Amplificador y láser de fibra óptica de sílice dopada con tulio

En este trabajo se presenta un láser de fibra dopada con tulio en cavidad de anillo, operando en modo continuo. El bombeo se realiza en la zona de 1600 nm mediante láseres de fibra dopada con erbio. Se ha estudiado el comportamiento con bombeo en modo continuo y en modo pulsado, obteniendo unas eficiencias del 35% y del 38%, respectivamente. Estas eficiencias son superiores a las típicas que se consiguen bombeando en 1600 nm. El láser emite en dos longitudes de onda separadas unos pocos nanómetros, situadas entre 1910 nm y 1920 nm. Al mismo tiempo, se presentan también medidas de ganancia espectral de la fibra dopada con tulio. A modo de ejemplo, se ha realizado un amplificador de fibra dopada con tulio y se ha demostrado su viabilidad amplificando un espectro supercontinuo en la región comprendida entre 1800 nm y 2000 nm, el cual podría utilizarse para bombear fibras no lineales cuya longitud de onda de dispersión cero esté situada en dicha región espectral

A reliable criterion for the correct delimitation of the foveal avascular zone in diabetic patients

Background: Manual segmentation of the Foveal Avascular Zone (FAZ) has a high level of variability. Research into retinas needs coherent segmentation sets with low variability. Methods: Retinal optical coherence tomography angiography (OCTA) images from type-1 diabetes mellitus (DM1), type-2 diabetes mellitus (DM2) and healthy patients were included. Superficial (SCP) and deep (DCP) capillary plexus FAZs were manually segmented by different observers. After comparing the results, a new criterion was established to reduce variability in the segmentations. The FAZ area and acircularity were also studied. Results: The new segmentation criterion produces smaller areas (closer to the real FAZ) with lower variability than the different criteria of the explorers in both plexuses for the three groups. This was particularly noticeable for the DM2 group with damaged retinas. The acircularity values were also slightly reduced with the final criterion in all groups. The FAZ areas with lower values showed slightly higher acircularity values. We also have a consistent and coherent set of segmentations with which to continue our research. Conclusions: Manual segmentations of FAZ are generally carried out with little attention to the consistency of the measurements. A novel criterion for segmenting the FAZ allows segmentations made by different observers to be more similar