Dynamic sensitivity distributed acoustic sensing

Abstract

Provided is a method for determining strain change in an optical fiber. The method includes injecting pulsed radiation into the optical fiber; interfering the radiation backscattered from plural locations within the fiber with reference radiation; detecting plural intensities of the interfered radiation associated with the plural locations; deriving plural temporal phase changes based on the plural intensities; for any target location along the fiber: setting a variable first aggregation range and/or second aggregation range to respective start aggregation range values; a) deriving a first phase aggregation value based on plural temporal phase changes of radiation returning from the first aggregation range including locations behind the target location; b) deriving a second phase aggregation value based on plural temporal phase changes of radiation travelled to a second aggregation range including locations in front of the target location; c) determining a signal (strain indicative value) associated with the target location based on a phase aggregation value difference between the first phase aggregation value and second phase aggregation value; performing the above steps a), b), c) while varying the first and/or second aggregation range values to respective final aggregation range values until a criterion is satisfied.