Method and apparatuses for acoustic sensing using an optical fiber are provide. An optical fiber sensor for acoustic sensing includes an optical fiber, a laser, a pump laser pulse generator, a probe laser pulse generator, a controller, and a detector. The pump laser pulse generator is configured to receive a laser beam, from the laser, and generate a pump laser pulse. Similarly, the probe laser pulse generator is configured to receive the laser beam and generate a plurality of probe laser pulses. The controller is constructed to control the pump laser pulse generator and the probe laser pulse generator to inject the pump laser pulse and the plurality of probe laser pulses, respectively, into the optical fiber at specific timings so as to generate a plurality of Brillouin gratings at a predetermined spacing. The detector is configured to receive reflected pump laser pulses from the plurality of Brillouin gratings, respectively, and provide the reflected pump laser pulses to the controller. The duration of the pump laser pulse is greater than a duration of a probe laser pulse.