3718 results about "Optical fiber sensing" patented technology

A 1D-CNN-based ((one-dimensional convolutional neural network)-based) distributed optical fiber sensing signal feature learning and classification method is provided, which solves a problem that an existing distributed optical fiber sensing system has poor adaptive ability to a complex and changing environment and consumes time and effort due to adoption of manually extracted distinguishable event features, The method includes steps of: segmenting time sequences of distributed optical fiber sensing acoustic and vibration signals acquired at all spatial points, and building a typical event signal dataset; constructing a 1D-CNN model, conducting iterative update training of the network through typical event signals in a training dataset to obtain optimal network parameters, and learning and extracting 1D-CNN distinguishable features of different types of events through an optimal network to obtain typical event signal feature sets; and after training different types of classifiers through the typical event signal feature sets, screening out an optimal classifier.

The invention provides a fiber-optic sensing system, utilizing a fiber-grating-based sensor, for a physical parameter, e.g., a pressure or a temperature. Different kinds of fiber-grating-based sensors may be used for this purpose but in-fiber gratings such as Fiber Bragg Grating, Long Period Grating and Surface Corrugated Long Period Fiber Grating are particularly suitable. Due to the small size of the optical fiber and the fact that same fiber acts as the sensing element as well as the signal conducting medium, it is possible to install the sensor in a small diameter needle which is commonly used for medical diagnosis and treatment. As a result, when the fiber-optic sensing system of the invention is used for in-vivo measurement of a biological parameter, such a sensing needle can be used for different in-vivo pressure or temperature sensing applications without causing too much harm and discomfort to the subject tested.

An optical fiber sensor system comprising of an optical fiber including plurality of sensitive elements, each sensitive element has characteristic spectral band which in normal undisturbed condition lies in a first wavelength range and, under an influence of some specified condition to be detected, shifts to a second wavelength range; first and second wavelength ranges do not overlap. Means for probing an optical transmission or reflection of the fiber operate within second wavelength range to monitor the changes of the transparency or reflectivity of the fiber caused by the shift of characteristic spectral band into the second wavelength range.

The invention provides means for distributed monitoring of equipment or construction structures and detection of specified conditions and can provide alarm signal when the specified conditions become effective.

An integrated optical circuit for use in a fibre optic gyroscope which senses rotation rates by determining a phase shift due to the Sagnac Effect between light beams travelling around an optical fibre sensing loop (4) in opposite directions, the circuit being provided on a silicon-on-insulator chip comprising a layer of silicon separated from a substrate by an insulating layer, the circuit comprising: rib waveguides (11) formed in the silicon layer for receiving light from a light source (2) and transmitting light to a light detector (3), fibre optic connectors (9) in the form of grooves etched in the silicon layer for receiving the respective ends of the optical fibre sensing loop (4); rib waveguides (11) formed in the silicon layer for transmitting light to and from said fibre optic connectors (9) so as to direct light beams in opposite directions around the sensing loop (4) and receive light beams returning therefrom, phase determining means and (13,17,31) integrated in silicon layer for determining a phase shift between the light beams returning from the sensing loop (4).

A method and apparatus for sensing attributes of reflected signals in an optical fiber sensing system is provided. In one embodiment, a method for sensing in an optical fiber sensing system comprising an interrogator coupled to a Bragg grating sensor by an optical cable includes the steps of producing a first optical signal, coupling the first optical signal to an optical cable, receiving a first reflected signal from a Bragg grating sensor within the optical cable, resolving a wavelength of first reflected signal, producing a second optical signal, coupling the second optical signal to the optical cable, receiving a second reflected signal caused by Brillouin backscattering within the optical cable, and resolving a difference in frequencies between the second optical signal and second reflected signal. Embodiments of the method and apparatus are particularly useful for sensing temperature and strain in hazardous locations such as down hole gas and oil field applications and the like.

A fiber optic sensing device uses a Fabry-Perot cavity to sense a physical parameter. The cavity modulates the incident polychromatic light. The modulated light is recorded by an optical spectrometer means. The spectrum is analyzed in a signal processing unit which normalizes the spectrum and determines the phase of the modulated signal. The phase, accumulated over whole range of wavelengths, has been used for identification of the physical parameter using a look-up-table. The cavity, the polychromatic light source and the spectroscope means are connected by fiber optic means.

The invention discloses a distributed optical fiber sensing device based on a chaotic laser coherence method, and a measurement method of the distributed optical fiber sensing device. Chaotic laser light which is emitted from a chaotic laser is divided into detection light and reference light; the detection light is amplified by a light amplifier and then emitted into a sending optical fiber through an optical circulator, and a backward Brillouin scattering light signal is generated in the optical fiber; the Brillouin scattering light signal is amplified by the light amplifier, de-noised by a tunable light filter and then emitted into an optical fiber coupler; the optical length of the reference light is regulated by a variable light delay line, and interferes with the backward Brillouin scattering light signal which is generated by the detection light at different positions in the sensing optical fiber in the optical fiber coupler; an interference beat frequency signal is detected by a photoelectrical detector; and Brillouin gain spectra at different lengths are obtained through a data acquisition device and a signal processing device and then output to a display device, so strain or temperature sensing detection is realized.

There is disclosed a distributed optical fibre sensing system in which the sensor fibre comprises at least first and second waveguides used for separate sensing operations. The sensor fibre may be, for example, a double clad fibre having a monomode core and a multimode inner cladding.

The invention provides a space division multiplexing Mach-Zehnder cascade fiber interferometer and a measurement method thereof. The space division multiplexing Mach-Zehnder cascade fiber interferometer is composed of a wide-spectrum light source, a photodetector, a coupler, a single-mode connection optical fiber, an optical fiber sensor, a continuous-variable optical delay device, and a reflector, wherein the optical fiber sensor is composed of a Mach-Zehnder interferometer and forms a cascade optical fiber sensor array or a network. The wide-spectrum light source and a photodetector are connected with the optical fiber sensor through the coupler to form a sensor network; and the sensor network is connected with the continuous-variable optical delay device and the reflector through the coupler and is used for enquiring and demodulating the optical fiber sensor. The space division multiplexing Mach-Zehnder cascade fiber interferometer solves the problem of breakage of the optical fiber sensor array, improves the anti-damage characteristics of the optical fiber sensor array and the network and solves the temperature compensation problem in the measurement process. The space division multiplexing Mach-Zehnder cascade fiber interferometer has the advantages of simple interferometer structure, easy implementation, improved measurement reliability and low cost, and better facilitates the technology generalization and popularization.

The invention relates to a method and a device for monitoring, also permanently and automatically, temperature distributions and/or temperature anomalies on the basis of distributed fiber-optic temperature sensing as well as to the use of such methods. According to the invention the detection of local temperature extremes, i.e. minimums or maximums, in view of the evaluation is performed by an evaluation without numeric derivations. With the device for monitoring ascending and supply pipes surrounded by an annular space it is possible to check the safety of pressurized installations, particularly in the field of low-pressure gas storage, in a cost-efficient manner. Moreover, the position of an underground watershed or respectively the direction and flow rate of the flows in flooded drift sections can be determined on the basis of fiber-optic temperature measurements. The defined arrangement of preferably vertical sensor cables inserted into the bores also makes it possible to examine the tightness of base sole and lateral walls in building excavations. Finally, the virtually horizontal, meander-shaped arrangement of fiber-optic cables situated in several levels makes it possible to evaluate and control the efficacy and homogeneity of leaching processes in leaching dumps and fills.

The present invention provides a method of using distributed optical fibers for an advanced monitoring of tunnel surrounding rock deformation. A monitoring device related to the method comprises a distributed optical fiber measuring pipe, an optical fiber sensing line, a Brillouin backscattering light data acquisition facility, and a data processing and analyzing software. The method comprises the steps of symmetrically laying sensing optical fibers on the external surface of a PP-R pipe to manufacture the distributed optical fiber measuring pipe, by which the displacement of soil along the measuring pipe can be obtained; embedding the distributed optical fiber measuring pipe in the drilling hole in the overlying surrounding rock of the tunnel, and injecting couplant to form a measuring pipe of a soil-pipe compatible deformation type, wherein the measuring pipe deforms with the synchronous displacement of the surrounding rock; and realizing monitoring of the deformation or displacement of the surrounding rock by measuring the deformation of the measuring pipe. The method provided in the invention has the characteristics of a distributed type, automatic data acquisition, real time and advanced monitoring, etc., and is suitable for monitoring surrounding rock two dimensional deformation or displacement in the geotechnical engineering field such as a tunnel cavern, a coal mine tunnel, etc.

A Sagnac-like optical fiber sending device of low coherent twisted type is prepared as connecting optical source and photoelectric detector at a side of a coupler and connecting another side of said coupler to a closed loop formed by series-connecting various single-mode optical sending arms with 2x2 couplers. The closed loop is featured as out-setting single-mode optical fiber of high reflection surface and single-mode out-set optical fiber, using self-focusing lens and scan-reflector to form demodulation end of optical fiber and returning partial light back to light detector through said single-mode optical fiber.

The invention relates to monitoring technology of power transmission lines, in particular to technology for monitoring ice coating and waving states of the power transmission lines. The invention discloses a method and a device for monitoring the power transmission line by using fiber sensors in real time. The method for monitoring the power transmission line is characterized by comprising the following steps: arranging the fiber sensors along the power transmission line to detect characteristic parameters of different positions of a lead; and judging the state of the power transmission line according to the analysis of the characteristic parameters. The device for monitoring the power transmission line comprises the fiber sensors and a signal transmitting and processing system, and is characterized in that the fiber sensors are arranged along the length direction of the power transmission line and used for detecting and transmitting the characteristic parameters of the different positions of the power transmission line. The method and the device are used for monitoring the ice coating and waving states of the power transmission lines, can fully exert the advantages of the fiber sensors to carry out multi-parameter real-time on-line detection, and have the characteristics that the device has long service life and can work for long time reliably under on-site severe environment conditions.

The invention belongs to the fiber sensing technical field, and specifically relates to a multi-core fiber bragg grating (FBG) universal bending sensor; the multi-core fiber bragg grating (FBG) universal bending sensor is suitable for smart material and structure on-line detection and analysis, can control and monitor space structure space three dimensional positions and attitudes, and is formed by using the multi-core fiber bragg grating (FBG) as the basic sensing unit; the multi-core fiber bragg grating (FBG) universal bending sensor comprises multi-core fibers including one center fiber core, and the resting fiber cores are arranged around the center fiber core in quadrature distribution or symmetrical distribution; each fiber core in the same transverse position of the multi-core fiber uses the same phase mask slice to simultaneously expose the FBG; the central wavelengths of various Bragg gratings on the multi-core fiber are different; the multi-core fiber bragg grating (FBG) universal bending sensor can monitor various reflection wavelength changes of the multi-core FBG, thus measuring the bending amplitude and direction angles.

An optical fiber grating wave length demodulation system belongs to the technical field of optical fiber sensing and optical measurement. The demodulation system comprises a broad band light source (1), a tunable filter (2), a 1x2 coupler, a wave length calibration module, a photodetector, a 1xN optical switch (5) and a signal processing system. The inside connection of the wave length calibration module is that: one end of a standard tool filter (6) is connected with an output end of a third 1x2 coupler (11)m the other end of the standard tool filter is connected with a reference grating (10), an input end of the third 1x2 coupler is connected with an output end of a first 1x2 coupler; the other output end of the third 1x2 coupler is connected with a signal processing system (9) by a second photodetector (4) to implement the wave length calibration. The calibration of the reflected optical fiber grating wave length can be implemented rapidly and accurately by the standard tool filter and the reference grating, the signal can be effectively demodulated for high precision. The system also can be used for monitoring temperature and stress and so on physical quantities.