Refractive index stepped sleeve and preparation method and manufacturing equipment thereof

Abstract

The invention provides a refractive index stepped sleeve and a preparation method and manufacturing equipment thereof, and the preparation method comprises the following steps: S1, depositing silicon dioxide quartz powder on the surface of a guide rod by using a core-pulling tube external vapor deposition method, and setting different combustion gas flows in the deposition process, obtaining inner and outer region loose bodies and a densified glass layer for isolating the inner and outer region loose bodies; s2, dehydrating and purifying the loose body to obtain the dehydrated and purified loose body; s3, fluoride gas is introduced into the center hole and the peripheral part of the dehydrated and purified loose body, fluorine doping is carried out at the set temperature by controlling the gas flow, and fluorine-doped sleeves with different internal and external refractive indexes are obtained; therefore, the preparation process flow is simplified, the manufacturing cost is reduced, the refractive index profile of the refractive index stepped sleeve has a stepped characteristic, and the refractive index stepped sleeve has wide applicability.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber preform rods, and in particular to a refractive index step-type sleeve and a preparation method and manufacturing equipment thereof. Background Art

[0002] In high-tech fields such as optical communications, fiber optic sensing, and laser technology, refractive index step-type tubes, as a key optical component, play a vital role. Through their unique refractive index distribution characteristics, this type of tube can achieve precise control and guidance of optical signals, thereby improving the overall performance and efficiency of the optical system. However, traditional methods for preparing refractive index step-type tubes often face problems such as complex process flow, high manufacturing costs, and difficulty in controlling the refractive index profile, which to some extent limit their wider application and development.

[0003] Specifically, traditional preparation methods usually involve multiple cumbersome steps, such as the sequential deposition of multiple layers of materials, complex heat treatment processes, and precise refractive index control. These steps not only increase the difficulty and time cost of production, but may also lead to problems with the unevenness and stability of the refractive index distribution. In addition, in order to achieve a step-change in the refractive index, it is often necessary to use a variety of materials with different refractive indices, and control the refractive index difference between the layers through precise lamination and heat treatment techniques. The implementation of this method not only requires high-precision equipment and strict process control, but also relatively high material costs and energy consumption.

[0004] In recent years, with the rapid development of optical technology and the continuous growth of application demand, the requirements for refractive index step-type tubes have become increasingly higher. Not only are they required to have excellent optical properties, such as high light transmittance, low loss, and stable refractive index distribution, but they are also required to have a simple preparation process and controllable costs to meet the needs of large-scale production and wide application.

[0005] It is worth noting that, although the prior art, such as the invention patent with publication number CN103951182B, introduces a process combining improved chemical vapor deposition (MCVD) and outside-the-tube vapor deposition (OVD) to manufacture deep refractive index and complex refractive index profile sleeves, during the powder vitrification process of this method, the fluorine element will diffuse along the fluorine concentration gradient and the powder density gradient, resulting in the inability to obtain a sleeve with a step-type refractive index profile, which limits its application scope to a certain extent.

[0006] The disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application, nor does it necessarily provide technical guidance. In the absence of clear evidence that the above content has been disclosed before the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of the present application. Summary of the invention

[0007] In order to solve the above technical problems, the present invention proposes a refractive index step-type sleeve and a preparation method and manufacturing equipment thereof, which not only simplifies the preparation process and reduces the manufacturing cost, but also realizes that the refractive index profile of the refractive index step-type sleeve achieves a step-type characteristic and has wide applicability.

[0008] In order to achieve the above object, the technical solution of the present invention is as follows:

[0009] The present invention provides a method for preparing a refractive index step-type sleeve, comprising the following steps:

[0010] S1 uses the core-pulling tube external vapor deposition method to deposit silicon dioxide quartz powder on the surface of the guide rod, and sets different combustion gas flow rates during the deposition process to obtain loose bodies in the inner and outer regions and a densified glass layer that isolates the loose bodies in the inner and outer regions;

[0011] S2 dehydrates and purifies the loose body to obtain a dehydrated and purified loose body;

[0012] S3 introduces fluoride gas into the central hole and the outer part of the loose body after dehydration and purification, and performs fluorine doping at a set temperature by controlling the gas flow rate to obtain a fluorine-doped sleeve with different refractive indices inside and outside.

[0013] The present invention proposes a refractive index step-type sleeve and a preparation method and manufacturing equipment thereof, which not only simplify the preparation process and reduce the manufacturing cost, but also realize that the refractive index profile of the refractive index step-type sleeve achieves a step-type characteristic and has wide applicability.

[0014] As a preferred technical solution, the densified glass layer deposited between the loose bodies in the inner and outer regions for isolation in step S1 includes the following preparation steps:

[0015] When the thickness of the cladding in the loose body reaches the target thickness during the deposition process, the silicon-based raw material in the blowtorch is shut down, and the flow rate of the combustion gas is increased to 120% to 150% of the flow rate of the combustion gas for depositing the loose body. The baking time is controlled at 0.5 to 2 minutes, and a densified glass layer is deposited;

[0016] The silicon-based raw material is silicon tetrachloride or organosilicon, and the combustion gas is methane and / or hydrogen.

[0017] As a preferred technical solution, the density of the densified glass layer deposited in step S1 is 1.8 to 2.2 g / cm 3 , with a thickness of 0.1 to 0.5 mm. The loose bodies in the inner and outer regions include: a loose inner cladding and a loose outer cladding. The density of the deposited loose inner cladding is 0.3 to 0.6 g / cm3 The density of the deposited loose outer cladding is 0.3-0.6 g / cm 3 .

[0018] As a preferred technical solution, the fluoride gas introduced in step S3 is a refractive index increasing doping compound gas or a refractive index decreasing doping compound gas, wherein the refractive index increasing doping compound gas includes: any one of germanium tetrachloride, phosphorus oxychloride and silicon tetrachloride, and the refractive index decreasing doping compound gas includes: any one of carbon tetrafluoride, silicon tetrafluoride, hexafluoroethane and hexafluoroethylene silicon.

[0019] As a preferred technical solution, the setting temperature for fluorine doping in step S3 includes:

[0020] The set temperature of the first temperature zone is 800℃~900℃;

[0021] The second temperature zone is set at 800℃~900℃;

[0022] The set temperature of the third temperature zone is 1300℃~1350℃.

[0023] As a preferred technical solution, the flow rate of the fluorine-doped gas in step S3 is 0.1 to 18 slpm.

[0024] As a preferred technical solution, step S3 introduces fluoride gas into the central hole and the peripheral part of the loose body, and fluorine is doped at a certain temperature by controlling the gas flow rate to obtain a fluorine-doped sleeve with different refractive indices inside and outside, which specifically includes the following steps:

[0025] The rotation speed of the loose body is controlled, the temperatures of the first temperature zone, the second temperature zone and the third temperature zone are set, the flow rate of the fluoride gas introduced into the central hole of the loose body is 0.9-1.5 slpm, the pressure of the mixed gas in the central hole of the loose body is controlled at 60-80 pa, and the flow rate of the helium is adjusted to 1-2 slpm; at the same time, the flow rate of the fluoride gas introduced into the outer part of the loose body is 0.3-0.5 slpm, the flow rate of the helium is 14-16 slpm, the loose body descends at a speed of 4-6 mm / min, and the vitrification is completed during the contraction process to obtain a glass rod;

[0026] The glass rod is degassed at 1050-1150° C. for 14-18 hours to obtain a fluorine-doped sleeve with different inner and outer refractive indices.

[0027] As a preferred technical solution, the following steps are also included:

[0028] S4 cuts off the head and tail cones of the fluorine-doped sleeve with different inner and outer refractive indices, and then performs boring processing to obtain a refractive index step-type sleeve.

[0029] The present invention also provides a refractive index step-type sleeve, which is prepared according to the preparation method of the refractive index step-type sleeve as described in any one of the above items.

[0030] The present invention also provides a manufacturing device for a refractive index step-type sleeve, and a method for manufacturing a refractive index step-type sleeve as described in any of the above items, comprising: a lead rod, the lead rod being hollow, one end of the lead rod passing through one end of a furnace core tube and entering the interior of the furnace core tube, the lead rod portion inside the furnace core tube being deposited with a loose inner cladding and a loose outer cladding, and a densified glass layer between the loose inner cladding and the loose outer cladding, the other end of the furnace core tube being provided with a furnace core tube air inlet, and the lead rod being sealed and connected to the loose body through a connecting sleeve.

[0031] The present invention provides a refractive index step-type sleeve and a preparation method and manufacturing equipment thereof, which have the following beneficial effects:

[0032] 1) It not only simplifies the preparation process and reduces the manufacturing cost, but also realizes that the refractive index profile of the refractive index step-type sleeve has a step-type characteristic and has wide applicability;

[0033] 2) The present invention adopts a loose body produced by a core pulling process to manufacture a casing. After vitrification, the finished casing can be obtained by cutting off the head and tail cones and boring holes. The material utilization rate reaches more than 95%, effectively reducing the manufacturing cost;

[0034] The inner and outer regions of the loose body are doped simultaneously to increase the refractive index of the doping compound gas or reduce the refractive index of the doping compound gas. Compared with the process of preparing cladding layers with different refractive indices layer by layer, the process flow is simplified. The doping and vitrification are carried out simultaneously, the production time can be shortened by 50%, and the manufacturing cost is reduced.

[0035] The refractive index profile of the prepared refractive index step-type casing achieves step-type characteristics and can be directly applied in the fields of special optical fibers, ultra-low loss optical fibers, and bend-resistant optical fibers, thereby reducing the difficulty of optical fiber manufacturing and ultimately reducing the manufacturing cost of optical fiber products. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic structural diagram of a refractive index step-type sleeve manufacturing device provided by the present invention;

[0037] Figure 2 A refractive index profile diagram of a refractive index step-type sleeve provided by the present invention;

[0038] Among them: 1-lead rod; 2-connecting sleeve; 3-inner cladding of loose body; 4-densified glass layer; 5-outer cladding of loose body; 6-air inlet of furnace core tube; 7-furnace core tube; 8-first temperature zone; 9-second temperature zone; 10-third temperature zone; 11-lead rod plug. DETAILED DESCRIPTION

[0039] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0040] The present invention provides a method for preparing a refractive index step-type sleeve, comprising the following steps:

[0041] S1 uses a core-pulling tube external vapor deposition method to deposit silicon dioxide quartz powder on the surface of the guide rod 1, and sets different combustion gas flow rates during the deposition process to obtain loose bodies in the inner and outer regions and a densified glass layer 4 that isolates the loose bodies in the inner and outer regions;

[0042] S2 dehydrates and purifies the loose body to obtain a dehydrated and purified loose body;

[0043] S3 introduces fluoride gas into the central hole and the outer part of the loose body after dehydration and purification, and performs fluorine doping at a set temperature by controlling the gas flow rate to obtain a fluorine-doped sleeve with different refractive indices inside and outside.

[0044] The present invention proposes a refractive index step-type sleeve and a preparation method and manufacturing equipment thereof, which not only simplify the preparation process and reduce the manufacturing cost, but also realize that the refractive index profile of the refractive index step-type sleeve achieves a step-type characteristic and has wide applicability.

[0045] Preferably, the densified glass layer 4 deposited between the loose bodies in the inner and outer regions for insulation in step S1 comprises the following preparation steps:

[0046] During the deposition process, when the thickness of the cladding 3 in the loose body reaches the target thickness, the silicon-based raw material in the blowtorch is shut down, and the flow rate of the combustion gas is increased to 120% to 150% of the flow rate of the combustion gas for depositing the loose body, and the baking time is controlled at 0.5 to 2 minutes, and a densified glass layer 4 is deposited;

[0047] The silicon-based raw material is silicon tetrachloride or organosilicon, and the combustion gas is methane and / or hydrogen.

[0048] Preferably, the density of the densified glass layer 4 deposited in step S1 is 1.8-2.2 g / cm 3 , with a thickness of 0.1-0.5 mm. The loose bodies in the inner and outer regions include: a loose inner cladding 3 and a loose outer cladding 5. The density of the deposited loose inner cladding 3 is 0.3-0.6 g / cm 3 The density of the deposited loose outer cladding 5 is 0.3-0.6 g / cm 3 .

[0049] Preferably, the fluoride gas introduced in step S3 is a refractive index increasing doping compound gas or a refractive index decreasing doping compound gas, and the refractive index increasing doping compound gas includes: any one of germanium tetrachloride, phosphorus oxychloride and silicon tetrachloride. Through an external bubbling tank, an inert gas carrier is used, and the inert gas is introduced into the raw material of the bubbling tank. A part of the liquid material is gasified and mixed with the inert gas. The amount of the raw material is controlled by the carrier gas flow control. The pipeline is connected to the guide rod 1 through a joint; the refractive index increasing doping compound gas enters the central hole of the guide rod 1 and the furnace core tube air inlet 6 through the pipeline in a gas carrier mode, and then enters the central hole and the peripheral part of the loose body. According to the refractive index target to be prepared, the flow rate of the carrier inert gas is set, and the gas flow rate is controlled by a mass flow controller (MFC). After the purification of the silica powder is completed, the carrier gas is carried according to the set flow rate, and the carrier gas enters the central hole and the peripheral part of the purified loose body through the pipeline and the central hole of the guide rod 1 in turn, and the powder is vitrified at high temperature and the doping is completed;

[0050] The refractive index reducing doping compound gas includes: any one of carbon tetrafluoride, silicon tetrafluoride, hexafluoroethane and hexafluoroethylene silicon. Since the refractive index reducing doping compound gas is in gaseous state at room temperature, a gas mass flow controller (MFC) controls the flow rate of the refractive index reducing doping compound gas into a pipeline, and the pipeline is connected to the central hole of the guide rod 1. The refractive index reducing doping compound gas enters the interior of the loose body through the central hole of the guide rod 1 and diffuses. Another gas mass flow controller (MFC) controls a certain flow rate to allow the refractive index reducing doping compound gas to enter the furnace core tube 7 through the furnace core tube air inlet 6, and the refractive index reducing doping compound gas diffuses in the outer part of the loose body.

[0051] After the doping gas enters the interior of the loose body and is sintered, it has the function of reducing or increasing the refractive index. Fluoride gas is introduced into the central hole and the outer part of the loose body, and fluorine is doped at a set temperature by controlling the gas flow rate to obtain a fluorine-doped sleeve with different refractive indices inside and outside, thereby obtaining a sleeve with different refractive indices inside and outside;

[0052] Preferably, the setting temperature for fluorine doping in step S3 includes:

[0053] The set temperature of the first temperature zone 8 is 800° C. to 900° C., and the set temperature of the first temperature zone 8 is preferably 800° C., 850° C. and 900° C. Due to space limitations and for simplicity, the present invention will no longer exhaustively list the specific point values ​​included in the range;

[0054] The second temperature zone 9 is set at a temperature of 800° C. to 900° C., and the second temperature zone 9 is preferably set at 800° C., 850° C. and 900° C. Due to space limitations and for simplicity, the present invention will no longer exhaustively list the specific point values ​​included in the range;

[0055] The set temperature of the third temperature zone 10 is 1300°C to 1350°C, and the set temperature of the third temperature zone 10 is preferably 1300°C, 1320°C and 1350°C. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0056] Preferably, the flow rate of the fluorine-doped gas in step S3 is 0.1-18 slpm.

[0057] Preferably, step S3 introduces fluoride gas into the central hole and the peripheral part of the loose body, controls the gas flow rate and performs fluorine doping at a certain temperature to obtain a fluorine-doped sleeve with different inner and outer refractive indices, which specifically includes the following steps:

[0058] The rotation speed of the loose body is controlled, the temperatures of the first temperature zone 8, the second temperature zone 9 and the third temperature zone 10 are set, the flow rate of the fluoride gas introduced into the central hole of the loose body is 0.9-1.5 slpm, the pressure of the mixed gas in the central hole of the loose body is controlled at 60-80 pa, and the flow rate of the helium is adjusted to 1-2 slpm; at the same time, the flow rate of the fluoride gas introduced into the outer part of the loose body is 0.3-0.5 slpm, the flow rate of the helium is 14-16 slpm, the loose body descends at a speed of 4-6 mm / min, and the vitrification is completed during the contraction process to obtain a glass rod;

[0059] The glass rod is degassed at 1050-1150° C. for 14-18 hours to obtain a fluorine-doped sleeve with different inner and outer refractive indices.

[0060] Preferably, the method further comprises the following steps:

[0061] S4 cuts off the head and tail cones of the fluorine-doped sleeve with different inner and outer refractive indices, and then performs boring processing to obtain a refractive index step-type sleeve.

[0062] The present invention also provides a refractive index step-type sleeve, which is prepared according to the preparation method of the refractive index step-type sleeve as described in any one of the above items.

[0063] like Figure 1As shown, the present invention also provides a manufacturing device for a refractive index step-type sleeve, and the manufacturing method for implementing the refractive index step-type sleeve as described in any one of the above items includes: a guide rod 1, the guide rod 1 is a hollow inner cavity, and a central control is provided on the hollow inner cavity, one end of the guide rod 1 passes through one end of a furnace core tube 7 and enters the interior of the furnace core tube 7, the guide rod 1 part inside the furnace core tube 7 is deposited with a loose inner cladding 3 and a loose outer cladding 5 and a densified glass layer 4 between the loose inner cladding 3 and the loose outer cladding 5, the other end of the furnace core tube 7 is provided with a furnace core tube air inlet 6, the guide rod 1 is sealed and connected to the loose body through a connecting sleeve 2, and gas diffusion with the outside cannot be carried out during the doping process, and the furnace core tube 7 is provided with a first temperature zone 8, a second temperature zone 9 and a third temperature zone 10.

[0064] Example 1

[0065] The present invention provides a method for preparing a refractive index step-type sleeve, comprising the following steps:

[0066] S1 uses the core-pulling tube vapor deposition method, using organic silicon (D4), methane and oxygen as raw materials to deposit silica quartz powder on the surface of the guide rod 1. During the deposition process, the thickness of the cladding 3 in the loose body is monitored to reach the target thickness. The deposition thickness of the cladding 3 in the loose body is 80mm, and the density of the cladding 3 in the loose body is 0.426g / cm 3 , the organic silicon (D4) in the blowtorch is turned off, and the flow rates of methane and oxygen are increased to 135% of the combustion gas flow rate of the deposited loose body. The baking time is controlled at 1 min, and the densified glass layer 4 is deposited. When the thickness of the densified glass layer 4 reaches the target thickness during the deposition process, the density of the densified glass layer 4 is 2 g / cm 3 , the thickness of the densified glass layer 4 is 0.3 mm, the organic silicon (D4) in the blowtorch is turned off, and the flow rates of methane and oxygen are reduced to the combustion gas flow rates of the deposited loose body. When the thickness of the outer cladding 5 of the loose body is monitored to reach the target thickness during the deposition process, the deposition thickness of the outer cladding 5 of the loose body is 295 mm, and the density of the outer cladding 5 of the loose body is 0.456 g / cm3, and the inner cladding 3 of the loose body and the outer cladding 5 of the loose body and the densified glass layer 4 for insulation between the inner cladding 3 of the loose body and the outer cladding 5 of the loose body are obtained;

[0067] S2: put the loose body into the furnace core tube 7, control the rotation speed of the loose body to be 2r / min, set the temperature of the first temperature zone 8, the second temperature zone 9, and the third temperature zone 10 to 1180°C, introduce chlorine and helium into the guide rod 1, the flow rate of chlorine is 0.8slpm, the flow rate of helium is 4slpm, and helium and chlorine are passed through the air inlet 6 at the bottom of the furnace core tube, the flow rate of helium is 10slpm, and the flow rate of chlorine is 1slpm, and dehydroxylation treatment is carried out for 60min to obtain the loose body after dehydration and purification treatment;

[0068] S3 controls the rotation speed of the loose body to 1r / min, the temperature of the first temperature zone 8 is set to 850°C, the temperature of the second temperature zone 9 is set to 850°C, and the temperature of the third temperature zone 10 is set to 1320°C. The flow rate of silicon tetrafluoride gas introduced into the central hole of the loose body through the guide rod 1 is 1.2slpm, the pressure of the mixed gas in the central hole of the loose body is controlled at 70a, and the flow rate of helium is adjusted to 1.5slpm; at the same time, the flow rate of silicon tetrafluoride gas introduced into the outer part of the loose body through the furnace core tube inlet 6 is 0.4slpm, and the flow rate of helium is 15slpm. The loose body descends at a speed of 5mm / min, and vitrification is completed during the contraction process to obtain a glass rod;

[0069] The glass rod is degassed at 1100° C. for 16 hours to obtain a fluorine-doped sleeve with different inner and outer refractive indices, and then a refractive index step-type sleeve is obtained.

[0070] The present invention also provides a refractive index step-type sleeve, which is prepared according to the preparation method of the refractive index step-type sleeve as described above.

[0071] Experimental methods

[0072] The refractive index step-type sleeve prepared in Example 1 was characterized and tested using a PK-2600 device, including the following steps:

[0073] 1. Equipment connection and setting: correctly connect the PK-2600 device to the computer or other data processing equipment to ensure smooth data transmission; open the device software and set the test parameters, including light source wavelength, measurement range, data sampling rate, etc.;

[0074] 2. Sample placement and adjustment, prepare the sample: place the refractive index step sleeve in the oil bath environment, ensure that the sample is completely immersed in the oil bath environment; use the PK-2600 device to adjust the light path so that it passes through the oil bath, the sample, and enters the oil bath again, with one end transmitting and the other end receiving, ensuring the alignment and stability of the light path.

[0075] 3. Refractive index measurement: start the light source of the equipment, let the light pass through the sample and refract; capture and record the direction and intensity information of the refracted light, and use the built-in data processing system of the equipment or the software on the computer to analyze the data; calculate the refractive index value of the sample according to the law of refraction and the measurement principle of the equipment; for step-type casing, it is necessary to measure and calculate the refractive index of each layer of material separately;

[0076] 4. Relative refractive index calculation. After obtaining the refractive index of each layer of material, the relative refractive index of the loose inner cladding 3 and the loose outer cladding 5 can be calculated; the relative refractive index is the ratio of the refractive index of the loose body to the refractive index of the loose body standard material; the characterization test data of the refractive index step-type casing prepared in Example 1 are as follows Table 1:

[0077] Table 1 Characterization test data of the refractive index step-type sleeve prepared in Example 1

[0078] project Relative refractive index of the cladding in the loose body (%) Relative refractive index of loose outer cladding (%) Example 1 -0.648％ -0.48％

[0079] From Table 1 and Figure 2 We can see that the refractive index profile of the refractive index step-type sleeve prepared in Example 1 achieves the step-type characteristics, and can be directly applied in the fields of special optical fiber, ultra-low loss optical fiber and bend-resistant optical fiber, reducing the difficulty of optical fiber manufacturing and ultimately reducing the manufacturing cost of optical fiber products; the refractive index step-type sleeve prepared in Example 1 can also be directly used as the sleeve material of the ultra-low loss G.654 series optical rod preform; the refractive index step-type sleeve can effectively reduce the loss of light during transmission through precise refractive index design and optimization, thereby improving the performance of the optical fiber transmission system; its excellent physical properties can ensure the stability and reliability of the preform during manufacturing and use, and reduce the optical fiber transmission failure rate caused by sleeve material problems; the refractive index step-type sleeve usually has good processing performance, and can be easily cut, bent and connected, thereby meeting various needs of the optical fiber transmission system; the refractive index step-type sleeve, due to its unique refractive index distribution and excellent physical properties, not only helps to improve the performance of the optical fiber transmission system, but also can reduce the manufacturing and use costs, providing strong support for the development of the optical fiber communication field.

[0080] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all various changes or equivalent substitutions falling within the scope of the claims of the present application are included. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present application are within the scope protected by the present invention.

Claims

1. A method for preparing a refractive index step-type sleeve, characterized in that: The following steps are involved: S1 uses the core-pulling tube external vapor deposition method to deposit silicon dioxide quartz powder on the surface of the guide rod, and sets different combustion gas flow rates during the deposition process to obtain loose bodies in the inner and outer regions and a densified glass layer that isolates the loose bodies in the inner and outer regions; S2 dehydrates and purifies the loose body to obtain a dehydrated and purified loose body; S3 introduces fluoride gas into the central hole and the outer part of the loose body after dehydration and purification, and performs fluorine doping at a set temperature by controlling the gas flow rate to obtain a fluorine-doped sleeve with different refractive indices inside and outside.

2. The method for preparing the refractive index step sleeve according to claim 1, characterized in that: The densified glass layer deposited between the loose bodies in the inner and outer regions for insulation in step S1 includes the following preparation steps: When the thickness of the cladding in the loose body reaches the target thickness during the deposition process, the silicon-based raw material in the blowtorch is shut down, and the flow rate of the combustion gas is increased to 120% to 150% of the flow rate of the combustion gas for depositing the loose body. The baking time is controlled at 0.5 to 2 minutes, and a densified glass layer is deposited; The silicon-based raw material is silicon tetrachloride or organosilicon, and the combustion gas is methane and / or hydrogen.

3. The method for preparing the refractive index step-type sleeve according to claim 1, characterized in that: The density of the densified glass layer deposited in step S1 is 1.8 to 2.2 g / cm 3 , with a thickness of 0.1 to 0.5 mm. The loose bodies in the inner and outer regions include: a loose inner cladding and a loose outer cladding. The density of the deposited loose inner cladding is 0.3 to 0.6 g / cm 3 The density of the deposited loose outer cladding is 0.3-0.6 g / cm 3 .

4. The method for preparing the refractive index step-type sleeve according to claim 1, characterized in that: The fluoride gas introduced in step S3 is a refractive index increasing doping compound gas or a refractive index decreasing doping compound gas, wherein the refractive index increasing doping compound gas includes: any one of germanium tetrachloride, phosphorus oxychloride and silicon tetrachloride, and the refractive index decreasing doping compound gas includes: any one of carbon tetrafluoride, silicon tetrafluoride, hexafluoroethane and hexafluoroethylene silicon.

5. The method for preparing the refractive index step-type sleeve according to claim 1, characterized in that: The setting temperature for fluorine doping in step S3 includes: The set temperature of the first temperature zone is 800℃~900℃; The second temperature zone is set at 800℃~900℃; The set temperature of the third temperature zone is 1300℃~1350℃.

6. The method for preparing the refractive index step-type sleeve according to claim 1, characterized in that: The flow rate of the fluorine-doped gas in step S3 is 0.1 to 18 slpm.

7. The method for preparing the refractive index step-type sleeve according to claim 5 or 6, characterized in that: Step S3 introduces fluoride gas into the central hole and the peripheral part of the loose body, controls the gas flow rate and performs fluorine doping at a certain temperature to obtain a fluorine-doped sleeve with different inner and outer refractive indices, which specifically includes the following steps: The rotation speed of the loose body is controlled, the temperatures of the first temperature zone, the second temperature zone and the third temperature zone are set, the flow rate of the fluoride gas introduced into the central hole of the loose body is 0.9-1.5 slpm, the pressure of the mixed gas in the central hole of the loose body is controlled at 60-80 pa, and the flow rate of the helium is adjusted to 1-2 slpm; at the same time, the flow rate of the fluoride gas introduced into the outer part of the loose body is 0.3-0.5 slpm, the flow rate of the helium is 14-16 slpm, the loose body descends at a speed of 4-6 mm / min, and the vitrification is completed during the contraction process to obtain a glass rod; The glass rod is degassed at 1050-1150° C. for 14-18 hours to obtain a fluorine-doped sleeve with different inner and outer refractive indices.

8. The method for preparing the refractive index step-type sleeve according to claim 1, characterized in that: The following steps are also included: S4 cuts off the head and tail cones of the fluorine-doped sleeve with different inner and outer refractive indices, and then performs boring processing to obtain a refractive index step-type sleeve.

9. A refractive index step-type sleeve, characterized in that: The refractive index step sleeve is prepared according to the preparation method of any one of claims 1-8.

10. A manufacturing device for a refractive index step-type sleeve, characterized in that: The method for manufacturing a refractive index step-type sleeve as described in any one of claims 1 to 8 comprises: a lead rod, wherein the lead rod is hollow, one end of the lead rod passes through one end of a furnace core tube and enters the interior of the furnace core tube, a loose inner cladding and a loose outer cladding as well as a densified glass layer between the loose inner cladding and the loose outer cladding are deposited on the lead rod portion inside the furnace core tube, a furnace core tube air inlet is provided at the other end of the furnace core tube, and the lead rod is sealed and connected to the loose body through a connecting sleeve.

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