J. M. Alvarez

Nonlinear response of a unidirectional erbium-doped fiber ring laser to a sinusoidally modulated pump power

The response of a unidirectional erbium-doped fiber ring laser, excited by a sinusoidally modulated pump power, is analyzed both experimentally and theoretically. Experimentally, several resonance peaks are observed, as well as different frequency ranges showing bistable behaviour. Appearance of all resonance peaks obtained can be explained taking into account simple relations between the pump modulation frequency and the system natural frequency. Theoretically, it is shown how a model which combines the theory of erbium-doped fibers and the semiclassical laser treatment can account for all phenomena observed, with good agreement. In particular, it is demonstrated that a correct description of the bistable regions requires taking into account powers and population distributions along the laser active medium.

Erbium doped fibre characterisation by laser transient behaviour analysis

A procedure to extract spectroscopic information from erbium doped fibres (EDF), based on transient laser behaviour analysis, is presented. It achieves a complete characterisation of EDF on wavelengths corresponding to pump and laser emission, obtaining respective absorption and emission coefficients. In addition, it allows to perform predictions of some laser dynamics features, which exhibit good experimental agreement.

980 and 1480 nm EDF characterisation by ring tunable laser dynamic study

Abstract An EDF characterisation method, based on laser transient behaviour, is applied to 980 and 1480 nm pumped ring tunable fibre lasers. Absorption and emission coefficients at both, pump and laser frequencies, along the 1521–1561 nm spectral range, are obtained, as well as dopant concentration. Obtained parameters are introduced in EDF amplifier (EDFA) simulation in order to check them out, presenting good agreement with experimental measurements.

Experimental cross sections of erbium-doped silica fibers pumped at 1480 nm

Absorption and stimulated emission coefficients for a pump power at 1480 nm are determined experimentally for three types of erbium-doped silica fiber. Starting from these coefficients and using previous gain measurements, we calculate absorption and stimulated emission cross sections of the erbium laser transition. The results obtained are in good agreement with the ones that appear in the literature.

Velocity resolution in laser Doppler velocimetry experiments by measuring the Fourier transform of the time-interval probability

Abstract In this paper the resolving power of the Fourier transform of the time-interval probability technique is studied when it is used in a laser Doppler velocimetry experiment to measure a non-steady fluid velocity. It is concluded that for small values of the scattered intensity, differences of velocities as little as 2% can be resolved with a small error.

Erbium-doped fiber characterization by fluorescence dynamics measurement

A technique for erbium-doped fiber characterization is presented. Its foundation lies in the study of the transversal and copropagating fluorescence time evolution when pumping is switched on and off. A model that describes these phenomena is developed, and experimental results, in good agreement with the model, are shown. The stimulated emission cross sections and an effective erbium-density distribution are determined from the measurements.

Erbium-Doped-Silica Photonic Crystal Fiber Characterization Method: Description and Experimental Check

The present paper reports and discusses a characterization method for erbium-doped-silica photonic crystal fibers based on the measurement of pump power attenuation and gain together with the McCumber theory. The absorption and emission cross sections and the passive losses of the fiber were obtained from a fitting procedure of theoretical to experimental values. The method was checked by means of a home-made photonic crystal fiber to verify its reliability. Finally, it was found that the characteristic parameters obtained by this method can be used to accurately simulate the performance of the fiber and therefore to design devices based on it.

Analysis of theoretical models for erbium-doped silica fibre lasers

A theoretical model for erbium-doped silica fibre lasers including the power modal distribution is developed. Using overlapping factors, an alternative theoretical model is proposed where analytical equations are obtained. The lasing wavelength is found without the requirement of being established beforehand by means of filters. Moreover, the theoretical model based on one overlapping factor is now solved using a new method based on a parameterised analytical pump power evolution, providing directly the laser wavelength as well as more accurate fluorescence spectra combined with very short computation times. Finally a combined model is also developed to provide solutions of the standard model with serious improvements in accuracy and computation time.

Comparison between intensity correlation and Fourier transform of the time interval probability techniques applied to laser Doppler velocimetry

In this paper we study the improvement in a laser Doppler velocimetry experiment when the Fourier transform of the time interval probability is measured instead of the intensity correlation function. The errors involved in determination of the velocity are found to be greatly improved for low scattered intensities.

New theoretical model based on the application of the energy conservation principle for erbium-doped silica fibre lasers

A new theoretical model based on the standard-model equations but ensuring conservation of energy by accounting for the optical powers stored in the laser cavity is presented. This model succeeds in grouping two sorts of previous models: those based on standard equations and those based on conservation of number of photons. Furthermore, it provides a more complete quantitative description of EDSFLs (erbium-doped silica fibre lasers) and also improves the qualitative description of these devices by including the spontaneous emission terms and by determining the optical powers involved as well as the oscillation wavelength. The possibility of solving the EDSFL system including the power modal distribution within the fibre is also considered. Finally, a detailed comparison between this model and the models proposed by other authors is shown, where it is proved that the new model describes much better the behaviour of EDSFLs.