Sebastián Jarabo

Multiwavelength fiber laser sources with Bragg-grating sensor multiplexing capability

Two erbium-doped fiber ring lasers (EDFRLs) wvith simultaneous emission at four different wavelengths are demonstrated. Both systems employ fiber Bragg gratings (FBGs) to select the operation wavelengths within the ring. The sensing capability of the FBGs has been taken advantage of, allowing for the sources to be used as sensor multiplexing schemes. The first system employs four FBGs in a tree filter topology, achieving four output channels with -5 dBm power each. The second system comprises an in-line filtering topology with active fiber segments within the filter. This second source yields 2-dBm output signals and allows for a higher number of lines to be easily added to the system. A comparison between both topologies is carried out, and their capability for sensor multiplexing is demonstrated.

New WDM amplified network for optical sensor multiplexing

A wavelength-division-multiplexing system for optical sensors with hybrid star-bus topology is shown experimentally. The star section of the network is formed by an erbium-doped fiber ring laser used as simultaneous-multiple-wavelength-operation source and distribution scheme. This topology is compared to an amplified double-bus configuration with a single-wavelength tunable source. Signal power, signal-to-noise ratio, and crosstalk are analyzed for both structures. Practical limitations of both schemes are also discussed.

Erbium-doped silica fiber modeling with overlapping factors

A simple model describing the evolution of pump, signal, and amplified spontaneous emission powers in an erbium-doped silica fiber is presented. The model is based on overlapping factors, depending on pump- and signal-coupled powers, which are systematically studied. Accurate results for gain and amplified spontaneous emission are obtained when this model is used. Experiments to measure the characteristic parameters of the fiber appearing in the model are described. Two main advantages of this model are found: computation time is considerably reduced and fiber characterization does not make it necessary to measure the parameters of the fiber as a function of radial or azimuthal coordinates.

Analytic modeling of erbium-doped fiber amplifiers on the basis of intensity-dependent overlapping factors

Rate equations based on intensity-dependent overlapping factors are integrated to obtain analytic solutions for pump, signal, and amplified spontaneous emission (ASE), even when the coupled signal varies with time. The equations can be applied without the imposition of any restraints on the values of the pump, signal, and ASE powers, the excited-state-absorption cross section, the erbium-density distribution, or other parameters that characterize the fiber. The methods used to calculate pump, signal, and ASE powers are discussed. Experimental techniques to characterize the doped fiber that were based on these analytic expressions are introduced.

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.

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.

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.

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.

Experimental verification of analytic modeling of erbium-doped silica fiber amplifiers pumped at 1480 nm

Gain measurements are carried out for different lengths of three types of erbium-doped silica fiber with different pump powers at 1480 nm. From these measurements a relation is established for each type of fiber between gain and the attenuation factor of the pump power. This relation is in complete agreement with the one predicted by an analytic model based on overlapping factors, which makes it possible to obtain methods for the experimental characterization of doped fibers.

Spectral hole burning induced by reflected amplified spontaneous emission in erbium-doped silica optical fiber pumped at 980 nm

We applied an erbrium-doped fiber amplifier characterization method previously reported for 1480-nm pumped amplifiers to a 980-nm amplifier, obtaining absorption and emission coefficients, as well as the dopant concentration in fiber. Gain and fluorescence (amplified spontaneous emission) simulations performed from the obtained features agree well with experimental results. Nevertheless, at certain high-gain circumstances, disagreements appear in the form of spectral hole burning, which can present high magnitudes and whose nature is discussed.