399 results about "Long-period fiber grating" patented technology

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 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 totally positive dispersion cavity mode-locked all-fiber laser which is a fiber laser structure with high repetition rate and power, simple structure and high efficiency and is an all-fibermode-locked ultrashort laser pulse laser with stable environment and novel structure. The all-fiber laser takes rare earth doped fiber as a laser gain medium, works in a totally positive dispersion area, uses a polarizing beam splitter to split light, uses a band-pass type long-period fiber grating filter for wavelength selectivity of a mode-locked laser centre and spectral filtering light pulse compression of mode-locked laser and takes a semiconductor saturable absorber as fiber laser structures. The totally positive dispersion cavity mode-locked all-fiber laser has picosecond and femtosecond light impulse length polarizing laser output and lasers with the wavelengths longer than 1 micrometer and can be used for pumping-detecting ultrafast light physical experiments or the environmental monitoring and the microwave photonics and biophysics detection of a molecular system, double-wavelength pumping-detecting ultrafast light physical experiments, frequency-combining light radiation generation, coherent anti-Stokes Raman scattering microscopy, micromachining, and the like by being amplified by a high-power fiber amplifier.

The invention relates to a cascade long-period fiber grating device, a manufacturing method thereof, a humidity sensor and a humidity sensing system. The humidity sensing system comprises a broadband light source, a Mach-Zehnder interferometer, a humidity sensitive film, a spectrum collection unit and a data processing unit, wherein the Mach-Zehnder interferometer is formed by connecting two long-period fiber gratings alternately in certain distance; two ends of the interferometer are connected with the broadband light source and the spectrum collection unit; the humidity sensitive film is used for sensing information of environment humidity variations; the spectrum collection unit is used for collecting the information of the environment humidity variations; and the data processing unit is used for analyzing and processing collected optical interference signals containing environment humidity information, and acquiring environment humidity to be detected finally. The spectrum has finer structure and narrower line width, solves the problems of low sensitivity and resolution in the prior art, can perform remote real-time online monitoring, and has accurate measurement and low cost.

The invention provides a sensor structure for simultaneously measuring the temperature and strain of long period fiber gratings (LPFGs). The sensor structure is characterized in that a pair of LPFGs which are written by high-frequency CO2 laser pulse in a fiber and have different periods are selected, namely an LPFG only sensitive to temperature variation and an LPFG sensitive to both temperaturevariation and strain variation; and the respective variation of the temperature and the strain can be accurately measured by cascading the two LPFGs. The sensor structure has the following prominent advantages: the temperature variation is measured by using the LPFG which has a specific period and is only sensitive to temperature variation, and the variation of the temperature and the strain is measured by using the other LPFG, thus realizing measurement of the two parameters (the temperature and the strain), and providing a scheme for solving the problem of cross sensitivity of the temperature and the strain; and meanwhile, the sensor has the capability of normally working at the high temperature of 750 DEG C and is unnecessary to be specially packaged.

The invention provides a biochemical sensor based on a thin-covering layer long-period fiber grating coupling resonant cavity, which comprises a microsphere resonant cavity, a thin-covering layer long-period fiber grating and a carrying silicon substrate, wherein the microsphere resonant cavity is coated with nano-pore zeolite coatings, the microsphere resonant cavity coated with nano-pore zeolite coatings and the thin-covering layer long-period fiber grating are fixed on the carrying silicon substrate engraved with micro grooves and hole grooves, and the distance between the microsphere resonant cavity and the thin-covering layer long-period fiber grating is controlled in a range between dozens of nanometers and hundreds of nanometers through the micro positioning of the carrying silicon substrate, wherein the resonant cavity is in a fractographic resonant mode, and the surface of the resonant cavity generates the fractographic change when the nano-pore zeolite coatings absorb molecules to be detected, so the resonant wavelength is deviated, and the detection is further carried out. The detection on the specified molecules can be realized according to the different hole diameters of the coatings of a zeolite molecular sieve, in addition, the sensitivity can reach the ppm range level or even the ppb range level, and the invention can be widely used in the fields of environment control, industrial process treatment, public safety and the like.

The invention discloses a Bragg grating (FBG) high-speed demodulating system based on cascade-connection long period fiber grating (LPFG), belonging to the optical-fiber intelligent structural healthmonitoring field. The system comprises a broadband light source (1) which is connected with the output end of a Y-shaped fiber optic coupler (3) by monomode optical fiber (2), the input end of the Y-shaped fiber optic coupler (3) is connected with a Bragg grating (4), the other output end thereof is connected with a cascade-connection long period fiber grating (6), the other end of the cascade-connection long period fiber grating is connected with a high-speed photoelectric detector (7), the output end of the high-speed photoelectric detector is connected with a conditioning circuit (8) whichis connected to a computer (10) which his connected with a data acquisition card (9). A demodulating method effectively combines the characteristics of the cascade-connection long period fiber gratingand the monitoring technology of central wavelength of a fiber bragg grating sensor together, has the advantages of high sensitivity, high demodulating speed and low cost, and can be used for shocking and vibrating monitoring of aerospace flight vehicles, bridges, large dams, underwater construction and the like.

The invention discloses a distributed strain and temperature optical fiber sensor based on brillouin scattering. The sensor comprises a light source, an electro-optical modulator, a pulse signal source, a first erbium-doped optical fiber amplifier, a second erbium-doped optical fiber amplifier, a circulator, a first optical coupler, a second optical coupler, double balance detectors, a signal processing system and a sensing optical fiber. The sensing optical fiber comprises a long period optical fiber grating and is an all-solid photonic crystal band gap optical fiber. Output light of the light source is divided into two paths, wherein one path of the output light is modulated to be detection pulse light by means of the electro-optical modulator, is amplified through the erbium-doped optical fiber amplifiers and is input into the sensing optical fiber through the circulator. The sensor can simultaneously obtain temperature and strain with high resolution through a single measurement, and can well solve the problem of cross sensitivity existing in measurement of a brillouin sensor.

The invention provides a method for manufacturing multi-core long-period fiber gratings and a fiber rotation positioning device. The method comprises the following steps of: (1) installing a multi-core fiber which has multiple fiber cores on different planes on the fiber rotation positioning device, wherein a CO2 laser pulse is arranged above the fiber rotation positioning device; (2) adjusting the fiber rotation positioning device so that one fiber core in the multi-core fiber is aligned with the CO2 laser pulse, and carrying out multiple exposure to make a grating on the fiber core; (3) and repeating step (2), and respectively writing gratings into other fiber cores of the multi-core fiber. The invention is convenient to implement, greatly enhances the grating writing quality, enables the manufacturing process to be controlled easily, reduces the multi-core grating writing difficulty, and is suitable for large-scale production. Multiple fiber gratings are integrated into one fiber, thereby enhancing the integration of optical devices in the fiber; and multiple physical quantities can be simultaneously measured.

The invention belongs to the field of micro strain detection technology of high-temperature pipes, and particularly relates to a long period fiber grating strain gauge for micro strain detection of high-temperature pipes, which comprises an H-shaped metal substrate; the metal substrate comprises a first vertical beam, a second vertical beam and a crossbeam; an LPFG (Long Period Fiber Grating)1 is vertically fixed on the first vertical beam; an LPFG2 is horizontally fixed on the crossbeam; two ends of an LPFG3 are freely and vertically fixed on the second vertical beam; the LPFG1, LPFG 2 and LPFG3 are optically connected with one another; and the three high-temperature long period fiber gratings have different characteristic wavelengths. The long period fiber grating strain gauge for micro strain detection of high-temperature pipes has the advantages as follows: as the three high-temperature long period fiber gratings which are distributed in an H shape are adopted, the horizontal and vertical strains of high-temperature pipes can be detected at the same time; a temperature compensation function is provided so that the high-temperature pipes above 200 DEG C can be detected; the structure is simple and the mounting is convenient; and correct and effective detection can be carried out on the two-dimensional strain states of outer walls of the high-temperature pipes.

The simultaneous measurement method of bending curvature and bending direction includes first measuring long period fiber grating bending characteristic and drawing the bending sensitivity curve of resonance wavelength of long period fiber grating LPFGA and LPFGB vs circumferential direction in 360 deg; cascading LPFGA and LPFGB and LPFGC with unimodal fibers and embedding into the measured engineering structure; measuring variation in resonance wavelength; calculating bending curvature; and judging the bending direction of the measured engineering structure based on the variation in LPFGA and LPFGB resonance wavelength and the bending curvature and through comparison with the bending sensitivity curve. The present invention realizes the simultaneous measurement method of bending curvature and bending direction of engineering structure, and the sensor is small, low in cost, compatible with fiber and easy in embedding into the measured engineering structure.

The invention relates to a real time signal multiplexing and demodulating method of a sensor of a full optical fiber long period optical fiber raster array and a device thereof. The invention selects the continuous laser as an optical source, which is provided with the central wavelength at an optical fiber communication wave bond and has an adjustable single longitudinal mode; the frequency of the laser sent by the optical source is demodulated, and then the laser is distributed to a reference light path and a measuring light path by an optical fiber isolator and an optical fiber coupler according to light intensity fixed proportion. The laser entering the reference light path is all reflected by a FLM. The laser entering the measuring light path is distributed into the branch measuring light path of i path, and the light intensity introduced by LPG after waste is reflected by the FLM. The light intensity reflected by each branch measuring light path is coupled and then passes through a 2 is multiplied by 2 optical fiber coupler again together with the light intensity reflected by the reference light path to produce a beat frequency signal. The wavelength drift rate of the central wavelength of the corresponding LPG is confirmed by analyzing the beat frequency signal. The method has the high measuring precision, has the advantage of low cost and is suitable for the integration and the instrumentation.

The invention relates to an allfiber type long period fiber grating solution multi-parameter sensing system. Broadband light source output light enters the input end of a 2*2 fiber coupler by a compound long period fiber grating; one path of output light of the 2*2 fiber coupler enters a first fiber Bragg grating; the other path of the output light enters a second fiber Bragg grating by a fiber isolator; the reflected light of the two fiber Bragg gratings is collected by a data capture card after entering a photoelectric conversion module and a signal amplifier; and a computer carries out data processing and real-time measurement result display. In the multi-parameter sensing system, the compound long period fiber grating serves as the sensitive elements of a plurality of parameters, matched fiber Bragg gratings serve as signal demodulation elements to realize the allfiber type multi-parameter sensing system. The allfiber type long period fiber grating solution multi-parameter sensingsystem has the advantages of electromagnetic interference, allfiber type measurement and the like and can be remotely monitored.

Fiber optic coupler averagely distributes light intensity of light source in wide band into multiple LPGPs possessing different path differences. Multiplex is accomplished after each path of signal light is converged. Through a light unidirectional isolator, multiplex signal light enters into 3-dB fiber optic coupler. Through collimator of optical fiber, two beams of signal light are sent to reflector, and reflective back to optical fiber. Controlling position movement of one reflector compensates phase difference introduced by LPGPs in different path differences. Compensated two paths of optical signal are converged and intervened at 3-dB fiber optic coupler. The intervened pattern is converted to electrical signal by photo diode; and the signal is collected by data collection card so as to complete demodulation. Advantages are: low cost, suitable to integration and combined to instrument.

Disclosed is a double LPFG temperature and humidity sensor. A temperature sensibilizing straight bar, a supporting straight bar and a metal casing are axially arranged between two sensing bodies, wherein a temperature sensitive LPFG is arranged on the temperature sensibilizing straight bar, a humidity sensitive LPFG is arranged in the metal casing, and tail fibers of the temperature sensitive LPFG and the humidity sensitive LPFG are welded together. When temperature and humidity in the external environment change, effective refractive indexes of a fundamental core mode and a cladding mode of the LPFG, grating period, resonant wavelength and refractive index change, then information of the temperature and the humidity of the environment can be obtained through detection of transmission wavelengths of the temperature sensitive LPFG and the humidity sensitive LPFG, and double parameters can be measured simultaneously. The double LPFG temperature and humidity sensor has the advantages of high measurement accuracy, simultaneous measurement of the temperature and the humidity, and the like; and can be used as the sensor which can measure the temperature and the humidity simultaneously.

The invention relates to a femtosecond laser programmed type pixel-level long-period fiber grating manufacturing device. A designed programmed type control system realizes the writing of femtosecond laser to long-period fiber grating fixed on optical fiber of a high-precision three-dimensional displacement platform, and the manufactured long-period fiber grating has uniform modulated refractive index, the writing of the long-period fiber grating with tunable resonant wavelength and resonant peak can be realized by controlling the mobile distance and reciprocating times of the three-dimensional displacement platform, and the femtosecond laser programmed type pixel-level long-period fiber grating manufacturing device has the characteristics of small writing loss and high femtosecond laser utilization rate. Through the design of the programmed type system, the writing of the long-period fiber grating with tunable resonant wavelength and resonant peak can be realized by utilizing femtosecond. The manufactured femtosecond laser programmed type pixel-level long-period fiber grating manufacturing device has the advantages of low noise, no backward reflection, long resonant wavelength, easiness in tuning, controllability on the depth of resonant peak, and the like, thus providing an efficient preparation method with tunable parameters for applications in the fields of scientific research, fiber-optical communication and optical fiber sensing technology.

The invention relates to a cascade acoustic microstructure optical fiber long cycle grating interferometer which comprises a light source, a 3dB coupler, a microstructure optical fiber, two three-dimensional regulation frames, a signal generator, a piezoelectric ceramic chip, an acoustic amplifier, an acoustic damper, a spectrum analyzer, a connecting single-mode optical fiber and a lead, and belongs to the technical field of optical fiber induction. A sine electric signal is generated through the signal generator, acts on the piezoelectric ceramic chip, is converted into an acoustic signal, amplified through the acoustic amplifier and laterally loaded to the microstructure optical fiber to form an acoustic long cycle optical fiber grating, and then a Mach-Zehnder interference effect is formed through a high reverse film; and an induction optical fiber is corroded to generate an evanescent field and is arranged in an environment to be measured. In addition, a functional material is filled into the cladding air hole of the microstructure optical fiber, so that an electric field, a magnetic filed and the like can be measured and the induction sensitivity is further improved. The cascade acoustic microstructure optical fiber long cycle grating interferometer has the advantages that the structure is simple, the tunability is good, the sensitivity is high, and refractive index, temperature, the electric field, the magnetic field, gas concentration and other parameters can be induced.

The invention discloses a structural long-period optical fiber grating. The structural long-period optical fiber grating comprises a shaft and a spiral line, wherein the spiral line is wound on the surface of the shaft to form a periodical spiral structure; the diameters of the cross sections of the shaft and the spiral line are in level of micron or nanometer; and the diameter of the cross section of the shaft is larger than that of the cross section of the spiral line. The structural long-period optical fiber grating disclosed by the invention has the advantages of being simple in manufacturing process, low in manufacturing cost, simple in structure, compact, smart and the like; and in addition, the structural long-period optical fiber grating can simultaneously realize functions of band pass filtering and band elimination filtering.

The invention provides a tapered-waveguide-assisted cascade long-period waveguide grating sensor and a preparation method thereof. The sensor is formed by connecting a first long-period waveguide grating with a second long-period waveguide grating through a tapered waveguide. The Mach-Zehnder effect of a cascade long-period waveguide grating is combined with the characteristic of strong evanescent field high sensibility of the tapered waveguide by the sensor, so that the sensor has the good characteristics of high sensibility and quick response. The sensor adopts the manufacturing processes of simple and mature ultraviolet photoetching method and reactive ion etching method. Compared with a composite device consisting of a long-period optical fiber grating and an optical fusible cone, the invention has the advantage that the sensor has a wide application prospect in the field of optical waveguide sensing devices, and is simple in structure, high in sensitivity and convenient to manufacture.

The invention relates to a fiber grating sensor, comprising a broadband light source, a photonic crystal optical fiber, a spectrum acquiring module and a data processing module, wherein, the broadband light source is used for providing light source to the spectrum acquiring module; the two end of the photonic crystal optical fiber are connected with the broadband light source and the spectrum acquiring module with a single mode optical fiber, and the photonic crystal optical fiber is provided with an asymmetric long period fiber grating for sensing the bending deflection of a object which is to be measured; the spectrum acquiring module is used for acquiring the information of the bending deflection; the data processing module is used for analyzing and processing the acquired information of the bending deflection so as to finally obtain the curvature and the bending direction of the bending deflection. The invention can simultaneously measure curvature value and positive/negative direction.

The invention discloses a long-period fiber bragg grating manufacturing method based on the ink-jet printing technology. The long-period fiber bragg grating manufacturing method based on the ink-jet printing technology is characterized in that firstly, a fiber coating of an optical grating writing zone is stripped off, so that a fiber cladding is exposed and a fiber is fixed on a fiber clamp; the ink-jet printing technology is adopted, photoresist coatings with periodical intervals cover the fiber cladding and the photoresist coatings are dried; an argon ion ultraviolet laser with the wavelength of 248nm is adopted and the exposed fiber cladding is scanned and exposed. The fiber cladding which is not covered by the photoresist coatings and a fiber core located in the fiber cladding sense light and variation of the photoinduced refractive indexes is generated through the light-sensing fiber core; the photoresist coatings are removed to manufacture a long-period fiber bragg grating. By means of the ink-jet printing technology, an image structure with the grating period can be rapidly printed on the surface of the fiber cladding. The long-period fiber bragg grating manufacturing method is simple and rapid in manufacturing process, suitable for being manufactured in batches and good in consistency.

The invention discloses a dotted groove type optical fiber cladding surface Bragg raster, which is characterized in that the optical fiber cladding surface Bragg raster is arranged on the outer surface of the optical fiber cladding of the single mode fiber; the optical fiber cladding surface Bragg raster consists of a plurality of dotted grooves which cause the structural damage to the optical fiber cladding and have periodicity; and the center points of all dotted grooves are in the same line which is parallel with a center axis of the optical fiber. The dotted groove type optical fiber cladding surface Bragg raster is unique in structure, simple in manufacture method, miniaturized and fiber-optical. The invention has a characteristic sensitive to the outside medium, which is similar to the long period optical fiber bragg gating, has a high Q value factor and has a cross sensitivity effect which is much lower than the long period optical fiber bragg gating; the temperature, pressure and the strain sensitivity are higher than that of the traditional optical fiber Bragg raster; the raster zone of the optical fiber cladding has obvious double refraction effect and can be widely applicable to the fields like the biology, chemical engineering, medical science, the bioscience, etc.

Through LPGP, light in broadband generates optical path difference caused by refringence between core layer and clad layer in optical fiber. The optical path difference is compensated by a scannable Michelson interferometer so as to obtain interference fringe. Intensity of interference fringe is sensitive to curvature of LPGP. Carrying out Fourier transform for interference fringe obtains centered wavelength of loss peak of macrocyclic optical fiber grating spectrograph in LPGP. The location of wavelength is sensitive to temperature signal. The invention obtains signal of dual parameters of LPGP sensor. Through matrix method, the invention eliminates crossing influence between parameters. Features are: low cost, suitable to integration and to instrument.

Long-period fiber gratings are placed in a predetermined pattern along a double-clad optical fiber having an outer cladding, an inner cladding and a core. The core is doped with an optically active material such as, for example, a rare earth ion or other laser ion. The long-period fiber gratings couple light between a mode of the inner cladding and a mode of the core. As a consequence of increased coupling into the core resulting from the use of long-period fiber gratings, the length of double-clad optical fiber needed to transfer light between the inner cladding and the core is reduced.

The invention belongs to the technical field of optical fibers, and particularly relates to a fiber bragg grating microstructure beam splitter with double filtering functions. A broad band optical source (1) is connected with an input end of a single mode optical fiber (2); an output end of the single mode optical fiber (2) is connected with an input end of a multimode optical fiber (4); a long-period fiber grating is written into the multimode optical fiber; and an output end of the multimode optical fiber (4) is connected with a CCD (Charge Coupled Device) detector. Diameter (d) of the core of the multimode optical fiber is less than 125 microns and more than or equal to 105 microns. The single mode optical fiber and the multimode optical fiber are connected by dislocation welding. The multimode optical fiber can be replaced by special optical fibers such as double-core optical fibers, annular-core optical fibers and three-core optical fibers. Compared with the method for simply writing the fiber grating into the multimode optical fiber, the beam splitter has high stability and controllability. The optical fiber material and the device are standard optical fiber communication elements, therefore, the beam splitter has the advantages of simple structure, small volume, low cost and high accuracy in comparison with the prior beam splitter.

The present invention discloses a process for making long period optical fiber grating for sensing and detecting degree of strain and temperature characterized by that, using the infrared pulsed laser beam directly and gradually irradiating on the bare optical fiber core periodically point-to-point, making the refractivity of the optical fiber core change periodically forever. By selecting different optical fiber core material and packing material, the optical fiber grating of different characteristics can be made, with temperature and stress response sensitivity raised by more than 100 times of that of the optical fiber grating for communication, it can be buried inside the measured object and material, resulting the simultaneous distinction and real time monitoring for pressure and temperature.