The use of reflected power spectra arising from a chirped fiber Bragg grating (CFBG) to extract a nonuniform temperature distribution along the grating has been investigated. The technique uses a discrete Fourier transform (FFT) in which the measured spectrum of the CFBG due to a localised temperature change was simulated using the FFT grating design model. The model operated on the reference spectrum and hypothesis temperature distributions, T(z), to generate a spectrum representative of a localised temperature disturbance. The simulated spectrum was fitted to the measured spectrum using a three-parameter disturbance function operating on position, width and amplitude of temperature change. The rms deviation of the applied value for position of a localised temperature change was 0.14 mm.