allows high-power watt-level laser beam profiling and also provides both submicron-level high resolution and wide area profiling coverage; and all optical transversal RF filters that operate on the principle of broadband optical spectral control using MEMS and/or Acousto-Optic tunable Filters (AOTF) devices which can provide continuous, digital or hybrid signal time delay and weight selection. The hybrid optical sensors presented in the thesis are extreme environment pressure sensors and dual temperature-pressure sensors. The sensors employ hybrid free-space and fiber-coupled techniques for remotely monitoring a system under simultaneous extremely high temperatures and pressures.

Microwave signal processing in the optical domain is investigated in this thesis. Two signal processors including an all-optical fractional Hilbert transformer and an all-optical microwave differentiator are investigated and experimentally demonstrated. Specifically, the photonic-assisted fractional Hilbert transformer with tunable fractional order is implemented based on a temporal pulse shaping system incorporating a phase modulator. By applying a step function to the phase modulator to introduce a phase jump, a real-time fractional Hilbert transformer with a tunable fractional order is achieved. The microwave bandpass differentiator is implemented based on a finite impulse response (FIR) photonic microwave delay-line filter with nonuniformly-spaced taps. A microwave bandpass differentiator based on a six-tap nonuniformly-spaced photonic microwave delay-line filter with all- positive coefficients is designed, simulated, and experimentally demonstrated. The reconfigurability of the microwave bandpass differentiator is experimentally investigated. The employment of the differentiator to perform differentiation of a bandpass microwave signal is also experimentally demonstrated.

Microwave signal processing in the optical domain is investigated in this thesis. Two signal processors including an all-optical fractional Hilbert transformer and an all-optical microwave differentiator are investigated and experimentally demonstrated. Specifically, the photonic-assisted fractional Hilbert transformer with tunable fractional order is implemented based on a temporal pulse shaping system incorporating a phase modulator. By applying a step function to the phase modulator to introduce a phase jump, a real-time fractional Hilbert transformer with a tunable fractional order is achieved. The microwave bandpass differentiator is implemented based on a finite impulse response (FIR) photonic microwave delay-line filter with nonuniformly-spaced taps. A microwave bandpass differentiator based on a six-tap nonuniformly-spaced photonic microwave delay-line filter with all- positive coefficients is designed, simulated, and experimentally demonstrated. The reconfigurability of the microwave bandpass differentiator is experimentally investigated. The employment of the differentiator to perform differentiation of a bandpass microwave signal is also experimentally demonstrated.

Microwave signal processing in the optical domain is investigated in this thesis. Two signal processors including an all-optical fractional Hilbert transformer and an all-optical microwave differentiator are investigated and experimentally demonstrated. Specifically, the photonic-assisted fractional Hilbert transformer with tunable fractional order is implemented based on a temporal pulse shaping system incorporating a phase modulator. By applying a step function to the phase modulator to introduce a phase jump, a real-time fractional Hilbert transformer with a tunable fractional order is achieved. The microwave bandpass differentiator is implemented based on a finite impulse response (FIR) photonic microwave delay-line filter with nonuniformly-spaced taps. A microwave bandpass differentiator based on a six-tap nonuniformly-spaced photonic microwave delay-line filter with all- positive coefficients is designed, simulated, and experimentally demonstrated. The reconfigurability of the microwave bandpass differentiator is experimentally investigated. The employment of the differentiator to perform differentiation of a bandpass microwave signal is also experimentally demonstrated.