37results about How to "Suppress intensity noise" patented technology

The invention belongs to the technical field of all-fiber current transformers, and particularly relates to a high-precision high-reliability and all-fiber current transformer. A redundancy design method adopting active optical devices is applied so that output optical power of light source units is enabled to be more stable and stability of light source average wavelength is enhanced. A depolarization head is additionally arranged in an optical path system so that stability and measurement precision of the optical path system can be enhanced. Two beams of light are converted into electric signals to be transmitted to a signal processing unit by utilizing correlation of output light of the two output ends of a second single-mode coupler through a digital signal processing unit, and suppression of light source intensity noise is realized by utilizing a digital circuit subtraction method so that signal-to-noise ratio is enhanced and measurement precision of the system is enhanced. A low birefringence optical fiber Verdet constant and a transformation ratio error generated by change of wave plate phase delay along with temperature are enabled to be mutually compensated via an all-fiber current transformer transformation ratio temperature error automatic compensation technology so that full-temperature measurement precision of the system is enhanced.

The invention discloses a digital closed loop optical fiber gyroscope with a double-interferometer system. The digital closed loop optical fiber gyroscope comprises a light source driver, a light source, a third beam splitter, a first angular speed sensing module, a second angular speed sensing module, an optical fiber ring and a logic circuit, wherein light emitted by the light source is divided into two beams of incident light after passing through the third beam splitter, and the two beams of incident light respectively enter the first angular speed sensing module and the second angular speed sensing module; the two modules uses the same optical fiber ring, so that two different interferometers are formed in the polarization maintaining optical fiber ring and respectively output signals; the logic circuit receives the signals and performs differential calculation to obtain speed information sensed by the interferometers. The digital closed loop optical fiber gyroscope disclosed by the invention controls a polarization state through a polarization beam splitting/combing device through the same polarization maintaining optical fiber ring, so that the two interferometers in different polarization states are formed in the optical fiber ring; the two polarization states are separated, so that the light-based double-polarization double-interferometer system is implemented, and the precision of the digital closed loop optical fiber gyroscope can be obviously improved, and the intensity noise of the light source is suppressed.

The invention relates to a method and device for improving the signal to noise ratio of a laser micro-vibration sensing system. The light emitted by a laser is divided into two light beams by an optical fiber coupler, the weak light beam is directly converted into an electrical signal through a third photoelectric detector, and the strong light beam is emitted through an optical fiber collimator to serve as a light source of an interferometer. The light emitted by the optical fiber collimator is divided into reflected light and transmission light through a first polarizing beam splitting device, the reflected light serves as reference light, and the transmission light serves as signal light. The reference light and the signal light are input to a first photoelectric detector and a second photoelectric detector respectively through a second wave plate and a second polarizing beam splitting device. The output of the second photoelectric detector is subtracted from the output of the first photoelectric detector, then the difference is divided by the output of the third photoelectric detector, two orthogonal signals are obtained by frequency mixing and filtering on the result, A/D conversion is carried out on the two orthogonal signals, and a carrier wave demodulation algorithm is generated through a phase position so that demodulation can be achieved. The signal to noise ratio can be improved by 5dB to 10dB, and the measurement capability of weak vibration signals is enhanced.

The invention provides a continuously tunable single-frequency Ti sapphire laser device. The continuously tunable single-frequency Ti sapphire laser device comprises a pump source (3), a Ti sapphire crystal (2), a laser resonant cavity, an isolator, a double-refraction filter (4), an etalon (5) and piezoelectric ceramic (14), wherein a nonlinear crystal (1) is inserted between a third flat concave mirror (11) and a fourth flat concave mirror (12) forming the laser resonant cavity, the nonlinear crystal (1) is an optical crystal machined to be provided with two unparallel light through surfaces or an optical crystal placed in a light path at a Brewster angle; moreover, the nonlinear crystal (1) is used for realizing generation of second harmonics of the base-frequency light of the laser device in a mode of critical phase matching or noncritical phase matching. According to the continuously tunable single-frequency Ti sapphire laser device provided by the invention, the nonlinear loss stressed by the main oscillation mode of the base-frequency light is one half of a non-oscillation mode, thus the oscillation starting of the non-oscillation mode of the base-frequency light is effectively suppressed, and the laser device realizes continuously tunable property for the frequency in a valid gain bandwidth. The laser device is compact in structure and convenient to operate.

A 2 [mu]m band low-noise narrow-linewidth single-frequency fiber laser is provided, which comprises a single-frequency laser resonant short cavity, a resonant cavity temperature control module, a wavelength division multiplexer, a co-band pumping source, a pumping source intensity noise suppression module and an optical isolator. The invention uses a laser with small difference between the workingwavelength and the laser signal wavelength as a co-band pumping source, uses an intensity noise suppression module to suppress the noise of the pumping source, and then uses a low-noise pumping source to pump the 2 [mu]m single-frequency laser resonant short cavity. Finally, single frequency fiber laser with low noise, narrow linewidth, and the working band of 2 [mu]m is output from the cavity. The laser provided by the invention has the advantages of all-optical fiber structure, excellent noise performance, extremely narrow laser linewidth, high conversion efficiency, simple structure, etc.,and can be used for atmospheric measurement, laser radar, biomedical, and realizing laser output in 3-5 [mu]m band as a pump source of an optical parametric oscillator (OPO) and the like.

The invention discloses a broadband single-frequency fiber laser intensity noise suppression device for achieving a nearly schottky noise limit. The broadband single-frequency fiber laser intensity noise suppression device comprises a single-frequency fiber laser resonator, a wavelength division multiplexer, a single-mode semiconductor pump light source, an optical fiber isolator, a polarization controller, a laser saturated amplification device, an optical fiber filter module, an optical fiber coupler, a photoelectric detector and a feedback control system. According to the broadband single-frequency fiber laser intensity noise suppression device disclosed by the invention, the broadband intensity noise of output laser can be reduced through the laser saturated amplification device; feedback control is carried out on the laser saturated amplification device, so that the intensity noise of the output laser can be further reduced; the frequency range of intensity noise suppression can be further expanded; and finally, the effects of keeping the intensity noise of a single-frequency laser within a broadband and simultaneously reducing the intensity noise close to schottky noise limit are achieved. The broadband single-frequency fiber laser intensity noise suppression device for achieving the nearly schottky noise limit has a broad application prospect and great application value in the fields of ultra-high precision and ultra-long distance laser ranging, optical fiber sensing, atomic and molecular spectroscopy and the like.

The invention relates to a high-precision fiber-optic gyroscope optical path structure with a function of suppressing relative strength noise. The high-precision fiber-optic gyroscope optical path structure comprises an ASE (Amplified Spontaneous Emission) light source, a detector, a coupler, a Y waveguide integrated optical device and a polarization-maintaining optical fiber ring. The high-precision fiber-optic gyroscope optical path structure is mainly and technically characterized in that a semiconductor optical amplifier is arranged between the ASE light source and the coupler; the ASE light source passes through the semiconductor optical amplifier, the coupler and the Y waveguide integrated optical device and is then divided into two paths which enter the polarization-maintaining optical fiber ring; interference light from the polarization-maintaining optical fiber ring passes through the coupler and then enters the detector. According to the high-precision fiber-optic gyroscope optical path structure disclosed by the invention, the semiconductor optical amplifier (SOA) working in a saturation region is added in a fiber-optic gyroscope optical path; and noises are suppressed by using optical characteristics of the SOA, so that relative strength noise of the light source is effectively inhibited and the precision of a fiber-optic gyroscope is improved; meanwhile, the SOA isadopted and an extra noise suppression channel and a feedback loop do not need to be added, so that design difficulty of a demodulation circuit and debugging difficulty of the gyroscope are preventedfrom being increased; a realization method of the high-precision fiber-optic gyroscope optical path structure is simple and effective.

The invention discloses a wide frequency band intensity noise inhibition device and inhibition method of an optical fiber laser. The device is composed of an optical fiber laser, a reflection type semiconductor optical amplifier, a semiconductor optical amplifier controller, an optical fiber conical lens, a semiconductor laser, a driving current source, a photoelectric detector and a frequency spectrum analyzer. Through the combination of the gain saturation effect of the large bandwidth of the semiconductor optical amplifier and the frequency stabilization effect of a laser resonant cavity, the intensity noise of the optical fiber laser can be inhibited in large amplitude in the wide frequency band range while maintaining the narrow line-width of the optical fiber laser.

The invention discloses a data processing method for a THz-grade large-bandwidth laser synthetic aperture radar imaging system, which is composed of a linear tuning semiconductor, a 99:1 optical fiber coupler, a 90:10 optical fiber coupler, an emission collimating lens, a polarized beam splitter, a lambda/4 wave plate, a target displacement platform, a receiving collimating mirror, four 50:50 optical fiber couplers, two balancing detectors, a reference time delay optical fiber, a molecular wavelength reference device, an optical power meter, a data acquisition module and a data processing program module. The laser synthetic aperture radar imaging system disclosed by the invention is based on a large-range linear tuning laser pulse signal; and a target two-dimensional image is calculated according to the homodyne coherent detection technology, the balance detection technology, the synthetic aperture technology and the final special data processing procedure. The system has the advantages of short laser signal wavelength, large bandwidth, high imaging resolution, all-weather characteristic, high stability, simple structure, high detection sensitivity and long acting distance, and most of the system is based on the optical fiber device.

The invention discloses an optical fiber communication transmission system and method applied to multi-wavelength pumping high-order bidirectional Raman amplification, which are applied to an ultra-long span optical fiber communication system and a common optical fiber communication system, can reduce one pump light in a multi-wavelength pumped bidirectional high-order Raman amplifier, and solve the problems of high relative intensity noise and low gain efficiency in a current multi-wavelength pumped high-order Raman amplification process and meanwhile reduce the system cost. A pump light closest to a signal light wavelength is reduced on a forward high-order Raman amplifier; and a reflection-type fiber grating filter is inserted respectively at an output end of the forward high-order Raman amplifier and an input end of a backward high-order Raman amplifier, and the central wavelength of the fiber grating is the wavelength of the pump light that has been reduced. The method of the invention can reduce the number of pump lights of the high-order Raman amplifier and reduce cost, and at the same time, reduce the relative intensity noise of the high-order Raman amplifier, greatly improve the backward gain and forward gain efficiency of the high-order Raman amplifier, and extend the transmission distance of a bidirectional high-order Raman fiber communication system.

The invention discloses a 1.0-micron ultralow-noise single-frequency optical fiber laser. The laser comprises a high-reflectivity optical fiber Bragg grating, a high-gain optical fiber, a low-reflectivity optical fiber Bragg grating, a TEC thermoelectric refrigerator, a pump laser, an optical wavelength division multiplexer, an optical filter, an optical isolator, a medium-frequency-band intensitynoise suppression module and a low-frequency-band intensity noise suppression module. The high-gain optical fiber serves as a gain medium of laser light; laser oscillation is formed under the pumpingof pump light; output laser light is filtered by the optical filter to amplify spontaneous radiation light, so that stable and single longitudinal mode laser output is realized; the laser light enters the medium-frequency-band intensity noise suppression module; the intensity noise near a laser relaxation oscillation peak is effectively suppressed by a semiconductor optical amplifier, and laser power amplification is carried out; then the low-frequency-band intensity noise suppression module is used for suppressing the low-frequency-band intensity noise; and finally high-power, ultralow-noise, narrow-line-width and single-frequency optical fiber laser output is realized.

The invention discloses an integrated three-phase all-fiber optical current transformer and solves a technical problem of how to improve all-temperature measurement precision and integration reliability. The integrated three-phase all-fiber optical current transformer comprises a light path system unit and a digital signal processing unit, wherein a light source, a polarization-maintaining coupler, a polarizer, a straight waveguide, a delay fiber and a sensing ring of the light path system unit are sequentially connected, the digital signal processing unit is provided with a light source intensity noise inhibition unit, a signal processing unit, a phase demodulator and a phase driving circuit which are sequentially connected, and the phase driving circuit is connected with the straight waveguide. Compared with the prior art, intensity noise is inhibited through a dual-polarized light path, all-temperature measurement precision and small current measurement precision of the current transformer are improved, a time division multiplexing circuit is employed by the signal processing unit, optical devices and the sensing ring of the light path system are simplified, phase time delay of the sensing ring is precisely controlled, automatic light path compensation is realized, curing manufacturing of the sensing ring is realized, and all-temperature measurement precision and reliability of the all-fiber optical current transformer are improved.

The invention discloses a method and device for restraining light source intensity noise through electro-optical modulator proportional compensation. A light beam splitter is used for splitting lightsource output in proportion; a pair of high-power and low-power light beams is formed; the high-power light beam is sampled; light intensity fluctuation information is obtained, a modulation signal isloaded to an electro-optical modulator through a signal processing module to modulate light intensity fluctuation of the low-power light beam so as to generate a light signal which is the same as thehigh-power light beam in intensity and has a phase difference of 180 degrees, and finally the light signal and the high-power light beam are combined and output, so that the effect of restraining output light intensity fluctuation is achieved. The defect of low power threshold of the electro-optical modulator is overcome, the intensity noise suppression of the high-power laser is realized, the cost is low, and the application and implementation are easy.

The invention relates to a method for optically detecting surfaces wherein strip patterns are projected onto the surface, images are captured, and the three-dimensional contour thereof is determined from the reproduction of the strip pattern on the surface of the object. The aim of the invention is to prevent reflections that interfere with the images and as a result, the surface of the object is covered with a layer of a fluorescent material, is then radiated with ultraviolet radiation, and the radiation emitted by the fluorescent material in the visible light is detected.

The invention discloses a high-performance pulse laser pumping rubidium clock optical system. An optical isolator is arranged in the light emitting direction of a laser diode; a first reflector is arranged in the light emitting direction of the optical isolator; one part of the light beam passing through the first reflector enters a frequency stabilization module through a first beam splitter, andthe other part enters a second beam splitter; one part of the light beam split by the second beam splitter enters a photoelectric detector, and the other part enters a second reflector; light reflected by the light beam through the second reflector enters an acoustic optical modulator, the acoustic optical modulator adopts a semiconductor refrigerator for temperature control, light emitted by theacoustic optical modulator enters a diaphragm, light emitted by the diaphragm enters a third reflector, and the light beam enters a beam expander after being reflected by the third reflector. A largenumber of temperature-sensitive components such as a phase delay sheet and a polarization beam splitter are effectively prevented from being used, and a Doppler background removing frequency stabilization scheme is adopted, so that the system has the advantages of compact volume, high reliability and low frequency and intensity noise.