All-fiber mirror-swept frequency interference ranging device and method based on wavelength division multiplexing

Abstract

All-fiber mirror swept-frequency interference ranging device and method based on wavelength division multiplexing, which relate to the technical field of absolute distance measurement. To solve the technical problems in the prior art that spectral aliasing, swept-frequency non-linearity, Doppler effect and chromatic dispersion mismatch occur in swept-frequency interference measurement work, and the measurement accuracy, measurement efficiency and reliability of the all-fiber mirror swept-frequency interference ranging system cannot be guaranteed, the technical solution provided by the present invention is: an all-fiber mirror swept-frequency interference ranging device based on wavelength division multiplexing, the device includes: a laser unit for outputting swept-frequency light; a measurement interferometer optical path for generating a measurement signal according to the swept-frequency light; an auxiliary interferometer optical path for generating an auxiliary signal according to the swept-frequency light; a gas chamber calibration optical path for calibrating the optical path of the auxiliary interferometer according to the swept-frequency light; a data acquisition and processing module for obtaining a ranging result according to the measurement signal, the auxiliary signal and the calibration signal. It is used in the work of all-fiber mirror swept-frequency interference ranging.

Description

Technical Field

[0001] It relates to the technical field of absolute distance measurement, and particularly relates to all-fiber mirror swept-frequency interference ranging based on wavelength division multiplexing. Background Art

[0002] Swept-frequency interference measurement is an absolute distance measurement method, which has the advantages of no ranging ambiguity, strong anti-interference ability, high ranging accuracy, and can be used for non-cooperative target measurement. It has gradually become an effective means for measuring the three-dimensional distance information of space targets. The research content of this ranging method mainly focuses on 4 key points, namely swept-frequency nonlinear correction, large swept-frequency range, chromatic dispersion mismatch compensation, and Doppler effect suppression.

[0003] Existing swept-frequency nonlinear correction methods mainly include two categories: the active correction method based on an optoelectronic phase-locked loop and the optical frequency resampling method. The active correction method based on an optoelectronic phase-locked loop has the problems of complex optoelectronic phase-locked loop structure, high implementation difficulty, and currently unable to achieve full swept-frequency range correction. The optical frequency resampling method can use a simple all-fiber optical path to realize real-time correction of swept-frequency nonlinearity in the full swept-frequency range and can be used for non-cooperative target measurement.

[0004] To improve the measurement resolution, increasing the swept-frequency range of a tunable laser is a direct and effective means. However, when the swept-frequency range or the measurement distance is too large, chromatic dispersion mismatch will cause the target spectrum to broaden, resulting in a decrease in measurement resolution. Currently, there are two solutions to chromatic dispersion mismatch. The first is to introduce a dispersion compensation medium, but this method usually cannot accurately compensate for the influence of chromatic dispersion mismatch. The other is to iteratively compensate for the second-order term of chromatic dispersion mismatch existing in the measurement signal through an algorithm. Because iterative operations are required, it is not conducive to fast measurement.

[0005] The Doppler effect introduced by target movement will lead to the deterioration of the swept-frequency interference measurement accuracy. To eliminate the influence of the Doppler effect, the first is to eliminate the Doppler effect by measuring the signal frequency difference generated by a triangular wave modulated light source. This method requires the target movement speed to remain unchanged within a complete swept-frequency period, and the measurement effect on rapidly changing targets is not good. The second is to use the signal generated by a mirror swept-frequency light source to eliminate the Doppler effect. This method requires setting the two light sources to different swept-frequency rates or using orthogonal polarization beam splitting to separate the two signals. Among them, setting the light sources to different swept-frequency rates will introduce chromatic dispersion mismatch in the measurement signal. In orthogonal polarization beam splitting, using a fiber polarization beam splitter (fiber PBS, extinction ratio 22 dB) will cause crosstalk between the two signals. Although using a prism PBS can reduce the crosstalk influence, it will increase the system volume and the calibration difficulty. In addition, the nonlinear correction process of the above mirror swept-frequency scheme has the problem of low efficiency and is difficult to achieve fast measurement. Summary of the Invention

[0006] To solve the technical problems in the prior art that spectral aliasing, frequency-sweeping non-linearity, Doppler effect, chromatic dispersion mismatch, and low measurement efficiency occur in frequency-sweeping interference measurement, and the measurement accuracy and reliability of the all-fiber mirror frequency-sweeping interference ranging system cannot be guaranteed, the technical solution provided by the present invention is as follows:

[0007] An all-fiber mirror frequency-sweeping interference ranging device based on wavelength division multiplexing, the device comprising:

[0008] A laser unit for outputting frequency-swept light;

[0009] A measurement interferometer optical path for generating a measurement signal according to the frequency-swept light;

[0010] An auxiliary interferometer optical path for generating an auxiliary signal according to the frequency-swept light;

[0011] An air chamber calibration optical path for calibrating the optical path of the auxiliary interferometer according to the frequency-swept light;

[0012] A data acquisition and processing module for obtaining a ranging result according to the measurement signal, the auxiliary signal, and the calibration signal.

[0013] Further, a preferred embodiment is provided, wherein the measurement interferometer optical path comprises two optical paths of unequal lengths, and the measurement signal is obtained by detecting the interference information of the measurement light reflected by the target and the reference light transmitted through the optical fiber.

[0014] Further, a preferred embodiment is provided, wherein the auxiliary interferometer optical path comprises two optical paths of unequal lengths, and the auxiliary signal is obtained by detecting the interference information of the measurement light transmitted through the long optical fiber and the reference light transmitted through the short optical fiber.

[0015] Further, a preferred embodiment is provided, wherein the air chamber calibration optical path and the auxiliary interferometer share part of the optical path through a circulator to calibrate the optical path of the auxiliary interferometer.

[0016] Further, a preferred embodiment is provided, wherein the measurement interferometer optical path comprises two balanced detectors for outputting the measurement signal, which are connected to the digital acquisition and processing module through a multiplier.

[0017] Further, a preferred embodiment is provided, wherein the auxiliary interferometer optical path comprises two balanced detectors for outputting the auxiliary signal, which are connected to the digital acquisition and processing module through a multiplier.

[0018] Based on the same inventive concept, the present invention also provides an all-fiber mirror frequency-sweeping interference ranging method based on wavelength division multiplexing, the method being implemented based on the device described above, and comprising:

[0019] Steps of collecting measurement signals, auxiliary signals, and calibration signals; steps of generating a reference signal, mixing and filtering the reference signal with the auxiliary signal to obtain a processed auxiliary signal; steps of performing mixing and filtering and phase demodulation on the processed auxiliary signal to obtain a step of correcting the phase of the interferometer signal; steps of mixing the measurement signal and using the corrected interferometer signal phase and calibration signal to obtain a ranging result.

[0020] Based on the same inventive concept, the present invention also provides a full-fiber mirror swept-frequency interference ranging method based on wavelength division multiplexing, which is implemented based on the described device and includes:

[0021] Steps of collecting measurement signals, auxiliary signals, and calibration signals; steps of generating a reference signal, performing mixing, filtering, and phase demodulation on the reference signal and the auxiliary signal to obtain a step of correcting the phase of the interferometer signal; steps of using the corrected interferometer signal phase and calibration signal to obtain a ranging result according to the measurement signal.

[0022] Based on the same inventive concept, the present invention also provides a computer storage medium for storing a computer program, which implements the described method when the computer program is read by a computer.

[0023] Based on the same inventive concept, the present invention also provides a computer including a processor and a storage medium, which implements the described method when the computer program stored in the storage medium is read by the processor.

[0024] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows:

[0025] The full-fiber mirror swept-frequency interference ranging device and method based on wavelength division multiplexing provided by the present invention adopt a mirror synchronous swept-frequency technology and use two swept-frequency lights with a mirror relationship for measurement. It makes full use of the effective bandwidth of the light source to solve the problem of spectral aliasing in multi-target measurement scenarios. Compared with the prior art, this method can more effectively separate and analyze the measurement signals of multiple targets to achieve high-precision distance measurement of multiple targets.

[0026] The full-fiber mirror swept-frequency interference ranging device and method based on wavelength division multiplexing provided by the present invention use a wavelength division multiplexer to combine and separate two swept-frequency lights. It effectively improves the dual-band isolation and avoids crosstalk between dual-band lights. Compared with the method of orthogonal polarization beam splitting, this method has a simpler structure and less crosstalk, improving the reliability and accuracy of measurement.

[0027] The all-fiber mirror-swept frequency interference ranging device and method based on wavelength division multiplexing provided by the present invention adopt an all-fiber mirror-swept frequency structure, reducing the system volume, lowering the system complexity, and immune to the adverse effects of spectral broadening caused by the target Doppler effect and chromatic dispersion mismatch in a large swept frequency range. Compared with the traditional free-space optical path, the all-fiber structure is more compact and stable.

[0028] The all-fiber mirror-swept frequency interference ranging device and method based on wavelength division multiplexing provided by the present invention introduce a calibration optical path for the air chamber, and perform calibration through the absolute optical frequency and phase value of the absorption peak of the air chamber, ensuring the stability and reliability of the measurement system reference, and improving the measurement accuracy and long-term stability of the system.

[0029] The all-fiber mirror-swept frequency interference ranging device and method based on wavelength division multiplexing provided by the present invention use two different acquisition structures, and utilize the dual-reference frequency signal generated by the computer to quickly solve the phase of the auxiliary interferometer. The multi-target measurement and the number of data channels can be optimized according to requirements, improving the flexibility and adaptability of the system. In the signal processing part, while improving the measurement efficiency, high-precision measurement of the target is ensured.

[0030] The all-fiber mirror-swept frequency interference ranging device and method based on wavelength division multiplexing provided by the present invention are superior to the prior art in terms of reliability, system complexity, and processing efficiency, and have significant advantages especially in solving the problems of spectral aliasing, chromatic dispersion mismatch, and Doppler effect.

[0031] The all-fiber mirror-swept frequency interference ranging device and method based on wavelength division multiplexing provided by the present invention can be applied to the work of all-fiber mirror-swept frequency interference ranging. Description of the Drawings

[0032] Figure 1 It is a schematic diagram of Structure 1 of the all-fiber mirror-swept frequency interference ranging device based on wavelength division multiplexing;

[0033] Figure 2 It is a schematic diagram of Structure 2 of the all-fiber mirror-swept frequency interference ranging device based on wavelength division multiplexing;

[0034] Figure 3 For Figure 1 It is a flowchart of the implemented method;

[0035] Figure 4 For Figure 2 It is a flowchart of the implemented method;

[0036] Figure 5 It is the experimental result of absolute distance measurement. Among them, (a) is the schematic diagram of the distance spectrum of one measurement, and (b) is the measurement results of ten measurements. The repeatability of the ten measurement results is 3.9 μm.

[0037] Among them, 1 - the first tuning laser source, 2 - the second tuning laser source, 3 - the first isolator, 4 - the second isolator, 5 - the first coupler, 6 - the first wavelength division multiplexer, 7 - the second coupler, 8 - the third coupler, 9 - the first circulator, 10 - the optical system, 11 - the target, 12 - the fourth coupler, 13 - the second wavelength division multiplexer, 14 - the third wavelength division multiplexer, 15 - the first balanced detector, 16 - the second balanced detector, 17 - the fifth coupler, 18 - the sixth coupler, 19 - the second circulator, 20 - the fourth wavelength division multiplexer, 21 - the fifth wavelength division multiplexer, 22 - the third balanced detector, 23 - the fourth balanced detector, 24 - the first detector, 25 - the gas cell, 26 - the seventh coupler, 27 - the second detector, 28 - the data acquisition and data processing module, 29 - the first multiplier, 30 - the second multiplier. Detailed implementation mode

[0038] To make the advantages and beneficial effects of the technical solution provided by the present invention more clearly reflected, the technical solution provided by the present invention will now be further described in detail with reference to the accompanying drawings. Specifically:

[0039] Embodiment 1. This embodiment provides an all-fiber mirror swept-frequency interference ranging device based on wavelength division multiplexing. The device includes:

[0040] The laser unit is used to output swept-frequency light.

[0041] The measurement interferometer optical path is used to generate a measurement signal according to the swept-frequency light.

[0042] The auxiliary interferometer optical path is used to generate an auxiliary signal according to the swept-frequency light.

[0043] The gas cell calibration optical path is used to calibrate the optical path of the auxiliary interferometer according to the swept-frequency light.

[0044] The data acquisition and processing module is used to obtain the ranging result according to the measurement signal, auxiliary signal and calibration signal.

[0045] Specifically,

[0046] The all-fiber mirror swept-frequency interference ranging device based on wavelength division multiplexing includes:

[0047] The laser unit (1), which includes the first tuning laser source 1 and the second tuning laser source 2, is used to output swept-frequency light with a mirror image of the swept-frequency range.

[0048] The measurement interferometer optical path (2) is used to generate a measurement signal.

[0049] The auxiliary interferometer optical path (3) is used to generate an auxiliary signal and realize measurement signal correction.

[0050] Air chamber calibration optical path (IV), which is used to calibrate the optical path of the auxiliary interferometer to ensure the accuracy of measurement;

[0051] Data acquisition module, which is used to acquire measurement signals, auxiliary signals and calibration signals;

[0052] Digital signal processing module, which is used to process and analyze the acquired signals.

[0053] Functions and interrelationships of each component

[0054] Laser unit (I):

[0055] It includes a first tunable laser source 1 and a second tunable laser source 2, which are used to output swept-frequency light.

[0056] After the swept-frequency light is combined by the wavelength division multiplexer, it enters the measurement interferometer optical path, the auxiliary interferometer optical path and the air chamber calibration optical path respectively.

[0057] Measurement interferometer optical path (II):

[0058] Receives the swept-frequency light from the laser unit and generates the measurement light and reference light of the measurement interferometer optical path.

[0059] The measurement light formed after being reflected by the target 11 irradiated by the optical system 10 interferes with the reference light transmitted by the optical fiber to generate a measurement signal.

[0060] The measurement signal is detected by the balanced detector.

[0061] Auxiliary interferometer optical path (III):

[0062] Similarly receives the swept-frequency light from the laser unit and generates the measurement light and reference light of the auxiliary interferometer optical path.

[0063] The measurement light and reference light transmitted through the long and short optical paths interfere to generate an auxiliary signal.

[0064] The auxiliary signal is detected by the balanced detector to assist in correcting the measurement signal.

[0065] Air chamber calibration optical path (IV):

[0066] Receives the swept-frequency light from the laser unit and is used to calibrate the absolute frequency of the light source.

[0067] Absorbs light of a specific wavelength through the air chamber to ensure accurate measurement of the absolute frequency of the swept-frequency light.

[0068] The calibration signal is detected by the detector and is used to calculate the optical path of the auxiliary interferometer.

[0069] Data acquisition module:

[0070] Collect signals from the optical path of the measurement interferometer, the optical path of the auxiliary interferometer, and the optical path for chamber calibration.

[0071] Transmit the signals to the digital signal processing module for further processing.

[0072] Digital signal processing module:

[0073] Analyze and process the collected measurement signals, auxiliary signals, and calibration signals.

[0074] Correct the errors caused by non-linearity and calculate the final ranging result.

[0075] Each component is connected in series and parallel through optical fibers and optical elements to form a complete measurement system, which cooperates with each other to complete the high-precision interference ranging task.

[0076] The swept-frequency light output by the laser unit is combined through a wavelength division multiplexer and then enters the optical path of the measurement interferometer and the optical path of the auxiliary interferometer respectively; the optical path of the measurement interferometer irradiates the target 11 through the optical system 10, and the measurement light reflected by the target 11 interferes with the reference light transmitted through another optical fiber to generate a measurement signal; the optical path of the auxiliary interferometer makes the measurement light transmitted through different lengths of optical paths interfere with the reference light to generate an auxiliary signal; the optical path for chamber calibration is calibrated by absorbing light of a specific wavelength; the data acquisition module collects the signals and transmits them to the digital signal processing module to generate the final ranging result

[0077] Embodiment 2: This embodiment further limits the all-fiber mirror swept-frequency interference ranging device based on wavelength division multiplexing provided in Embodiment 1. The optical path of the measurement interferometer includes two optical paths with unequal lengths. By detecting the interference information formed by the interference between the measurement light reflected by the target 11 and the reference light transmitted through the optical fiber, a measurement signal is obtained.

[0078] Embodiment 3: This embodiment further limits the all-fiber mirror swept-frequency interference ranging device based on wavelength division multiplexing provided in Embodiment 1. The optical path of the auxiliary interferometer includes two optical paths with unequal lengths. By detecting the interference information formed by the interference between the measurement light transmitted through the long optical fiber and the reference light transmitted through the short optical fiber, an auxiliary signal is obtained.

[0079] Embodiment 4: This embodiment further limits the all-fiber mirror swept-frequency interference ranging device based on wavelength division multiplexing provided in Embodiment 1. The optical path for chamber calibration and the optical path of the auxiliary interferometer share part of the optical path through a circulator to calibrate the optical path of the auxiliary interferometer.

[0080] Embodiment 5. This embodiment further limits the all-fiber mirror frequency-swept interference ranging device based on wavelength division multiplexing provided in Embodiment 1. The optical path of the measurement interferometer includes two balanced detectors for outputting the measurement signal, which are connected to the digital acquisition and processing module through a multiplier.

[0081] Embodiment 6. This embodiment further limits the all-fiber mirror frequency-swept interference ranging device based on wavelength division multiplexing provided in Embodiment 5. The optical path of the auxiliary interferometer includes two balanced detectors for outputting the auxiliary signal, which are connected to the digital acquisition and processing module through a multiplier.

[0082] Embodiment 7. This embodiment provides an all-fiber mirror frequency-swept interference ranging method based on wavelength division multiplexing. The method is implemented based on the device provided in Embodiment 1 and includes:

[0083] Steps of collecting measurement signals, auxiliary signals and calibration signals; steps of generating a reference signal and mixing and filtering the reference signal with the auxiliary signal to obtain a processed auxiliary signal; steps of mixing and filtering the processed auxiliary signal and performing phase demodulation to obtain the step of correcting the phase of the interferometer signal; steps of mixing the measurement signal and using the corrected interferometer signal phase and calibration signal to obtain a ranging result.

[0084] Specifically:

[0085] Method 1 is based on wavelength division multiplexing technology and realizes high-precision all-fiber mirror frequency-swept interference ranging through optical path and signal processing steps. Its steps include signal acquisition, mixing processing, band-pass filtering, phase demodulation and final ranging calculation.

[0086] Signal acquisition

[0087] Input: Multiple signals to be processed, including measurement signals, auxiliary signals and calibration signals.

[0088] Output: Acquired signal data.

[0089] Detailed process: The computer receives the signals to be processed from the measurement interferometer, auxiliary interferometer and gas chamber calibration optical path. These signals are collected by sensors and recorded in the time domain.

[0090] Mixing processing

[0091] Input: Acquired signal data.

[0092] Output: Mixed signals.

[0093] Detailed process: The computer generates a reference signal and performs mixing processing with the two acquired auxiliary signals respectively to obtain mixed signals.

[0094] Mixing processing, band-pass filtering

[0095] Input: The mixed signal.

[0096] Output: The mixed and filtered signal.

[0097] Detailed process: Mix the mixed signal again, and then filter out the signal for correcting non-linearity through a band-pass filter to obtain the band-pass filtered signal. The purpose of this step is to extract useful frequency components to improve the accuracy of the signal.

[0098] Phase demodulation

[0099] Input: The band-pass filtered signal.

[0100] Output: Correct the phase of the interferometer signal.

[0101] Detailed process: Perform phase demodulation on the band-pass filtered signal to obtain the demodulated signal phase, that is, correct the phase of the interferometer signal. This step is to extract the phase information of the signal for subsequent distance calculation.

[0102] Final ranging calculation

[0103] Input: The corrected interferometer signal phase, the measurement signal, and the calibration signal.

[0104] Output: The measured distance value.

[0105] Detailed process: Use the corrected interferometer signal phase and the calibration signal to process the measured signal after mixing through a specific algorithm, and calculate the distance to target 11. This step combines the results of all the previous steps and outputs the final ranging result.

[0106] Embodiment 8. This embodiment provides a full-fiber mirror-swept frequency interference ranging method based on wavelength division multiplexing. The method is implemented based on the device provided in Embodiment 5 and includes:

[0107] The steps of collecting the measurement signal, the auxiliary signal, and the calibration signal; generating a reference signal, mixing and filtering the reference signal with the auxiliary signal, and performing phase demodulation to obtain the step of correcting the phase of the interferometer signal; and the step of obtaining the ranging result according to the measurement signal by using the corrected interferometer signal phase and the calibration signal.

[0108] Specifically:

[0109] Method 2 is also based on wavelength division multiplexing technology. Through improved signal processing and correction methods, the ranging accuracy and efficiency are further improved. Its steps include signal acquisition, mixing processing, band-pass filtering, phase demodulation, and final ranging calculation.

[0110] Signal acquisition

[0111] Input: Multiple signals to be processed, including measurement signals, auxiliary signals, and calibration signals.

[0112] Output: Acquired signal data.

[0113] Detailed process: The computer receives the signals to be processed from the measurement interferometer, auxiliary interferometer, and gas chamber calibration optical path. These signals are acquired through a data acquisition card and recorded in the time domain.

[0114] Mixed-frequency processing

[0115] Input: Acquired auxiliary signals.

[0116] Output: Mixed-frequency signals.

[0117] Detailed process: The computer generates a reference signal and performs mixed-frequency processing with the acquired auxiliary signals to obtain the mixed-frequency signals.

[0118] Band-pass filtering

[0119] Input: Mixed-frequency auxiliary signals.

[0120] Output: Band-pass filtered signals.

[0121] Detailed process: Pass the mixed-frequency auxiliary signals through a band-pass filter to select the signals for correcting non-linearity and obtain the band-pass filtered signals. The purpose of this step is to extract the useful frequency components to improve the accuracy of the signals.

[0122] Phase demodulation

[0123] Input: Band-pass filtered signals.

[0124] Output: Correct the phase of the interferometer signal.

[0125] Detailed process: Perform phase demodulation on the band-pass filtered signals to obtain the demodulated signal phase, that is, correct the phase of the interferometer signal. This step is to extract the phase information of the signal for subsequent distance calculation.

[0126] Final ranging calculation

[0127] Input: Corrected interferometer signal phase, measurement signal, calibration signal.

[0128] Output: Measured distance value.

[0129] Detailed process: By using the calibration interferometer signal phase and calibrating the signal, the measurement signal is processed through a specific algorithm, and the distance of the target 11 is obtained through calculation. This step combines the results of all the previous steps and outputs the final ranging result.

[0130] Embodiment 9. This embodiment provides a computer storage medium for storing a computer program, which, when read by a computer, implements the method provided in Embodiment 7 or 8.

[0131] Embodiment 10. This embodiment provides a computer, including a processor and a storage medium, which, when the computer program stored in the storage medium is read by the processor, implements the method provided in Embodiment 7 or 8.

[0132] Embodiment 11. This embodiment provides a computer program product storing a computer program, which, when read by a processor, implements the method provided in Embodiment 7 or 8.

[0133] Embodiment 12. In combination with Figures 1-5 describing this embodiment, this embodiment further describes the above-provided technical solution in detail through specific examples. Specifically:

[0134] This embodiment provides a wavelength-division multiplexing-based all-fiber mirror swept-frequency interference ranging device and method;

[0135] The wavelength-division multiplexing-based all-fiber mirror swept-frequency interference ranging device includes:

[0136] The laser unit 1 includes a first tunable laser source 1, a second tunable laser source 2, a first isolator 3, a second isolator 4, a first coupler 5, a first wavelength-division multiplexer 6, and a second coupler 7. The first and second tunable laser sources respectively output swept-frequency light with mirror-image swept-frequency ranges. The two swept-frequency lights can be separated by a wavelength-division multiplexer. The detection light output by the first tunable laser source 1 passes through the first isolator 3 and is split by the first coupler 5 and enters the gas chamber calibration optical path 4 and the first wavelength-division multiplexer 6 respectively. The detection light output by the second tunable laser source 2 also enters the first wavelength-division multiplexer 6 through the second isolator 4. The two swept-frequency lights are combined by the first wavelength-division multiplexer 6 and enter the second coupler 7. After being split by the second coupler 7, they enter the measurement interferometer 2 and the auxiliary interferometer 3 respectively.

[0137] The measurement interferometer II includes a third coupler 8, a first circulator 9, an optical system 10, a target 11, a fourth coupler 12, a second wavelength division multiplexer 13, a third wavelength division multiplexer 14, a first balanced detector 15, and a second balanced detector 16. The swept-frequency light from the second coupler 7 is split by the third coupler 8 to obtain the measurement light and the reference light of the measurement interferometer. The measurement light passes through the first circulator 9 and the optical system 10, and after being reflected by the surface of the target 11 to be measured, it returns along the original path to the optical system 10, outputs from the other end of the first circulator 9, and is combined with the reference light obtained by splitting the other path of the third coupler 8 at the fourth coupler 12. After being output from the fourth coupler 12, it is respectively input into the second wavelength division multiplexer 13 and the third wavelength division multiplexer 14, and swept-frequency lights with two detection lights as light sources can be respectively obtained, which are respectively detected by the first balanced detector 15 and the second balanced detector 16 to obtain two measurement interferometer signals generated by the detection lights.

[0138] The auxiliary interferometer III includes a fifth coupler 17, a sixth coupler 18, a second circulator 19, a fourth wavelength division multiplexer 20, a fifth wavelength division multiplexer 21, a third balanced detector 22, and a fourth balanced detector 23. The swept-frequency light received from the split output of the second coupler 7 is split by the fifth coupler 17 to obtain the measurement light and the reference light of the auxiliary interferometer. The measurement light and the reference light respectively pass through longer optical fiber paths and shorter optical fiber paths, and are combined by the sixth coupler 18. The swept-frequency light output from the sixth coupler 18 is respectively input into two paths of the second circulator 19, the fourth wavelength division multiplexer 20, and the fifth wavelength division multiplexer 21, and swept-frequency lights with two detection lights as light sources can be respectively obtained, which are respectively detected by the third balanced detector 22 and the fourth balanced detector 23, and two auxiliary interferometer signals generated by the detection lights can be obtained.

[0139] The gas chamber calibration optical path IV includes a first detector 24, a gas chamber 25, a seventh coupler 26, a second detector 27, a fifth coupler 17, a sixth coupler 18, and a second circulator 19. The swept-frequency light obtained by splitting from the first coupler 5 is input into the gas chamber calibration optical path IV, and is split by the seventh coupler 26. A part of the split light beam passes through the gas chamber 25 and is detected by the first detector 24, and the other part passes through the second circulator 19, and is divided into measurement light and reference light by the sixth coupler 18 and respectively passes through longer optical fiber paths and shorter optical fiber paths, and is combined by the fifth coupler 17, and its output light is detected by the second detector 27. The gas chamber calibration signal can be obtained through the first and second detectors 24 and 27.

[0140] There are two structures in the data acquisition part:

[0141] The measurement interferometer II, the auxiliary interferometer III, and the data acquisition and data processing module 28 respectively have two connection structures. One is to be directly connected, such as Figure 1, secondly, it is connected through the first multiplier 29 and the second multiplier 30, as Figure 2 .

[0142] As Figure 3 and 4 shown,

[0143] The method includes the following steps:

[0144] Step 1: This step has different processing methods according to different structures.

[0145] In step 1 of Structure 1, the computer receives the signals to be processed i 1m (t), i 2m (t), i 1f (t), i 2f (t), i c (t), i gc (t); when the ranging device is Structure 2, the computer receives the signals to be processed i m (t), i f (t), i c (t), i gc (t). Where t is the sampling clock.

[0146] Step 2: This step has different processing methods according to different structures.

[0147] In step 2 of Structure 1, the computer generates signals i aux1 (t), i aux2 (t) and respectively mix them with the mirror sweep-assisted signals i 1f (t), i 2f (t) obtained in step 1 of Structure 1 to obtain signals i′ 1f (t), i′ 2f (t), mix the signals i′ 1f (t), i′ 2f (t) again to obtain signal i′ f (t), perform band-pass filtering on i′ f (t), and the signal i″ f (t) for correcting the nonlinearity of the measurement interferometer signal can be filtered out. Perform phase demodulation on i″ f (t) to obtain the corrected interferometer signal phase

[0148] In step 2 of Structure 2, the computer generates signal i aux (t) and mix it with the auxiliary signal i f (t) obtained in step 1 of Structure 2 to obtain signal i′ f (t), perform filtering on i′ f(t) Perform band-pass filtering to select the signal i″ for correcting the nonlinearity of the measurement interferometer signal. f (t), and perform phase demodulation on i″ f (t) to obtain the corrected interferometer signal phase.

[0149] Step 3: Mix the mirror sweep measurement signals i 1m (t), i 2m (t) obtained in Step 1 of Structure 1 to obtain the signal i m (t), and the sweep measurement signal i m (t) obtained in Step 1 of Structure 2. Use the corrected interferometer signal phase obtained in Step 2 to perform nonlinear correction on i m (t). After nonlinear correction, the signal i′ m (k) is obtained, where k = 0, 1, 2, …, K, and K is the total number of points of i′ m (k).

[0150] Step 4: Filter the gas cell absorption signal i gc (t) obtained in Step 1, and record the absolute optical frequency corresponding to the gas cell absorption peak and the sampling point serial number. Solve for the phase value of the signal i c (t) corresponding to the sampling serial number. By fitting the absolute optical frequency f c1 , f c2 , …, f cM and the phase value …, the auxiliary interferometer length L can be obtained from the slope. f .

[0151] Step 5: Perform spectral analysis on the signal i′ m (k) obtained in Step 3. Determine the frequency f corresponding to the highest spectral energy according to the spectral distribution of this signal. IF Use the auxiliary interferometer optical path L f obtained in Step 4. The frequency f IF can be converted into the absolute distance measurement value R of the target to be measured. m .

[0152] Preferably, Step 1 of the Structure 1 is specifically:

[0153] The mirror sweep measurement signals i 1m (t), i 2m (t) output from the measurement interferometer optical path and the mirror sweep auxiliary signals i 1f (t), i 2f (t) output from the auxiliary interferometer optical path can be expressed by the following formula (ignoring the amplitude):

[0154]

[0155] Among them, f 01 and f 02 are respectively the initial optical frequencies of the frequency modulation of the tuning lasers 1 and 2, and Δf1(t) and Δf2(t) are respectively the frequency modulation curves of the tuning lasers 1 and 2 (for simplified representation, written as Δf1 and Δf2 in the formula), n air is the refractive index of air, are respectively the refractive indices of the optical fibers corresponding to the initial optical frequencies of the tuning lasers 1 and 2, d f is the fiber dispersion coefficient within the swept frequency range, c is the speed of light, R m is the absolute distance of the target to be measured, and ΔR(t) is the motion change curve introduced by the target motion (for simplified representation, written as ΔR in the formula), R f is the optical transmission distance difference between the auxiliary interferometer measurement path and the reference path.

[0156] Step 1 of the structure 2 is specifically as follows:

[0157]

[0158] The chamber calibration signal i c (t) output from the chamber calibration optical path can be expressed by the following formula:

[0159]

[0160] The signal i gc (t) represents the chamber absorption signal.

[0161] Preferably, step 2 of the structure 1 is specifically as follows:

[0162] Generate the following reference signals i aux1 (t), i aux2 (t) through computer simulation:

[0163] i aux1 (t) = exp(j2πf aux1 t);

[0164] i aux2 (t) = exp(j2πf aux2 t);

[0165] Among them, f aux1 and f aux2 are respectively the frequencies of the signals i aux1 (t), i aux2 (t). The generated signals i aux1 (t), i aux2 (t) are respectively compared with the signal i 1f(Δf1), i 2f Multiply (Δf2), and the signals i′ 1f (t), i′ 2f (t) can be obtained respectively, as shown in the following formula:

[0166]

[0167] Wherein, are respectively the phases of i 1f (t), i 2f (t). Mix the generated signals i′ 1f (t), i′ 2f (t) again. After mixing, the signal i′ f (t) can be obtained:

[0168]

[0169] Step 2 of the second structure is specifically:

[0170] Generate a reference signal i aux (t) as shown in the following formula through computer simulation:

[0171] i aux (t) = exp[j2π(f aux1 - f aux 2)t];

[0172] Multiply the generated signal i aux1 (t) with the signal i f (t), and the same signal i′ f (t) as in step 2 of the second structure can be obtained.

[0173] The following processing flow of the first structure is the same as that of the second structure. Filter i′ f (t) to obtain i″ f (t), and the specific form is as shown in the following formula:

[0174]

[0175] Wherein, A″ f is the amplitude of the signal i″ f (t). Solve the phase of the signal i″ f (t). Using the known term 2π(f aux1 - f aux2 ), the phase of the calibration interferometer signal can be obtained through signal operation Since the frequency sweep rates and the refractive indices of the initial optical frequencies of the two light sources are similar, the phase is as shown in the following formula:

[0176]

[0177] Preferably, step 3 is specifically as follows:

[0178] Mix the signal i obtained in step 1 of Structure 1 1m (Δf1, ΔR), i 2m (Δf2, ΔR), and after mixing, the signal i m (t) is as shown in the following formula: (The signal i m (t) can be directly obtained in step 1 of Structure 2 without performing the following operations)

[0179]

[0180] Where are respectively the phases of i 1m (Δf1, ΔR), i 2m (Δf2, ΔR).

[0181] Use the signal phase obtained in step 2 to perform non - linear correction on i m (t), and after non - linear correction, the signal i′ m (k) is obtained, as shown in the following formula:

[0182]

[0183] Where k = 0, 1, 2, …, K, K is the total number of points of i′ m (k), and the phase of the second term of the signal i′ m (k) is further expanded and can be represented by the following formula:

[0184]

[0185] Where L f is the optical path of the auxiliary interferometer, is the phase of the auxiliary interferometer and so on is the phase - interval interpolation step.

[0186] Preferably, step 4 is specifically as follows:

[0187] Filter the gas - cell absorption signal i gc (t) obtained in step 1, and record the absolute optical frequency corresponding to the gas - cell absorption peak and the sampling - point serial number.

[0188] Solve for the phase value of the signal i c (t) corresponding to the sampling serial number, and by fitting the absolute optical frequency f c1 , f c2 , …, f cM and the phase value , … L can be obtained from the slope f .

[0189] Preferably, step 5 is specifically as follows:

[0190] Perform spectrum analysis on the signal i′ m (k) obtained in step 3, and determine the frequency f corresponding to the highest spectral energy according to the spectral distribution of the signal IF . This frequency can be expressed by the following formula:

[0191]

[0192] Use L obtained in step 4 f to obtain the absolute distance measurement value R of the target to be measured m :

[0193]

[0194] This embodiment has the following gain effects:

[0195] Compared with the prior art, this embodiment:

[0196] Adopting mirror synchronous frequency sweeping not only makes full use of the effective bandwidth of the light source, but also can solve the problem of spectral aliasing in the multi-target measurement scenario. Through wavelength division multiplexing cascading, the dual-band isolation can be effectively improved, and crosstalk of dual-band light can be avoided. Adopting a mirror synchronous frequency sweeping fiber structure not only effectively reduces the system volume to reduce the system complexity, but also can simultaneously immunize the adverse effects of spectral broadening caused by the target Doppler effect and chromatic dispersion mismatch in a large frequency sweeping range. During the construction of the measurement system, a calibration system temperature control system, etc. are proposed based on the mirror synchronous frequency sweeping fiber structure to ensure the stable and reliable measurement system reference; in the acquisition part, this system can use two acquisition structures, and these two structures can be selected according to needs, and the optimization goals beneficial to multi-target and the number of data channels can be realized respectively; in the signal processing part, it is proposed that the auxiliary interferometer phase can be quickly solved by means of a dual-reference frequency signal generated by a computer. In summary, the system with the above advantages can achieve all-fiber high-precision frequency sweeping interference measurement.

[0197] The above further describes the technical solutions provided by the present invention through several specific embodiments to highlight the advantages and beneficial effects of the technical solutions provided by the present invention. However, the above several specific embodiments are not used as a limitation to the present invention. Any reasonable modifications and improvements, combinations of embodiments, equivalent replacements, etc. based on the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An all-fiber mirror-swept frequency interference ranging device based on wavelength division multiplexing, characterized in that The device includes: A laser unit, including a first tunable laser source and a second tunable laser source, for outputting swept-frequency light with a mirrored swept-frequency range; A measurement interferometer optical path, for generating a measurement signal according to the swept-frequency light; An auxiliary interferometer optical path, for generating an auxiliary signal according to the swept-frequency light; A gas cell calibration optical path, for calibrating the optical path of the auxiliary interferometer according to the swept-frequency light; A data acquisition and processing module, for obtaining a ranging result according to the measurement signal, the auxiliary signal, and the calibration signal.

2. The all-fiber mirror-swept frequency interference ranging device based on wavelength division multiplexing according to claim 1, wherein The measurement interferometer optical path includes two optical paths with unequal lengths. By detecting the interference information between the measurement light reflected by the target and the reference light transmitted through the optical fiber, a measurement signal is obtained.

3. The all-fiber mirror-swept frequency interference ranging device based on wavelength division multiplexing according to claim 1, wherein The auxiliary interferometer optical path includes two optical paths with unequal lengths. By detecting the interference information between the measurement light transmitted through the long optical fiber and the reference light transmitted through the short optical fiber, an auxiliary signal is obtained.

4. The all-fiber mirror-swept frequency interference ranging device based on wavelength division multiplexing according to claim 1, characterized in that The gas cell calibration optical path and the auxiliary interferometer optical path share part of the optical path through a circulator to calibrate the optical path of the auxiliary interferometer.

5. The all-fiber mirror-swept frequency interference ranging device based on wavelength division multiplexing according to claim 1, wherein The measurement interferometer optical path includes two balanced detectors for outputting the measurement signal, which are connected to the data acquisition and processing module through a multiplier.

6. The all-fiber mirror-swept frequency interference ranging device based on wavelength division multiplexing according to claim 5, wherein The auxiliary interferometer optical path includes two balanced detectors for outputting the auxiliary signal, which are connected to the data acquisition and processing module through a multiplier.

7. The all-fiber mirror-swept frequency interference ranging method based on wavelength division multiplexing is characterized in that The method is implemented based on the device described in claim 1 and includes: Steps of collecting a measurement signal, an auxiliary signal, and a calibration signal; generating a reference signal, mixing and filtering the reference signal with the auxiliary signal to obtain a processed auxiliary signal; mixing and filtering the processed auxiliary signal and performing phase demodulation to obtain a step of correcting the phase of the interferometer signal; mixing the measurement signal, and using the corrected interferometer signal phase and the calibration signal to obtain a ranging result.

8. The all-fiber mirror-swept frequency interference ranging method based on wavelength division multiplexing is characterized in that The method is implemented based on the device described in claim 5 and includes: Steps of collecting a measurement signal, an auxiliary signal, and a calibration signal; generating a reference signal, mixing, filtering, and performing phase demodulation on the reference signal and the auxiliary signal to obtain a step of correcting the phase of the interferometer signal; according to the measurement signal, using the corrected interferometer signal phase and the calibration signal to obtain a ranging result.

9. A computer storage medium for storing a computer program, characterized in that, When the computer program is read by a computer, the method described in claim 7 or 8 is implemented.

10. A computer, comprising a processor and a storage medium, characterized in that, When the computer program stored in the storage medium is read by a processor, the method described in claim 7 or 8 is implemented.

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