Device and method for calibrating optical fiber end face distance based on gradient ceramic ferrule

Abstract

The present invention belongs to the technical field of optical coherence tomography. A device and method for calibrating the end face distance of an optical fiber based on a gradient ceramic ferrule are provided, the internal structure of the ceramic ferrule is improved, and a diameter gradient ceramic ferrule is produced, which can make it easier for the optical fiber to enter the interior of the ceramic ferrule, facilitate its center alignment, and also facilitate the movement of the displacement optical fiber and can also achieve the effect of reducing radial runout during rotation; a method for calibrating the end face distance of an optical fiber based on a gradient ceramic ferrule is designed, and the same evaluation but different coefficients are selected according to different application scenarios. By comparing the size of the evaluation result value, the optimal end face distance is intuitively obtained, which greatly improves the evaluation efficiency and evaluation accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of optical coherence tomography, and in particular to a device and method for calibrating the distance between optical fiber end faces based on a gradient ceramic ferrule. Background Art

[0002] The statements in this section merely provide background art related to the present invention and do not necessarily constitute prior art.

[0003] OCT (Optical Coherence Tomography) is a non-contact, non-invasive optical imaging diagnostic technology that uses the basic principle of weak coherent light interferometer to construct a two-dimensional or three-dimensional structural image of biological tissue by detecting the back-reflected or several scattered signals of incident weak coherent light at different depths of biological tissue. This technology can provide images of tissue reflectivity as a function of depth and lateral position on the sample, with extremely high resolution and imaging depth.

[0004] With the development of science and technology and the medical needs of human society, endoscopic technology based on the OCT principle is increasingly widely used in the detection of pathological structures inside the human body. The main technical approach is to project and focus the OCT imaging beam onto the internal tissues of the human body through an endoscope, scan and collect the back-reflected light from the tissues, and then transmit it back to the OCT interferometer for image processing. This technology can obtain high-resolution cross-sectional images of tissues, provide information about microscopic architectural morphology, and help doctors accurately diagnose and evaluate lesions.

[0005] However, when designing this endoscope based on OCT technology, the fiber optic rotary connector is an important component. The fiber optic rotary connector is based on the principle of optical refraction and reflection. It inputs and outputs optical signals through optical fibers to complete transitional transmission under rotation, ensuring the continuity and stability of the transmitted optical signals and avoiding damage to the optical fibers caused by direct twisting of the optical fibers during rotation. It is an indispensable part of the design process of endoscopes based on OCT technology. However, when designing a fiber optic rotary connector, it is necessary to calibrate the distance between the end faces of the two optical fibers. However, the current calibration method still has the following problems: (1) The diameter of the traditional ceramic ferrule is large at the end face position, and the diameter from the end face to the inside is rapidly reduced to about the diameter of the optical fiber, making it difficult to insert the optical fiber into the ceramic ferrule, resulting in difficulties in docking and inability to effectively align the center; (2) The optimal fiber end face distance is often related to the light transmission efficiency, the fluctuation of the light transmission efficiency when the optical fiber rotates, and the rotation speed of the optical fiber. At present, most of the calibration is performed manually based on experience, which cannot be calibrated quickly and accurately. The main reason is that it is impossible to make each influencing factor reach the ideal optimal at the same time. Summary of the invention

[0006] In order to address the deficiencies in the prior art, the present invention provides a device and method for calibrating the distance between optical fiber end faces based on a gradient ceramic ferrule. The design of the gradient ceramic ferrule not only facilitates the rapid entry of the bare optical fiber into the interior of the ceramic ferrule, but also realizes rapid alignment of the optical fiber end faces; the light transmission efficiency and the light transmission efficiency fluctuation caused by the rotation of the optical fiber are evaluated, thereby realizing automated distance calibration and improving calibration efficiency and accuracy.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a device for calibrating the distance between optical fiber end faces based on a gradient ceramic ferrule.

[0009] A device for calibrating the end face distance of an optical fiber based on a gradient ceramic ferrule, comprising: a motor, a long shaft, a rotating optical fiber, a displacement optical fiber, a displacement platform, and a gradient ceramic ferrule, wherein the rotating optical fiber passes through the long shaft and the first end of the rotating optical fiber passes through the long shaft, and the output end of the motor is connected to the long shaft to control the rotation of the long shaft;

[0010] The first end of the rotating optical fiber is a bare optical fiber, the displacement optical fiber is directly or indirectly connected to the displacement platform so as to control the movement of the displacement optical fiber through the displacement platform, the first end of the displacement optical fiber is a bare optical fiber, and the first end of the rotating optical fiber and the first end of the displacement optical fiber are respectively inserted through two ports of the gradient ceramic ferrule and are centrally aligned.

[0011] As a further limitation of the first aspect of the present invention, the gradient ceramic ferrule comprises: a ferrule body, wherein a through hole is provided in the ferrule body for inserting and center-aligning a rotating optical fiber bare end and a displacement optical fiber bare end;

[0012] The center position of the through hole is a cylindrical through hole with a consistent inner diameter, and both ends of the cylindrical through hole extend outwards respectively and the inner diameter increases gradually.

[0013] As a further limitation of the first aspect of the present invention, the center position of the ferrule body is taken as the coordinate origin, and the central axis of the ferrule body is taken as Axis, in the horizontal plane The direction perpendicular to the axis is The edge curve of the axial section of the through hole includes: a first piecewise function, a second piecewise function and a third piecewise function;

[0014] The edge curve corresponding to the cylindrical through hole is the first piecewise function. The value is a constant, the edge curve on the left side of the cylindrical through hole is the second piecewise function, and the second piecewise function The value is about The edge curve on the right side of the cylindrical through hole is the third piecewise function. The value is about A quadratic function of .

[0015] As a further limitation of the first aspect of the present invention, the long shaft is divided into two sections, the two sections are connected by a coupling, the first section is connected to the motor, and the second section passes through the inner ring of the bearing in the bearing seat.

[0016] As a further limitation of the first aspect of the present invention, the displacement optical fiber is connected to the displacement platform via a clamp.

[0017] In a second aspect, the present invention provides a method for calibrating the distance between optical fiber end faces based on a gradient ceramic ferrule.

[0018] A method for calibrating the distance between optical fiber end faces based on a gradient ceramic ferrule, using the device for calibrating the distance between optical fiber end faces based on a gradient ceramic ferrule according to the first aspect of the present invention, comprises the following process:

[0019] The motor drives the rotating optical fiber to rotate one circle to obtain a graphic area surrounded by a power-angle image;

[0020] Obtain the rotating fiber rotation speed, output beam diameter, end face distance between two optical fibers, light transmission efficiency, and maximum beam waist distance for maintaining light collimation;

[0021] The sum of the product of the fluctuation evaluation coefficient and the pattern area, the product of the rotation speed evaluation coefficient and the rotation speed of the rotating optical fiber, and the product of the effect evaluation coefficient and the light transmission efficiency is the first variable;

[0022] The second variable is the power of half of the product of the output beam diameter and the end face distance, and the ratio of the product of the first variable and the maximum beam waist distance to the second variable is used as the evaluation result value;

[0023] A plurality of evaluation result values ​​are determined according to different end face distances, and the end face distance corresponding to the maximum evaluation result value and the corresponding two optical fiber positions are taken as the optimal calibration result.

[0024] As a further limitation of the second aspect of the present invention, the light transmission efficiency is: the ratio of the optical power at the second end of the displaced optical fiber to the initial power at the first end of the rotated optical fiber.

[0025] As a further limitation of the second aspect of the present invention, the output beam diameter is: ,in, is the wavelength of light, is the mode field diameter, is the focal length of the collimator.

[0026] As a further limitation of the second aspect of the present invention, the maximum beam waist distance is: .

[0027] As a further limitation of the second aspect of the present invention, the rotation speed of the rotating optical fiber is: ,in, is the number of pole pairs of the motor’s rotating magnetic field, is the power supply frequency.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention innovatively designs a device for calibrating the end face distance of an optical fiber based on a gradient ceramic ferrule, develops a gradient ceramic ferrule, improves the internal structure of the ceramic ferrule, and produces a diameter gradient ceramic ferrule, which can make it easier for the optical fiber to enter the interior of the ceramic ferrule, facilitate its center alignment, facilitate the movement of the displacement optical fiber, and also achieve the effect of reducing radial runout during rotation.

[0030] 2. The present invention innovatively designs a method for calibrating the optical fiber end face distance based on a gradient ceramic ferrule. The same evaluation but different coefficients are selected according to different application scenarios. By comparing the values ​​of the evaluation results, the optimal end face distance is intuitively obtained, which greatly improves the evaluation efficiency and accuracy.

[0031] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0033] Figure 1 A schematic diagram of a gradient ceramic ferrule provided in a specific embodiment of the present invention;

[0034] Figure 2 A schematic diagram for determining the size of a ceramic ferrule provided in a specific embodiment of the present invention;

[0035] Figure 3 A schematic diagram of a device for calibrating the distance between optical fiber end faces based on a gradient ceramic ferrule provided in a specific embodiment of the present invention;

[0036] Figure 4 The power and angle of the optical fiber when it rotates one circle provided in the specific embodiment of the present invention images;

[0037] Among them, 1. ferrule body; 2. through hole; 3. motor; 4. long axis; 5. rotating optical fiber; 6. displacement optical fiber; 7. displacement platform; 8. fixture; 9. coupling; 10. bearing seat. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0039] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0040] In this implementation, a gradient ceramic ferrule is first proposed, such as Figure 1 As shown, it comprises: a ferrule body 1, wherein the ferrule body 1 has a hole for rotating the optical fiber 5 (such as Figure 3 ) and the bare end of the displacement optical fiber 6 (as shown in Figure 3 The bare end of the optical fiber 6 is inserted into and aligned with the center of the through hole 2, the center position of the through hole 2 is a cylindrical through hole with the same inner diameter, and the two ends of the cylindrical through hole extend outward respectively and the inner diameter gradually increases. This gradual structure can make it easier for the optical fiber to enter the ferrule body 1, facilitate its center alignment, and also facilitate the movement of the displacement optical fiber 6 and can also achieve the effect of reducing the radial runout during the rotation of the rotating optical fiber 5.

[0041] For the dimensions of the ferrule body 1, establish Figure 2 In the coordinate axis shown, the length of the ferrule body 1 is L, and according to the structural design of the ferrule body 1, the internal curve of the ferrule body 1 is set as a piecewise function. Specifically, according to the coordinates of the three points A (-L / 2, 0.4), B (-0.4, 0.0625) and C (L / 2, 0.4), the curve function inside the ferrule body 1 can be deduced as:

[0042] (1);

[0043] (2);

[0044] (3);

[0045] Among them, formula (2) represents the first piecewise function, formula (1) represents the second piecewise function, and formula (3) represents the third piecewise function. It can be seen that the first piecewise function The value is a constant, and the second piecewise function The value is about The quadratic function of the third piecewise function The value is about A quadratic function of .

[0046] like Figure 3 As shown, based on the above-mentioned gradient ceramic ferrule, this implementation provides a device for calibrating the distance between optical fiber end faces, including: a motor 3, a long shaft 4, a rotating optical fiber 5, a displacement optical fiber 6 and a displacement platform 7, wherein the rotating optical fiber 5 penetrates into the long shaft 4 and the first end of the rotating optical fiber 5 penetrates out of the long shaft 4, and the output end of the motor 3 is connected to the long shaft 4 to control the rotation of the long shaft 4;

[0047] The first end of the rotating optical fiber 5 is a bare optical fiber, and the displacement optical fiber 6 is directly or indirectly connected to the displacement platform 7 so as to control the movement of the displacement optical fiber 6 through the displacement platform 7. The first end of the displacement optical fiber 6 is a bare optical fiber, and the first end of the rotating optical fiber 5 and the first end of the displacement optical fiber 6 are respectively inserted through the two ports of the core body 1 and are center-aligned.

[0048] In this implementation, the long shaft 4 is divided into two sections, and the two sections are connected by a coupling 9 , the first section is connected to the motor 3 , and the second section passes through the inner ring of the bearing in the bearing seat 10 .

[0049] In the present implementation, preferably, an indirect connection is adopted, that is, the displacement optical fiber 6 is connected to the displacement platform 7 via a clamp 8 .

[0050] The calibration method based on the above calibration device includes the following steps:

[0051] S1: Determine the initial power.

[0052] S1.1: First, take two sections of optical fiber (respectively as the rotating optical fiber 5 and the displacement optical fiber 6) and perform stripping, cleaning and cutting operations on one end of each section to make them into bare optical fibers;

[0053] S1.2: Insert an optical fiber into the central through hole of the long axis 4, and expose the first end of the optical fiber to a part of the long axis 4. Connect the non-bare end (i.e., the second end) of the optical fiber to the light source, and measure the power of one end (i.e., the first end) of the bare optical fiber and name it as the initial power. The optical fiber is named the rotation optical fiber 5, the other optical fiber is the displacement optical fiber 6, and the bare optical fiber end of the displacement optical fiber 6 is the first end.

[0054] S2: Center alignment.

[0055] S2.1: Insert one end of the bare fiber of the rotating optical fiber 5 and one end of the bare fiber of the displacement optical fiber 6 into two ends of the ferrule body 1 respectively until the centers of the two are aligned;

[0056] S2.2: Move the rotating optical fiber 5 and the displacing optical fiber 6 so that the end faces of the two bare optical fibers are located at the center of the ferrule body 1 and are infinitely close to each other.

[0057] S3: Distance power measurement.

[0058] S3.1: Place the displacement optical fiber 6 on the displacement platform 7 and connect it to the light source so that it passes through the rotating optical fiber 5 and enters the displacement optical fiber 6 to form a structure as shown in FIG. Figure 3 The platform shown;

[0059] S3.2: Use a power meter to measure the output power of the non-bare fiber end of the shifted optical fiber 6 (i.e., the second end of the shifted optical fiber 6) ;

[0060] S3.3: Use the displacement platform 7 to set the distance between the two end faces to 0.05 mm, and use the power meter to measure the output power and the initial power of the light Divide to get the light efficiency ;

[0061] S3.4: At the same time, the motor 3 is used to rotate the rotating optical fiber 5, and its light transmission efficiency during the rotation process is measured. Since the rotating optical fiber 5 will have radial runout during the rotation process, its light transmission efficiency is not constant. The power and angle of the rotating optical fiber 5 when it rotates one circle are measured. The image is obtained by taking the power-angle image and calculating the area of ​​the image enclosed by the power-angle image using the following formula:

[0062] (4);

[0063] in, It refers to the measured value of the change of the light transmission efficiency of the rotating optical fiber 5 with the rotation angle during the rotation process.

[0064] like Figure 4 As shown, the rotating optical fiber 5 rotates one circle within the range of 0-360°, and an angle is divided into 0°, 15°,..., 330°, 345° every 15°, and the length of each angle is the efficiency (20, 40, 60 and 80 in the figure represent 20% efficiency, 40% efficiency, 60% efficiency, 80% efficiency respectively), and the area enclosed by this efficiency is the area S, which is used to represent the fluctuation of the efficiency of the rotating optical fiber 5 when it rotates one circle and the level of the overall efficiency.

[0065] S3.5: Use the displacement platform 7 to set the distances between the two end faces to 0.10 mm, 0.15 mm, ..., 1.2 mm respectively. Repeat the above operation and use a power meter to measure the output power. and compare it with the initial light power Divide to get the light efficiency (i=2,3...).

[0066] S4: Position evaluation.

[0067] S4.1: Under different usage conditions, the requirements for rotation speed are different. Currently, it is impossible to minimize both the light transmission efficiency and the fluctuation during the rotation process. Therefore, the present invention needs to evaluate the different distances represented by different positions of the exposed end face of the rotating optical fiber 5.

[0068] Theoretical value of known output beam diameter for:

[0069] (5);

[0070] in, is the wavelength of light, in nm; is the mode field diameter, in μm; is the focal length of the collimator in mm.

[0071] Maximum waist distance , refers to the maximum distance that the beam waist can be from the lens in order to maintain collimation, specifically:

[0072] (6);

[0073] In this implementation, the beam waist refers to the position where the radius of the light beam is the smallest in the propagation direction.

[0074] The rotation speed of the rotating optical fiber 5 is:

[0075] (7);

[0076] in, is the number of pole pairs of the rotating magnetic field of motor 3; is the power supply frequency; is the rotation speed, unit is r / min.

[0077] Substitute the above formulas into the formula:

[0078] (8);

[0079] in, is the fluctuation evaluation coefficient, unit: r -1 ; b is the speed evaluation coefficient, unit is min / r; c is the effect evaluation coefficient; is the end face distance between the rotation optical fiber 5 and the displacement optical fiber 6, in mm; is the evaluation result value.

[0080] The best evaluation formula for evaluating the distance between the rotating optical fiber 5 and the displaced optical fiber 6 is obtained:

[0081] (9).

[0082] It should be noted that in different application cases, the values ​​of the three evaluation coefficients a, b and c are different, and the sum of the three is always 1. For the calibration of optical fiber rotary connectors, it is more inclined to pursue more stability and high efficiency (that is, it is hoped that the fluctuation evaluation coefficient and the effect evaluation coefficient are larger), so a=0.4, b=0.2, c=0.4 can be taken; if it is applied to high speed requirements (in this case, it is hoped that the speed evaluation coefficient is larger), then a=0.2, b=0.6, c=0.2 can be taken.

[0083] During the distance calibration of the optical fiber rotary connector, the light transmission efficiency should be at least 70% when stationary, and the rotation speed should be less than 10000r / min.

[0084] S5: Determine the optimal position.

[0085] The evaluation results of different end face distances are measured respectively. After that, by comparing the evaluation result values , taken as the evaluation result value The distance value at the maximum value and the positions of the rotated optical fiber 5 and the displaced optical fiber 6 at this time are the optimal results.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for calibrating the distance between optical fiber end faces based on a gradient ceramic ferrule, characterized in that: include: A motor, a long shaft, a rotating optical fiber, a displacement optical fiber, a displacement platform, and a gradient ceramic ferrule, wherein the rotating optical fiber passes through the long shaft and the first end of the rotating optical fiber passes through the long shaft, and the output end of the motor is connected to the long shaft to control the rotation of the long shaft; The first end of the rotating optical fiber is a bare optical fiber, the displacement optical fiber is directly or indirectly connected to the displacement platform so as to control the movement of the displacement optical fiber through the displacement platform, the first end of the displacement optical fiber is a bare optical fiber, the first end of the rotating optical fiber and the first end of the displacement optical fiber are respectively inserted through two ports of the gradient ceramic ferrule and are centrally aligned; The gradient ceramic ferrule comprises: a ferrule body, wherein a through hole is provided in the ferrule body for inserting and center-aligning the rotating optical fiber bare end and the displacement optical fiber bare end; The center position of the through hole is a cylindrical through hole with a uniform inner diameter, and both ends of the cylindrical through hole extend outwards respectively and the inner diameter gradually increases; Calibration process: The motor drives the rotating optical fiber to rotate one circle to obtain a graphic area surrounded by a power-angle image; Obtain the rotating fiber rotation speed, output beam diameter, end face distance between two optical fibers, light transmission efficiency, and maximum beam waist distance for maintaining light collimation; The sum of the product of the fluctuation evaluation coefficient and the pattern area, the product of the rotation speed evaluation coefficient and the rotation speed of the rotating optical fiber, and the product of the effect evaluation coefficient and the light transmission efficiency is the first variable; The second variable is the power of half of the product of the output beam diameter and the end face distance, and the ratio of the product of the first variable and the maximum beam waist distance to the second variable is used as the evaluation result value; A plurality of evaluation result values ​​are determined according to different end face distances, and the end face distance corresponding to the maximum evaluation result value and the corresponding two optical fiber positions are taken as the optimal calibration result.

2. A method for calibrating the distance between optical fiber end faces based on a gradient ceramic ferrule as claimed in claim 1, characterized in that: The center of the ferrule body is taken as the coordinate origin, and the central axis of the ferrule body is taken as Axis, in the horizontal plane The direction perpendicular to the axis is The edge curve of the axial section of the through hole includes: a first piecewise function, a second piecewise function and a third piecewise function; The edge curve corresponding to the cylindrical through hole is the first piecewise function. The value is a constant, the edge curve on the left side of the cylindrical through hole is the second piecewise function, and the second piecewise function The value is about The edge curve on the right side of the cylindrical through hole is the third piecewise function. The value is about A quadratic function of .

3. A method for calibrating the distance between optical fiber end faces based on a gradient ceramic ferrule as claimed in claim 1, characterized in that: The long shaft is divided into two sections, which are connected by a coupling. The first section is connected to the motor, and the second section passes through the inner ring of the bearing in the bearing seat.

4. A method for calibrating the distance between optical fiber end faces based on a gradient ceramic ferrule as claimed in claim 1, characterized in that: The displacement optical fiber is connected to the displacement platform through a clamp.

5. The method for calibrating the optical fiber end face distance based on the gradient ceramic ferrule according to claim 1, characterized in that: The light transmission efficiency is: the ratio of the optical power at the second end of the displaced optical fiber to the initial power at the first end of the rotated optical fiber.

6. A method for calibrating the distance between optical fiber end faces based on a gradient ceramic ferrule as claimed in claim 1, characterized in that: The output beam diameter is: ,in, is the wavelength of light, is the mode field diameter, is the focal length of the collimator.

7. A method for calibrating the distance between optical fiber end faces based on a gradient ceramic ferrule as claimed in claim 6, characterized in that: The maximum waist distance is: .

8. The method for calibrating the optical fiber end face distance based on the gradient ceramic ferrule according to claim 6, characterized in that: The rotating fiber rotation speed is: ,in, is the number of pole pairs of the motor’s rotating magnetic field, is the power supply frequency.

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