Abstract
The proposed technique consists in an optical fiber resonator interrogated for sensor characterization, implementing an alternative technique for dynamic range improvement. Such technique relies on the analysis of an added-signal caused by signal saturation, which occurs due to the broadening of the laser pulse. A wide study for different pulse widths is presented in this work, namely for 100 ns, 5 mu s and 20 mu s, being the last one related to the emergence of an added-signal for the proposed configuration. The behavior of the waveform in the presence of an intensity sensor is also characterized.

Abstract
A cantilever structure in 3D printed based on a fiber Bragg grating (FBG) sensor embedded in polymer material is proposed. The FBG sensor was embedded in 3D printed coating and was tested under three physical parameters: displacement, temperature and vibration. The sensor was tested in displacement in two different regions of the cantilever, namely, on its midpoint and end point. The maximum displacement sensitivity achieved was (3 +/- 0.1) pm/mm for end point displacement, and a temperature sensitivity of (30 +/- 1) pm/degrees C was also attained. In the case of vibration measurements it was possible to obtain a 10.23Hz-low frequency oscillation.

Abstract
A brief review in the fibre cavity ring-down (CRD) technique is presented. It addresses the latest developments in CRD technique for sensing applications, undergone at INESC TEC. The CRD is based on the conventional configuration with the possibility of adding amplification in order to compensate the output signal losses induced by the sensing head. The results obtained for strain, curvature and refractive index sensing are presented, corresponding to distinct sensing structures, namely, a chirped fibre Bragg grating (FBG), a long period grating (LPG) and a multimode interference (MMI) based sensor.

Abstract
Two different sensing structures based on a hollow microsphere Fabry-Perot cavity are proposed. The hollow spheroidal cavities are fabricated resorting only to fusion splicing. The first structure is based on a hollow microsphere located at the fiber end and works as a probe sensor. The structure was subjected to lateral load pressure and presents a sensitivity of 1.56 +/- 0.01 nm/N. The second proposed sensor relies on an in-line hollow microsphere. The sensing structure allows the detection of lateral loading, with a sensitivity of 2.62 +/- 0.02 nm/N, as well as strain detection, with a sensitivity of 4.66 +/- 0.03 pm/mu epsilon. The two proposed sensors present similar response when subjected to temperature and have low thermal sensitivity.

Abstract
This work presents a multimode interference-based fiber sensor in a cavity ring-down system for sensing temperature-induced refractive index (RI) changes of water. The sensing head is based in multimodal interference (MMI) and it was placed inside the fiber loop cavity of the CRD system. A modulated laser source was used to send pulses down into the fiber loop cavity and an erbium-doped fiber amplifier (EDFA) was placed in the fiber ring to provide an observable signal with a reasonable decay time. The behavior of the sensing head to temperature was studied due to its intrinsic sensitivity to said parameter - a sensitivity of -1.6 10(-9) s/C was attained. This allowed eliminating the temperature component from RI measurement of water and a linear sensitivity of 580 mu s/RIU in the RI range of 1.324-1.331 was obtained.

Abstract
A microfiber knot resonator integrated in an abrupt taper-based Mach-Zehnder interferometer was used for simultaneous measurement of temperature and refractive index. This compact structure was fabricated using only CO2 laser processing. The transmission spectrum is the combination of the microfiber knot resonator and the Mach-Zehnder interferometer responses. The two different components of the transmission spectrum (the microfiber knot resonator and the MachZehnder interferometer components) present different sensitivities when subjected to physical or chemical parameters. A characterization in temperature, refractive index, and sodium chloride (NaCl) concentration was performed. A simple matrix method was used for simultaneous measurement of temperature and refractive index.