4839 results about "Fiber gratings" patented technology

A medical instrument system includes an elongate flexible instrument body with an optical fiber substantially encapsulated in a wall of the instrument body, the optical fiber including one or more fiber gratings. A detector is operatively coupled to the optical fiber and configured to detect respective light signals reflected by the one or more fiber gratings. A controller is operatively coupled to the detector, and configured to determine a twist of at least a portion of the instrument body based on detected reflected light signals. The instrument may be a guide catheter and may be robotically or manually controlled.

A loss-less, optical add/drop multiplexer according to the present invention includes a rare earth-doped fiber amplifier integrated with a wavelength-selective fiber path coupled between two directional optical transfer devices for selectively adding and dropping optical signals from a multi-wavelength signal, such as a wavelength division multiplexed optical signal. One or more fiber gratings are disposed along the length of the rare earth-doped fiber amplifier or between segments of the rare earth-doped fiber so that at least one grating is used for reflecting each optical signal that is expected to be added to or dropped from the multi-wavelength optical signal. By using this configuration, appropriate amplification is provided to compensate for losses in the add, drop, and through paths.

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.

A large diameter optical waveguide, grating, and laser includes a waveguide 10 having at least one core 12 surrounded by a cladding 14, the core propagating light in substantially a few transverse spatial modes; and having an outer waveguide dimension d2 of said waveguide being greater than about 0.3 mm. At least one Bragg grating 16 may be impressed in the waveguide 10. The waveguide 10 may be axially compressed which causes the length L of the waveguide 10 to decrease without buckling. The waveguide 10 may be used for any application where a waveguide needs to be compression tuned, e.g., compression-tuned fiber gratings and lasers or other applications. Also, the waveguide 10 exhibits lower mode coupling from the core 12 to the cladding 14 and allows for higher optical power to be used when writing gratings 16 without damaging the waveguide 10. The shape of the waveguide 10 may have other geometries (e.g., a “dogbone” shape) and/or more than one grating or pair of gratings may be used and more than one core may be used. The core and/or cladding 12,14 may be doped with a rare-earth dopant and/or may be photosensitive. At least a portion of the core 12 may be doped between a pair of gratings 50,52 to form a fiber laser or the grating 16 or may be constructed as a tunable DFB fiber laser or an interactive fiber laser within the waveguide 10. The waveguide may resemble a short “block” or a longer “cane” type, depending on the application and dimensions used.

In certain variations, fiber shape sensing or measuring systems, devices and methods are described herein, which allow for measurement of three dimensional bending as well as twist measurements of various fibers, e.g., optical fibers and fiber optic probes of various sizes. In certain variations, the systems are designed to take advantage of unique light guiding properties of optical fibers and various fiber gratings.

The invention relates to a method for monitoring the stress of a casing in a well by applying optical-fiber sensors, which mainly solves the problem that the existing research field of the casing erosion of an oil field and oil-water well does not have a direct method for monitoring the stress loading process of the casing in the well and the morphological characters of the casing erosion. The method is characterized in that: optical-fiber grating sensors are circumferentially arranged along the outer surface of the casing; a ground optical-fiber grating demodulation instrument connected with the optical-fiber grating sensors is utilized to monitor the circumferential strain Epsilon Theta of the casing and obtain the circumferential strain data of the casing; meanwhile, Brilliouin optical-fiber sensors are axially arranged along the outer surface of the casing; a ground Brilliouin optical-fiber demodulation instrument connected with the Brilliouin optical-fiber sensors is utilized to monitor the axial strain Epsilon Z of the casing and obtain the axial stain data of the casing; and the obtained circumferential strain Epsilon Theta and the axial strain Epsilon Z of the casing are utilized to obtain the stress of the outer layer of the casing in the well according to a ground stress explanation model. The method is characterized by being capable of permanently monitoring the deformation of the casing and obtaining corresponding stratum pressure under the condition without knowing the casing erosion and the stratum pressure.

A sensing module positioned about an optical fiber cable having a long axis. The optical fiber includes a core that transmits light through the optical fiber cable. The sensing module includes a first short-period fiber grating positioned about the core. A second short-period fiber grating is positioned about the core and at a distance along the long axis with respect to the first short-period fiber grating. At least one of a long-aperiod fiber grating and a long-period fiber grating is positioned between the first short-period fiber grating and the second short-period fiber grating. A fiber cladding is positioned around the long-period grating and/or the long-aperiod grating of the sensing module. A sensing skin is positioned about the fiber cladding and includes a chemical gas active material.

The invention discloses a fully distributed optical fiber strain and vibration sensor comprising a laser (1), a first coupler (2), a pulse modulation module (3), an optical amplifier (4), a circulator (5), a sensing optical fiber (6), a fiber bragg grating (7), a polarization scrambler, a second coupler, a balance photoelectric detector, an analyzer, a photoelectric detector (12) and a signal processing unit. Continuous light output by the laser (1) is split into two paths through the first coupler (2), wherein one path is used as reference light and is accessed to a first input end of the second coupler (9) through the polarization scrambler (8); and the second path is processed by the pulse modulation module (3) and the optical amplifier (4) and then used as detection pulse light to be injected into a first port of the circulator (5). In the invention, Brillouin optical time domain reflectometry (BOTDR) and polarization optical time domain reflectometry (POTDR) are simultaneously utilized for respectively and correspondingly carrying out fully distributed measurement on strain and vibration on a signal optical fiber, the defects of a system with single BOTDR or POTDR are overcome, and the false alarm rate or missed report rate of the system is decreased.

A coal mine underground safety comprehensive monitoring system based on fiber grating sensors and belongs to a coal mine underground safety monitoring system. The system comprises an aboveground part and an underground part; the aboveground part comprises a static fiber grating demodulator, a computer data processing system, a printer, a server and a client; the underground part comprises an optical switch array, a working face safety monitoring subsystem and a laneway safety monitoring subsystem; each of the two monitoring subsystems at least comprises a monitoring base station; each monitoring base station at least comprises a survey station; each survey station is corresponding to one group of fiber grating sensors; the advantage is that the system adopts multiple survey stations to perform underground multi-parameter monitoring, integrates the fiber grating sensors, adopts all-optical survey and optical fibers for signal transmission, is intrinsically safe, has high anti-electromagnetic interference capability and a good monitoring effect, realizes real-time continuous long-term on-line monitoring and the sharing of data in an entire mining area to better guide the safety production of a coal mine, can effectively reduce safety accidents of the coal mine and realizes safe and efficient production of the coal mine.

The invention provides a fiber grating-based transformer internal temperature detection system, which comprises a light source, fiber grating sensors, a grating signal demodulation system, a signal processing display instrument and data analysis software, wherein the fiber grating sensors are arranged on a winding and a strut of a transformer and sensing points at other positions in the transformer and used for sensing measurement of transformer temperature, stress and local discharge parameters; the grating signal demodulation system receives the measured data of the fiber grating sensors, and accurately demodulates corresponding light signals of the temperature, stress and local discharge parameters; the signal processing display instrument performs correction processing such as temperature compensation, stress sensitivity removal and the like on the measured signals, and displays real-time data on an instrument panel; and the data analysis software performs programming software analysis on the processed data to acquire real-time transformer internal temperature field and temperature change, and then performs transformer internal temperature monitoring and full service life assessment. The system realizes real-time measurement of temperature of multiple points in the transformer through the photoelectric sensors, and provides a good foundation for economic operation of the transformer.

The invention discloses a fiber bragg grating array-based phase-sensitive optical time domain reflection device and method. The device includes a light source, a laser frequency adjustment module, a modulator, an optical fiber amplifier, a circulator, a sensing optical fiber, a light detector, a data acquisition module and a data processing module; the sensing optical fiber is provided with an optical fiber array formed by a plurality of FBGs (fiber bragg grating) which are arranged equidistantly; the laser frequency adjustment module is used for frequency adjustment of continuous light emitted by the light source; the continuous light is modulated by the modulator so as to form pulsed light; the optical fiber amplifier performs power amplification on the pulsed light; the sensing optical fiber is used for receiving and transmitting the pulsed light which has been subjected to power amplification; the light detector receives scattered light and reflected light; the scattered light and reflected light are acquired by the data acquisition module; and the data processing module generates interference signal frequency response spectrum and obtains the length variation quantity of the sensing optical fiber between two adjacent FBGs through processing. With the fiber bragg grating array-based phase-sensitive optical time domain reflection device and method of the invention adopted, strain quantitative detection can be realized, and high-spatial resolution measurement can be realized based on quantitative analysis.

A tunable interferometer for creating an interference pattern of variable periodicity at a fixed location is disclosed. The interferometer includes an optical element for splitting an input beam into a first write beam and a second write beam which are parallel to one another and have a variable distance therebetween. The interferometer also includes a beam directing element for receiving the parallel first and second write beams to intersect at the fixed location with an angle of intersection which is a function of the variable distance between the parallel first and second write beams received.

The invention discloses a fiber grating sensing layer-divided sinking apparatus for observing unconsolidated strata sedimentation, a data monitoring processing system, a grating sensor and an implantation method. The fiber grating sensing layer-divided sinking apparatus comprises a grating sensor and a grating sensor array, wherein the grating sensor array is used for applying a light source to the grating sensor through a broadband light source of a fiber grating demodulator and a coupler; a light signal returned by the grating sensor is input to the fiber grating demodulator through the coupler; the fiber grating demodulator is used for converting the light signal into an electric signal and calculating a center wavelength value of each grating sensor; the monitoring processing system is connected with a wavelength data acquiring module, a data analysis module, a time display wavelength module, a real-time monitoring curve module, an information prompt module, a forecasting alarm system module and the like respectively; and another path of data analysis is connected with a memory and a data processing module respectively. The device is simple in structure, not influenced by a severe environment, resistant to corrosion and electromagnetic interference, safe and reliable, convenient to use and widely applied to strata sedimentation; and sensing and transmission are integrated.

The invention relates to a fiber grating strain and temperature simultaneously measuring sensor. A fiber grating strain sensor is formed by utilizing a second stainless steel pipe to package bare fiber grating, a fiber grating temperature sensor is formed by utilizing a metal pipe to package bare fiber grating, and the fiber grating strain sensor and the fiber grating temperature sensor are packaged in parallel in a first stainless steel pipe by adopting epoxide resin. When the sensor is arranged on an engineering structure, the first stainless steel pipe produces the distortion and transmits the temperature and the strain of the structure to the fiber grating strain sensor at the inner part and the fiber grating temperature sensor without strain influence through the epoxide resin, the measuring value of the strain sensor is compensated by the temperature sensor so as to achieve the simultaneous measurement of the strain and the temperature of the structure.

A a chiral fiber grating mimicking a cholesteric liquid crystal structure to achieve fiber Bragg grating properties, is provided. The chiral fiber grating includes a first and a second helical structures disposed along its central longitudinal axis, where the second helical structure is identical in orientation to the first helical structure but is shifted by one half of the structure's pitch forward. In another embodiment of the invention, only a single helical structure is disposed along the fiber to create an optically resonant chiral fiber.

The invention discloses a testing device and a testing device method for simulating collapse of tunnel surrounding rock under conditions of rainfall and underground water seepage. The testing device comprises a model testing box, a rainfall adjustable simulating system, an underground water seepage simulating system, an underground water supplying system, a water content testing system, a stress monitoring system, a digital radiography noncontact measuring system and an optical fiber bragg grating displacement monitoring system. By simulating a progressive failure process of tunnel weak broken surrounding rock under the action of seepage of surface water and underground water, mechanical behaviors of crushing the surrounding rock under different rainfall conditions and different underground water seepage path conditions are quantitatively researched. By obtaining multiple-physical field information in a tunnel surrounding rock collapse process, multi-information features in different evolutionary phases and internal links of information of all fields of the collapse are analyzed, a progressive failure process and fracture morphology and ranges of the tunnel weak broken surrounding rock under different factors are determined, and the effective basis is provided for disclosing a progressive failure principle and a dynamic pressure arch effect of the weak broken surrounding rock under conditions of rainfall and underground water seepage.

The invention discloses a method and system for monitoring a plurality of control parameters of a synchronous grouting process behind a segment wall during shield tunnel piercing construction in a fiber grating sensing and optical fiber communication mode. The method and system is mainly characterized in the remote and real-time multi-parameter monitoring, namely various fiber grating sensors which are pre-buried in segment control positions are used to perform remote and real-time monitoring on control parameters of pore water pressure, soil pressure, segment temperature, concrete stress, rebar stress and other control parameters in synchronous grouting process behind a segment wall, and the grouting pressure can be adjusted according to the monitoring data so as to ensure the grouting to be finished smoothly and ensure the grouting quality. The method and system is strong in practical applicability and feasibility, can monitor any link in the synchronous grouting construction behind the tunnel segment wall and can improve the controllability of the synchronous grouting process and the grouting quality.

A matched pair of tilted gratings may be formed in a section of optical fiber (or waveguide) and used as a “tap” to measure the power of an optical signal passing through the fiber. By using a pair of highly-tilted gratings (e.g., tilted at an angle of 45° with respect to the optical axis) and orienting the gratings to be orthogonal with respect to one another (i.e., azimuthal orthogonality around the fiber axis), a pair of orthogonally polarized beams will be out-coupled from the propagating signal. Since the pair of beams are orthogonal, their sum can be made insensitive to variations in polarization of the optical signal propagating along the fiber.

The invention discloses a fiber bragg grating detection system device and method for detecting an anchoring force of an anchor rod. The fiber bragg grating detection system device consists of a fiber bragg grating sensor array, a fiber bragg grating anchor rod dynamometer, a fiber bragg grating demodulator, an optical cable and a computer, wherein the fiber bragg grating anchor rod dynamometer mainly comprises a plurality of fiber bragg grating sensors which are uniformly arranged on an annular elastic body arm and is arranged at the end part of the anchoring end of the anchor rod; meanwhile, the fiber bragg grating sensor array is distributed on a rod body of the anchor rod; the fiber bragg grating sensor array and the fiber bragg grating anchor rod dynamometer are respectively connected with the fiber bragg grating demodulator through the optical cable; and the fiber bragg grating demodulator is connected with the computer. According to the fiber bragg grating detection system device, the real-time detection on the stress of the anchor rod can be realized and the distributed measurement can be realized. The fiber bragg grating detection system device has the advantages of simple structure, convenience in mounting, high detection speed, long-distance monitoring, repeated use and easiness in protection and maintenance, and is widely applied to tunnels and slopes dug for coal mines, metallurgical mines, water conservancy, railways, roads and defense.

The invention provides a three-dimensional microscale measuring device and method based on a four-core fiber grating, and belongs to the technical field of precision instrument manufacturing and measurement. The device comprises a broadband light source, an optical spectrum analyzer, an optical circulator, a control computer, a multi-way optical switch and an external reference grating. The multi-way optical switch is communicated with a four-core fiber fan-out device through four single mode fibers. One end of a four-core fiber is connected to the four-core fiber fan-out device. A four-core fiber grating probe is fixedly installed at the other end of the four-core fiber through a probe clamp holder. The four-core fiber and the four-core fiber grating probe are connected to form a closed circuit. According to the method, the multi-way optical switch is controlled by the control computer to switch optical paths, the optical spectrum analyzer is used for measuring reflectance spectra of the fiber gratings, and three-dimensional microscale measuring without temperature coupling is realized by utilizing a differential data processing algorithm. The three-dimensional microscale measuring device and method based on the four-core fiber grating have the advantages that accuracy is high, contact force is small, the device and method are not affected by the masking effect, and the service life of the probe is long.