Brillouin distributed optical fiber sensing system based on spontaneous Brillouin intensity measurement may measure temperature in the optical fiber, due to the dependence of spontaneous Brillouin scattering intensity on temperature. In this paper, a 4.25km distributed optical fiber temperature sensing experiment system was demonstrated. Using the experiment system, we obtained the traces of spontaneous Brillouin scattering intensity as the sensing fiber was not heated and heated respectively. By normalizing the trace of the fiber being heated to the trace of the fiber not being heated, the intensity change of spontaneous Brillouin scattering corresponding to temperature along the fiber has been obtained. And there was a good
agree between the result and the heated section of the fiber.