Abstract: Various example embodiments for supporting distributed fiber optic sensing are presented. Various example embodiments for supporting distributed fiber optic sensing may be configured to support distributed fiber optic sensing via fiber optic cables. Various example embodiments for supporting distributed fiber optic sensing via a fiber optic cable may be configured to support distributed fiber optic sensing based on interrogation of an optical fiber of the fiber optic cable that is also configured to carry communications. Various example embodiments for supporting distributed fiber optic sensing of a fiber optic cable may be configured to support distributed fiber optic sensing of a fiber optic cable based on interrogation of an optical fiber of the fiber optic cable that is also configured to carry optical data communication channels using an optical interrogation channel where the optical data communication channels and the optical interrogation channel are spectrally separated.

Abstract: A method for measuring a response from an optical fiber providing distributed back reflections using a system comprising an optical source comprising a laser, an optical receiver and a processing unit is disclosed. The method comprises generating an interrogation signal and an optical local oscillator using the optical source, the interrogation signal being represented by an interrogation phasor and the optical local oscillator being represented by a local oscillator phasor; transmitting the interrogation signal into the optical fiber; and mixing the optical local oscillator with reflected light from the optical fiber and detecting a mixing product with the optical receiver to achieve a receiver output signal.

Abstract: A method for measuring a response from an optical fiber providing distributed back reflections using a system comprising an optical source comprising a laser, an optical receiver and a processing unit is disclosed. The method comprises establishing initial parameters of a distributed back-reflection processing. The method also comprises generating an interrogation signal and an optical local oscillator using the optical source, the interrogation signal being represented by an interrogation phasor and the optical local oscillator being represented by a local oscillator phasor; transmitting the interrogation signal into the optical fiber; and mixing the optical local oscillator with reflected light from the optical fiber and detecting a mixing product with the optical receiver to achieve a receiver output signal.

Abstract: A method for measuring a response from an optical fiber providing distributed back reflections using a system comprising an optical source comprising a laser, an optical receiver and a processing unit is disclosed. The method comprises establishing initial parameters of a distributed back-reflection processing. The method also comprises generating an interrogation signal and an optical local oscillator using the optical source, the interrogation signal being represented by an interrogation phasor and the optical local oscillator being represented by a local oscillator phasor; transmitting the interrogation signal into the optical fiber; and mixing the optical local oscillator with reflected light from the optical fiber and detecting a mixing product with the optical receiver to achieve a receiver output signal.

Abstract: A method for measuring a response from an optical fiber providing distributed back reflections using a system comprising an optical source comprising a laser, an optical receiver and a processing unit is disclosed. The method comprises generating an interrogation signal and an optical local oscillator using the optical source, the interrogation signal being represented by an interrogation phasor and the optical local oscillator being represented by a local oscillator phasor; transmitting the interrogation signal into the optical fiber; and mixing the optical local oscillator with reflected light from the optical fiber and detecting a mixing product with the optical receiver to achieve a receiver output signal.

Abstract: The invention relates to a method of interrogating an interferometric optical fiber sensor system including a laser source configured to generate interrogation light and a sensor array with at least a first reflector and a second reflector.

Abstract: The invention relates to a method of interrogating an interferometric optical fibre sensor system including a laser source configured to generate interrogation light and a sensor array with at least a first reflector and a second reflector.

Abstract: A method of processing data from a distributed fibre-optic interferometric sensor system for measuring a measurand, the system comprising multiple interferometric sensors. The method comprises interrogating two or more of the multiple interferometric sensors to record a raw measurement time series for each of the sensors. The method further comprises calculating a common reference time series as a measure of central tendency of the raw measurement time series from two or more reference sensors, the reference sensors being selected from the multiple interferometric sensors. Finally, the method comprises compensating at least one raw measurement time series from a measurement sensor selected from the multiple interferometric sensors with the common reference time series to produce a compensated measurement time series, the measurement sensor being configured to be sensitive to the measurand. The invention further relates to a distributed fibre-optic interferometric sensor system.

Abstract: A method of processing data from a distributed fibre-optic interferometric sensor system for measuring a measurand, the system comprising multiple interferometric sensors. The method comprises interrogating two or more of the multiple interferometric sensors to record a raw measurement time series for each of the sensors. The method further comprises calculating a common reference time series as a measure of central tendency of the raw measurement time series from two or more reference sensors, the reference sensors being selected from the multiple interferometric sensors. Finally, the method comprises compensating at least one raw measurement time series from a measurement sensor selected from the multiple interferometric sensors with the common reference time series to produce a compensated measurement time series, the measurement sensor being configured to be sensitive to the measurand. The invention further relates to a distributed fibre-optic interferometric sensor system.

Abstract: Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.

Abstract: Methods and apparatus for interrogating optical sensors with high slew rates using non-uniform sampling are provided. The transmission of optical signals in a non-uniform pattern is employed to allow for demodulation of fringe rates exceeding the commonly understood Nyquist frequency limit given as one half of the mean sampling frequency. By monitoring the time dependent fringe frequency and assuming that the fringe frequency has a limited bandwidth, only a limited bandwidth smaller than the Nyquist bandwidth around the instantaneous fringe frequency needs to be reconstructed at any time.

Abstract: A method and apparatus for demodulation of detected fringes from interferometric sensors with high slew rates are provided. A detected interference signal may be mixed with a local oscillator phasor to obtain a mixed signal, the local oscillator being controlled to produce a frequency that roughly matches the fringe frequency of the interference signal. A sensor phase estimate may be obtained from the detected interference signal or the mixed signal. The local oscillator signal can be computed from the sensor phase estimate. The mixed signal and the sensor phase estimate may be low pass filtered and decimated and the resulting decimated mixed signal and decimated sensor phase estimate may be processed and combined with moderate processing power requirements in an effort to accurately measure the sensor phase for the interferometric sensor.

Abstract: Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.

Abstract: Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.

Abstract: Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.

Abstract: A seismic sensor station includes a housing containing a fiber optic hydrophone and a fiber optic accelerometer that can both be made from a single length of optical fiber arranged inside the housing. The fiber optic accelerometer is arranged in a liquid/oil filled compartment of the housing for dampening of mechanical resonances in the accelerometer due to mechanical disturbances and pressure fluctuations.

Abstract: Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.

Abstract: Methods and apparatus for interrogating optical sensors with high slew rates using non-uniform sampling are provided. The transmission of optical signals in a non-uniform pattern is employed to allow for demodulation of fringe rates exceeding the commonly understood Nyquist frequency limit given as one half of the mean sampling frequency. By monitoring the time dependent fringe frequency and assuming that the fringe frequency has a limited bandwidth, only a limited bandwidth smaller than the Nyquist bandwidth around the instantaneous fringe frequency needs to be reconstructed at any time.

Abstract: A method and apparatus for demodulation of detected fringes from interferometric sensors with high slew rates are provided. A detected interference signal may be mixed with a local oscillator phasor to obtain a mixed signal, the local oscillator being controlled to produce a frequency that roughly matches the fringe frequency of the interference signal. A sensor phase estimate may be obtained from the detected interference signal or the mixed signal. The local oscillator signal can be computed from the sensor phase estimate. The mixed signal and the sensor phase estimate may be low pass filtered and decimated and the resulting decimated mixed signal and decimated sensor phase estimate may be processed and combined with moderate processing power requirements in an effort to accurately measure the sensor phase for the interferometric sensor.

Abstract: A method for interrogating time-multiplexed interferometric sensors using multiple interrogation pulses so as to increases the allowable interrogation pulse duty-cycle and improve the signal-to-noise ratio. In each TDM repetition period a sequence of multiple interrogation pulses are generated. The pulses in the sequence are separated by a time that is equal to the sensor imbalance. The phase from pulse to pulse in each TDM time-slot is modulated at a different, linear rate such that the pulse in time-slot m will have an optical frequency that is shifted by m??, where ?? is the sub-carrier frequency. Because multiple reflections do not need to fade out the inventive method can enhance the signal-to-noise ratio of interferometric sensors such as inline Fabry-Perot sensors.