Abstract
A simple interrogation technique for refractive index measurement is proposed, using a multimode interference-based fiber tip structure. The fiber probe is a section of a multimode fiber, spliced to a single-mode fiber and interrogated in reflection. The interrogation technique uses two fiber Bragg gratings as discrete optical sources; by means of relative intensity variation of the reflected signals, those sources will provide a measurement of refractive index changes, while taking advantage of the MMI-based fiber tip. The read-out system uses a WDM and two photodetectors to separate both signals. A sensitivity of -5.87/RIU, in the refractive index range 1.30-1.38, was achieved with the proposed configuration.

Abstract
An optical fiber sensor based on a tapered-FBG coated with 150 nm-thick Pd film is proposed for hydrogen pressure detection. The FBG was written in a 50 µm-diameter tapered fiber by DUV femtosecond laser technology. A second FBG was inscribed in the untapered fiber region for temperature compensation. The sensing head was able to detect the variation of hydrogen pressure in the range 0-780 kPa and a maximum sensitivity of 0.15 pm/kPa was achieved. © 2012 OSA.

Abstract
The refractometric analysis of ethanol-water mixtures is hampered because this type of binary solution does not present a linear behavior. In this letter, a multimode graded-index fiber (GIF) tip sensor for the measurement of ethanol in binary liquid solutions of ethanol-water is proposed. The proof is fabricated by the fusion-splicing of a 500 mu m GIF to a single-mode fiber (SMF), and it operates as a refractometric sensor in reflection. To evaluate the prove potential to detected ethanol variations, samples of ethanol-water mixtures were measured at different temperatures (20 degrees C-60 degrees C). The samples have different %(v/v) of ethanol, in a range between 0% and 100%.

Abstract
The use of graphene oxide (GO) as a saturable absorber for short pulses generation in an Erbium-doped fiber laser was studied and demonstrated. The saturable absorber consisted of a thin GO film, with a high concentration of monolayer GO flakes, spray-coated on the end face of a ferrule-connected fiber. By including the saturable absorber in the laser cavity and controlling the intra-cavity polarization, the generation of shortpulsed light was achieved under mode-locking and Q-switching operations. Under mode-locking operation, it was observed a pulse train with a fundamental repetition rate of 1.48 MHz, with a working wavelength centered at 1564.4 nm. In the Q-switch operation, a pulse train with a 12.7 kHz repetition rate and a 14.3 µs pulse duration was attained for a 230-mA pump current. Further investigation showed a linear dependence of the repetition rate with the pump power, attaining frequencies between 12.7 and 14.4 kHz. © 2023 by SCITEPRESS - Science and Technology Publications, Lda.

Abstract
Measuring gas and liquid flow rate is paramount in various scientific and industrial applications. This work presents an optical fiber flowmeter based on a graphene oxide (GO) coated Michelson interferometer. The interferometer is fabricated using a long-period fiber grating (LPFG) followed by a GO-coated single-mode fiber (SMF). By radiating the GO coating, it experiences photothermic effect that induces local heating of the film. This results in a variation in the effective refractive index in the cladding modes, which induces a phase shift on the interferometer spectrum. When a gas flow is introduced near the coated fiber, the hot-wire region will experience a reduction in temperature proportional to the flow rate. The flowmeter exhibited a linear wavelength shift to the flow rate with an absolute sensitivity of 17.4 +/- 0.8 pm/(L.min-1) for gas flow rates between 2 and 8 L/ min. Furthermore, the dynamic response of the sensor was studied, attaining a maximum response time of 1.1 +/- 0.4 s

Abstract
Ethionamide (ETH) is an important second-line antituberculosis drug used for the treatment of patients infected with multidrug-resistant Mycobacterium tuberculosis. Recently, we reported that the loading of ETH into thermally carbonized-porous silicon (TCPSi) nanoparticles enhanced the solubility and permeability of ETH at different pH-values and also increased its metabolization process. Based on these results, we synthesized carboxylic acid functionalized thermally hydrocarbonized porous silicon nanoparticles (UnTHCPSi NPs) conjugated with ETH and its antimicrobial effect was evaluated against Mycobacterium tuberculosis strain H37Rv. The activity of the conjugate was increased when compared to free-ETH, which suggests that the nature of the synergy between the NPs and ETH is likely due to the weakening of the bacterial cell wall that improves conjugate-penetration. These ETH-conjugated NPs have great potential in reducing dosing frequency of ETH in the treatment of multidrug-resistant tuberculosis (MDR-TB).