A method and a system for interrogating an optical fiber includes a probe signal that has a first frequency comb at a first repetition rate (Δf) injected into the optical fiber. A backscattering signal that includes the probe signal convolved with an impulse response of the optical fiber in reflection which is sensitive to at least one parameter being measured from the optical fiber is gathered. The backscattering signal is beaten with a local oscillator signal to generate a beating signal, the local oscillator signal including a second frequency comb at a second repetition rate that is offset from the first repetition rate (Δf+δf) and being mutually coherent with the first frequency comb. The resulting beating signal is analysed to thereby determine the at least one parameter being measured from the optical fiber.

The present invention relates to a stratum deformation monitoring device. The device includes a working tube having an outer surface and an in-tube space and buried into a target stratum; a plurality of deformation monitoring rings, each of which the plurality of deformation monitoring rings are movably assembled on the outer surface of the working tube in equal intervals or unequal intervals; and at least one strain optical fiber movably assembled on the outer surface of the working tube by securing on the plurality of deformation monitoring rings.

The present invention relates to a stratum deformation monitoring device. The device includes a working tube having an outer surface and an in-tube space and buried into a target stratum; a plurality of deformation monitoring rings, each of which the plurality of deformation monitoring rings are movably assembled on the outer surface of the working tube in equal intervals or unequal intervals; and at least one strain optical fiber movably assembled on the outer surface of the working tube by securing on the plurality of deformation monitoring rings.

A system for downhole measurements. The system may comprise a fiber optic cable that further comprises a transmission fiber and a return fiber. Additionally, the system may comprise a passive optical device optically connected to the transmission fiber and the return fiber, a first wavelength division multiplexer (WDM) optically connected to the transmission fiber, and a second WDM optically connected to the return fiber. The system may further comprise a transmitter and a first Raman pump optically connected to the first WDM and a receiver and a second Raman pump optically connected to the second WDM.

A system for downhole measurements. The system may comprise a fiber optic cable that further comprises a transmission fiber and a return fiber. Additionally, the system may comprise a passive optical device optically connected to the transmission fiber and the return fiber, a first wavelength division multiplexer (WDM) optically connected to the transmission fiber, and a second WDM optically connected to the return fiber. The system may further comprise a transmitter and a first Raman pump optically connected to the first WDM and a receiver and a second Raman pump optically connected to the second WDM.

To expand a measurement range with regard to SDH-BOTDR.

A BFS1 and a BFS2, which is obtained by inverting the BFS1, are acquired on the basis of a first measurement signal and a first local oscillation signal that is a cosine wave, a BFS3 is acquired on the basis of a second measurement signal and a second local oscillation signal that is a sine wave, and a Brillouin frequency shift waveform is synthesized from the BFS1 to BFS3. In the case where an optical fiber is not strained or in the case where temperature of the optical fiber is not changed, a phase rotation number N, which is a phase difference between a measurement signal and a local oscillation signal, is calculated on the basis of intensity of the measurement signal, and an offset corresponding to the phase rotation number N is given to the synthesized Brillouin frequency shift waveform.

To expand a measurement range with regard to SDH-BOTDR.

A BFS1 and a BFS2, which is obtained by inverting the BFS1, are acquired on the basis of a first measurement signal and a first local oscillation signal that is a cosine wave, a BFS3 is acquired on the basis of a second measurement signal and a second local oscillation signal that is a sine wave, and a Brillouin frequency shift waveform is synthesized from the BFS1 to BFS3. In the case where an optical fiber is not strained or in the case where temperature of the optical fiber is not changed, a phase rotation number N, which is a phase difference between a measurement signal and a local oscillation signal, is calculated on the basis of intensity of the measurement signal, and an offset corresponding to the phase rotation number N is given to the synthesized Brillouin frequency shift waveform.

An optical fiber characteristic measurement device (1, 2, 3) includes a photodetector (15, 15A) which detects Brillouin scattered light (LS) obtained by causing light to be incident on an optical fiber (FUT), an intensity acquisitor (16, 16A) which acquires a signal intensity at a prescribed reference frequency (f1, f2) from a detection signal (S1, S2, S3) output from the photodetector, and a measurer (18, 18A, 18B) which measures characteristics of the optical fiber by obtaining a peak frequency of a Brillouin gain spectrum, which is a spectrum of the Brillouin scattered light, from the signal intensity at the reference frequency acquired by the intensity acquisitor.

A well system includes a fiber-optic cable that can be positioned downhole along a wellbore. The well system further includes a plurality of opto-electrical interfaces to communicatively couple to the fiber-optic cable to monitor temperature and strain along the fiber-optic cable. Additionally, the well system includes a processing device and a memory device that includes instructions executable by the processing device to cause the processing device to perform operations. The operations include receiving data representing frequency or phase shift measurements from the opto-electrical interfaces using at least two frequency or phase shift measurement techniques. Further, the operations include generating a temperature shift output and a strain change output using an inversion comprising sensitivity ratios and the data representing the frequency or phase shift measurements from the plurality of opto-electrical interfaces.

A well system includes a fiber-optic cable that can be positioned downhole along a wellbore. The well system further includes a plurality of opto-electrical interfaces to communicatively couple to the fiber-optic cable to monitor temperature and strain along the fiber-optic cable. Additionally, the well system includes a processing device and a memory device that includes instructions executable by the processing device to cause the processing device to perform operations. The operations include receiving data representing frequency or phase shift measurements from the opto-electrical interfaces using at least two frequency or phase shift measurement techniques. Further, the operations include generating a temperature shift output and a strain change output using an inversion comprising sensitivity ratios and the data representing the frequency or phase shift measurements from the plurality of opto-electrical interfaces.