Abstract: A method for tuning a distributed acoustic sensing (DAS) system. The method may include determining a signal strength from a first Raman Pump in the DAS system, sweeping a laser pulse output from a transmitter; wherein the sweeping is an incremental increase of a power of the laser pulse output from a minimum pulse power to a maximum pulse power, and measuring a first signal-to-noise-ratio (SNR) for each of the incremental increase of the power of the laser pulse output. The method may further comprise selecting a maximum SNR from the first SNR for each of the incremental increase of the power of the laser pulse output and configuring the first Raman Pump and the laser pulse output based at least in part on the maximum SNR.

Abstract: A fiber optic sensing (FOS) system may include a Brillouin Optical Time Domain Analyzer (BOTDA) unit, a first fiber optical cable optically connected to the BOTDA interrogator unit at a first end, and an optical feedthrough system (OFS) optically connected the first fiber optical cable at a second end of the first fiber optical cable. The FOS system may further comprise a fiber optic cable forming a loop within a wellbore that is optically connected to the first fiber optical cable at the OFS and a second fiber optical cable optically connected to the loop at the OFS and wherein the second fiber optical cable is optically connected to the BOTDA interrogator unit.

Abstract: A method, includes: detecting one or more properties of a waveguide having a downhole end and an uphole end; and responsive to the detected one or more properties, positioning into a passage of a wellbore the waveguide to minimize tension thereof.

Abstract: A fiber optic sensing (FOS) system may include a Brillouin Optical Time Domain Analyzer (BOTDA) unit, a first fiber optical cable optically connected to the BOTDA interrogator unit at a first end, and an optical feedthrough system (OFS) optically connected the first fiber optical cable at a second end of the first fiber optical cable. The FOS system may further comprise a fiber optic cable forming a loop within a wellbore that is optically connected to the first fiber optical cable at the OFS and a second fiber optical cable optically connected to the loop at the OFS and wherein the second fiber optical cable is optically connected to the BOTDA interrogator unit.

Abstract: A method and system for fiber optic communication and sensing (FOCS) may include transmitting one or more measurement signals from an interrogator unit that is optically connected to a proximal wavelength division multiplexer (WDM), transmitting one or more communication signals from an information handling system that is optically connected to a proximal wavelength division multiplexer (WDM), multiplexing the one or more measurement signals and the one or more communication signals with the proximal WDM into a first fiber optic cable, and receiving the one or more measurement signals and the one or more communication signals with a distal WDM that is optically connected to the first fiber optic cable. The method may further include multiplexing the one or more measurement signals from the first fiber optic cable into one or more downhole sensing fibers and receiving backscatter light from at least one of the one or more downhole sensing fibers.

Abstract: A method for distributed acoustic sensing includes sending a first optical pulse down an optical fiber, wherein light from the first optical pulse is backscattered from positions along a length of the optical fiber according to coherent Rayleigh scattering; splitting backscattered light from the first optical pulse into a first portion for a first interferometer and a second portion for a second interferometer, the first interferometer having a first gauge length and the second interferometer having a second gauge length, wherein the first gauge length is different from the second gauge length; detecting a first interferometric signal from the first interferometer responsive to the first portion of backscattered light; detecting a second interferometric signal from the first interferometer responsive to the second portion of backscattered light; and processing the first and second interferometric signals for two different sensing applications adapted for the first and second gauge lengths, respectively.

Abstract: A backscattered signal can be received from a sensing fiber that extends into a wellbore. The backscattered signal can have been generated based on an optical signal launched into the sensing fiber. A first delayed signal, a second delayed signal, a first non-delayed signal, and a second non-delayed signal can be generated from the backscattered signal. A polarization control device can shift a polarization of the first delayed signal or the first non-delayed signal. A first demodulated signal can be determined based on the first delayed signal and the first non-delayed signal. A second demodulated signal can be determined based on the second delayed signal and the second non-delayed signal. Data about an environment of the wellbore can be determined by processing the first demodulated signal and the second demodulated signal to compensate for noise in the first demodulated signal or the second demodulated signal.

Abstract: An interrogation system includes a light signal switch and a reflection signal switch. The light signal switch may be communicatively coupled to an optical light source. The light signal switch may route a light signal generated by the light source downhole in a wellbore through a single-mode optical fiber cable or a multi-mode optical fiber cable. The reflection signal switch may be communicatively coupled to the single-mode optical fiber cable and the multi-mode optical fiber cable. The reflection signal switch may route a reflection of the light signal from the signal-mode optical fiber cable or the multi-mode optical fiber cable to an optical detector.

Abstract: A backscattered signal can be received from a sensing fiber that extends into a wellbore. The backscattered signal can have been generated based on an optical signal launched into the sensing fiber. A first delayed signal, a second delayed signal, a first non-delayed signal, and a second non-delayed signal can be generated from the backscattered signal. A polarization control device can shift a polarization of the first delayed signal or the first non-delayed signal. A first demodulated signal can be determined based on the first delayed signal and the first non-delayed signal. A second demodulated signal can be determined based on the second delayed signal and the second non-delayed signal. Data about an environment of the wellbore can be determined by processing the first demodulated signal and the second demodulated signal to compensate for noise in the first demodulated signal or the second demodulated signal.

Abstract: An interrogation system includes a light signal switch and a reflection signal switch. The light signal switch may be communicatively coupled to an optical light source. The light signal switch may route a light signal generated by the light source downhole in a wellbore through a single-mode optical fiber cable or a multi-mode optical fiber cable. The reflection signal switch may be communicatively coupled to the single-mode optical fiber cable and the multi-mode optical fiber cable. The reflection signal switch may route a reflection of the light signal from the signal-mode optical fiber cable or the multi-mode optical fiber cable to an optical detector.

Abstract: Systems and methods for distributed acoustic sensing based on coherent Rayleigh scattering are disclosed herein. A system comprises a pulse generator, an interferometer, a photo detector assembly, and an information handling system. The interferometer comprises a first and second optical switch each comprising a plurality of ports. The information handling system activates one port on each of the first and second optical switches so as to vary the optical path length of the interferometer. A method comprises splitting backscattered light from an optical pulse into a first portion and a second portion, activating one port of a first optical switch and one port of a second optical switch, sending the first portion into a first arm of an interferometer, sending the second portion into a second arm of the interferometer, combining the first and second portions to form an interferometric signal, and receiving the interferometric signal at a photodetector assembly.

Abstract: A distributed acoustic sensing system for use in a wellbore can include a shutter positioned between an amplifier and an optical-wave flow controller of the distributed acoustic sensing system for reducing optical noise in the distributed acoustic sensing system. The distributed acoustic sensing system can also include a controller operable to transmit a signal to the shutter to (i) open the shutter for allowing an optical pulse to transmit through the shutter, and (ii) close the shutter for preventing an extraneous optical waveform, that generates at least a portion of the optical noise, from transmitting through the shutter.

Abstract: Systems and methods for distributed acoustic sensing based on coherent Rayleigh scattering are disclosed herein. A system comprises a pulse generator, an interferometer, a photo detector assembly, and an information handling system. The interferometer comprises a first and second optical switch each comprising a plurality of ports. The information handling system activates one port on each of the first and second optical switches so as to vary the optical path length of the interferometer. A method comprises splitting backscattered light from an optical pulse into a first portion and a second portion, activating one port of a first optical switch and one port of a second optical switch, sending the first portion into a first arm of an interferometer, sending the second portion into a second arm of the interferometer, combining the first and second portions to form an interferometric signal, and receiving the interferometric signal at a photodetector assembly.