A micro distance measuring device and method based on a multi-core optical fiber

Abstract

The application provides a kind of micro distance measuring device and method based on multi-core optical fiber, belongs to non-contact optical measurement technical field.Micro distance measuring device is by wide spectrum light source, optical circulator, double-core fiber fan-in fan-out module, double-core fiber probe, first optical power meter, second optical power meter and host computer composition.According to the numerical value p1, p2 measured by two optical power meters of micro distance measuring device, and the light intensity loss coefficient of optical circulator, the host computer can directly calculate the distance between the double-core fiber probe and the measured object.The measuring method of the application is directly using power ratio to measure distance, which can eliminate the influence of light source power fluctuation and the reflectivity of measured object surface on micro distance measurement result.

Description

Technical Field

[0001] This invention relates to the field of non-contact optical measurement, and more particularly to a device and method for measuring minute distances based on multi-core optical fibers. Background Technology

[0002] Non-contact optical technology is widely used in measuring minute distances between objects. Among them, fiber-optic reflective measurement technology benefits from the small size of optical fibers and its immunity to electromagnetic interference, making it a highly promising measurement technology for high-temperature or strong electromagnetic field environments, hazardous or explosive environments, and biomedical applications. The basic working principle of this technology is as follows: the measuring device guides light from a fixed optical fiber to the object to be measured at a minute distance and detects the amount of light reflected from the object. This working principle also presents the following problems: determining the minute distance of an object is based on the absolute value of the reflected light intensity; however, the absolute value of reflected light intensity is easily affected by factors such as fluctuations in light source intensity, the material of the measured object's surface, and the reflection characteristics, leading to measurement errors. Traditional measuring or sensing devices use multiple optical fibers or fiber bundles spliced ​​together to form fiber optic probes or heads. Due to differences between different optical fibers and errors in the splicing process, the measurement error is further increased. Furthermore, the size of the probe or head cannot be effectively reduced.

[0003] Multicore fiber is a novel type of microstructured fiber characterized by having multiple cores within its cladding, whereas traditional optical fibers have only one core. A single multicore fiber can replace multiple traditional single-core fibers or fiber bundles, offering a more compact structure, smaller size, and lower cost. Furthermore, because the cores in multicore fibers are pre-stretched, their uniformity and neatness are superior to those of spliced ​​fiber bundles. Using multicore fibers as probes or sensors instead of traditional fiber bundles results in more accurate measurements, especially over minute distances. Summary of the Invention

[0004] In view of this, the present invention provides a micro-distance measurement device and method based on multi-core optical fiber, which uses the ratio of received and reflected light power of different cores in the multi-core optical fiber to measure distance, thereby eliminating the influence of differences in optical fiber parameters, fluctuations in light source power, and the surface reflectivity of the object being measured on the micro-distance measurement results.

[0005] The technical solution adopted by the embodiments of the present invention to solve its technical problem is as follows:

[0006] A micro-distance measurement device based on multi-core optical fiber comprises a broadband light source (1), an optical circulator (2), a dual-core optical fiber fan-in / fan-out module (3), a multi-core optical fiber probe (4), a first optical power meter (5), a second optical power meter (6), and a host computer (8). The outgoing optical path starts from the broadband light source (1), enters the first port of the optical circulator (2), exits from the second port of the optical circulator (2), enters the first fiber core (4-1) of the multi-core optical fiber probe (4) through the dual-core optical fiber fan-in / fan-out module (3), and exits to the object being detected (7). The reflected light from the object being detected (7) is transmitted through two incident optical paths. The first incident optical path is formed by the first... The fiber core (4-1) receives reflected light, enters the second port of the optical circulator (2) through the dual-core fiber fan-in / fan-out module (3), and enters the first optical power meter (5) from the third port of the optical circulator (2); the second incident light path is the second fiber core (4-2) of the multi-core fiber probe (4) receiving reflected light, entering the second optical power meter (6) through the dual-core fiber fan-in / fan-out module (3); the first optical power meter (5) and the second optical power meter (6) convert the input optical signal into an electrical signal representing power and output it to the host computer (8), and the host computer calculates the distance between the object being detected (7) and the multi-core fiber probe (4).

[0007] Preferably, the multi-core fiber optic probe (4) has at least two fiber cores; the structure of the multi-core fiber optic probe (4) from the inside out is as follows: each fiber core located at the center, a cladding (4-3) covering the fiber core, a coating (4-4) applied to the cladding, and a protective shell (4-5) outside the coating.

[0008] Preferably, the broadband light source (1) is connected to the first port of the optical circulator (2) via optical fiber, the dual-core fiber fan-in / fan-out module (3) is connected to the second port of the optical circulator (2), the second optical power meter (6), the first fiber core (4-1) of the multi-core fiber probe (4), and the second fiber core (4-2) of the multi-core fiber probe (4) via optical fiber, the third port of the optical circulator (2) is connected to the first optical power meter (5) via optical fiber, and the first optical power meter (5), the second optical power meter (6) are electrically connected to the host computer (8).

[0009] Preferably, the distance between the object being detected (7) and the multi-core fiber optic probe (4) is s, and the relationship between the ratio of the power p1 measured by the first optical power meter (5) and the power p2 measured by the second optical power meter (6) and s satisfies:

[0010] p1=p0α c α m1 α rα m1 α c f(s,d1)

[0011] p2=p0α c α m1 α r α m2 f(s,d2)

[0012]

[0013] In the formula, p0 is the intensity of the broadband light source (1), α c α is the light intensity loss coefficient of the optical circulator (2). m1 α is the light intensity loss coefficient through the dual-core fiber fan-in / fan-out module (3) and the first fiber core (4-1). r Let f(s,d1) be the influence coefficient of the reflectivity of the object's surface, and f(s,d1) be a function of s and d1; α m2 Let d1 be the light intensity loss coefficient of the dual-core fiber fan-in / fan-out module (3) and the second fiber core (4-2). d1 refers to the distance between the first fiber core (4-1) that emits the outgoing light and the first fiber core (4-1) that receives the reflected light in the first receiving optical path; d2 refers to the distance between the first fiber core (4-1) that emits the outgoing light and the second fiber core (4-2) that receives the reflected light in the second receiving optical path; f(s,d2) is a function of s and d2; considering the consistency of the multi-core fiber height, let α... m1 =α m2 This yields the simplified expression for p2 / p1.

[0014] Preferably, a reference object is selected, a distance measurement experiment is preset and tested, and the test data is recorded. A set of test data consists of a preset distance s and the measured power values ​​p1 and p2. The host computer (8) obtains a two-dimensional correlation curve between s and p2 / p1 by plotting the curve of s and p2 / p1 and performing curve fitting. The value of s corresponding to max(p2 / p1) on the vertical axis of the two-dimensional correlation curve is selected as x1. Accordingly, the interval [0, x1] on the horizontal axis of the two-dimensional correlation curve is defined as the uphill section, and the interval (x1, +∞) is the downhill section.

[0015] Preferably, the micro-distance measuring device is configured with two measurement schemes, including a high-sensitivity measurement scheme and a high dynamic range measurement scheme, and one of them is selected for use in a single measurement;

[0016] The curve located on the downhill section is gentler and has a wider range than the curve located on the uphill section. Therefore, the high-sensitivity measurement scheme finds the s value corresponding to p2 / p1 in the uphill section, with a corresponding range of [0, x1]. The high dynamic range measurement scheme finds the s value corresponding to p2 / p1 in the downhill section, with a corresponding range of (x1, +∞).

[0017] The present invention also provides a ranging method using the aforementioned micro-distance measuring device based on multi-core optical fiber. The ranging steps using the aforementioned micro-distance measuring device include:

[0018] Step S1: Install the micro-distance measuring device and determine the light intensity loss coefficient α of the optical circulator (2). c And the distance L between the two fiber cores used to receive reflected light;

[0019] Step S2: Select a reference object, set up a distance measurement test and conduct the test, and record the test data. A set of test data consists of a preset distance s and the measured power values ​​p1 and p2, where p1 is the data measured by the first optical power meter (5) and p2 is the data measured by the second optical power meter (6).

[0020] Step S3: Based on the experimental data, plot the curve s versus p2 / p1 and perform curve fitting to obtain a two-dimensional correlation curve between s and p2 / p1.

[0021] Step S4: Select the s value corresponding to max(p2 / p1) on the vertical axis of the two-dimensional correlation curve as x1. Accordingly, define the interval [0,x1] on the horizontal axis of the two-dimensional correlation curve as the upslope segment and the interval (x1,+∞) as the downslope segment.

[0022] Step S5: Use the micro-distance measuring device to measure distance and find the s value corresponding to p2 / p1 based on the two-dimensional correlation curve. A single measurement is applicable to a single measurement scheme, which includes a high-sensitivity measurement scheme and a high dynamic range measurement scheme.

[0023] Preferably, the high-precision measurement scheme finds the s value corresponding to p2 / p1 in the uphill section, with a corresponding range of [0, x1]; the long-distance measurement scheme finds the s value corresponding to p2 / p1 in the downhill section, with a corresponding range of (x1, +∞).

[0024] Preferably, step S5 includes:

[0025] Step S51: Move the micro-distance measuring device back and forth in front of the object to be measured, and find the position of max(p2 / p1) based on the slope change of p2 / p1.

[0026] Step S52: Select a measurement scheme, wherein the measurement scheme is one of a high-sensitivity measurement scheme and a high dynamic range measurement scheme;

[0027] Step S53: Perform a measurement within the range corresponding to the measurement scheme, and find the s value corresponding to p2 / p1 based on the two-dimensional correlation curve.

[0028] As can be seen from the above technical solution, the micro-distance measurement device and method based on multi-core optical fiber provided in this embodiment of the invention comprises a broadband light source, an optical circulator, a dual-core optical fiber fan-in / fan-out module, a dual-core optical fiber probe, a first optical power meter, a second optical power meter, and a host computer. Based on the values ​​p1 and p2 measured by the two optical power meters of the micro-distance measurement device, and the optical intensity loss coefficient of the optical circulator, the host computer can directly calculate the distance between the dual-core optical fiber probe and the object being measured. This invention uses a more integrated multi-core optical fiber probe and utilizes the ratio of received and reflected light power of different cores in the multi-core optical fiber for distance measurement, eliminating the influence of differences in fiber parameters, fluctuations in light source power, and the surface reflectivity of the object being measured on the micro-distance measurement results, thus expanding the applicability of the measurement and improving the accuracy and precision of micro-distance measurement. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the micro-distance measurement device based on multi-core optical fiber according to the present invention.

[0030] In the diagram: 1 is a broadband light source, 2 is an optical circulator, 3 is a multi-core fiber fan-in / fan-out module, 4 is a multi-core fiber probe, 5 is an optical power meter, 6 is an optical power meter, 7 is the object under test, and 8 is the host computer.

[0031] Figure 2 This is a schematic diagram of the structure of a multi-core fiber optic probe.

[0032] In the diagram: 4-1 is the first fiber core, 4-2 is the second fiber core, 4-3 is the cladding, 4-4 is the coating, and 4-5 is the protective shell.

[0033] Figure 3 This is a magnified schematic diagram of a multi-core fiber optic probe and the object under test.

[0034] In the figure: the minute distance between the first fiber core 4-1 and the second fiber core 4-2 is L; the minute distance between the probe end face and the object being measured is s.

[0035] Figure 4(a) shows the output signal power of the light source, which is p 01 p 02 At that time, the output p1 of optical power meter 5 and the output p2 of optical power meter 6;

[0036] Figure 4(b) shows the output signal power of the light source as p 01 p02 When, the ratio of p2 / p1 is as follows.

[0037] Figure 5(a) shows the influence coefficients of the reflectivity of the object surface, α r1 α r2 At that time, the output p1 of optical power meter 5 and the output p2 of optical power meter 6;

[0038] Figure 5(b) shows the influence coefficients of the reflectivity of the object surface, α r1 α r2 When, the ratio of p2 / p1 is as follows. Detailed Implementation

[0039] The technical solution and effects of the present invention will be further described in detail below with reference to the accompanying drawings.

[0040] Please refer to Figure 1-3 The micro-distance measuring device provided by this invention comprises a broadband light source 1, an optical circulator 2, a dual-core fiber fan-in / fan-out module 3, a multi-core fiber probe 4, a first optical power meter 5, a second optical power meter 6, and a host computer 8. Based on the values ​​p1 and p2 measured by the two optical power meters in the micro-distance measuring device, and the light intensity loss coefficient of the optical circulator, the host computer can directly calculate the distance between the dual-core fiber probe and the object being measured. The measurement method of this invention utilizes the power ratio for distance measurement, which can eliminate the influence of differences in light source intensity and differences in the reflective surface of different targets on the micro-distance measurement results.

[0041] Figure 1 In the configuration, the broadband light source 1 is connected to port 1 of the optical circulator 2 via optical fiber. The dual-core fiber fan-in / fan-out module 3 is connected to port 2 of the optical circulator 2, the second optical power meter 6, the first fiber core 4-1 of the multi-core fiber probe 4, and the second fiber core 4-2 of the multi-core fiber probe 4 via optical fiber. The third port of the optical circulator 2 is connected to the first optical power meter 5 via optical fiber. The first optical power meter 5, the second optical power meter 6, and the host computer 8 are electrically connected.

[0042] Structural example of multi-core fiber optic probe 4 (reference) Figure 2 The multi-core fiber optic probe 4 has at least two fiber cores; the structure of the multi-core fiber optic probe 4 from the inside out consists of: each fiber core located at the center, a cladding 4-3 covering the fiber cores, a coating 4-4 ​​applied to the cladding, and a protective shell 4-5 outside the coating. Figure 2 The image shows a dual-core fiber optic probe. This invention is applicable not only to dual-core and multi-core optical fibers, but also to multi-core optical fibers with more cores. The multi-core fiber optic probe 4 can have multiple cores, and two of them are selected as the first core 4-1 and the second core 4-2. Therefore, the number of cores in the multi-core fiber optic probe 4 is greater than or equal to 2.

[0043] like Figure 1 As shown, the outgoing optical path starts from the broadband light source 1, enters port 1 of the optical circulator 2, exits from port 2 of the optical circulator 2, passes through the dual-core fiber fan-in / fan-out module 3, enters the first fiber core 4-1 of the multi-core fiber optic probe 4, and exits to the object being detected 7. The reflected light from the object being detected 7 is transmitted through two incident optical paths. The first incident optical path is where the first fiber core 4-1 receives the reflected light, passes through the dual-core fiber fan-in / fan-out module 3 to enter port 2 of the optical circulator 2, and enters the first optical power meter 5 from port 3 of the optical circulator 2. The second incident optical path is where the second fiber core 4-2 of the multi-core fiber optic probe 4 receives the reflected light, passes through the dual-core fiber fan-in / fan-out module 3, and enters the second optical power meter 6. The first optical power meter 5 and the second optical power meter 6 convert the input optical signal into an electrical signal representing the power and output it to the host computer 8, which calculates the distance between the object being detected 7 and the multi-core fiber optic probe 4.

[0044] In the device of the present invention, a broadband light source, such as LED or fluorescent lamp, is used as the light source. Compared with a narrow-spectrum light source, this can avoid the interference fringes caused by interference phenomena affecting the accuracy of the reflected light power value measurement.

[0045] The micro-distance measuring device is equipped with two measurement schemes, including a high-sensitivity measurement scheme and a high dynamic range measurement scheme. One of them can be used for a single measurement. The high-sensitivity measurement scheme corresponds to the range [0, x1], and the high dynamic range measurement scheme corresponds to the range (x1, +∞).

[0046] Furthermore, utilizing Figure 1 The method for measuring distance using the micro-distance measuring device shown is as follows:

[0047] Step S1: Install the micro-distance measuring device to determine the light intensity loss coefficient α of the optical circulator (2). c And the distance L between the two fiber cores used to receive reflected light;

[0048] Step S2: Select a reference object, set up a distance measurement test and conduct the test, and record the test data. A set of test data consists of a preset distance s and the measured power values ​​p1 and p2, where p1 is the data measured by the first optical power meter (5) and p2 is the data measured by the second optical power meter (6).

[0049] Step S3: Plot the curve s versus p2 / p1 based on the experimental data and perform curve fitting to obtain the two-dimensional correlation curve between s and p2 / p1.

[0050] Step S4: Select the s value corresponding to max(p2 / p1) on the vertical axis of the two-dimensional correlation curve as x1. Accordingly, define the interval [0,x1] on the horizontal axis of the two-dimensional correlation curve as the upslope segment and the interval (x1,+∞) as the downslope segment.

[0051] Step S5: Distance measurement is performed using a micro-distance measuring device. Based on the two-dimensional correlation curve, the s value corresponding to p2 / p1 is found. A single measurement is applicable to a single measurement scheme, which includes a high-sensitivity measurement scheme and a high dynamic range measurement scheme. The curve located on the downhill section is flatter and has a wider range than the curve located on the uphill section. Therefore, the high-sensitivity measurement scheme finds the s value corresponding to p2 / p1 within the uphill section, with a range of [0, x1]. The high dynamic range measurement scheme finds the s value corresponding to p2 / p1 within the downhill section, with a range of (x1, +∞).

[0052] The specific implementation method of step S5 is as follows: Move the micro-distance measuring device back and forth in front of the object to be measured, and find the position of max(p2 / p1) (referring to the actual position of the micro-distance measuring device) based on the slope change of p2 / p1; according to the selected measurement scheme, perform the measurement within the range corresponding to the measurement scheme, and find the s value corresponding to p2 / p1 based on the two-dimensional correlation curve. If a high-sensitivity measurement scheme is to be used, the measurement is performed within the range [0, x1]; if a high dynamic range measurement scheme is to be used, the measurement is performed within the range (x1, +∞). Additionally, because light reflection reception may be interfered with, the device may not be able to measure p1 and p2 simultaneously, in which case the measurement scheme using p2 / p1 of this invention cannot be executed.

[0053] In this invention, the expressions for p1 and p2 are defined as follows:

[0054] p1=p0α c α m1 α r α m1 α c f(s,d1) (1)

[0055] p2=p0α c α m1 α r α m2 f(s,d2) (2)

[0056] In the formula, p0 is the intensity of broadband light source 1, and α c Let α be the light intensity loss coefficient of optical circulator 2. m1 To determine the optical intensity loss coefficient α through the dual-core fiber fan-in / fan-out module 3 and the first fiber core 4-1, r Let α be the influence coefficient of the reflectivity of the object surface, the center-to-center distance between the first fiber core 4-1 and the second fiber core 4-2 be L, and d1 be the distance between the first fiber core 4-1 that emits outgoing light and the first fiber core 4-1 that receives reflected light in the first receiving optical path. We can consider d1 = 0. m2Let d2 be the optical intensity loss coefficient of the dual-core fiber fan-in / fan-out module 3 and the second fiber core 4-2. d2 refers to the distance between the first fiber core 4-1 that emits the outgoing light and the second fiber core 4-2 that receives the reflected light in the second receiving optical path; d2 can be considered as d2 = L. f(s,d1) is a function of s and d1, and f(s,d2) is a function of s and d2.

[0057] The expression for the optical power ratio p2 / p1 is:

[0058]

[0059] Considering the consistency of the height of multi-core optical fibers, let α m1 =α m2 The expression for the optical power ratio p2 / p1 can be simplified to:

[0060]

[0061] Equation (4) shows that for a given optical system, α c Since d1 and d2 are all definite constants, the ratio p2 / p1 is only a function of the small distance s between the fiber end face and the object, and is independent of the characteristics of the light source and the reflectivity of the target. Therefore, using the power ratio method can effectively avoid the influence of fluctuations in the power of the light source and the different reflectivities of the surface of the measured object on the measurement results.

[0062] Step S2 involves conducting experiments and measurements, with the data used to plot graphs. A reference object is selected, a preset distance measurement experiment is performed, and the experimental data is recorded. A set of experimental data consists of a preset distance *s* and measured power values ​​*p1* and *p2*. For example, design a set of predicted distances {0 μm, 10 μm, ...}. First, place the probe against the object surface; at this point, the distance *s* is 0 μm. Record *p1* and *p2*, and calculate *p2* / *p1*. Mark the position of this point on the graph (x-axis is 0, y-axis is *p2* / *p1*). Then, move the probe 10 μm; at this point, the distance *s* is 10 μm. Record *p1* and *p2*, and calculate *p2* / *p1*. Mark the position of this point on the graph (x-axis is 10, y-axis is *p2* / *p1*). Refer to the schematic diagram of the measurement results:

[0063] Figures 4(a) and 4(b) are schematic diagrams showing the relationship between output and small distance when the power of the light source signal is different.

[0064] In Figure 4(a), with the small distance s remaining constant, when the intensity of the broadband light source 1 is p 01 p 02At that time, the optical signal power value p1 (one reflected optical signal received by fiber core 4-1) measured by optical power meter 5 was not the same (reflected as two curves with large differences), indicating that the change in light source intensity would lead to the change in measurement results (the optical signal power value p2 measured by optical power meter 6 also conforms to the above situation). However, in reality, the tiny distance s between the probe and the object being measured did not change, and the cause of the change was the change in the light source signal intensity. Therefore, the measurement was incorrect.

[0065] In Figure 4(b), with the small distance s remaining constant, when the intensity of the broadband light source 1 is p 01 p 02 At the same time, observing the ratio p2 / p1 of the optical signal power value p1 (one reflected optical signal received by fiber core 4-1) measured by optical power meter 5 and the optical signal power value p2 (one reflected optical signal received by fiber core 4-2) measured by optical power meter 6, it can be seen that the value of p2 / p1 is the same (theoretically, this is reflected as the two curves coinciding), and it does not differ due to the intensity change of broadband light source 1. This proves that the present invention effectively overcomes the influence of light source intensity fluctuations on the measurement results.

[0066] Figures 5(a) and 5(b) show the influence coefficients of surface reflectance α when the measured object or the surface of the measured object is different. r1 α r2 Output a schematic diagram showing the relationship between small distances.

[0067] In Figure 5(a), with the small distance s remaining constant, when different objects are selected or the surface reflectivity of the objects is different, let their reflectivity influence coefficients be α respectively. r1 α r2 The optical signal power values ​​measured by optical power meter 5 (one reflected optical signal received by fiber core 4-1) are not the same (reflected by two curves with large differences), indicating that different measured objects or changes in the reflectivity of the measured object's surface will lead to changes in the measurement results (the optical signal power values ​​measured by optical power meter 6 also conform to the above situation). However, in reality, the tiny distance s between the probe and the measured object does not change; the cause of the change is the change in the reflectivity of the measured object. Therefore, the measurement is incorrect.

[0068] In Figure 5(b), with the small distance s remaining constant, when different objects are selected or the surface reflectivity of the objects is different, let their reflectivity influence coefficients be α. r1 α r2By observing the ratio p2 / p1 of the optical signal power value p1 (one reflected optical signal received by fiber core 4-1) measured by optical power meter 5 and the optical signal power value p2 (one reflected optical signal received by fiber core 4-2) measured by optical power meter 6, it can be seen that the value of p2 / p1 is the same (theoretically, this is reflected as the two curves coinciding), and it does not differ due to the change in reflectivity. This proves that the present invention effectively overcomes the influence of different reflectivities of different measured objects on the measurement results.

[0069] The advantages of this invention are: 1. The probe has a higher degree of integration, a more compact structure, and a smaller size; 2. It overcomes the influence of factors such as fluctuations in light source intensity, the material of the object being measured, and reflection on the measurement, thus expanding the applicable range of the measurement and improving the accuracy and precision of macro measurement.

[0070] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A micro-distance measuring device based on multi-core optical fiber, characterized in that, It consists of a broadband light source (1), an optical circulator (2), a dual-core fiber fan-in / fan-out module (3), a multi-core fiber probe (4), a first optical power meter (5), a second optical power meter (6), and a host computer (8); the outgoing optical path starts from the broadband light source (1), enters the first port of the optical circulator (2), exits from the second port of the optical circulator (2), enters the first fiber core (4-1) of the multi-core fiber probe (4) through the dual-core fiber fan-in / fan-out module (3), and exits to the object being detected (7); the reflected light from the object being detected (7) is transmitted through two incident optical paths; the first incident optical path is received by the first fiber core (4-1). The reflected light enters the second port of the optical circulator (2) through the dual-core fiber fan-in / fan-out module (3) and enters the first optical power meter (5) from the third port of the optical circulator (2); the second incident light path is the second fiber core (4-2) of the multi-core fiber probe (4) receiving the reflected light, which enters the second optical power meter (6) through the dual-core fiber fan-in / fan-out module (3); the first optical power meter (5) and the second optical power meter (6) convert the input optical signal into an electrical signal representing the power and output it to the host computer (8), which calculates the distance between the object being detected (7) and the multi-core fiber probe (4); The distance between the object being detected (7) and the multi-core fiber optic probe (4) is s. The relationship between the ratio of the power p1 measured by the first optical power meter (5) and the power p2 measured by the second optical power meter (6) and s satisfies: p1=p0a c a m1 a r a m1 a c f(s,d1); p2=p0a c a m1 a r a m2 f(s,d2); ； In the formula, p0 is the intensity of the broadband light source (1), α c α is the light intensity loss coefficient of the optical circulator (2). m1 α is the light intensity loss coefficient through the dual-core fiber fan-in / fan-out module (3) and the first fiber core (4-1). r Let f(s,d1) be the influence coefficient of the reflectivity of the object's surface, and f(s,d1) be a function of s and d1; α m2 Let d1 be the light intensity loss coefficient of the dual-core fiber fan-in / fan-out module (3) and the second fiber core (4-2). d1 refers to the distance between the first fiber core (4-1) that emits the outgoing light and the first fiber core (4-1) that receives the reflected light in the first receiving optical path; d2 refers to the distance between the first fiber core (4-1) that emits the outgoing light and the second fiber core (4-2) that receives the reflected light in the second receiving optical path; f(s,d2) is a function of s and d2; considering the consistency of the multi-core fiber height, let α... m1 =α m2 This yields the simplified expression for p2 / p1; Select a reference object, set up a distance measurement test and conduct the test, record the test data. A set of test data consists of a preset distance s and the measured power values ​​p1 and p2. The host computer (8) draws a curve of s and p2 / p1 and performs curve fitting to obtain a two-dimensional correlation curve of s and p2 / p1. Select the s value corresponding to max(p2 / p1) on the vertical axis of the two-dimensional correlation curve as x1. Accordingly, define the interval [0,x1] on the horizontal axis of the two-dimensional correlation curve as the uphill section and the interval (x1,+∞) as the downhill section. The micro-distance measuring device is equipped with two measurement schemes, including a high-sensitivity measurement scheme and a high dynamic range measurement scheme, and one of them can be used for a single measurement. The curve located on the downhill section is gentler and has a wider range than the curve located on the uphill section. Therefore, the high-sensitivity measurement scheme finds the s value corresponding to p2 / p1 in the uphill section, with a corresponding range of [0, x1]. The high dynamic range measurement scheme finds the s value corresponding to p2 / p1 in the downhill section, with a corresponding range of (x1, +∞).

2. The micro-distance measuring device based on multi-core optical fiber as described in claim 1, characterized in that, The multi-core fiber optic probe (4) has at least two fiber cores; the structure of the multi-core fiber optic probe (4) from the inside out is as follows: each fiber core located at the center, a cladding (4-3) covering the fiber core, a coating (4-4) applied to the cladding, and a protective shell (4-5) outside the coating.

3. The micro-distance measuring device based on multi-core optical fiber as described in claim 2, characterized in that, The broadband light source (1) is connected to the first port of the optical circulator (2) via optical fiber. The dual-core fiber fan-in / fan-out module (3) is connected to the second port of the optical circulator (2), the second optical power meter (6), the first fiber core (4-1) of the multi-core fiber probe (4), and the second fiber core (4-2) of the multi-core fiber probe (4) via optical fiber. The third port of the optical circulator (2) is connected to the first optical power meter (5) via optical fiber. The first optical power meter (5), the second optical power meter (6), and the host computer (8) are electrically connected.

4. A ranging method using the aforementioned micro-distance measuring device based on multi-core optical fiber, characterized in that, Using the micro-distance measuring device according to any one of claims 1-3, the distance measuring step includes: Step S1: Install the micro-distance measuring device and determine the light intensity loss coefficient α of the optical circulator (2). c And the distance L between the two fiber cores used to receive reflected light; Step S2: Select a reference object, set up a distance measurement test and conduct the test, and record the test data. A set of test data consists of a preset distance s and the measured power values ​​p1 and p2, where p1 is the data measured by the first optical power meter (5) and p2 is the data measured by the second optical power meter (6). Step S3: Based on the experimental data, plot the curve s versus p2 / p1 and perform curve fitting to obtain a two-dimensional correlation curve between s and p2 / p1. Step S4: Select the s value corresponding to max(p2 / p1) on the vertical axis of the two-dimensional correlation curve as x1. Accordingly, define the interval [0,x1] on the horizontal axis of the two-dimensional correlation curve as the upslope segment and the interval (x1,+∞) as the downslope segment. Step S5: Use the micro-distance measuring device to measure distance and find the s value corresponding to p2 / p1 based on the two-dimensional correlation curve. A single measurement is applicable to a single measurement scheme, which includes a high-sensitivity measurement scheme and a high dynamic range measurement scheme.

5. The ranging method using the micro-distance measuring device based on multi-core optical fiber as described in claim 4, characterized in that, The high-sensitivity measurement scheme finds the s value corresponding to p2 / p1 in the uphill section, with a corresponding range of [0, x1]; the high dynamic range measurement scheme finds the s value corresponding to p2 / p1 in the downhill section, with a corresponding range of (x1, +∞).

6. The ranging method using the micro-distance measuring device based on multi-core optical fiber as described in claim 5, characterized in that, Step S5 includes: Step S51: Move the micro-distance measuring device back and forth in front of the object to be measured, and find the position of max(p2 / p1) based on the slope change of p2 / p1. Step S52: Select a measurement scheme, wherein the measurement scheme is one of a high-sensitivity measurement scheme and a high dynamic range measurement scheme; Step S53: Perform a measurement within the range corresponding to the measurement scheme, and find the s value corresponding to p2 / p1 based on the two-dimensional correlation curve.

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