Abstract: The spatial resolution of a fiber optical Distributed Acoustic Sensing (DAS) assembly is enhanced by: arranging an optical DAS fiber with a series of contiguous channels that are sensitive to vibration in a U-shaped loop such that substantially parallel fiber sections include pairs of channels that are arranged at least partially side by side; transmitting a series of light pulses through the optical fiber and receiving back reflections of said light pulses by a light transmission and receiving assembly; and processing the received back reflections such that back reflections stemming from at least one pair of channels that are arranged at least partially side by side are correlated to each other.

Abstract: The spatial resolution of a fiber optical Distributed Acoustic Sensing (DAS) assembly is enhanced by: arranging an optical DAS fiber (1) with a series of contiguous channels (C1-C14) that are sensitive to vibration in a U-shaped loop (U1) such that substantially parallel fiber sections (IA, IB) comprise pairs of channels (C1&C14, C2&C13,C3&C12 . . . etc) that are arranged at least partially side by side; transmitting a series of light pulses (5A, 5B) through the optical fiber (1) and receiving back reflections (6A, 6B) of said light pulses (5A, 5B) by a light transmission and receiving assembly (7); and processing the received back reflections (6A, 6B) such that back reflections stemming from at least one pair of channels (C1, C14; C2,C13) that are arranged at least partially side by side are correlated to each other.