Transient response of buried oil pipelines fiber optic leak detector based on the distributed temperature measurement

Oil leakage of transportation pipelines causes a change in its environmental temperature. This effect is employed to detect the leakage and its positions. The Raman Optical Time Domain Reflectometer (ROTDR) and Brillouin Optical Time Domain Amplifier (BOTDA) sensors are two of the most precise oil pipeline leak detector systems operate based on this effect. The position of leakage is determined by the time difference between the sending and backscattered laser pulses. In this paper, the transient response of BOTDA and ROTDR sensors are obtained through solution of the mass, energy and heat transfer in soil and fiber cable. It is shown that the mechanical rise time is of the order of a few minutes, which is in agreement with the experimental results of BOTDA and ROTDR sensors. Ultimately, on the basis of the heat transfer results, a method for leak flow rate measurement by the optical fiber leak sensors is proposed.