Abstract: An apparatus for detecting a location of an optical fiber having an acoustic sensor disposed subsurface to the earth includes an acoustic emitter configured to emit a first signal having a first frequency and a second signal having a second frequency that is higher than the first frequency, the first and second emitted acoustic signals being azimuthally rotated around the borehole and an optical interrogator configured to interrogate the optical fiber to receive an acoustic measurement that provides a corresponding first received signal and a corresponding second received signal. The apparatus also includes a processor configured to (i) frequency-multiply the first received signal to provide a third signal having a third frequency within a selected range of the second frequency, (ii) estimate a phase difference between the second received signal and the third signal, and (iii) correlate the phase difference to the location of the optical fiber.

Abstract: An apparatus for detecting a location of an optical fiber having an acoustic sensor disposed subsurface to the earth includes an acoustic emitter configured to emit a first signal having a first frequency and a second signal having a second frequency that is higher than the first frequency, the first and second emitted acoustic signals being azimuthally rotated around the borehole and an optical interrogator configured to interrogate the optical fiber to receive an acoustic measurement that provides a corresponding first received signal and a corresponding second received signal. The apparatus also includes a processor configured to (i) frequency-multiply the first received signal to provide a third signal having a third frequency within a selected range of the second frequency, (ii) estimate a phase difference between the second received signal and the third signal, and (iii) correlate the phase difference to the location of the optical fiber.

Abstract: A method of measuring acoustic energy impinging upon a cable includes, interrogating at least one optical fiber of the cable with electromagnetic energy, the at least one optical fiber is nonconcentrically surrounded by and strain locked to a sheath of the cable, monitoring electromagnetic energy returned in the at least one optical fiber, and determining acoustic energy impinging on the cable.

Abstract: Disclosed herein is a method for sensing one or more selected parameters related to a structure of interest, for example, the shape of an isolated structure. A cable is attached to the structure of interest at one or more attachment points. The cable contains one or more optical fibers. One or more light signals are transmitted into the one or more optical fibers and then detected to form a data set. The data set is compared with information known about the one or more attachment points to determine error values. The error values are then combined with the data set to determine the selected parameters associated with the structure.

Abstract: A method of measuring acoustic energy impinging upon a cable includes, interrogating at least one optical fiber of the cable with electromagnetic energy, the at least one optical fiber is nonconcentrically surrounded by and strain locked to a sheath of the cable, monitoring electromagnetic energy returned in the at least one optical fiber, and determining acoustic energy impinging on the cable.

Abstract: Disclosed herein is a method for sensing one or more selected parameters related to a structure of interest, for example, the shape of an isolated structure. A cable is attached to the structure of interest at one or more attachment points. The cable contains one or more optical fibers. One or more light signals are transmitted into the one or more optical fibers and then detected to form a data set. The data set is compared with information known about the one or more attachment points to determine error values. The error values are then combined with the data set to determine the selected parameters associated with the structure.

Abstract: A system and method to obtain acoustic information from a borehole penetrating the earth are described. The system includes a light source to provide a continuous output beam and a modulator to modulate the continuous output beam with a modulation signal to provide a frequency modulated continuous wave (FMCW) to be sent out on an optical fiber disposed along the borehole, the optical fiber including a plurality of reflectors at known locations along the optical fiber. The system also includes a processor to process a light reflection signal from the optical fiber to determine the acoustic information.

Abstract: A system and method to obtain an acoustic signal from a borehole penetrating the earth are described. The system includes a modulated single frequency incoherent light source to output a modulated light signal. The system also includes two or more optical fibers to split the modulated light signal for transmission to an optical sensor in the borehole, at least one of the two or more optical fibers including a delay, two or more photodetectors to receive respective resultant signals resulting from the two or more optical fibers transmitting the modulated light signal to the optical sensor, and a processor to obtain the acoustic signal based on the resultant signals.