Spectral coding two-dimensional imaging system based on single-cavity double-optical-comb fiber laser

Abstract

The invention provides a spectrum coding two-dimensional imaging system based on a single-cavity double-optical-comb fiber laser, and belongs to the field of single-cavity double-optical-comb imaging. The defects that a traditional double-optical-comb laser is tedious in structure and too large in size are overcome. Comprising a pumping source, a wavelength division multiplexer, an erbium-doped fiber, a second fiber coupler, an isolator, a micro fiber loop mode interference filter, a carbon nanotube saturable absorber and a polarization controller, pulse laser emitted by a pumping source is sent to one input end of a wavelength division multiplexer, and the output end of the wavelength division multiplexer is connected with an erbium-doped fiber, a second fiber coupler, an isolator, a micro fiber loop mode interference filter, a carbon nanotube saturable absorber and a polarization controller end to end. The output end of the polarization controller is connected with the other input end of the wavelength division multiplexer; the method is applied to spectral coding two-dimensional imaging.

Description

Technical Field

[0001] This application relates to the technical field of single - cavity dual - optical - comb imaging, and particularly to a spectral - encoding two - dimensional imaging system based on a single - cavity dual - optical - comb fiber laser. Background Art

[0002] Dual - optical - comb technology uses two optical frequency combs with slightly different repetition frequencies to perform asynchronous optical sampling in the time domain, enabling fast sampling of the target to be measured without mechanical delay scanning. Generally, two sets of lasers are used to generate an optical frequency comb respectively, but the coherence and stability between these two optical frequency combs are poor, and an external frequency - stabilization system is required for frequency locking to eliminate the incoherence between frequencies. This not only increases the system volume but also significantly improves the overall complexity. If two optical frequency combs can be generated in a single laser cavity, since the two optical frequency combs share the same laser cavity structure and experience basically the same external environmental interference, the common - mode noise caused by environmental factors can be effectively reduced. Therefore, the generated dual - optical - comb simultaneously has the characteristics of high coherence and stability, and simplifies the device structure greatly.

[0003] Spectral - encoding imaging technology maps different wavelengths to different spatial positions through a spatial disperser, thus encoding the spatial information of an object onto the spectrum of an ultrafast pulsed laser. Without the need for a mechanical scanning device that limits the scanning speed, accuracy, and practicality, fast image acquisition can be achieved. The spatial disperser used in spectral encoding can be a virtual imaging phase array (VIPA) or a grating. When the light beam is reflected by the target to be measured, the intensity and phase information are encoded onto the broadband spectrum, and then beat - frequency occurs with the reference light. The beat - frequency signal is demodulated using Fourier transform to construct the surface profile of the object. When the spectral - encoding imaging method using both a virtual imaging array and a grating is adopted, the beam - matching requirements for optical elements in the system become extremely strict, thus increasing the complexity of the overall design.

[0004] Some researchers have only used the grating-based spectral encoding imaging technology combined with a one-dimensional displacement stage, which greatly simplifies the imaging process. By using this method, the one-dimensional spectral information of the target to be measured can be encoded onto the spectrum of an ultrafast pulse. The one-dimensional spectral encoding is uniformly swept across the target to be measured through the one-dimensional displacement stage, and then the spectral information is collected by a high-bandwidth photodetector, and finally the imaging information of the target to be measured is restored. Most traditional imaging is based on a single laser combined with mechanical delay scanning sampling technology to achieve point or line scanning imaging. The mechanical delay device has a slow scanning speed and poor stability, which ultimately leads to a serious decline in imaging resolution. To solve this problem, some researchers have proposed applying the dual-comb technology to spectral encoding imaging. By using the dual-comb asynchronous optical sampling technology, not only can the imaging speed be improved, but also the imaging resolution can be improved. However, the dual-comb technology used in this imaging system requires an electronic feedback frequency stabilization device to eliminate the inconsistency between the frequencies of the two optical frequency combs, which increases the complexity and cost of the spectral encoding two-dimensional imaging system and restricts the wide application of spectral encoding two-dimensional imaging outside the laboratory. Summary of the Invention

[0005] To solve the above technical problems, the present application proposes a spectral encoding two-dimensional imaging system based on a single-cavity dual-comb fiber laser. Using the single-cavity dual-comb fiber laser as the light source, it overcomes the disadvantages of the traditional dual-comb laser using a frequency-stabilized dual-cavity laser system, such as cumbersome structure and too large volume; using spectral encoding imaging technology, combined with the advantages of the dual-comb broadband spectrum, high mutual coherence, and effective reduction of common-mode noise, two-dimensional imaging is realized, and the problems of slow imaging speed and low imaging resolution are solved.

[0006] The technical solution adopted by the present application is: a spectral encoding two-dimensional imaging system based on a single-cavity dual-comb fiber laser, including a single-cavity dual-comb fiber laser, an amplification and beat-frequency module, and a signal acquisition and processing module connected in sequence. The single-cavity dual-comb fiber laser includes a pump source, a wavelength division multiplexer, an erbium-doped fiber, a second fiber coupler, an isolator, a microfiber ring mode interference filter, a carbon nanotube saturable absorber, and a polarization controller. The pulsed laser emitted by the pump source is sent to one input end of the wavelength division multiplexer. The output end of the wavelength division multiplexer is connected end to end with the erbium-doped fiber, the second fiber coupler, the isolator, the microfiber ring mode interference filter, the carbon nanotube saturable absorber, and the polarization controller. The output end of the polarization controller is connected to the other input end of the wavelength division multiplexer to form an optical resonator.

[0007] Furthermore, the amplification and beat frequency module includes a coarse wavelength division multiplexer, an optical fiber amplifier, a circulator, an optical fiber collimator, a ruled diffraction grating, an achromatic lens, a slit, a one-dimensional displacement stage, a first optical fiber coupler, and a balanced photodetector. The coarse wavelength division multiplexer divides the pulse train in the single-cavity dual-comb optical fiber laser into two beams: one beam is used as the reference light, and the other beam is used as the measurement light. The optical fiber amplifier is used to perform spectral broadening and pulse energy amplification on the measurement light. The circulator is designed with three ports for transporting and receiving pulses. Port 1 of the circulator is connected to the output of the optical fiber amplifier, and Port 2 of the circulator is connected to the input of the optical fiber collimator. At the same time, Port 2 also serves as an output for coupling the encoded measurement light back into the cavity for subsequent beat frequency with the reference light. Port 3 of the circulator is connected to the first optical fiber coupler. The optical fiber collimator converts the amplified and broadened measurement light output from the circulator into a spatial beam and irradiates it onto the ruled diffraction grating. The ruled diffraction grating separates the measurement light into diffracted lights in different directions. The achromatic lens changes the measurement light diffracted by the ruled diffraction grating into a parallel beam. The slit controls the width of the parallel beam after passing through the achromatic lens. The one-dimensional displacement stage is used to carry the target to be measured. The measurement light is reflected by the target to be measured and coupled back into Port 3 of the circulator. Finally, the measurement light and the reference light generate a beat frequency in the first optical fiber coupler in front of the balanced photodetector, and the beat frequency signal is detected and recorded by the balanced photodetector.

[0008] Furthermore, the signal acquisition and processing module includes a computer, on which a data acquisition board is integrated, storing the beat frequency signal and performing Fourier transform on the beat frequency signal to reproduce the intensity and phase information of the measurement light.

[0009] Furthermore, the microfiber loop mode interference filter is a loop composed of microfibers. Its manufacturing process is as follows: Connect a section of single-mode fiber to both ends of the microfiber, directly tie a knot with the single-mode fibers at the two independent ends of the microfiber to form a loop. During operation, hold the single-mode fibers at both ends of the microfiber and slowly pull. As the pulling progresses, the size of the loop will gradually become smaller, and the knot will also move. Eventually, the loop shrinks to only the microfiber part, including the knot part which is also microfiber, forming a microfiber loop. When the light beam propagates in the microfiber loop, mode interference occurs in the loop formed by tying the knot of the microfiber, forming a comb filter with a filtering period and modulation depth. Finally, place the microfiber loop mode interference filter on the wafer.

[0010] Furthermore, the second optical fiber coupler has two output ends, and the output power ratio is 30:70. One end with 70% of the output power is connected to the isolator, and the end with 30% of the output power serves as the output end of the single-cavity dual-comb optical fiber laser.

[0011] Furthermore, the single-cavity dual-comb optical fiber laser, the coarse wavelength division multiplexer, the optical fiber amplifier, the circulator, the optical fiber collimator, and the first optical fiber coupler all operate in the near-infrared 1550 nm band.

[0012] Further, the balanced photodetector operates in the 800 - 1700 nm band with a bandwidth of 75 MHz.

[0013] Further, the focal length of the fiber collimator is 20 mm, and the focal length of the achromatic lens is 200 mm.

[0014] Further, the fiber amplifier uses an erbium - doped fiber amplifier.

[0015] Further, the filtering bandwidth of the coarse wavelength division multiplexer is 7.5 nm.

[0016] The beneficial effects of this application compared with the prior art are as follows:

[0017] 1. A spectral - encoding two - dimensional imaging system based on a single - cavity dual - optical - comb fiber laser disclosed in this application uses the dual - optical - comb asynchronous optical sampling technology to encode the intensity and phase information of the target to be measured onto the broadband spectrum of the measurement light. By processing the beat signal through Fourier transform, the intensity and phase information of the measurement light are reproduced. Without the need to rely on a high - bandwidth photodetector, a single - cavity dual - optical - comb fiber laser is used to replace two sets of independent lasers. At the same time, a narrow - band detector can be used to collect data, greatly improving the imaging resolution and speed of the system and reducing the system cost.

[0018] 2. The single - cavity dual - optical - comb fiber laser proposed in this application uses a carbon nanotube saturable absorber to achieve mode - locking. With the help of the micro - fiber - loop mode interference filter as the function of the comb filter to achieve dual - wavelength output, a train of pulses is generated in a single laser cavity, which contains two pulses with different central wavelengths and different repetition frequencies. Since these two pulses share the same laser cavity and are subject to the same external interference, these two pulses have good mutual coherence. Compared with traditional dual - optical - combs, there is no need to rely on a complex external frequency - stabilization device, simplifying the complexity of the system.

[0019] 3. The spectral filter composed of a polarization controller combined with a micro - fiber - loop mode interference filter in the single - cavity dual - optical - comb fiber laser proposed in this application can adjust the modulation depth and filtering period of the spectral filter, which can meet the mode - locking central wavelength and the dual - optical - comb repetition - frequency difference required for spectral - encoding two - dimensional imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The following further describes this application with reference to the drawings:

[0021] Figure 1 It is a schematic structural diagram of a spectral - encoding two - dimensional imaging system based on a single - cavity dual - optical - comb fiber laser provided by an embodiment of this application;

[0022] Figure 2 It is a schematic structural diagram of a single - cavity dual - optical - comb fiber laser provided by an embodiment of this application;

[0023] Figure 3 This is the output spectrum diagram of the single - cavity dual - optical - comb fiber laser provided by the embodiment of the present application when the pump power is 217 mW;

[0024] Figure 4 This is the output frequency spectrum diagram of the single - cavity dual - optical - comb fiber laser provided by the embodiment of the present application when the pump power is 217 mW;

[0025] Figure 5 This is the output time - domain diagram of the single - cavity dual - optical - comb fiber laser provided by the embodiment of the present application when the pump power is 217 mW;

[0026] Figure 6 This is the beat - frequency signal diagram collected by the spectral - encoding two - dimensional imaging system based on the single - cavity dual - optical - comb fiber laser provided by this embodiment;

[0027] In the figure: 1 is a single - cavity dual - optical - comb fiber laser, 2 is a coarse wavelength division multiplexer, 3 is an optical fiber amplifier, 4 is a circulator, 5 is an optical fiber collimator, 6 is a ruled diffraction grating, 7 is an achromatic lens, 8 is a slit, 9 is a target to be measured, 10 is a one - dimensional displacement stage, 11 is a first fiber coupler, 12 is a balanced photodetector, 13 is a computer;

[0028] 21 is a wavelength division multiplexer, 22 is an erbium - doped fiber, 23 is a second fiber coupler, 24 is an isolator, 25 is a micro - fiber - ring mode interference filter, 26 is a carbon nanotube saturable absorber, 27 is a polarization controller, 28 is a pump source. Detailed implementation manners

[0029] As Figures 1 to 6 shown, the present application provides a spectral - encoding two - dimensional imaging system based on a single - cavity dual - optical - comb fiber laser, including: a single - cavity dual - optical - comb fiber laser 1, a coarse wavelength division multiplexer 2, an optical fiber amplifier 3, a circulator 4, an optical fiber collimator 5, a ruled diffraction grating 6, an achromatic lens 7, a slit 8, a one - dimensional displacement stage 10, a first fiber coupler 11, a balanced photodetector 12, and a computer 13;

[0030] The single-cavity dual-frequency comb fiber laser 1 is used to emit a train of pulses, and the train of pulses contains two pulses with different central wavelengths and repetition frequencies; the coarse wavelength division multiplexer 2 functions as a filter and can divide the train of pulses in the single-cavity dual-frequency comb fiber laser 1 into two beams: one beam is used as the reference light, and the other beam is used as the measurement light; the fiber amplifier 3 is used to perform spectral broadening and pulse energy amplification on the measurement light; the circulator 4 is designed with three ports and is used to transmit and receive pulses. Port 1 of the circulator 4 is connected to the output of the fiber amplifier 3, and port 2 of the circulator 4 is connected to the input of the fiber collimator 5. At the same time, port 2 is also used as an output to couple the encoded measurement light back into the cavity for subsequent beat frequency with the reference light; port 3 of the circulator 4 is connected to the first fiber coupler 11; the fiber collimator 5 converts the amplified and broadened measurement light output from the circulator 4 into a spatial beam and irradiates it onto the ruled diffraction grating 6; the ruled diffraction grating 6 separates the measurement light into diffracted lights in different directions, thereby realizing the beam expansion function, and the separated measurement light is convenient for spectral analysis; the achromatic lens 7 converts the measurement light diffracted by the ruled diffraction grating 6 into a parallel beam; the slit 8 controls the width of the parallel beam after passing through the achromatic lens 7 and needs to be adjusted manually; the one-dimensional displacement stage 10 is used to carry the target to be measured 9 to make the overall imaging process fully automatic; the first fiber coupler 11 combines the measurement light output from the circulator 4 and the reference light output from the coarse wavelength division multiplexer 2 to make the measurement light and the reference light generate beat frequency; the balanced photodetector 12 is used to record the beat frequency signal generated by the beat frequency of the reference light and the measurement light; the computer 13 is equipped with a PXI-5122 board card to collect the time-domain signal at a speed of 100 MB / s, store the beat frequency signal, perform Fourier transform on the beat frequency signal, and reproduce the intensity and phase information of the measurement light.

[0031] Such as Figure 2As shown in the figure, the single - cavity dual - optical - comb fiber laser 1 includes: a pump source 28, a wavelength - division multiplexer 21, an erbium - doped fiber 22, a second fiber coupler 23, an isolator 24, a micro - fiber - ring mode interference filter 25, a carbon - nanotube saturable absorber 26, and a polarization controller 27; the pump source 28 is connected to one input end of the wavelength - division multiplexer 21; the output end of the wavelength - division multiplexer 21 is connected to the erbium - doped fiber 22, and the other input end of the wavelength - division multiplexer 21 is connected to one end of the polarization controller 27; the erbium - doped fiber 22 is connected to the input end of the second fiber coupler 23. The second fiber coupler 23 has two output ends with an output - power ratio of 30:70. The 70% end is connected to the isolator 24, and the 30% end is used as the output end of the laser; the isolator 24 is connected to the micro - fiber - ring mode interference filter 25 to ensure unidirectional light propagation in the cavity; the micro - fiber - ring mode interference filter 25 is connected to the carbon - nanotube saturable absorber 26, and the carbon - nanotube saturable absorber 26 is used for mode - locking; the carbon - nanotube saturable absorber 26 is connected to the polarization controller 27, thus forming a loop; the micro - fiber - ring mode interference filter 25 acts as a comb filter in the cavity. By adjusting the polarization state in the cavity through the polarization controller 27, two pulses are output at the 30% end of the second fiber coupler 23, that is, two pulses with different central wavelengths and repetition frequencies are generated in the same resonant cavity. The repetition - frequency difference between the two pulses can be changed by controlling the state of the polarization controller 27.

[0032] The pump source 28 emits pulsed laser light at 976 nm and sends it to the 980 - nm input end of the wavelength - division multiplexer 21. The output end of the wavelength - division multiplexer 21 is connected end - to - end with the erbium - doped fiber 22, the second fiber coupler 23, the isolator 24, the micro - fiber - ring mode interference filter 25, the carbon - nanotube saturable absorber 26, and the polarization controller 27. The output end of the polarization controller 27 is connected to the 1550 - nm input end of the wavelength - division multiplexer 21, forming an optical resonant cavity.

[0033] In this embodiment, the micro - fiber - ring mode interference filter 25 is a ring composed of micro - fibers. Its manufacturing process is as follows: At both ends of the micro - fiber, a section of single - mode fiber is respectively connected. The single - mode fibers at the two independent ends of the micro - fiber are directly knotted to form a ring. During the operation, hold the single - mode fibers at both ends of the micro - fiber and slowly pull. As the pulling progresses, the size of the ring will gradually become smaller, and the knotting position will also move. Eventually, the ring shrinks to only the micro - fiber part, including the knotting part which is also micro - fiber, forming a micro - fiber ring; when the light beam propagates in the micro - fiber ring, mode interference occurs in the ring formed by knotting the micro - fiber, forming a comb filter with a filtering period and modulation depth. Finally, the micro - fiber - ring mode interference filter 25 is placed on the wafer.

[0034] In this embodiment, the single - cavity dual - optical - comb fiber laser 1, the coarse wavelength division multiplexer 2, the fiber amplifier 3, the circulator 4, the fiber collimator 5, and the first fiber coupler 11 all operate in the near - infrared 1550 nm band; the filtering bandwidth of the coarse wavelength division multiplexer 2 is 7.5 nm. The focal length of the fiber collimator 5 is 20 mm, and the focal length of the achromatic lens 7 is 200 mm. The ruled diffraction grating 6 has 1200 lines / mm. The balanced photodetector 12 operates in the 800 - 1700 nm band with a bandwidth of 75 MHz.

[0035] In this embodiment, the fiber amplifier 3 is an erbium - doped fiber amplifier.

[0036] In this embodiment, the ruled diffraction grating 6 converts the circular beam output by the fiber collimator 5 into a discrete linear beam.

[0037] In this embodiment, the slit 8 is composed of two filters and can precisely control the width of the transmitted beam; the beam width can be adjusted through the slit 8 to optimize the signal - to - noise ratio of the beat signal.

[0038] In this embodiment, the first fiber coupler 11 has a specification of 2×2, 50:50, enabling the measurement light and the reference light to generate a beat frequency in the coupler.

[0039] The one - dimensional displacement stage 10 in this embodiment is used to drive the target to be measured 9 to step at a speed of 30 μm / s, enabling the system to operate fully automatically and obtain imaging information without manual operation.

[0040] The principle of this application is as follows: The single - cavity dual - optical - comb fiber laser 1 emits a train of pulses. The train of pulses contains two types of pulses, and the central wavelengths and repetition frequencies of these two trains of pulses are different; the train of pulses is input into the coarse wavelength division multiplexer 2 through the optical fiber. The coarse wavelength division multiplexer 2 divides a train of pulses into two separate pulses, namely the reference light and the measurement light, and each of the two pulses has a central wavelength and a repetition frequency; subsequently, the measurement light is amplified in energy and broadened in spectrum through the fiber amplifier 3; then it is input into port 1 of the circulator 4. The measurement light passing through the circulator 4 is input into port 2 of the circulator 4 and is connected to the fiber collimator 5; the measurement light irradiates on the ruled diffraction grating 6 and undergoes diffraction, and the measurement light becomes a discrete linear beam; it irradiates on the achromatic lens 7, and the measurement light changes from a discrete state to a parallel beam and irradiates on the target to be measured 9; a slit 8 is placed between the achromatic lens and the target to be measured 9 for filtering, so that the spectrum of the measurement light is controlled within the spectrum range of the reference light, and the slit width is adjustable to maximize the signal - to - noise ratio of the beat signal and ensure that the beat signal is not distorted; the measurement light is reflected by the target to be measured 9 and coupled back into port 3 of the circulator 4; finally, the measurement light and the reference light generate a beat frequency in the first fiber coupler 11 in front of the balanced photodetector 12, and the beat signal is detected by the balanced photodetector 12; the beat signal stored by the computer 13 is as Figure 6As shown, the beat frequency signal is digitized, Fourier-transformed, its intensity or phase information is reproduced, and noise reduction processing is performed to form a two-dimensional intensity or phase image of the target to be measured 9.

[0041] In this embodiment, the output spectrum diagram of the single-cavity dual-comb fiber laser 1 when the pump power is 217 mW is as Figure 3 shown, and the output frequency spectrum diagram is as Figure 4 shown. The central wavelengths of the two pulses are 1534.75 nm and 1544.2 nm respectively, and their corresponding repetition frequencies are 52.201427 MHz and 52.202747 MHz. The time-domain diagram of the pulses is also shown in Figure 5 .

[0042] In the embodiment, the width of the slit 8 needs to be strictly controlled because the beam width directly emerging from the ruled diffraction grating 6 is very large. When directly using this beam as the measurement light, spectral aliasing may occur. Therefore, a slit 8 needs to be added after the ruled diffraction grating 6 to adjust the beam width; at the same time, the diffraction angle needs to be adjusted so that the system satisfies that when the beam width is the widest, the spectral width range is the largest, that is, the scanning range is the largest. When the time-domain signal is normal, the slit width Δx, the spectral bandwidth Δλ, and the diffraction angle θ m satisfy:

[0043] d(sinθ m +sinθ i ) = mλ;

[0044]

[0045] where θ i is the angle of light incident on the ruled diffraction grating, m is the diffraction order, and f is the focal length of the achromatic lens.

[0046] In this application, two pulses are generated by the single-cavity dual-comb fiber laser 1. One is used as the reference light, and the other is used as the measurement light to perform one-dimensional spectral encoding scanning on the target. Subsequently, the reference light and the measurement light interfere, and the interference signal is collected and processed by the signal acquisition and processing module, so as to realize the spectral encoding two-dimensional imaging of the target to be measured 9.

[0047] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; although this application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A spectrally encoded two-dimensional imaging system based on a single-cavity dual-comb fiber laser, characterized in that: The invention comprises a single-cavity dual-comb fiber laser, an amplification and beat frequency module and a signal acquisition and processing module which are connected in sequence. The single-cavity dual-comb fiber laser comprises a pump source, a wavelength division multiplexer, an erbium-doped fiber, a second fiber coupler, an isolator, a micro-fiber ring mode interference filter, a carbon nanotube saturable absorber and a polarization controller. The pulse laser emitted by the pump source is sent to an input end of the wavelength division multiplexer. The output end of the wavelength division multiplexer is connected end to end with the erbium-doped fiber, the second fiber coupler, the isolator, the micro-fiber ring mode interference filter, the carbon nanotube saturable absorber and the polarization controller. The output end of the polarization controller is connected to the other input end of the wavelength division multiplexer to form an optical resonant cavity.

2. The spectrally encoded two-dimensional imaging system based on a single-cavity dual-comb fiber laser according to claim 1, characterized in that: The amplification and beat frequency module includes a coarse wavelength division multiplexer, a fiber amplifier, a circulator, a fiber collimator, a ruled diffraction grating, an achromatic lens, a slit, a one-dimensional translation stage, a first fiber coupler and a balanced photodetector. The coarse wavelength division multiplexer divides the pulse train in the single-cavity dual-comb fiber laser into two beams: one beam is used as a reference light, and the other beam is used as a measurement light; the fiber amplifier is used to perform spectrum broadening and pulse energy amplification on the measurement light; The circulator is a three-port design for transmitting and receiving pulses. Port 1 of the circulator is connected to the output of the fiber amplifier, and port 2 of the circulator is connected to the input of the fiber collimator. At the same time, port 2 is used as an output to couple the encoded measurement light back into the cavity so as to generate beat frequency with the reference light later. Port 3 of the circulator is connected to the first fiber coupler. The fiber collimator converts the amplified and broadened measurement light output by the circulator into a spatial beam and irradiates it onto the ruled diffraction grating. The ruled diffraction grating separates the measurement light into diffracted light in different directions. The achromatic lens converts the measurement light diffracted by the ruled diffraction grating into a parallel beam. The slit controls the width of the parallel light beam after passing through the achromatic lens; the one-dimensional translation stage is used to carry the target to be measured; the measuring light is reflected by the target to be measured and coupled back to the port three of the circulator; finally, the measuring light and the reference light beat each other in the first optical fiber coupler in front of the balanced photodetector, and the beat signal is detected and recorded by the balanced photodetector.

3. The spectrally encoded two-dimensional imaging system based on a single-cavity dual-comb fiber laser according to claim 2, characterized in that: The signal acquisition and processing module includes a computer, which is integrated with a data acquisition board card, stores the beat frequency signal, performs Fourier transform on the beat frequency signal, and reproduces the intensity and phase information of the measurement light.

4. The spectrally encoded two-dimensional imaging system based on a single-cavity dual-comb fiber laser according to claim 1, characterized in that: The micro-fiber ring mode interference filter is a ring composed of micro-fibers. The manufacturing process is as follows: a section of single-mode optical fiber is connected to each end of the micro-fiber, and the single-mode optical fibers at the two independent ends of the micro-fiber are directly knotted to form a ring. During operation, the single-mode optical fibers at both ends of the micro-fiber are held and pulled slowly. As the pulling progresses, the size of the ring will gradually decrease, and the knot will also move. Eventually, the ring will shrink to only the micro-fiber part, including the knot, to form a micro-fiber ring. When the light beam propagates in the micro-fiber ring, mode interference occurs in the ring formed by the micro-fiber knotting, forming a comb filter with a filtering period and modulation depth. Finally, the micro-fiber ring mode interference filter is placed on the wafer.

5. The spectrally encoded two-dimensional imaging system based on a single-cavity dual-comb fiber laser according to claim 1, characterized in that: The second fiber coupler has two output ends with an output power ratio of 30:70, wherein the end with an output power of 70% is connected to the isolator, and the end with an output power of 30% serves as the output end of the single-cavity dual-comb fiber laser.

6. The spectrally encoded two-dimensional imaging system based on a single-cavity dual-comb fiber laser according to claim 1, characterized in that: The single-cavity dual-comb fiber laser, the coarse wavelength division multiplexer, the fiber amplifier, the circulator, the fiber collimator and the first fiber coupler all operate in the near-infrared 1550nm band.

7. The spectrally encoded two-dimensional imaging system based on a single-cavity dual-comb fiber laser according to claim 1, characterized in that: The balanced photodetector operates in the 800-1700nm band with a bandwidth of 75MHz.

8. The spectrally encoded two-dimensional imaging system based on a single-cavity dual-comb fiber laser according to claim 1, characterized in that: The focal length of the fiber collimator is 20 mm, and the focal length of the achromatic lens is 200 mm.

9. The spectrally encoded two-dimensional imaging system based on a single-cavity dual-comb fiber laser according to claim 2, characterized in that: The optical fiber amplifier adopts an erbium-doped optical fiber amplifier.

10. The spectrally encoded two-dimensional imaging system based on a single-cavity dual-comb fiber laser according to claim 1, characterized in that: The filter bandwidth of the CWDM is 7.5nm.

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