220 results about "Atomic clock" patented technology

The invention relates to the technical field of atomic clock control, and discloses a punctuality type atomic clock control method based on a microwave frequency band. The method comprises the following steps: firstly, acquiring microwave frequency band signal data and atomic state data, and constructing a time calculation model in combination with historical operation data to output a theoretical time value; performing multi-dimensional difference analysis on the theoretical time value and the actual measurement time value to generate a time difference coefficient matrix; inputting the matrix into a spatial propagation analysis network, and combining atomic clock component parameters and environmental parameters to generate a time anomaly probability distribution diagram; and finally, configuring microwave control parameters according to the distribution diagram, including starting a high-frequency monitoring mode for a high-probability abnormal region and applying a disturbance test to adjacent frequency bands. According to the method, through multi-dimensional data modeling, difference analysis and dynamic parameter configuration, the accuracy and adaptability of atomic clock control are improved, and the operation stability of the atomic clock in a complex environment can be enhanced.

The invention relates to a method and device for determining a lunar gravity field by using an inter-satellite frequency signal time-frequency link, and the method comprises the steps: connecting an earth observation station, a static satellite and a lunar polar orbit satellite which are provided with an atomic clock through a satellite carrying a clock system based on a generalized relativistic theory, and carrying out the time-frequency transmission through a satellite time-frequency transmission method, the gravity potential difference between the earth and the satellite and the gravity potential difference between the satellite and the moon polar orbit satellite are measured through a gravity frequency shift method, the gravity potential data of the moon polar orbit satellite are obtained through an inter-satellite time-frequency link according to the earth gravity potential data, and then the moon gravity field is determined through a physical geodetic measurement method. Therefore, the problems that the prior art is difficult to implement on the surface of the moon and the gravity potential of the moon and the earth cannot be connected are solved.

The application discloses a double-resonance atomic clock ultra-miniature substrate integrated waveguide chamber, comprising: a substrate integrated waveguide annular gap cavity, the substrate integrated waveguide annular gap cavity is formed by longitudinal stacking of a plurality of longitudinal slit substrate integrated waveguides, the longitudinal slit substrate integrated waveguide comprises a metalized through hole and a metal microstrip line, and the longitudinal slit substrate integrated waveguide is provided with a longitudinal slit; a MEMS atomic gas chamber; a mode matching excitation structure for exciting a microwave magnetic field to the substrate integrated waveguide annular gap cavity; and an electromagnetic shielding and heating assembly arranged outside the substrate integrated waveguide annular gap cavity. The application can effectively solve the key problem that the resonant performance of a printed miniature annular gap cavity is extremely sensitive to the size change of subwavelength structure parameters, increase the processing tolerance of the ultra-miniature integrated chamber, reduce the processing difficulty and manufacturing cost of high-precision PCB through holes, and improve product yield.

The invention relates to an atomic clock frequency anomaly detection method, and belongs to the technical field of deep learning and the field of atomic clock anomaly detection. The method comprises the following steps: acquiring a frequency sequence set with a label generated by an atomic clock in a normal frequency sequence injection known abnormal mode; performing supervised training on the anomaly detection model by using the frequency sequence set; in the anomaly detection model, performing feature fusion, nonlinear transformation and classification on a first path of features extracted by performing multilayer decomposition on an input frequency sequence by adopting discrete wavelet transform and a second path of features extracted by adopting a CNN-Transformer network on the input frequency sequence, and then detecting an abnormal frequency sequence; and performing frequency anomaly detection on the atomic clock frequency sequence acquired in real time by using the trained anomaly detection model. According to the invention, high-precision detection of frequency anomalies with different characteristics is realized, the detection range is expanded, and the detection precision is improved.

The invention provides a comprehensive photoelectric platform method and system for unmanned aerial vehicle detection, electronic equipment and a storage medium, and relates to the technical field of unmanned aerial vehicle detection and localization. Synchronously triggering a photoelectric platform to capture a suspicious airspace high-definition video stream and establishing a space-time corresponding database of the two; synchronizing each radio frequency receiving node by taking a high-precision atomic clock as a time reference, and processing multiple paths of signal data to obtain a time-aligned basic signal; basic signal radio frequency features are extracted and associated with equipment identification, a mapping relation between the basic signal radio frequency features and remote controller models is established, and a hardware feature library is constructed; and finally, in combination with the library identification result, the signal time difference and the optical data, correcting a multipath error by using particle filtering, predicting and updating the position of an operator, and realizing comprehensive detection and positioning of the unmanned aerial vehicle after iterative convergence, thereby realizing comprehensive detection and positioning of the unmanned aerial vehicle in combination with radio frequency detection and optical observation.

The present invention belongs to the field of marine underwater positioning, navigation and timing. Disclosed are an underwater navigation and communication integrated position service system and method. The system comprises a buoy base station, a submerged buoy base station, a seabed base station and a shore-based operation and control unit, and the system utilizes a three-dimensional base station network observation mode combining the buoy base station, the submerged buoy base station and the seabed base station. The position service system and method in the present invention have the capabilities of underwater acoustic navigation and communication, satellite positioning and communication, atomic clock timekeeping, hydrological measurement and responding to instructions of a shore-based operation and control unit, have the functions of autonomous, real-time and online base station position and clock calibration and sound velocity field correction, have the functions of base station position and clock calibration, and sound velocity field correction and control based on the shore-based operation and control unit, and can expand the range and functions of underwater position services, and provide accurate positioning, navigation and timing services for water-surface / underwater users.

The invention discloses a power line fog penetration monitoring method, system and device based on polarization-infrared multi-mode fusion and a medium. An atomic clock is tamed to trigger infrared pulse and polarization exposure, and pixel offset caused by jitter of an unmanned aerial vehicle is compensated through an image motion analysis method; constructing a polarization physical model, and establishing a relationship between the fogdrop particle size and the polarization degree; performing multi-modal feature fusion, constructing a double-branch deep learning network, and performing output judgment on the image according to a dynamic fusion strategy; and optimizing conductor features and insulator features in the power line through a special convolution kernel, and accurately extracting target features.

The invention belongs to the technical field of satellite communication, navigation and precision measurement, and discloses a constant-temperature crystal oscillator automatic taming and calibration method and system based on GPS pulse per second, which can accurately tame and calibrate internal clocks such as a rubidium atomic clock and a 10MHz constant-temperature crystal oscillator through a GPS pulse per second signal, and adopts a novel clock synchronization algorithm to realize the automatic taming and calibration of the constant-temperature crystal oscillator. Through accurate frequency calibration and phase synchronization, high-stability and high-precision second pulse signals and 10MHz frequency clock signals are output.

The invention discloses a femtosecond optical comb large-size precision absolute distance measurement system in a complex environment. Comprising a source module, a beam splitter, a third dichroic mirror, a fundamental frequency femtosecond optical comb reference detector, a frequency doubling femtosecond optical comb reference detector, a fourth dichroic mirror, a frequency doubling femtosecond optical comb measurement detector, a fundamental frequency femtosecond optical comb measurement detector, a phase discriminator, a ranging zero point mirror and a corner reflector. The source module comprises an atomic clock, a femtosecond optical comb, an optical fiber beam splitter, a signal generator, an electro-optical modulator, a lens, a frequency multiplication module, a first collimation beam expander, a second collimation beam expander, a first dichroic mirror and a second dichroic mirror. According to the scheme, the defects that in the prior art, the measurement range is insufficient, complex industrial sites are difficult to adapt, and the real-time performance is poor are overcome, and a new way is provided for breaking through the technical bottleneck of large-range, high-precision, dead-zone-free, rapid and real-time measurement in a complex environment; and a technical support is provided for engineering application of a femtosecond optical comb precision distance measurement technology and development of a subsequent measurement prototype.

The invention discloses a distributed radar time-frequency synchronization and transmit-receive coherent method and system, and belongs to the technical field of radars. The method comprises the following steps: connecting each transmitting station and each receiving station of the distributed radar with a synchronization device, wherein the synchronization device comprises timing system equipment, an atomic clock and wireless communication equipment; the distributed radar receives working parameters issued by the wireless communication center controller to the distributed radar by using the wireless communication equipment; according to the working parameters, the transmitting station starts to transmit a radar signal after receiving a trigger synchronization signal of the timing system equipment, and the receiving station starts to collect an echo signal based on a local oscillator signal after receiving the trigger synchronization signal of the timing system equipment; the radar signal and the local oscillator signal are both generated based on the connected atomic clock as a reference clock. According to the invention, time-frequency synchronization and transmit-receive coherence of the distributed radar can be realized by using the synchronization device, limitation of space wired connection is avoided, and the construction cost of the distributed radar is reduced.

The invention provides a high-precision time-keeping low-phase-noise time synchronization device, and belongs to the technical field of time synchronization. The system comprises a power supply module, a satellite time service module, a frequency source module, a clock synchronization module, a frequency shunt module, a communication interface module and a Bluetooth module. Wherein the power supply module adopts a dual-power-supply redundant circuit design, and after one power supply breaks down, the other power supply can be automatically switched; the satellite time service module adopts a single Beidou signal baseband signal processing algorithm and an anti-cheating design, so that the safety of equipment is improved; the frequency source module comprises a constant-temperature crystal oscillator and a rubidium atomic clock, and high-time-keeping and low-phase-noise signal output is achieved in the mode that the crystal oscillator and the atomic clock are complementary. According to the invention, the problem that the conventional time synchronization equipment cannot have high time keeping precision and low phase noise of output signals at the same time is solved, a high-steady-state low-phase-noise 10MHz frequency standard signal, a 1PPS time service signal and an NTP network time service signal can be provided, and time service is provided for various terminals or servers.

The invention discloses a high-precision time synchronization method and system based on distributed airborne measurement, and the method comprises the following steps: employing a high-precision atomic clock as a system clock, transmitting the precise clock to slave devices at all levels, achieving the homology and the same frequency of the clock, and guaranteeing the time consistency of the timekeeping process of a local clock; clock and time service data are transmitted through high-speed optical fibers, independent optical fiber communication links are distributed, and the same clock and time service data receiving and transmitting module is used, so that the data transmission and receiving processing time of all levels of equipment in the time service process is fixed, and the fixed time delay can be measured through a specific means. And high-precision time synchronization is finally realized by compensating the fixed time delay. Based on the distributed design of airborne measurement, the index requirements of small design size and high synchronization precision of the master device and the slave device are met, the synchronization precision can reach 10ns, the slave device can be flexibly expanded, and the method is suitable for various distributed measurement systems or measurement and control systems with high requirements on time synchronization precision.

The invention discloses a time synchronization method, a time synchronization system and a storage medium, and the method comprises the steps: receiving and fusing multi-source time signals at the same time, and obtaining a local time reference signal; calculating the frequency compensation amount of a local clock source in real time based on an LSTM model trained by using a local time reference signal; detecting whether the time signal is available, and determining to switch an atomic clock taming mode or a timekeeping mode based on a detection result; inserting a timestamp with femtosecond precision for the initial data message through the PIC to obtain a target data message; and sending the time synchronization information and the target data message to a 6G network node through a precision time protocol of the FPGA chip. According to the invention, on the basis that the satellite signal is taken as a time reference, two conditions that the satellite signal is available and unavailable are considered, and a local clock source and photon time service are adjusted in combination with a multi-source satellite signal fusion result, so that the time synchronization precision is improved, and the 6G network requirement is met.

The invention relates to a Beidou pseudolite signal simulation generation method, which comprises the following steps of: setting a pseudolite private frequency band so as to avoid same-frequency interference with a real Beidou satellite signal; high-precision clock synchronization is carried out to ensure that the pseudolite and the Beidou atomic clock are highly synchronized; and the transmitting power is dynamically adjusted to adjust the transmitting power in real time, the near-far effect is inhibited, and the signal coverage range is optimized. Through collaborative optimization of frequency spectrum planning, clock synchronization and power regulation, the positioning availability is improved and the elevation precision is optimized in a complex environment, and a complete enhanced positioning solution is provided for a Beidou system in scenes such as automatic driving, tunnel navigation, mountains and canyons.

The invention discloses a cable saddle state detection method, which belongs to the technical field of detection, and constructs a'monitoring-analysis-decision 'closed-loop intelligent detection system through the combination of multi-parameter fusion, coupling characteristic analysis, dynamic threshold and a multi-parameter group-based joint judgment mechanism. The one-sidedness defect of traditional single parameter monitoring is fundamentally overcome, on the multi-parameter fusion level, time reference unification is achieved through an atomic clock, a three-dimensional geometric model is constructed through homogeneous coordinate transformation, state parameters are unified into space-time reference, and multi-source data isomerism is eliminated; in coupling analysis, the Pearson's correlation coefficient and the mutual information algorithm realize screening of strong correlation parameter groups through double criteria, a design standard and historical data are combined to dynamically calibrate a threshold value, it is ensured that parameter correlation analysis fits an actual working condition, and a technical scheme with comprehensiveness, accuracy and engineering practicability is provided for cable saddle state detection. And the safety monitoring level of a major engineering structure is improved.

A high-temperature tank (116) includes an optical window which transmits a laser (132) and is provided at one end, and a right-angle conical mirror (102) which is provided at the other end, has an opening (106) at the apex and which reflects laser light (132) incident from the optical window towards the one end in an area other than the opening (106). A magnetic field generator (112) generates a magnetic field in the region of intersection of the laser reflected by the right-angle conical mirror (102). A magnetic field gradient relaxation module (130) generates a relaxation magnetic field which relaxes the gradient of the magnetic field generated by the magnetic field generator (112).

The invention provides a method for constellation time keeping in a free operation state of a satellite-borne atomic clock, and the method comprises the steps: generating an adjustable second time frequency signal through frequency synthesis based on a first time frequency signal outputted by the satellite-borne atomic clock; comparing and measuring the phase difference between the two and sending the phase difference to an inter-satellite link; through inter-satellite measurement and interaction, obtaining a clock error between the second time frequency signals of all satellites, and converting to obtain a clock error between the first time frequency signals of all satellites; and on the basis, a clock difference parameter between the constellation time and the first time-frequency signal is calculated and converted into a clock difference parameter between the constellation time and the second time-frequency signal, a frequency adjustment parameter is generated through a control algorithm, and the second time-frequency signal is controlled to gradually approach the constellation time. The invention further provides a device for constellation time keeping in the free operation state of the satellite-borne atomic clock. Therefore, the free operation requirement and the irregular frequency modulation requirement of the satellite-borne atomic clock under the navigation constellation autonomous time keeping scene can be considered, and the constellation autonomous time keeping precision and the user service performance are improved.

This invention discloses a rubidium atomic clock frequency adaptive prediction method and system based on LSTM network, belonging to the field of time and frequency technology. The invention includes the following steps: Step 1. Data acquisition; Step 2. Filtering and denoising preprocessing; Step 3. Normalization processing; Step 4. LSTM model training and deployment; Step 5. Frequency prediction; Step 6. Online model adaptation. This invention employs a Long Short-Term Memory (LSTM) network, a special type of recurrent neural network, which can effectively learn the complex time dependencies and noise patterns in rubidium atomic clock time and frequency data. The inherent gating mechanism of the LSTM model makes it adept at capturing long-term dependencies in time series, thus enabling high-precision prediction of short-term frequency fluctuations. Through an online fine-tuning mechanism, this invention allows the LSTM model to continuously adapt to the individual drift and aging characteristics of a single rubidium atomic clock, achieving precise optimization for each clock and model, significantly improving the practicality and long-term stability of the method.

This invention relates to a multi-mode communication release-response integrated time-synchronized underwater mooring system and method, and relates to the fields of underwater acoustic communication networks and underwater positioning and navigation technology. The purpose of this invention is to solve the problems of poor reusability of existing underwater mooring systems in complex and diverse application scenarios, the insynchrony of time among mooring nodes making it impossible to coordinate data aggregation or communication reporting tasks at precise times, resulting in single-function underwater mooring equipment, low resource utilization, and large reference time errors. The system includes multiple dual-master control mooring communication units and an external battery compartment, integrating spread spectrum communication, OFDM communication, multiple orthogonal response, atomic clock timekeeping, release control, and positioning functions; it achieves time synchronization and local timekeeping through 1PPS signals and GPRMC information or absolute time information; after deployment, each node completes multi-mode signal reception and response according to a preset mode, and serves as a positioning anchor point to achieve platform positioning through a long baseline positioning algorithm; after the task is completed, it is released and surfaced under control.

The application discloses a three-dimensional magnetic optical trap device capable of adjusting cold atom projection speed, comprising a vacuum cavity, wherein an alkali metal source, a first reflector, a second reflector and a third reflector are arranged in the vacuum cavity; a first transmission window piece, a second transmission window piece and a third transmission window piece are arranged on the vacuum cavity; and a cold atom projection adjusting method is disclosed. The six lasers required by the traditional magnetic optical trap are reduced to three lasers through the reflectors integrated in the vacuum cavity, the volume and weight of the system are greatly reduced, the space structure is simplified, the stability of the device is improved, the device can be applied to the fields of atomic sensing technology and atomic clock and the like, and the integration degree of the instrument is improved.

The invention provides a temperature self-adaptive frequency locking system and method applied to a CPT atomic clock, the system comprises a TEC heating sheet 1, a VCSEL laser 2, a temperature sensor 3, a gas chamber shell 4, a gas chamber 5 and the like, the VCSEL laser 2 is tightly attached to the surface of the TEC heating sheet 1, the temperature sensor 4 is arranged near the outer side of the gas chamber 5, the gas chamber 5 is wrapped by the gas chamber shell 4, and the TEC heating sheet 1 is arranged in the gas chamber shell 4. A heating resistor network 7 is arranged at the lower part of the air chamber 5; a laser beam emitted by the VCSEL laser 2 passes through the gas chamber 5 and then is received by the photoelectric sensor 6. The whole control is executed by a CPT atomic clock control system 9; and feedback signals of the temperature sensor 4 are respectively transmitted to the frequency drift algorithm processing module 10 and the control parameter adjustment algorithm processing module 11. Output signals of the two modules are transmitted to a CPT atomic clock control system 9; a feedback signal of the photoelectric sensor 6 is also transmitted to the CPT atomic clock control system 9; the VCO voltage-controlled crystal oscillator 8 is controlled by the CPT atomic clock control system 9 and outputs frequency to the outside.

The application relates to the technical field of atomic clocks, and provides a chip optical clock based on a modulation transfer spectrum principle and an implementation method thereof. The chip optical clock comprises: an on-chip narrow-line-width laser for emitting laser; a waveguide beam splitter for splitting the laser into two beams; one beam of laser is used for inputting into an electro-optic phase modulator, and the other beam of laser is used for inputting into a MEMS atomic cell; the electro-optic phase modulator is used for phase-modulating the one beam of laser and outputting pump light; the MEMS atomic cell is used for modulating and transferring the other beam of laser based on the pump light to obtain a probe spectrum; a photoelectric detector is used for converting the detected probe spectrum into an electric signal; a high-speed servo feedback control integrated circuit is used for converting the received electric signal into a feedback control signal, inputting the feedback control signal into a feedback control port of the on-chip narrow-line-width laser, realizing full-bandwidth locking, and outputting an optical clock signal. The above-designed chip optical clock has small integration difficulty and is easy to realize full-chip optical clock.

The invention discloses a multi-source heterogeneous clock group management system and method based on an ALGOS time scale algorithm. The method comprises the steps that an atomic clock group outputs multiple paths of radio frequency analog signals; the signal frequency discrimination comparison module is used for converting the radio frequency analog signal into a digital signal, measuring the frequency and calculating frequency difference data; the atomic time scale calculation module converts the frequency difference data into frequency difference data relative to the atomic time scale, predicts the clock face frequency reading, determines the weight of each atomic clock according to the forecast residual error, and calculates the atomic time correction through weighted average; the frequency scale control module calculates the frequency offset according to the atomic time correction, the crystal oscillator and the atomic clock signal, and generates control voltage; and the local voltage-controlled crystal oscillator receives the control voltage and reproduces a high-precision time-frequency reference signal synchronized with the atomic clock group. According to the invention, the operation state of the atomic clock is not adjusted, only discrete sampling is carried out, the advantages of the clock group are fused by utilizing the ALGOS algorithm, the long-term stability of the output signal is improved by controlling the high-reliability voltage-controlled crystal oscillator, and the influence of frequency drift, intermittent start and stop and noise interference is effectively inhibited.

The invention relates to a sea surface gravitational potential measuring method and device based on a satellite time-frequency strategy, and the method comprises the steps: placing two measuring systems at a land measuring station at the same time, carrying out the calibration and adjustment of clocks, and determining the system error between the clocks through zero baseline comparison; the mobile measurement system is placed on a ship and advances according to a designed experiment route, the measurement system can continuously operate, and position information and gravity potential information on an air route can be measured by combining a positioning system; the ship can sail according to any route, and the gravitational potential difference of any position on the sea surface can be measured with the help of a satellite; after the ship returns, the mobile measurement system and the fixed measurement system need to be compared again, and it is ensured that no large error occurs in the experiment process of the atomic clock. Therefore, the problems that gravitational potential data in the global range cannot be comprehensively obtained in real time, and on-sea gravitational potential measurement and cross-sea measurement are difficult to achieve are solved.

The embodiment of the invention discloses a CPT atomic clock circuit system. The system comprises a controller used for sending a first control signal to an integrated microwave source, sending a second control signal to an integrated temperature controller, collecting the current temperature of a CPT atomic clock physical system, and sending a third control signal to the CPT atomic clock physical system according to the current temperature of the CPT atomic clock physical system; the integrated microwave source is used for sending a microwave signal to the CPT atomic clock physical system according to the first control signal; the integrated temperature controller is used for collecting the current temperature of the laser, controlling the laser to work at a first preset temperature according to the second control signal and the current temperature of the laser, and sending a laser signal to the CPT atomic clock physical system; and the CPT atomic clock physical system is used for working at a second preset temperature according to the third control signal and outputting a laser feedback signal according to the microwave signal and the laser signal.

The invention provides an atomic clock error simulation method and device, equipment and a storage medium. Relates to the technical field of high-stability time keeping. The method comprises the following steps: decomposing the clock difference of an atomic clock into a deterministic trend term and a random noise term, and obtaining a deterministic trend term simulation value through polynomial fitting; performing identification and intensity decomposition on the random noise item according to the clock difference frequency stability; simulating the random running frequency modulation noise, the random walking frequency modulation noise, the white frequency modulation noise and the white phase modulation noise according to a set simulation formula to obtain corresponding power law noise simulation values; for the flicker walk frequency modulation noise, the flicker frequency modulation noise and the flicker phase modulation noise, fitting by using a first-order Markov process according to the power spectrum density characteristic to obtain a corresponding power law noise simulation value; and adding the deterministic trend term simulation value and various power law noise simulation values to obtain a simulation clock difference value of the corresponding stability. According to the method, atomic clock error simulation which is clear in physical significance, low in calculation cost and high in interpretability can be realized.

The invention discloses a cloud computing analysis method based on a time mark pulse sequence, and belongs to the technical field of signal processing. The method is used for solving the technical problems that in an existing scheme, delay nonlinearity caused by multipath propagation is not considered, and effective decoupling cannot be achieved due to a coupling effect existing in atomic clock error estimation and system deviation. A direct component and a scattering component can be distinguished through time scale layered mapping, and the amplitude-phase-frequency coupling effect of multi-path propagation is covered by fusing the three-dimensional characteristics of delay inequality, amplitude attenuation and frequency drift; the nonlinear mapping capability of the hyperbolic tangent kernel function is superior to that of a linear model, and the hyperbolic tangent kernel function can adapt to time delay nonlinear change in a complex electromagnetic environment; clock error, time delay parameters and system deviation are modeled in a unified mode, error accumulation caused by traditional separation estimation is avoided, variable dependency is quantized through an information theory tool, mutual information decoupling is achieved, robustness is enhanced, and a decoupling result directly corresponds to an atomic clock core index and system interference.

This invention discloses a method, system, device, and medium for evaluating the performance of a high-precision space atomic clock. The method includes the following steps: calculating the relative clock difference between space and ground based on a two-way time difference measurement method; wherein, a distance inconsistency delay error is introduced for correction during the calculation of the relative clock difference; calculating stability, sky stability, and space-to-ground alignment accuracy based on the calculated relative clock difference; and achieving performance evaluation of the high-precision space atomic clock based on the stability, sky stability, and space-to-ground alignment accuracy. In the technical solution provided by this invention, a space-to-ground time alignment network system based on a microwave ranging link is used, and the relative clock difference information between space and ground is calculated based on a two-way time difference measurement method. Finally, the performance of the high-precision space atomic clock can be evaluated using the relative clock difference information.

Optical frequency reference apparatus (10) comprising - an atomic vapor cell (1), containing a vapor of reference atoms, said atomic vapor cell (1) comprising a first end (41) having a first window (4) and a second end (61), - a laser source (11) for generating a laser probe beam (3) adapted to excite a two-photon optical transition of said reference atoms, - an optical detector (14), adapted to detect a fluorescence signal emitted by said reference atoms, and - at least one reflective element (5, 15) wherein the laser source (11), the atomic vapor cell (1) and the at least one reflective element (5, 15) are configured such that, in operation, the probe beam (3) enters the atomic vapor cell (1) through said first window (4) at said first end (41) and crosses said vapor of reference atoms until said second end (61) through a defined optical path in a first forward direction (3a), the probe beam (3) is reflected backwards by said at least one reflective element (5, 15) and crosses said vapor of reference atoms a second time through the same defined optical path, in a second direction (3b) opposite to the first forward direction (3a), characterized in that the optical frequency reference apparatus (10) further comprises means (7, 9) for absorbing the reflected laser probe beam (3) exiting from the atomic vapor cell (1) according to the second direction (3b).

A method for synchronous excitation of multiple exciters relates to the field of dynamic testing and vibration control technology for large civil structures. The method includes the following steps: after constructing a unified time reference based on satellite navigation signals and a rubidium atomic clock, excitation amplitude and phase parameters are obtained based on the target modal requirements, and these parameters are sent to all exciter slave stations; the exciter slave stations generate a reference trajectory based on the excitation amplitude and phase parameters, enabling the exciter motor shaft angle to follow the reference trajectory in real time and output the target excitation; the phase error is obtained based on the measured excitation phase value and the reference trajectory, and then the motor angular velocity of the exciter is corrected based on the phase error. This invention solves the problems of startup phase error and long-term frequency drift in master-slave triggering schemes, ensuring synchronous start-up of all exciters. Combined with dynamic correction of the exciter motor angular velocity, it suppresses phase drift during long-term operation, significantly improving the excitation efficiency of higher-order modes and the clarity of the response signal.