Disclosed herein is a method comprising injecting light of a first wavelength λ.sub.1 into a wavelength division multiplexer; injecting light of a second wavelength λ.sub.2 into the wavelength division multiplexer; combining the light of the first wavelength λ.sub.1 and the light of the second wavelength λ.sub.2 in the wavelength division multiplexer to produce light of a third wavelength λ.sub.3; and reflecting the light of the third wavelength λ.sub.3 in a dual-Brillouin peak optical fiber that is in communication with the wavelength divisional multiplexer; wherein the dual-Brillouin peak optical fiber has at least two Brillouin peaks, such that an amplitude A.sub.1 of at least one of said Brillouin peaks is within 50% to 150% of an amplitude A.sub.2 of another Brillouin peak 0.5A2≤A.sub.1≤1.5A.sub.2; wherein the dual-Brillouin peak optical fiber generates a Brillouin dynamic grating that reflects an improved back-reflected Brillouin signal of the combined light.

A dynamic Brillouin fiber sensor that is immune to fluctuations in the power, frequency, or polarizing state of the pump and probe beams is described herein. A new measurand that combines information from the complex Stokes and anti-Stokes interactions is provided to extract the absolute Brillouin frequency shift while rejecting the majority of noise sources that may limit the performance of current slope-assisted Brillouin optical time domain analysis systems.

A dynamic Brillouin fiber sensor that is immune to fluctuations in the power, frequency, or polarizing state of the pump and probe beams is described herein. A new measurand that combines information from the complex Stokes and anti-Stokes interactions is provided to extract the absolute Brillouin frequency shift while rejecting the majority of noise sources that may limit the performance of current slope-assisted Brillouin optical time domain analysis systems.

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.

Aspects of the present disclosure describe systems, methods, and structures for distributed temperature sensing that employ joint wavelet denoising to achieve desirable signal-to-noise ratio(s) over extended sensor fiber distances.

Aspects of the present disclosure describe systems, methods, and structures for distributed temperature sensing that employ joint wavelet denoising to achieve desirable signal-to-noise ratio(s) over extended sensor fiber distances.

An optical fiber characteristic measurement device (1) includes a light detector (16) configured to detect Brillouin scattered light (LS) obtained by causing light to be incident on an optical fiber (FUT); a signal processor (18b) configured to obtain, on the basis of a detection signal (S1) which is output from the light detector, a first Brillouin gain spectrum (B1) which is a spectrum of the Brillouin scattered light obtained in a case where a spectral width of the light incident on the optical fiber is a first width and a second Brillouin gain spectrum (B2) which is a spectrum of the Brillouin scattered light obtained in a case where the spectral width of the light incident on the optical fiber is a second width larger than the first width; and a measurer (18c) configured to measure characteristics of the optical fiber on the basis of the first Brillouin gain spectrum and the second Brillouin gain spectrum.

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.

Systems and methods are provided for enabling improved sensitivity in low-gain regimes. Embodiments of the present disclosure use polarization pulling to separate a signal of interest (e.g., amplified probe light) from the background probe light. This enables a dramatic increase in probe power and thereby increases the signal-to-noise ratio of the measurement. Embodiments of the present disclosure provide a vector subtraction technique to compensate for undesirable interference effects resulting from the finite extinction of standard polarization components (i.e. polarizing beam splitters) and polarization fluctuations. Embodiments of the present disclosure enable Brillouin sensing with improved accuracy in low-gain regimes and is particularly relevant for high-spatial resolution sensing applications.