A method for measuring a response from an optical fiber providing distributed back reflections using a system comprising an optical source comprising a laser, an optical receiver and a processing unit is disclosed. The method comprises establishing initial parameters of a distributed back-reflection processing. The method also comprises generating an interrogation signal and an optical local oscillator using the optical source, the interrogation signal being represented by an interrogation phasor and the optical local oscillator being represented by a local oscillator phasor; transmitting the interrogation signal into the optical fiber; and mixing the optical local oscillator with reflected light from the optical fiber and detecting a mixing product with the optical receiver to achieve a receiver output signal. The method further comprises performing a measurement that characterizes the interrogation phasor; updating the parameters of the distributed back-reflection processing based on the measurement result such that an effect of fluctuations in the interrogation phasor on the measured response from the fiber is reduced; and applying distributed back-reflection processing to the receiver output signal. Finally, the method comprises extracting the response from the optical fiber from the distributed back-reflection processing output. A system for measuring a response from an optical fiber providing distributed back reflections is also disclosed.

A reflection mode sensor system may include an optical fiber core and an optical fiber cladding. A first long period grating (LPG) may be positioned along the optical fiber core having a first grating period, a second LPG may be positioned along the optical fiber core having a second grating period, and a third LPG may be positioned along the optical fiber core having a third grating period. The grating periods may enable sensing of multiple parameters simultaneously. A metal coating may be applied to an end facet of the combined optical fiber core and optical fiber cladding. The metal coating may also cover a side surface of the optical fiber cladding along a length from the end facet. The metal coating may include a paste applied to the optical fiber core and the optical fiber cladding, where the paste has been cured, and includes a metal.

Use of a sensor read out system with at least one fiber optical sensor, which is connected via at least one signal line to a processing unit as part of an additive manufacturing setup, for in situ and real time quality control of a running additive manufacturing process. Acoustic emission is measured via the at least one fiber optical sensor in form of fibers with Bragg grating, fibre interferometer or Fabry-Perot structure, followed by a signal transfer and an analysis of the measured signals in the processing unit, estimation of the sintering or melting process quality due to correlation between sintering or melting quality and measured acoustic emission signals and subsequent adaption of ion and electron beams, microwave or laser sintering or melting parameters of a ion and electron beams, microwave or laser electronics of the additive manufacturing setup in real times via a feedback loop as a result of the measured acoustic emission signals after interpretation with an algorithmic framework in the processing unit.

The present invention relates to a sensor device comprising an optical fiber to be coupled with a laser beam, a through-fiber fabricated cantilever onto one end of said optical fiber, and a light collector. According to the invention, the through-fiber fabricated cantilever is made of a polymer obtained by photo-structuring at least one photo-sensitive monomer species. The present invention also relates to methods for the measurement of parameters such as temperature, mass, viscosity, analyte concentrations, and the degree of a polymerization process, using the device of the invention.

An optical fiber sensing system includes a sensing optical fiber and one or more optical amplifiers in series with the sensing fiber and arranged to increase the power of sensing pulses travelling along the fiber to thereby increase the range of the sensing system. The optical fiber sensing system is one selected from the group including an optical fiber distributed acoustic sensor (DAS), an optical fiber distributed temperature sensor (DTS), or an optical time domain reflectometry (OTDR) system.

The subject matter of this specification can be embodied in, among other things, a method for remotely sensing vibration includes transmitting a collection of optical pulses through an optical fiber at a predetermined frequency, detecting a collection of backscattered Rayleigh traces from the optical fiber based on a vibration of the optical fiber at a vibration frequency at a location along the optical fiber, determining a normalized differential trace based on the collection of Rayleigh traces, determining, based on the normalized differential trace, the location in the optical fiber of the vibration, and determining, based on the raw Rayleigh traces, the vibration frequency.

Systems and methods for performing the dynamic anomaly localization of utility pole aerial/suspended/supported wires/cables by distributed fiber optic sensing. In sharp contrast to the prior art, our inventive systems and methods according to aspects of the present disclosure advantageously identify a location region on a utility pole supporting an affected wire/cable, thereby permitting the identification and reporting of service personnel that are uniquely responsible for responding to such anomalous condition(s).

Techniques and apparatus are provided for downhole sensing using optical couplers in a downhole splitter assembly to split interrogating light signals into multiple optical sensing branches. Each optical branch may then be coupled to an optical sensor (e.g., a pass-through or an optical single-ended transducer (OSET)) or to another optical coupler for additional branching. The sensors may be pressure/temperature (P/T) type transducers. Some systems may exclusively use OSETs as the optical sensors. In this manner, if one of the OSETs is damaged, it does not affect light traveling to any of the other sensors, and sensing information from remaining sensors is still returned.

Example embodiments include an optical interrogation system with a sensing fiber having a single core, the single core having multiple light propagating modes. Interferometric apparatus probes the single core multimode sensing fiber over a range of predetermined wavelengths and detects measurement interferometric data associated with the multiple light propagating modes of the single core for each predetermined wavelength in the range. Data processing circuitry processes the measurement interferometric data associated with the multiple light propagating modes of the single core to determine one or more shape-sensing parameters of the sensing fiber from which the shape of the fiber in three dimensions can be determined.

Example embodiments include an optical interrogation system with a sensing fiber having a single core, the single core having multiple light propagating modes. Interferometric apparatus probes the single core multimode sensing fiber over a range of predetermined wavelengths and detects measurement interferometric data associated with the multiple light propagating modes of the single core for each predetermined wavelength in the range. Data processing circuitry processes the measurement interferometric data associated with the multiple light propagating modes of the single core to determine one or more shape-sensing parameters of the sensing fiber from which the shape of the fiber in three dimensions can be determined.