Phosphorous doping and drawing effects on the Raman spectroscopic properties of O=P bond in silica-based fiber and preform.

We report an experimental study of the doping and drawing effects on the Raman activities of phosphorus (P)-doped silica-based optical fiber and its related preform. Our data reveal a high sensitivity level in the full width at half maximum value of the 1330 cm-1 (O=P) Raman band to the P-doping level. Its increase with the P doping level does not clash with an increase in the disorder of the O=P surrendering matrix. In addition, we observe that in the central core region of the sample (higher doping level), the drawing process decreases the relative band amplitude. We tentatively suggest that this phenomenon is due to the change in the first derivate of the bond polarizability as a function of the normal vibration coordinates.