Fiber Bragg grating-based thermometer for drill bit temperature monitoring.

The temperature measurement of a drill bit during an implantology drilling process is proposed by using a fiber Bragg grating fitted inside the drill bit. Due to the rotational nature of the drilling process, a free-space fiber-optic rotary joint is used for interrogating the fiber Bragg grating. Due to mechanical clearances and interferometric noise induced at this rotary joint, signal integrity is strongly deteriorated and is not workable without adequate measures. These measures involve a proper fiber lensing and a signal processing in order to remove the interferometric noise. Finally, a heating measurement on an implantology drill bit is performed and discussed for drilling several holes on a pork jaw sample.