Large-section, high-resolution flexible optical fiber imaging bundle and preparation method thereof

Abstract

The present invention relates to the field of optical fiber technology, and discloses a flexible optical fiber imaging bundle with large cross-section and high resolution, and a preparation method thereof. The bundle comprises a fiber core, wherein the outside of each optical fiber core is coated with an optical cladding, and the outer wall of the optical cladding has a plurality of randomly distributed recesses, so that the refractive index difference between the optical cladding and the optical fiber core is increased. An acid-soluble glass layer with microbubbles is provided on the outer side of the optical cladding, so that a thin-walled portion that is easily eroded by an acid solution is formed on the surface of the acid-soluble glass layer. During the acid dissolution process, the acid solution can dissolve toward the bundle core along the easily soluble acid-soluble glass layer portion, thereby accelerating the dissolution speed and avoiding the problem of a hard core. During the dissolution process, recesses can be formed on the surface of the second optical cladding, which can increase the spacing between the optical claddings and the difference between the optical claddings, thereby reducing crosstalk between the cores, improving the transmission quality of the imaging bundle, and obtaining a large-cross-section, high-resolution optical fiber imaging bundle.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber image transmission bundles, and in particular to a flexible optical fiber image transmission bundle with a large cross-section and high resolution and a preparation method thereof. Background Art

[0002] A fiber optic image bundle is an optical element that can transmit images by arranging multiple multi-component glass optical fibers of a certain length into a bundle with one-to-one correspondence at both ends. As one of the ways to transmit images, a fiber optic image bundle can be used in situations where the image transmission distance is long, the environment is harsh (high and low temperature, radiation, corrosion, vibration), and flexible image transmission is required. Large-section, flexible fiber optic image bundles with high resolution are widely used in industrial, medical, and military fields. For example, fiber optic image bundles can be used to prepare flexible aiming systems, periscopes, and electromagnetic and radiation-resistant image transmission systems.

[0003] Currently, there are two main methods for preparing fiber optic image bundles: lamination and acid dissolution. The large-cross-section fiber optic image bundles produced by the lamination method have relatively thick single filaments, low resolution, and are not flexible enough to meet application requirements. Therefore, the acid dissolution method is generally used to produce flexible image bundles.

[0004] The acid dissolution method first draws three layers of coaxial monofilaments including a core layer, an optical cladding, and a soluble glass layer, then arranges them into bundles, hot-melt-draws them into composite filaments, and finally places the composite filaments in an acid solution to remove the soluble glass layer (except at the ends of the image transmission bundle), so that the individual monofilaments are separated, thereby obtaining the flexibility of the image transmission bundle. However, when making image transmission bundles larger than 3mm, for example, this process cannot be corroded because the acid solution cannot penetrate smoothly into the soluble glass in the middle of the image transmission bundle. Therefore, it is difficult to produce large cross-sections. In addition, the resolution of the optical fiber image transmission bundle is limited by the core density and the crosstalk between the cores. The acid dissolution method can produce optical fiber bundles with high core density, but the high-density core arrangement leads to increased crosstalk between the cores, thereby reducing the image transmission quality.

[0005] Prior art literature:

[0006] Patent document 1CN111190251A A method for manufacturing a large-section, high-resolution flexible optical fiber imaging bundle

[0007] Patent Document 2CN104181636A Flexible High-Resolution Infrared Chalcogenide Glass Fiber Image Bundle and Preparation Method

[0008] Patent document 3CN108680989A A high-resolution image-transmitting glass fiber bundle Summary of the Invention

[0009] The first aspect of the present invention provides a technical solution, a method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution, comprising the following steps:

[0010] Step 1: Wire drawing:

[0011] 1.1) Select the fiber core rod, cladding glass tube and acid-soluble glass tube with microbubbles in the tube wall;

[0012] 1.2): On the outside of the core rod, the cladding glass tube and the acid-soluble glass tube are sequentially installed from the inside to the outside;

[0013] 1.3): drawn into monofilament by the rod-tube method;

[0014] Step 2, arranging the wire: cutting the monofilament drawn in the step into the required length and arranging the wire tightly in a hexagonal shape to form a multifilament rod;

[0015] Step 3, multifilament drawing: one end of the primary multifilament rod obtained in the step is hung on a wire drawing machine, and the other end is heated by an electric furnace to draw a hard image transmission bundle;

[0016] Step 4, hot melting: The small-section rigid image transfer bundles prepared in the step are tightly arranged and bundled into a bundle, and both ends of the bundle are simultaneously pressurized and hot-melted in a hot melting device to fuse the two ends of the rigid image transfer bundle together;

[0017] Step 5, acid dissolution: Protect the two hot-melt ends of the large-section rigid image transmission bundle obtained in the step with acid-resistant materials, immerse them in flowing acid solution to dissolve the acid-soluble layer, so that the fiber core becomes discrete single filaments, and form several recesses on the surface of the cladding to make a soft and bendable large-section flexible optical fiber image transmission bundle.

[0018] Preferably, the method for preparing the acid-soluble glass tube having microbubbles in the tube wall in step 1 comprises: step a, adding ultrafine silicon dioxide powder with a particle size of 10 to 100 nm to a siliceous raw material; and step b, manually blowing the glass solution before defoaming.

[0019] Preferably, the cladding glass tube in step 1 includes two layers distributed from the inside to the outside, and the refractive index of the outer cladding glass tube is less than or equal to the refractive index of the inner cladding glass tube.

[0020] Preferably, the multifilament drawing in step 3 includes secondary multifilament: the hard image transmission bundles are tightly arranged in a hexagon, and then one end is hung on a wire drawing machine, and the other end is heated by an electric furnace to draw a secondary multifilament bundle.

[0021] Preferably, in step 6, the concentration of the acid solution is 0.5N, the temperature of the acid solution is 30° C. to 40° C., and the flow rate of the acid solution is 0.8 to 1.2 L / min.

[0022] The second aspect of the present invention provides a technical solution, a large-cross-section, high-resolution flexible optical fiber imaging bundle, comprising:

[0023] A fiber core, the fiber core comprising a plurality of densely arranged image transmission units;

[0024] The image transmission unit comprises a plurality of optical fiber cores arranged in a regular polygonal shape, each of the optical fiber cores being covered with an optical cladding, and the outer wall of the optical cladding having a plurality of randomly distributed recesses to increase the refractive index difference between the optical cladding and the optical fiber core;

[0025] The depth of the recess is less than 1 / 2 of the thickness of the optical cladding.

[0026] Preferably, the recesses are arranged in a dot shape or a strip shape.

[0027] Preferably, the optical cladding includes a first optical cladding coated on the outside of the optical fiber core and a second optical cladding coated on the outside of the first optical cladding, and the recess is provided on an outer wall of the second optical cladding.

[0028] Preferably, the refractive index of the second optical cladding is less than or equal to the refractive index of the first optical cladding, and the thickness ratio of the second optical cladding to the first optical cladding is in a range of 3 / 2 to 1 / 1.

[0029] Preferably, the regular polygon includes a regular quadrilateral or a regular hexagon.

[0030] Compared with the prior art, the advantages of the present invention are:

[0031] The method for preparing an optical fiber image transmission bundle proposed in the present invention arranges an acid-soluble glass layer with microbubbles on the outside of the optical cladding, so that the surface of the acid-soluble glass layer forms a thin-walled portion that is easily corroded by the acid solution. During the acid dissolution process, the acid solution can dissolve along the easily soluble acid-soluble glass layer portion toward the bundle core portion, thereby accelerating the dissolution speed and avoiding the problem of a hard core.

[0032] The preparation method of the optical fiber imaging bundle proposed in the present invention can form a recess on the surface of the second optical cladding during the dissolution process, which can increase the spacing between the optical claddings and the difference between the optical claddings, thereby reducing the crosstalk between the cores, improving the transmission quality of the imaging bundle, and obtaining a large-cross-section high-resolution optical fiber imaging bundle.

[0033] The flexible optical fiber imaging bundle proposed in the present invention can provide an optical fiber imaging bundle with a large cross-section and ensure that the imaging bundle has high resolution without increasing the inter-core crosstalk caused by a high fiber core density. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For the sake of clarity, not every component is labeled in every figure. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings, in which:

[0035] Figure 1 Schematic diagram of the cross-sectional structure of a flexible optical fiber imaging bundle with large cross-section and high resolution shown in an embodiment of the present invention;

[0036] Figure 2 Schematic diagram of the cross-sectional structure of an image transmission unit in a flexible optical fiber image transmission bundle with large cross-section and high resolution shown in an embodiment of the present invention;

[0037] Figure 3 Schematic diagram of the partial structure of the image transmission unit in the flexible optical fiber image transmission bundle with large cross-section and high resolution shown in an embodiment of the present invention;

[0038] Figure 4 It is a structural schematic diagram of the concave portion formed on the surface of the optical cladding in a flexible optical fiber imaging bundle with a large cross-section and high resolution shown in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to better understand the technical content of the present invention, specific embodiments are given and described below with reference to the accompanying drawings.

[0040] For the optical fiber core currently made by the rod-and-tube method, a solid soluble glass layer is used to cover the outside of the optical cladding. After the multifilament is melt-pressed, it is acid-dissolved, which will result in the problem of a hard core still existing in the middle after the outer layer of soluble glass is completely dissolved. The present application uses a soluble glass layer containing tiny bubbles to accelerate the acid solution's erosion of the soluble glass layer and form a recess on the outer wall of the optical cladding to avoid the problem of a hard core. At the same time, it increases the refractive index difference between the optical fiber cores, further reduces the crosstalk between the cores, and obtains a large-section, high-resolution flexible optical fiber imaging bundle.

[0041] [Preparation method of flexible fiber optic imaging bundle with large cross-section and high resolution]

[0042] The first aspect of the present invention provides a technical solution, a method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution, comprising the following steps:

[0043] Step 1: Wire drawing:

[0044] 1.1: Select a fiber core rod (outer diameter 18mm) made of high-purity silica, a cladding glass tube doped with a small amount of germanium dioxide, phosphorus pentoxide, and boron trioxide, and an acid-soluble glass tube (inner diameter 23mm, wall thickness 1.5mm) with a boron trioxide and barium oxide content of more than 40%, so that the refractive index of the fiber core rod is greater than that of the cladding glass tube and greater than or equal to the refractive index of the acid-soluble glass tube.

[0045] Among them, the cladding glass tube includes two layers distributed from the inside to the outside (the inner layer has an inner diameter of 19mm and a wall thickness of 1.5mm, and the outer layer has an inner diameter of 21mm and a wall thickness of 1.5mm), and the refractive index of the outer cladding glass tube is less than or equal to the refractive index of the inner cladding glass tube.

[0046] Furthermore, the acid-soluble glass tube is made by adding ultrafine silicon dioxide powder with a particle size of 10 to 100 nm to the siliceous raw material and manually blowing the glass solution before defoaming, so that the tube wall has irregularly distributed microbubbles, and the bubbles occupy about 1 / 3 of the volume in the tube.

[0047] 1.2: Cladding glass tube and acid-soluble glass tube are sequentially installed on the outside of the core rod from the inside to the outside, with the diameter difference between adjacent tubes being 0.5mm.

[0048] 1.3: Use the rod-tube method to draw the monofilament, and control the monofilament diameter to 0.5-1mm.

[0049] Step 2: Arranging the wires: Cut the monofilaments drawn in step 1 into the required length and arrange them tightly in a hexagonal shape to form a multifilament rod.

[0050] Step 3, multifilament drawing: hang one end of the primary multifilament rod obtained in step 2 on a wire drawing machine, and heat the other end through an electric furnace to draw a hard image transmission bundle with a cross section of 0.2 to 1 mm, wherein the diameter of the single wire is 10 to 20 μm.

[0051] Among them, multifilament drawing can also include secondary multifilament: the hard image transmission bundle is tightly arranged in a hexagon, and then one end is hung on the wire drawing machine, and the other end is heated by an electric furnace to draw a secondary multifilament bundle, so that a hard image transmission bundle with higher resolution can be obtained.

[0052] Step 5, hot melting: Arrange the small-section hard image transfer bundle prepared in step 3 tightly and bundle it into a bundle with copper wire. Pressurize and hot melt both ends of the bundle simultaneously in a hot melting device. Slowly increase the temperature from room temperature to 380°C at a heating rate of 5°C / min, and increase the temperature from 380°C to 600°C at a heating rate of 10°C / min. Maintain the temperature at 600°C for about 15 minutes, and cool it down to room temperature at a cooling rate of 5°C / min to fuse the two ends of the hard image transfer bundle together.

[0053] Step 6, acid dissolution: The two hot-melt ends of the large-section rigid image transmission bundle with the ends hot-melt prepared in step 5 are protected with acid-resistant materials, immersed in a flowing acid solution to dissolve the acid-soluble layer, so that the fiber core becomes discrete single filaments, and a plurality of recesses 221 are formed on the surface of the cladding to make a large-section flexible optical fiber image transmission bundle with a cross-sectional size of 5 to 30 mm. The acid solution uses hydrochloric acid solution with a concentration of 0.5N, the acid solution temperature is 30°C to 40°C, and the acid solution flow rate is 0.8 to 1.2 L / min.

[0054] In combination with the above embodiment, the cross-sectional distribution of the hard image beam is as follows: Figure 4 In figure a, the optical fiber core 1, the first optical cladding 21, the second optical cladding 22, and the acid-soluble glass layer 3 are arranged. The portion of the acid-soluble glass layer 3 with bubbles distributed therein is a thin-walled portion 31 that is easily corroded by the acid solution. During the acid dissolution process, the acid solution easily penetrates the acid-soluble glass layer 3 with bubbles on the surface thereof and penetrates inward along the acid-soluble glass layer 3 until the acid-soluble glass layer 3 on the entire surface of the rigid image transmission bundle is completely dissolved. During this process, the acid-soluble glass layer 3 is more easily dissolved than the existing solid glass layer due to the bubbles inside it. Therefore, the relative dissolution speed is faster, and the erosion of the optical components is less.

[0055] Furthermore, during the process of dissolving the acid-soluble glass layer 3 with the acid solution, the portion with bubbles dissolves at a relatively faster rate. Therefore, the surface of the inner second optical cladding 22 where the bubbles are distributed will be corroded by the acid solution, thereby forming a recess 221 on the surface, which can increase the spacing between the optical claddings 2 and the difference between the optical claddings 2, thereby reducing inter-core crosstalk and improving the transmission quality of the image beam.

[0056]

Large cross-section, high-resolution flexible fiber optic imaging bundle

[0057] A second aspect of the present invention provides a technical solution, a flexible optical fiber imaging bundle with a large cross-section and high resolution, comprising a fiber core 100 and a packaging layer covering the outside of the fiber core 100.

[0058] The fiber core 100 includes multiple groups of densely arranged image transmission units 10, and the packaging layer is arranged to cover the outside of the fiber core 100. The packaging layer can be made of metal or plastic material to form a tubular structure on the outside of the fiber core 100, which can protect the fiber core 100.

[0059] Furthermore, the image transmission unit 10 includes a plurality of optical fiber cores 1 arranged in a regular polygonal shape, and the outside of each optical fiber core 1 is covered with an optical cladding 2. The outer wall of the optical cladding 2 has a plurality of randomly distributed recesses 221, which increases the refractive index difference between the optical cladding 2 and the optical fiber core 1, thereby making each optical fiber core have a stronger light limiting capability.

[0060] The concave portion 221 is configured to be in a dot shape or a strip shape. The concave portion 221 can retain air, thereby increasing the difference between the optical claddings 2 and reducing the crosstalk between cores.

[0061] In a preferred embodiment, the optical cladding 2 includes a first optical cladding 21 coated on the outside of the optical fiber core 1 and a second optical cladding 22 coated on the outside of the first optical cladding 21. The recess 221 is provided on the outer wall of the second optical cladding 22, and the depth of the recess 221 is less than 1 / 2 of the thickness of the optical cladding 2.

[0062] Specifically, the thickness of the first optical cladding 21 and the second optical cladding 22 is 3 / 2 of that of the traditional cladding. Therefore, the outer second optical cladding 22 is eroded by the acid solution to form a recess 221, which increases the difference between the optical claddings 2 to reduce the crosstalk between the cores. In this way, a high-resolution optical fiber image bundle can be obtained.

[0063] At the same time, the first optical cladding 21 will not be damaged by the acid solution, and can maintain a complete optical structure. It has a good light-limiting ability to avoid light leakage, and its bending ability after corrosion can be consistent with that of a traditional fiber core.

[0064] Furthermore, the refractive index of the second optical cladding 22 is less than or equal to the refractive index of the first optical cladding 21, and the thickness ratio of the second optical cladding 22 to the first optical cladding 21 is between 3 / 2 and 1 / 1. In this way, the possibility of the first optical cladding 21 being corroded by the acid solution can be minimized, and the inner first optical cladding 21 can be kept with a complete optical structure to obtain better light confinement capability. At the same time, the surface of the second optical cladding 22 is corroded to form a concave portion 221, which increases the difference between the optical claddings 2, thereby reducing inter-core crosstalk. As a result, the double-layer optical cladding 2 still has good bending performance as a whole.

[0065] Regular polygons include regular quadrilaterals or regular hexagons, which can be arranged according to usage requirements, among which regular hexagons have a higher utilization rate.

[0066] In combination with the above embodiments, an acid-soluble glass layer 3 with microbubbles is provided on the outside of the optical cladding 2, so that a thin-walled portion 31 easily eroded by the acid solution is formed on the surface of the acid-soluble glass layer 3. During the acid dissolution process, the acid solution can dissolve along the easily soluble portion of the acid-soluble glass layer 3 toward the core portion of the bundle, thereby accelerating the dissolution speed and avoiding the problem of a hard core.

[0067] During the dissolution process, a recess 221 can be formed on the surface of the second optical cladding 22, which can increase the spacing between the optical claddings 2 and the differences between the optical claddings 2, thereby reducing inter-core crosstalk, improving the transmission quality of the image bundle, and obtaining a large-cross-section high-resolution optical fiber image bundle.

[0068] While the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution, characterized in that: The following steps are involved: Step 1: Wire drawing: 1.1) Select the fiber core rod, cladding glass tube and acid-soluble glass tube with microbubbles in the tube wall; 1.2): On the outside of the core rod, the cladding glass tube and the acid-soluble glass tube are sequentially installed from the inside to the outside; 1.3): drawn into monofilament by the rod-tube method; Step 2, arranging the wire: cutting the monofilament drawn in step 1 into the required length and arranging the wire tightly in a hexagonal shape to form a multifilament rod; Step 3, multifilament drawing: one end of the primary multifilament rod obtained in step 2 is hung on a wire drawing machine, and the other end is heated in an electric furnace to draw a hard image transmission bundle; Step 5, hot melting: The small-section rigid image transfer bundles prepared in step 3 are tightly arranged and bundled into a bundle, and both ends of the bundle are simultaneously pressurized and hot-melted in a hot melting device to fuse the two ends of the rigid image transfer bundle together; Step 6, acid dissolution: The two hot-melt ends of the large-section rigid image transmission bundle with the hot-melt ends obtained in step 5 are protected with acid-resistant materials, immersed in a flowing acid solution to dissolve the acid-soluble layer, so that the fiber core becomes discrete single filaments, and a plurality of recesses (221) are formed on the surface of the cladding to make a soft and bendable large-section flexible optical fiber image transmission bundle.

2. The method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution according to claim 1, characterized in that: The method for preparing the acid-soluble glass tube with microbubbles in the tube wall in step 1 comprises: step a, adding ultrafine silicon dioxide powder with a particle size of 10 to 100 nm to a siliceous raw material; step b, manually blowing the glass solution before defoaming.

3. The method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution according to claim 1, characterized in that: The cladding glass tube in step 1 includes two layers distributed from the inside to the outside, and the refractive index of the outer cladding glass tube is less than or equal to the refractive index of the inner cladding glass tube.

4. The method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution according to claim 1, characterized in that: The multifilament drawing in step 3 includes secondary multifilament: the hard image transmission bundle is tightly arranged in a hexagon, and then one end is hung on a wire drawing machine, and the other end is heated by an electric furnace to draw a secondary multifilament bundle.

5. The method for preparing a flexible optical fiber imaging bundle with a large cross-section and high resolution according to claim 1, characterized in that: In step 6, the concentration of the acid solution is 0.5N, the temperature of the acid solution is 30° C. to 40° C., and the flow rate of the acid solution is 0.8 to 1.2 L / min.

6. A flexible fiber optic imaging bundle with large cross-section and high resolution, characterized in that: The method for preparing a large-cross-section, high-resolution flexible optical fiber imaging bundle according to claim 1 comprises: A fiber core (100), wherein the fiber core (100) comprises a plurality of densely arranged image transmission units (10); The image transmission unit (10) comprises a plurality of optical fiber cores (1) arranged in a regular polygonal shape, each optical fiber core (1) is coated with an optical cladding (2) on the outside, and the outer wall of the optical cladding (2) has a plurality of randomly distributed recesses (221) to increase the refractive index difference between the optical cladding (2) and the optical fiber core (1); The depth of the recess (221) is less than 1 / 2 of the thickness of the optical cladding (2).

7. The large-cross-section, high-resolution flexible fiber optic imaging bundle according to claim 6, characterized in that: The recessed portions (221) are arranged in a dot shape or a strip shape.

8. The large-cross-section, high-resolution flexible fiber optic imaging bundle according to claim 6, characterized in that: The optical cladding (2) comprises a first optical cladding (21) coated on the outside of the optical fiber core (1) and a second optical cladding (22) coated on the outside of the first optical cladding (21), and the recess (221) is arranged on the outer wall of the second optical cladding (22).

9. The large-cross-section, high-resolution flexible optical fiber imaging bundle according to claim 8, characterized in that: The refractive index of the second optical cladding (22) is less than or equal to the refractive index of the first optical cladding (21), and the thickness ratio of the second optical cladding (22) to the first optical cladding (21) is between 3 / 2 and 1 / 1.

10. The large-cross-section, high-resolution flexible optical fiber imaging bundle according to claim 6, characterized in that: The regular polygon includes a regular quadrilateral or a regular hexagon.

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