Abstract
Optical fiber gratings have long shown their sensing capabilities. One of the main challenges, however, is the interrogation method applied, since typical systems tend to use broadband light sources with optical spectrum analyzers, laser scanning units or CCD (Charged Coupled Device) spectrometers. The following paper presents the development of an interrogation system, which explores the temperature response of a multimode laser diode, in order to interrogate long period fiber gratings. By performing a spectral sweep along one of its rejection bands, a discrete attenuation spectrum is created. Through a curve fitting technique, the original spectrum is restored. The built unit, while presenting a substantially reduced cost compared with typical interrogation systems, is capable of interrogating along a 10 nm window with measurement errors reaching minimum values as low as 0.4 nm, regarding the grating central wavelength, and 0.4 dB for its attenuation. Given its low cost and reduced dimensions, the developed system shows potential for slow-changing field applications.

Abstract
This work presents an experimental study on the effects of gamma radiation on Long Period Fiber Gratings (LPFGs) in a low-dose test campaign to evaluate their eventual degradation. The study was carried out with standard single-mode fibers where the grating was inscribed using the Electric-Arc Discharge (EAD) technique. Before the gamma campaign, a detailed optical characterization was performed with repeatability tests to verify the accuracy of the setup and the associated error sources. The gamma-induced changes up to a dose of 200 krad and the recovery after radiation were monitored with the Dip Wavelength Shift (DWS). The results show that the gamma sensitivity for a total dose of 200 krad is 11 pm/krad and a total DWS of 2.3 nm has been observed with no linear dependence. Post-radiation study shows that recovery from radiation-induced wavelength shift is nearly complete in about 4000 h. Experimental results show that the changes suffered under gamma irradiation of these LPFGs are temporary making them a good choice as sensors in space applications.

Abstract
Background: Biogenic amines (BAs) are compounds considered to be contaminants of foodstuff and are cause of poisoning. The main BAs found in foods are cadaverine, putrescine, tyramine, histamine, spermine and spermidine. The number of food poisoning cases associated with BAs in food has increased in the recent years reinforcing the need for early detection to ensure high levels of food quality and safety. Scope and approach: This review aims to provide a general approach to the different BAs detected in foods their concentrations and sample treatments. These compounds are found in varying concentrations in a wide variety of foods such as fish, meat, fruits, vegetables, cheese, wine, and beer. It also refers the different analytical techniques currently used for the detection of BAs, as well as the different treatments of the samples and innovations of the techniques currently used that allow greater sensitivity and speed of the analyzes and with obtaining detection limits lower and lower. Key findings and conclusions: BAs are present in a wide variety of foods and their concentration is highly influenced by the storage conditions of food products. BAs can be precursors of nitrosamines, which have been linked to carcinogenic and mutagenic activity. Several analytical techniques and sample treatments have been improved in the last few years for better and faster detection of BAs.

Abstract
A detailed study of turn around point (TAP) long period fiber gratings (LPFGs) with coupling to the asymmetric cladding modes of a standard single-mode fiber (SMF-28e), fabricated by femtosecond (fs) laser direct writing was realized. The entire fabrication process, including the coating with different titanium dioxide (TiO2) film thicknesses of LPFGs and the corrections needed to achieve coated devices operating precisely in the TAP condition with coupling to the asymmetric cladding modes, was addressed. The significant fabrication details are also given, such as inscription periods, shape and localization of the refractive index modifications across the core. The fabrication process described allows the optimization of the LPFGs sensitivity in regards to the surrounding refractive index (SRI). Optimization of the writing parameters to obtain gratings working at the TAP for two different media surrounding the fiber (water and air) was achieved. It was demonstrated that for a grating period of 191.8 mu m, the LP1,12 mode exhibits a TAP at 1442.7 nm in air, and for a period of 192.5 mu m, the same mode exhibits a TAP at 1448.6 nm in water. The LPFGs operating at the TAP in air and water were coated with 10, 20, and 30 nm thin TiO2 film thicknesses and the spectral behavior characterized. The wavelength sensitivity to the surrounding refractive index (SRI) was assessed in the range between 1.3700 to 1.4120, and a maximum sensitivity of similar to 8051.4 nm/RIU was measured for the 192.5 mu m LPFG coated with a 30 nm thick TiO2 film.

Abstract
The use of Long-Period Fiber Gratings (LPFGs) as sensors has been thoroughly researched, given the multitude of parameters these structures can monitor by themselves (such as temperature, strain, curvature) and the potential for combination with other materials that allow for monitoring of parameters such as humidity, pH and chemical concentration, at a low price and with easy fabrication processes available. This interest has increased the need for the development of interrogation systems for these sensors, particularly in the C-band spectral region. Given the cost and physical limitations (such as size and weight) of traditional solutions like Optical Spectrum Analyzers (OSA), the development of low-cost approaches for LPFG spectral analysis became an important topic that needed further development. The development of a simple curve fitting routine for LPFG spectra is reported in this article, along with a framework for automatic detection of certain physical phenomena such as corrosion and the presence of chemical species, among others.

Abstract
The ability to select, isolate, and manipulate micron-sized particles or small clusters has made optical tweezers one of the emergent tools for modern biotechnology. In conventional setups, the classification of the trapped specimen is usually achieved through the acquired image, the scattered signal, or additional information such as Raman spectroscopy. In this work, we propose a solution that uses the temporal data signal from the scattering process of the trapping laser, acquired with a quadrant photodetector. Our methodology rests on a pre-processing strategy that combines Fourier transform and principal component analysis to reduce the dimension of the data and perform relevant feature extraction. Testing a wide range of standard machine learning algorithms, it is shown that this methodology allows achieving accuracy performances around 90%, validating the concept of using the temporal dynamics of the scattering signal for the classification task. Achieved with 500 millisecond signals and leveraging on methods of low computational footprint, the results presented pave the way for the deployment of alternative and faster classification methodologies in optical trapping technologies.