A sapphire fiber thermal probe with Cr3+ ion-doped end was grown using the laser heated pedestal method. The fluorescence thermal probe offers advantages of compact structure, high performance and the ability to sustain high temperature from the room temperature to 450 °C. Based on the fast fourier transform (FFT), the fluorescence lifetime is obtained from the tangent function of the phase angle of the first non-zeroth item of FFT result. Compared with other traditional fitting methods, our method has advantages such as fast speed, high accuracy and being free from the influence of the base signal. The standard deviation of FFT method is about half of that of the Prony method and close to the one of the Marquardt method. In addition, since the FFT method is immunity to the background noise of the signal, the background noise analysis can be skipped.
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