Abstract
Sensing at small dimensions in biological and medical environments requires miniaturized sensors with high sensitivity and measurement resolution. In this work a small optical fiber probe was developed to apply the Vernier effect, allowing for enhanced temperature sensing. Such effect is an effective way of magnifying the sensitivity of a sensor or measurement system in order to reach higher resolutions. The device is a multimode silica Fabry-Perot interferometer structured at the edge of a tapered multimode fiber by focused ion beam milling. The Vernier effect is generated from the interference between different modes in the Fabry-Perot interferometer. The sensor was characterized in temperature, achieving a sensitivity of -654 pm/degrees C in a temperature range from 30 degrees C to 120 degrees C. The Vernier effect provided a temperature sensitivity over 60-fold higher than the sensitivity of a normal silica Fabry-Perot interferometer without the effect. The temperature resolution obtained was 0.14 degrees C, however this value was limited by the resolution of the OSA and can be improved further to less than 0.015 degrees C.

Abstract
We present a portable and low-cost system for interrogation of long-period fiber gratings (LPFGs) costing around a 30th of the price of a typical setup using an optical spectrum analyzer and a broadband light source. The unit is capable of performing real-time monitoring or as a stand-alone data-logger. The proposed technique uses three thermally modulated fiber-coupled laser diodes, sweeping a few nanometers around their central wavelength. The light signal is then modulated by the LPFG and its intensity is acquired by a single photo-detector. Through curve-fitting algorithms the sensor transmission spectrum is reconstructed. Testing and validation were accomplished by inducing variations in the spectral features of an LPFG through changes either in external air temperature from 22 to 425 degrees C or in refractive index (RI) of the surrounding medium from 1.3000 to 1.4240. A dynamic resolution between 3.5 and 1.9 degrees C was achieved, in temperatures from 125 to 325 degrees C. In RI measurements, maximum wavelength and optical power deviations of 2.75 nm and 2.86 dB, respectively, were obtained in the range from 1530 to 1570 nm. The worse RI resolution obtained was 3.47x10(-3). The interrogation platform was then applied in the detection of iron corrosion, expressing wavelength peak values within 1.12 nm from the real value in the region between 1530 and 1570 nm.

Abstract
An optical fiber Fabry-Perot (FP) for relative humidity (RH) sensing is proposed. The FP cavity is fabricated by splicing a short length of hollow silica tube in a single mode fiber. The fiber is then coated with a polyvinylidene fluoride (PVDF) thin film to work as a mirror. The fabrication process of the FP interferometer with a dip coating process in a PVDF/dimethyl formamide solution is presented. The pattern fringes of the FP suffer a wavelength shift due to the change in the PVDF's refractive index with the ambient RH variation. A short overview of the cavity's formation and stability is presented. The RH response of the FPI cavity is tested. The sensor presented a sensitivity of 32.54 pm/%RH at constant temperature and -15.2 pm/degrees C for temperature variation.

Abstract
In view of the growing importance of nanotechnologies, the detection of nanoparticles type in several contexts has been considered a relevant topic. Several organisms, including the National Institutes of Health, have been highlighting the urge of developing nanoparticles exposure risk assessment assays, since very little is known about their physiological responses. Although the identi fi cation/characterization of synthetically produced nanoparticles is considered a priority, there are many examples of \ naturally" generated nanostructures that provide useful information about food components or human physiology. In fact, several nanoscale extracellular vesicles are present in physiological fluids with high potential as cancer biomarkers. However, scientists have struggled to fi nd a simple and rapid method to accurately detect/identify nanoparticles, since their majority have diameters between 100-150 nm -far below the di ff raction limit. Currently, there is a lack of instruments for nanoparticles detection and the few instrumentation that is commonly used is costly, bulky, complex and time consuming. Thus, considering our recent studies on particles identi fi cation through back-scattering, we examined if the time/frequency-domain features of the back-scattered signal provided from a 100 nm polystyrene nanoparticles suspension are able to detect their presence only by dipping a polymeric lensed optical fi ber in the solution. This novel technique allowed the detection of synthetic nanoparticles in distilled water versus \ blank solutions" (only distilled water) through Multivariate Statistics and Arti fi cial Intelligence (AI)-based techniques. While the state-of-the-art methods do not o ff er a ff ordable and simple approaches for nanoparticles detection, our technique can contribute for the development of a device with innovative characteristics.

Abstract
Dissolved carbon dioxide (dCO2) evaluation is very important in many different fields. In this work, a new, integrated, colorimetric-optical fiber-based system for dCO2 monitoring in aquaculture industry was developed. The sensing chemistry is based on colorimetric changes of the used indicator—poly p-nitrophenol (pNPh)—in contact with CO2. Preliminary tests were done in a laboratory environment (calibration) and in a laboratory Recirculating Aquaculture System (RAS) with controlled CO2 injection. The results have shown the suitability of the new sensor for assessing dCO2 dynamics in RAS and its fast detection of low dCO2 concentrations in an appropriate operation range.

Abstract
Colloids and suspensions are part of our daily routines. Even the blood is considered a "naturally" occurring colloid. However, the majority of colloids are complex and composed by a diversity of nano to microparticles. The characterization of both synthetic and physiological fluids in terms of particulate types, size and surface characteristics plays a vital role in products formulation, and in the early diagnosis through the identification of abnormal scatterers in physiological fluids, respectively. Several methods have been proposed for characterizing suspensions, including imaging, electrical sensing counters, hydrodynamic or field flow fractionation. However, the Dynamic Light Scattering (DLS) has evolved as the most convenient method from these. Based also on the scattering signal, we propose a novel, simple and fast method able to determine the number of different scatterers type present in a suspension, without any previous information about its composition (in terms of particle classes). This is achieved by collecting features from a 980 nm laser back-scattered signal acquired through a polymeric lensed optical fiber tip dipped into the solution. Unlike DLS, this technique allows the trapping of particles whose diameter >= 1 mu m. For smaller particles, despite not guaranteeing their immobilization, it is also able to determine the number of different nanoparticles classes in an ensemble. The number of particle types was correctly determined for suspensions of synthetic particles and yeasts; different bacteria; and 100 nm nanoparticles types, using both Principal Component Analysis and K-means algorithms. This method could be a valuable alternative to complex and time-consuming methods for particles separation, such as field flow fractionation.