183 results about "Fiber interferometer" patented technology

An autocorrelator apparatus and method for economically measuring physical properties of an object where the measurement path is at least semi-translucent to light, such as thicknesses in multilayered optical structures, group index of refraction, and distance to a surface. The apparatus includes a non-coherent light fiber interferometer and an optional coherent light fiber interferometer in association so as to share PZT fiber modulators. Thickness and boundary extent measurements can be made, for example, of solids, liquids, liquids moving along a horizontal plane, or liquids flowing down a plane.

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.

A sensor apparatus combines an optical sensor in which acceleration, acoustic velocity, or displacement (vibration) causes a corresponding shift in the center wavelength of the sensor output, coupled to a high speed interferometric interrogator, through an unbalanced fiber interferometer. The unbalanced interferometer functions to translate optical wavelength shift into phase shift, which is easily demodulated by the interrogator.

The invention relates to a fiber laser hydrophone signal demodulating system. The laser output by a fiber laser hydrophone is transmitted to the terminal b of a 3x3 fiber coupler (3) through a single mode fiber (2) from an input terminal (1), the laser is output in three ways through the 3x3 coupler, wherein the terminal e is vacant, the laser is divided into two ways by the terminal d and the terminal f, the laser signal after interference of the two lasers is output by the terminal a and the terminal c of the 3x3 coupler, the laser signals of the terminal a and the terminal c are received by a photoelectric detector (8), and V1(t) signal and V2(t) signal output by two photoelectric detectors are transmitted to a demodulation operation processing system (10) by a signal transmission wire (9) to obtain sound pressure size. The fiber laser hydrophone demodulating system of the invention demodulates a sound pressure signal in high resolution and high stability based on a Michelson nonequilibrium fiber interferometer and eliminates influence of polarization random change on an interference demodulating signal in a common single mode fiber interferometer.

The invention discloses a fiber grating based interference type three-dimensional vector hydrophone. The vector hydrophone comprises a sealed shell used for mounting and protecting fiber grating based one-dimensional accelerometers which are inside the sealed shell and are used for measuring vibration accelerations in X, Y and Z directions, wherein the sealed shell is made of a low-density material and can meet a zero-buoyancy balance weight requirement; an elastic shell mounted outside the sealed shell and a fiber grating based fiber interferometer stuck on the elastic shell compose a sound pressure measurement channel which is used for measuring a sound pressure in water; each fiber grating based one-dimensional accelerometer has the same structure as the fiber interferometer of the sound pressure measurement channel and is respectively composed of two gratings and sensing fibers between the two gratings; the two gratings respectively reflect partial incident light signals; a hole in the sealed shell is used for leading out tail fibers of each fiber grating based one-dimensional accelerometer in the sealed shell. The fiber grating based interference type three-dimensional vector hydrophone has no discrete device, is good for size miniaturization and has obvious advantages in the aspects of reliability, multiplexing technology and the like.

The invention provides a measuring device and method for the length difference between arms of an optical fiber interferometer. The measuring device comprises a laser source module, a measured optical fiber interferometer module, a reference interferometer module and an acquisition and control module, wherein laser with wavelength varying linearly is emitted by a tunable laser to enter the measured optical fiber interferometer module and the reference interferometer module, a computer controls an analog quantity output board card to drive piezoelectric ceramic with optical fibers wound thereon, and accurate phase variation of the two modules is acquired after acquired signal demodulation; the optical path difference between two arms of the reference interferometer is changed, and meanwhile, the optical path difference variation is demodulated by the aid of a distributed feedback laser in the source module in combination with a PGC algorithm; the first step is repeated after the optical path difference between the two arms of the reference interferometer is changed; the length difference between arms of the measured optical fiber interferometer is calculated according to a measuring formula for the length difference between the arms. The piezoelectric ceramic, the distributed feedback laser and the like are introduced, the length difference between the arms of the measured optical fiber interferometer can be measured accurately with the PGC algorithm, and the measuring device has the advantages of high measurement accuracy, wide range, capability of automatic calibration and the like.

The invention discloses a polarization fading and phase fading control system of a Mach-Zehnder interferometer, which comprises a closed-loop phase fading control system consisting of a first laser (1), a polarization modulator (8), a phase controller (10), a first photodetector (3) and a digital signal processor (11), and a closed-loop polarization fading control system consisting of a second laser (2), a polarization controller (7), a phase modulator (9), a second photodetector (4) and a digital signal processor (11). The first laser (1) and the second laser (2) simultaneously output laser in an interference path through a wavelength division multiplexer (5) and a wavelength division demultiplexer (6), the comprehensive utilization of the two laser beams with different wavelengths can simultaneously eliminate polarization fading and phase fading of the Mach-Zehnder interferometer, and the wavelengths of the output laser beams of the first laser (1) and the second laser (2) are finally stabilized on an arbitrary wave crest or in the trough position of an interference light power spectrum.

The present invention provides an unbalanced polarization maintaining fiber dual-interferometer temperature strain simultaneous measurement device and method. A polarization-maintaining fiber coupler,a phase modulator, a polarization-maintaining fiber and a polarization-maintaining fiber reflector form an unbalanced polarization-maintaining fiber interferometer. A light source injects light intoa fast axis and a slow axis through a polarizer at the same time for transmission, coaxial transmission signal interference is achieved in the interferometer, interference signals are detected by a polarization beam splitting difference detection device formed by a polarization-maintaining circulator, a polarization beam splitter and a photoelectric detector, and finally, a signal collection and demodulation and record device processes the interference signals. Parameters of the fast axis and the slow axis of the polarization maintaining fiber are different to allow fast-axis signals and slow-axis signals to have different responses for the same temperature and the same strain, and an unbalanced interferometer structure is employed to construct an orthogonal response matrix and measure temperature response coefficients and strain response coefficients of two paths of interference signals to achieve simultaneous measurement of temperatures and strains. The unbalanced polarization maintaining fiber dual-interferometer temperature strain simultaneous measurement device and method solve the intersection sensitivity problem, the measurement result is accurate and stable, and the sensitivity is high.

The invention discloses a fiber laser self-mixing interferometer and a measurement method thereof and belongs to the field of displacement precision measurement. The interferometer comprises a distributed feedback semiconductor laser, a polarization-maintaining fiber coupler, an intra-line polarizer, a single mode fiber, an electrooptical modulator, an fiber Bragg grating, a gradient refractive index lens, a test piece, an photoelectric detector, a data acquisition and processing system, a fiber holder, one-dimensional guide rails, two-dimensional precision translation platform, a microscope, a base, a support and a signal generator. The fiber Bragg grating and the test piece form a reference outer cavity and a measurement outer cavity with the exit end face of the laser respectively for generating a double outer cavity self-mixing interference phenomenon; and the data acquisition and processing system adopts a self-mixing signal obtained by analysis by orthogonal demodulation technology to calculate the displacement of the test piece. The structure of the fiber interferometer is very suitable for measuring the nanometer displacement and vibration of the micro machines and MEMS devices and is more practical.

The electro-optical phase modulation coefficient measuring method for integrated electro-optical phase modulator adopts one Sagnac fiber interferometer as the measuring device, and has the measured integrated electro-optical phase modulator phase modulating the signal to the fiber interferometer with one square wave signal in the period greater than 2 times transition time of the fiber interferometer. The electro-optical phase modulation coefficient is measured through adding modulated square waves to the fiber interferometer, sampling the square wave signal the fiber interferometer outputs with a sampling circuit and calculating.

The invention discloses a demodulating device for an optical fiber Young interference optical path difference based on low coherent interference. The demodulating device comprises a wideband light source, a 3dB coupler, a sensing interferometer, a demodulating interferometer, a calibration interferometer and a line array camera, wherein a multimode optical fiber is adopted in a light path formed by the components in sequence for optical signal transmission. A demodulating method mainly comprises the steps of optical path difference sensing, optical path difference demodulating and optical path difference calibration. Compared with the prior art, the demodulating device and the method integrate modes of space scanning and time scanning to conduct low coherent interference optical path difference demodulating; no mechanical movement is available; the stability is high; compared with the time scanning, the demodulating precision is not affected by moving precision of a scanning motor; the nano-level high precision demodulating can be realized; the optical path difference calibration of an overall system is realized by adjusting the optical path difference; in addition, a nano displacement platform is adopted to control the output optical path difference effectively; an optical path difference demodulating interval of the overall system is amended; and with the adoption of an optical fiber interferometer structural form, the system adjustment is facilitated and the working stability is high.

The invention provides a Faraday rotation reflection mirror and an optical fiber interferometer. The Faraday rotation reflection mirror comprises a collimator, wherein a Faraday rotator is arranged at the emergence end of the collimator, and a reflection mirror is arranged at the emergence end of the Faraday rotator. A polarizing beam-splitting beam-combining device are arranged between the emergence end of the collimator and the Faraday rotator, the Faraday rotator is located on an emergence optical path of the polarizing beam-splitting beam-combining device, light beams pass through the Faraday rotator and then rotate for 90 degrees in a polarization state, and a focusing lens is arranged between the emergence end of the Faraday rotator and the reflection mirror. The optical fiber interferometer is provided with two interference arms, wherein each interference arm is provided with the Faraday rotation reflection mirror. The Faraday rotation reflection mirror is suitable for the optical fiber interferometer which is large in wavelength range, insensitive to temperature change and high in signal to noise ratio.

A compact and portable apparatus for measuring properties of objects utilizing a fiber optic Sagnac interferometer is enabled. The fiber optic Sagnac interferometer may be a double differential Sagnac interferometer. The interferometer core may be implemented with fiber optic components including polarization maintaining optical fiber, and by utilizing an auto-balanced avalanche photodetector. An optical switch may be incorporated to maintain relatively low average probe signal power while allowing optimal peak probe signal power. The compact and portable apparatus may be configured to measure ultrasonic vibrations, a displacement of an object surface in response to ultrasonic vibrations, and / or a vibration speed of the object surface. A wideband light source may be amplified and stabilized. A sensor head of the interferometer may incorporate a collimator adjustable to block a central portion of the projected probe beam thereby at least in part enabling in-plane and out-of-plane measurements.

The invention discloses a fiber interferometer-based area anti-intrusion method, which comprises the following steps of: arranging one or more defense areas on the boundary of a protected area by a fiber interferometer according to the size of the protected area and different requirements on information accuracy of an intrusion alarm device, forming at least one complete enclosure for the protected area, and forming a complete enclosure for the protected area by connecting the plurality of defense areas in series or in parallel; making the light emitted from a light source pass through a transmission light path to reach a light path adapter, splitting beams into a plurality of paths by the light path adapter to correspond to the plurality of defense areas respectively; forming one or moredefense lines parallel to the boundary in each defense area, wherein the plurality of defense lines are separated at intervals on depth, and each defense line consists of a path of fiber interferometer; and detecting the phase difference of optical signals transmitted in two arms of the fiber interferometer in each defense area, discriminating the characteristics of suspicious disturbance events on the boundary of the protected area, judging the position of a vibration signal by the system when the signal characteristic accords with an intrusion behavior characteristic mode and alarming by the system.

A sensor apparatus combines an optical sensor in which acceleration, acoustic velocity, or displacement (vibration) causes a corresponding shift in the center wavelength of the sensor output, coupled to a high speed interferometric interrogator, through an unbalanced fiber interferometer. The unbalanced interferometer functions to translate optical wavelength shift into phase shift, which is easily demodulated by the interrogator.

The invention discloses a new-type gas detection system based on a fiber interferometer, which belongs to the gas detection technical field, is composed of a semiconductor laser, an isolator, 1*2 coupler, a gas room, common optical fibers and a phase demodulating system, and is characterized in that a tail optical fiber of the semiconductor laser is accessed into the isolator; the output end of the isolator is connected with the common optical fiber; the other end of the common optical fiber is connected with the input end of the 1*2 coupler; the two same directional output ends of the 1*2 coupler are respectively connected with two common optical fibers; one of the common optical fiber is in series connection with the gas room; the output ends of the two common optical fibers are connected with the phase demodulating system; the optical phase difference of two beams output by two-path common optical fibers is detected by the phase demodulating system to indirectly calculate the gas refractive index, and further calculate the gas concentration. The gas detection system of the invention has the advantages of radiation resistance, corrosion resistance and electromagnetic interference resistance, and capability of safely operate in harmful environment, and being not influenced by the environment.

The invention provides a laser absorption spectrum temperature-measuring method and system based on an interference modulation principle. Employed components comprise a laser generation unit, a Mach-Zehnder optical fiber interferometer, a photoelectric detection unit and a data processing unit etc. A laser signal is generated and passes through the Mach-Zehnder interferometer, then the laser signal passes through a to-be-detected gas, and data is acquired and uploaded to the data processing unit through the photoelectric detector. Absorption light intensity data and mapping between the relative wave number and the absorption light intensity data are extracted from measurement data, a baseline and an initial value of an absorption spectrum parameter are obtained through fitting and corrected through iteration, an integral absorption rate is resolved according to the corrected absorption spectrum parameter, and a detected gas temperature is resolved through the integral absorption ratesof multiple spectral lines. According to the method and system, the structure of the optical system is simple, movable parts are avoided, the background radiation noise can be suppressed, the integraleffect is prominent, the application range is wide, the reliability is high, and the application prospect is wide.

The invention provides a vector optical fiber sensing probe based on an optical fiber interferometer and an underground vector accelerometer. A vector optical fiber sensing probe, a signal acquisitionsystem, a signal processing system and peripheral equipment are mainly included, wherein the vector optical fiber sensing probe includes three single-axis accelerometers, an outer cylinder, a sealingcover, a waterproof sealing optical cable joint and the like; two runway type optical fiber sensitive rings are pasted on two surfaces of an equal-strength cantilever beam to form a push-pull structure, sensitivity of the accelerometer can be improved, a damping liquid is filled in the probe to increase damping, and the influence of resonance on the accelerometer can be eliminated; and the threeaccelerometers are arranged in a 120-degree crossed and stacked mode to form the vector optical fiber sensing probe, a radial size of the probe can be effectively controlled, multiple measurement scenes with limitation on an equipment size can be met, and the accelerometers are particularly suitable for deep well earthquake observation.

The invention belongs to the field of fiber interferometer measurement, and specifically relates to a rotating seismic wave measurement device based on a composite interferometer. The device comprises a fiber sensing probe 10, the composite interferometer 20, and peripheral equipment. In the composite interferometer 20, an input light source 204 is connected to a port a of a second circulator 212, and a port b of the second circulator 212 is connected to a port a of a first circulator 211. A port b of the first circulator 211 is connected to a first optical grating 221, and then is connected to a second detector 202. A port c of the first circulator 211 is connected to a first detector 201. The device employs an optical path multiplexing structure to enable a Michelson interferometer and a Sagnac interferometer to share a light source and a sensing arm, and reduces the system manufacture cost.

A chemical and biological transducer is prepared by setting long period fibre grating, reflecting film on fibre section, fibre covering, fibre core and metal film on fibre covering surface on one piece of fibre to SPR transducer of fibre Michelson interferometer structure. The sensing system comprises wide band light source, fibre, chemical and biological transducer prepared as above, wide band coupler, fibre spectrograph and computer.

A compact and stable interferometer is easily built only with fusion splices. The air-holes of a microstructured fiber are intentionally collapsed in the vicinity of the splices and this broadens the propagating optical mode, allowing coupling from core to cladding modes. The transmission spectrum is sinusoidal and of single frequency, indicating predominant interference between the fundamental core mode (7) and a cladding mode (6). A regular interference spectrum can be observed from 650 nm to 1600 nm with fringe visibility reaching 80%. The fringe spacing is inversely proportional to the distance between the splices. This behaviour has a significant impact in optical sensing and communications and so the interferometer can be applied for strain sensing. The device comprises two splices (5) of a microstructured optical fiber (1), said splices (5) determining two regions in which the air-holes (4) are collapsed, separated a length (L) along which said two modes are excited.

The invention discloses a laser frequency shift detecting method and device with a dual-cavity F-P interferometer which is formed on the basis of polarization maintaining optical fibers. The device comprises a laser device, an acoustic optical modulator (AOM), an erbium-doped optical fiber amplifier (EDFA), quarter-wave plates, a collimator, a telescope, a first polarization maintaining optical fiber, a first circulator, a first narrow-band fiber bragg grating (FBG), a polarization controller (PC), an optical fiber F-P interferometer, an F-P interferometer controller, a polarization beam splitter (PBS), a first single photon counting module (SPCM), a second SPCM, a second polarization maintaining optical fiber, a second circulator, a second narrow-band FBG, a third SPCM and an acquisition card. According to the laser frequency shift detecting method and device with the dual-cavity F-P interferometer which is formed on the basis of the polarization maintaining optical fibers, a laser radar fiber integrated single-emission double-receiving light path is developed, two receiving optical fibers are spliced in the same cladding to form a dual D involution optical fiber, separation of energy detection and frequency shift detection is achieved, the signal to noise ratio of the frequency shift detection is increased, a dual-edge detection technology can be successfully achieved only by the single-channel F-P interferometer, the energy utilization ratio is high, and the method is simple.

The invention is an optic fiber safety prewarning signal identifying system of buried tube, construction or important establishment and area. Output of the optic fiber interferometer is connected with photoelectricity signal process circuit [302], character signal pick-up module [303] connected with the photoelectricity signal process circuit [302] is connected with expert system [304] then connected with the analyzing and judging system [305], the analyzing and judging system [305] is connected with local managing system [110]; output of the photoelectricity signal process circuit [302] is connected with audio processor [306] with audio buffer [307], output of the audio processor [306] is connected with local managing system [110], another output is connected with D / A[309], amplifying circuit [310] to the audio output equipment [311], at the same time the local managing system [110] possesses a output to audio equipment [311]. The invention can detect any soil oscillation signal within 3 meters effectively; judgment for property of event is accurate, stable, and reliable, without leakage.

The invention relates to a novel optical fiber interferometer and in particular to an all polarization maintaining optical fiber interferometer consisting of a 3*3 polarization maintaining optical fiber coupler. The invention consists of a 2*2 optical fiber coupler and a 3*3 optical fiber coupler. The 3*3 optical fiber coupler and the 2*2 optical fiber coupler are both the coupler consisting of the polarization maintaining optical fiber. The optical fibers are all polarization maintaining optical fibers and the polarization maintaining optical fiber is parallel to the polarization axis of the coupler; the structure can be Mach-zehnder-type or Michelson-type or Sagnac-type. As the 3*3 polarization maintaining optical fiber coupler is adopted, the interferometer in the structure of the invention has good stability and high sensitivity.

The invention belongs to the technical field of optical fiber sensing, and particularly relates to a distributed sensing system based on a Michelson-Sagnac optical fiber interferometer. According to the system, two arms of a Michelson optical fiber interferometer are used as sensing arms, and the two sensing arms are distinguished through adoption of a signal analysis algorithm; and the two interferometers detect the same time-varying disturbance at the same time, add and subtract the demodulated phases to obtain two paths of signals with time delay, and obtain the time delay related to the disturbance position through cross-correlation, so that the disturbance position information can be calculated. The maximum detection distance of the system can reach 140 km, and no blind area exists. According to the system provided by the invention, the Michelson-Sagnac hybrid optical fiber interferometer is utilized to realize distributed optical fiber sensing and positioning, the sensitivity andpositioning precision of long-distance distributed sensing are improved, the frequency response range of a distributed optical fiber sensing system is expanded, and the problem that positioning cannot be achieved when a traditional scheme is applied to buried optical cable positioning is solved.

The invention belongs to the fields of optical fiber sensing and measuring technologies, in particular to a realizing method of the pi / 2 phase bias of an optical fiber interferometer. The phase bias is generated by arranging a special optical fiber branching unit with the length and the width of 3 in an interference optical path structure; the optical intensities of output ports of the branching unit are respectively 20 percent, 40 percent and 40 percent of total output light; and the pi / 2 phase bias can be obtained by a proper optical path connection. The invention realizes the pi / 2 (positive or negative) phase bias with a pour optical path method and obtains high measuring sensitivity and linear segment measuring range. The invention is not only suitable for an interference system with same interference optical paths and opposite transmission directions, such as interference systems of Sagnac rings, single-core feedback types, and the like, and can also provide the phase bias for an M-Z optical fiber interference structure.

The invention provides a method and system for generating chaotic laser generation with high bandwidth and time delay tag concealment. In the feedback cavity of the traditional external cavity semiconductor laser, the phase modulation module and the delay fiber interferometer are added in turn. The output chaotic laser is used as the RF input of the phase modulator after photoelectric conversion and amplification, and the self-chaotic phase modulation structure is formed. The invention has the advantages that the generation of the wide-band chaotic laser, the concealment of the time delay label and the symmetrical amplitude distribution are simultaneously realized.

The present invention relates to a high-resolution surface plasmon microscope including a heterodyne interferometer (6) for splitting an excitation light beam into at least one reference beam and at least one measurement beam directed toward a coupling medium (7) to generate a surface plasmon, said heterodyne interferometer consists essentially of guide optical fibers (12, 13, 14, 15) optically connected at a first of their ends to an optical coupler (16) and each also optically connected at their second end to a light source (1), an optical coupling medium (7), an element (17) for reflecting the reference beam, and means (28) for detecting an interferometer beam, respectively.

The invention discloses a light source phase noise test method and a light source phase noise test device. The method comprises steps: firstly, a phase modulator is arranged on one way of delay fiber of a fiber interferometer, and modulation signals are loaded in the phase modulator; then, light source signals are transmitted to the fiber interferometer along the fiber, and interference signals generated by the fiber interferometer are modulated through the modulation signals; and finally, a phase generated carrier demodulation method or a working-point control method is used for demodulating the modulated interference signals, phase noise signals of the light source are acquired, and measurement on the light source phase noise is realized. through arranging the phase modulator on one way of delay fiber of the fiber interferometer, the fiber interferometer with a short-range difference is delicately used, phase modulation and interference signal acquisition are carried out synchronously, the phase noise is calculated according to an interfering modulation waveform through a demodulation algorithm, direct measurement on the light source phase noise is completed, a high-frequency detector and a high-frequency acquisition system are not needed, the system structure is greatly simplified, and the product price is reduced.