High temperature measurements using femtosecond written FBGs of a titanium substrate under intense heat flow

Pairs of arrays of point-by-point fiber Bragg Gratings written with a femtosecond laser were anchored with K-type thermocouple within an asymmetrical titanium substrate. Three anchoring methods were used, including silica based, graphite based glue commercially available as well as Yttria Stabilized Zirconia deposited by Atmospheric Plasma Spraying. The optical fibers were first recoated with an inorganic coating, specifically developed to resist to high temperatures above 800°C. The titanium plate was exposed to an intense heat flow delivered by tungsten halogen lamps to reach temperature of around 800°C. High temperature and strain measurements was performed in situ with a relative error of less than 10% at 800°C.