Over the past decade, researchers in the oil and gas industry developed a technique, distributed acoustic sensing (DAS), to solve a range of on- and offshore reservoir imaging problems. In essence, DAS transforms a straight fiber-optic cable into a one-dimensional array of strain-rate sensors. Here’s how: An electro-optic device illuminates one end of the fiber with short light pulses and performs interferometry on any photons that are backscattered from microscopic heterogeneities in the fiber’s glass core. The interferometric signal changes if the fiber undergoes local strain. By recording the photons’ return times, the device determines the position of any linear stretch or compression on the cable. And by repeatedly firing pulses into the fiber, it can resolve the speed of sound waves.
A team of researchers led by Nate Lindsey (University of California, Berkeley, and Lawrence Berkeley National Laboratory) and Eileen Martin (Stanford University) has now demonstrated that DAS can...
