A distributed optical fiber sensing (DOFS)/distributed acoustic sensing (DAS) method employing polarization diversity combining and spatial diversity combining for a DOFS/DAS system wherein the polarization diversity combining determines a temporal average product for each beating product, determines one having a max average power, rotates that one having max average power for its phase shift to produce a reference, determines a phase difference for each beating product as compared to the reference, compensates any phase difference such that all beating products exhibit a well-aligned phase; and combining the beating products; and wherein the spatial diversity combining uses the combined beating products for each location, determines a temporal average power, determines a location having a greatest average power; and combines the results and provides an indicia of the combined result(s).

Provided is a device for measuring the amount of probe displacement using a change in amount of light, the device including: a sensor mounting unit having a sensor and configured to adjust a position so that a probe is provided at a position corresponding to the sensor; a handpiece fixing unit configured to fix a handpiece by means of a through-hole formed at a center of the handpiece fixing unit; and an impedance matching unit configured to generate acoustic impedance to the probe.

Aspects of the present disclosure describe distributed optical fiber sensing systems, methods, and structures that advantageously employ point sensors that send sensory data/information over an attached, distributed optical fiber sensor without using a separate network or communications facility.

Aspects of the present disclosure describe distributed fiber optic sensing (DFOS)-distributed acoustic sensing (DAS) based systems, methods, and structures that advantageously enable and/or facilitate the monitoring of civil infrastructures via acoustic wave speed measurements.

Systems, methods, and structures that provide distributed acoustic sensing using chirped optical pulses of selectable duration and bandwidth, at a frame rate limited by a round-trip propagation time of a fiber under test. Instead of processing a transmitted chirped pulse as a single sequence—our systems, methods, and structures employ a parallel fragmented multiband architecture, where each tributary correlates the received signal with a truncated chirped pulse to obtain the Rayleigh impulse response over its frequency band. By reducing the duration of the chirp processed by each tributary, spatial leakage is reduced at all the tributaries, thus even after combining all the interferometric products from all tributaries using a rotated vector sum, the resultant signal is much less impacted by spatial leakage than by using a conventional TGD-OFDR method.

An apparatus for monitoring mechanical integrity of an eye-safety component of an illuminator is disclosed. The apparatus comprises a sensor, operable to sense a photoacoustic effect in the eye-safety component during operation of the illuminator and to output a signal representative of the sensed photoacoustic effect, and a processor. The processor is operable to: monitor the signal from the sensor; determine if the signal comprises at least one parameter that falls outside of a pre-determined acceptable range, the pre-determined acceptable range being indicative of mechanical integrity of the eye-safety component; and initiate a safety action in response to a determination that the at least one parameter falls outside of the pre-determined acceptable range thereby indicating a loss of mechanical integrity.

An apparatus for monitoring mechanical integrity of an eye-safety component of an illuminator is disclosed. The apparatus comprises a sensor, operable to sense a photoacoustic effect in the eye-safety component during operation of the illuminator and to output a signal representative of the sensed photoacoustic effect, and a processor. The processor is operable to: monitor the signal from the sensor; determine if the signal comprises at least one parameter that falls outside of a pre-determined acceptable range, the pre-determined acceptable range being indicative of mechanical integrity of the eye-safety component; and initiate a safety action in response to a determination that the at least one parameter falls outside of the pre-determined acceptable range thereby indicating a loss of mechanical integrity.

A system for measuring periodic displacement of an object in periodic motion at a first frequency includes a light source module, a camera module and a processor. The light source module is configured to periodically illuminate the object at a second frequency that is different from the first frequency and that is related to a sum of the first frequency and a first constant. The camera module is configured to take pictures of the object. The processor is in communication with the camera module in order to receive the pictures, and is configured to determine periodic displacement of the object based on the pictures.

A system for measuring periodic displacement of an object in periodic motion at a first frequency includes a light source module, a camera module and a processor. The light source module is configured to periodically illuminate the object at a second frequency that is different from the first frequency and that is related to a sum of the first frequency and a first constant. The camera module is configured to take pictures of the object. The processor is in communication with the camera module in order to receive the pictures, and is configured to determine periodic displacement of the object based on the pictures.

A method of detecting sand inflow into a wellbore is disclosed. The method can include obtaining a sample data set, detecting a broadband signal within the sample data set, comparing the broadband signal with a signal reference, determining that the broadband signal meets or exceeds the signal reference, and determining the presence of sand inflow into the wellbore based on determining that the broadband signal meets or exceeds the signal reference. The sample data set can be a sample of an acoustic signal originating within a wellbore including a fluid, and the broadband signal at least includes a portion of the sample data set at frequencies above 0.5 kHz.