Method for manufacturing multicore hollow-core tapered optical fiber

Abstract

The application provides a preparation method of a multi-core hollow-core tapered optical fiber, which comprises the following steps: precisely controlling the positive pressure, the negative pressure and the speed during the whole drawing process of the multi-core hollow-core tapered optical fiber, measuring the actual diameter of the optical fiber in real time during the whole drawing process, comparing the actual diameter of the optical fiber with a theoretical diameter of the optical fiber, adjusting the drawing speed according to the difference, forming a closed-loop feedback control, and ensuring the accuracy of the drawn multi-core hollow-core tapered optical fiber. The multi-core hollow-core tapered optical fiber with different sizes can be accurately prepared through the application, and the multi-core hollow-core structure of the optical fiber can be maintained during the drawing process of the polygonal tapered zone through the feedback control in the preparation process.

Description

Technical Field

[0001] This invention mainly relates to the field of optical fiber fabrication technology, and in particular to a method for fabricating multi-core hollow tapered optical fibers. Background Technology

[0002] Multi-core hollow optical fiber differs from ordinary round optical fiber. Preforms of different shapes are initially drawn out of the high-temperature furnace as solid. In order to draw the optical fiber into the required multi-core hollow structure, it is necessary to adjust the temperature of the high-temperature furnace, the feeding speed of the preform, the optical fiber preparation speed, and the air pressure control inside the preform. After reaching a certain balance point, the optical fiber will exhibit the required structure.

[0003] During the drawing process of multi-core hollow tapered optical fiber, the drawing speed varies, and the speed varies by multiples. Therefore, in order to produce qualified tapered optical fiber while maintaining the structure of the optical fiber, a precise control method is required. Summary of the Invention

[0004] In view of the technical problems existing in the prior art, the present invention proposes a method for preparing multi-core hollow tapered optical fiber.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] On one hand, the present invention provides a method for fabricating a multi-core hollow tapered optical fiber, comprising:

[0007] (1) Prepare multi-core hollow preforms, wherein the dimensions of the multi-core hollow preforms include: preform diameter D, core preform diameter D (芯) Hollow preform diameter D (空) ;

[0008] (2) Determine the dimensional parameters of the multi-core hollow tapered optical fiber to be drawn, including the fiber diameter d at the thicker end. (1) The core diameter d at the thicker end of the filament (芯1) The hollow diameter d at the thicker end of the wire (空1) The length L1 of the thicker filament end and the diameter d of the fiber at the thinner filament end. (2) The core diameter d at the filament end (芯2) The hollow diameter d at the tip of the filament (空2) The length of the thicker end of the filament is L2, and the length of the tapered section where the filament diameter changes from thick to thin is L3.

[0009] (3) Determine the drawing parameters when drawing the thicker diameter end of the fiber, including the drawing temperature, preform feed rate, fiber drawing speed, and control positive pressure P. 1(+) and control negative pressure P 1(-) ;

[0010] Determine the drawing parameters when drawing the filament diameter end: determine the drawing temperature, fiber drawing speed, and control positive pressure P. 2(+) and control negative pressure P 2(-) ;

[0011] Based on the fiber diameter d at the thicker end (1) The diameter d of the optical fiber at the thinner end (2) Given the length L3 of the tapered region where the fiber diameter changes from thick to thin, calculate the theoretical curve of the fiber diameter changing from thick to thin in the tapered region, and determine the theoretical fiber diameter at any length position in the tapered region.

[0012] The control pressure P during drawing the diameter end of the coarse wire 1(+) Control negative pressure P 1(-) Control of positive pressure P at the diameter end of the drawn filament 2(+) and control negative pressure P 2(-) Determine the control positive pressure P when drawing the tapered zone 正 The curve function of fiber diameter variation and the control negative pressure P 负 Curve function showing the change in fiber diameter;

[0013] (4) Based on the determined drawing parameters when drawing the thicker filament end, the drawing length L1 of the multi-core hollow preform and the fiber diameter d at the thicker filament end are determined. (1) The core diameter d at the thicker end of the filament (芯1) The hollow diameter d at the thicker end of the wire (空1) The thicker diameter end of a multi-core hollow tapered optical fiber;

[0014] (5) The end point of the thick wire diameter of the multi-core hollow tapered optical fiber is the starting point of the tapered region to be drawn. The tapered region drawing starts from the starting point of the tapered region. During the entire tapered region drawing process, the positive pressure and negative pressure are controlled according to the curve function of the change of positive pressure with optical fiber diameter and the curve function of the change of negative pressure with optical fiber diameter when drawing the tapered region. At the same time, the drawing speed of the tapered region drawing process is controlled by closed-loop feedback based on the actual optical fiber diameter at the current drawing position during the real-time measurement of the tapered region drawing process until the tapered region with a length of L3 is completed.

[0015] (6) Based on the determined drawing parameters for drawing the filament diameter end, complete the drawing of the filament diameter end with a length of L2.

[0016] On the other hand, the present invention provides a multi-core hollow tapered optical fiber, which is obtained by the above-mentioned method for preparing multi-core hollow tapered optical fiber.

[0017] On the other hand, a laser system is provided, comprising a multi-core hollow tapered optical fiber obtained by the above-described method for preparing multi-core hollow tapered optical fiber.

[0018] Compared with the prior art, the technical effects of the present invention are as follows:

[0019] This invention enables the precise fabrication of multi-core hollow tapered optical fibers of different sizes. Furthermore, through feedback control during the fabrication process, it ensures that the multi-core hollow structure of the optical fiber is maintained during the drawing of the polygonal tapered region. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a multi-core hollow tapered optical fiber;

[0022] Figure 2 This is a cross-sectional view of a multi-core hollow preform prepared in one embodiment;

[0023] Figure 3 This is a theoretical curve showing the change in fiber diameter versus the change in drawing speed during the tapered region drawing process.

[0024] Figure 4 A graph showing the change in hollow core diameter with control positive pressure during the tapered drawing process;

[0025] Figure 5 A graph showing the change in core diameter with control negative pressure during the tapered zone drawing process;

[0026] Figure 6 This is a comparison chart of the actual and theoretical changes in wire diameter during the tapered zone drawing process using existing methods.

[0027] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] In one embodiment, a method for fabricating a multi-core hollow tapered optical fiber is provided, comprising:

[0030] (1) Prepare multi-core hollow preforms, wherein the dimensions of the multi-core hollow preforms include: preform diameter D, core preform diameter D (芯) Hollow preform diameter D (空) ;

[0031] (2) Determine the dimensional parameters of the multi-core hollow tapered optical fiber to be drawn, including the fiber diameter d at the thicker end. (1) The core diameter d at the thicker end of the filament (芯1) The hollow diameter d at the thicker end of the wire (空1) The length L1 of the thicker filament end and the diameter d of the fiber at the thinner filament end. (2) The core diameter d at the filament end (芯2) The hollow diameter d at the tip of the filament (空2) The length of the thicker end of the filament is L2, and the length of the tapered section where the filament diameter changes from thick to thin is L3.

[0032] (3) Determine the drawing parameters when drawing the thicker diameter end of the fiber, including the drawing temperature, preform feed rate, fiber drawing speed, and control positive pressure P. 1(+) and control negative pressure P 1(-) ;

[0033] Determine the drawing parameters when drawing the filament diameter end: determine the drawing temperature, fiber drawing speed, and control positive pressure P. 2(+) and control negative pressure P 2(-) ;

[0034] Based on the fiber diameter d at the thicker end (1) The diameter d of the optical fiber at the thinner end (2) Given the length L3 of the tapered region where the fiber diameter changes from thick to thin, calculate the theoretical curve of the fiber diameter changing from thick to thin in the tapered region, and determine the theoretical fiber diameter at any length position in the tapered region.

[0035] The control pressure P during drawing the diameter end of the coarse wire 1(+) Control negative pressure P 1(-) Control of positive pressure P at the diameter end of the drawn filament 2(+) and control negative pressure P 2(-) Determine the control positive pressure P when drawing the tapered zone 正 The curve function of fiber diameter variation and the control negative pressure P 负 Curve function showing the change in fiber diameter;

[0036] (4) Based on the determined drawing parameters when drawing the thicker filament end, the drawing length L1 of the multi-core hollow preform and the fiber diameter d at the thicker filament end are determined. (1) The core diameter d at the thicker end of the filament (芯1) The hollow diameter d at the thicker end of the wire (空1) The thicker diameter end of a multi-core hollow tapered optical fiber;

[0037] (5) The end point of the thick wire diameter of the multi-core hollow tapered optical fiber is the starting point of the tapered region to be drawn. The tapered region drawing starts from the starting point of the tapered region. During the entire tapered region drawing process, the positive pressure and negative pressure are controlled according to the curve function of the change of positive pressure with optical fiber diameter and the curve function of the change of negative pressure with optical fiber diameter when drawing the tapered region. At the same time, the drawing speed of the tapered region drawing process is controlled by closed-loop feedback based on the actual optical fiber diameter at the current drawing position during the real-time measurement of the tapered region drawing process until the tapered region with a length of L3 is completed.

[0038] (6) Based on the determined drawing parameters for the diameter end of the filament, complete the drawing of the diameter end of the filament with a length of L2, and obtain the following: Figure 1 The multi-core hollow tapered optical fiber shown.

[0039] The multi-core hollow preform prepared in step (1) has the following dimensions: preform diameter D, core preform diameter D0. (芯) Hollow preform diameter D (空) .like Figure 2 The image shown is a cross-sectional view of a multi-core hollow preform prepared in one embodiment. The overall cross-section of the multi-core hollow preform is circular, including a hollow preform located at the center and multiple fiber core preforms surrounding the hollow preform. Figure 2 There are four medium fiber core preforms, located at the top, bottom, left, and right positions of the hollow preform. The cladding covers the hollow preform and the fiber core preform, making the overall cross-section of the multi-core hollow preform circular, and the diameter of the multi-core hollow preform is D.

[0040] This invention proposes a gas pressure control scheme for the stable variation of the core and hollow core diameters during the drawing of multi-core hollow tapered optical fibers. When the fiber diameter decreases, the gas pressure control of the preform does not change accordingly, which can lead to preform core explosion. Specifically, in this invention, the control pressure P during the drawing of the thicker fiber diameter end is adjusted accordingly. 1(+) Control negative pressure P 1(-) Control of positive pressure P at the diameter end of the drawn filament 2(+) and control negative pressure P 2(-) Determine the control positive pressure P when drawing the tapered zone 正 The curve function showing the change in fiber diameter is as follows:

[0041]

[0042] Control negative pressure P during tapered drawing 负 The curve function showing the change in fiber diameter is as follows:

[0043]

[0044] Where d is the actual fiber diameter at the current drawing position.

[0045] Reference Figure 4 This is a graph showing the change in hollow core diameter with control positive pressure during the tapered section drawing process. Figure 5 This is a graph showing the change in core diameter with controlled negative pressure during the tapered zone drawing process.

[0046] Furthermore, the air pressure variation ratio can be set according to the wire diameter. When the real-time pressure is detected to exceed or fall below the set threshold, the control pressure is adjusted in real time to keep it within the normal pressure control range.

[0047] Furthermore, in step (5), during the entire tapered section drawing process, based on the real-time measurement of the actual fiber diameter at the current drawing position during the tapered section drawing process, a closed-loop feedback control is used to control the drawing speed during the tapered section drawing process, including:

[0048] (5.1) According to The theoretical curve of the required drawing speed as the wire diameter decreases from thick to thin is calculated, where V1 represents the drawing speed at the thick wire end and V2 represents the drawing speed at the thin wire end.

[0049] (5.2) At the initial moment of the conical drawing, the drawing speed is controlled according to the theoretical change curve of the drawing speed;

[0050] (5.3) Measure the actual fiber diameter at the current drawing position during the tapered region drawing process in real time, and compare the actual fiber diameter at the current drawing position with the theoretical fiber diameter at the current drawing position to obtain the fiber diameter deviation value.

[0051] (5.4) Based on the ratio of the wire diameter deviation value and the theoretical speed value at the current drawing position, perform corresponding proportional control on the theoretical speed value, update the drawing speed in the current conical drawing process, return to step (5.5), until the current drawing position is the end point of the conical area, and complete the drawing of the conical area with a length of L3.

[0052] Furthermore, during the drawing process of multi-core hollow tapered optical fiber, fiber coating is also performed simultaneously. During the drawing process of multi-core hollow tapered optical fiber, as the fiber diameter decreases, the thickness of the fiber coating also changes accordingly. The drawing speed continuously increases, and the consumption of coating material changes accordingly. Based on the fiber diameter measured in real time by the fiber diameter measurement system after coating, the coating pressure P is controlled in real time. At the same time, the time for the coated optical fiber to pass through the curing equipment becomes shorter, and the curing power Pow of the curing equipment is also controlled in real time according to the change in drawing speed.

[0053] Furthermore, during the drawing process of multi-core hollow tapered optical fiber, the start and end positions of the multi-core hollow tapered optical fiber are marked simultaneously: when drawing the multi-core hollow tapered optical fiber, the fiber drawing length L at the start of drawing and the length L4 from the fiber drawing output port to the fiber take-up machine are determined; when the fiber drawing length is equal to L+L4, the start position of the multi-core hollow tapered optical fiber is marked at the corresponding position of the fiber; when the fiber drawing length is equal to L+L1+L2+L3+L4, the end position of the multi-core hollow tapered optical fiber is marked at the corresponding position of the fiber.

[0054] In step (5), according to The theoretical curve of fiber diameter change versus drawing speed during the process of fiber diameter reduction from thick to thin was derived, as follows: Figure 3 The figure shows a theoretical curve of fiber diameter change versus drawing speed change during the tapered fiber drawing process, from which the drawing speed is determined based on the fiber diameter. However, in the actual tapered fiber drawing process of multi-core hollow tapered fibers, if... Figure 3 The theoretical curve of fiber diameter variation versus drawing speed variation shown is used for speed control. However, due to system hysteresis and the uniformity of the preform itself, the fiber diameter variation curve will exhibit the following characteristics: Figure 6 The trend shown. From Figure 6 As can be seen, two problems arise: First, the fiber diameter cannot reach the theoretical value at specific lengths; second, the fiber diameter fluctuates near the narrow end due to the butterfly effect caused by the first problem. Solving these problems requires ensuring the fiber diameter changes according to or closely approximates the theoretical value.

[0055] This invention accurately measures the actual fiber diameter in real time throughout the entire process of drawing multi-core hollow tapered optical fibers. The actual fiber diameter is compared with the theoretical fiber diameter to calculate the real-time difference. Based on this difference, the control system performs corresponding proportional control on the theoretical speed value according to the ratio of the difference to the theoretical value, forming a closed-loop control. Feedback control runs through the entire process of drawing multi-core hollow tapered optical fibers, ensuring the accuracy of the drawn multi-core hollow tapered optical fibers.

[0056] Matters not covered in this invention are common knowledge.

[0057] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0058] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating multi-core hollow tapered optical fibers, characterized in that, include: (1) Prepare a multi-core hollow preform. The overall cross-section of the multi-core hollow preform is circular, including a hollow preform located in the center and multiple fiber core preforms surrounding the hollow preform. The dimensions of the multi-core hollow preform include: preform diameter D, fiber core preform diameter D （芯） Hollow preform diameter D （空） ; (2) Determine the dimensional parameters of the multi-core hollow tapered optical fiber to be drawn, including the diameter of the fiber at the thicker end. d (1) Core diameter at the thicker end of the filament d (芯1) Hollow diameter at the thicker end of the wire d (空1) The length L1 of the thicker filament end, and the diameter of the fiber at the thinner filament end. d (2) The core diameter at the filament end d (芯2) Hollow diameter at the tip of the filament d (空2) The length of the thicker end of the filament is L2, and the length of the tapered section where the filament diameter changes from thick to thin is L3. (3) Determine the drawing parameters when drawing the thicker diameter end of the fiber, including the drawing temperature, the preform feeding speed, the fiber drawing speed, and the control positive pressure. and control negative pressure ; Determine the drawing parameters when drawing the filament diameter: determine the drawing temperature, fiber drawing speed, and control positive pressure. and control negative pressure ; Based on the diameter of the thicker end of the optical fiber d (1) Fiber diameter at the thinner filament end d (2) Given the length L3 of the tapered region where the fiber diameter changes from thick to thin, calculate the theoretical curve of the fiber diameter changing from thick to thin in the tapered region, and determine the theoretical fiber diameter at any length position in the tapered region. Controlling the positive pressure when drawing the diameter end of the coarse wire Controlling negative pressure Controlling the positive pressure at the diameter end of the drawn filament and control negative pressure Determine the control positive pressure when drawing the tapered zone. The curve function of fiber diameter variation and control negative pressure Curve function showing the change in fiber diameter; The curve function showing the change of control positive pressure with fiber diameter during the drawing of the tapered region is as follows: in d This represents the actual diameter of the optical fiber at the current drawing position. The curve function showing the change of control negative pressure with fiber diameter during the drawing of the tapered region is as follows: in d This represents the actual diameter of the optical fiber at the current drawing position. (4) Based on the determined drawing parameters when drawing the thicker filament end, the drawing length L1 of the multi-core hollow preform and the fiber diameter at the thicker filament end are determined. d (1) Core diameter at the thicker end of the filament d (芯1) Hollow core diameter at the thicker end of the wire d (空1) The thicker diameter end of a multi-core hollow tapered optical fiber; (5) The end point of the thick wire diameter of the multi-core hollow tapered optical fiber is the starting point of the tapered region to be drawn. The tapered region drawing starts from the starting point of the tapered region. During the entire tapered region drawing process, the positive pressure and negative pressure are controlled according to the curve function of the change of positive pressure with optical fiber diameter and the curve function of the change of negative pressure with optical fiber diameter when drawing the tapered region. At the same time, the drawing speed is controlled by closed-loop feedback based on the actual optical fiber diameter at the current drawing position during the real-time measurement of the tapered region drawing process until the tapered region with a length of L3 is completed. (6) Based on the determined drawing parameters for drawing the filament diameter end, complete the drawing of the filament diameter end with a length of L2.

2. The method for preparing a multi-core hollow tapered optical fiber according to claim 1, characterized in that, Based on the actual fiber diameter at the current drawing position during the real-time measurement of the tapered region drawing process, closed-loop feedback control is used to regulate the drawing speed during the tapered region drawing process, including: (5.1) According to The theoretical curve of the drawing speed required to reduce the wire diameter from coarse to fine was calculated, where Indicates the drawing speed at the diameter end of the thicker wire. Indicates the drawing speed at the diameter end of the filament; (5.2) At the initial moment of the conical drawing, the drawing speed is controlled according to the theoretical change curve of the drawing speed; (5.3) Measure the actual fiber diameter at the current drawing position during the tapered region drawing process in real time, and compare the actual fiber diameter at the current drawing position with the theoretical fiber diameter at the current drawing position to obtain the fiber diameter deviation value. (5.4) Based on the ratio of the wire diameter deviation value and the theoretical speed value at the current drawing position, perform corresponding proportional control on the theoretical speed value, update the drawing speed in the current conical drawing process, return to step (5.5), until the current drawing position is the end point of the conical area, and complete the drawing of the conical area with a length of L3.

3. The method for preparing a multi-core hollow tapered optical fiber according to claim 1, characterized in that, The multi-core hollow preform consists of four fiber core preforms, located at the top, bottom, left, and right positions of the hollow preform. The cladding covers the hollow preform and the fiber core preform, making the overall cross-section of the multi-core hollow preform circular, and the diameter of the multi-core hollow preform is D.

4. The method for fabricating a multi-core hollow tapered optical fiber according to claim 1, 2, or 3, characterized in that, During the drawing process of multi-core hollow tapered optical fiber, fiber coating is also carried out simultaneously. As the fiber diameter decreases during the drawing process, the thickness of the fiber coating also changes accordingly. The drawing speed continuously increases, and the consumption of coating material changes accordingly. Based on the fiber diameter measured in real time by the fiber diameter measurement system after coating, the coating pressure P is controlled in real time. At the same time, the time for the coated fiber to pass through the curing equipment is shortened, and the curing power Pow of the curing equipment is also controlled in real time according to the change of drawing speed.

5. The method for preparing a multi-core hollow tapered optical fiber according to claim 4, characterized in that, During the drawing process of multi-core hollow tapered optical fiber, the start and end positions of the multi-core hollow tapered optical fiber are marked simultaneously: when drawing the multi-core hollow tapered optical fiber, the fiber drawing length L at the start of the drawing process and the length L4 from the fiber drawing output port to the fiber take-up machine are determined; when the fiber drawing length is equal to L+L4, the start position of the multi-core hollow tapered optical fiber is marked at the corresponding position of the fiber; when the fiber drawing length is equal to L+L1+L2+L3+L4, the end position of the multi-core hollow tapered optical fiber is marked at the corresponding position of the fiber.

6. A multi-core hollow tapered optical fiber, characterized in that, The multi-core hollow tapered optical fiber is obtained using the fabrication method described in claim 1, 2, 3, or 5.

7. A laser system, characterized in that, This includes multi-core hollow tapered optical fibers obtained using the fabrication method of multi-core hollow tapered optical fibers as described in claim 1, 2, 3, or 5.

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