A fully fiber-optic vortex interferometry system and a method for measuring phase change.

Abstract

This invention relates to an all-fiber vortex interferometer system and a method for measuring phase change, belonging to the field of optical precision instrument design and testing. The aim is to achieve ultra-high precision phase change measurement using an all-fiber structure. The vortex interferometer system, along the optical path, sequentially includes a light source module, an optical fiber beam splitter module, an optical fiber sensing module, an optical fiber mode conversion module, an optical fiber mode interferometry module, and an imaging module. The phase change measurement method is a phase change demodulation method based on angular Fourier transform proposed for the all-fiber vortex interferometer system. The interferometer proposed in this invention eliminates the complex optical path alignment steps of traditional interferometers, and the sensitivity of the all-fiber vortex interferometer is further improved.

Description

Technical Field

[0001] This invention belongs to the field of optical precision instrument design and testing technology, and particularly relates to an all-fiber vortex interferometry system and a method for measuring phase change. Background Technology

[0002] A beam with a spiral phase wavefront is called a vortex beam, also known as an orbital angular momentum (OAM) beam. It has found wide applications in optical manipulation, optical communication, and precision metrology, and has even sparked research booms in fields such as liquid surface waves and acoustics. Thanks to the inherent spiral phase wavefront of the OAM beam, interference between OAM beams or between an OAM beam and a Gaussian beam can linearly map the phase change to be measured as a rotation of the optical field pattern. The combination of an OAM beam and a traditional interferometer is called an optical vortex interferometer (OVI), which has been applied to the measurement of displacement, refractive index, and temperature. If the angular order difference between the two beams selected for OVI is... When the phase change between beams is At that time, the light field pattern will rotate. This means that the sensitivity of OVI is affected by the angular order difference of the OAM beam. Decide.

[0003] If the tilt angles of the two beams in OVI are mismatched, a "crosshair" interference pattern will be produced. If the tilt angles are matched, the matching of sphericity will correspond to two patterns: "petal" and "spiral," which are the interference patterns selected by OVI. Specifically, using conjugate OAM beams of the same intensity for interference can produce a "petal" pattern, which requires matching of beam divergence and tilt angle. Using OAM beams with different divergences and Gaussian beams for interference can produce a "spiral" pattern, which requires matching of beam tilt angles and strict alignment of beam centers. For demodulation of petal patterns, researchers have proposed methods such as centroid identification, correlation coefficient, and azimuth complex spectrum. However, the minimum angular order difference that can be constructed for petal patterns is limited. The value of 2 directly limits the interferometer's sensitivity. To handle more complex spiral patterns, researchers have developed methods such as principal component analysis and Mohr's pointer method. Compared to petal patterns, spiral patterns can construct a minimum angular order difference of 1, meaning a two-fold increase in sensitivity. These demodulation schemes require more complex algorithms, higher-quality light field patterns, and may even be unable to handle minute intensity center shifts.

[0004] Fiber optic sensors offer advantages such as high compactness, strong compatibility, and strong long-range sensing capabilities. Current research is implementing some OVI (Optical Vision Indicator) functions within optical fibers. This includes using optical fibers as the carrier of the sensing area or integrating OAM (Optical Amplitude Modulation) beam generation into the fiber. To date, it is possible to achieve angular order difference... The interference structure has not yet been integrated into the optical fiber, or in other words, the two beams used for interference need to be synthesized by devices in free space. To reduce or avoid systematic errors caused by the tilt of the signal light and the reference light, differences in sphericity, and offset of the intensity center, the accuracy of traditional OVI relies on strict optical path alignment, which brings great inconvenience. Summary of the Invention

[0005] In view of this, the present invention aims to provide an all-fiber vortex interferometer system and a method for measuring phase change, so as to avoid the complex optical path alignment steps of spatial interferometers and further improve the sensitivity of all-fiber vortex interferometers. The present invention can avoid the cumbersome coaxial adjustment steps of the optical path, eliminate systematic errors caused by problems such as tilting of the signal light and reference light, sphericity differences, and intensity center offset, and its minimum angular order difference... With a value of 1, sensitivity is improved.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first aspect of this application provides an all-fiber vortex interferometry system; the vortex interferometry system includes a light source module, an optical fiber beam splitter module, an optical fiber sensing module, an optical fiber mode conversion module, an optical fiber mode interferometry module and an imaging module connected sequentially along the optical path, wherein the optical fiber beam splitter module splits the beam into two paths, one path is a probe arm, which is connected to the optical fiber mode conversion module through the optical fiber sensing module, and the other path is a reference arm, which is directly connected to the optical fiber mode conversion module.

[0008] The optical fibers include both traditional solid-core fibers and hollow-core fibers and microstructured fibers capable of supporting multiple intrinsic modes; the light source module provides the single-wavelength continuous laser required by the vortex interferometer; the fiber beam splitting module is used to distribute the single-path input laser to the reference arm and the probe arm; the fiber sensing module is used to generate phase changes on the probe arm fiber; the fiber mode conversion module is used to convert low-order modes within the fiber to high-order modes; the fiber mode interferometry module is used to combine the laser beams of the reference arm and the probe arm; and the imaging module is used to image the fiber light field.

[0009] Furthermore, the light source module is selected from a single-wavelength laser or a tunable laser.

[0010] Furthermore, the fiber optic beam splitter module refers to an all-fiber device capable of distributing a single-path input laser to the reference arm and the probe arm at any power ratio, including a single-mode fiber coupler and an attenuator.

[0011] Furthermore, the fiber optic sensing module refers to a device capable of converting changes in external physical or chemical parameters into changes in the phase of light waves; wherein:

[0012] The external physical or chemical parameters refer to the external physical or chemical parameters to be detected, including temperature and stress that can be directly detected using the thermo-optical effect and elasto-optical effect of traditional solid-core optical fibers, and solution refractive index or suspension concentration that can be indirectly detected by tapering or grinding.

[0013] Furthermore, the fiber mode conversion module refers to a device that converts a low-order mode group within an optical fiber into a high-order mode group; wherein:

[0014] The low-order mode group refers to the mode group with a higher effective mode refractive index, including but not limited to the fundamental mode group.

[0015] The higher-order mode group refers to the mode group with a lower effective refractive index compared to the lower-order mode.

[0016] The device refers to an optical fiber device that enables mode conversion within the optical fiber, including mode selection couplers, long-period fiber gratings, and photonic lanterns, as well as devices that utilize misaligned fusion splicing to generate higher-order modes.

[0017] Furthermore, the fiber mode interferometry module refers to a device that realizes interferometry of different fiber modes, including devices capable of simultaneously realizing mode conversion and mode interferometry, or devices capable of only realizing mode interferometry, and a fiber polarization controller for providing perturbation to achieve phase matching of fiber modes; wherein:

[0018] Different optical fibers refer to optical fibers that are spatially separated and can carry information independently, including single-mode fiber-few-mode fiber and microstructure fiber-few-mode fiber combination.

[0019] Furthermore, the imaging module refers to a module that images the light field within the optical fiber for computer analysis, and is a combination of a lens, a polarization management device, and a camera; wherein:

[0020] Polarization management devices are devices used to filter the polarization state of optical fiber output, including polarizers alone or combinations of waveplates and polarizers.

[0021] A second aspect of this application provides an all-fiber vortex interferometry phase change measurement method, implemented using the aforementioned interferometric system, comprising:

[0022] S1: Adjust the fiber polarization controller in the fiber mode interference module to disturb the mode in the fiber so that the phases of different modes in the same module match each other. At the same time, adjust the polarization management device in the imaging module and observe the light field pattern after polarization state screening until it presents a vortex state.

[0023] S2: Adjust the attenuator in the fiber optic beam splitter module to make the laser power of the reference arm or the detector arm zero, use the imaging module to perform imaging, and use the light field pattern corresponding to the non-zero power arm to locate the center of the light field analysis.

[0024] S3: Adjust the attenuator in the fiber optic beam splitter module so that the laser power of the reference arm and the detector arm are on the same order of magnitude. Use the imaging module to perform imaging. With the light field analysis center selected in step S2 as the center, determine the radius of the analysis ring. Its size is preferably slightly larger than the non-central singularity position.

[0025] S4: Adjust the fiber optic sensing module to change the external physical or chemical parameters. When the external physical or chemical parameters to be detected change, sample the light field pattern, process the light beam phase change, and further calculate the change in the external physical or chemical parameters.

[0026] Furthermore, the location of the light field analysis center described in step S2 refers to the process of determining the light field center when performing light field image analysis using a computer, including locating the light field analysis center using the fundamental mode module and the non-fundamental mode module; wherein:

[0027] Using the fundamental mode module to locate the optical field analysis center means adjusting the laser power of other modules to zero and using the fundamental mode module to locate the optical field pattern obtained by the imaging system, including using the point with the maximum intensity of the fiber fundamental mode or the centroid of the fiber fundamental mode optical field as the optical field analysis center.

[0028] Locating the optical field analysis center using the non-fundamental mode module refers to adjusting the laser power of other modules to zero and using the non-fundamental mode module to locate the optical field pattern obtained by the imaging system, including using the singularity of the non-fundamental mode center as the optical field analysis center.

[0029] Further, the processing of the light field pattern in step S4 refers to: analyzing the light field pattern obtained by the imaging system using computer methods to determine the amount of phase change of the light wave, and further determining the changes in the physical or chemical parameters of the external environment to be detected by understanding the mechanism by which known external parameters affect the amount of phase change of the light wave; wherein:

[0030] Computer methods refer to the process of using computers to perform mathematical analysis on light field patterns in order to know the amount of phase change of the light wave, including the use of angular Fourier transform and singularity direction positioning to know the amount of phase change of the probe arm;

[0031] The mechanism by which known external parameters affect the change in the phase of light waves refers to the known relationship between changes in the physical or chemical parameters of the external environment to be detected and the resulting changes in the phase of light waves, including thermo-optical effect, elasto-optical effect, and electro-optical effect.

[0032] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0033] (1) The all-fiber vortex interferometry system of the present invention has advantages such as small size and low cost. Compared with other vortex interferometry systems, the vortex interferometry system of the present invention fully integrates the functions of vortex beam generation and vortex beam interference into the optical fiber, eliminating the need for cumbersome optical path coaxial adjustment steps, and effectively reducing system errors caused by problems such as tilting of the signal light and reference light, sphericity difference, and intensity center offset. Compared with other fiber vortex interferometry systems, the vortex interferometry system of the present invention supports vortex beam interference of any order, especially supporting minimum angular beam order difference of 0. The vortex beam interference theoretically has higher sensitivity.

[0034] (2) The all-fiber vortex interference phase change measurement method of the present invention has the advantages of strong robustness and high sensitivity; compared with the centroid identification method, the demodulation method of the present invention can process the vortex beam interference pattern with arbitrary angular order difference. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the all-fiber vortex interferometry system described in this invention. The system includes: a light source module, a fiber beam splitter module, a fiber sensing module, a fiber mode conversion module, a fiber mode interferometry module, and an imaging module.

[0036] Figure 2 This is a schematic diagram of a specific implementation structure of the all-fiber vortex interferometer system described in this invention, including: 1, a 1550 nm fiber laser; 2, a single-mode fiber coupler; 3a, a first fiber tunable attenuator; 3b, a second fiber tunable attenuator; 4a, a mode selection coupler for lower-order module conversion; 4b, a mode selection coupler for higher-order module conversion; 5a, a first fiber polarization controller; 5b, a second fiber polarization controller; 6, a collimator; 7, a polarizer; 8, a camera; and 9, a temperature control chamber.

[0037] Figure 3 This is a flowchart of the all-fiber vortex interferometry phase change measurement process described in this invention.

[0038] Figure 4 The present invention compares the all-fiber vortex interferometry phase change measurement method with the traditional free-space OVI phase change measurement process, wherein: (a) OAM beam generation; (b) optical field centroid positioning; (c) analysis radius selection; (d) angular Fourier transform and data analysis.

[0039] Figure 5The results of temperature measurement using the all-fiber vortex interferometry system described in this invention are as follows: (a) the change in rotation angle with temperature under different angular order differences; (b) the order of the OAM beam used for interferometry, with the same line shape as (a); (c) the phase change... At that time, the rotation of the light field pattern corresponding to the different order differences of the OAM beam angle is consistent with (a). Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0041] It should be noted that the following detailed descriptions are exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should be noted that the terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0042] Example 1: All-fiber vortex interferometry system

[0043] like Figure 1 , Figure 2 As shown, the vortex interferometer system described in the embodiment of the present invention includes a light source module, an optical fiber beam splitter module, an optical fiber sensing module, an optical fiber mode conversion module, an optical fiber mode interferometer module, and an imaging module connected sequentially along the optical path. The optical fiber beam splitter module splits the light beam into two paths: one is a probe arm that is connected to the optical fiber mode conversion module through the optical fiber sensing module, and the other is a reference arm that is directly connected to the optical fiber mode conversion module.

[0044] In this embodiment of the invention, the light source module uses a 1550 nm fiber laser 1.

[0045] In this embodiment of the invention, the fiber optic splitting module uses a single-mode fiber coupler with a splitting ratio of 5:5.

[0046] In some embodiments, the fiber optic sensing module is designed to realize and enhance the responsiveness of optical wave characteristics to external physical or chemical parameters. Traditional solid-core optical fibers can be processed using tapering or grinding methods, or special optical fibers or a combination of the above methods can be used to make the optical wave phase respond to external physical or chemical parameters; materials whose optical properties change significantly with external physical or chemical parameters, such as liquid crystals and magnetohydrodynamics, can also be introduced.

[0047] In this embodiment of the invention, temperature is used as the sensing object. The fiber optic sensing module consists only of a single-mode optical fiber placed inside the temperature control chamber 9. Due to the thermo-optic effect, changes in temperature directly affect the phase delay of the light wave passing through the fixed-length single-mode optical fiber. The effective heating length of the temperature control chamber is 31 cm, and the temperature can be adjusted from 30 to 75 °C.

[0048] In this embodiment of the invention, the fiber mode conversion module and the fiber mode interferometry module are integrated. The all-fiber device simultaneously performs the mode conversion function of converting low-order modes to high-order modes, and the mode interferometry function of coupling low-order and high-order mode beams into the same few-mode fiber. The fiber mode conversion and fiber mode interferometry modules are implemented by cascaded mode selection couplers 4a and 4b. The function of mode selection coupler 4 is as follows: Figure 2 As shown, a mode selection coupler customized for a specific order of few-mode fiber can convert the fundamental mode beam in a single-mode fiber into a higher-order mode and couple it into the few-mode fiber. Simultaneously, mode selection coupler 4b allows the lower-order modes at the input end of the few-mode fiber to pass through. When cascaded mode selection couplers 4a and 4b are used, interference between the fundamental mode beam and the higher-order mode beam can be achieved in the same few-mode fiber.

[0049] In this embodiment of the invention, the imaging module includes a collimator 6, a polarizer 7, and a camera 8. A polarization modulation element is used to filter the specific polarization state of the beam, ensuring that the fundamental mode beam and the higher-order mode beams are completely coherent. The higher-order mode beam is... The beam corresponding to the module appears as a ring-shaped spot, or vortex state, after passing through the polarizer; the fundamental mode beam is also... The beam corresponding to the module exhibits a Gaussian distribution after passing through the polarizer.

[0050] Example 2: A Method for Measuring Phase Changes via All-Fiber Vortex Interference

[0051] This invention also provides an all-fiber vortex interferometry phase change measurement method, such as... Figure 3 As shown. The all-fiber vortex interferometry system described in Example 1 (see Example 1) is used. Figure 2 The specific implementation process includes:

[0052] S1: Adjust the fiber polarization controllers 5a and 5b in the fiber mode interference module to disturb the mode in the fiber so that the phases of different modes in the same module match each other. At the same time, adjust the polarizer 7 in the imaging module and observe the light field pattern after polarization state screening until it presents a vortex state.

[0053] In this embodiment of the invention, the reference arm power attenuation 3b needs to be adjusted to its maximum to observe the optical field pattern morphology corresponding to the probe arm. While adjusting the polarization controller 5b on the few-mode fiber, the optical field pattern measured by the imaging system is observed in real time. Adjustment is completed when the pattern approaches a ring shape. Figure 4 As shown in (a). If a non-fundamental mode module is used to interfere with a higher-order module, it is also necessary to restore the reference arm attenuation 3b and adjust the probe arm attenuation 3a to the maximum to observe the fiber optical field pattern corresponding to the reference arm. Similarly, when adjusting the polarization controller 5b on the few-mode fiber, the fiber optical field pattern measured by the imaging system is observed in real time. The adjustment is completed when it is approximately circular, as shown in (a). Figure 4 As shown in (a).

[0054] S2: Adjust the attenuators 3a and 3b in the fiber optic beam splitter module so that the laser power of the reference arm or the detector arm is zero, and use the imaging module described in Example 1 to perform imaging, and use the light field pattern corresponding to the non-zero power arm to locate the center of the light field analysis.

[0055] In this embodiment of the invention, the process of locating the optical field analysis center in step S2 is achieved by adjusting the laser power of the probe arm to zero and then selecting the point with the maximum power of the fundamental mode beam, such as... Figure 4 (b) As shown on the right. If a non-fundamental mode module is used to interfere with a higher-order module, the center of the optical field analysis needs to be determined by selecting the central singularity.

[0056] S3: Adjust attenuators 3a and 3b in the fiber optic beam splitter module so that the laser power of the reference arm and the detector arm are on the same order of magnitude. Use the imaging module described in Example 1 to perform imaging. Using the optical field analysis center selected in S2 as the center, determine the radius of the analysis ring. Its size is preferably slightly larger than the non-central singularity position. Figure 4 (c) As shown on the right;

[0057] In this embodiment of the invention, the attenuation level of the reference arm and the probe arm is adjusted by the camera settings in the imaging system. Under certain settings, it is preferable to achieve a clear interference pattern without overexposure.

[0058] S4: Adjust the fiber optic sensing module to change the external physical or chemical parameters. When the external physical or chemical parameters to be detected change, sample the light field pattern, process the light beam phase change, and further calculate the change in the external physical or chemical parameters.

[0059] In this embodiment of the invention, the processing of the light field pattern adopts the form of angular Fourier transform. Through angular Fourier transform, the azimuth complex spectrum is obtained, and further demodulation is used to obtain the phase change, such as... Figure 4 As shown in (d).

[0060] Figure 4The invention provides a comparison between the all-fiber vortex interferometry phase change measurement method described in this invention and the traditional free-space OVI phase change measurement method. The vortex interferometry phase measurement method described in this invention exhibits advantages in vortex beam generation, optical field center positioning, and analysis radius selection.

[0061] To clearly illustrate the all-fiber vortex interferometry phase change measurement method provided by this invention, the temperature testing process and results are presented when three different order mode selection coupler combinations are used, such as... Figure 5 As shown. The specific process of the experiment is analyzed as follows:

[0062] First, select as Modules and The mode selection coupler for module development, according to Figure 2 The optical path is connected, and the sensing area is a 31 cm long single-mode optical fiber placed inside the temperature-controlled chamber 9. Then, the laser is turned on, and steps S1-S3 are executed to adjust the target temperature of the temperature-controlled chamber in 5°C increments. The light field pattern obtained by the imaging system is monitored in real time, and data is acquired after the pattern stabilizes. Finally, step S4 is executed to calculate the rotation amount corresponding to the light field pattern, obtaining... Figure 5 (a) shows the approximate linear relationship corresponding to the solid line. Figure 5 In (b), the solid lines indicate the wavefronts of the two vortex beams used for mode interference. Figure 5 The solid line in (c) indicates the phase delay of At that time, the rotation of the light field is .

[0063] After the first set of experiments was completed, it was switched to and The mode selection coupler developed for the module yielded the second set of results corresponding to the dashed line. After completing both sets of experiments, the method was changed to... and The mode selection coupler developed by the module obtained the third set of results corresponding to the dotted line.

[0064] like Figure 5 As shown in (a), linear fitting was performed on the results obtained independently from the interference of different modules, yielding solid lines, dashed lines, and dotted lines, respectively. Multiplying their slopes by the corresponding vortex order differences, the phase changes caused by temperature were calculated to be 44.19, 45.20, and 44.01 rad / (℃·m), respectively. With other conditions identical in the three independent experiments, the measured phase changes caused by temperature were close, demonstrating the robustness of the vortex interference phase change measurement method proposed in this invention.

[0065] like Figure 5 As shown in (c), the external phase delay is a fixed value. At that time, the rotation amounts of the light field pattern are respectively , as well as These correspond to solid lines, dashed lines, and dotted lines, respectively. Under a given external phase change, a larger rotation indicates a stronger phase change response capability. Clearly, using two modes with the lowest angular order difference for interferometry, i.e., selecting... Modules and When using a mode selection coupler in module development, this vortex interferometer system exhibits the highest sensitivity in measuring phase change.

[0066] The all-fiber vortex interferometry system described in this invention can be used to measure phase changes. For example... Figure 5 As shown in (a), the change in external physical or chemical parameters can be further calculated using the results of linear fitting, which is the change in external temperature in this embodiment.

[0067] The above-described specific embodiments are merely illustrative of the technical solutions of the present invention and not intended to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific embodiments of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A fully fiber-optic vortex interferometry system, characterized in that, The vortex interferometer system includes a light source module, an optical fiber beam splitter module, an optical fiber sensing module, an optical fiber mode conversion module, an optical fiber mode interferometer module, and an imaging module connected sequentially along the optical path. The optical fiber beam splitter module splits the light beam into two paths: one is a probe arm that is connected to the optical fiber mode conversion module through the optical fiber sensing module, and the other is a reference arm that is directly connected to the optical fiber mode conversion module. The optical fibers include both traditional solid-core fibers and hollow-core fibers and microstructured fibers capable of supporting multiple intrinsic modes; the light source module provides the single-wavelength continuous laser required by the vortex interferometer; the fiber beam splitting module is used to distribute the single-path input laser to the reference arm and the probe arm; the fiber sensing module is used to generate phase changes on the probe arm fiber; the fiber mode conversion module and the fiber mode interferometry module are integrated and implemented by an all-fiber device, which simultaneously performs the mode conversion function of converting low-order modes within the fiber to high-order modes, and the mode interferometry function of coupling low-order and high-order mode beams into the same few-mode fiber; the imaging module is used for imaging the fiber light field.

2. The all-fiber vortex interferometry system as described in claim 1, characterized in that, The light source module can be a single-wavelength laser or a tunable laser.

3. The all-fiber vortex interferometry system as described in claim 1, characterized in that, The fiber optic beam splitter module refers to an all-fiber device that can distribute a single-channel input laser to the reference arm and the probe arm at any power ratio, including a single-mode fiber coupler and an attenuator.

4. The all-fiber vortex interferometry system as described in claim 3, characterized in that, The fiber optic sensing module refers to a device capable of converting changes in external physical or chemical parameters into changes in the phase of a light beam; wherein: The external physical or chemical parameters refer to the external physical or chemical parameters to be detected, including temperature and stress that can be directly detected using the thermo-optical effect and elasto-optical effect of traditional solid-core optical fibers, and solution refractive index or suspension concentration that can be indirectly detected by tapering or grinding.

5. The all-fiber vortex interferometry system as described in claim 1, characterized in that, The fiber optic mode conversion module refers to a device that converts a low-order mode group within an optical fiber into a high-order mode group; wherein: The effective mode refractive index of the lower-order mode group is higher than that of the higher-order mode group. The device refers to an optical fiber device that enables mode conversion within the optical fiber, including mode selection couplers, long-period fiber gratings, and photonic lanterns, as well as devices that utilize misaligned fusion splicing to generate higher-order modes.

6. The all-fiber vortex interferometry system as described in claim 4, characterized in that, The fiber optic mode interferometry module includes an all-fiber device capable of simultaneously performing mode conversion and mode interferometry, and a fiber polarization controller for providing perturbations to achieve phase matching of the fiber modes; wherein: Different optical fibers refer to optical fibers that are spatially separated and can carry information independently, including single-mode fiber-few-mode fiber and microstructure fiber-few-mode fiber combination.

7. The all-fiber vortex interferometry system as described in claim 6, characterized in that, The imaging module refers to a module that images the light field within the optical fiber for computer analysis; it is a combination of a lens, a polarization management device, and a camera. Polarization management devices are devices used to filter the polarization state of optical fiber output, including polarizers alone or combinations of waveplates and polarizers.

8. A method for measuring phase change of vortex interferometry using an all-fiber optic system, characterized in that, Implemented using the interference system described in claim 7, comprising: S1: Adjust the fiber polarization controller in the fiber mode interference module to disturb the mode in the fiber so that the phases of different modes in the same module match each other. At the same time, adjust the polarization management device in the imaging module and observe the light field pattern after polarization state screening until it presents a vortex state. S2: Adjust the attenuator in the fiber optic beam splitter module to make the laser power of the reference arm or the detector arm zero, use the imaging module to perform imaging, and use the light field pattern corresponding to the non-zero power arm to locate the center of the light field analysis. S3: Adjust the attenuator in the fiber optic beam splitter module so that the laser power of the reference arm and the detector arm are of the same order of magnitude. Use the imaging module to perform imaging. With the light field analysis center selected in step S2 as the center, determine the radius of the analysis ring so that the radius of the analysis ring is greater than the distance between the light field analysis center and the non-central singularity in the interference pattern. S4: Adjust the fiber optic sensing module to change the external physical or chemical parameters. When the external physical or chemical parameters to be detected change, sample the light field pattern and process it to obtain the amount of change in the beam phase. Then, calculate the amount of change in the external physical or chemical parameters.

9. The all-fiber vortex interferometry phase change measurement method as described in claim 8, characterized in that, The location of the light field analysis center mentioned in step S2 refers to the process of determining the light field center when performing light field image analysis using a computer, including locating the light field analysis center using the fundamental mode module and the non-fundamental mode module; wherein: Using the fundamental mode module to locate the optical field analysis center means adjusting the laser power of other modules to zero and using the fundamental mode module to locate the optical field pattern obtained by the imaging module, including using the point with the maximum intensity of the fiber fundamental mode or the centroid of the fiber fundamental mode optical field as the optical field analysis center. Locating the optical field analysis center using the non-fundamental mode module refers to adjusting the laser power of other modules to zero and using the non-fundamental mode module to locate the optical field pattern obtained by the imaging module, including using the singularity of the non-fundamental mode center as the optical field analysis center.

10. The all-fiber vortex interferometry phase change measurement method as described in claim 8, characterized in that, The processing of the light field pattern in step S4 refers to: analyzing the light field pattern obtained by the imaging module using computer methods to determine the phase change of the light beam; and further understanding the changes in the physical or chemical parameters of the external environment to be detected by knowing the mechanism by which external parameters affect the phase change of the light beam. Computer methods refer to the process of using computers to perform mathematical analysis on light field patterns in order to know the amount of phase change of the light beam, including the use of angular Fourier transform and singularity direction positioning methods to know the amount of phase change of the probe arm. The mechanism by which known external parameters affect the phase change of the beam refers to the known relationship between changes in the physical or chemical parameters of the external environment to be detected and the resulting phase change of the beam, including thermo-optical effect, elasto-optical effect, and electro-optical effect.

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