The present invention discloses a computational distributed fiber-optic sensing method and system. The method includes: determining a signal source for modulating intensity of incident light, where the signal source is a binary sequence; using an optical pulse sequence obtained after modulation is performed using the signal source, as an incident light signal, and emitting the incident light signal to an optical fiber; acquiring, according to specified sampling frequency, a scattered light signal obtained through optical fiber scattering; determining, according to the incident light signal and the scattered light signal, a time-domain reconstructed image of a to-be-detected light signal by using a time domain-based differential ghost imaging protocol; and determining a sensing signal of the optical fiber according to the time-domain reconstructed image of the to-be-detected light signal. The computational distributed fiber-optic sensing method and system provided in the present invention feature low sampling frequency, low device complexity, and low costs.

An object of the present disclosure is to provide an optical fiber cable monitoring method and an optical fiber cable monitoring system capable of linking information obtained from a measurement result with information stored in a DB and accurately specifying a loss occurrence location on an optical fiber cable. The optical fiber cable monitoring method according to the present disclosure uses two types of optical fiber measurement techniques having different sensitivities. Each of closure locations on the optical fiber cable is acquired with a high-sensitivity measurement technique, and geographical location information and the closure locations on the optical fiber are linked in an arrangement order of the closures. Thus, an operator can recognize an actual location (geographical location information) of a closure that is linked to a location of a point of abnormality on the optical fiber cable when an abnormality in the closure is detected with a low-sensitivity measurement technique.

An optical fiber sensor device includes a control section configured to compute a physical quantity in an optical fiber installed at plural measurement locations based on intensity of scattered light received, and to compute an average of the computed physical quantity for the optical fiber. The control section is configured to compute the average of the physical quantity based on the computed physical quantity and on a length of the optical fiber. A length of the optical fiber installed at the measurement location is increased as a distance between a light source and the respective measurement location increases.

An optical fiber characteristic measurement device includes: a detector that detects Brillouin scattered light obtained by causing light to be incident on an optical fiber under test; a spectrum analyzer that obtains a Brillouin gain spectrum from the Brillouin scattered light; and a spectrum analyzing controller that: measures a characteristic of the optical fiber under test by analyzing the Brillouin gain spectrum to obtain a peak frequency of the Brillouin gain spectrum, and changes a frequency range used by the spectrum analyzer to obtain the Brillouin gain spectrum according to the peak frequency.

A distributed acoustic system (DAS) method and system. The system may comprise an interrogator and an umbilical line comprising a first fiber optic cable and a second fiber optic cable attached at one end to the interrogator. The DAS may further include a downhole fiber attached to the umbilical line at the end opposite the interrogator and a light source disposed in the interrogator that is configured to emit a plurality of coherent light frequencies into the umbilical line and the downhole fiber. The method may include generating interferometric signals of the plurality of frequencies of backscattered light that have been received by the photo detector assembly and processing the interferometric signals with an information handling system.

A distributed acoustic system (DAS) with an interrogator, an umbilical line attached at one end to the interrogator, and a downhole fiber attached to the umbilical line at the end opposite the interrogator. A method for optimizing a sampling frequency may begin with identifying a length of a fiber optic cable connected to an interrogator, identifying one or more regions on the fiber optic cable in which a backscatter is received, and optimizing a sampling frequency of a distributed acoustic system (DAS) by identifying a minimum time interval that is between an emission of a light pulse such that at no point in time the backscatter arrives back at the interrogator that corresponds to more than one spatial location along a sensing portion of the fiber optic cable.

Embodiments relate to a dual Brillouin distributed optical fiber sensing system and a sensing method using Brillouin scattering that detects an event area in which an event occurred quickly by simultaneously measuring multiple correlation points located in an optical fiber under test by using a pump signal modulated with a pulsed gating signal and a continuous wave probe signal, and then precisely measures the corresponding event area by using the probe signal modulated with the pulsed gating signal and the pump signal.

Aspects of the present disclosure describe systems, methods and structures providing bipolar cyclic coding for Brillouin optical time domain analysis that may be employed—for example—to determine high accuracy temperature and/or strain measurements along an optical fiber. Systems, methods, and structures according to the present disclosure employ the bipolar cyclic coding technique that advantageously overcomes the problems that plague the prior art and provides extended sensing range resulting from superior signal-to-noise characteristics.

Embodiments relate to a dual Brillouin distributed optical fiber sensing system and a sensing method using Brillouin scattering that detects an event area in which an event occurred quickly by simultaneously measuring multiple correlation points located in an optical fiber under test by using a pump signal modulated with a pulsed gating signal and a continuous wave probe signal, and then precisely measures the corresponding event area by using the probe signal modulated with the pulsed gating signal and the pump signal.

An improved technique for acoustic sensing involves, in one embodiment, launching into a medium, a plurality of groups of pulse-modulated electromagnetic-waves. The frequency of electromagnetic waves in a pulse within a group differs from the frequency of the electromagnetic waves in another pulse within the group. The energy scattered by the medium is detected and, in one embodiment, the beat signal may be used to determine a characteristic of the environment of the medium. For example, if the medium is a buried optical fiber into which light pulses have been launched in accordance with the invention, the presence of acoustic waves within the region of the buried fiber can be detected.