CN113156449A - Large-size rapid high-precision distance measuring method based on electro-optical modulation three-optical comb - Google Patents
Large-size rapid high-precision distance measuring method based on electro-optical modulation three-optical comb Download PDFInfo
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- 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
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- G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
Abstract
The invention relates to a large-size rapid high-precision distance measuring method. The method uses a three-optical frequency comb interferometric ranging method. On the basis of the distance measurement by the double-optical frequency comb interference method, the non-fuzzy distance of the three-optical comb interference distance measurement method is expanded from centimeter magnitude to hundred meter magnitude, and the problem of high distance prejudgment precision requirement in large-size distance measurement is solved. Meanwhile, the method keeps the distance measurement precision and the updating rate of the distance measurement by the double-optical frequency comb interference method, the distance updating rate reaches the MHz magnitude, and the method is more suitable for large-size high-precision distance measurement in the range of hundreds of meters to kilometers. The method can be applied to the fields of intelligent weapons, satellite formation flight, large military aircraft assembly and the like.
Description
The technical field is as follows:
the invention relates to a distance measuring method, in particular to a large-size rapid high-precision distance measuring method based on an electro-optical modulation three-optical comb.
Background art:
the precise measurement of large-size distances plays a crucial role in the scientific research and industrial fields. For example, a new generation of smart weapons relies on target tracking and aiming, and high-precision distance measurement in the range of hundreds of meters to kilometers is a precondition for the smart weapons to achieve target tracking and aiming. The synthetic aperture space detector based on the flight of the formation of the satellite needs to keep and control the formation of the constellation, and realizes the relative navigation among the constellation. And the relative navigation among the constellation needs to realize real-time and high-precision distance measurement and precise clock synchronization through a space communication network. In general, the sub-satellite spacing is on the order of kilometers, and the distance measurement accuracy is kept at micron or even sub-micron measurement accuracy.
Under the background of rapid development of the optical frequency comb technology, the distance measurement interferometry based on the dual-optical frequency comb has attracted extensive attention by people due to the advantages of high updating rate and high measurement precision. According to the method, two optical frequency combs with a tiny repetition frequency difference are used as light sources, the asynchronous optical sampling process between the two optical frequency combs is utilized, the pulse phase carrying distance information is amplified, and the distance value to be measured is obtained after pulse phase accurate detection and a phase inversion algorithm. However, the unambiguous distance of this measurement method is inversely proportional to the repetition frequency of the optical frequency comb, and the higher the repetition frequency, the smaller the unambiguous distance. For example, with a 100MHz optical frequency comb, the unambiguous distance is 1.5 m; whereas with an optical frequency comb with a repetition frequency of 10GHz the unambiguous distance is only 15 mm. Therefore, in order to obtain an accurate value of the distance to be measured, a distance meter with measurement accuracy better than half of the non-fuzzy distance, such as 7.5mm, must be used for roughly measuring and estimating the distance to be measured in actual operation. The unambiguous range of the ranging device therefore directly affects the complexity of the ranging system. On the other hand, the update rate of the ranging system is proportional to the difference in the repetition frequencies of the dual optical frequency combs. Generally, the higher the repetition frequency of the optical frequency comb, the larger the difference in repetition frequency, and the faster the update rate of the ranging system. Simply pursuing a long unambiguous distance and reducing the repetition frequency of the optical frequency comb results in a system update rate that is too low to meet the real-time measurement requirements. Therefore, the method for measuring the distance with the long non-fuzzy distance and the fast updating rate has urgent requirements and application value.
In order to solve the difficulties, the invention provides a large-size distance precision measurement method based on an electro-optical modulation three-optical comb. The method can make up for the defect that a large non-fuzzy distance and a high updating rate cannot be obtained simultaneously in the double-optical-comb distance measurement method, and has the same measurement precision as the double-optical-comb distance measurement method. The method is more suitable for large-size high-precision distance measurement in the range of hectometer to kilometer, the updating rate reaches MHz magnitude, and the method can be applied to the fields of intelligent weapons, satellite formation flight and the like.
The invention content is as follows:
the invention provides a large-size rapid high-precision distance measuring method based on an electro-optical modulation three-optical comb. The electro-optical modulation three-optical comb can be decomposed into two double-optical comb distance measuring devices, and the non-fuzzy distance expansion of the three-optical comb distance measuring method is realized through the superposition calculation of the non-fuzzy distance between the two double-optical combs. The method has the advantages of long non-fuzzy distance, high updating rate and high measurement precision, solves the problem of high distance prejudging precision requirement in large-size distance measurement, and is more suitable for kilometer-scale distance measurement.
The invention is implemented by the following technical scheme: a large-size rapid high-precision distance measuring method based on an electro-optical modulation three-optical comb comprises an electro-optical modulation three-optical comb light source part and a large-size rapid high-precision distance measuring part; the electro-optical modulation three-optical comb part comprises a continuous wave laser, an electro-optical modulator and a signal generator, wherein the electro-optical modulator modulates the continuous wave laser and can generate an electro-optical modulation optical frequency comb, the repetition frequency of the electro-optical modulation optical frequency comb is equal to the driving frequency of the electro-optical modulator, the driving frequency of the electro-optical modulator is the output frequency of the signal generator for driving the electro-optical modulator, and the electro-optical modulation three-optical comb has a tiny repetition frequency difference;
the large-size rapid high-precision distance measuring part consists of a reference mirror, a target mirror, a light beam combiner, a photoelectric detector and a data processing module; the relative position between the reference mirror and the target mirror provides information of the distance to be measured, the optical beam combiner completes the asynchronous sampling process between the three optical combs, and the photoelectric detector and the data processing module complete the detection and calculation of the distance signal to finally obtain the information of the distance to be measured.
Optimally: the electro-optical modulation three-optical comb part comprises a continuous wave laser, a first electro-optical modulator, a second electro-optical modulator, a first signal generator and a second signal generator; the first electro-optical modulator is connected with the first signal generator at the same time to form an electro-optical modulation double-signal optical comb, and the second electro-optical modulator is connected with the second signal generator to form an electro-optical modulation local oscillator optical comb.
Optimally: the electro-optical modulation three-optical comb is generated as follows: setting the frequency of the output signal of the first signal generator to be periodically switched between two values, wherein the frequency of the periodic switching is f. Thus, the frequency of the signal loaded on the electro-optical modulator is periodically switched between two frequency values; thus, the repetition frequency of the optical frequency comb generated after the continuous wave laser passes through the electro-optical modulator shows periodic variation, which is respectively marked as frep1And frep2(ii) a Wherein f isrep1For the frequency of the output signal of the first signal generator in the first half-cycle, frep2The frequency of the output signal for the first signal generator in the last half cycle;
secondly, after beam splitting by the optical fiber beam splitter, delaying one path of split optical signals by the optical fiber delay line by one half of a rectangular wave period;
thirdly, after passing through the optical fiber beam combiner, the single optical frequency comb with the periodically changed repetition frequency is changed into an electro-optical modulation double-optical comb with a tiny repetition frequency difference to be used as a double-signal optical comb;
fourthly, additionally arranging an electro-optical modulation single optical comb as a local oscillator optical comb, and recording the repetition frequency of the electro-optical modulation single local oscillator optical comb as frep3(ii) a The repetition frequencies of the electro-optical modulation double-signal optical comb and the electro-optical modulation single-local-oscillator optical comb are different, namely frep1≠frep2≠frep3。
Optimally: the first signal generator, the second signal generator and the third signal generator trace to the same rubidium atomic clock, so that the stability of the electro-optical modulation double-signal optical comb and the stability of the electro-optical modulation single-local-oscillator optical comb can be improved.
Optimally: the electro-optical modulation three optical combs are all from the same continuous wave laser.
Optimally: the electro-optical modulation dual-signal optical comb is divided into reference light and measuring light after beam splitting, and the light intensity of the reference light and the light intensity of the measuring light can be adjusted according to the requirement; the reference light is reflected by a reference mirror and then is combined with the electro-optical modulation single local oscillator light comb through a spatial light beam splitter; measuring light is combined with the single local oscillator light of the electro-optical modulation after being reflected by a target mirror; adjusting the polarization states of the reference light and the measuring light to be consistent with the polarization state of the electro-optical modulation single local oscillator optical comb, and generating interference; the interference signal is detected by a photoelectric detector and then data processing is carried out; and the data processing module is used for solving the relative distance between the reference mirror and the target mirror.
Optimally: the repetition frequencies in the electro-optical modulation dual-signal optical comb are respectively frep1And frep2The two optical frequency combs are reflected by the reference mirror and the target mirror, so that the electro-optic modulation dual-signal optical frequency combs contain distance information between the reference mirror and the target mirror; after the electro-optical modulation double-signal optical frequency comb and the electro-optical modulation single-local-oscillator optical comb are combined, the phase of an interference signal between the electro-optical modulation double-signal optical frequency comb and the electro-optical modulation single-local-oscillator optical comb reflects the distance between the reference mirror and the measuring mirror, and the distance between the reference mirror and the measuring mirror can be obtained through back calculation of phase information.
Optimally: the repetition frequency is frep1A set of double-optical frequency comb distance measuring system can be formed between the signal optical frequency comb and the electro-optical modulation single local oscillator optical comb; the distance between the reference mirror and the target mirror is expressed as
Wherein N is an integer, c is the speed of light, and N is the repetition frequency frep1The order of the composite wavelength formed by the combination of the different frequency components of the signal optical frequency comb,
the phase difference between the reference light and the measuring light under the n-order synthetic wavelength;
for the repetition frequency to be frep1The signal optical frequency comb and the measured non-fuzzy distance value n which can be reached by the electro-optical modulation single local oscillator optical comb distance measurementgIs the refractive index of air.
Optimally: the repetition frequency is frep2A second set of double-optical-comb distance measuring system can be formed between the signal optical frequency comb and the electro-optical modulation single local oscillator optical comb; the distance between the reference mirror and the target mirror can be expressed as
Wherein N is an integer, c is the speed of light, and m is the repetition frequency frep2The order of the composite wavelength formed by the combination of the different frequency components of the signal optical frequency comb,
the phase difference between the reference light and the measuring light under the m-order synthetic wavelength;
for the repetition frequency to be frep2The signal optical frequency comb and the measured non-fuzzy distance value which can be reached by the distance measurement of the electro-optical modulation single local oscillator optical comb; n isgIs the refractive index of air.
Optimally: the electro-optical modulation dual-signal optical comb has different repetition frequencies frep1And frep2Therefore, the electro-optical modulation double-signal optical comb and the electro-optical modulation single-local-oscillator optical comb have different non-fuzzy distances L during rangingNAR1And LNAR2(ii) a The unambiguous range of the ranging system can be extended to
Compared with the prior art, the invention has the following advantages:
1. the electro-optical modulator is used for realizing the generation of the double-signal optical comb, simplifying the light source structure and reducing the cost of the whole experimental equipment.
2. The electro-optical modulation double-signal optical comb and the electro-optical modulation single-local-oscillator optical comb are derived from the same light source, so that the electro-optical modulation double-signal optical comb and the electro-optical modulation single-local-oscillator optical comb have higher coherence, and meanwhile, the system structure is simpler.
3. The electro-optical modulation double-signal optical comb and the electro-optical modulation single-local-oscillator optical comb have extremely high stability.
4. The rubidium atomic clock can be replaced by a hydrogen atomic clock, so that the stability of the electro-optical modulation double-signal optical comb and the stability of the electro-optical modulation single-local-oscillator optical comb are further improved.
5. Simplify the range finding space light path, improve range finding system's integrability.
Drawings
FIG. 1 is a flow chart of an embodiment of the present invention;
fig. 2 is a large-size fast high-precision distance measuring device based on an electro-optical modulation three-optical comb in the embodiment of the present invention.
Wherein: 1-a continuous wave laser; 2-a first fiber splitter; 3-a first electro-optical modulator; 4-a second electro-optic modulator; 5-rubidium atomic clock; 6-a first signal generator; 7-a second signal generator; 8-a second fiber splitter; 9-a fiber delay line; 10-an optical fiber combiner; 11-a first collimator; 12-a first half wave plate; 13-a reference mirror; 14-a first quarter wave plate; 15-a second quarter wave plate; 16-a target lens; 17-a first polarizing beam splitter; 18-a second collimator; 19-a second half-wave plate; 20-a spatial beam splitter; 21-a mirror; 22-a second polarizing beam splitter; 23-a first photodetector; 24-a second photodetector; 25-a data processing module; 26-third half-wave plate.
Detailed Description
The invention is further illustrated with reference to the following examples and figures, without thereby limiting the scope of the invention.
The invention provides a large-size rapid high-precision distance measuring method based on an electro-optical modulation three-optical comb. The method for implementing the method is shown in the figure 1 and the figure 2. The distance information to be measured is loaded on the electro-optical modulation signal optical comb 1 and the electro-optical modulation signal optical comb 2. And the electro-optical modulation local oscillator optical comb and the electro-optical modulation signal optical combs 1 and 2 enter an interference optical path after being combined. And finally, obtaining the true value of the distance to be measured through data processing.
The present invention will be further described with reference to specific embodiments thereof. The invention provides a large-size rapid high-precision distance measuring method based on an electro-optical modulation three-optical comb. The electro-optical modulation three-optical-comb part consists of an electro-optical modulation double-signal optical comb and an electro-optical modulation single-local-oscillator optical comb. Wherein, the two signal optical combs of electro-optical modulation include: the device comprises a continuous wave laser 1, a first optical fiber beam splitter 2, a first electro-optical modulator 3, a rubidium atomic clock 5, a first signal generator 6, a second optical fiber beam splitter 8, an optical fiber delay line 9 and an optical fiber beam combiner 10. The single local oscillator optical comb of electro-optical modulation includes: a second electro-optical modulator 4, a second signal generator 7. The large-size fast high-precision distance measuring section includes: the device comprises a first collimator 11, a first half-wave plate 12, a reference mirror 13, a first quarter-wave plate 14, a second quarter-wave plate 15, a target mirror 16, a first polarization beam splitter 17, a second collimator mirror 18, a second half-wave plate 19, a spatial light beam splitter 20, a reflector 21, a second polarization beam splitter 22, a first photodetector 23, a second photodetector 24, a data processing module 25 and a third half-wave plate 26.
The electro-optical modulation double-signal optical comb is generated as follows: after the output signal of the continuous wave laser is subjected to electro-optic modulation, an optical frequency comb with the repetition frequency being the electro-optic modulation frequency is generated. Therefore, the frequency of the output signal of the first signal generator is set to be periodically switched, so that the frequency of the signal applied to the first electro-optical modulator 3 is periodically switched. Thus, the repetition frequency of the output optical frequency comb of the continuous wave laser 1 after passing through the first electro-optical modulator 3 exhibits a periodic variation, respectively denoted as frep1And frep2. Wherein f isrep1For the frequency, f, of the output signal of the first signal generator 6 in the first half cyclerep2The frequency of the output signal for the second half cycle of the first signal generator 6. After being split by the second optical fiber beam splitter 8, the optical fiber delay line 9 delays one path of split optical signals by one halfThe period of the square wave. After passing through the optical fiber combiner 10, the single optical frequency comb with the periodically changing repetition frequency becomes an electro-optical modulation dual-signal optical comb.
The production process of the electro-optical modulation single local oscillator optical comb comprises the following steps: and modulating the output optical signal of the continuous wave laser by using a second electro-optical modulator 4, and outputting an electro-optical modulation single local oscillator optical comb. Wherein, the modulation signal of the second electro-optical modulator 4 is the output signal of the second signal generator 7. Recording the repetition frequency of the single local oscillator optical comb of the electro-optical modulation as frep3I.e. the frequency of the output signal of the second signal generator 7.
Specifically, the repetition frequencies of the electro-optical modulation dual-signal optical comb and the electro-optical modulation single-local-oscillator optical comb are different and slightly different, namely frep1≠frep2≠frep3. And the difference between the repetition frequencies of the electro-optical modulation double-signal optical comb and the electro-optical modulation single-local-oscillator optical comb is far smaller than the repetition frequency.
Specifically, the first electro-optical modulator 3 and the second electro-optical modulator 4 may be composed of an electro-optical phase modulator and an electro-optical intensity modulator, or may be composed of an electro-optical phase modulator and a mach-zehnder modulator. The specific implementation mode can be specifically set according to actual requirements, such as parameters of system power consumption, required optical comb spectral range, flatness and the like.
Preferably, a first optical fiber beam splitter 2 is used for splitting the output signal of the continuous wave laser 1, and the split signals are respectively used for a first electro-optical modulator 3 and a second electro-optical modulator 4 to generate the electro-optical modulation double-signal optical comb and the electro-optical modulation single-local-oscillator optical comb. The first optical fiber beam splitter 2 is arranged to enable the electro-optical modulation double-signal optical comb and the electro-optical modulation single-local-oscillator optical comb to be derived from the same light source, so that the electro-optical modulation double-signal optical comb and the electro-optical modulation single-local-oscillator optical comb have higher coherence, and meanwhile, the system structure is simpler.
Preferably, the first signal generator 6 and the second signal generator 7 are arranged to trace to the same rubidium atomic clock 5, so that the stability of the electro-optical modulation double-signal optical comb and the stability of the electro-optical modulation single-local-oscillator optical comb can be improved.
Preferably, the rubidium atomic clock can be replaced by a hydrogen atomic clock, so that the stability of the electro-optical modulation double-signal optical comb and the stability of the electro-optical modulation single-local-oscillator optical comb are further improved.
A large-size rapid high-precision distance measuring part: the electro-optical modulation double-signal optical comb is divided into reference light and measuring light after passing through the first half-wave plate 12 and the polarization beam splitter 17. The first half-wave plate 12 is used to adjust the splitting ratio of the reference light and the measurement light. Specifically, the optical power of the measuring light can be set to be higher than the reference light intensity, and the method is applied to the fields of non-cooperative target distance measurement and the like. Wherein, the reference light is reflected by the reference mirror 13 and then combined with the electro-optical modulation single local oscillator optical comb through the spatial light beam splitter 20; the measuring light is reflected by the target lens 16 and then is combined with the electro-optical modulation single local oscillation light by the spatial light beam splitter 20. The first quarter wave plate 14 and the second quarter wave plate 15 are used to adjust the polarization states of the reference light and the measurement light so that the reference light and the target light reflected by the reference mirror 13 and the target mirror 16 can completely pass through the first polarization beam splitter 17. The combined signal is split by the second polarization beam splitter 22 and enters the two photodetectors respectively. The third half-wave plate 26 is used for adjusting the polarization state of the reference light and the measurement light when the reference light and the measurement light interfere with the electro-optical modulation local oscillation optical comb. Finally, the data processing module 25 performs a calculation of the relative distance of the reference mirror 13 and the target mirror 16.
Specifically, the repetition frequencies in the electro-optical modulation dual-signal optical comb are respectively frep1And frep2The two optical frequency combs are reflected by the reference mirror and the target mirror after beam splitting. The electro-optically modulated dual signal optical frequency combs each contain information on the distance between the reference mirror and the target mirror. After the electro-optical modulation double-signal optical frequency comb and the electro-optical modulation single-local-oscillator optical comb are combined, the phase of an interference signal between the electro-optical modulation double-signal optical frequency comb and the electro-optical modulation single-local-oscillator optical comb reflects the distance between the reference mirror and the measuring mirror, and the distance between the reference mirror and the measuring mirror can be obtained through back calculation of phase information.
In particular, the repetition frequency is frep1A set of double-optical frequency comb distance measuring system can be formed between the signal optical frequency comb and the electro-optical modulation single local oscillator optical comb. The distance between the reference mirror 16 and the target mirror 19 is indicated as
Wherein N is an integer, c is the speed of light, and N is the repetition frequency frep1The order of the composite wavelength formed by the combination of the different frequency components of the signal optical frequency comb,
is the phase difference between the reference light and the measuring light at the n-order synthesized wavelength.
For the repetition frequency to be frep1The signal optical frequency comb and the measurement non-fuzzy distance value which can be reached by the electro-optical modulation single local oscillator optical comb distance measurement. n isgIs the refractive index of air.
In particular, the repetition frequency is frep2The second set of double optical comb distance measuring system can be formed between the signal optical frequency comb and the electro-optical modulation single local oscillator optical comb. The distance between the reference mirror and the target mirror can be expressed as
Wherein M is an integer, c is the speed of light, and M is the repetition frequency frep2The order of the composite wavelength formed by the combination of the different frequency components of the signal optical frequency comb,
is the phase difference between the reference light and the measuring light at the m-order synthesized wavelength.
For the repetition frequency to be frep2The signal optical frequency comb and the measurement non-fuzzy distance value which can be reached by the electro-optical modulation single local oscillator optical comb distance measurement. n isgIs the refractive index of air.
Further, the electro-optical modulation dual-signal optical comb has different repetition frequencies frep1And frep2Thus, the electro-optically modulated dual-signal optical comb andwhen the electro-optical modulation single local oscillator optical comb is used for ranging, different non-fuzzy distances are provided
And LNAR2. Finally, the unambiguous range of the ranging system can be extended to
Specifically, the distance update rate of the ranging system is determined by a repetition frequency difference between the electro-optical modulation dual-signal optical comb and the electro-optical modulation single local oscillator optical comb.
Specifically, the repetition frequency of the electro-optical modulation dual-signal optical comb and the electro-optical modulation single-local-oscillator optical comb can be specifically set according to actual conditions. For example, f can be setrep1＝10GHz，frep2＝10.001GHz，frep310.0003 GHz. The unambiguous distance is
The distance updating rate can reach the MHz magnitude at most. The measurement precision can reach micron or even submicron level. Therefore, after the non-fuzzy distance expansion, the distance measuring system can be suitable for large-size, high-precision and quick distance measurement and other applications.
Further, the first polarization beam splitter 20 may be replaced by an optical fiber device, which simplifies the distance measurement spatial light path and improves the integratability of the distance measurement system.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The large-size rapid high-precision distance measuring method based on the electro-optical modulation three-optical comb is characterized by comprising the following steps of: the device comprises an electro-optical modulation three-optical-comb light source part and a large-size rapid high-precision distance measuring part; the electro-optical modulation three-optical comb part comprises a continuous wave laser, an electro-optical modulator and a signal generator, wherein the electro-optical modulator modulates the continuous wave laser and can generate an electro-optical modulation optical frequency comb, the repetition frequency of the electro-optical modulation optical frequency comb is equal to the driving frequency of the electro-optical modulator, the driving frequency of the electro-optical modulator is the output frequency of the signal generator for driving the electro-optical modulator, and the electro-optical modulation three-optical comb has a tiny repetition frequency difference;
the large-size rapid high-precision distance measuring part consists of a reference mirror, a target mirror, a light beam combiner, a photoelectric detector and a data processing module; the relative position between the reference mirror and the target mirror provides information of the distance to be measured, the optical beam combiner completes the asynchronous sampling process between the three optical combs, and the photoelectric detector and the data processing module complete the detection and calculation of the distance signal to finally obtain the information of the distance to be measured.
2. The distance measuring method according to claim 1, characterized in that: the electro-optical modulation three-optical comb part comprises a continuous wave laser, a first electro-optical modulator, a second electro-optical modulator, a first signal generator and a second signal generator; the first electro-optical modulator is connected with the first signal generator to form an electro-optical modulation double-signal optical comb, and the second electro-optical modulator is connected with the third signal generator to form an electro-optical modulation local oscillator optical comb.
3. The distance measuring method according to claim 2, characterized in that: the electro-optical modulation three-optical comb is generated as follows: setting the frequency of an output signal of a first signal generator to be periodically switched between two values, wherein the frequency of the periodic switching is f; thus, the repetition frequency of the optical frequency comb generated after the continuous wave laser passes through the electro-optical modulator shows periodic variation, which is respectively marked as frep1And frep2(ii) a Wherein f isrep1For the frequency of the output signal of the first signal generator in the first half-cycle, frep2Is a first signal generatorThe frequency of the output signal in the last half cycle;
secondly, after beam splitting by the optical fiber beam splitter, delaying one path of split optical signals by one half f by the optical fiber delay line;
thirdly, after passing through the optical fiber beam combiner, the single optical frequency comb with the periodically changed repetition frequency is changed into an electro-optical modulation double-optical comb with a tiny repetition frequency difference to be used as a double-signal optical comb;
fourthly, additionally arranging an electro-optical modulation single optical comb as a local oscillator optical comb, and recording the repetition frequency of the electro-optical modulation single local oscillator optical comb as frep3(ii) a The repetition frequencies of the electro-optical modulation double-signal optical comb and the electro-optical modulation single-local-oscillator optical comb are different, namely frep1≠frep2≠frep3。
4. The distance measuring method according to claim 2, characterized in that: the first signal generator and the second signal generator trace to the same rubidium atomic clock, so that the stability of the electro-optical modulation double-signal optical comb and the stability of the electro-optical modulation single-local-oscillator optical comb can be improved.
5. The distance measuring method as set forth in claim 2, wherein: the electro-optical modulation three optical combs are all from the same continuous wave laser.
6. The distance measuring method according to claim 1, characterized in that: the electro-optical modulation dual-signal optical comb is divided into reference light and measuring light after beam splitting, and the light intensity of the reference light and the light intensity of the measuring light can be adjusted according to the requirement; the reference light is reflected by a reference mirror and then is combined with the electro-optical modulation single local oscillator light comb through a spatial light beam splitter; measuring light is combined with the single local oscillator light of the electro-optical modulation after being reflected by a target mirror; adjusting the polarization states of the reference light and the measuring light to be consistent with the polarization state of the electro-optical modulation single local oscillator optical comb, and generating interference; the interference signal is detected by a photoelectric detector and then data processing is carried out; and the data processing module is used for solving the relative distance between the reference mirror and the target mirror.
7. The method of claim 6The distance measuring method is characterized in that: the repetition frequencies in the electro-optical modulation dual-signal optical comb are respectively frep1And frep2The two optical frequency combs are reflected by the reference mirror and the target mirror, so that the electro-optic modulation dual-signal optical frequency combs contain distance information between the reference mirror and the target mirror; after the electro-optical modulation double-signal optical frequency comb and the electro-optical modulation single-local-oscillator optical comb are combined, the phase of an interference signal between the electro-optical modulation double-signal optical frequency comb and the electro-optical modulation single-local-oscillator optical comb reflects the distance between the reference mirror and the measuring mirror, and the distance between the reference mirror and the measuring mirror can be obtained through back calculation of phase information.
8. The distance measuring method according to claim 7, characterized in that: the repetition frequency is frep1A set of double-optical frequency comb distance measuring system can be formed between the signal optical frequency comb and the electro-optical modulation single local oscillator optical comb; the distance between the reference mirror and the target mirror is expressed as
Wherein N is an integer, c is the speed of light, and N is the repetition frequency frep1The order of the synthetic wavelength formed by combining different frequency components of the signal optical frequency comb is the phase difference between the reference light and the measuring light under the n-order synthetic wavelength;
for the repetition frequency to be frep1The signal optical frequency comb and the measured non-fuzzy distance value n which can be reached by the electro-optical modulation single local oscillator optical comb distance measurementgIs the refractive index of air.
9. The distance measuring method according to claim 7, characterized in that: the repetition frequency is frep2A second set of double-optical-comb distance measuring system can be formed between the signal optical frequency comb and the electro-optical modulation single local oscillator optical comb; the distance between the reference mirror and the target mirror can be expressed as
Wherein N is an integer, c is the speed of light, and m is the repetition frequency frep2The order of the synthetic wavelength formed by combining different frequency components of the signal optical frequency comb is the phase difference between the reference light and the measuring light under the m-order synthetic wavelength;
for the repetition frequency to be frep2The signal optical frequency comb and the measured non-fuzzy distance value which can be reached by the distance measurement of the electro-optical modulation single local oscillator optical comb; n isgIs the refractive index of air.
10. The distance measurement method according to any one of claims 7 to 9, characterized in that: the electro-optical modulation dual-signal optical comb has different repetition frequencies frep1And frep2Therefore, the electro-optical modulation double-signal optical comb and the electro-optical modulation single-local-oscillator optical comb have different non-fuzzy distances L during rangingNAR1And LNAR2(ii) a The unambiguous range of the ranging system can be extended to
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