22 results about "Heterodyne detection" patented technology

An optical transmission apparatus includes an optical transmitter that generates an optical signal in an uplink direction by modulating output light of a laser that outputs light of a first frequency with a subcarrier on which transmission data is superimposed, a heterodyne detection unit that receives an optical signal in a downlink direction by heterodyne detection, a control unit that calculates a first intermediate frequency based on the frequency of the downlink signal received by the heterodyne detection and the first frequency of the laser, and controls the first frequency of the laser when there is a difference between the calculated first intermediate frequency and a reference second intermediate frequency by a threshold or more.

This invention provides a self-heterodyne detection system capable of stably and over long periods of time measuring broadband laser linewidths. [Solution] The present invention discloses a self-heterodyne detection system. The system may include a frequency comb light source that generates light, a photodetector that detects the light, an electrical spectrum analyzer connected to the photodetector that analyzes the frequency and wavelength of the light using the detection signal of the photodetector, an interferometer including an input coupler provided between the frequency comb light source and the photodetector to receive the light, a branch waveguide branched by the input coupler, and an output coupler connected to the branch waveguide, and a programmable filter provided in the branch waveguide to select the peak wavelength of the light.

This improves the degradation of the cross-correlation coefficient caused by the error between the set frequency and the actual frequency of the light source, and makes it possible to improve the degradation of the measurement accuracy of strain and temperature. [Solution] The light source unit has a frequency-stabilized wavelength-tunable laser that generates continuous light, and a first optical coupler splits the continuous light generated by the light source unit into two, sending one to a second optical coupler and the other to an optical frequency measurement unit. The optical frequency measurement unit measures the frequency of the continuous light generated by the light source unit, and the second optical coupler further splits the continuous light split by the first optical coupler into two, sending one as probe light to the optical pulse generation unit and the other as local light to a detection unit. The detection unit measures the frequency change Δf by means of coherent time domain reflectometry and a means for heterodyne detection of the Rayleigh scattered light and the local light resulting from Rayleigh scattering of pulsed light in the fiber under test. max and means for acquiring the

The invention discloses a high-wind-speed coherent laser wind-finding radar device, which comprises a seed laser, a plurality of cascaded acousto-optic frequency shift modules, a laser amplifier, a first optical switch, a laser transmitting and receiving detection module, a wind field inversion module and a wind speed identification and control unit, and is characterized in that the plurality of cascaded acousto-optic frequency shift modules realize frequency shift and beam splitting of the seed laser; the first optical switch selects the seed laser output by one acousto-optic frequency shift module as heterodyne detection seed laser; the wind field inversion module performs wind field inversion on the heterodyne beat frequency signal output by the balance detector to obtain a wind speed measurement result; the wind speed identification and control unit controls the frequency shift amount of the emitting seed laser and the frequency shift amount of the heterodyne detection seed laser, so that the difference value between the Doppler frequency shift amount caused by the wind speed and the frequency shift amount of the heterodyne detection seed laser is within the bandwidth range of the balance detector, and effective detection of the wind speed is achieved. According to the invention, the wind speed measurement range of the coherent wind lidar can be effectively improved, and the reduction of the wind speed measurement precision is not caused.

This invention discloses a bidirectional continuous-variable quantum key distribution method and system based on frequency division duplexing in a single-transceiver ring network. The method is based on a monolithically integrated silicon photonics transceiver chip. By pre-setting optical carrier frequency offsets for the forward and reverse links, it isolates the quantum signal from Rayleigh backscattering noise in the fiber in the frequency domain. The transmitting end generates a broadband waveform containing quantum signals and pilot signals, which is transmitted bidirectionally through a single optical fiber. The receiving end uses a laser source from the same chip as the local oscillator for coherent heterodyne detection. A digital signal processing module performs orthogonalization correction, phase recovery, and matched filtering to suppress noise and extract the quantum signal to generate a secure key. This invention solves the problems of inflexible networking, low fiber utilization, and severe scattering noise interference in bidirectional transmission over a single fiber caused by the separation of the transmitting and receiving ends in integrated continuous-variable quantum key distribution systems. It provides a low-cost and highly flexible solution for metropolitan quantum ring networks.

Transmitters, receivers, systems and methods for compensating for polarization drift caused by a communications channel are provided. One or more polarization reference signal(s) or sets of polarization reference signals may be transmitted in combination with a polarized communications signal. The combination may be via wavelength or time multiplexing. Polarization measurements of the one or more polarization reference signals or sets of polarization reference signals and subsequent heterodyne detections thereof may be used for compensation of the polarization drift of the combined signals which are received. The polarization compensation may be for a State of Polarization (SOP) of a polarized communications signal such as any one polarization basis. The polarization compensation may be for complete polarization channel compensation such as for three different polarization basis which are mutually unbiased.

This invention discloses a DC suppression circuit structure, a DC suppression method, and a terahertz heterodyne detection system. The DC suppression circuit structure includes a first nonlinear detection module, a second nonlinear detection module, a phase adjustment module, and a signal synthesis module. The phase adjustment module adjusts the phase of the mixing signal generated by the second nonlinear detection module. The signal synthesis module superimposes the phase-adjusted mixing signal with the mixing signal generated by the first nonlinear detection module. During the synthesis process, the self-mixing DC component is at least partially canceled out, and the intermediate frequency AC component is at least partially superimposed. This invention weakens or cancels the self-mixing DC component during the synthesis process, while allowing the intermediate frequency AC component to be superimposed and output, thereby effectively suppressing the self-mixing DC component in the output signal and improving the stability of the intermediate frequency signal.

The disclosure provides a weak measurement technology enhanced long-distance weak signal detection system and method, which can be applied to the technical field of signal detection. The system comprises: a light source providing initial signal light; a first beam splitter dividing the initial signal light into first local oscillator light, second local oscillator light and signal light; a long-distance signal transmission simulation unit obtaining intermediate signal light; a second beam splitter dividing the intermediate signal light into first intermediate signal light and second intermediate signal light; a first signal action unit modulating the first intermediate signal light into first post-selection signal light, performing heterodyne detection with the first local oscillator light, and obtaining a first heterodyne detection result; a second signal action unit modulating the second intermediate signal light into second post-selection signal light, performing heterodyne detection with the second local oscillator light, and obtaining a second heterodyne detection result, the first post-selection angle and the second post-selection angle being opposite numbers; and a signal processing unit obtaining the phase of the signal to be detected.

The invention provides a radar system for measuring wind and distance and a wind and distance measuring method, and relates to the technical field of laser radars. The system comprises a dual-band laser light source module used for outputting a first laser signal of a first wavelength and two paths of second laser signals of a second wavelength, which are emitted by the same laser and are separated; the optical antenna module is used for respectively transmitting the first laser signal and one path of second laser signal as anemometry laser, transmitting the other path of second laser signal as ranging laser, and receiving two kinds of anemometry echoes and ranging echoes; the photoelectric conversion module is used for performing heterodyne detection on the two wind measurement echoes to obtain a first wind measurement electric signal and a second wind measurement electric signal, and determining a distance measurement electric signal according to the distance measurement echoes; the identification module is used for identifying the wind speed according to the first and second wind measurement electric signals; and recognizing the clearance distance according to the ranging electric signal. According to the invention, continuity and reliability of wind measurement and distance measurement can be guaranteed, and multi-meteorological-scene monitoring requirements of wind power equipment are met.

Dual comb radiation sources and heterodyne detection for alignment metrology are described. A dual comb radiation source is configured to irradiate a metrology target with first radiation and second radiation. The first radiation and the second radiation have different repetition rates so one comb samples the repetitive pulse train from the other comb. A detector receives diffracted radiation and generates a detection signal by analyzing heterodyne beating between different corresponding portions of the first radiation and the second radiation to distinguish relevant wavelength ranges in an optical spectrum of diffracted radiation.

The invention relates to the technical field of spectrum sensing and precision measurement, in particular to a photo-thermal gas detection device and method based on double-comb enhancement, and the photo-thermal gas detection device comprises a pumping laser module, a detection laser module, a hollow-core anti-resonance optical fiber and a data acquisition module, the pump light and a first optical comb generated by the detection laser module are transmitted in the same direction in the hollow-core anti-resonance optical fiber, and the phase of the first optical comb is modulated by a photothermal effect generated after gas absorbs the pump light; and performing optical beat frequency and demodulation on the modulated first optical comb and second optical comb in a data acquisition system to obtain a photo-thermal spectrum signal. According to the invention, the wide spectrum coverage capability of the double optical combs is utilized to realize rapid parallel detection of multi-component gas, and signals are transferred to a radio frequency domain through coherent heterodyne detection, so that various noises are effectively inhibited, and the detection sensitivity, the signal-to-noise ratio and the environmental adaptability are greatly improved.

The invention belongs to the field of optical fiber sensing, relates to a distributed optical fiber sensing technology, and particularly provides a time-frequency division multiplexing Brillouin time domain reflectometer based on pulse sequence coding, which is used for improving the system performance of the Brillouin time domain reflectometer. According to the method, the optical pulse string with the time domain separated from the frequency domain is generated through the frequency shift ring, then pulse time domain coding is carried out on the optical pulses of different channels, on the premise that the number of the channels is increased, increase of the optical peak power is avoided, meanwhile, heterodyne detection of single intrinsic light has feasibility due to the reasonable frequency interval, and the detection accuracy is improved. The intrinsic optical power is maximized, so that the heterodyne detection signal-to-noise ratio is maximized; moreover, the time domain pulse codes between different channels are not mutually aliasing, so that different groups of codes can be almost simultaneously input into the optical fiber to be measured and can be decoded simultaneously, and the limitation of long measurement time of the traditional codes is broken through. And finally, the signal-to-noise ratio, the detection speed, the detection precision and other system performances of the system are effectively improved.

Described are systems and methods for generating two-dimensional spectra of liquid or gas samples. In examples, the disclosed systems and methods use frequency comb lasers for the pump and probe lasers, such as generated using fiber laser systems or electro-optic modulated laser systems, and employ enhancement cavities for the pump and probe lasers to increase laser intensity for interaction with the liquid or gaseous sample for generation of signals for use in generating two-dimensional spectra. In examples, heterodyne detection of generated signals using a detection laser is also employed.

The application belongs to the technical field of laser radar, and discloses a low, slow and small single-photon radar based on a detection array, which comprises a laser, a beam splitter, an acousto-optic modulator, an optical amplification module, a transceiving light path, a rotary table, a fiber array, a heterodyne detection array module and a data acquisition and processing module; the data acquisition and processing module extracts the body vibration characteristic parameters of the unmanned aerial vehicle through a vibration characteristic extraction algorithm, and identifies the unmanned aerial vehicle target by using a target identification algorithm. Compared with the prior art, the application generates high-coherence laser, realizes laser projection and vibration signal reception in a large range of space through the fiber array, and then combines the heterodyne detection array to suppress environmental noise and extract the body vibration characteristics of the unmanned aerial vehicle, so that the precise detection and identification of the unmanned aerial vehicle are finally completed through a signal processing and identification module, and the application has the advantages of a large field of view, strong anti-interference capability, high vibration signal extraction precision and the like, and can realize the detection of the low, slow and small unmanned aerial vehicle at a long distance, high sensitivity and low misjudgment rate.

The invention discloses a microscopic system and method based on spontaneous Brillouin scattering. A microscopic system based on spontaneous Brillouin scattering may include a microscopic assembly and a detection assembly. The microscopic assembly is configured to receive first laser, and the first laser is pulse laser; and guiding the first laser to the sample to be tested to generate spontaneous Brillouin scattering light. The detection assembly is configured to: receive the spontaneous Brillouin scattering light and the second laser; heterodyne detection is carried out on the spontaneous Brillouin scattered light and the second laser to generate a detection result, and the detection result is processed to carry out Brillouin microscopic detection on the to-be-detected sample.

This invention relates to an electromagnetic field scanning system for diamond NV centers based on heterodyne detection, belonging to the field of microwave quantum detection technology. It includes a laser pumping module, a fluorescence collection module, a microwave pumping module, a magnetic field control module, and a scanning detection module. The laser pumping module generates a laser to excite the diamond NV centers to emit fluorescence signals. The microwave pumping module generates an injection microwave signal and a reference microwave signal with similar frequencies. The injection microwave signal is injected into the microwave radiation device under test to generate the microwave signal to be measured. The reference microwave signal and the microwave signal to be measured generate a heterodyne mixing signal. The magnetic field control module applies a static magnetic field to the diamond, enabling the diamond NV centers to resonate with the microwave signal to be measured and emit fluorescence response signals. The fluorescence collection module collects the fluorescence signal and obtains the spectrum, which is sent to the control unit. The control unit calculates the microwave signal to be measured based on the spectrum information. This invention solves the problem of the lack of a system solution for applying heterodyne detection to the detection of diamond NV centers in the prior art.

The invention discloses a full duplex underwater wireless coherent optical communication system and method, and the system comprises a terminal A and a terminal B. The terminal A comprises a first laser, a first beam splitter, a first modulator, a first light beam adjusting unit, a first transmitting aperture, a first receiving aperture, and a first coherent receiving module. Laser emitted by the first laser device is divided into two laser beams through the first beam splitter, one laser beam is modulated by the first modulator, then information is loaded, the laser beam is emitted and output from the first emission aperture through the first light beam adjusting unit, a digital signal to be transmitted is connected to the input end of the first modulator, and the other laser beam serves as coherently received local oscillation light. And the optical signals are input into the first coherent receiving module, the first coherent receiving module receives the optical signals, and signal demodulation is completed through coherent heterodyne detection. The terminal B and the terminal A are of a symmetrical structure and are the same in composition and function. The invention has the advantages of strong ambient light inhibition capability, simple and compact structure and the like.

The invention discloses endoscopic detection equipment and Brillouin microscopic detection equipment used for the endoscopic detection equipment. A Brillouin microscopic detection device for an endoscopic detection device comprises a first laser module, a second laser module, an optical fiber and a detection assembly. The first laser module generates pump light and the second laser module generates cost-oscillating light. The optical fiber transmits the pump light to irradiate the portion to be detected to generate spontaneous Brillouin scattering light. The optical fiber transmits the spontaneous Brillouin scattering light to the detection module. The detection module receives the spontaneous Brillouin scattered light and the local oscillator light to perform heterodyne detection thereon to generate a detection result, which is processed to perform Brillouin microscopic detection.

The application discloses a reconfigurable large-bandwidth frequency hopping system and method based on an optical frequency comb, and belongs to the technical field of communication. The system comprises a laser, a first microwave source, a second microwave source, a third microwave source, a first coupler, a second coupler, a first intensity modulator, a second intensity modulator, a first optical filter, a second optical filter, a third optical filter, a fourth optical filter, a high-speed optical switch, a double-parallel Mach-Zehnder intensity modulator, a controller, a 90-degree mixer, a photodetector and a doped fiber amplifier. The system can generate high-quality optical frequency combs by cascading intensity modulators, can provide rich spectrum resources for frequency hopping, can realize high-speed switching by combining a commercial high-speed optical switch, and can realize reconfigurable large-bandwidth frequency hopping signal generation by carrier-suppressed single sideband modulation of a double-parallel Mach-Zehnder modulator and heterodyne detection.

Systems and methods for measuring electron density within a plasma are disclosed herein. An example system includes a laser source configured to emit a light beam, a first second harmonic generation (SHG) component configured to receive the light beam and generate a first harmonic light beam with a first polarization, and a plasma chamber containing a plasma, which the light beam and the first harmonic light beam pass through. The example system further includes a second SHG component configured to receive the light beam after passing through the plasma and generate a second harmonic light beam that has a second polarization. The example system further includes a heterodyne detection component configured to detect an interference pattern of the first harmonic light beam combined with the second harmonic light beam, and data processing circuitry configured to determine an electron density of the plasma based on the interference pattern.

The embodiment of the application provides a kind of high sensitivity acoustic wave sensing system and method, belong to optical fiber sensing technical field.The system includes: narrow line width laser output continuous coherent light, is divided into two ways by beam splitter;Reference arm is set in the acoustooptic modulator operating in continuous wave mode, and the light signal is shifted with fixed frequency, and the local oscillator light is output;Sensing arm is set in the suspended micro-nano fiber sensing probe, and the external acoustic wave signal is modulated as the phase change of light;Two-way light is combined by second optical coupler, and is converted into beat frequency electric signal by photoelectric detector;IQ demodulation module carries out quadrature demodulation to beat frequency electric signal, and extracts the phase change caused by acoustic wave signal.The application adopts suspended micro-nano fiber structure, eliminates mechanical resonance and damping;Combined with AOM continuous light heterodyne detection and IQ demodulation, acoustic wave signal is shifted to high frequency carrier, and environmental drift is directly filtered out by digital high-pass filter, without PZT feedback, realize never lose lock wideband high sensitivity detection.

The invention discloses a 90-degree spatial light mixer, which comprises a local oscillation light processing unit and a signal light processing unit which are arranged in parallel, an energy spectroscope is arranged on the rear side of the local oscillation light processing unit, a light splitting film is plated on one side of the energy spectroscope, and an antireflection film is plated on the other side of the energy spectroscope; a second rhombic prism group is arranged right behind the energy spectroscope; a first reflecting mirror is arranged right above the energy spectroscope; an optical device for realizing coherent mixing of signal light (S) and local oscillation light (LO) by using a polarization optical element and a special optical coating technology is characterized in that through an integrated design of polarization beam splitting, phase modulation and beam combination, complex light splitting, phase shifting and multi-path detection functions in a traditional heterodyne detection or coherent communication system are changed into a multi-path optical device for realizing coherent mixing of signal light (S) and local oscillation light (LO); the spatial optical mixer is integrated in a compact module with a simple structure and a small number of elements, and the technical problems of heavy device weight, incompact structure and high assembly difficulty caused by a large number of discrete devices in the spatial optical mixer in the prior art are solved.