A serial weak FBG interrogator is disclosed. The serial weak FBG interrogator may include a CW tunable laser or pulsed laser utilized as a laser source and an EDFA. The serial weak FBG interrogator may also be an interrogation of a single sensor system by utilization of a DFB laser which utilizes a single sensor, which may be an interferometer sensor, an extrinsic Fabry-Perot interferometer or a wavelength-modulated sensor. The serial weak FBG interrogator may also include a computer system or CSPU.

A method of manufacturing an optical fiber sensing device includes steps of moving an optical fiber having a core linearly along a first direction, during the moving, directly writing a number of nanograting structures into the core using a laser beam generated by an ultrafast laser system, wherein the number of nanograting structures form a number of scattering points; and forming an energy transducing element on an outer surface of the optical fiber, wherein the number of scattering points is/are structured and configured to scatter light out of fiber core and into the transducing element to provide local power for the optical fiber sensing device. A system for performing the method is also provided.

An apparatus for determining the position of an object having one or more magnetic elements. The apparatus includes magnetostrictive optical sensors, each arranged to produce a signal which is indicative of a proximity of the sensor to the one or more magnetic elements. The apparatus is arranged to determine the position of the object based on a plurality of such proximity signals.

Methods, systems and devices for estimating a parameter of interest in a borehole. The method may include generating information from an optical displacement device relating to relative motion between two or more reflective surfaces thereof that is indicative of the parameter of interest; and preventing changes in the information resulting from changes at the optical displacement device in at least one of i) temperature, or ii) pressure, by compensating for the changes. Compensating may include adjusting at least one light source generating an electromagnetic beam at least partly received by the optical displacement device responsive to information relating to a control optical displacement device at the optical displacement device. Compensating may include using an optical displacement device and configuring the optical displacement device such that a difference between a first variable gap and a second variable gap is substantially zero while the apparatus is subject to nominal conditions.

A transformer system includes a transformer and a transformer tank. The transformer tank houses the transformer in a bath of a dielectric fluid. The transformer system also includes a controller, and a fiber optic sensor communicatively coupled to the controller. The fiber optic sensor is disposed in the dielectric fluid and operative to provide an output that varies with the level of the dielectric fluid. The controller is operative to determine the level of the dielectric fluid based on the output of the fiber optic sensor.

A sensor network having a series arrangement of fiber-coupled, reflective sensors is disclosed. In operation, a first light signal having multiple wavelength bands is launched in an upstream direction on a fiber bus. Each sensor includes a wavelength filter and an FP sensor that is sensitive to a parameter. Each wavelength filter (1) selectively passes a different one of the wavelength bands to its FP sensor and (2) reflects the remaining wavelength bands back into the fiber bus to continue upstream. The FP sensor imprints a signal based on the parameter onto its received light and reflects it as a second light signal. The collimator, wavelength filter, and FP sensor of each sensor are arranged such that each second light signal is returned to the fiber bus, which conveys them in a downstream direction to a processor that measures them and estimates the parameter at each sensor.

A system includes at least one optical fiber having at least one FBG and a detection system. The optical fiber is configured to be coupled to a structure in at least one location. The location at which the optical fiber is to be coupled to the structure is different from a location at which the FBG is disposed. The detection system includes a light source configured to inject light into the optical fiber, a photodetector configured to detect a shift in a wavelength spectrum of light reflected by the FBG as a result of a time-varying strain induced at the at least one FBG, and a processor configured to detect a shear-horizontal guided stress wave propagating in said structure based on the shift in the wavelength spectrum detected by the photodetector induced by a longitudinal-type guided stress wave that is propagated along the optical fiber.

Sensor systems including an interferometer system are disclosed herein. In a general embodiment, the sensor system includes an optical fiber that is embedded into a sample, where the optical fiber has a reflective tip. The optical fiber is optically coupled to a sensor and a detector of the laser interferometer system. The sensor system further includes a computing device or circuit that is configured to receive electrical signals generated by the detector. The laser source is configured to emit light, which is coupled into the optical fiber. The light travels through the optical fiber until the light reaches the reflective tip, where it is reflected back through the optical fiber. The detector is impacted by the reflected light, and generates an electrical signal based upon the reflected light. The computing device generates a value that is indicative of a behavior of the sample based upon the electrical signal.

Apparatuses, systems and methods for modulating returned light for acquisition of 3D data from a scene are described. A 3D imaging system includes a Fabry-Perot cavity having a first partially-reflective surface for receiving incident light and a second partially-reflective surface from which light exits. An electro-optic material is located within the Fabry-Perot cavity between the first and second partially-reflective surfaces. Transparent longitudinal electrodes or transverse electrodes produce an electric field within the electro-optic material. A voltage driver is configured to modulate, as a function of time, the electric field within the electro-optic material so that the incident light passing through the electro-optic material is modulated according to a modulation waveform. A light sensor receives modulated light that exits the second partially-reflective surface of the Fabry-Perot cavity and converts the light into electronic signals. Three-dimensional (3D) information regarding a scene-of-interest may be obtained from the electronic signals.

Distributed acoustic sensing (DAS) system for quasi-coherent detection of at least one multi-frequency signal over an optical fiber, including a multi-frequency pulse generator, a circulator, a coherent detector and a processor, the pulse generator for generating at least one multi-frequency pulse train including at least two pulses each having a different frequency, the pulse train including a plurality of carriers, the coherent detector for receiving at least one backscattered signal from the optical fiber and the processor for quasi-coherent aggregation of the carriers in the backscattered signal, wherein the processor channelizes the backscattered signal into at least one complex signal for each frequency in the carriers and wherein for each complex signal, the processor respectively extracts at least one of an amplitude change and a phase change for each one of the carriers and selectively aggregates at least one of the changes for the carriers for determining if an event has occurred over the optical fiber.