An improved optical fiber distributed acoustic sensor system uses an optical fiber having reflector portions distributed along its length in at least a first portion. The reflector portions are positioned along the fiber separated by a distance that is equivalent to twice the distance an optical pulse travels along the fiber in a single sampling period of the data acquisition opto-electronics within the sensor system. No oversampling of the reflections of the optical pulses from the reflector portions is undertaken. The sampling points for data acquisition in the sensor system are aligned with the reflections that arrive at the sensor system from along the sensing fiber. Adaptive delay componentry adaptively aligns the reflected optical signals (or their electrical analogues) with the sampling points. Control over the sampling points can re-synchronise the sampling points with the returning reflections. Reflection equalisation componentry may reduce the dynamic range of the returning reflections.

There is described a method for interrogating optical fiber comprising fiber Bragg gratings (“FBGs”), using an optical fiber interrogator. The method comprises (a) generating an initial light pulse from phase coherent light emitted from a light source, wherein the initial light pulse is generated by modulating the intensity of the light; (b) splitting the initial light pulse into a pair of light pulses; (c) causing one of the light pulses to be delayed relative to the other of the light pulses; (d) transmitting the light pulses along the optical fiber; (e) receiving reflections of the light pulses off the FBGs; and (f) determining whether an optical path length between the FBGs has changed from an interference pattern resulting from the reflections of the light pulses.

A system and method for evaluating individual Fiber Bragg Grating (FBG) sensors in a multiplexed acoustic sensor system, the system comprising: a broadband pulsed source; a circulator that passes a laser pulse to a multiplexed series of N FBG sensors and one reference Fresnel reflector, wherein said circulator also receives a return N+1 reflection pulse train from the N FBG sensors and one reference Fresnel reflector; and an optical switch that receives the return N+1 reflection pulse train from the N FBG sensors and one reference Fresnel reflector.

A method for determining a length of a span of electrically conductive material, comprising a first voltage measurement across the entire span, and a second voltage measurement across a constant-length segment of the span. The dual measurements allow the calculation of the span length in a manner that is robust to many disturbances including ambient temperature, material temperature, and material stress and fatigue.

A system may include a first sensor of a first type and a second sensor of a second different type and having a detector. A field of view of the second sensor may be formed by a plurality of regions of interest (ROIs) defined by the detector. Control circuitry of the system may be configured to perform operations including obtaining, from the first sensor, first sensor data representing an environment, and determining, based on the first sensor data, information associated with a feature of interest within the environment. The operations may also include determining, based on the information, a particular ROI that corresponds to an expected position of the feature at a later time, obtaining a plurality of ROI sensor data from the particular ROI instead of obtaining full-resolution sensor data, and analyzing the plurality of ROI sensor data to determine one or more attributes of the feature.

There is described a method for interrogating optical fiber comprising fiber Bragg gratings (“FBGs”), using an optical fiber interrogator. The method comprises (a) generating an initial light pulse from phase coherent light emitted from a light source, wherein the initial light pulse is generated by modulating the intensity of the light; (b) splitting the initial light pulse into a pair of light pulses; (c) causing one of the light pulses to be delayed relative to the other of the light pulses; (d) transmitting the light pulses along the optical fiber; (e) receiving reflections of the light pulses off the FBGs; and (f) determining whether an optical path length between the FBGs has changed from an interference pattern resulting from the reflections of the light pulses.

A system may include a first sensor of a first type and a second sensor of a second different type and having a detector. A field of view of the second sensor may be formed by a plurality of regions of interest (ROIs) defined by the detector. Control circuitry of the system may be configured to perform operations including obtaining, from the first sensor, first sensor data representing an environment, and determining, based on the first sensor data, information associated with a feature of interest within the environment. The operations may also include determining, based on the information, a particular ROI that corresponds to an expected position of the feature at a later time, obtaining a plurality of ROI sensor data from the particular ROI instead of obtaining full-resolution sensor data, and analyzing the plurality of ROI sensor data to determine one or more attributes of the feature.

Disclosed herein is a system, apparatus and method directed to detecting damage to an optical fiber of a medical device. The optical fiber includes core fibers including a plurality of sensors configured to (i) reflect a light signal based on received incident light, and (ii) change a characteristic of the reflected light signal based on experienced strain. The system also includes a console having memory storing logic that, when executed, causes operations of providing receiving reflected light signals of different spectral widths of the broadband incident light by one or more of the plurality of sensors, processing the reflected light signals to detect fluctuations of a portion of the optical fiber, and determining a location of the portion of the optical fiber or a defect affecting a vessel in which the portion is disposed based on the detected fluctuations. The portion may be a distal tip of the optical fiber.

An optical monitoring system comprising first and second sensor arrays interrogated via first and second optical connections from an interrogator location. The system is configured such that no wavelength is carried bi-directionally in the first and second optical connections. In typical systems the optical connections comprise trunk cables from the sensor arrays to the interrogator location.

According to an embodiment there is provided a distributed optical sensing apparatus for determining of a primary quantity along a waveguide, the distributed optical sensing apparatus comprising: an electromagnetic radiation source adapted for coupling electromagnetic radiation into the waveguide to thereby generate in the waveguide (e.g. by interaction with the waveguide) a first response radiation and a different second response radiation; a detector device adapted for providing a first measurement signal indicative of the first response radiation and a second measurement signal indicative of the second response radiation; an evaluation unit adapted for deriving a secondary quantity (e.g. a loss) based on the first measurement signal and the second measurement signal; the evaluation unit being further adapted for deriving the primary quantity based on the secondary quantity and at least one of the first measurement signal and the second measurement signal.