182 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.

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 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 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.

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 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.

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 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.