Journal: IEEE Journal of Quantum Electronics
Paper: Comparison of the stability of ring resonator structures for multiwavelength fiber lasers using Ramanor Er-doped fiber amplification

AUTHORS: Montserrat Fenandez-Vallejo, Silvia Diaz, Rosa Ana Perez-Herrera, Ruth Unzu, M.A. Quintela, José Miguel López-Higuera, Manuel López-Amo
Abstracts:
An experimental comparison of the stability performance of two multiwavelength lasers, based on either an erbium-doped fiber or Raman amplification, is reported. Both systems employ fiber Bragg gratings to select the operating wavelengths within the resonant ring cavity. The aim of this work is to compare the output power stability of the lasers and also their optical signal-to-noise ratios.

Journal: Journal of Lightwave Techology
Paper: Stability Comparison of Two Ring Resonator Structures for Multiwavelenghth Fiber Lasers Using Highly Doped Er-Fibers

AUTHORS: Rosa Ana Pérez-Herrera; M. Angeles Quintela, Montserrat Fernández-Vallejo, Antonio Quintela, Manuel López-Amo, Jose Miguel López-Higuera
Abstracts:
An experimental comparison of stability between two different fiber laser topologies is carried out. The lasers are based on ring resonators that include highly doped Er-fibers. Both topologies use fiber Bragg grating reflectors in order to select the emission wavelengths. The experimental results confirms that the novel topology based on fiber optic circulators arranged in a hybrid serial-parallel configuration offers better stability and a higher optical signal-to-noise ratio (OSNR) than the simpler one based on a parallel configuration.

Journal: Sensors
Paper: Use of the plasma spectrum RMS signal for arc-welding diagnostics

AUTHORS: J. Mirapeix, A. Cobo, J. Fuentes, M. Davila, J.M. Etayo, J.M. López-Higuera
Abstracts:
A new spectroscopic parameter is used in this paper for on-line arc-welding quality monitoring. Plasma spectroscopy applied to welding diagnostics has typically relied on the estimation of the plasma electronic temperature, as there is a known correlation between this parameter and the quality of the seams. However, the practical use of this parameter gives rise to some uncertainties that could provoke ambiguous results. For an efficient on-line welding monitoring system, it is essential to prevent the appearance of false alarms, as well as to detect all the possible defects. In this regard, we propose the use of the root mean square signal of the welding plasma spectra, as this parameter will be proved to exhibit a good correlation with the quality of the resulting seams. Results corresponding to several arc-welding field tests performed on Inconel and titanium specimens will be discussed and compared to non-destructive evaluation techniques.

Journal: Electronics Letters
Paper: Technique to develop active devices by modifying Brillouin gain spectrum

AUTHORS: C.A. Galindez, F.J. Madruga, A. Ullan, J.M. Lopez-Higuera
Abstracts:
A simple technique to reshape the Brillouin gain spectrum is based on the superposition of the Brillouin scattering spectra from several concatenated optical fibres. Different and well defined Brillouin gain pectra can be obtained from each single mode fibre, when they are pumped at the same optical pump radiation. Furthermore, with this technique, a customized Brillouin gain spectral response can be obtained by choosing the single mode fibres properly. Thus, actives devices such as filters, amplifiers and lasers with narrow band and customized band can be developed. To check experimentally our idea, we proposed and demonstrated an active device with a like “M” spectral response, with a bandwidth of 280 MHz at 3dB and a reject band placed in 10.78GHz from the pump wavelength. We used four different pieces of single mode fibre with 5m long each.