Erbium-doped aluminophosphosilicate optical fibres

We have studied the active properties of erbium-doped aluminophosphosilicate (APS) core fibres in wide ranges of erbia, alumina and phosphorus pentoxide concentrations. The absorption and luminescence spectra of the P₂O₅- or Al₂O₃-enriched erbium-doped APS fibres are shown to be similar to those of the erbium-doped fibres singly doped with phosphorus pentoxide or alumina, respectively. The formation of AlPO₄ in APS fibres leads not only to a reduction in the refractive index of the glass but also to a marked increase in Er₂O₃ solubility in silica.