Fabricating in fiber gratings in single crystal sapphire fiber

In this paper, we propose an innovative extremely harsh environment (up to 2000 degreesC) distributed temperature sensor by fabricating in-fiber gratings in single crystal sapphire fibers. Temperature is sensed by changing grating optical spectral response. By cascading a set of gratings in the same single crystal sapphire fiber, distributed sensing can be achieved. A quantitative analysis on grating design, fabrication, and performance is presented. Some preliminary experimental results are also reported. Application of this unique in-fiber grating to extremely harsh environment temperature sensor will be performed in the near future.