Bending-resistant optical fiber and production process thereof

Abstract

The embodiment of the invention provides an anti-bending optical fiber and a production process thereof, and relates to the technical field of optical fibers. The first wrapping layer wraps the core layer; the gradient layer wraps the first wrapping layer; the second wrapping layer wraps the gradient layer; and the refractive indexes of the core layer, the first cladding, the gradient layer and the second cladding are gradually reduced in sequence. According to the bending-resistant optical fiber and the production process thereof provided by the embodiment of the invention, the problem of relatively large bending loss of the optical fiber in the prior art is solved.

Description

Technical Field

[0001] This application relates to the technical field of optical fibers, and particularly relates to a bend-resistant optical fiber and its production process. Background Art

[0002] An optical fiber is a fiber material used to transmit optical signals. Utilizing the principle of total internal reflection of light, the optical signal is transmitted from one end to the other.

[0003] In related technologies, an optical fiber generally includes a core layer and a cladding layer that wraps the core layer. In some scenarios of communication network construction, the optical fiber needs to be bent and installed in a narrow space. At this time, the bending of the optical fiber easily causes some optical signals to fail to complete total internal reflection transmission, resulting in a large bending loss, making it difficult to meet the requirements of network communication. Summary of the Invention

[0004] Embodiments of this application provide a bend-resistant optical fiber and its production process to solve the problem of large bending loss of optical fibers in the prior art.

[0005] In a first aspect, embodiments of this application provide a bend-resistant optical fiber, including:

[0006] A core layer;

[0007] A first cladding layer that wraps the core layer;

[0008] A gradient layer that wraps the first cladding layer;

[0009] A second cladding layer that wraps the gradient layer;

[0010] The refractive indices of the core layer, the first cladding layer, the gradient layer, and the second cladding layer decrease in sequence.

[0011] In a possible implementation manner, the refractive index n1 of the core layer is 0.35% to 0.42%;

[0012] And / or, the refractive index n2 of the first cladding layer is -0.05% to 0;

[0013] And / or, the refractive index n3 of the second cladding layer is -0.4% to -0.2%;

[0014] And / or, the refractive index of the gradient layer shows a decreasing trend between n2 and n3.

[0015] In a second aspect, embodiments of this application provide a production process for a bend-resistant optical fiber, including the following steps:

[0016] Deposit the core layer, the first cladding layer, the gradient layer, and the second cladding layer in sequence to form a loose body;

[0017] Sinter the loose body and complete dehydration and fluorine doping so that the refractive indices of the core layer, the first cladding layer, the gradient layer, and the second cladding layer decrease in sequence.

[0018] In a possible implementation manner, sintering the loose body and completing dehydration and fluorine doping includes:

[0019] Feed the loose body into a sintering device. When the temperature of the loose body is 1000 - 1100 °C, introduce 0.5 - 1.0 slpm of chlorine gas and 0.02 - 0.05 slpm of helium gas to remove moisture by dehydroxylation;

[0020] When the temperature of the loose body is 1000 - 1300 °C, introduce 0.3 - 2.0 slpm of fluoride;

[0021] Wherein, the sintering speed of the loose body is 6 - 15 mm / min.

[0022] In a possible implementation manner, feeding the loose body into a sintering device includes:

[0023] Place the loose body into a sintering device having an air inlet hole and an air outlet hole;

[0024] Control the temperature of the loose body through a heating element in the sintering device.

[0025] In a possible implementation manner, sequentially depositing the core layer, the first cladding layer, the gradient layer, and the second cladding layer to form a loose body includes:

[0026] In the cavity of a deposition device, deposit the core layer, the first cladding layer, the gradient layer, and the second cladding layer respectively through a core layer torch, a first cladding layer torch, a gradient layer torch, and a second cladding layer torch.

[0027] In a possible implementation manner, the core layer torch and the second cladding layer torch are torches with a ring-shaped multi-layer cylindrical structure.

[0028] In a possible implementation manner, the first cladding layer torch and the gradient layer torch are torches with a focusing structure.

[0029] In a possible implementation manner, after sintering the loose body and completing dehydration and fluorine doping, it further includes:

[0030] Vitrify the sintered loose body to form a glass rod;

[0031] Perform an extension treatment on the glass rod to form a core rod;

[0032] Deposit an outer cladding layer on the outside of the core rod and perform overall sintering to obtain an optical fiber preform;

[0033] Draw the drawn fiber preform.

[0034] In a possible implementation, vitrifying the sintered loose body includes:

[0035] When the temperature of the loose body is 1300 - 1500 °C, introduce 0.02 - 0.05 slpm of helium gas for vitrification to form the glass rod.

[0036] An anti - bending optical fiber and its production process provided by an embodiment of the present application. Among them, the anti - bending optical fiber is provided with: a core layer; a first cladding layer that wraps the core layer; a gradient layer that wraps the first cladding layer; a second cladding layer that wraps the gradient layer; and the refractive indices of the core layer, the first cladding layer, the gradient layer, and the second cladding layer decrease in sequence. Thus, by setting the distribution gradient of the refractive index, a refractive index difference is formed between the core layer and each cladding layer, and further, when the optical fiber is bent, the propagation path of light is better restricted, light leakage and loss caused by the bending of the optical fiber are reduced, and the bending loss is effectively controlled, solving the problem of large bending loss of the optical fiber in the prior art; and it also has the advantages of a large mode field diameter, a large effective area, and excellent bending performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings here are incorporated into the description and form a part of this description, showing embodiments that conform to the present application, and are used together with the description to explain the principles of the present application.

[0038] Figure 1 It is a schematic structural diagram of an anti - bending optical fiber provided by the present application;

[0039] Figure 2 For Figure 1 The refractive index curve diagram of the anti - bending optical fiber in

[0040] Figure 3 It is a schematic structural diagram of a deposition device in the production process of an anti - bending optical fiber provided by the present application;

[0041] Figure 4 For Figure 3 The schematic structural diagram of the core layer burner in

[0042] Figure 5 For Figure 4 The side - view sectional view of the core layer burner in

[0043] Figure 6 For Figure 3 The schematic structural diagram of the first cladding layer burner in

[0044] Figure 7Schematic structural diagram of a sintering device in a production process of a bend-resistant optical fiber provided by the present application;

[0045] Figure 8 Refractive index curve diagram of Example 1 in a production process of a bend-resistant optical fiber provided by the present application;

[0046] Figure 9 Refractive index curve diagram of Example 2 in a production process of a bend-resistant optical fiber provided by the present application;

[0047] Figure 10 Refractive index curve diagram of Example 3 in a production process of a bend-resistant optical fiber provided by the present application;

[0048] Figure 11 Refractive index curve diagram of the comparative example in a production process of a bend-resistant optical fiber provided by the present application.

[0049] Explanation of reference numerals:

[0050] 10 - Loose body;

[0051] 20 - Seed rod;

[0052] 100 - Core layer;

[0053] 200 - First cladding;

[0054] 300 - Gradient layer;

[0055] 400 - Second cladding;

[0056] 500 - Deposition device; 510 - Cavity; 520 - Core layer torch; 530 - First cladding torch; 540 - Gradient layer torch; 550 - Second cladding torch; 560 - Air supply part; 570 - Exhaust part;

[0057] 600 - Sintering device; 610 - Air inlet hole; 620 - Air outlet hole; 630 - Heating element.

[0058] Through the above-mentioned drawings, specific embodiments of the present application have been shown, and there will be more detailed descriptions hereinafter. These drawings and text descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. Detailed embodiments

[0059] Exemplary embodiments will be described in detail herein, and examples thereof are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0060] In the related art, an optical fiber generally includes a core layer and a cladding layer that wraps the core layer. In some scenarios of communication network construction, the optical fiber needs to be bent and installed in a narrow space.

[0061] When the optical fiber is bent, energy radiation always occurs along the bending radius direction, and some of the guided modes in the original optical waveguide will invariably become leaky modes, and even some become radiation modes, thus causing bending loss.

[0062] Therefore, the bending of the optical fiber easily causes some optical signals to fail to complete total reflection transmission, and there is a large bending loss, so that it is difficult to meet the requirements of network communication.

[0063] Based on this, the embodiments of the present application provide an anti-bending optical fiber and its production process. The anti-bending optical fiber includes: a core layer; a first cladding layer that wraps the core layer; a gradient layer that wraps the first cladding layer; a second cladding layer that wraps the gradient layer; and the refractive indices of the core layer, the first cladding layer, the gradient layer, and the second cladding layer decrease in sequence. Thus, by setting the distribution gradient of the refractive index, a refractive index difference is formed between the core layer and each cladding layer, and then the optical fiber can better limit the light propagation path when bent, reduce light leakage and loss caused by the bending of the optical fiber, effectively control the bending loss, and solve the problem of large bending loss of the optical fiber in the prior art.

[0064] The technical solutions of the present application and how the technical solutions of the present application solve the above technical problems will be described in detail below with specific embodiments. These specific embodiments below can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below with reference to the accompanying drawings.

[0065] As Figure 1 shown, an anti-bending optical fiber provided by an embodiment of the present application includes:

[0066] a core layer 100;

[0067] a first cladding layer 200 that wraps the core layer 100;

[0068] a gradient layer 300 that wraps the first cladding layer 200;

[0069] The second cladding layer 400 wraps the graded layer 300;

[0070] The refractive indices of the core layer 100, the first cladding layer 200, the graded layer 300, and the second cladding layer 400 decrease in sequence.

[0071] Specifically, as Figure 2 shown, the refractive index n1 of the core layer 100 is 0.35 - 0.42%;

[0072] and / or, the refractive index n2 of the first cladding layer 200 is -0.05% - 0;

[0073] and / or, the refractive index n3 of the second cladding layer 400 is -0.4 - -0.2%;

[0074] and / or, the refractive index of the graded layer 300 shows a decreasing trend between n2 and n3.

[0075] It should be noted that the gradient between the first cladding layer 200 and the second cladding layer 400 of the graded layer 300 forms an angle θ with respect to the x-axis, where θ is between 30° and 90°. Exemplarily, θ can be 30°, 50°, 60°, 70°, 80°, 90° or other values. So that the first cladding layer 200, the graded layer 300, and the second cladding layer 400 form a stepped concave structure from the inside out.

[0076] During implementation, the refractive index n1 of the core layer 100 can be set to 0.35%, 0.38%, 0.40%, 0.41%, 0.42% or other values. The refractive index n2 of the first cladding layer 200 can be set to -0.05%, -0.04%, -0.03%, -0.02%, -0.01%, 0 or other values. The refractive index n3 of the second cladding layer 400 can be set to -0.4%, -0.35%, -0.30%, -0.25%, -0.2% or other values.

[0077] Thus, by setting the distribution gradient of the refractive index, a refractive index difference is formed between the core layer 100 and each cladding layer, thereby enabling the optical fiber to better limit the light propagation path when bent, reducing light leakage and loss caused by fiber bending, effectively controlling the bending loss, and solving the problem of large bending loss of the optical fiber in the prior art; moreover, it also has the advantages of a large mode field diameter, a large effective area, and excellent bending performance.

[0078] During implementation, an outer cladding layer can also be wrapped outside the second cladding layer 400 to ensure the safety of the optical fiber during use.

[0079] It is further noted that through research, it is found that the bending loss α of the optical fiber is related to the refractive index distribution structure parameters of the optical fiber (such as: relative refractive index △, core radius a), that is

[0080]

[0081] where k is a proportionality constant related to the roughness of the fiber contact surface and material properties.

[0082] In the formula, it can be seen that one of the ways to reduce the bending loss is to increase the relative refractive index △ or decrease the core radius a to reduce the fiber bending loss.

[0083] In the embodiments of the present application, the method adopted is to embed a low-refractive-index glass into the inner cladding close to the core or as a trench of the cladding to better confine light in the core, thereby effectively reducing the bending loss of the fiber.

[0084] In summary, the anti-bending fiber provided by the embodiments of the present application forms a refractive index difference between the core layer 100 and each cladding layer by setting the refractive index distribution gradient, so that the fiber can better limit the light propagation path when bent, reduce the light leakage and loss caused by fiber bending, effectively control the bending loss, and solve the problem of large bending loss of the fiber in the prior art; moreover, it also has the advantages of a large mode field diameter, a large effective area, and excellent bending performance.

[0085] A production process of an anti-bending fiber provided by the embodiments of the present application includes the following steps:

[0086] Deposit the core layer 100, the first cladding layer 200, the gradient layer 300, and the second cladding layer 400 in sequence to form a loose body 10;

[0087] Sinter the loose body 10 and complete dehydration and fluorine doping so that the refractive indices of the core layer 100, the first cladding layer 200, the gradient layer 300, and the second cladding layer 400 decrease in sequence.

[0088] After sintering the loose body 10 and completing dehydration and fluorine doping, it further includes:

[0089] Vitrify the sintered loose body 10 to form a glass rod

[0090] Perform an elongation treatment on the glass rod to form a core rod;

[0091] Use the OVD process (i.e., the outside vapor deposition process) to deposit an outer cladding on the outside of the core rod and sinter the whole to obtain a fiber preform;

[0092] Perform a drawing treatment on the fiber preform to obtain an anti-bending fiber.

[0093] Thus, a refractive index difference is formed between the core layer 100 and each cladding layer, so that the fiber can better limit the light propagation path when bent, reduce the light leakage and loss caused by fiber bending, effectively control the bending loss, and solve the problem of large bending loss of the fiber in the prior art

[0094] In some embodiments, the core layer 100, the first cladding layer 200, the graded layer 300, and the second cladding layer 400 are sequentially deposited to form the loose body 10, including:

[0095] Using the VAD process (i.e., the vapor axial deposition process), and in the cavity 510 of the deposition device 500, the core layer 100, the first cladding layer 200, the graded layer 300, and the second cladding layer 400 are respectively deposited through the core layer torch 520, the first cladding layer torch 530, the graded layer torch 540, and the second cladding layer torch 550.

[0096] It should be noted that, as Figure 3 shown, the deposition device 500 includes a cavity 510 and the core layer torch 520, the first cladding layer torch 530, the graded layer torch 540, and the second cladding layer torch 550 which are arranged on the cavity 510 and distributed in sequence from bottom to top. The deposition device 500 further includes an air supply member 560 and an air exhaust member 570. The air supply member 560 and the air exhaust member 570 are respectively arranged on both sides of the cavity 510 and are respectively used for supplying air into the cavity 510 and exhausting the air flow in the cavity 510. Both the air supply member 560 and the air exhaust member 570 can be set as fans.

[0097] During implementation, the carrier (the carrier can be a seed rod 20 or other rods) can be inserted into the cavity 510 from the top and rotated and lifted upward at a set speed. In this embodiment, the carrier is the seed rod 20. Subsequently, control the core layer torch 520 to deposit the core layer 100 at the end of the seed rod 20 first with a preset deposition gas flow rate; then, according to the refractive index profile structure of each cladding layer, control the first cladding layer torch 530 to deposit the first cladding layer 200 with a preset deposition gas flow rate from the inside to the outside in sequence, control the graded layer torch 540 to deposit the graded layer 300 with a preset deposition gas flow rate, and control the second cladding layer torch 550 to deposit the second cladding layer 400 with a preset deposition gas flow rate. Thus, the loose body 10 with the refractive indices of the core layer 100, the first cladding layer 200, the graded layer 300, and the second cladding layer 400 decreasing in sequence is obtained, and then it enters the subsequent processes.

[0098] Furthermore, the core layer torch 520 and the second cladding layer torch 550 are torches with a ring-shaped multi-layer cylindrical structure; the first cladding layer torch 530 and the graded layer torch 540 are torches with a focusing structure.

[0099] In this embodiment, as Figure 4 and Figure 5As shown, the core layer blowtorch 520 and the second cladding blowtorch 550 are both blowtorches with a ring-shaped twelve-layer nozzle structure, which sequentially include a central nozzle, a first-layer annular nozzle, a second-layer annular nozzle, a third-layer annular nozzle, a fourth-layer annular nozzle, a fifth-layer annular nozzle, a sixth-layer annular nozzle, a seventh-layer annular nozzle, an eighth-layer annular nozzle, a ninth-layer annular nozzle, a tenth-layer annular nozzle, and an eleventh-layer annular nozzle from the inside out. Moreover, the nozzle opening of the ring-shaped twelve-layer blowtorch gradually protrudes from the central tube to the seventh ring in a stepped manner, so as to control low-density deposition through this structure.

[0100] In this embodiment, as Figure 6 shown, the first cladding blowtorch 530 and the gradient layer blowtorch 540 are both focused six-fold blowtorches, which sequentially include a central layer, a first layer, a second layer, a third-layer porous focus, a fourth layer, and a fifth layer from the inside out. Thus, the focused six-fold blowtorch deposits by focusing at one point through the third-layer oxygen pipe, so as to achieve high-density deposition control.

[0101] Specifically, the preset gases and gas flow rates in each blowtorch are as follows:

[0102] Core layer blowtorch 520:

[0103] The central nozzle is passed with SiCl 4 gas with a preset flow rate of 2 - 6 g and GeCl 4 gas with a preset flow rate of 0.3 - 0.5 slpm;

[0104] The first-layer annular nozzle is passed with hydrogen with a preset flow rate of 4 - 10 slpm;

[0105] The second-layer annular nozzle is passed with argon with a preset flow rate of 1 - 5 slpm;

[0106] The third-layer annular nozzle is passed with oxygen with a preset flow rate of 10 - 30 slpm;

[0107] The fourth-layer annular nozzle is passed with argon with a preset flow rate of 1 - 6 slpm;

[0108] The fifth-layer annular nozzle is passed with hydrogen with a preset flow rate of 15 - 35 slpm;

[0109] The sixth-layer annular nozzle is passed with argon with a preset flow rate of 1 - 6 slpm;

[0110] The seventh-layer annular nozzle is passed with oxygen with a preset flow rate of 15 - 30 slpm.

[0111] The eighth-layer annular nozzle is passed with argon with a preset flow rate of 1 - 6 slpm;

[0112] The ninth-layer annular nozzle is passed with hydrogen with a preset flow rate of 15 - 35 slpm;

[0113] The tenth-layer annular nozzle is supplied with argon gas at a preset flow rate of 1 to 6 slpm;

[0114] The eleventh-layer annular nozzle is supplied with oxygen gas at a preset flow rate of 15 to 30 slpm.

[0115] The first cladding torch 530:

[0116] The central layer is supplied with SiCl 4 gas at a preset flow rate of 5 to 35 g and 0 to 2 slpm of oxygen gas;

[0117] The first layer is supplied with argon gas at a preset flow rate of 1 to 5 slpm;

[0118] The second layer is supplied with hydrogen gas at a preset flow rate of 60 to 100 slpm;

[0119] The third-layer porous focusing is supplied with oxygen gas at a preset flow rate of 20 to 50 slpm;

[0120] The fourth layer is supplied with argon gas at a preset flow rate of 1 to 6 slpm;

[0121] The fifth layer is supplied with oxygen gas at a preset flow rate of 20 to 50 slpm;

[0122] In the loose body 10, the density of the first cladding 200 is controlled within the range of 0.35 to 0.55 g / cm3.

[0123] The gradient-layer torch 540:

[0124] The central layer is supplied with SiCl 4 gas at a preset flow rate of 1 to 20 g and 2 to 5 slpm of oxygen gas;

[0125] The first layer is supplied with argon gas at a preset flow rate of 1 to 5 slpm;

[0126] The second layer is supplied with hydrogen gas at a preset flow rate of 50 to 100 slpm;

[0127] The third-layer porous focusing is supplied with oxygen gas at a preset flow rate of 20 to 50 slpm;

[0128] The fourth layer is supplied with argon gas at a preset flow rate of 1 to 6 slpm;

[0129] The fifth layer is supplied with oxygen gas at a preset flow rate of 10 to 40 slpm;

[0130] In the loose body 10, the density of the gradient layer 300 is controlled within the range of 0.45 to 0.60 g / cm3.

[0131] The second cladding torch 550:

[0132] The central nozzle is passed through with SiCl having a preset flow rate of 20 to 60 g 4 gas;

[0133] The first layer of annular nozzles is passed through with hydrogen having a preset flow rate of 10 to 40 slpm;

[0134] The second layer of annular nozzles is passed through with argon having a preset flow rate of 1 to 5 slpm;

[0135] The third layer of annular nozzles is passed through with oxygen having a preset flow rate of 20 to 60 slpm;

[0136] The fourth layer of annular nozzles is passed through with argon having a preset flow rate of 1 to 6 slpm;

[0137] The fifth layer of annular nozzles is passed through with hydrogen having a preset flow rate of 40 to 100 slpm;

[0138] The sixth layer of annular nozzles is passed through with argon having a preset flow rate of 1 to 6 slpm;

[0139] The seventh layer of annular nozzles is passed through with oxygen having a preset flow rate of 25 to 60 slpm;

[0140] The eighth layer of annular nozzles is passed through with argon having a preset flow rate of 1 to 6 slpm;

[0141] The ninth layer of annular nozzles is passed through with hydrogen having a preset flow rate of 60 to 120 slpm;

[0142] The tenth layer of annular nozzles is passed through with argon having a preset flow rate of 1 to 6 slpm;

[0143] The eleventh layer of annular nozzles is passed through with oxygen having a preset flow rate of 50 to 120 slpm;

[0144] In the porous body 10, the density of the second cladding 400 is controlled within the range of 0.22 to 0.3 g / cm.

[0145] In addition, during actual implementation, a control system can also be set on the deposition device 500 to control the lifting and rotation of the seed rod 20 through the control system, and at the same time control the preset deposition gas flow rates in the core layer torch 520, the first cladding torch 530, the gradient layer torch 540, and the second cladding torch 550 through the control system, thereby ensuring the stability and reliability of the deposition process.

[0146] In some embodiments, sintering the porous body 10 and completing dehydration and fluorine doping includes:

[0147] Sending the porous body 10 into a sintering device 600. When the temperature of the porous body 10 is 1000 - 1100 °C, introducing 0.5 - 1.0 slpm of chlorine gas and 0.02 - 0.05 slpm of helium gas to remove hydroxyl groups and moisture;

[0148] When the temperature of the porous body 10 is between 1000 and 1300 °C, fluoride is introduced at 0.3 to 2.0 slpm;

[0149] Among them, the sintering speed of the porous body 10 is 6 to 15 mm / min.

[0150] Subsequently, the porous body 10 is vitrified to produce a glass rod with the refractive indices of the core layer 100, the first cladding layer 200, the gradient layer 300, and the second cladding layer 400 decreasing in sequence. Finally, an anti-bending optical fiber can be made through subsequent processes.

[0151] In some embodiments, feeding the porous body 10 into the sintering device 600 includes:

[0152] Placing the porous body 10 into the sintering device 600 having an air inlet hole 610 and an air outlet hole 620;

[0153] Controlling the temperature of the porous body 10 through the heating element 630 in the sintering device 600.

[0154] It should be noted that as Figure 7 shown, the adopted sintering device 600 includes a hollow main body and a heating element 630 arranged on the main body to heat the porous body 10 through the heating element 630; the main body also has an air inlet hole 610 and an air outlet hole 620 communicating with the internal space. The air inlet hole 610 is located at the bottom of the main body, and the air outlet hole 620 is located at the top of the main body. Among them, the material of the heating element 630 can be graphite, ceramics, resistance wire or other materials, and there is no limitation on this.

[0155] During implementation, the porous body 10 is fed to the heating element 630 in the sintering device 600, and then chlorine gas and helium gas are introduced from the air inlet hole 610. After submerging the porous body 10, they are discharged from the air outlet hole 620. At the same time, the temperature required for sintering is controlled through the heating element 630 to achieve the corresponding dehydration and fluorine doping effects.

[0156] Secondly, vitrifying the sintered porous body 10 includes:

[0157] In the sintering device 600, when the temperature of the porous body 10 is between 1300 and 1500 °C, helium gas at 0.02 to 0.05 slpm is introduced for vitrification to form the glass rod. That is, a glass rod with the refractive indices of the core layer 100, the first cladding layer 200, the gradient layer 300, and the second cladding layer 400 decreasing in sequence is obtained. Finally, the glass rod is sent to subsequent processes to make an anti-bending optical fiber.

[0158] In some embodiments, drawing the optical fiber preform includes:

[0159] Take the tip and the tail handle part of the optical fiber preform to obtain a feedstock head, perform a cross-section test on the feedstock head to obtain corresponding test parameters, and then reasonably control the drawing process according to the test parameters. Thus, the smooth progress of the drawing process can be ensured.

[0160] In addition, the present invention is described in detail through embodiments, and the present invention includes but is not limited to the following several embodiments. The production processes adopted in the following embodiments and comparative examples are as follows:

[0161] Utilize the VAD process and deposit the core layer 100, the first cladding layer 200, the gradient layer 300, and the second cladding layer 400 in sequence through the deposition device 500 to form a porous body 10;

[0162] Sinter the porous body 10 and complete dehydration and fluorine doping so that the refractive indices of the core layer 100, the first cladding layer 200, the gradient layer 300, and the second cladding layer 400 decrease in sequence;

[0163] Vitrify the porous body 10 to form a glass rod.

[0164] After forming the glass rod, perform an elongation treatment on the glass rod to form a core rod;

[0165] Utilize the OVD process to deposit an outer cladding on the outside of the core rod and sinter the whole to obtain an optical fiber preform;

[0166] Take the tip and the tail handle part of the optical fiber preform to obtain a feedstock head, perform a cross-section test on the feedstock head to obtain corresponding test parameters;

[0167] Then, perform a drawing treatment on the optical fiber preform according to the test parameters to obtain a bend-resistant optical fiber.

[0168] Among them, the deposition devices 500 adopted in the embodiments all have a core layer burner 520, a first cladding layer burner 530, a gradient layer burner 540, and a second cladding layer burner 550. In the deposition device 500 adopted in the comparative example, except that the gradient layer burner 540 is not provided, the others are the same as those in the embodiment.

[0169] In each of the embodiments and the comparative example, the gases and preset flow rates in each spray hole of each burner are as follows:

[0170] Table 1. Flow rate table of the core layer burner

[0171]

[0172] Table 2. Flow rate table of the first cladding layer burner

[0173]

[0174] Table 3. Flow rate table of the gradient layer burner

[0175]

[0176] Table 4. Flow Rate Table of the Second Cladding Torch

[0177]

[0178] Example 1:

[0179] As shown in Table 1 - 4, the flow rate of the core layer torch 520 is set as follows:

[0180] The central nozzle is passed with SiCl 4 gas with a preset flow rate of 3 g and GeCl 4 gas with a preset flow rate of 0.30 slpm;

[0181] The first - layer annular nozzle is passed with hydrogen with a preset flow rate of 5 slpm;

[0182] The second - layer annular nozzle is passed with argon with a preset flow rate of 2.2 slpm;

[0183] The third - layer annular nozzle is passed with oxygen with a preset flow rate of 15 slpm;

[0184] The fourth - layer annular nozzle is passed with argon with a preset flow rate of 3.5 slpm;

[0185] The fifth - layer annular nozzle is passed with hydrogen with a preset flow rate of 20 slpm;

[0186] The sixth - layer annular nozzle is passed with argon with a preset flow rate of 4.0 slpm;

[0187] The seventh - layer annular nozzle is passed with oxygen with a preset flow rate of 20 slpm.

[0188] The flow rate of the first cladding torch 530 is set as follows:

[0189] The central layer is passed with SiCl 4 gas and 1.0 slpm of oxygen;

[0190] The first layer is passed with argon with a preset flow rate of 1.0 slpm;

[0191] The second layer is passed with hydrogen with a preset flow rate of 80 slpm;

[0192] The third - layer multi - hole focusing is passed with oxygen with a preset flow rate of 30 slpm;

[0193] The fourth layer is passed with argon with a preset flow rate of 5 slpm;

[0194] The fifth layer is passed with oxygen with a preset flow rate of 25 slpm.

[0195] The flow rate of the tapered layer torch 540 is set as follows:

[0196] The central layer is supplied with SiCl with a preset flow rate of 5 g 4 gas and 6 slpm of oxygen;

[0197] The first layer is supplied with argon with a preset flow rate of 2.3 slpm;

[0198] The second layer is supplied with hydrogen with a preset flow rate of 70 slpm;

[0199] The third layer of porous focusing is supplied with oxygen with a preset flow rate of 25 slpm;

[0200] The fourth layer is supplied with argon with a preset flow rate of 5 slpm;

[0201] The fifth layer is supplied with oxygen with a preset flow rate of 20 slpm.

[0202] The flow rate setting of the second cladding torch 550 is:

[0203] The central nozzle is supplied with SiCl with a preset flow rate of 35 g 4 gas;

[0204] The first layer of annular nozzles is supplied with hydrogen with a preset flow rate of 8 slpm;

[0205] The second layer of annular nozzles is supplied with argon with a preset flow rate of 3.5 slpm;

[0206] The third layer of annular nozzles is supplied with oxygen with a preset flow rate of 20 slpm;

[0207] The fourth layer of annular nozzles is supplied with argon with a preset flow rate of 5 slpm;

[0208] The fifth layer of annular nozzles is supplied with hydrogen with a preset flow rate of 60 slpm;

[0209] The sixth layer of annular nozzles is supplied with argon with a preset flow rate of 5 slpm;

[0210] The seventh layer of annular nozzles is supplied with oxygen with a preset flow rate of 30 slpm.

[0211] Example 2:

[0212] As shown in Table 1-4, the flow rate setting of the core layer torch 520 is:

[0213] The central nozzle is supplied with SiCl with a preset flow rate of 3 g 4 gas and GeCl with a preset flow rate of 0.32 slpm 4 gas; The preset flow rates of other nozzles are the same as those in Example 1.

[0214] The flow rate setting of the first cladding torch 530 is:

[0215] The first layer is passed with argon gas at a preset flow rate of 1.1 slpm; the preset flow rates passed through the other layers are the same as those in Example 1.

[0216] The flow rate setting of the gradient layer torch 540 is:

[0217] The central layer is passed with SiCl with a preset flow rate of 10 g 4 gas and 7 slpm of oxygen; the second layer is passed with hydrogen gas at a preset flow rate of 75 slpm; the preset flow rates passed through the other layers are the same as those in Example 1.

[0218] The flow rate setting of the second cladding torch 550 is:

[0219] The preset flow rate of each spray hole is the same as that in Example 1.

[0220] Example 3:

[0221] As shown in Table 1-4, the flow rate setting of the core layer torch 520 is:

[0222] The central spray hole is passed with SiCl with a preset flow rate of 3 g 4 gas and GeCl with a preset flow rate of 0.35 slpm 4 gas; the preset flow rates of the other spray holes are the same as those in Example 1.

[0223] The flow rate setting of the first cladding torch 530 is:

[0224] The central layer is passed with SiCl with a preset flow rate of 10 g 4 gas and 2.0 slpm of oxygen; the first layer is passed with argon gas at a preset flow rate of 1.5 slpm; the preset flow rates passed through the other layers are the same as those in Example 1.

[0225] The flow rate setting of the gradient layer torch 540 is:

[0226] The central layer is passed with SiCl with a preset flow rate of 10 g 4 gas and 8 slpm of oxygen; the second layer is passed with hydrogen gas at a preset flow rate of 80 slpm; the preset flow rates passed through the other layers are the same as those in Example 1.

[0227] The flow rate setting of the second cladding torch 550 is:

[0228] The preset flow rate of each spray hole is the same as that in Example 1.

[0229] Comparative example:

[0230] As shown in Table 1-4, the flow rate setting of the core layer torch 520 is:

[0231] The central spray hole is passed with SiCl with a preset flow rate of 3 g 4The gas and GeCl with a preset flow rate of 0.38 slpm 4 gas; the preset flow rates of the other spray holes are the same as those in Example 1.

[0232] The flow rate setting of the first cladding torch 530 is:

[0233] The central layer is passed with SiCl with a preset flow rate of 30 g 4 gas and 2 slpm of oxygen; the first layer is passed with 2 slpm of argon; the second layer is passed with 90 slpm of hydrogen; the preset flow rates passed through the other layers are the same as those in Example 1.

[0234] The gradient layer torch 540 is not set.

[0235] The flow rate setting of the second cladding torch 550 is:

[0236] The preset flow rate of each spray hole is the same as that in Example 1.

[0237] As shown in Table 5, for the parameters during sintering and dehydration: the temperatures, chlorine flow rates, and helium flow rates in each example and the comparative example are the same.

[0238] Table 5. Parameter Table during Sintering and Dehydration

[0239]

[0240] As shown in Table 6, for the parameters during sintering with fluorine doping: the temperature of each example is preset to 1250 °C, and the temperature of the comparative example is preset to 1040 °C; the fluorine flow rate, helium flow rate, moving speed, and other parameters in each example and the comparative example are the same.

[0241] Table 6. Parameter Table during Sintering with Fluorine Doping

[0242]

[0243] As shown in Table 7, for the parameters during vitrification: the temperatures and helium flow rates in each example and the comparative example are the same.

[0244] Table 7. Parameter Table during Vitrification

[0245]

[0246] Finally, the heads of the fiber preforms processed in each example and the comparative example are subjected to a cross-section test, and the corresponding test parameters are shown in Table 8 and Figure 3 as shown, and the fiber parameters obtained are shown in Table 9 and Figures 8 - 11 as shown:

[0247] Table 8. Cross-Section Parameter Table

[0248]

[0249] Table 9. Optical fiber parameters

[0250]

[0251] It can be seen that for the anti-bending optical fiber prepared by the production process provided in the embodiments of the present application, a refractive index difference is formed between the core layer 100, the first cladding layer 200, the gradient layer 300, and the second cladding layer 400. As a result, the optical fiber can better limit the light propagation path when bent, reduce light leakage and loss caused by the bending of the optical fiber, effectively control the bending loss, and solve the problem of large bending loss of the optical fiber in the prior art. Moreover, as can be seen from Table 9, this anti-bending optical fiber also has the advantages of a large mode field diameter, a large effective area, excellent bending performance, and compatibility with conventional optical fibers.

[0252] Finally, it should be noted that those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention, which follow the general principles of the present invention and include common general knowledge or conventional technical means in the technical field not disclosed in the present invention. It is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A bend-resistant optical fiber, characterized in that: include: Core layer (100); A first cladding layer (200), the first cladding layer (200) wrapping the core layer (100); a gradient layer (300), the gradient layer (300) wrapping the first cladding layer (200); A second cladding layer (400), the second cladding layer (400) wrapping the gradient layer (300); The refractive indices of the core layer (100), the first cladding layer (200), the graded layer (300), and the second cladding layer (400) decrease in sequence.

2. The bend-resistant optical fiber according to claim 1, characterized in that: The refractive index n1 of the core layer (100) is 0.35-0.42%; And / or, the refractive index n2 of the first cladding (200) is -0.05% to 0; And / or, the refractive index n3 of the second cladding (400) is -0.4 to -0.2%; And / or, the refractive index of the gradient layer (300) shows a decreasing trend between n2 and n3.

3. A process for producing the bend-resistant optical fiber according to claim 1 or 2, characterized in that: The following steps are involved: Depositing a core layer (100), a first cladding layer (200), a gradient layer (300), and a second cladding layer (400) in sequence to form a loose body (10); The loose body (10) is sintered, dehydrated and doped with fluorine, so that the refractive indices of the core layer (100), the first cladding layer (200), the gradient layer (300) and the second cladding layer (400) decrease in sequence.

4. The production process according to claim 3, characterized in that: The step of sintering the loose body (10) and completing dehydration and fluorine doping comprises: The loose body (10) is fed into a sintering device (600), and when the temperature of the loose body (10) is between 1000°C and 1100°C, 0.5 to 1.0 slpm of chlorine gas and 0.02 to 0.05 slpm of helium gas are introduced to remove hydroxylation and moisture; When the temperature of the loose body (10) is between 1000°C and 1300°C, 0.3 to 2.0 slpm of fluoride is introduced; Wherein, the sintering speed of the loose body (10) is 6-15 mm / min.

5. The production process according to claim 4, characterized in that: The step of feeding the loose body (10) into a sintering device (600) comprises: The loose body (10) is placed in a sintering device (600) having an air inlet (610) and an air outlet (620); The temperature of the loose body (10) is controlled by a heating body (630) in the sintering device (600).

6. The production process according to claim 3, characterized in that: The sequentially depositing of a core layer (100), a first cladding layer (200), a gradient layer (300), and a second cladding layer (400) to form a loose body (10) comprises: In a cavity (510) of a deposition device (500), the core layer (100), the first cladding (200), the gradient layer (300) and the second cladding (400) are deposited respectively by a core layer burner (520), a first cladding burner (530), a gradient layer burner (540) and a second cladding burner (550).

7. The production process according to claim 6, characterized in that: The core layer burner (520) and the second cladding layer burner (550) are burners with annular multi-layer cylindrical structures.

8. The production process according to claim 6, characterized in that: The first cladding layer blowtorch (530) and the gradient layer blowtorch (540) are blowtorches with focusing structures.

9. The production process according to claim 3, characterized in that: After the loose body (10) is sintered, dehydrated and doped with fluorine, the method further comprises: vitrifying the sintered loose body (10) to form a glass rod; Extending the glass rod to form a core rod; Depositing an outer cladding layer on the outer side of the core rod, and sintering the whole to obtain an optical fiber preform rod; The optical fiber preform is subjected to a drawing process.

10. The production process according to claim 9, characterized in that: The vitrification of the sintered loose body (10) comprises: When the temperature of the loose body (10) is between 1300°C and 1500°C, 0.02 to 0.05 slpm of helium is introduced to vitrify the loose body (10) to form the glass rod.

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