Fictive temperature distribution in highly Ge-doped multimode optical fibers

In this study, FTIR FPA (focal plan array) detector was used to image the 'bond-stretching' vibration mode observed near σ = 1120 cm−1 of highly Ge-doped graded index multimode optical fibers (GI-MMF). Next, as calibration curves between σ and the fictive temperature Tf are not available in the literature for highly Ge-doped glasses (above 7 wt%), we have determined our own calibration curves from 1 to 30 wt% in Ge. Then, we have applied these corrections to our σ measurements in GI-MMF in order to estimate, for the first time to our knowledge, the fictive temperature distribution within MMF cross-section.