Vectorial rotation measurement method and apparatus based on multi-core optical fiber

Abstract

The present invention belongs to the field of optical measurements. Disclosed are a vectorial rotation measurement method and apparatus based on a multi-core optical fiber. A plurality of input light beams undergo non-uniform spatial transmission to form a structured scalar light field in a non-uniform spatial distribution; the scalar light field is used as detection light to irradiate rotationally moving particles in a collimated manner; the rotationally moving particles reflect signal light which carries movement information; Fourier analysis is performed on the signal light to obtain a Fourier magnitude spectrum and a Fourier phase spectrum; the magnitude of the velocity of the rotationally moving particles is calculated by means of the frequency peak in the Fourier magnitude spectrum; and calculation is performed by using a relative phase difference value corresponding to the Fourier phase spectrum, so as to infer the direction of the velocity of the rotationally moving particles, thereby realizing measurement which is performed on the vectorially rotationally moving particles on the basis of a multi-core optical fiber. The present invention breaks through the limitations of conventional solutions in which the magnitude and direction of a rotational movement velocity are subjected to vectorial measurement based on a scalar light field, and by means of an optical fiber assembly, detection light and signal light are transmitted on the same optical fiber, thereby improving the stability of a system.

Description

A vector rotation measurement method and device based on multi-core optical fiber

Technical field

[0001] The present invention belongs to the field of optical measurement, and more specifically, relates to a vector rotation measurement method and device based on multi-core optical fiber. [Background Technology]

[0002] The Doppler effect, caused by the relative motion between a wave source and an observer, is widely used in optical and acoustic measurement. Doppler velocimetry techniques developed based on the Doppler effect typically offer advantages such as high spatial resolution, a wide measurement range, and non-contact operation. Throughout the history of the Doppler effect, researchers have often focused on the frequency variations of a light field during its interaction with an object. Recently, as researchers explore the dimensionality of light fields, a new method for simultaneously determining the magnitude and direction of rotational motion has been discovered and confirmed, based on vector-polarized light fields whose polarization varies with space. This novel extension of the traditional Doppler effect provides a new approach for simultaneously determining the magnitude and direction of rotational motion. However, this vector-polarized light field requires complex free-space devices to generate and strictly control its polarization during transmission, making it difficult to achieve using conventional optical fiber architectures. Given the advantages of optical fiber for modern optical systems and the ease of transmitting scalar fields through optical fibers, it is crucial to develop a method for measuring vector motion using scalar light fields. Typically, conventional scalar light fields only extract information about the magnitude of velocity from motion. Objects moving in opposite rotational directions exhibit the same signal in a conventional scalar light field. However, for spatially asymmetric scalar light fields, signals in opposite rotational directions will produce a clear reversal in the time domain. This shows that the vector signal generated by the change in the rotational motion state in the spatially asymmetric scalar light field will exhibit extremely obvious variation characteristics. Compared with vector light fields that rely on polarization and phase control, asymmetric scalar light fields that are only intensity-dependent are more meaningful in simplifying practical systems for vector measurement. This asymmetric scalar light field can be generated by optical fibers and can also be transmitted in optical fibers. It does not rely on a coherent light source and does not require strict control of the polarization of light during transmission, reducing the complexity of the measurement system and having a wide range of applications.

[0003] [Summary of the invention]

[0004] In response to the shortcomings of the existing technology, the present invention provides a vector rotation speed measurement method and device based on multi-core optical fiber, aiming to break through the limitations of traditional scalar light fields in measuring vector rotational motion, realize the simultaneous measurement of the speed and direction of rotating particles through the optical fiber architecture, and fill the gaps in related technologies.

[0005] To achieve the above-mentioned purpose, the present invention provides a vector rotation speed measurement method based on multi-core optical fiber, comprising emitting multiple light beams from a light source, which are received by a multi-core optical fiber through a fan-in and fan-out module, and then transmitting a structured non-uniform spatially distributed scalar light field. The scalar light field passes through a probe as a collimated probe light to illuminate a rotating particle (angular velocity is Ω). The rotating particle reflects a signal light carrying motion information, which is collected by the probe and converged to the central core. The probe light and the signal light are transmitted by the same optical fiber, thereby remotely measuring the rotational motion. The detection end performs Fourier analysis on the signal light to obtain a Fourier amplitude spectrum and a phase spectrum. The magnitude of the rotating particle velocity is calculated by the frequency peak in the Fourier amplitude spectrum, and the direction of the rotating particle velocity is inferred by calculating the relative phase difference corresponding to the Fourier phase spectrum, thereby realizing the measurement of vector rotating particles based on multi-core optical fiber.

[0006] Preferably, when the detection light is a geometrically asymmetric scalar light field, the multi-core optical fiber selects a geometrically asymmetric outer ring core to pass light, and the transmitted light power is the same. The generated detection light field is a non-uniform spatially distributed scalar light field. Under the action of the scalar light field, the rotating particles reflect the signal light, and the signal light is subjected to Fourier analysis. The first frequency peak and the second frequency peak are extracted from the Fourier amplitude spectrum. The speed of the rotating particles can be calculated based on the frequency difference between two adjacent frequency peaks. The phases corresponding to the first frequency peak and the second frequency peak are then extracted from the Fourier phase spectrum, the relative phase difference is calculated, and the direction of the rotating particle velocity is determined based on the sign of the relative phase difference.

[0007] Preferably, when the detection light is an intensity asymmetric scalar light field, the multi-core optical fiber selects a geometrically symmetrical outer ring core to pass light, and the light power transmitted by each core is different. The generated detection light field is a non-uniform spatially distributed scalar light field. Under the action of the scalar light field, the rotating particles reflect the signal light, and the signal light is subjected to Fourier analysis. The first frequency peak and the second frequency peak are extracted from the Fourier amplitude spectrum. The speed of the rotating particles can be calculated based on the frequency difference between two adjacent frequency peaks. The phases corresponding to the first frequency peak and the second frequency peak are then extracted from the Fourier phase spectrum, the relative phase difference is calculated, and the direction of the rotating particle velocity is determined based on the sign of the relative phase difference.

[0008] Preferably, for a multi-core optical fiber, a specific number and position of outer ring cores are selected to transmit the probe light, and a single central core is selected to receive the signal light, and the length of the optical fiber is not limited. When the probe light is a geometrically asymmetric scalar light field, the number of cores selected to pass the light is not less than three, and a geometrically asymmetric structure is formed. When the probe light is an intensity asymmetric scalar light field, the number of cores selected to pass the light is not less than two. There are two ways to form a geometrically asymmetric scalar light field: first, the multi-core optical fiber originally has a circularly symmetric core distribution, and the probe light field is formed by selecting some asymmetric outer ring cores to pass the light; second, the multi-core optical fiber is designed and manufactured to have an asymmetric core distribution structure, and the probe light field is formed by passing the light through all outer ring cores.

[0009] For multiple input light sources, there are two preferred approaches for matching the optical fiber with the multi-core fiber: first, a single light source is split by a beam splitter into multiple coherent beams, which are then connected to the multi-core fiber to match the number of cores in the outer ring; second, different light sources output light that is connected to their respective cores. Furthermore, the light source is not restricted by wavelength, thus constructing a coherence- and wavelength-independent detection device.

[0010] According to another aspect of the present invention, a vector rotation speed measurement device based on a multi-core optical fiber is provided, comprising: a light source, a fan-in / fan-out module, a multi-core optical fiber, a probe, and a detection device. The light source emits multiple light paths, which are received by the fan-in / fan-out module at a specific outer ring core of the multi-core optical fiber. The multi-core optical fiber then transmits a structured, non-uniformly spatially distributed scalar light field. The scalar light field passes through the probe as probe light to illuminate rotating particles. The rotating particles reflect signal light carrying motion information. The signal light is collected by the probe into the central core of the multi-core optical fiber, thereby enabling the transmission of the probe light and the signal light through the same optical fiber bundle, and remote measurement of the rotational motion. The signal light is connected to the detection device via the fan-in / fan-out module from the central core. The detection device performs Fourier analysis on the signal light to obtain a Fourier amplitude spectrum and phase spectrum. The magnitude of the rotating particle velocity is calculated based on the frequency peaks in the Fourier amplitude spectrum, and the direction of the rotating particle velocity is inferred based on the relative phase difference corresponding to the Fourier phase spectrum, thereby achieving vector rotation speed measurement based on the multi-core optical fiber.

[0011] Preferably, for a multi-core optical fiber, when viewed from the end face, it includes a circle of outer ring fiber cores and a central fiber core. The number of outer ring fiber cores transmitting the detection light matches the non-uniform illumination scheme, and the central fiber core receiving the signal light is separate. The length of the multi-core optical fiber is not limited, and remote measurement is achieved by a low-loss long optical fiber. There are two ways to form a geometrically asymmetric scalar light field: first, the multi-core optical fiber originally has a circularly symmetrical core distribution, and a fan-in and fan-out module selects a part of the asymmetric outer ring fiber cores to pass light to form a detection light field; second, the multi-core optical fiber is manufactured into a structure with an asymmetric core distribution in terms of technology, and all outer ring fiber cores are passed to form a detection light field.

[0012] Preferably, there are two methods for emitting multiple beams of light from a light source and receiving them from an optical fiber: first, a single laser outputs laser light, which is split by a beam splitter into multiple coherent beams and connected to a multi-core optical fiber to match the number of cores in a specific outer ring; second, different lasers output laser light separately and connect to their respective cores. The light source has no wavelength restrictions and uses narrow-linewidth lasers or broad-spectrum lasers within the low-loss wavelength range of the multi-core optical fiber. The speed measurement device constructed in this way is coherent-free and wavelength-independent.

[0013] Preferably, for the fan-in / fan-out module, a bundle of multi-core optical fibers is coupled with multiple bundles of single-mode optical fibers for low-loss coupling, allowing each core of the multi-core optical fiber to be independently controlled. The fan-in / fan-out module is composed of all-fiber devices, integrated chip devices, or free-space discrete components, and each core of the multi-core optical fiber is connected to an independent fiber jumper. After selecting the fan-in / fan-out module, the optical path of the multi-core optical fiber transmission is divided into two types. The selected outer ring core receives the light provided by the light source to form the detection light, and the central core collects the light returned by the rotating particles to form the signal light. This constructs a speed measurement device in which the detection light and the signal light are transmitted on the same optical fiber.

[0014] Preferably, for the fiber optic probe device, a lens, an objective lens, a fiber optic collimator or a processing structure integrated in the end face of the optical fiber is used to adjust the optical path, expand the detection light and collimate it to illuminate the rotating object to be measured. At the same time, when the signal light is returned, the signal light is converged on the central fiber core, and the information of the area covered by the detection light field is efficiently recovered.

[0015] The above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0016] 1. The present invention is based on the principle of a structured spatially distributed scalar light field. Compared with the general scalar field Doppler velocity measurement method, it is innovative and has guiding significance for more general velocity measurement research. It has broad application prospects in optical measurement and sensing, filling the gap in related technical fields.

[0017] 2. The present invention can realize a one-time measurement of the complex rotational motion state of the particle, which can not only obtain the size of the particle's rotational angular velocity, but also determine the direction of the particle's rotational angular velocity, thus ensuring the integrity of the motion information obtained.

[0018] 3. The present invention is based on a multi-core optical fiber assembly and adopts a coaxial transmission structure for detection light and signal light, integrating the detection end and the receiving end on a single probe. The return signal from a distant place can be returned to the location of the transmitting end for detection, which greatly improves the practical value of the measurement system in remote measurement while reducing the cost of the measurement system.

[0019] 4. The present invention uses an ordinary light source input optical fiber as the detection light, eliminating the need for additional reference light in the measurement and allowing non-homologous light to be used for detection. Therefore, the measurement device is simpler and more compact, while avoiding coherent noise and the measurement results are less affected by environmental interference.

Brief Description of the Drawings

[0020] FIG1 is a schematic structural diagram of a vector rotation measurement method based on a multi-core optical fiber provided by the present invention;

[0021] FIG2 is a schematic diagram of a device for generating a structured spatial scalar light field according to an embodiment of the present invention;

[0022] FIG3 is a schematic diagram of the interaction between rotating particles and a structured spatial scalar light field provided by an embodiment of the present invention;

[0023] FIG4 is a schematic diagram of a detection device for a return signal provided by an embodiment of the present invention;

[0024] FIG5 is a diagram showing the detection results of rotating particles using a symmetrical scalar light field generated by a multi-core optical fiber provided in an embodiment of the present invention, wherein (a) is the time domain spectrum of the echo signal detected on the rotating particles under the symmetrical scalar light field in the embodiment of the present invention, and the rotation speed is Ω=40πrad / s; (b) is the Fourier frequency domain spectrum of the echo signal detected on the rotating particles under the symmetrical scalar light field in the embodiment of the present invention, and the rotation speed is Ω=40πrad / s; (c) is the time domain spectrum of the echo signal detected on the rotating particles under the symmetrical scalar light field in the embodiment of the present invention, and the rotation speed is Ω=80πrad / s; (d) is the Fourier frequency domain spectrum of the echo signal detected on the rotating particles under the symmetrical scalar light field in the embodiment of the present invention, and the rotation speed is Ω=80πrad / s; (e) is the variable speed measurement result obtained by detecting the rotating particles under the symmetrical scalar light field in the embodiment of the present invention;

[0025] FIG6 is a diagram showing the detection results of rotating particles using a geometrically asymmetric scalar light field generated by a multi-core optical fiber, wherein (a) is the time domain signal of the detection of counterclockwise rotating particles under the geometrically asymmetric scalar light field in an embodiment of the present invention; (b) is the Fourier amplitude spectrum of the detection of counterclockwise rotating particles under the geometrically asymmetric scalar light field in an embodiment of the present invention; (c) is the Fourier phase spectrum of the detection of counterclockwise rotating particles under the geometrically asymmetric scalar light field in an embodiment of the present invention; (d) is the time domain signal of the detection of clockwise rotating particles under the geometrically asymmetric scalar light field in an embodiment of the present invention; (e) is the Fourier amplitude spectrum of the detection of clockwise rotating particles under the geometrically asymmetric scalar light field in an embodiment of the present invention; and (f) is the Fourier phase spectrum of the detection of clockwise rotating particles under the geometrically asymmetric scalar light field in an embodiment of the present invention.

[0026] Figure 7 is a diagram showing the detection results of rotating particles using an intensity asymmetric scalar light field generated by a multi-core optical fiber, (a) is the time domain signal of the detection of counterclockwise rotating particles under the intensity asymmetric scalar light field in an embodiment of the present invention; (b) is the Fourier amplitude spectrum of the detection of counterclockwise rotating particles under the intensity asymmetric scalar light field in an embodiment of the present invention; (c) is the Fourier phase spectrum of the detection of counterclockwise rotating particles under the intensity asymmetric scalar light field in an embodiment of the present invention; (d) is the time domain signal of the detection of clockwise rotating particles under the intensity asymmetric scalar light field in an embodiment of the present invention; (e) is the Fourier amplitude spectrum of the detection of clockwise rotating particles under the intensity asymmetric scalar light field in an embodiment of the present invention; and (f) is the Fourier phase spectrum of the detection of clockwise rotating particles under the intensity asymmetric scalar light field in an embodiment of the present invention. [Specific implementation method]

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0028] The present invention provides a vector rotation speed measurement method based on multi-core optical fiber, comprising emitting multiple light beams from a light source, which are received by a specific number and position of cores selected by the multi-core optical fiber through a fan-in and fan-out module. The multi-core optical fiber then transmits a structured non-uniform spatially distributed scalar light field. The scalar light field passes through a probe as a collimated probe light to illuminate a rotating particle (with an angular velocity of Ω). The rotating particle reflects a signal light carrying motion information. The signal light is collected by the probe and converged to the central core. The probe light and the signal light are transmitted by the same optical fiber, thereby remotely measuring the rotational motion. The detection end performs Fourier analysis on the signal light to obtain a Fourier amplitude spectrum and a phase spectrum. The magnitude of the rotating particle velocity is calculated by the frequency peak in the Fourier amplitude spectrum. The direction of the rotating particle velocity is inferred by calculating the relative phase difference corresponding to the Fourier phase spectrum, thereby realizing the measurement of vector rotating particles based on multi-core optical fiber.

[0029] Specifically, when the detection light is a geometrically asymmetric scalar light field, the multi-core optical fiber selects a geometrically asymmetric outer ring core to pass light, and the transmitted light power is the same. The generated detection light field is a non-uniform spatially distributed scalar light field. Under the action of the scalar light field, the rotating particles reflect the signal light, and the signal light is subjected to Fourier analysis. The first frequency peak and the second frequency peak are extracted from the Fourier amplitude spectrum. The speed of the rotating particles can be calculated based on the frequency difference between two adjacent frequency peaks. The phases corresponding to the first frequency peak and the second frequency peak are then extracted from the Fourier phase spectrum, the relative phase difference is calculated, and the direction of the rotating particle velocity is determined based on the sign of the relative phase difference.

[0030] Specifically, when the detection light is an intensity asymmetric scalar light field, the multi-core optical fiber selects a geometrically symmetrical outer ring core to pass the light, and the light power transmitted by each core is different. The generated detection light field is a non-uniform spatially distributed scalar light field. Under the action of the scalar light field, the rotating particles reflect the signal light, and the signal light is subjected to Fourier analysis. The first frequency peak and the second frequency peak are extracted from the Fourier amplitude spectrum. The speed of the rotating particles can be calculated based on the frequency difference between two adjacent frequency peaks. The phases corresponding to the first frequency peak and the second frequency peak are then extracted from the Fourier phase spectrum, the relative phase difference is calculated, and the direction of the rotating particle velocity is determined based on the sign of the relative phase difference.

[0031] Specifically, for a multi-core optical fiber, a specific number and position of outer ring cores are selected to transmit the probe light, and a single central core is selected to receive the signal light, and the length of the optical fiber is not limited. When the probe light is a geometrically asymmetric scalar light field, the number of cores selected to pass the light is not less than three, and a geometrically asymmetric structure is formed. When the probe light is an intensity asymmetric scalar light field, the number of cores selected to pass the light is not less than two. There are two ways to form a geometrically asymmetric scalar light field: first, the multi-core optical fiber originally has a circularly symmetric core distribution, and the probe light field is formed by selecting some asymmetric outer ring cores to pass the light; second, the multi-core optical fiber is designed and manufactured with an asymmetric core distribution structure, and the probe light field is formed by passing the light through all outer ring cores.

[0032] Specifically, for multiple input sources, there are two approaches to matching the optical fiber with a multi-core fiber: First, a single optical source is split by a beam splitter into multiple coherent beams, which are then connected to the multi-core fiber to match the number of cores in the outer ring; second, different optical sources output light separately, each connected to its corresponding core. Furthermore, the optical source is wavelength-independent, thus creating a coherence- and wavelength-independent detection device.

[0033] According to another aspect of the present invention, a vector rotation speed measurement device based on a multi-core optical fiber is provided, comprising: a light source, a fan-in / fan-out module, a multi-core optical fiber, a probe, and a detection device. The light source emits multiple light paths, which are received by the fan-in / fan-out module at a specific outer ring core of the multi-core optical fiber. The multi-core optical fiber then transmits a structured, non-uniformly spatially distributed scalar light field. The scalar light field passes through the probe as probe light to illuminate rotating particles. The rotating particles reflect signal light carrying motion information. The signal light is collected by the probe into the central core of the multi-core optical fiber, thereby enabling the transmission of the probe light and the signal light through the same optical fiber bundle, and remote measurement of the rotational motion. The signal light is connected to the detection device via the fan-in / fan-out module from the central core. The detection device performs Fourier analysis on the signal light to obtain a Fourier amplitude spectrum and phase spectrum. The magnitude of the rotating particle velocity is calculated based on the frequency peaks in the Fourier amplitude spectrum, and the direction of the rotating particle velocity is inferred based on the relative phase difference corresponding to the Fourier phase spectrum, thereby achieving vector rotation speed measurement based on the multi-core optical fiber.

[0034] Specifically, for multi-core optical fiber, when viewed from the end face, it includes a circle of outer ring fiber cores and a central fiber core. The number of outer ring fiber cores that transmit detection light matches the non-uniform illumination scheme, and the central fiber core that receives signal light is separate. The length of multi-core optical fiber is not limited, and remote measurement is achieved by low-loss long optical fiber. There are two ways to form a geometrically asymmetric scalar light field: first, the multi-core optical fiber originally has a circularly symmetrical core distribution, and the fan-in and fan-out modules select some asymmetric outer ring fiber cores to pass light to form a detection light field; second, the multi-core optical fiber is manufactured into a structure with an asymmetric core distribution, and all outer ring fiber cores are passed light to form a detection light field.

[0035] Specifically, there are two ways to transmit multiple beams of light from a light source and receive them from an optical fiber: First, a single laser outputs laser light, which is split by a beam splitter into multiple coherent beams that are connected to a multi-core fiber to match the number of cores in a specific outer ring. Second, different lasers output laser light separately and connect to their respective cores. The light source has no wavelength restrictions and uses narrow-linewidth or broad-spectrum lasers within the low-loss wavelength range of the multi-core fiber. The speed measurement device constructed in this way is coherent-free and wavelength-independent.

[0036] Specifically, for the fan-in fan-out module, a bundle of multi-core optical fibers is coupled with multiple bundles of single-mode optical fibers for low-loss coupling, allowing each core of the multi-core optical fiber to be independently controlled. The fan-in fan-out module is composed of all-fiber devices, integrated chip devices, or free-space discrete components. Each core of the multi-core optical fiber is connected to an independent fiber jumper. After the fan-in fan-out module is selected, the optical path of the multi-core optical fiber transmission is divided into two types. The selected outer ring core receives the light provided by the light source to form the detection light, and the central core collects the light returned by the rotating particles to form the signal light. This constructs a speed measurement device in which the detection light and signal light are transmitted on the same optical fiber.

[0037] Specifically, for the fiber optic probe device, a lens, an objective lens, a fiber optic collimator, or a processing structure integrated in the end face of the optical fiber is used to adjust the optical path, expand the detection light, and collimate it to illuminate the rotating object to be measured. At the same time, when the signal light is returned, the signal light is converged on the central fiber core, and information on the area covered by the detection light field is efficiently recovered.

[0038] The following is a description with reference to specific embodiments and drawings.

[0039] As shown in Figure 1, the present invention provides a schematic structural diagram of a vector rotation measurement method based on a multi-core optical fiber, comprising: a light source 1, an optical fiber device 2, a structured scalar light field 3, rotating particles 4, a return signal 5, and a detection device 6. The light source 1 is an ordinary light source with adjustable power, which is divided into multiple optical paths and connected to the optical fiber device 2. The optical fiber device 2 generates and outputs a structured scalar light field 3 as a probe light. The structured scalar light field 3 vertically illuminates the rotating particles 4, which reflect the return signal 5. The return signal 5 is collected by the optical fiber device 2 and coaxially transmitted to the detection device 6 again through the optical fiber. The detection device 6 extracts information from the return signal 5 to achieve simultaneous measurement of the speed, magnitude, and direction of the rotating particles 4. Among them, the optical axis of the structured scalar light field 3 is aligned with the rotation axis of the rotating particle 4; the rotating particle 4 maintains rotational motion within the same plane, and its rotation trajectory is located in the structured scalar light field 3, which can reflect the light field at different spatial positions; the detection device 6 performs Fourier analysis on the return signal 5, extracts the Doppler frequency shift peak in the Fourier amplitude spectrum and the corresponding relative phase difference in the Fourier relative phase spectrum, and calculates the magnitude and direction information of the rotation speed of the rotating particle 4.

[0040] As shown in Figure 2, a schematic diagram of a device for generating a structured scalar light field provided by an embodiment of the present invention includes: a light source 1, several single-mode fiber ports 21 connected to the outer ring core, a fiber coupling device 22, a multi-core fiber 23 of a certain length, a multi-core fiber output port 24, a fiber collimator 25, a single-mode fiber port 26 connected to the central core, and a structured scalar light field 3. Light source 1 generates multiple light paths, all of which are ordinary Gaussian beams with adjustable power. These light paths are connected to the outer ring cores of the multi-core fiber via several single-mode fiber ports 21. Each port is then coupled to the same multi-core fiber 23 by a fiber coupling device 22. The light is transmitted through the multi-core fiber 23 to the output port 24. The light field output by the fiber is then passed through the fiber collimator 25 to form the structured scalar light field 3. Light source 1 only controls the power of the multiple light paths and does not require polarization. The light sources do not need to be the same, meaning they can be provided by multiple lasers or by a single laser via a beam splitter. The front end of the multi-core optical fiber 23 has a fan-in and fan-out module, which realizes high-efficiency coupling of each core of the multi-core optical fiber with several single-mode optical fibers through the optical fiber coupling device 22, and each core can transmit light independently. The core distribution of the multi-core optical fiber 23 is designed as follows: when observing the end face of the optical fiber, all the outer ring cores are geometrically circularly symmetrically distributed, and the single center core is located at the center of the end face. In this scheme, several single-mode optical fiber ports 21 connected to the outer ring cores are used to input light, and the single-mode optical fiber port 26 connected to the center core is used to output light. Selecting whether the light source of each core is passed can control the generation of the required structured scalar light field 3.

[0041] As shown in Figure 3, a schematic diagram of the interaction between rotating particles and the structured scalar light field generated by a multi-core optical fiber provided by an embodiment of the present invention includes: a multi-core optical fiber output port 24, an optical fiber collimator 25, a structured scalar light field 3, rotating particles 4, and a return signal 5. The light field of each outer ring core outputted from the multi-core optical fiber output port 24 passes through the optical fiber collimator 25 to form a structured scalar light field 3. The rotating particles 4 rotate (with an angular velocity of Ω). Under the illumination of the structured scalar light field 3, the center of revolution of the rotating particles 4 coincides with the optical axis of the structured scalar light field 3. The motion trajectory of the rotating particles 4 is located in an area with a high density of the structured scalar light field 3. The size of the rotating particles 4 is smaller than the spot size of the structured scalar light field 3. During the interaction process, the rotating particles 4 locally reflect part of the light field, generating a signal with an intensity that varies with time, namely the return signal 5.

[0042] As shown in Figure 4, the schematic diagram of the return signal detection device provided by an embodiment of the present invention includes: an optical fiber coupling device 22, a multi-core optical fiber 23 of a certain length, a multi-core optical fiber output port 24, an optical fiber collimator 25, a single-mode optical fiber port 26 connected to the central core, a return signal 5 to be detected, a photodetector 61, and a signal processing module 62. The return signal 5 to be detected is collected by the optical fiber collimator 25, and the returned signal light converges to the multi-core optical fiber output port 24 and is received by the central core of the multi-core optical fiber. At this time, the multi-core optical fiber output port 24 is the return signal receiving port. The return signal is sequentially transmitted through the multi-core optical fiber 23, the optical fiber coupling device 22, output by the single-mode optical fiber port 26 connected to the central core, received by the photodetector 61 and photoelectrically converted, and the electrical signal converted by the photodetector 61 is transmitted by the radio frequency line to the signal processing module 62 for Fourier analysis.

[0043] As shown in Figure 5, the multi-core optical fiber provided by the embodiment of the present invention generates a symmetrical scalar light field to detect rotating particles. When the rotating speed of the rotating particles is Ω = 40πrad / s, (a) in Figure 5 is the detected time domain signal, and (b) is the detected Fourier amplitude spectrum; when the rotating speed of the rotating particles is Ω = 80πrad / s, (c) in Figure 5 is the detected time domain signal, and (d) is the detected Fourier amplitude spectrum; (e) is the variable speed measurement result, showing the linear relationship between the detected signal frequency and the rotation speed. Among them, the detection light used in this result is a symmetrical light field, which is formed by selecting six circularly symmetrical outer ring cores of the seven-core optical fiber to pass light and controlling the light power to be the same. The rotational symmetry of the symmetrical scalar light field is S R=6. As shown in Figure 6, the detection results of rotating particles using a geometrically asymmetric scalar light field generated by a multi-core optical fiber are shown. When the rotating particle's rotation speed is Ω = 40πrad / s and the rotation direction is counterclockwise, (a) in Figure 6 is the detected time domain signal, (b) is the detected Fourier amplitude spectrum, and (c) is the detected Fourier phase spectrum. When the rotating particle's rotation speed is Ω = 40πrad / s and the rotation direction is clockwise, (d) in Figure 6 is the detected time domain signal, (e) is the detected Fourier amplitude spectrum, and (f) is the detected Fourier phase spectrum. The detection light used in this result is a geometrically asymmetric light field, which is generated by selecting three asymmetric outer ring cores of the seven-core optical fiber to pass light and controlling the optical power to be the same. As shown in Figure 7, the detection results of rotating particles using an intensity-asymmetric scalar light field generated by a multi-core optical fiber are shown. When the rotating speed of the rotating particle is Ω=40πrad / s and the rotation direction is counterclockwise, (a) in Figure 7 is the detected time domain signal, (b) is the detected Fourier amplitude spectrum, and (c) is the detected Fourier phase spectrum; when the rotating speed of the rotating particle is Ω=40πrad / s and the rotation direction is clockwise, (d) in Figure 7 is the detected time domain signal, (e) is the detected Fourier amplitude spectrum, and (f) is the detected Fourier phase spectrum. Among them, the detection light used in this result is an intensity asymmetric light field, which is formed by selecting two symmetrical outer ring cores of the seven-core optical fiber to pass light and controlling the light power to be different. From the measurement results of the symmetric scalar light field, it can be seen that the rotational symmetry of the symmetric scalar light field is S R =6, when the rotation speed doubles, the peak frequency of the Fourier amplitude spectrum will also double, and the peak frequency has a linear relationship with the rotation speed For the measurement results of asymmetric scalar light fields, regardless of whether the detection light field is a geometrically asymmetric scalar light field or an intensity asymmetric scalar light field, at a fixed particle rotation speed, the detected Fourier amplitude spectrum has several peak frequency components, where |f1| and |f2| are the first peak frequency and the second peak frequency, respectively, and |Δf 1,2 The difference between the two is related to the angular velocity of rotation. The difference in the Fourier relative phase spectra for the two rotational directions in Figures 6 (c) and (f) shows that when the anisotropic rotational motion reverses direction, the sign of the relative phase difference corresponding to the two peak frequency components reverses, allowing the signs of the two peak frequencies to be determined. Using the relationship between the two peak frequency intervals and the angular velocity of rotation, the magnitude and direction of the angular velocity of the rotating particle can be calculated. Similarly, the difference in the Fourier relative phase spectra for the two rotational directions in Figures 7 (c) and (f) shows that when the anisotropic rotational motion reverses direction, the sign of the relative phase difference corresponding to the two peak frequency components also reverses, allowing the magnitude and direction of the angular velocity of the rotating particle to be calculated.

[0044] The present invention is not limited to the above-mentioned specific embodiments. A person skilled in the art can implement the present invention in a variety of other specific embodiments based on the contents disclosed in the present invention. Therefore, any design that adopts the design structure and ideas of the present invention and makes some simple changes or modifications falls within the scope of protection of the present invention.

Claims

1. A vector rotation speed measurement method based on a multi-core optical fiber, characterized in that, it includes: The multiplexed optical inputs form a scalar optical field with a structured non-uniform spatial distribution through non-uniform spatial transmission. The scalar optical field is used as a detection light to collimate and irradiate the rotating moving particles. The rotating moving particles reflect the signal light carrying the motion information. The Fourier analysis is performed on the signal light to obtain the Fourier amplitude spectrum and the phase spectrum. The magnitude of the velocity of the rotating moving particles is calculated through the frequency peaks in the Fourier amplitude spectrum, and the direction of the velocity of the rotating moving particles is calculated and inferred by using the relative phase difference corresponding to the Fourier phase spectrum, so as to realize the measurement of the vector rotating moving particles based on the multi-core optical fiber.

2. The speed measurement method according to claim 1, characterized in that, The frequency peaks are taken in ascending order of peak frequency, and the first two are: the first frequency peak and the second frequency peak, and the peak frequencies are respectively First frequency peak: Second frequency peak: where Ω is the angular velocity of the rotating microparticle, and the subtraction of the two peak frequencies gives The magnitude of the moving speed of the rotating particles is calculated.

3. The speed measurement method according to claim 2, characterized in that, Obtain the phase corresponding to the first frequency peak in the Fourier phase spectrum and the phase corresponding to the second frequency peak Calculate the relative phase difference between the first frequency peak and the second frequency peak Determine the direction of the velocity of the rotating moving particle according to the sign of the relative phase difference 4. A vector rotation speed measurement device based on a multi-core optical fiber, characterized in that, it includes: A light source, a fan-in / fan-out module, a multi-core optical fiber, a probe, and a detection device; wherein, the light source is used to emit multiplexed optical light, which is received by the outer ring fiber cores that pass through the multi-core optical fiber selected by the fan-in / fan-out module to generate a scalar optical field with a structured non-uniform spatial distribution. The multi-core optical fiber is used to transmit the scalar optical field. The scalar optical field passes through the probe and irradiates the rotating moving particles as a detection light. The rotating moving particles reflect the signal light carrying the motion information. The signal light passes through the probe and is collected into the central fiber core of the multi-core optical fiber. The signal light is then connected to the detection device through the fan-in / fan-out module. The detection device performs Fourier analysis on the signal light to obtain the Fourier amplitude spectrum and the phase spectrum. The magnitude of the velocity of the rotating moving particles is calculated through the frequency peaks in the Fourier amplitude spectrum, and the direction of the velocity of the rotating moving particles is calculated and inferred by using the relative phase difference corresponding to the Fourier phase spectrum, so as to realize vector rotation speed measurement based on the multi-core optical fiber.

5. The speed measurement device according to claim 4, characterized in that, The multi-core optical fiber includes: a central fiber core, which is arranged at the central position of the multi-core optical fiber; outer ring fiber cores, which are arranged in a circle around the central fiber core, and the distance between each outer ring fiber core and the central fiber core, as well as between each outer ring fiber core, is equal. There is no crosstalk or weak crosstalk in the energy transmitted between the central fiber core and any one outer ring fiber core, as well as between each outer ring fiber core; part of the asymmetric outer ring fiber cores are selected by the fan-in / fan-out module to pass through light to form a detection optical field.

6. The speed measurement device according to claim 4, characterized in that, The multi-core optical fiber includes: a central core disposed at the center of the multi-core optical fiber; outer ring cores disposed around the central core, and the distances between each outer ring core and the central core, as well as between each outer ring core, are not equal. There is no crosstalk or weak crosstalk in the energy transmitted between the central core and any one outer ring core, as well as between each outer ring core. The probe optical field is formed by selecting all the outer ring cores to transmit light through the fan-in / fan-out module.

7. The speed measurement device according to claim 4, wherein, the scalar optical field is a geometrically asymmetric optical field, the optical power provided to the core is uniform, and the outer ring cores transmitting light are in an asymmetric form in terms of spatial geometry.

8. The speed measurement device according to claim 4, wherein, the scalar optical field is an intensity-asymmetric optical field, the optical power provided to the core is non-uniform, the outer ring cores transmitting light are in an asymmetric form in terms of spatial intensity distribution, and in terms of spatial geometry, it is in other forms except for being axisymmetric along the diameter of the fiber end face.

9. The speed measurement device according to claim 4, wherein, the light source is a single laser, and multiple identical homogenous lights are output after beam splitting and are connected to the multi-core optical fiber. The number of the multiple lights matches the number of the outer ring cores transmitting light.

10. The speed measurement device according to claim 4, wherein, the light source is multiple lasers, and multiple lights output are connected to the multi-core optical fiber as multiple lights. The number of the multiple lights matches the number of the outer ring cores transmitting light.

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