Fabrication of long-period fiber gratings by CO2 laser irradiations for high temperature applications

We report in this paper the fabrication of high performance thermal LPFGs by point-by-point CO2 laser irradiations. These thermal LPFGs have shown much better temperature tolerance and promised applications in high temperature harsh environments. The computer-controlled fabrication system with in situ signal monitoring capability is described. The fabricated LPFGs survived high temperatures up to 800 degrees C. Long term stability test at 550 degrees C for 200 hours indicated that thermal shock at a higher temperature could significantly reduce the drift.