Peculiarities of the photosensitivity of low-loss phosphosilica fibres

The peculiarities of the refractive-index change in low-loss heavily P₂O₅-doped silica fibres fabricated by the MCVD method caused by irradiation with UV light are studied. The pre-exposure effect is found in these fibres. The mechanisms of the refractive-index change in phosphosilica and germanosilica fibres are considered and compared in the presence of this effect.