Abstract: Various embodiments include apparatus and methods implemented to take into consideration gauge length in optical measurements. In an embodiment, systems and methods are implemented to interrogate an optical fiber disposed in a wellbore, where the optical fiber is subjected to seismic waves, and to generate a seismic wavefield free of gauge length effect and/or to generate a prediction of a seismic wavefield of arbitrary gauge length, based on attenuation factors of a plurality of wavefields acquired from interrogating the optical fiber. In an embodiment, systems and methods are implemented to interrogate an optical fiber disposed in a wellbore, where the optical fiber is subjected to seismic waves, and to convert a seismic wavefield associated with a first gauge length to a seismic wavefield associated with a different gauge length that is a multiple of the first gauge length. Additional apparatus, systems, and methods are disclosed.

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: In some embodiments, a method and apparatus, as well as an article, may operate to determine downhole properties based on detected optical signals. An optical detection apparatus can include an optical detector including a superconducting nanowire single photon detector (SNSPD) for detecting light received at an input section of fiber optic cable. The optical detection apparatus can further include a cryogenic cooler configured to maintain the temperature of a light-sensitive region of the SNSPD within a superconducting temperature range of the SNSPD. Downhole properties are measured based on detected optical signals received at the optical detection apparatus. Additional apparatus, systems, and methods are disclosed.

Abstract: Various embodiments include apparatus and methods implemented to take into consideration gauge length in optical measurements. In an embodiment, systems and methods are implemented to interrogate an optical fiber disposed in a wellbore, where the optical fiber is subjected to seismic waves, and to generate a seismic wavefield free of gauge length effect and/or to generate a prediction of a seismic wavefield of arbitrary gauge length, based on attenuation factors of a plurality of wavefields acquired from interrogating the optical fiber. In an embodiment, systems and methods are implemented to interrogate an optical fiber disposed in a wellbore, where the optical fiber is subjected to seismic waves, and to convert a seismic wavefield associated with a first gauge length to a seismic wavefield associated with a different gauge length that is a multiple of the first gauge length. Additional apparatus, systems, and methods are disclosed.

Abstract: Various embodiments include apparatus and methods implemented to take into consideration gauge length in optical measurements. In an embodiment, systems and methods are implemented to interrogate an optical fiber disposed in a wellbore, where the optical fiber is subjected to seismic waves, and to generate a seismic wavefield free of gauge length effect and/or to generate a prediction of a seismic wavefield of arbitrary gauge length, based on attenuation factors of a plurality of wavefields acquired from interrogating the optical fiber. In an embodiment, systems and methods are implemented to interrogate an optical fiber disposed in a wellbore, where the optical fiber is subjected to seismic waves, and to convert a seismic wavefield associated with a first gauge length to a seismic wavefield associated with a different gauge length that is a multiple of the first gauge length. Additional apparatus, systems, and methods are disclosed.

Abstract: A method and system can include positioning an optical waveguide along a wellbore, and launching one or more optical signals into the waveguide at one or more optical signal frequencies and during one or more time periods, thereby resulting in one or more backscattered signals being received by the receiver, which produces a trace for each of the one of more backscattered signals. Changing an environmental condition in the wellbore, generating additional backscattered light signals at one or more frequencies after the change. Comparing the traces generated before the condition change to those generated after the change, identifying a before trace and an after trace that are substantially equal to each other and identifying a frequency difference between these traces. The frequency difference can be used to determine the amount of change in the environmental condition that occurred when the environmental change event happened.

Abstract: A cementing tool with a top seal and a bottom seal may be positionable within a casing string of a wellbore. A fiber optic line may be coupled to the top seal and to a second fiber optic line coupled to a bottom seal that is deployed within an annulus. An amplifier coupled to the cementing tool may amplify a source optical signal from a light source and a sensing measurement signal from the second fiber optic line and the first fiber optic line. One or more operational parameters, such as cementing parameters, may be adjusted based, at least in part, on the sensing measurement signal.

Abstract: Faded channels in a distributed acoustic sensing system can be mitigated using a phase modulator. A first pulse and a second pulse of an optical signal can be determined. A phase modulator can modulate the first pulse to have a different wavelength than the second pulse. The first pulse can be launched into a sensing fiber that extends into a wellbore. A first backscattered signal can be received from the sensing fiber in response to the first pulse being launched into the sensing fiber. The second pulse can be launched into the sensing fiber and a second backscattered signal can be received from the sensing fiber. Data about an environment of the wellbore can be determined by processing the first backscattered signal and the second backscattered signal to compensate for fading in the first backscattered signal or the second backscattered signal.

Abstract: A method and system can include positioning an optical waveguide along a wellbore, and launching one or more optical signals into the waveguide at one or more optical signal frequencies and during one or more time periods, thereby resulting in one or more backscattered signals being received by the receiver, which produces a trace for each of the one of more backscattered signals. Changing an environmental condition in the wellbore, generating additional backscattered light signals at one or more frequencies after the change. Comparing the traces generated before the condition change to those generated after the change, identifying a before trace and an after trace that are substantially equal to each other and identifying a frequency difference between these traces. The frequency difference can be used to determine the amount of change in the environmental condition that occurred when the environmental change event happened.

Abstract: A method and system can include positioning an optical waveguide along a wellbore, and launching one or more optical signals into the waveguide at one or more optical signal frequencies and during one or more time periods, thereby resulting in one or more backscattered signals being received by the receiver, which produces a trace for each of the one of more backscattered signals. Changing an environmental condition in the wellbore, generating additional backscattered light signals at one or more frequencies after the change. Comparing the traces generated before the condition change to those generated after the change, identifying a before trace and an after trace that are substantially equal to each other and identifying a frequency difference between these traces. The frequency difference can be used to determine the amount of change in the environmental condition that occurred when the environmental change event happened.

Abstract: A method and system can include positioning an optical waveguide along a wellbore, and launching one or more optical signals into the waveguide at one or more optical signal frequencies and during one or more time periods, thereby resulting in one or more backscattered signals being received by the receiver, which produces a trace for each of the one of more backscattered signals. Changing an environmental condition in the wellbore, generating additional backscattered light signals at one or more frequencies after the change. Comparing the traces generated before the condition change to those generated after the change, identifying a before trace and an after trace that are substantially equal to each other and identifying a frequency difference between these traces. The frequency difference can be used to determine the amount of change in the environmental condition that occurred when the environmental change event happened.

Abstract: In some embodiments, a method and apparatus, as well as an article, may operate to determine downhole properties based on detected optical signals. An optical detection apparatus can include an optical detector including a superconducting nanowire single photon detector (SNSPD) for detecting light received at an input section of fiber optic cable. The optical detection apparatus can further include a cryogenic cooler configured to maintain the temperature of a light-sensitive region of the SNSPD within a superconducting temperature range of the SNSPD. Downhole properties are measured based on detected optical signals received at the optical detection apparatus. Additional apparatus, systems, and methods are disclosed.

Abstract: In some embodiments, a method and apparatus, as well as an article, may operate to determine properties based on detected optical signals. An optical detection apparatus can include an optical detector for detecting light received through a fiber optic cable; a housing for enclosing the optical detector; a light source; and a cooling mechanism having the housing mounted thereto. The cooling mechanism can maintain the temperature of a light-sensitive region of the optical detector within a temperature range below 210 degrees Kelvin. Additional apparatus, systems, and methods are disclosed.

Abstract: In some embodiments, a method and apparatus, as well as an article, may operate to determine downhole properties based on detected optical signals. An optical detection system can include a fiber optic cable having a sensing location to generate a backscattered Rayleigh signal representative of measurement parameters. The optical detection system can further include a light source to transmit a measurement signal to cause the sensing location to provide the backscattered Rayleigh signal. The optical detection system can further include an optical detector comprising a single-photon detector (SPD) for detecting the backscattered Rayleigh signal received over the fiber optic cable. The optical detection system can further include circuitry to produce an acoustic signal representative of a downhole property based on the phase of the backscattered Rayleigh signal. Additional apparatuses, systems, and methods are disclosed.

Abstract: An example system for detecting mud pump stroke information comprises a distributed acoustic sensing (DAS) data collection system coupled to a downhole drilling system, a stroke detector coupled to a mud pump of the downhole drilling system configured to detect strokes in the mud pump and to generate mud pump stroke information based on the detected strokes, and a fiber disturber coupled to the stroke detector and to optical fiber of the DAS data collection system configured to disturb the optical fiber based on mud pump stroke information generated by the stroke detector. The system further comprises a computing system comprising a processor, memory, and a pulse detection module operable to transmit optical signals into the optical fiber of the DAS data collection system, receive DAS data signals in response to the transmitted optical signals, and detect mud pump stroke information in the received DAS data signals.

Abstract: Methods and systems for the use of partially reflective materials and coatings for optical communications in a wellbore environment are provided. In one embodiment, methods for remote communication in a wellbore comprise: positioning an optical fiber in the wellbore, wherein at least a portion of the optical fiber comprises a partially reflective coating; transmitting an output optical signal from an optical source through the optical fiber; and receiving a reflected optical signal from the optical fiber at an optical detector, wherein at least one optical property of the reflected optical signal is indicative of a downhole condition.

Abstract: A cementing tool with a top seal and a bottom seal may be positionable within a casing string of a wellbore. A fiber optic line may be coupled to the top seal and to a second fiber optic line coupled to a bottom seal that is deployed within an annulus. An amplifier coupled to the cementing tool may amplify a source optical signal from a light source and a sensing measurement signal from the second fiber optic line and the first fiber optic line. One or more operational parameters, such as cementing parameters, may be adjusted based, at least in part, on the sensing measurement signal.

Abstract: A pipe has a longitudinal axis. A flex board extends along the longitudinal axis within the pipe and curls around the longitudinal axis. A cross-section of the flex board perpendicular to the longitudinal axis has a flex-board curve shape that has a first section on a first side of a line perpendicular to the longitudinal axis and a second section on a second side of the line perpendicular to the longitudinal axis. The first section has a first section shape and the second section has a second section shape. A first conductive stripe is coupled to the flex board, extends along the longitudinal axis, and follows the contour of the first section of the flex board. A second conductive stripe is coupled to the flex board, extends along the longitudinal axis, and follows the contour of the second section of the flex board.

Abstract: In distributed fiber-optic sensing within a borehole, the accuracy of correlating signal channels with depth along the borehole can be improved by taking the thermo-optic effect on the group velocity of light into account. In an example application, this allows, in turn, to more accurately localize acoustic sources via distributed acoustic sensing. Additional embodiments are disclosed.

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.