Abstract
The thesis focuses on signal processing in the microwave and terahertz regions by using optical devices operating in the telecommunication band. The limitations of processing in these bands employing conventional technology can be circumvented using optical technology. On one hand, microwave electronics have high losses and are bandwidth-limited. In this case fiber-optics technology provides advantages such as low losses and almost unlimited bandwidth. On the other hand, processing of terahertz signals has been traditionally performed using free-space elements which are bulky and show long-term stability problems. Thanks to the recent development of terahertz sources and detectors compatible with 1.5 µm light processing can be performed using fiber-compatible devices, allowing for compact and stable processing systems.  
	The aim of this thesis is the development of fiber optic solutions to address limitations in the processing of signals in the lower part of the electromagnetic spectrum from radio to THz. In particular, novel photonic microwave filter structures as well as fiber optic processing for terahertz spectroscopy are analyzed. 
In the field of photonic processing of microwave signals, several new architectures have been studied. Cascaded four-wave mixing is employed to increase the number of taps of finite-impulse response filters based on dispersion. Non-periodic bandpass responses that are necessary for radio frequency applications are also implemented by electrical sampling of narrow optical filters such as phase-shifted fiber Bragg gratings and silicon microring resonators.
	With respect to the processing of terahertz signals, techniques to obtain locally increased power density are proposed. One relies on the non-linear distribution of ultrashort pulses through optical fiber while the other is based on the time modulation of the optical source spectrum by means of dispersion and a semiconductor optical amplifier interferometric structure. The increase of generated terahertz power due to the combined effect of sources with enhanced efficiency and optical processing techniques is expected to extend the applicability of tabletop terahertz systems. Finally, the generation of optical delays to replace slow delay lines based on mirrors and translation stages is addressed. The solutions proposed are based on the saturation of a semiconductor optical amplifier and single sideband carrier suppressed modulation of the spectrum. While the first approach does not introduce pulse degradation the obtained delays are small, as opposed to the second approach which obtains large delays at expenses of pulse widening.