All-fiber system for simultaneous interrogation of distributed strain and temperature sensing by spontaneous Brillouin scattering

Abstract

We demonstrate a low-loss, long-range, single-ended distributed optical fiber sensor to measure both temperature and strain simultaneously and unambiguously. By using the Landau¿Placzek ratio and cascaded Mach¿Zehnder interferometric filters, we measure both the intensity and the frequency changes in the Brillouin backscattered signal. Strain and temperature measurements can then be independently resolved. A temperature resolution of 4 degrees C, a strain resolution of 290 muepsilon, and a spatial resolution of 10 m have been achieved for a sensing length of 15 km.

Dependence of the Brillouin frequency shift on strain and temperature in a photonic crystal fiber

“…To compare with the results for a single -mode fiber [ϳ4.1 ± C and ϳ140 me (Ref. 9) with 10-m spatial resolution 6 ], our results show similar temperature but better strain accuracy and higher spatial resolution. This comparison clearly demonstrates the ability of our system to measure temperature and strain simultaneously.…”

“…4 One could then subtract the frequency shift that resulted from any temperature effects from the combined frequency shift to determine the strain on the structure. This method was used to measure strain and temperature with a spatial resolution of 5 m. As a second solution to this problem, interest was focused on both Brillouin backscattered intensity and frequency shifts, 5,6 because they both exhibit dependence on strain and temperature. However, the spatial resolution achieved is tens of meters because of power (intensity) f luctuations induced by lasers and by the accuracy of intensity measurement.…”

Application of Distributed Optical Fiber Sensing Technology in Surrounding Rock Deformation Control of TBM-Excavated Coal Mine Roadway

“…Optical Fiber Sensor. The fiber sensors are capable of sensing the temperature and strain over long distances [29,30]. While the bare optical fibers are usually used in laboratory tests because they are easily fractured under the deformation of measured structures.…”

Nonlinear Scattering Effects in Optical Fibers

“…The fiber sensors are capable of sensing the temperature and strain over long distances [17,18]. Whenever there is change in temperature or strain, the refractive index of silica changes in response to such variations.…”