222 results about "Optical frequency comb" patented technology

The invention relates to the technical field of laser ranging, in particular to a double-optical-comb hybrid ranging device which comprises a signal detection optical path system and a signal demodulation optical path system. Wherein the signal detection optical path system comprises a first optical frequency comb, a first optical isolator, a first optical collimator, a first beam splitter prism, a reference mirror, a Faraday rotator, a convergence mirror and a target reflector; the signal demodulation optical path system comprises a second optical frequency comb, a second optical isolator, a second optical collimator, a half-wave plate, a second beam splitter prism, a third beam splitter prism, a first polarization controller, a first photoelectric detector, a reflector, a polarization beam splitter prism, a second polarization controller and a second photoelectric detector. A third polarization controller; and a third photoelectric detector. According to the invention, three ranging technologies of asynchronous optical sampling ranging, multi-heterodyne interference ranging and synthetic wavelength ranging are fused, and the problem that a large ranging range and high ranging precision cannot be simultaneously considered in the ranging process is solved.

Disclosed herein is an optical frequency comb generator for a distributed acoustic anomaly detection system. The system can include a continuous wave frequency modulated laser source configured to generate a laser signal. The system can include an acousto-optical modulator configured to modulate the laser signal by altering an amplitude and / or frequency of the laser signal based on an RF drive signal applied to the AOM, and to output an optical pulse with multiple frequency sidebands based on the modulation. The output can form an optical frequency comb usable detecting and locating acoustic anomalies within a structure under observation.

An optical comb generator receives light from at least two continuous wave laser sources, produces a different frequency comb from each laser source, and produces an output that it the simultaneous combination of the different frequency combs. The different frequency combs span different frequency bands, but at least partially overlap in frequency with an adjacent comb in a region of overlap. A spectral filter produces a filtered output that has at least one pair of tones from the region of overlap, the pair of tones comprising one tone from each of two adjacent combs. Feedback control based on the filtered output is applied to adjust the light entering the comb generator such that the frequencies and phases of the pair of tones from the region of overlap are aligned. In this way, the multiple different overlapping combs are stitched together to form a single seamless comb spanning a broader frequency range.

The invention discloses a beat frequency comparison device mediated by an optical frequency comb. The beat frequency comparison device comprises the optical frequency comb, a first frequency stabilized laser, a first beat frequency device, a first frequency mixer, a first high-pass filter, a second frequency stabilized laser, a second beat frequency device, a second frequency mixer, a second high-pass filter, a DDS signal generator, a third frequency mixer and a low-pass filter. Frequency-stabilized lasers output by the first frequency-stabilized laser and the second frequency-stabilized laser and an optical frequency comb output by the optical frequency comb are subjected to beat frequency in the first beat frequency device and the second beat frequency device respectively, and first beat frequency and second beat frequency are obtained; the first beat frequency and the second beat frequency are mixed with the carrier envelope offset frequency of the optical frequency comb, and a first sum frequency and a second sum frequency are filtered out; the first sum frequency obtains a synthetic frequency through direct digital frequency synthesis; the second sum frequency and the synthetic frequency are mixed in the third mixer, and then the difference frequency is filtered out through the low-pass filter. According to the invention, beat frequency comparison of frequency-stabilized lasers with different wavelengths can be realized, and the influence of the stability of the optical frequency comb is avoided.

The invention provides a mid-infrared optical frequency comb. The mid-infrared optical frequency comb comprises a near-infrared optical frequency comb seed source of a polarization-maintaining all-fiber structure; the all-fiber nonlinear amplification and pulse compression module is connected with the near-infrared optical frequency comb seed source through a polarization maintaining fiber and is used for amplifying the power of the seed light and compressing the pulse width after generating a linear chirped pulse; the all-fiber nonlinear spectrum broadening module is connected with the all-fiber nonlinear amplification and pulse compression module through a polarization maintaining fiber and is used for broadening a laser spectrum; the difference frequency module is used for receiving the laser pulse processed by the all-fiber nonlinear spectrum broadening module and generating an intermediate infrared laser pulse through intra-pulse self-difference frequency; wherein the seed source, the all-fiber nonlinear amplification and pulse compression module and the all-fiber nonlinear spectrum broadening module are connected through a polarization maintaining fiber to form an all-fiber integrated structure. By adopting the scheme, the anti-interference capability of the system can be enhanced, miniaturization and high operation reliability are realized, the debugging process is simplified, and the difference frequency efficiency is improved.

The invention discloses a device for generating Mach-Zehnder interference, a photo-thermal spectrum gas sensing device based on the device and a detection method, and belongs to the technical field of laser spectrum gas sensing. The interference device sequentially comprises an optical frequency comb and a first light beam splitter on a light transmission path; a movable arm reflector group is arranged on the light path of one light beam B in the two light beams split by the first light beam splitter, the path of the light beam B is changed through the movable arm reflector group, the light beam B intersects with the light path of the other light beam C, and a beam combiner is arranged at the intersection; the movable arm reflector group is connected with a driving mechanism, the driving mechanism is used for driving the movable arm reflector group to do linear motion, and the track of the linear motion is parallel to the straight line where the light beam B is located. The interference device does not need to use a local oscillator optical comb and a signal optical comb to carry out multi-heterodyne interference, can directly use the moving speed of a movable arm reflector group in a Mach-Zehnder interference structure to calculate a down-conversion factor, and maps each longitudinal mode of the signal optical comb in an optical frequency to a radio frequency component one by one.

The invention provides a terahertz frequency comb generation verification method and system based on an optical fiber microcavity optical frequency comb, and the method comprises the steps: injecting a continuous wave laser into an optical fiber microcavity resonator to generate a stable Kerr optical frequency comb, enabling the Kerr optical frequency comb to work in a single soliton state or a soliton crystal state, and obtaining an optical frequency reference with low phase noise. Furthermore, spectrum selection is performed on the optical frequency comb, multiple groups of optical comb tooth pairs comprising comb teeth of different orders are actively selected, and the optical frequency difference of each group of comb tooth pairs is directly converted into an electric signal in a terahertz frequency band by utilizing a beat frequency effect of a photoelectric detector. A plurality of terahertz electric signals generated by different comb tooth pairs are integrated to form a multi-channel terahertz frequency comb. The method allows a plurality of discrete and frequency-controllable terahertz signal channels to be generated in parallel on a single optical platform through one-time optical processing and photoelectric conversion, so that multichannel terahertz frequency comb generation is realized.

This invention discloses a vehicle-mounted dual-optical-comb system for outdoor testing, comprising an oscillator module, a power amplifier module, a frequency conversion module, a gas measurement module, a signal detection, acquisition, and processing module, and a vehicle-mounted platform module. The oscillator module generates two optical frequency comb signals with slightly different repetition frequencies. The power amplifier module amplifies the two optical frequency comb signals. The frequency conversion module outputs a combined dual-optical-comb beam. The gas measurement module enables the dual-optical-comb beam to interact with the gas to be tested in an open environment. The signal detection, acquisition, and processing module receives the optical signal absorbed by the gas to be tested, converts it into an electrical signal, and acquires and processes the electrical signal to obtain the absorption spectrum information of the gas to be tested. The vehicle-mounted platform module is used to fix and install each module. The advantages of this invention are: stable operation, strong resistance to environmental interference, low power consumption, and suitability for long-term vehicle-mounted operation.

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.

The invention provides a system and method for enhancing the spectrum demodulation rate of a dual-optical-frequency comb, and the system comprises a circulation light path which carries out the light splitting of excitation pulse light which is inputted to the circulation light path and corresponds to a first repetition frequency, thereby enabling one part of the excitation pulse light to be outputted towards a unit to be detected, and enabling the other part of the excitation pulse light to circulate along the circulation light path; the to-be-tested unit is used for modulating the excitation pulse light and outputting processing signal light carrying dynamic spectrum information generated based on an actual dynamic spectrum of the to-be-tested unit; the light combining unit is used for coupling the processing signal light and the sampling pulse light and outputting coupled signal light; the photoelectric detector performs light field cross-correlation-based detection on the coupled signal light and outputs a periodic electric signal; and the data acquisition and processing unit processes the periodic electric signal to obtain an actual dynamic spectrum corresponding to the unit to be detected. The detection efficiency is at least improved.

The invention discloses a micro-cavity optical frequency comb and a structural parameter determination method thereof, relates to the technical field of optical frequency combs, and aims to solve the problems that in the prior art, a traditional optical frequency comb is limited in structural regulation dimension, and an existing design method is difficult to efficiently and accurately achieve matching of spectrum requirements and structural parameters. The micro-cavity optical frequency comb comprises an input / output waveguide and a grating-assisted nested micro-ring cavity. The input / output waveguide is coupled with the grating-assisted nested micro-ring cavity; the grating auxiliary nested micro-ring cavity comprises an outer micro-ring, an inner micro-ring and a grating; the grating is formed on the outer micro-ring or the inner micro-ring; the outer micro-ring and the inner micro-ring are coupled to form a nested resonant structure; structural parameters corresponding to the grating-assisted nested micro-ring cavity are obtained through light field steady-state verification based on trained reverse neural network prediction; the trained reverse neural network is obtained based on the forward neural network. The method is used for realizing efficient and accurate design of the microcavity optical frequency comb and meeting the target spectrum requirement.

The application discloses a microwave photon frequency hopping signal generation device and method based on an optical switch and belongs to the technical field of optical communication. The application is composed of a light source, a beam splitter, an optical frequency comb generator, an electro-optical frequency shifter, an acousto-optic modulator, a digital frequency synthesizer, a filter array, a signal control unit, an electrically controlled high-speed optical switch, a beam combiner and a photoelectric detector. The application separates optical frequency comb teeth by using an ultra-narrow bandwidth optical filter, selects and opens the frequency hopping signal generated by the local light beat frequency through the optical switch, and can generate a high-speed high-order high-stability frequency hopping signal compared with the prior art.

The invention relates to the technical field of satellite communication, and discloses a multiband local oscillator signal generation system and method, and the system comprises a laser, an optical splitter, a first optical modulator, a second optical modulator, an arbitrary waveform generator, an optical coupler, and a signal generation module. The optical splitter divides an optical carrier generated by the laser into first carrier light and second carrier light; the arbitrary waveform generator converts the digital signal into a digital baseband signal to be modulated; the first optical modulator modulates the first baseband signal to the first carrier light to obtain a first optical frequency comb; a second optical modulator modulates a second baseband signal to second carrier light to obtain a second optical frequency comb; the optical coupler couples the first optical frequency comb and the second optical frequency comb into a laser signal; the signal generation module converts the laser signal into a local oscillator millimeter wave signal. Dual-coherent optical frequency combs with different comb tooth intervals are generated through modulation of digital signals with different bit rates, tuning of local oscillation signals is achieved, and the requirement for multi-frequency local oscillation is met.

The invention relates to an intermediate infrared micro comb generation system and method, in particular to an intermediate infrared micro comb key starting type generation system and method based on a negative thermo-optic effect. In order to solve the problems that a traditional mid-infrared light frequency comb is limited in size, weight, power consumption and repetition frequency, and the mid-infrared band faces the defects that the light source tuning rate is low, the micro-cavity quality factor is low and the key device performance is poor, the invention provides the mid-infrared light frequency comb. The intermediate infrared micro comb key starting type generation system based on the negative thermo-optic effect comprises a pumping unit used for providing pumping light, a microcavity unit used for generating a nonlinear four-wave mixing process and the negative thermo-optic effect, and a detection unit used for receiving an intermediate infrared micro comb and recording time domain information and frequency domain information of the intermediate infrared micro comb. Meanwhile, the invention provides a key-starting type generation method of the mid-infrared micro comb based on the negative thermo-optical effect, which is self-starting, wide in spectral bandwidth, high in repetition frequency and high in stability based on the system.

An interferometric resonator optical gyroscope includes an optical frequency comb generator configured to generate an optical frequency comb. Optical signals representative of the optical frequency comb pass through an optical resonator in different directions, and a rotation rate is determined based on the extent of interference between the optical signals. Parameters of the optical frequency comb generator can be controlled by a control servo based on an intensity of the optical signals after propagating in the optical resonator. Utilizing an optical frequency comb generator reduces the bias error during gyroscope operation.

A movement prediction apparatus including first and second light output devices, a light reception device, and a processor. The first light output device outputs output-light having a spectral component of a first optical frequency comb of which a frequency comb interval is a first interval. The second light output device outputs reference light having a spectral component of a second optical frequency comb of which a frequency comb interval is a second interval. The light reception device receives combination light that is a combination of the output-light, reflection light that is the output-light reflected by a flying object rotor wing, and the reference light, and measures a distance to the rotor wing based on the combination light. The processor calculates a rotation amount that represents a rotational speed of the rotor wing based on a change amount of the measured distance, and predicts a movement of the flying object.

LIDAR distance measuring device (10), comprising: a laser (12) for generating a laser beam, a frequency comb generator (14) configured to generate at least one optical frequency comb signal (37) based on the laser beam, a signal splitting unit (16) which is configured to split the optical frequency comb signal (37) into different optical signal channels (34), each of which is assigned a respective wavelength range, a channel matching unit (18) which is configured to change at least two optical signal channels (34) in their relative position to each other, a transmitting unit (20) which is configured to send light associated with the modified optical signal channels (36) as transmitting light (22) into a measuring area (24), a receiving unit (26) for receiving transmitted light reflected from objects (28) in the measuring range (24) as received light (30), and a signal processing unit (32) which is configured to determine a distance to the object (28) based on the received light (30) and in particular at least a part of the transmitted light (22).

The invention discloses a high-power micro-cavity optical frequency comb generation device and method, and solves the problems that an existing optical frequency comb system needs to adopt a high-speed tunable laser to carry out precise scanning locking on micro-cavity resonance, or depends on distributed feedback type semiconductor laser with extremely narrow linewidth to carry out optical injection feedback on an ultra-high-quality micro-cavity; in order to solve the problems of complex system structure and operation due to the fact that the existing optical frequency comb has the advantages of high repetition frequency, high comb power and wide spectral range, pumping is carried out by a pumping unit, optical frequency comb generation and synchronous power amplification are carried out through an active gain microcavity, and the channel interval (100GHz) of the optical frequency comb meets the international communication standard. The power of a single comb tooth reaches a hundred mu W level and is improved by 2-3 orders of magnitude compared with a common Kerr microcavity optical frequency comb scheme (a typical value is a hundred nW level), so that weak signal power amplification is not needed, and the Kerr microcavity optical frequency comb has important application value in the field of optical communication.

The present disclosure provides a device suitable for generating a frequency-stable microcavity optical frequency comb, comprising: a light source part configured to emit a light beam; a beam splitting device configured to split the light beam emitted by the light source part into a plurality of first light beams; a light source frequency determination unit connected with a first output port of the beam splitting device, the adjustment frequency being determined based on the absorption of the first light beams by atoms in the light source frequency determination unit, and the light source part adjusting the frequency of the emitted second light beams based on the adjustment frequency; a resonant microcavity connected with the light source frequency determination unit, the second light beams generating a first microcavity optical frequency comb in the resonant microcavity; and a modulation unit arranged between a second output port of the beam splitting device and the resonant microcavity, configured to modulate the second light beams into third light beams with repetition frequency information based on the repetition frequency of the first microcavity optical frequency comb, and the third light beams generating a second microcavity optical frequency comb in the resonant microcavity.

This invention provides an optical frequency comb frequency stabilization device and method. The device includes: a first optical filter configured to filter the optical frequency comb to obtain two comb teeth to be locked; an oscillation loop configured to oscillate based on the two comb teeth to be locked, generating an oscillation radio frequency signal at a first angular frequency and an oscillation radio frequency signal at a second angular frequency; and a feedback controller configured to perform mixing processing on the oscillation radio frequency signal at the first angular frequency, the oscillation radio frequency signal at the second angular frequency, and a radio frequency reference signal to extract a time-varying error signal, and output a control signal based on the error signal to lock the frequency of the optical frequency comb.

The application discloses an optical frequency comb automatic recovery device and method, and belongs to the field of silicon-based nonlinear optical photoelectric modulation. The application comprises a laser, an IQ modulator, an acousto-optic modulator, a fiber amplifier, a polarization controller, a micro-ring resonator, a phase-locked loop, an arbitrary waveform generator, a photoelectric detector, a PID module and an upper computer. Transmission loss of an optical frequency comb debugging system is tested, which comprises fiber loss before laser enters a microcavity and transmission loss after the laser enters the microcavity; the output frequency range of the phase-locked loop is adjusted, and frequency scanning is performed on the microcavity; laser wavelength is entered from blue detuning, the output power of the laser is gradually reduced through the acousto-optic modulator, and the wavelength is kept unchanged; when the PID detects a power rise, the laser power is quickly raised until the PID detects a rising step; the laser frequency is slowly increased and the power is kept unchanged until a single soliton optical frequency comb is observed; when the single soliton disappears, the control steps after the laser wavelength is entered from blue detuning are repeated, and the optical frequency comb is automatically recovered.

The invention discloses a programmable optical frequency comb light source based on a dispersion reconfigurable microcavity, and the structure of the programmable optical frequency comb light source comprises a grating writing and dispersion detection module, an integrated microcavity module with a photoinduced refraction characteristic, an optical comb pumping and spectrum sensing module, and a feedback control and signal processing module. The working principle is as follows: on a micro-ring resonant cavity with a photorefractive effect, laser is written into a programmable Bragg grating, so that a dispersion curve of the micro-cavity is reconstructed in real time; then, an intelligent feedback closed loop is formed by monitoring the spectrum and repetition frequency of the output optical comb and comparing the spectrum and repetition frequency with a target set by a user, and the grating pattern is automatically adjusted until the output spectrum is matched with the target. The programmable optical frequency comb light source can be dynamically reconstructed or switched according to different application requirements. The programmable optical frequency comb can be used as a light source module of a co-packaging optical technology, bandwidth density is improved, power consumption is reduced, and therefore the programmable optical frequency comb can be widely applied to interconnection of next-generation data centers.

1. Name of the designed product: Optical frequency comb generator. 2. Use of the designed product: for making optical pulse sequences in QKD (quantum key distribution) devices. 3. Design points of the designed product: in shape. 4. Picture or photo best indicating the design points: perspective view.

The invention relates to the technical field of laser light sources, in particular to a Kerr-dissipation soliton optical frequency comb light source excitation device. The device comprises a pump light source module, an optical fiber gain filtering module, a spatial light adjusting module and an optical fiber Fabry-Perot microcavity module, the pump light source module is used for generating a first optical signal; the optical fiber gain filtering module is used for gaining the first optical signal into a second optical signal; the second optical signal is continuous pump light; the spatial light adjustment module is used for performing light beam adjustment on the second light signal to obtain a third light signal; the third optical signal is a fixed polarization line polarization bandwidth optical signal; and the optical fiber Fabry-Perot micro-cavity module is used for performing frequency domain filtering processing on the third optical signal to obtain single-frequency continuous laser, and autonomously exciting the dissipative Kerr soliton optical frequency comb light source through the single-frequency continuous laser. According to the scheme, the problems of high cost and complex control of a traditional soliton micro-comb system are solved.

The application discloses a private network communication data processing method, relates to the technical field of communication, and comprises the following steps: constructing a unified time baseline, establishing a cause-and-effect sequence benchmark on the basis of the unified time baseline, extracting data backflow risk characteristics in link operation data, and generating risk prior data; scanning a cache area based on the risk prior data, identifying residual fingerprints and sequence hollow spectrum, calibrating back-feeding segments with backflow characteristics, and constructing an arrival threshold field consistent with the unified time baseline. The application realizes backflow risk identification by constructing a unified time baseline and a cause-and-effect sequence, blocks error segments from penetrating by combining a one-way submission channel and a shadow pipeline, realizes segment misplacement perception and isolation by introducing time watermarking and counting chains, completes data repair by using time inversion and error correction recovery, converges residual energy by combining an optical frequency comb and micro-injection, constructs a closed-loop regulation mechanism, and significantly improves the stability and security of private network communication.

The invention discloses a molecular spectrum scanning device and method based on cavity enhancement. The molecular spectrum scanning device comprises a stepping motor, a laser, a cavity enhancement spectrum system, a PDH locking system, an optical frequency comb, a wavelength meter, a spectrum data acquisition card, an industrial personal computer and a voltage amplifier. Through the PDH locking technology, the scanning laser frequency tracks the resonance mode of the optical resonant cavity in real time, the lock losing problem in the scanning process is solved, and high stability is ensured; meanwhile, an optical frequency comb is used as a frequency scale, and real-time and accurate absolute frequency measurement is carried out on the scanning laser through a wavemeter; active frequency locking and absolute frequency calibration technologies are organically combined, high-sensitivity, high-frequency-precision and high-stability cavity enhanced molecular absorption spectrum measurement is achieved, and the method is particularly suitable for the fields of trace gas detection, precision spectroscopy, atmospheric environment monitoring and the like.

The application discloses a kind of microcavity optical frequency comb ultra-high repetition frequency precision measurement system and method, solve the existing microcavity optical frequency comb repetition frequency measurement system because of facing electronic device frequency bandwidth bottleneck lead to the problem that measurable range is seriously limited, including optical rough measurement unit, comb tooth processing unit, modulation frequency shift unit, reference equalization unit, beam combination beat frequency unit and microwave precision measurement unit;Optical rough measurement unit is used to measure the repetition frequency of the light beam to be measured, and is divided into measurement beam and reference beam;Comb tooth processing unit is used to filter out target comb from measurement beam;Modulation frequency shift unit is used for electro-optic modulation to target comb;Reference equalization unit is used to control the reference comb power of reference beam to obtain better beat frequency detection effect;Beam combination beat frequency unit is used for optical beam combination beat frequency between target comb and reference comb and is divided into two beams;Microwave precision measurement unit is used to detect the beat frequency signal between target comb and reference comb, to realize the precision measurement of repetition frequency.

The application provides a light frequency comb generation device and method based on a series double microcavity structure. The device comprises a pump laser, an optical amplifier, a polarization controller, a first tapered lens fiber, a series double microcavity structure and a second tapered lens fiber connected in sequence. The second tapered lens fiber is connected to a spectrum analyzer and an oscilloscope through a first coupler. The optical amplifier is used to amplify the power of the output laser of the pump laser to reach the power threshold required for microcavity light frequency comb generation. The polarization controller is used to adjust the polarization mode of the output laser of the optical amplifier so that the polarization mode of the laser is the same as the polarization mode of the microcavity light frequency comb to be generated. The series double microcavity structure comprises a bus waveguide and two microcavities coupled thereto and is used to generate a light frequency comb. The application can solve the technical problems of high pump power, low energy conversion efficiency and low parameter selection freedom of the existing light frequency comb based on a single microcavity structure.

The invention discloses a free space coherent optical communication system and method based on optical frequency comb multi-mode extraction, and belongs to the field of free space coherent optical communication. The system comprises an optical frequency comb multi-mode extraction module, a free space coherent light communication transmitting module and a free space coherent light communication receiving module. According to the invention, the injection locking and optical phase-locked loop technology of the butterfly-shaped semiconductor laser is adopted, so that a plurality of ultra-narrow linewidth optical carriers can be extracted from the optical frequency comb locked to the ultra-stable cavity. The multi-mode high-stability optical carrier generation method and the real-time power fluctuation compensation method are adopted, and the communication quality of the free space coherent optical communication system is improved. Advanced modulation formats such as DP-QPSK and the like and higher modulation rate can be realized at a transmitting end, better anti-interference capability is realized in free space transmission, and optical signal receiving power stability is higher. And self-coherent detection is realized at a receiving end, the communication quality is improved, and digital signal processing algorithms such as frequency offset estimation are simplified.

The invention provides an optical frequency comb modulation system for a quantum dot mode-locked laser, which comprises a quantum dot mode-locked laser, a light splitting element, an optical feedback path and an optical measurement path, and is characterized in that the quantum dot laser is internally provided with a laser cavity, and two ends of the quantum dot laser can output laser; one end of the quantum dot laser is connected with the input end of the light splitting element, the output end of the light splitting element is connected with the input end of the optical feedback path and the input end of the optical measurement path, and a first deviation controller and a back reflector which are matched with each other are arranged in the optical feedback path. The quantum dot laser, the light splitting element, the first deviation controller and the back reflector are connected through optical fibers or waveguides. The method has the advantages that tuning of the modulation state of the optical frequency comb can be achieved, the distribution range of the FM comb is compressed, and the working range of the AM comb is widened.