Mención Internacional en el título de doctor The copper conductor is the physical medium traditionally used to transport power between different points. However, in recent years a new technology called Power over Fiber (PoF) has begun to be used for the same purpose. This idea firstly developed in the 1970s by the American Telephone and Telegraph Company in the field of telephony used fiber optics to power parts of a telephone instead of traditional copper. Power over Fiber technology involves the transmission of energy using an optical fiber to feed an electronic device. In its basic configuration, it consists of an energy source, typically a high power laser (HPL), an optical fiber to transmit energy to the receiving side, and a photovoltaic converter to convert light into electrical energy. This technology has several advantages over the use of copper, due to the intrinsic properties of optical fiber such as immunity to electromagnetic interference, galvanic isolation and low weight. The use of this technology is of interest in monitoring applications in high-voltage networks requiring galvanic isolation, in nuclear power generation applications, as well as in the automotive and aviation sectors. On the other hand, a scenario of special attention regarding the application of this technology is the communications sector, due to the advantages that the synergy between the transmission of energy and data through the same physical medium can provide. For those reasons, the main objective of this research is to study and develop light-powered systems that integrate solutions with intelligence in the field of sensors and communications, ensuring optimization and management of energy consumption. This research has included one chapter for the development of applications in the sensing field and three for the analysis of Power over Fiber applications in communications scenarios, specifically in the context of 5G technology. The following is a summary of the research content by chapters. Chapter 2 presents PoF systems as an emerging technology capable of transmitting energy over short and long distances using optical fiber to power remote devices. It also discusses the main theoretical concepts and parameters related to each of the elements that compromise a PoF system. The main objective of this approach is to establish the principles that will help to understand the rest of the chapters within this research. The first sections define the elements employed by the technology, the state of the art and its characteristics. Finally, considerations and critical aspects that may limit the implementation of PoF systems are addressed. Chapter 3 discusses the state of the art of PoF technology in sensing applications. Additionally, the key aspects to consider in the development of a PoF system operating in the first window are discussed. Finally, the implementation of several sensing applications in different fields such as explosive areas, in the context of Internet of Things (IoT) and pyrometry applications are discussed. Throughout the chapter, topics such as the impact of modal field diameter and fiber fuse on the power threshold supported by the fiber, and scalability analysis for powering a sensor network with a Point-to-Multipoint configuration are also analyzed. Chapter 4 addresses the main concepts associated with 5G-NR technology and focuses on the implementation and analysis of synergistic scenarios using PoF technology in a Centralized-Radio Access Networks (C-RAN) architecture. Consumption analysis in the Remote Radio Head (RRH) is carried out to evaluate the energy requirements demanded by the 5G technology and the feasibility of using power by light. Additionally, a PoF platform is developed that implements low-power modes and remote sensing through a low-power communications channel. This functionality allows monitoring and controlling parameters of the RRH, from the Central office (CO), through a computer application implemented in Matlab. The integration of 5G and PoF (5G/PoF) technology is experimentally validated through the feeding of a RF amplifier, integrated in an Analog Radio over Fiber (ARoF) scenario. Finally, the performance of the integrated 5G/PoF system is evaluated using the EVM value as a metric. Chapter 5 addresses the impact of the main fiber optic parameters on data transmission in a 5G scenario, because of power transmission in a shared scenario (data and power multiplexing on the same optical fiber). For the analysis, different laboratory experiments and simulations are carried out in an ARoF scenario operating in millimeter wave bands, with RF carriers below 20 GHz. Additionally, the influence of the Kerr effect and the nonlinear Stimulated Raman Scattering (SRS) phenomenon on the critical frequency behavior of the system and the appearance of the power fading phenomenon are analyzed. Finally, the effect of the Relative Intensity Noise of the HPL and the effects of the coupled noise in the data channel through the SRS phenomenon are discussed. In all cases, the EVM is used as a metric for the characterization of the systems. Chapter 6 addresses a PoF solution integrated in the optical fronthaul of a 5G network in a C-RAN configuration, operating at a radio frequency of 25.5 GHz. The design employs Space Division Multiplexing (SDM) integrated with PoF over a 10 km-long multicore fiber (MCF), with the objective of powering and controlling critical elements of the RRH for remotely managing its power consumption. Agent-based intelligent control is implemented in the design. Additionally, ARoF and PoF systems are characterized and the impact of power transmission on the ARoF system is evaluated for QPSK, 16 QAM and 64 QAM modulations using the BER value as a metric. In addition, two application examples based on MCF and single mode (SMF) optical fibers are explored for the optimization of the RRH power consumption. Additionally, a technique based on Tilted Fiber Bragg Gratings (TFBG) over MCF fibers for monitoring the transmitted energy is discussed. Finally, chapters 7 and 8 summarize, in English and Spanish, the main conclusions of this research and present proposals for future work. It is important to highlight as general conclusions of this work the integration capacity of PoF systems in different application scenarios, even though the threshold power supported by the optical fiber limits its transmission capacity, being more critical in the case of multimode (MMF) fibers with a gradual refractive index profile because of its smaller modal field diameter. On the other hand, the PoF systems developed in this research are compatible with current and future infrastructures in the context of 5G technology, based on SMF and MCF fibers. This research demonstrated in practice the transmission of hundreds of milliwatts over more than 10 km, using SMF fibers. In the case of MCF the transmitted power was sufficient to implement remote control of a power amplifier from the CO. The main contributions of this research include the exploration and development of sensor applications integrating novel functionalities not covered by state-of-the-art solutions so far. The systems were tested in practice and demonstrated the ability to deliver an electrical power of 340 mW at a distance of 300 m, the HPL being configured at an optical emission power of 1.5 W, which represents a system efficiency of 22.6 %. PoF applications were extended to IoT and hazardous environment safety scenarios, including capabilities such as fiber optic fault detection, which is critical in explosive atmospheres. Additionally, a PoF platform was developed in which not only the power delivered to the load was increased to 1.95 W, but also the efficiency of the system was increased up to 36 %, positioning the solution among the best reported in the state of the art. On the other hand, this research has contributed to the development of the integration of PoF systems in communications, specifically with 5G technology, where the capability of the technology for the energy control of the RRH in a C-RAN scenario was demonstrated. The developed theoretical and experimental analysis allowed understanding the impact of nonlinear phenomena in the context of PoF technology, enabling the development of more efficient synergic systems, especially in the communications scenario. Long distance systems, over 10 km, based on SMF and MCF fibers were implemented. The system based on MCF fiber is the longest distance PoF solution explored with this type of fiber in the literature. Finally, a technique for monitoring the transmitted power in PoF systems was developed and patented. Programa de Doctorado en Ingeniería Eléctrica, Electrónica y Automática por la Universidad Carlos III de Madrid Presidente: Ignacio Esquivias Moscardó.- Secretario: Sonia Martín López.- Vocal: Salvador E. Vargas Palma