CN119439181B - Single-optical-frequency-comb-assisted laser phase distance estimation method and device - Google Patents
Single-optical-frequency-comb-assisted laser phase distance estimation method and deviceInfo
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- CN119439181B CN119439181B CN202411577933.7A CN202411577933A CN119439181B CN 119439181 B CN119439181 B CN 119439181B CN 202411577933 A CN202411577933 A CN 202411577933A CN 119439181 B CN119439181 B CN 119439181B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/4808—Evaluating distance, position or velocity data
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/486—Receivers
- G01S7/487—Extracting wanted echo signals, e.g. pulse detection
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Abstract
The invention discloses a single optical frequency comb-assisted laser phase distance estimation method and a device. The method comprises the steps of obtaining a detection light signal and a reference light signal, measuring the space distance of a link to be detected by the detection light signal to obtain a detection echo light signal, performing double-sideband intensity modulation on the reference light signal and the detection echo light signal by using a single-frequency microwave signal, performing beat frequency processing on the modulated reference light signal and the modulated detection echo light signal to obtain a reference light current signal and a detection echo light current signal, performing analog-to-digital conversion on the reference light current signal and the detection echo light current signal, respectively calculating frequency components obtained by the beat frequency of the reference light signal and the detection echo light signal, and performing defuzzification on a phase difference between corresponding frequency components of the reference light current signal and the detection echo light current signal to obtain the accurate space distance of the link to be detected. The invention greatly improves the ranging speed under the condition of ensuring the ranging range and the accuracy.
Description
Technical Field
The invention relates to an optical frequency comb distance measuring method, in particular to a single optical frequency comb-assisted laser phase distance estimating method and device.
Background
The laser ranging is a non-contact measuring technology, has the characteristics of good monochromaticity, strong directivity and high ranging precision, and is widely applied to the fields of national defense, construction industry, aerospace, engineering measurement and the like. In the conventional ranging method, the pulse method calculates the target distance by directly measuring the time difference between the transmitted pulse and the received pulse, the measuring speed is high, the measuring range can reach up to kilometers, but the ranging accuracy is limited by the width of the pulse, and the maximum can only reach millimeter level. The frequency scanning interferometry calculates the target distance by continuously linearly sweeping the laser and obtaining time delay information at the interference frequency, but is limited by the frequency tuning speed of the laser and the subsequent algorithm processing, so that the measuring speed is slower. The phase method is to calculate the target distance indirectly according to the phase difference generated by the modulated light wave going back and forth to the measured distance, the distance measurement accuracy depends on the high-frequency signal, a high-performance detector and a high-speed ADC are needed, the processor has large calculation amount, and the hardware cost of the system is high. In addition, because of the 2 pi ambiguity in the phase obtained by the phase detector, a phase-push method is often used to solve this problem, which requires modulating a series of microwave signals to perform phase unwrapping, thus limiting the measurement speed. The optical frequency comb becomes a new measurement means by the characteristics of ultrahigh frequency stability, good coherence, wide frequency spectrum range and the like, and brings new thought and method for the development of the traditional absolute distance measurement technology. Such as the conventional double comb ranging method, but it requires locking the repetition frequency and absolute frequency of the two-column frequency comb, which makes the system more complex and expensive.
In summary, the existing optical ranging system has the following problems that high-precision light time delay measurement cannot be achieved by a pulse method, the existing high-precision large-range ranging methods have the problems of high requirements on performance of devices such as ADC (analog to digital converter) and low ranging speed, and the traditional double-optical-frequency comb ranging system is complex and high in cost.
Disclosure of Invention
The invention aims to solve any problem in the prior art, and provides a single optical frequency comb-assisted laser phase distance estimation method and device, so as to realize high-precision quick distance measurement of a single optical frequency comb, and the specific technical scheme is as follows:
In a first aspect, the present invention provides a single optical frequency comb-assisted laser phase pitch estimation method, including:
acquiring a detection light signal and a reference light signal corresponding to the detection light signal, wherein the detection light signal and the reference light signal are optical frequency comb signals;
Measuring the space distance of the link to be measured by using the detection light signal to obtain a detection echo light signal;
performing double-sideband intensity modulation on the reference optical signal and the detection echo optical signal by using a single-frequency microwave signal;
performing beat frequency processing on the modulated reference light signal and the modulated detection echo light signal respectively to obtain a reference photocurrent signal and a detection echo photocurrent signal;
performing analog-to-digital conversion on the reference photocurrent signal and the detection echo photocurrent signal;
respectively calculating frequency components obtained by the beat frequency of the modulated reference light signal and the modulated detection echo light signal in a digital domain;
And the phase difference between the corresponding frequency components of the reference photocurrent signal and the detected echo photocurrent signal is deblurred by using a time phase method, so that the accurate spatial distance of the link to be detected is obtained.
Further, the acquiring the detection light signal and the reference light signal corresponding to the detection light signal includes:
gating the optical frequency comb signals locked by the repetition frequency;
and dividing the optical frequency comb signal after gating into the reference optical signal and the detection optical signal.
Further, the performing double-sideband intensity modulation on the reference optical signal and the detection echo optical signal by using a single-frequency microwave signal includes:
and performing double-sideband intensity modulation on the reference optical signal and the detection echo optical signal by using a high-frequency microwave signal of more than 40 GHz.
Further, the calculating, in the digital domain, frequency components obtained by beat frequencies of the modulated reference optical signal and the detected echo optical signal respectively includes:
Determining a first frequency component obtained by the comb tooth space beat frequency with the minimum distance between the reference optical signal and the reference optical signal after modulation and a second frequency component obtained by the comb tooth space second small beat frequency before modulation in a digital domain, and determining a first frequency component obtained by the comb tooth space beat frequency with the minimum distance between the detection echo optical signal and the detection echo optical signal after modulation and a second frequency component obtained by the comb tooth space second small beat frequency before modulation.
Further, the method for disambiguating a phase difference between the frequency components corresponding to the reference photocurrent signal and the detected echo photocurrent signal by using a time phase method to obtain a spatial distance of the link to be measured includes:
Calculating integer ambiguity corresponding to a phase difference between corresponding frequency components of the reference photocurrent signal and the detection echo photocurrent signal by using a time phase method;
calculating the accurate time delay introduced by the space link to be tested by using the integer ambiguity;
and calculating the space distance of the link to be measured according to the accurate time delay.
Further, the calculating the integer ambiguity corresponding to the phase difference between the frequency components of the reference photocurrent signal and the detected echo photocurrent signal by using a time phase method includes:
Extracting a phase difference between corresponding frequency components of the reference photocurrent signal and the detection echo photocurrent signal;
And optimizing the rough time delay which is directly obtained from the time domain and can indirectly represent the link distance to be measured according to the phase difference between the time domain pulse number difference corresponding to the reference photocurrent signal and the detection echo photocurrent signal and the corresponding frequency component.
And acquiring the integer ambiguity according to the optimized rough time delay.
In a second aspect, the present invention provides a single optical frequency comb-assisted laser phase pitch estimation device, comprising:
The signal acquisition module is used for acquiring a detection light signal and a reference light signal corresponding to the detection light signal, wherein the detection light signal and the reference light signal are optical frequency comb signals;
the measuring module is used for measuring the space distance of the link to be measured by utilizing the detection light signal to obtain a detection echo light signal;
the intensity modulation module is used for carrying out double-sideband intensity modulation on the reference optical signal and the detection echo optical signal by utilizing a single-frequency microwave signal;
the photoelectric conversion module is used for performing beat frequency processing on the modulated reference light signal and the modulated detection echo light signal respectively to obtain a reference photocurrent signal and a detection echo photocurrent signal;
the analog-to-digital conversion module is used for carrying out analog-to-digital conversion on the reference photocurrent signal and the detection echo photocurrent signal;
A resolving module for respectively calculating frequency components of the modulated reference light signal and the detected echo light signal after beat frequency in a digital domain, and
And the phase difference between the corresponding frequency components of the reference photocurrent signal and the detected echo photocurrent signal is deblurred by using a time phase method, so that the accurate spatial distance of the link to be detected is obtained.
Further, the signal acquisition module includes:
The optical frequency comb source is used for generating an optical frequency comb signal;
the optical switch is connected with the optical frequency comb and is used for gating the optical frequency comb signal locked by the repetition frequency;
and the coupler is connected with the optical switch and is used for dividing the optical frequency comb signal after gating into the reference optical signal and the detection optical signal.
Further, the device also comprises a microwave source, wherein the reference input end of the microwave source is connected with the optical frequency comb source and the optical switch, and the output end of the microwave source is connected with the intensity modulation module.
Further, the signal acquisition module, the microwave source, the analog-to-digital converter and the resolving module are locked in time synchronization.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
The technical scheme disclosed by the invention can realize high-precision quick ranging of the single optical frequency comb, greatly reduces the requirements on data processing and the analog-to-digital converter by using the low-speed analog-to-digital converter, greatly improves the ranging speed under the condition of ensuring the ranging range and the precision, reduces the requirement on high-stability frequency locking compared with the traditional double optical frequency comb ranging scheme, has lower realization cost and expands the non-fuzzy measuring range of the single optical comb.
Drawings
FIG. 1 is a schematic flow chart of a single optical frequency comb-assisted laser phase pitch estimation method disclosed by the invention;
FIG. 2 is a schematic block diagram of a single optical frequency comb-assisted laser phase pitch estimation device according to the present invention;
FIG. 3 is a schematic diagram of a single optical frequency comb-assisted laser phase estimation device according to an embodiment of the present invention.
Detailed Description
According to the technical scheme, high-precision quick ranging of the single optical frequency comb can be realized, analog-to-digital conversion can be performed through the low-speed analog-to-digital converter, the requirements on data processing and the analog-to-digital converter are greatly reduced, and the ranging speed is greatly improved under the condition that the ranging range and the accuracy are ensured. Compared with the traditional double-optical-frequency comb ranging scheme, the method reduces the requirement on high-stability frequency locking, is lower in implementation cost, and expands the non-fuzzy measurement range of the single optical comb.
As shown in fig. 1, the single optical frequency comb-assisted laser phase pitch estimation method provided by the invention is specifically as follows:
S1, acquiring a detection light signal and a reference light signal corresponding to the detection light signal.
The detection optical signal and the reference optical signal are divided into two paths of signals after being gated by the same optical frequency comb signal, that is, the detection optical signal and the reference optical signal are both optical frequency comb signals. The detection optical signal is used for measuring the space distance of the link to be measured, and the reference optical signal is used as a reference. In the step, the detection optical signal and the reference optical signal are acquired, and the optical signal generated before measurement can be directly acquired, or the optical signal can be generated.
For the method of generating an optical signal at the time of measurement, in one embodiment, step S1 specifically includes:
s11, gating the optical frequency comb signals locked by the repetition frequency;
s12, dividing the optical frequency comb signal after gating into a reference optical signal and a detection optical signal.
The above-mentioned, at first, carry out the repetition frequency locking to the optical frequency comb signal, the repetition frequency locking is mainly in order to carry out accurate control to the repetition frequency of optical frequency comb signal, makes it keep stable unchanged. And then selecting and activating a specific signal from the optical frequency comb signals after the repetition frequency locking. And finally dividing the gated signal into two paths of optical signals, namely a reference optical signal and a detection optical signal.
S2, measuring the space distance of the link to be measured by using the detection light signal to obtain a detection echo light signal.
The above-mentioned detection optical signal is mainly used for measuring the space distance of the link to be measured, and the detection echo optical signal is obtained after measurement, and the detection echo optical signal has the time delay information introduced by the space link to be measured.
S3, double-sideband intensity modulation is carried out on the reference optical signal and the detection echo optical signal by utilizing the single-frequency microwave signal.
And respectively performing double-sideband intensity modulation on the reference optical signal and the detection echo optical signal to obtain a modulated reference optical signal and a modulated detection echo optical signal. When intensity modulation is performed, the higher the frequency of the single-frequency microwave signal is, the higher the accuracy of the measurement result is, so that the single-frequency microwave signal with high frequency can be selected to perform double-sideband intensity modulation on the reference optical signal and the detection echo optical signal. Preferably, the reference optical signal and the probe echo optical signal are optionally double sideband intensity modulated with a high frequency microwave signal of greater than 40 GHz.
S4, performing beat frequency processing on the modulated reference light signal and the detected echo light signal respectively to obtain a reference photocurrent signal and a detected echo photocurrent signal.
The above-mentioned, the reference optical signal is subjected to beat processing, the modulated reference optical signal is converted into the reference photocurrent signal, the probe echo optical signal is subjected to beat processing, and the probe echo optical signal is converted into the probe echo photocurrent signal.
S5, carrying out analog-to-digital conversion on the reference photocurrent signal and the detection echo photocurrent signal.
And performing analog-to-digital conversion on the reference photocurrent signal to obtain reference light data information, and performing analog-to-digital conversion on the detected echo photocurrent signal to obtain detected echo light data information.
S6, respectively calculating frequency components obtained by the beat frequency of the modulated reference light signal and the detected echo light signal in a digital domain.
The optical frequency comb signal has equidistant comb teeth, the comb teeth of the modulated optical signal are moved compared with those of the optical signal before modulation, so that the frequency component can be obtained according to the beat frequency between the comb teeth of the modulated optical signal and those of the optical signal before modulation, and the frequency component can be a plurality of frequency components.
To reduce computational pressure, embodiments of the present invention may select only two low frequency components, thereby reducing the hardware requirements of the photodetector and digital-to-analog converter during subsequent processing. Taking a comb tooth of a certain modulated optical signal as an example, two comb teeth of the modulated optical signal are adjacent to the comb tooth of the modulated optical signal, and beat frequencies are carried out on the comb tooth of the modulated optical signal and the comb teeth of the two adjacent modulated optical signals, so that two different low-frequency components in the photocurrent signal can be obtained.
In one embodiment, step S6 specifically includes:
the method comprises the steps of determining a first frequency component obtained by the minimum comb tooth space beat frequency of a modulated reference light signal and a reference light signal before modulation and a second frequency component obtained by the second small comb tooth space beat frequency in a digital domain, and determining a first frequency component obtained by the minimum comb tooth space beat frequency of a modulated detection echo light signal and a detection echo light signal before modulation and a second frequency component obtained by the second small comb tooth space beat frequency.
The above-mentioned, the reference optical signal is subjected to beat processing, the modulated reference optical signal is converted into the reference photocurrent signal, the probe echo optical signal is subjected to beat processing, and the probe echo optical signal is converted into the probe echo photocurrent signal. The two frequency components with the lowest frequency in the reference photocurrent signal are selected. The two lowest frequency components of the probe photocurrent are also selected, whereby the two frequency components of the reference light signal and the probe echo light signal are determined, respectively.
And S7, performing disambiguation on the phase difference between the corresponding frequency components of the reference photocurrent signal and the detected echo photocurrent signal by using a time phase combination method to obtain the accurate spatial distance of the link to be detected.
In general, the time delay of the reference link is subtracted from the time delay of the detection link to obtain the time delay of the detection light signal introduced by the space link to be detected, thereby further obtaining the distance of the space link to be detected. However, the time delay difference between the two is directly measured in the time domain, and because the time delay precision is not enough as rough time delay, the technical scheme disclosed by the invention utilizes a time phase method to deblur the phase difference of the corresponding frequency components of the detected echo photocurrent signal and the reference photocurrent signal, determine the accurate time delay and further calculate the distance of the space link to be measured.
In one embodiment, step S7 includes:
Calculating integer ambiguity corresponding to a phase difference between corresponding frequency components of the reference photocurrent signal and the detection echo photocurrent signal by using a time phase method;
utilizing integer ambiguity optimization to directly obtain a rough time delay from a time domain and indirectly characterize the link distance to be tested;
And calculating the accurate spatial distance of the link to be measured according to the accurate time delay.
If the reference photocurrent signal and the detected echo photocurrent signal both have two frequency components, two phase differences exist between the reference photocurrent signal and the detected echo photocurrent signal. The integer ambiguity corresponds to a phase difference between the respective frequency components of the reference photocurrent signal and the detected echo photocurrent signal. The purpose of the time phase method is to obtain more accurate integer ambiguity, and to obtain accurate integer ambiguity by obtaining more accurate coarse time delay using time delay information obtained from the time domain and phase information obtained from the frequency domain.
In one embodiment, calculating the integer ambiguity corresponding to the phase difference between the respective frequency components of the reference photocurrent signal and the detected echo photocurrent signal using a time phase method comprises:
A phase difference between the corresponding frequency components of the reference photocurrent signal and the probe echo photocurrent signal is extracted.
Optimizing a coarse time delay which is directly obtained from a time domain and can indirectly represent the link distance to be measured according to a phase difference between a time domain pulse number difference corresponding to the reference photocurrent signal and the detection echo photocurrent signal and a corresponding frequency component;
and obtaining the whole-cycle ambiguity according to the optimized rough time delay.
The rough time delay is introduced after the detection light signal is measured on the space link to be measured. If the reference photocurrent signal and the probe echo photocurrent signal both have two frequency components, the reference photocurrent signal has a first frequency component and a second frequency component, and the probe echo photocurrent signal has a first frequency component and a second frequency component. The difference in the number of pulses in the two time domains can be calculated in the time domain.
Illustratively, the steps include:
Extracting a first phase difference between a first frequency component of the reference optical signal and a first frequency component of the probe echo optical signal, and a second phase difference between a second frequency component of the reference optical signal and a second frequency component of the probe echo optical signal;
optimizing the rough time delay introduced by the link to be tested according to the time domain pulse number difference, the first phase difference and the second phase difference corresponding to the reference photocurrent signal and the detection echo light signal;
And optimizing the first integer ambiguity corresponding to the first phase difference according to the adjusted rough time delay.
In this example, the first integer ambiguity corresponds to the first phase difference, the first phase difference corresponds to the first frequency component, the frequency of the modulated signal corresponding to the first frequency component is relatively high, and the frequency of the modulated signal is proportional to the precision, so that the first integer ambiguity is selected to be optimized.
The principle of the technical scheme of the invention is further described in detail by the following specific examples:
An optical frequency comb signal E 0 (t) generated by an optical frequency comb source has the expression:
Wherein A n is the optical amplitude value of the nth optical frequency comb tooth signal. f ceo is the frequency offset of the optical frequency comb, and f rep is the repetition frequency of the optical frequency comb. And then performing time domain gating on the optical frequency comb signals, and dividing the optical frequency comb signals after gating into detection optical signals and reference optical signals. The detection optical signal is sent to a space link for ranging, so as to obtain a detection echo optical signal, and the expression of the detection echo optical signal can be written as follows:
where τ is the delay generated during ranging and α is the attenuation introduced by the spatial link.
And respectively performing double-sideband intensity modulation on the received reference optical signal and the detected echo optical signal by utilizing a single-frequency microwave signal with the frequency of f RF, wherein the expression of the detected echo optical signal is as follows:
Where M is the electro-optic modulation factor.
The reference optical signal and the detection echo optical signal enter a photoelectric detector to perform beat frequency processing, a direct current component is removed, and a low frequency component is taken, wherein the photocurrent corresponding to the detection echo optical signal is:
Wherein N 1 represents the number of comb teeth present in the range of the modulated signal f RF. Round (..) is defined as rounded off to rounded off symbols. The first term in equation (4) is the result of the beat frequency between the modulated signal and the original optical frequency comb signal nearest thereto (first frequency component), and the second term is the result of the beat frequency between the modulated signal and the original optical frequency comb signal nearest thereto (second frequency component).
Sending the beat frequency signal into an analog-to-digital converter, inputting the generated digital signal into a resolving module, extracting the phase difference between a reference link and a detection link corresponding to the two frequency components in the step (4)According to the characteristics of the optical frequency comb, the phase difference isThe phase difference between the reference link and the probe link corresponding to the signals with frequencies N 1frep and (N 1-1)frep) is equal, and the following expression can be obtained:
Wherein, will be Defined as a downward rounding symbol, N amb1 isCorresponding integer ambiguity, N amb2 isCorresponding integer ambiguity. The above formula (7) can be obtained according to the definition of the integer ambiguity, taking the first formula in the formula (6) as an example, taking the formula (7) into the formula (6), and uniformly rounding down the two sides of the formula:
Where Δτ is the oscilloscope's delay error, the above equation holds if and only if |Δτ| < 1/(2N 1frep). Because the time precision of the oscilloscope is limited, the requirements are difficult to meet, so that the precision of the rough time delay tau r is further improved by adopting time phase, and the combined type (6) can be obtained:
Wherein b=n amb1-Namb2, the difference value can be determined according to the number of time-domain pulses of the reference photocurrent signal corresponding to the reference light signal after gating and the detected echo photocurrent signal corresponding to the detected echo light signal. After time-domain gating, the time-domain waveform of the optical frequency comb signal can be expressed as:
Wherein n 0 is an optical frequency comb signal corresponding to a time-domain gating time, the pulse width of a en (t) is t wid, and a en (t) =0 when |t| > t wid/2. Then, using the obtained τ r, the accurate N amb1 is calculated:
Further, bringing N amb1 into the first equation in equation (6) can calculate the exact time delay τ:
Further, the distance of the spatial link to be measured can be calculated:
wherein round (..) is defined as rounding off a rounded symbol The method is defined as downward rounding symbols, d is the distance of a space link to be measured, c is the light speed, n air is the refractive index of air, and f RF is the frequency of the single-frequency microwave signal; A first phase difference between a reference path and a detection path corresponding to a signal obtained by beat frequency between the modulated signal and an original optical frequency comb signal nearest to the modulated signal; For modulating the second phase difference between the reference path and the detection path corresponding to the beat frequency obtained between the signal and the original optical frequency comb signal which is the second closest to the signal, N amb1 is The corresponding first integer ambiguity, N amb2 isF rep is the repetition frequency of the optical frequency comb.
On the other hand, as shown in fig. 2, based on the single optical frequency comb-assisted laser phase estimation method disclosed in the present invention, the single optical frequency comb-assisted laser phase estimation device provided in the present invention includes:
The signal acquisition module 201 is configured to acquire a detection light signal and a reference light signal corresponding to the detection light signal.
The measurement module 202 is configured to measure a spatial distance of the link to be measured by using the probe optical signal, and obtain a probe echo optical signal.
The intensity modulation module 203 is configured to perform double-sideband intensity modulation on the reference optical signal and the probe echo optical signal by using a single-frequency microwave signal.
The photoelectric conversion module 204 is configured to perform beat frequency processing on the modulated reference optical signal and the modulated detection echo optical signal, respectively, to obtain a reference photocurrent signal and a detection echo photocurrent signal.
The analog-to-digital conversion module 205 is configured to perform analog-to-digital conversion on the reference photocurrent signal and the detected echo photocurrent signal.
A resolving module 206 for respectively calculating frequency components of the modulated reference light signal and the detected echo light signal obtained by beat frequency in the digital domain, and
And the phase difference between the corresponding frequency components of the reference photocurrent signal and the detection echo photocurrent signal is deblurred by using a time phase method, so that the accurate spatial distance of the link to be detected is obtained.
The signal acquisition module 201 may be configured to directly collect the optical signal that has been generated before measurement, and may also be configured to generate an optical signal, where the detected optical signal and the reference signal are both optical frequency comb signals.
In one embodiment, the signal acquisition module 201 includes:
The optical frequency comb source is used for generating an optical frequency comb signal;
The optical switch is connected with the optical frequency comb source and is used for gating the optical frequency comb signal locked by the repetition frequency;
and the coupler is connected with the optical switch and is used for dividing the optical frequency comb signal after gating into a reference optical signal and a detection optical signal.
In one embodiment, the measurement module 202 includes a circulator and collimator and a mirror for measuring the spatial distance of the link under test.
In one embodiment, the intensity modulation module 203 double sideband intensity modulates the reference light signal and the probe echo light signal with a high frequency microwave signal greater than 40 GHz.
In one embodiment, the resolving module 206 includes:
the frequency component calculation module is used for calculating frequency components obtained by the beat frequency of the reference optical signal and the detection echo optical signal respectively;
And the defuzzification module is used for defuzzifying the phase difference between the corresponding frequency components of the reference photocurrent signal and the detected echo photocurrent signal by using a time phase method to obtain the accurate spatial distance of the link to be detected.
In one embodiment, in the resolving module 206, the frequency component calculating module is specifically configured to:
The method comprises the steps of determining a first frequency component obtained by the beat frequency between comb teeth with minimum space between a reference optical signal after modulation and a reference optical signal before modulation and a second frequency component obtained by the beat frequency between comb teeth with second small space between comb teeth in a digital domain, and determining a first frequency component obtained by the beat frequency between comb teeth with minimum space between a detection echo optical signal after modulation and a detection echo optical signal before modulation and a second frequency component obtained by the beat frequency between comb teeth with second small space between comb teeth.
In one embodiment, in the resolving module 206, the defuzzifying module includes:
The whole-cycle ambiguity calculating module is used for calculating the whole-cycle ambiguity corresponding to the phase difference between the corresponding frequency components of the reference photocurrent signal and the detected echo photocurrent signal by using a phase-time method;
the accurate time delay calculation module is used for calculating and detecting the accurate time delay introduced by the space link to be detected in the echo optical signal by using the integer ambiguity;
And the space distance calculation module is used for calculating the accurate space distance of the link to be measured according to the accurate time delay.
In one embodiment, the whole-cycle ambiguity calculation module is specifically configured to:
extracting a phase difference between frequency components corresponding to the reference photocurrent signal and the detection echo photocurrent signal;
Optimizing a coarse time delay which is directly obtained from a time domain and can indirectly represent the link distance to be measured according to a phase difference between a time domain pulse number difference corresponding to the reference photocurrent signal and the detection echo photocurrent signal and a corresponding frequency component;
And acquiring the whole-cycle ambiguity according to the optimized rough delay difference.
In one embodiment, the device disclosed in the embodiment of the present invention further includes:
The reference input end of the microwave source is connected with the optical frequency comb source and the optical switch, and the output end of the microwave source is connected with the intensity modulation module.
In one embodiment, time synchronization lock between the signal acquisition module 201, the microwave source, the analog-to-digital converter, and the resolution module 206 is used to ensure time synchronization between the signal acquisition module 201, the microwave source, the analog-to-digital converter, and the resolution module 206.
For easy understanding, the following detailed description of the technical solution of the present invention is provided by a specific embodiment in combination with the accompanying drawings:
As shown in FIG. 3, the single optical frequency comb-assisted laser phase distance estimation device of the embodiment comprises an optical frequency comb source, an optical switch, a coupler, a local vibration source, a single frequency microwave source, two intensity modulators, two photoelectric detectors, a two-channel analog-to-digital converter and a resolving module. The output end of the local oscillation source is connected with the optical frequency comb source, the optical switch, the microwave source, the analog-to-digital converter and the resolution module, and the local oscillation source is used for providing unified reference for the module connected with the local oscillation source. The output end of the optical frequency comb source is connected with an optical switch, the output end of the optical switch is connected with a coupler, the output end of the coupler is connected with a circulator and an intensity modulator, and the output end of the circulator is connected with another intensity modulator and a collimator. The output end of the microwave source is connected with the power divider, and the output end of the power divider is respectively connected with the two intensity modulators. The output ends of the two intensity modulators are respectively connected with the two photoelectric detection modules. The output ends of the two photoelectric detection modules are connected with the two-channel analog-to-digital converter, and the output ends of the analog-to-digital converter are connected with the input end of the resolving module.
The optical frequency comb source outputs continuous optical frequency comb signals, the repetition frequency of the continuous optical frequency comb signals is taken as a frequency reference by a local oscillator source with high stability, the repetition frequency locking of the optical frequency comb is realized, the generated signals are input into the coupler after being gated by the optical switch, one path of the signals is taken as a reference optical signal, and the other path of the signals is taken as a detection optical signal to enter the circulator and is measured on the space between the two paths of the signals through the collimator, so that detection echo optical signals are formed. And the reference optical signal and the detection echo optical signal carrying the space distance time delay information are respectively input into two intensity modulators, and the single-frequency microwave signal is utilized to carry out double-sideband intensity modulation on the two paths of optical frequency comb signals. The two photoelectric detectors respectively perform beat frequency processing on the reference light signal and the detection echo light signal to obtain two paths of photocurrent signals. The two paths of photocurrent signals are converted by a two-channel analog-to-digital converter, the phase difference and the gating time difference between the corresponding frequency components of the reference light signal and the detection echo light signal are solved in a digital domain, and the accurate spatial distance of the link to be detected is obtained by step-by-step calculation through a time phase method. The above process needs to lock the optical switch, the single-frequency microwave source, the resolving module, the analog-to-digital converter and the optical frequency comb source to ensure the synchronization of signals.
Claims (10)
1. A single optical frequency comb-assisted laser phase pitch estimation method is characterized by comprising the following steps:
acquiring a detection light signal and a reference light signal corresponding to the detection light signal, wherein the detection light signal and the reference light signal are optical frequency comb signals;
Measuring the space distance of the link to be measured by using the detection light signal to obtain a detection echo light signal;
performing double-sideband intensity modulation on the reference optical signal and the detection echo optical signal by using a single-frequency microwave signal;
performing beat frequency processing on the modulated reference light signal and the modulated detection echo light signal respectively to obtain a reference photocurrent signal and a detection echo photocurrent signal;
performing analog-to-digital conversion on the reference photocurrent signal and the detection echo photocurrent signal;
respectively calculating frequency components obtained by the beat frequency of the modulated reference light signal and the modulated detection echo light signal in a digital domain;
And the phase difference between the corresponding frequency components of the reference photocurrent signal and the detected echo photocurrent signal is deblurred by using a time phase method, so that the accurate spatial distance of the link to be detected is obtained.
2. The single optical frequency comb-assisted laser phase estimation method of claim 1, wherein the acquiring a probe optical signal and a reference optical signal corresponding to the probe optical signal comprises:
gating the optical frequency comb signals locked by the repetition frequency;
and dividing the optical frequency comb signal after gating into the reference optical signal and the detection optical signal.
3. The single optical frequency comb assisted laser phase pitch estimation method of claim 1, wherein double sideband intensity modulating the reference optical signal and the probe echo optical signal with a single frequency microwave signal comprises:
and performing double-sideband intensity modulation on the reference optical signal and the detection echo optical signal by using a high-frequency microwave signal of more than 40 GHz.
4. The single optical frequency comb-assisted laser phase estimation method according to claim 1, wherein the calculating frequency components of the modulated reference optical signal and the probe echo optical signal obtained by beat frequency in the digital domain includes:
Determining a first frequency component obtained by the comb tooth space beat frequency with the minimum distance between the reference optical signal and the reference optical signal after modulation and a second frequency component obtained by the comb tooth space second small beat frequency before modulation in a digital domain, and determining a first frequency component obtained by the comb tooth space beat frequency with the minimum distance between the detection echo optical signal and the detection echo optical signal after modulation and a second frequency component obtained by the comb tooth space second small beat frequency before modulation.
5. The single optical frequency comb-assisted laser phase estimation method according to claim 1, wherein the step of using a phase-shift method to deblur a phase difference between corresponding frequency components of the reference photocurrent signal and the probe echo photocurrent signal to obtain the accurate spatial distance of the link to be measured comprises:
Calculating integer ambiguity corresponding to a phase difference between corresponding frequency components of the reference photocurrent signal and the detection echo photocurrent signal by using a time phase method;
calculating the accurate time delay introduced by the space link to be tested by using the integer ambiguity;
and calculating the accurate spatial distance of the link to be measured according to the accurate time delay.
6. The single optical frequency comb assisted laser phase estimation method of claim 5 wherein said calculating a whole-cycle ambiguity corresponding to a phase difference between corresponding frequency components of said reference photocurrent signal and said probe echo photocurrent signal using a phase-time phase method comprises:
Extracting a phase difference between corresponding frequency components of the reference photocurrent signal and the detection echo photocurrent signal;
Optimizing a coarse time delay which is directly obtained from a time domain and can indirectly represent the link distance to be measured according to a phase difference between a time domain pulse number difference corresponding to the reference photocurrent signal and the detection echo photocurrent signal and a corresponding frequency component;
and acquiring the integer ambiguity according to the optimized rough time delay.
7. A single optical frequency comb-assisted laser phase pitch estimation device, comprising:
The signal acquisition module is used for acquiring a detection light signal and a reference light signal corresponding to the detection light signal, wherein the detection light signal and the reference light signal are optical frequency comb signals;
the measuring module is used for measuring the space distance of the link to be measured by utilizing the detection light signal to obtain a detection echo light signal;
the intensity modulation module is used for carrying out double-sideband intensity modulation on the reference optical signal and the detection echo optical signal by utilizing a single-frequency microwave signal;
the photoelectric conversion module is used for performing beat frequency processing on the modulated reference light signal and the modulated detection echo light signal respectively to obtain a reference photocurrent signal and a detection echo photocurrent signal;
The analog-to-digital conversion module is used for performing analog-to-digital conversion on the reference photocurrent signal and the detection echo photocurrent signal;
A resolving module for respectively calculating frequency components obtained by the beat frequency of the modulated reference light signal and the detected echo light signal in a digital domain, and
And the phase difference between the corresponding frequency components of the reference photocurrent signal and the detected echo photocurrent signal is deblurred by using a time phase method, so that the accurate spatial distance of the link to be detected is obtained.
8. The single optical frequency comb-assisted laser phase pitch device of claim 7, wherein the signal acquisition module comprises:
The optical frequency comb source is used for generating an optical frequency comb signal;
the optical switch is connected with the optical frequency comb and is used for gating the optical frequency comb signal locked by the repetition frequency;
and the coupler is connected with the optical switch and is used for dividing the optical frequency comb signal after gating into the reference optical signal and the detection optical signal.
9. The single optical frequency comb aided laser phase pitch device of claim 8 further comprising a microwave source, a reference input of said microwave source being connected to said optical frequency comb source and said optical switch, an output of said microwave source being connected to said intensity modulation module.
10. The single optical frequency comb aided laser phase pitch estimation device of claim 9, wherein time synchronization lock between said signal acquisition module, said microwave source, said analog to digital conversion module, and said resolution module.
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