75 results about "Birefringent fiber" patented technology

A method and device for measuring the current in a conductor are presented. They utilize the Faraday effect on counter-propagating circularly polarized beams of light in a fiber optic coil. The light beams are transformed to and from circular polarization by a polarization transformer comprised of a birefringent fiber with a twist through an appropriate angle at an appropriate distance from one end.

The invention relates to a method for detecting micro photoelectrons, in particular to a method for detecting temperature and a magnetic field simultaneously based on a magnetofluid-filled crystal fiber loop mirror. According to the method, magnetofluid is selectively filled into air holes of a structurally-symmetrical photonic crystal fiber along the center line in the horizontal direction; the birefringence characteristic of the photonic crystal fiber is changed accordingly, and a temperature/magnetic field-adjustable birefringent photonic crystal fiber is formed; a traditional birefringent fiber in a Sagnac fiber loop mirror is replaced by the temperature/magnetic field-adjustable birefringent photonic crystal fiber, the distance between two adjacent resonance valleys and the drift distance of the resonance valleys are changed along with the changes of the temperature and the magnetic field with different change sensibilities, and accordingly the temperature and the magnetic field can be simultaneously detected through the two-parameter matrix method. The method improves the stability performance and measuring sensitivity of a sensor, solves the problem of cross sensitivity of the temperature and the magnetic field of the optical fiber sensor and achieves the purpose of measuring the temperature and the magnetic filed simultaneously through one optical fiber.

The invention relates to a fiber optic interferometric system for reducing the influence of fiber birefringence. Laser is emitted by a laser device and transmitted to a fiber optic coupler through a source fiber; the laser is split by the coupler and then output to a metric arm and a reference arm of the fiber optic interferometric system respectively, wherein, one path of light is incident to light reflection device of the metric arm through a fiber optic depolarizer of the metric arm and an optical fiber of the metric arm; the reflected light returns to the fiber optic coupler through the original path; the other path of light is incident to a light reflection device of the reference arm through a fiber optic depolarizer of the reference arm and an optical fiber of the reference arm; the reflected light returns to the fiber optic coupler through the original path; the two path of reflected light form an interference light signal in the coupler; the signal is received by a photoelectric detector as an interference signal through an optical fiber of the detector; and the interference signal is transmitted to an operational processing system through a signal transmission line to obtain the size of the outside physical quantity signal. The fiber optic interferometric system used for metering outside physical quantities such as vibration eliminates the influence of the random variation of the polarization state in the ordinary fiber optic interferometric system on the signal of the fiber optic interferometric system.

The invention discloses an all-fiber current transducer, belonging to the field of electric power measurement and comprising a sensing optical fiber and an electronic sensor which are connected by an optical cable. The all-fiber current transducer is characterized in that the electronic sensor comprises a light source, an optical coupler, a polarizer and a polarized light modulator which are sequentially connected by a cable. The electronic sensor further comprises a differential light receiving device connected with the optical coupler by the cable; the differential light receiving device is also electrically connected with a signal processor; and two Faraday reflecting mirrors are arranged on the sensing optical fibers. The invention can effectively inhibit the influences from double refraction of the optical fiber, the temperature, the vibration and the like and has the potential for realizing high precision and highly reliable measurement.

The invention discloses a polarization control method, based on the genetic algorithm, of a distributed optical fiber disturbance positioning system. In the polarization control process, the genetic algorithm is adopted as a control algorithm, and an extrusion-type polarization controller is adopted to modulate the polarization state of interference optical waves; with the relevancy of two interference signals received by a detector in the distributed optical fiber disturbance positioning system as a feedback signal, the impressed voltage value, corresponding to the maximum relevancy of two interference signals, of the extrusion-type polarization controller is searched for according to the genetic algorithm. A polarization control system comprises a distributed optical fiber disturbance sensing system based on the dual Mach-Zehnder interferometer principle, the extrusion-type polarization controller, a lithium niobate birefringence phase modulator, a single-chip microcomputer system and a computer. According to the polarization control method of the distributed optical fiber disturbance positioning system, the polarization-induced fading resistance of the system can be effectively improved by adjusting the polarization state of interference light, and the influence of birefringence of single-mode optical fibers on the positioning precision of the system can be eliminated to a great extent.

The invention relates to an axial strain measurement method based on a birefringent fiber environment. On the basis of constructing the existing axial strain measurement device for the birefringent fiber environment, axial strain is measured by choosing an optimal monitoring point. Not only can the smooth measurement of the strain be ensured, but also the strain flexibility is improved. Compared with a structural innovation method for improving the strain flexibility, the axial strain measurement method based on the birefringent fiber environment is simple and easy.

The invention discloses an interferometric sensor based on a microstructured optical fiber selectively filled with functional materials. A birefringent microstructured optical fiber selectively filled with functional materials is used as a sensing head, and the functional materials are selectively filled into two adjacent air vent holes in the periphery of a fiber core of a refractive index guiding microstructured optical fiber in which triangular lattice air vent holes are distributed, so that birefringent fiber with a transmission mechanism of mixing refractive index and photonic band gap is realized. As null characteristic that group birefringence of the birefringent fiber is at a specific wavelength is utilized, and a transmission spectrum of a Sagnac fiber optic interferometer comprising the birefringent fiber presents a spectral characteristic different from that of a common interferometer, the interferometric sensor has superhigh response sensitivity to outside parameters. The interferometric sensor based on the microstructured optical fiber selectively filled with the functional materials has the advantages of flexibility in realizing manner and high sensing sensitivity and capability of being widely applied in high sensitivity sensing measurement of parameters such as temperature, refractive index and the like as well as manufacturing fields of optical elements such as photoswitches, tunable filters and the like.

A dual wavelength optical fiber distributed feedback laser comprises a pump laser coupled to a birefringent fiber in which a first grating device (two co-located single phase-shift fiber Bragg gratings (FBGs)) is provided. The grating device gives the laser two potential lasing modes in each of two orthogonal polarization states. A polarization mode coupling FBG selects two orthogonally polarized modes on which the laser oscillates. In a photonic data carrying signal source, the laser is coupled to a polarization dependent, optical modulator operable to apply a modulation, at a data signal frequency, to one polarization mode of the laser output. In an optical waveguide based electronic signal transmission system the modulated and un-modulated polarization modes output from the source are transmitted across a fiber transmission line to a polarizing optical fiber in which the two modes heterodyne to generate an electronic carrier signal in the optical domain.

The invention discloses an all-fiber optical current transformer detection system. The all-fiber optical current transformer detection system comprises a sensing optical fiber ring, a light path system, a circuit system and a merging unit; the sensing optical fiber ring is used for acquiring a current signal of a to-be-detected position and generating a light intensity signal carrying data information of a Faraday rotation angle; the light path system is used for transmitting the data information to the circuit system by virtue of the optical fiber; the circuit system is used for receiving data information transmitted by the light path system and converting the data information to a circuit digital signal; the merging unit is used for receiving the circuit digital signal generated by the circuit system and outputting an identification signal. The current transformer adopts a special optical fiber winding way, so that the temperature drift can be effectively inhibited, the influence of the birefringence phenomenon on detection precision of an ordinary optical fiber transformer can be overcome, the birefringence phenomenon is influenced by the temperature, so that the precision drift of the detection precision caused along with the temperature variation exists.

Methods and apparatus to measure visual appearance of birefringent fibers are disclosed. One method comprises emitting light, creating N_i polarization states of the emitted light, illuminating the birefringent fibers with the emitted light so polarized, thereby generating IR_i internal reflection components, ER_i external reflection components, and D_i diffusion components of the light in the birefringent fibers, observing the light from the illuminated birefringent fibers, creating O_i polarization states of the observed light, forming X_i images of the observed polarized light, each image comprising an information (N_i, O_i, IR_i, ER_i, D_i), wherein i=1, 2, . . . n and n≧4, measuring the intensity I_i in each pixel in the X_i images, and separating the i-th internal reflection component, the i-th external reflection component, and the i-th diffusion component from the i-th image for the X_i images.

The invention provides a single-mode fiber birefringence measurement device and method, belongs to the technology of fiber sensing, and relates to a single-mode fiber birefringence measurement method. The device and method aim to achieve single-mode fiber birefringence measurement. An optical signal of a pump light source is transmitted to an optical signal input end of a wavelength division multiplexer through an optical fiber after passing an optoisolator, an optical signal output end of the wavelength division multiplexer is connected with one end of a fiber grating, the other end of the fiber grating is connected with one end of an erbium-doped fiber, the other end of the erbium-doped fiber is connected with one signal end of an optical fiber coupler, the other two signal ends of the optical fiber coupler are connected with two signal ends of a fiber annular structure respectively, a sensing signal output end of the wavelength division multiplexer outputs a laser signal to a light sensing face of a photoelectric detector, and a signal output end of a frequency spectrum acquisition module is connected with a frequency spectrum signal input end of a data processing module. The device and method are used for measuring birefringence changes of a single-mode fiber.

Methods and apparatus to measure visual appearance of randomly arranged birefringent fibers are disclosed. One method comprises emitting light, creating N_i polarization states of the emitted light, illuminating the birefringent fibers with the emitted light so polarized, thereby generating IR_i internal reflection components, ER_i external reflection components, and D_i diffusion components of the light in the birefringent fibers, observing the light from the illuminated birefringent fibers, creating O_i polarization states of the observed light, forming X_i images of the observed polarized light, each image comprising an information (N_i, O_i, IR_i, ER_i, D_i), wherein i=1, 2, . . . n and n≧4, measuring the intensity I_i in each pixel in the X, images, and separating the i-th internal reflection component, the i-th external reflection component, and the i-th diffusion component from the i-th image for the X_i images.

The invention discloses a small-diameter solid core polarization-maintaining photonic crystal fiber of a four-layer structure and belongs to the technical field of microstructure fibers. The concrete structure refers to that a section is round, and the fiber sequentially comprises a coating layer, a cladding and cladding air pores from outside to inside. The cladding air pores are of a four-layer symmetric structure and are arrayed in a hexagon. The centers of the cladding air pores are concave parts, two large air pores are formed in the centers in the x-axis direction to form shape birefringence of the fiber. The diameter d of each cladding air pore is 3.0-3.8 micrometers; the distance A between every two adjacent cladding air pores is 5.4-6.2 micrometers; the diameter D of each large air pore is 5.5-6.4 micrometers, the duty ratio d/Lambada is 0.55-0.65, and the range of the normalized frequency Lambada/Lambada is 3.5-4. The fiber has the advantages that gyro precision is substantially improved within a certain size limit, the temperature performance of an fiber gyro and the temperature stability of fiber birefringence are improved, and the temperature sensitivity of the fiber gyro is reduced; an fiber mode field diameter is closer to that of a common polarization-maintaining fiber, so the welding loss is smaller; the diameters of the cladding and the coating layer are smaller than those of a current fiber, so gyro miniaturization is facilitated.

In a method of measurement of the birefringence of an optical fiber, the round-trip Jones matrix R(z) for a first interval (0, z) from a measurement starting point 0 in the optical fiber for measurement to a prescribed position z, and the round-trip Jones matrix R(z+Δz) for a second interval (0, z+Δz) from the measurement starting point 0 to a position z+Δz differing from the position z, are acquired, the eigenvalues ρ₁, ρ₂ of the matrix R(z+Δz)R(z)⁻¹ are determined, and by computing the following equations (1) and (2), $\begin{array}{cc}\varphi =\frac{\arg \left(\frac{{\rho }_1}{{\rho }_2}\right)}{2}& \left(1\right)\\ \Delta n=\frac{\mathrm{\lambda \varphi }}{2\pi ·\Delta z}& \left(2\right)\end{array}$

(where φ represents the phase difference between linear polarization components due to birefringence, Δn represents birefringence, and λ represents wavelength), the birefringence in the infinitesimal interval Δz from the position z to the position z+Δz is obtained.

The invention discloses a measuring device for a polarization-maintaining fiber birefringence coefficient based on soliton self-frequency shifting, and the device comprises a femtosecond laser (1), an ultrashort pulse power and polarization state adjustment part consisting of an electronically controlled liquid crystal wave plate (2), a polarization beam splitting prism (3), a half-wave plate (4), a beam expander (5) and a fiber coupling mirror (6), a high nonlinear polarization-maintaining photonic crystal fiber (7), and a spectral coherence and detection part consisting of a fiber collimator beam expander (8), a first 50:50 splitter (9), a first mirror (10), an adjustable attenuator (11), a second mirror (12), an adjustable spatial light delay line (13) and a second 50:50 splitter (14). The measurement of the birefringence coefficient of the optical fiber can be realized by measuring the relative delay of the optical soliton in the fast axis and the slow axis by spectral coherence. The measuring device provided by the invention can measure the change of the birefringence coefficient of the optical fiber when the wavelength is continuously adjusted in a large range, and the measurement result is accurate and reliable.

Disclosed is a luminance-enhanced film, including birefringent island-in-the-sea yarns which comprise island portions and sea portions, each composed of a specific material. Accordingly, unlike conventional stack-type luminance-enhanced films, the luminance-enhanced film of the present invention comprises birefringent island-in-the-sea yarn, as a layer, in the sheet, thus considerably improving luminance without forming a plurality of layers. In addition, several hundred layers are not laminated on one film and the film can be easily fabricated at considerably reduced costs. Furthermore, the luminance-enhanced film has considerably more birefringent interfaces, as compared to films fabricated by conventional methods wherein birefringent fibers are incorporated into sheets, thus considerably improving luminance-enhancement effects and being industrially applicable.

The invention discloses a photonic crystal multimode optical fiber with completely-separated intrinsic modes. The photonic crystal multimode optical fiber comprises a birefringent fiber core which isasymmetrical in horizontal and vertical directions, an inner cladding layer formed by arranging circular air holes in a hexagonal array and an outer cladding layer formed by pure silicon dioxide. Theoptical fiber supports more than 10 intrinsic modes, and the effective refractive index difference between any two adjacent modes is greater than 1x10<-4> and even greater than 1x10<-3>, that is, allmodes are completely separated, thereby realizing the multichannel intrinsic-mode multiplexing communication of the optical fiber. According to the invention, the mode division multiplexing transmission is directly carried out on the basis of an optical fiber intrinsic mode, the supported intrinsic modes are completely separated and simplified, and the intrinsic mode stable transmission of the multichannel optical fiber can be realized without MIMO-DSP technology. The photonic crystal multi-mode optical fiber provided by the invention is completely composed of a pure silicon dioxide matrix andan air hole lattice, is based on the existing photonic crystal optical fiber manufacturing process, and is convenient for implementing the actual drawing.

The invention discloses an optical fiber winding and fixing device, which is suitable for fixing low birefringent fibers in the filed of all-fiber Sagnac optical interferometer mode optical fiber current sensing. The optical fiber winding and fixing device realizes the functions of the low birefringent fibers by means of separation of fixing and packaging and through annular spiral winding; the optical fibers are protected by grooves and supports from being influenced by external stress; and packaging of a shell shields the pollution of the outside world and guarantees the measuring precision and the reliability.