Abstract: An apparatus for sensing acoustic energy in a borehole penetrating the earth includes an optical interrogator and a sensing optical fiber having a length Ls optically coupled to the optical interrogator and configured to sense the acoustic energy to provide sensed acoustic data. The apparatus also includes a reference optical fiber having a length Lr optically coupled to the optical interrogator to provide reference data, wherein the optical interrogator corrects the sensed acoustic data using the reference data to provide corrected sensed acoustic data.

Abstract: A method and apparatus for measuring a pressure. A pressure gauge includes a first plate having a resonant frequency related to a pressure at the pressure gauge. The first plate is thermally-excited at a selected frequency, and a sensor measures a first power level of a first light having a first wavelength reflected from the first plate and a second power level of a second light having a second wavelength reflected from the first plate. A processor determines a thermal drift in the resonant frequency of the first plate due to the thermal excitation of the first plate from the first power level and the second power level, corrects a pressure measurement determined from the resonant frequency of the first plate for the thermal drift of the resonant frequency, and operates a device based on the pressure measurement.

Abstract: An apparatus for sensing acoustic energy in a borehole penetrating the earth includes an optical interrogator and a sensing optical fiber having a length Ls optically coupled to the optical interrogator and configured to sense the acoustic energy to provide sensed acoustic data. The apparatus also includes a reference optical fiber having a length Lr optically coupled to the optical interrogator to provide reference data, wherein the optical interrogator corrects the sensed acoustic data using the reference data to provide corrected sensed acoustic data.

Abstract: Downhole fiber optic interrogation systems are described. The systems include a fiber optic control system, a first sensing system, a second sensing system, an optical fiber disposed within a well, and an optical switch arranged between the optical fiber and the first and second sensing systems, wherein the fiber optic control system performs time division multiplex control of the optical switch wherein the first sensing system is operably connected to the optical fiber and the second sensing system is not connected to the optical fiber, and further controls the optical switch such that the second sensing system is operably connected to the optical fiber and the first sensing system is not connected to the optical fiber.

Abstract: A system and method to determine temperature include an optical fiber and at least two pulse laser sources to transmit light pulses with at least two wavelengths into the optical fiber. The system also includes an optical path length modulator to modulate the optical path length of the optical fiber as the light pulses are transmitted into the optical fiber. At least two photodetectors detect backscatter reflected in the optical fiber, and a processor determines the temperature based on the backscatter.

Abstract: An embodiment of a system for performing measurements in a downhole environment includes an optical interrogation assembly configured to emit a pulsed optical signal, the pulsed optical signal including a selected wavelength, and an optical fiber configured to be disposed in a borehole in an earth formation and configured to receive the pulsed optical signal, the optical fiber having at least one measurement location disposed therein and configured to at least partially reflect the pulsed optical signal. The optical fiber has a core and a cladding, at least a portion of the core made from at least substantially pure silica, and the optical fiber has a refractive index profile configured to have a zero dispersion wavelength that is greater than the selected wavelength.

Abstract: Downhole fiber optic interrogation systems are described. The systems include a fiber optic control system, a first sensing system, a second sensing system, an optical fiber disposed within a well, and an optical switch arranged between the optical fiber and the first and second sensing systems, wherein the fiber optic control system performs time division multiplex control of the optical switch wherein the first sensing system is operably connected to the optical fiber and the second sensing system is not connected to the optical fiber, and further controls the optical switch such that the second sensing system is operably connected to the optical fiber and the first sensing system is not connected to the optical fiber.

Abstract: An embodiment of a system for measuring a parameter includes at least a first optical fiber and a second optical fiber configured to be disposed in one or more boreholes in an earth formation, the first optical fiber and the second optical fiber including a plurality of sensing locations. The system also includes a first light source configured to launch a first optical signal into at least the first optical fiber, and a second light source configured to launch a second optical signal into at least the second optical fiber, wherein the first optical signal and the second optical signal are launched at least substantially simultaneously. The system further includes a processor configured to receive measurement data generated based on backscattered signals from at least the first optical fiber and the second optical fiber the reflected signals, the processor configured estimate the parameter based on the measurement data.

Abstract: A method and apparatus for measuring a pressure. A pressure gauge includes a first plate having a resonant frequency related to a pressure at the pressure gauge. The first plate is thermally-excited at a selected frequency, and a sensor measures a first power level of a first light having a first wavelength reflected from the first plate and a second power level of a second light having a second wavelength reflected from the first plate. A processor determines a thermal drift in the resonant frequency of the first plate due to the thermal excitation of the first plate from the first power level and the second power level, corrects a pressure measurement determined from the resonant frequency of the first plate for the thermal drift of the resonant frequency, and operates a device based on the pressure measurement.

Abstract: A method of measuring temperatures, includes disposing a carrier in a borehole in an earth formation, the carrier having an optical fiber connected thereto, interrogating the optical fiber with a pulsed optical signal generated by a distributed temperature sensing (DTS) assembly, the pulsed optical signal having a first frequency, and receiving first reflected signals from the optical fiber, estimating an absolute temperature from the reflected signals, interrogating the optical fiber with an at least partially coherent optical signal from a phase sensitive optical time domain reflectometry (?-OTDR) assembly, the at least partially coherent optical signal having a second frequency, and receiving second reflected signals from multiple scattering locations in the optical fiber; estimating a phase difference between the reflected signals, and estimating a temperature change based on the phase difference, and combining the absolute temperature and the temperature change to generate a temperature profile at a loca

Abstract: A system and method to determine temperature include an optical fiber and at least two pulse laser sources to transmit light pulses with at least two wavelengths into the optical fiber. The system also includes an optical path length modulator to modulate the optical path length of the optical fiber as the light pulses are transmitted into the optical fiber. At least two photodetectors detect backscatter reflected in the optical fiber, and a processor determines the temperature based on the backscatter.

Abstract: An embodiment of a system for performing measurements in a downhole environment includes an optical interrogation assembly configured to emit a pulsed optical signal, the pulsed optical signal including a selected wavelength, and an optical fiber configured to be disposed in a borehole in an earth formation and configured to receive the pulsed optical signal, the optical fiber having at least one measurement location disposed therein and configured to at least partially reflect the pulsed optical signal. The optical fiber has a core and a cladding, at least a portion of the core made from at least substantially pure silica, and the optical fiber has a refractive index profile configured to have a zero dispersion wavelength that is greater than the selected wavelength.

Abstract: A method of measuring temperatures, includes disposing a carrier in a borehole in an earth formation, the carrier having an optical fiber connected thereto, interrogating the optical fiber with a pulsed optical signal generated by a distributed temperature sensing (DTS) assembly, the pulsed optical signal having a first frequency, and receiving first reflected signals from the optical fiber, estimating an absolute temperature from the reflected signals, interrogating the optical fiber with an at least partially coherent optical signal from a phase sensitive optical time domain reflectometry (?-OTDR) assembly, the at least partially coherent optical signal having a second frequency, and receiving second reflected signals from multiple scattering locations in the optical fiber; estimating a phase difference between the reflected signals, and estimating a temperature change based on the phase difference, and combining the absolute temperature and the temperature change to generate a temperature profile at a loca

Abstract: An embodiment of a system for measuring a parameter includes at least a first optical fiber and a second optical fiber configured to be disposed in one or more boreholes in an earth formation, the first optical fiber and the second optical fiber including a plurality of sensing locations. The system also includes a first light source configured to launch a first optical signal into at least the first optical fiber, and a second light source configured to launch a second optical signal into at least the second optical fiber, wherein the first optical signal and the second optical signal are launched at least substantially simultaneously. The system further includes a processor configured to receive measurement data generated based on backscattered signals from at least the first optical fiber and the second optical fiber the reflected signals, the processor configured estimate the parameter based on the measurement data.

Abstract: A distributed temperature sensor (DTS) system includes a light source; a length of fiber filter having been hydrogen darkened prior to assembly of the system; and a DTS fiber. A method for making a filter for a DTS system.

Abstract: A distributed temperature sensor (DTS) system includes a light source; a length of fiber filter having been hydrogen darkened prior to assembly of the system; and a DTS fiber. A method for making a filter for a DTS system.