We demonstrated the possibility to inscribe long-period fiber gratings (LPFGs) in a B/Ge codoped fiber by using grating periods shorter than 150 μm. We also have arc-induced in the SMF 28 fiber an LPFG in the dispersion turning points by using a grating period of 197 μm. In previous works, the shortest periods were, respectively, of the order of 190 and 320 μm for the same fibers. To achieve such a considerable reduction in the grating periods which enables access to the higher order cladding modes (higher sensitivity), we have developed a high-voltage power supply that allows for a constant and stable electric current ranging from 10.5 up to 21 mA. Computer simulations were used to identify the cladding mode resonances for each grating inscribed in the different fibers. The fabricated LPFGs were characterized as a function of the external refractive index from 1.33 up to 1.42, and an average refractive index sensitivity of -720 nm/RIU in the 1.33-1.41 range was obtained for a 192-μm LPFG without further optimization, such as the use of etching or thin films deposition.

This paper presents a semi-empirical fuel cell model with parameters identified using an optimization approach. The Proton Exchange Membrane Fuel Cell (PEMFC) model is characterized by technological and empirical parameters and their identification is a hard task if is intended to have precise simulation results in a wide range of operating conditions. It is verified that the Particle Swarm Optimization (PSO) method is an adequate tool to extract the correct parameter values. This is achieved minimizing the difference between experimental and simulated results. Both PEMFC model and PSO algorithm are implemented in Matlab/Simulink software.