CN112876060B

CN112876060B - Preparation method of large-size optical fiber preform core rod

Info

Publication number: CN112876060B
Application number: CN202110145567.8A
Authority: CN
Inventors: 李星; 喻煌; 郭浩; 岳静
Original assignee: Fiberhome Fujikura Optic Technology Co ltd; Fiberhome Telecommunication Technologies Co Ltd
Current assignee: Fiberhome Fujikura Optic Technology Co ltd; Fiberhome Telecommunication Technologies Co Ltd
Priority date: 2021-02-02
Filing date: 2021-02-02
Publication date: 2022-09-02
Anticipated expiration: 2041-02-02
Also published as: CN112876060A

Abstract

The application relates to a preparation method of a large-size optical fiber preform core rod, which comprises the following steps: providing a reaction tube, wherein the reaction tube comprises a plurality of base tubes sleeved from inside to outside; the inner space of the innermost base tube and the space between any two adjacent base tubes form a deposition cavity respectively; introducing corresponding reaction gas into each deposition cavity by adopting a PCVD (plasma chemical vapor deposition) process, and finishing the deposition process; and performing a melting and shrinking process to obtain the large-size optical fiber preform core rod. This application adopts the reaction tube that a plurality of parent tube cover were established and are formed, except that the inner wall of the most inboard parent tube is as the deposition face, every increase a parent tube, just can make the surface that lies in the inboard parent tube in two adjacent parent tubes as the deposition face to make every increase a parent tube, just can more two deposition faces, when carrying out the deposit like this, can improve deposition efficiency in the unit interval widely.

Description

Preparation method of large-size optical fiber preform core rod

Technical Field

The application relates to the technical field of manufacturing of optical fiber preforms, in particular to a method for preparing a large-size optical fiber preform core rod.

Background

The optical fiber is prepared by drawing an optical fiber preform under the condition of high-temperature melting by a drawing machine and coating a high polymer material. The optical fiber preform is the basis for manufacturing optical fibers, mainly comprises a core layer and a cladding layer, and the classical preparation method comprises a one-step method and a two-step method. Preparing a prefabricated rod by adopting a one-step method, wherein a core layer and a cladding layer of the prefabricated rod are both completed by a vapor deposition process; the two-step method is different from the one-step method in that the preform rod with large size can be prepared, thereby reducing the cost and improving the production efficiency.

The Plasma Chemical Vapor Deposition (PCVD) method can accurately control the refractive index profile of the prefabricated rod to manufacture the optical fiber with a complex structure, thereby being widely applied to the preparation of special and high-end multimode optical fibers with complex refractive index profiles.

The plasma chemical vapor deposition method is a technique of activating reaction gas by plasma to promote the reaction gas to carry out chemical reaction in the surface space of a reaction substrate tube to generate a solid film.

The PCVD process usually requires two steps of deposition and collapsing to complete the processing of the preform rod. Wherein, the deposition process is to form low-pressure plasma by means of microwave, so that gaseous halide and oxygen are directly deposited in a reaction substrate tube under the high-temperature condition of more than 1000 ℃; the melt-shrinkage process is to heat the small segment of rotating reaction substrate tube to about 2200 deg.c with the heating furnace moving axially back and forth along the substrate tube, and to melt the deposited reaction substrate tube into one solid rod in stages under the action of surface tension to obtain the prefabricated rod core rod.

The PCVD process is an in-tube vapor deposition method, the size of the prepared preform rod is directly related to the outer diameter of the used reaction base tube, and the larger the outer diameter of the reaction base tube is, the larger the upper limit of the diameter of the preform rod after deposition is determined to be; the volume efficiency depends on the microwave power to a certain extent, the larger the microwave power is, the thicker the glass layer deposited in unit time is, and the thicker the preform core rod formed after final melting and shrinking is. Therefore, when a PCVD process is used to prepare a large-sized optical fiber core rod, a large-sized reaction tube and a high-power microwave are natural choices, but when the process is adopted to prepare the optical fiber core rod, the defects still exist:

(1) if the outer diameter of the reaction tube is simply increased to prepare a large-size optical fiber preform core rod, the deposition time is long and the deposition efficiency is low.

(2) If the microwave power is increased, a large amount of heat is generated, the risk of deposition failure is increased sharply, and the yield is reduced seriously.

(3) If the size of the reaction tube is simply increased, the melting shrinkage is difficult in the melting shrinkage process, and if the melting shrinkage time is increased and the temperature of the heating furnace is increased, a large amount of Ge in the core region of the Ge-doped prefabricated rod is volatilized, the refractive index profile of the core region is damaged, and the quality defect of the optical fiber is caused.

(4) In the process of the large-size preform core rod melting shrinkage, the heating time is long, the heat source moves slowly, and the part far away from the heat source is too cold, so that the preform core rod is fractured during the melting shrinkage.

Disclosure of Invention

The embodiment of the application provides a preparation method of a large-size optical fiber preform core rod, which aims to solve the problems of long deposition time and low deposition efficiency in the preparation of the large-size optical fiber preform core rod in the related technology.

The embodiment of the application provides a preparation method of a large-size optical fiber preform core rod, which comprises the following steps:

providing a reaction tube, wherein the reaction tube comprises a plurality of base tubes sleeved from inside to outside; the inner space of the innermost base tube and the space between any two adjacent base tubes form a deposition cavity respectively;

introducing corresponding reaction gas into each deposition cavity by adopting a PCVD (plasma chemical vapor deposition) process, and finishing a deposition process;

and performing a melting and shrinking process to obtain the large-size optical fiber preform core rod.

In some embodiments, before performing the deposition process, the method further comprises the steps of:

providing a heat preservation system, wherein the heat preservation system comprises a heat preservation furnace, a heating rod, a first temperature sensor, a second temperature sensor, a first cooling device and a first control device, the heating rod is arranged in the heat preservation furnace, and the first temperature sensor is arranged in the heat preservation furnace and used for measuring the temperature in the heat preservation furnace; the second temperature sensor is connected with the microwave resonant cavity and used for measuring the temperature in the microwave resonant cavity; the first cooling device is connected with the microwave resonant cavity;

passing the reaction tube through the microwave resonant cavity;

in performing the deposition process, the preparation method further includes the steps of:

the first control device regulates and controls the heating power of the heating rod based on the relation between the temperature measured by the first temperature sensor and the first target temperature, and regulates and controls the first cooling device to execute corresponding actions based on the relation between the temperature measured by the second temperature sensor and the second target temperature and the warning temperature.

In some embodiments, the holding furnace is provided with a second cooling device, and the first control device is further configured to control the second cooling device to perform corresponding actions based on the relationship between the temperature measured by the first temperature sensor and the first target temperature.

In some embodiments, the holding furnace is provided with a plurality of heating zones, and the heating zones are distributed along the length direction of the holding furnace;

the heating rod and the first temperature sensor are both multiple, and each heating zone is provided with one heating rod and one first temperature sensor;

the first control device is further used for obtaining the temperature measured by each first temperature sensor, comparing the temperature with a first target temperature, and controlling the heating power of the corresponding heating rod according to the comparison result.

In some embodiments, the reaction tube that completes the deposition process is heated using a dielectric heating furnace to perform collapsing.

In some embodiments, before the collapsing process is performed, the preparation method further includes the steps of:

providing a melting and shrinking system, wherein the melting and shrinking system comprises melting and shrinking equipment, negative pressure equipment and a second control device, the melting and shrinking equipment comprises a melting and shrinking bed, a fixed main shaft box and a movable main shaft box which can be close to or far away from the fixed main shaft box are arranged on the melting and shrinking bed, a dielectric heating furnace is movably arranged between the fixed main shaft box and the movable main shaft box, and the dielectric heating furnace is provided with a third temperature sensor for measuring the furnace temperature; the negative pressure equipment is communicated with the fixed spindle box, and the second control device is connected with a third temperature sensor and the negative pressure equipment;

respectively arranging two ends of the reaction tube which finishes the deposition process on the fixed spindle box and the movable spindle box, and penetrating through the dielectric heating furnace;

in the step of performing the collapsing process, the preparation method further includes the steps of:

and the second control device regulates and controls the heating power of the dielectric heating furnace and the negative pressure provided by the negative pressure equipment to the reaction tube according to the relation between the temperature measured by the third temperature sensor and a third target temperature.

In some embodiments, the collapsing device further comprises two baking lamps for heating and insulating two ends of the reaction tube respectively;

when the dielectric heating furnace moves towards one end of the reaction tube, driving the baking lamp corresponding to the end to retreat away from the reaction tube so as to avoid the dielectric heating furnace;

when the dielectric heating furnace leaves the end, the baking lamp is driven to reset.

In some embodiments, an avoidance area is formed between the fixed main spindle box and the smelting and shrinking bed and between the movable main spindle box and the smelting and shrinking bed respectively;

the baking lamp is arranged on a telescopic device, and the telescopic device is movably arranged on the smelting and shrinking bed through a carrying platform;

when the dielectric heating furnace moves towards one end of the reaction tube, the telescopic device drives the baking lamp to move towards the outer side of the smelting reduction bed so as to retreat from the reaction tube; and the carrying platform moves towards the avoidance area on the side where the carrying platform is located until the carrying platform and the telescopic device on the carrying platform are contained in the avoidance area.

In some embodiments, the carrying platform is provided with a lapping piece, the dielectric heating furnace is rotatably connected with two hooks, and the two hooks are respectively matched with the lapping piece on the carrying platform corresponding to the two baking lamps;

the carrying platform is also provided with a boss, and the bosses of the two carrying platforms are arranged on the smelting shrinkage bed;

the boss is configured to:

when the dielectric heating furnace moves towards one end of the reaction tube, the hook rotates under the support of the boss, and when the hook passes through the boss, the hook resets and is hung on a lapping piece on a corresponding carrier platform, and the carrier platform moves to be contained in the avoiding area under the drive of the dielectric heating furnace;

when the dielectric heating furnace leaves, the hook is supported by the boss to rotate so as to be separated from the lap joint piece, and the hook resets when passing through the boss.

In some embodiments, the telescopic device comprises:

a fixed plate provided on the stage;

the moving plate is movably arranged on the fixed plate, and the baking lamp is arranged on the moving plate;

and the driving mechanism is arranged on the fixed plate and connected with the movable plate, and is used for driving the movable plate to drive the baking lamp to move along the direction vertical to the moving direction of the dielectric heating furnace.

The beneficial effect that technical scheme that this application provided brought includes:

the embodiment of the application provides a preparation method of a large-size optical fiber preform core rod, a plurality of base pipes are sleeved to form a reaction pipe, the inner wall of the most inner base pipe is used as a deposition surface, and when one base pipe is added, the outer surface of the base pipe positioned on the inner side in two adjacent base pipes can be used as the deposition surface, so that when one base pipe is added, two deposition surfaces can be added, and thus, the deposition efficiency in unit time can be greatly improved. In addition, the substrate tube is directly selected as a part of the optical fiber preform core rod without deposition, thereby further improving the deposition efficiency.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a schematic view of a reaction tube provided in an example of the present application;

FIG. 2 is a schematic diagram of a heat preservation system provided in an embodiment of the present application (a first cooling system and a second cooling system are not shown);

FIG. 3 is a schematic view of a heat preservation system provided in an embodiment of the present application (a heating rod is not shown);

FIG. 4 is a front view of a collapsing system according to an embodiment of the present application;

FIG. 5 is a top view of a collapsing apparatus according to an embodiment of the present application;

FIG. 6 is a schematic view of a hook and strap combination provided in accordance with an embodiment of the present application;

fig. 7 is a schematic view of a telescopic device according to an embodiment of the present application.

In the figure: 1. a reaction tube; 10. a base pipe; 11. a deposition chamber; 2. a heat preservation system; 20. a holding furnace; 21. heating a rod; 22. a first temperature sensor; 23. a second temperature sensor; 24. a first cooling device; 25. a first control device; 26. a second cooling device; 3. a microwave resonant cavity; 4. a collapsing device; 40. a molten shrinkage bed; 41. fixing a main spindle box; 42. moving the main spindle box; 43. a dielectric heating furnace; 44. baking a lamp; 45. an avoidance zone; 46. a stage; 47. a lap joint; 48. hooking; 49. a boss; 5. negative pressure equipment; 50. a first conduit; 51. a tail gas exhaust pipeline; 52. a pressure regulating valve; 53. a dust filtering buffer box; 54. air supply regulating valve; 55. a jet pump; 6. a second control device; 7. a telescoping device; 70. a fixing plate; 71. moving the plate; 72. a drive mechanism; 73. a fire shield.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The embodiment of the application provides a preparation method of a large-size optical fiber preform core rod, which can solve the problems of long deposition time and low deposition efficiency in the preparation of the large-size optical fiber preform core rod in the related art. .

101: providing a reaction tube 1, wherein the reaction tube 1 comprises a plurality of base tubes 10, the diameters of the base tubes 10 are different, and the base tubes 10 are sleeved from inside to outside according to the diameters, as shown in fig. 1, two base tubes 10 are illustrated; the inner space of the innermost substrate tube 10, and the space between any two adjacent substrate tubes 10, each form a deposition chamber 11;

102: introducing corresponding reaction gas into each deposition cavity 11 by adopting a PCVD (plasma chemical vapor deposition) process, and finishing the deposition process;

103: and performing a melting and shrinking process to obtain the large-size optical fiber preform core rod.

According to the preparation method provided by the embodiment of the application, the reaction tube 1 formed by sleeving the base tubes 10 is adopted, except that the inner wall of the innermost base tube 10 is used as a deposition surface, the outer surface of the base tube 10 positioned on the inner side in the two adjacent base tubes 10 can be used as the deposition surface when one base tube 10 is added, so that two deposition surfaces can be added when one base tube 10 is added, and the deposition efficiency in unit time can be greatly improved when deposition is carried out. In addition, the substrate tube 10 itself, which is a part of the core rod of the optical fiber preform, is directly selected without deposition, thereby further improving the deposition efficiency.

It should be noted that the substrate tube 10 may be selected from a pure quartz tube or a doped quartz tube according to the actual deposition requirements.

When each parent tube 10 was established at the cover, can be coaxial cover and establish, also can non-coaxial cover establish, set up according to the deposit demand can, the both ends extension pipe that continues of each parent tube 10 to guarantee the relative position between the reaction tube through the frock.

According to the deposition requirement, the same or different reaction gases can be introduced into each deposition chamber 11, and each deposition chamber 11 is controlled by different vacuum control systems. The reaction tube 1 is arranged in a microwave resonant cavity and is insulated by the same heat insulation system for PCVD deposition process production.

In one possible embodiment, as shown in FIG. 1, the reactor tube 1 is a double-layer concentric arrangement, with the outer substrate tube 10 having an outer layer with an outer diameter typically ranging from 43 to 80mm and a thickness typically ranging from 2 to 6mm, as desired; the typical value of the outer diameter of the base pipe 10 of the inner layer is 30-55mm, the thickness is set according to the requirement of a refractive index profile, and the typical value is 2-6 mm; typical values for the length of the substrate tube 10 are in the range 1.4-1.9 m. The base tube 10 is made of pure quartz glass tube, F-doped quartz tube or other doped glass tubes. The silica glass tube is not limited to the composite tube.

The microwave power of the PCVD process is 6-20kw, and the heat preservation temperature is 800-1200 ℃ during deposition.

Each deposition chamber 11 in the reaction tube 1 is used for depositing refractive index profiles of different areas of the optical fiber preform core rod, so that different from other PCVD processes, a complete refractive index profile of the optical fiber preform core rod is finally formed by depositing from the cladding layer to the core region layer by layer.

After deposition, the whole optical rod is fused and contracted on a fusion-contraction bed to form a complete large-size optical fiber preform core rod, specifically, when the optical rod is fused and contracted, the outer-layer deposition cavity 11 is preferentially adopted and then the inner-layer deposition cavity 11 is gradually fused and contracted, so that the problem of bubbles can be effectively controlled, but the scheme that the deposition cavities 11 can be fused and contracted simultaneously or from inside to outside is not excluded in the application. The deposition cavity 11 of the target controls the melting and shrinking speed through negative pressure in the melting and shrinking process, and the deposition cavity 11 which is not temporarily melted and shrunk controls positive pressure to ensure that the shape of the optical rod is not deformed.

In some preferred embodiments, before performing the deposition process, the preparation method further comprises the steps of:

referring to fig. 2 and fig. 3, a set of holding system 2 is provided, where the holding system 2 includes a holding furnace 20, a heating rod 21, a first temperature sensor 22, a second temperature sensor 23, a first cooling device 24, and a first control device 25, the heating rod 21 is disposed in the holding furnace 20, and the first temperature sensor 22 is disposed in the holding furnace 20 and is used for measuring the temperature in the holding furnace 20; the second temperature sensor 23 is connected with the microwave resonant cavity 3 and is used for measuring the temperature in the microwave resonant cavity 3; the first cooling device 24 is connected with the microwave resonant cavity 3;

placing the reaction tube 1 in a heat preservation furnace 20 and penetrating through a microwave resonant cavity 3;

in performing the deposition process, the method further comprises the steps of: the first control means 25 regulates the heating power of the heating rod 21 based on the relationship between the temperature measured by the first temperature sensor 22 and the first target temperature, and regulates the first cooling means 24 to perform corresponding actions based on the relationship between the temperature measured by the second temperature sensor 23 and the second target temperature and the warning temperature.

In the present embodiment, the ambient temperature of the deposition process is stabilized by controlling the heating power of the heating rod 21, specifically, the first control device 25 obtains the temperature measured by the first temperature sensor 22 and compares the temperature with the first target temperature, if the temperature is higher than the first target temperature, the heating power of the heating rod 21 is reduced, otherwise, the heating power of the heating rod 21 is increased, so that the ambient temperature is in dynamic balance.

The microwave resonant cavity 3 is not only a reaction condition but also brings a large amount of heating, the heating is irregular and changes according to the amount of energy absorbed by reaction gas, when the reaction in the reaction tube 1 is insufficient and the reaction gas is less, a large amount of energy is changed into heat, and the whole reaction atmosphere is influenced.

Based on this, in this embodiment, the first cooling device 24 is controlled to make the temperature in the microwave cavity 3 approach the second target temperature, so as to reduce the temperature fluctuation, so as to make the deposition process proceed smoothly, specifically, the first control device 25 obtains the temperature measured by the second temperature sensor 23, and compares the temperature with the second target temperature and the warning temperature, if the measured temperature is higher than the warning temperature, it represents that there is a lot of heat generation, at this time, it is necessary to control the power of the first cooling device 24 to decrease the temperature rapidly, so as to make the temperature in the microwave cavity 3 approach the second target temperature, and if the measured temperature is lower than the warning temperature, the power of the first cooling device 24 is decreased or shut down, so as to finally ensure the dynamic balance of the deposition temperature.

Wherein the first target temperature, the second target set temperature, and the alert temperature are set in advance according to the deposition requirement.

In this embodiment, the first cooling device 24 adopts a heat exchanger, and the flow rate of the cooling water is adjusted to achieve the purpose of cooling.

In this embodiment, through the heat preservation system 2 that provides, can solve the high power microwave deposition problem of generating heat, improve the temperature field homogeneity to improve the deposition homogeneity, improve the effective stick length of deposit.

In some preferred embodiments, referring to fig. 3, the holding furnace 20 is provided with a second cooling device 26, and the first control device 25 is further configured to control the second cooling device 26 to perform corresponding actions based on the relationship between the temperature measured by the first temperature sensor 22 and the first target temperature.

The present embodiment provides the second cooling device 26, and the purpose thereof is to reduce the temperature more rapidly by the second cooling device 26 on the basis of reducing the ambient temperature by reducing the heating power of the heating rod 21.

It should be noted that the second cooling device 26 may also adopt a heat exchanger, and the cooling purpose is achieved by adjusting the flow rate of the cooling water.

In some preferred embodiments, referring to FIG. 2, holding furnace 20 has a plurality of heating zones, and each heating zone is distributed along the length of holding furnace 20; the heating rod 21 and the first temperature sensor 22 are both provided in plurality, and each heating zone is provided with one heating rod 21 and one first temperature sensor 22; the first control device 25 is further configured to obtain the temperature measured by each first temperature sensor 22, compare the temperature with the first target temperature, and control the heating power of the corresponding heating rod 21 according to the comparison result.

The embodiment controls the environment temperature more specifically by partition control.

In some preferred embodiments, referring to fig. 4, the reaction tube 1, which has completed the deposition process, is heated using a dielectric heating furnace 43 to perform collapsing.

The dielectric heating furnace 43 heats a heating object by a high-frequency electric field, and the heating object is repeatedly polarized by being placed in an alternating electric field and is frictionally heated by molecular motion. Compared with the mode of heating by the principle of heat conduction and heat radiation, such as oxyhydrogen flame, a resistance furnace, an induction furnace and the like, as the dielectric heating heat is generated inside a heating object, the heating speed is high, the heat efficiency is high, the collapsing capacity of the large-size optical fiber preform core rod can be realized, the collapsing time is reduced, the productivity is improved, meanwhile, the dielectric heating is uniform, the stress reduction of the large-size optical fiber preform core rod is facilitated, and the quality of the large-size optical fiber preform core rod is improved. The dielectric heating is suitable for local heating in a small range, but the point just accords with the using condition of the PCVD process, and the PCVD process also heats the melt-shrinkage process locally, little by little, but not integrally.

In some preferred embodiments, before the collapsing process is performed, the preparation method further comprises the following steps:

referring to fig. 4 and 5, a set of collapsing system is provided, the collapsing system comprises a collapsing device 4, a negative pressure device 5 and a second control device 6, the collapsing device 4 comprises a collapsing bed 40, a fixed main spindle box 41 and a movable main spindle box 42 are arranged on the collapsing bed 40, the movable main spindle box 42 can move on the collapsing bed 40 to be close to or far away from the fixed main spindle box 41, a dielectric heating furnace 43 is movably arranged between the fixed main spindle box 41 and the movable main spindle box 42, and the dielectric heating furnace 43 is provided with a third temperature sensor for measuring the furnace temperature; the negative pressure device 5 is communicated with the fixed spindle box 41, and the second control device 6 is connected with the third temperature sensor and the negative pressure device 5;

the two ends of the reaction tube 1 which finishes the deposition process are respectively arranged on the fixed spindle box 41 and the movable spindle box 42 and pass through the dielectric heating furnace 43, so that the dielectric heating furnace 43 can conveniently move back and forth to heat and melt the reaction tube 1;

in the step of performing the collapsing process, the preparation method further comprises the steps of:

the second control means 6 regulates the heating power of the dielectric heating furnace 43 and the negative pressure supplied from the negative pressure device 5 to the reaction tube 1 based on the relationship between the temperature measured by the third temperature sensor and the third target temperature.

In the present embodiment, the negative pressure control and the temperature control are controlled by the second control device 6, different temperatures are matched with different negative pressures, the relationship between the temperature and the negative pressure is stored in the second control device 6, the temperature control is realized by controlling the heating power of the dielectric heating furnace 43 to perform surface tension contraction, the negative pressure provided by the negative pressure device 5 is controlled to perform external pressure contraction, and the two acting forces are used to achieve the purpose of collapsing.

In the embodiment, on one hand, the dielectric heating furnace 43 is used for heating, so that the inside and the outside of the large-size optical fiber preform core rod are heated together, the fusion time can be shortened, the core area is not required to be rapidly heated by increasing the power, and the volatilization risk of the germanium dioxide in the core area is reduced; on the other hand, the second control device 6 regulates and controls the melting and shrinking equipment 4 and the negative pressure equipment 5, so that the melting and shrinking temperature is lower than the volatilization point of the germanium dioxide, and the volatilization of the germanium dioxide is avoided.

With reference to fig. 4, the negative pressure device 5 includes a first pipeline 50, a tail gas exhaust pipeline 51, a pressure regulating valve 52, and a dust filtering buffer tank 53, the tail gas exhaust pipeline 51 is communicated with the air draft device, two ends of the first pipeline 50 are respectively communicated with the tail gas exhaust pipeline 51 and the fixed spindle box 41, and the pressure regulating valve 52 and the dust filtering buffer tank 53 are sequentially arranged on the first pipeline 50 along the direction from the tail gas exhaust pipeline 51 to the fixed spindle box 41; a second pipeline and a third pipeline are connected to the first pipeline 50 and positioned between the pressure regulating valve 52 and the dust filtering buffer tank 53, a gas supplementing regulating valve 54 is arranged on the second pipeline, the second pipeline is communicated with nitrogen, a jet pump 55 is arranged on the third pipeline, and the third pipeline is communicated with a tail gas exhaust pipeline 51; the pressure regulating valve 52, the dust filtering buffer tank 53, the air supply regulating valve 54 and the jet pump 55 are all connected with the second control device 6.

The air draft device provides a negative pressure source of the whole system through a tail gas air draft pipeline 51 and takes away dust, the dust filtering buffer tank 53 filters the dust and stabilizes the pressure, and the second control device 6 controls the opening of the pressure regulating valve 52 to control the fusion negative pressure, so that the pressure rough regulation is realized.

The second control device 6 controls the jet pump 55 to work, on one hand, when the process requirement improves the rear-end negative pressure vacuum degree and the tail gas exhaust pipeline 51 is not enough to provide the negative pressure value, the jet pump 55 is controlled to work to quickly improve the vacuum degree; on the other hand, because the pressure of the tail gas exhaust pipeline 51 is not stable and constant, pressure fluctuation always occurs, only the pressure regulating valve 52 is used for rough regulation, frequent actions occur and the pressure is not controlled timely, and at the moment, the jet pump 55 is controlled to work, so that the quick action can be realized to compensate the pressure change.

The second control device 6 controls the air supply adjusting valve 54 to work, certain pressure fluctuation can still be caused by the changes of the working states such as the opening and the closing of the jet pump 55 and the pressure adjusting valve 52, at the moment, the change of the back-end draft is adjusted by controlling the work of the air supply adjusting valve 54 and adjusting the air supply amount, and the pressure fluctuation is improved by the mode of compensating the draft by air supply.

The jet pump 55 and the air supply regulating valve 54 are controlled to work, so that the pressure fine regulation is realized.

In some preferred embodiments, referring to fig. 4 and 5, the collapsing device 4 further comprises two baking lamps 44 for heating and insulating the two ends of the reaction tube 1;

when the dielectric heating furnace 43 moves towards one end of the reaction tube 1, driving the baking lamp 44 corresponding to the end to retreat from the reaction tube 1 so as to avoid the dielectric heating furnace 43;

when the dielectric heating furnace 43 leaves the end, the baking lamp 44 is driven to reset, and the heating and heat-holding are continued.

In the embodiment, the baking lamp 44 is adopted, so that the problem of rod cracking in the melting process can be effectively reduced.

Since the reaction tube 1 is generally long, for example, 1m long, in order to better prevent rod breakage, when the dielectric heating furnace 43 is returned and moved toward one end of the reaction tube 1, it is not necessary to immediately withdraw the baking lamp 44 corresponding to the end from the reaction tube 1, but when the dielectric heating furnace 43 is returned and moved to a position where the dielectric heating furnace 43 is close to the baking lamp 44 corresponding to the end, the baking lamp 44 corresponding to the end is withdrawn.

The retraction and repositioning of the searchlight 44 can be accomplished in a variety of ways, such as by a suspended telescoping arm. Of course, it can also be realized as follows:

referring to fig. 4 and 5, in some preferred embodiments, a relief area 45 is formed between the fixed headstock 41 and the collapsing bed 40, and between the moving headstock 42 and the collapsing bed 40;

the baking lamp 44 is arranged on a telescopic device 7, and the telescopic device 7 is movably arranged on the smelting and shrinking bed 40 through a carrying platform 46;

when the dielectric heating furnace 43 is moved toward one end of the reaction tube 1, the expansion device 7 drives the roast lamp 44 to move toward the outside of the molten reduction bed 40 (in fig. 5, the roast lamp 44 moves upward) to retreat from the reaction tube 1; and the stage 46 moves toward the avoidance area 45 on the side where it is located until the stage 46 and the expansion device 7 thereon are accommodated in the avoidance area 45.

When the dielectric heating furnace 43 leaves the end, the carrier 46 and the telescopic device 7 thereon leave the escape area 45 and are reset, and the telescopic device 7 drives the baking lamp 44 to reset.

In this embodiment, by providing the avoidance region 45 and the cooperation between the telescopic device 7 and the carrier 46, the blocking of the dielectric heating furnace 43 by the baking lamp 44 can be avoided, thereby avoiding the shortening of the core rod length of the optical fiber preform.

In some preferred embodiments, referring to fig. 5 and fig. 6, the carrying platform 46 is provided with a connecting component 47, for example, a pin, two hooks 48 are rotatably connected to the dielectric heating furnace 43, and the two hooks 48 are respectively matched with the connecting component 47 on the carrying platform 46 corresponding to the two baking lamps 44; the carrier 46 is also provided with a boss 49, the boss 49 adopts an arc shape or an arc shape, and the bosses 49 of the two carriers 46 are arranged on the smelting and shrinking bed 40;

the boss 49 is configured to:

when the dielectric heating furnace 43 moves towards one end of the reaction tube 1, the hook 48 rotates under the support of the boss 49, and when the hook 48 passes through the boss 49, the hook 48 resets and is hung on the corresponding lapping piece 47 on the carrier 46, and the carrier 46 moves to be contained in the avoiding area 45 under the drive of the dielectric heating furnace 43;

when the dielectric heating furnace 43 leaves the end, the hook 48 is rotated against the boss 49 to disengage the lap 47, and the hook 48 is reset when passing the boss 49.

Referring to fig. 5, the dielectric heating furnace 43 is moved rightward toward the moving headstock 42 for explanation:

the dielectric heating furnace 43 moves towards the moving headstock 42, when the hook 48 of the dielectric heating furnace 43 contacts the boss 49, the boss 49 abuts against the hook 48 to enable the hook to rotate, the dielectric heating furnace 43 continues to move and passes through the boss 49, at the moment, because the abutting force of the boss 49 on the hook 48 disappears, the hook 48 resets and is just hung on the lapping member 47 on the carrying platform 46, at the moment, the baking lamp 44 continues to move towards the moving headstock 42 along with the dielectric heating furnace 43;

when the baking lamp 44 is away from the moving spindle box 42 by a certain distance, the telescopic device 7 receives a signal sent by the sensor, at this time, the telescopic device 7 drives the baking lamp 44 to retreat, the telescopic device 7 and the carrier 46 enter the avoidance area 45 under the pushing of the dielectric heating furnace 43, and the moving space of the dielectric heating furnace 43 is ensured;

when the dielectric heating furnace 43 is far away from the moving spindle box 42, the dielectric heating furnace 43 drives the telescopic device 7 and the carrying platform 46 to leave the avoidance area 45 and move continuously, and when the telescopic device 7 receives the signal of the displacement sensor again, the telescopic device 7 drives the baking lamp 44 to reset;

when the hook 48 of the dielectric heating furnace 43 again hits the boss 49 after the movement is continued, the hook 48 rotates and disengages from the bridge 47, at which time the stage 46 disengages from the dielectric heating furnace 43, stops at the operating position, and the dielectric heating furnace 43 continues to move away from the moving headstock 42.

In some preferred embodiments, referring to fig. 7, the telescopic device 7 includes a fixed plate 70, a movable plate 71 and a driving mechanism 72, the fixed plate 70 is disposed on the carrier 46, the movable plate 71 is movably disposed on the fixed plate 70, and the baking lamp 44 is disposed thereon; the driving mechanism 72 is disposed on the fixed plate 70 and connected to the moving plate 71, and the driving mechanism 72 receives the signal from the displacement sensor and drives the moving plate 71 to move the baking lamp 44 in a direction perpendicular to the moving direction of the dielectric heating furnace 43.

Referring to fig. 7, the telescopic device 7 further includes a fire damper plate 73, and the fire damper plate 73 is connected to the fixed plate 70 and the moving plate 71.

In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

It is noted that, in the present application, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The previous description is only an example of the present application, and is provided to enable any person skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The preparation method of the large-size optical fiber preform core rod is characterized by comprising the following steps of:

providing a reaction tube (1), wherein the reaction tube (1) comprises a plurality of base tubes (10) which are sleeved from inside to outside; the inner space of the innermost substrate tube (10) and the space between any two adjacent substrate tubes (10) each form a deposition chamber (11);

introducing corresponding reaction gas into each deposition cavity (11) by adopting a PCVD (plasma chemical vapor deposition) process, and finishing the deposition process;

performing a melting and shrinking process to obtain a large-size optical fiber preform core rod;

before the deposition process is performed, the preparation method further comprises the following steps:

providing a heat preservation system (2), wherein the heat preservation system (2) comprises a heat preservation furnace (20), a heating rod (21), a first temperature sensor (22), a second temperature sensor (23), a first cooling device (24) and a first control device (25), the heating rod (21) is arranged in the heat preservation furnace (20), and the first temperature sensor (22) is arranged in the heat preservation furnace (20) and used for measuring the temperature in the heat preservation furnace (20); the second temperature sensor (23) is connected with the microwave resonant cavity (3) and is used for measuring the temperature in the microwave resonant cavity (3); the first cooling device (24) is connected with the microwave resonant cavity (3);

passing the reaction tube (1) through the microwave resonant cavity (3);

the first control device (25) regulates the heating power of the heating rod (21) based on the relation between the temperature measured by the first temperature sensor (22) and a first target temperature, and regulates the first cooling device (24) to perform corresponding actions based on the relation between the temperature measured by the second temperature sensor (23) and a second target temperature and an alert temperature.

2. The method for preparing a large-sized optical fiber preform core rod according to claim 1, wherein: the holding furnace (20) is provided with a second cooling device (26), and the first control device (25) is also used for controlling the second cooling device (26) to execute corresponding actions based on the relation between the temperature measured by the first temperature sensor (22) and the first target temperature.

3. The method for preparing a large-sized optical fiber preform core rod according to claim 1, wherein:

the holding furnace (20) is provided with a plurality of heating zones, and the heating zones are distributed along the length direction of the holding furnace (20);

a plurality of heating rods (21) and a plurality of first temperature sensors (22) are arranged, and each heating zone is provided with one heating rod (21) and one first temperature sensor (22);

the first control device (25) is further configured to obtain the temperature measured by each first temperature sensor (22), compare the temperature with a first target temperature, and control the heating power of the corresponding heating rod (21) according to a comparison result.

4. The method for preparing a large-sized optical fiber preform core rod according to claim 1, wherein: and heating the reaction tube (1) which completes the deposition process by using a dielectric heating furnace (43) to perform collapsing.

5. The method for preparing a large-sized optical fiber preform core rod according to claim 4, wherein:

before the fusing process is carried out, the preparation method further comprises the following steps:

providing a melting and shrinking system, wherein the melting and shrinking system comprises a melting and shrinking device (4), a negative pressure device (5) and a second control device (6), the melting and shrinking device (4) comprises a melting and shrinking bed (40), a fixed main spindle box (41) and a movable main spindle box (42) which can be close to or far away from the fixed main spindle box (41) are arranged on the melting and shrinking bed (40), a dielectric heating furnace (43) is movably arranged between the fixed main spindle box (41) and the movable main spindle box (42), and the dielectric heating furnace (43) is provided with a third temperature sensor for measuring the furnace temperature; the negative pressure equipment (5) is communicated with the fixed spindle box (41), and the second control device (6) is connected with a third temperature sensor and the negative pressure equipment (5);

respectively arranging two ends of the reaction tube (1) which finishes the deposition process on the fixed spindle box (41) and the movable spindle box (42) and penetrating through the dielectric heating furnace (43);

the second control device (6) regulates and controls the heating power of the dielectric heating furnace (43) and the negative pressure provided by the negative pressure equipment (5) to the reaction tube (1) according to the relation between the temperature measured by the third temperature sensor and a third target temperature.

6. The method for preparing a large-sized optical fiber preform core rod according to claim 5, wherein:

the melting and shrinking equipment (4) also comprises two baking lamps (44) which are respectively used for heating and insulating two ends of the reaction tube (1);

when the dielectric heating furnace (43) moves towards one end of the reaction tube (1), driving the baking lamp (44) corresponding to the end to retreat from the reaction tube (1) so as to avoid the dielectric heating furnace (43);

when the dielectric heating furnace (43) leaves the end, the baking lamp (44) is driven to reset.

7. The method for preparing a large-sized optical fiber preform core rod according to claim 6, wherein:

an avoidance area (45) is respectively formed between the fixed main shaft box (41) and the smelting and shrinking bed (40) and between the movable main shaft box (42) and the smelting and shrinking bed (40);

the baking lamp (44) is arranged on a telescopic device (7), and the telescopic device (7) is movably arranged on the smelting and shrinking bed (40) through a carrying platform (46);

when the dielectric heating furnace (43) moves towards one end of the reaction tube (1), the telescopic device (7) drives the baking lamp (44) to move towards the outer side of the molten shrinkage bed (40) so as to retreat from the reaction tube (1); and the carrying platform (46) moves towards the avoidance area (45) on the side where the carrying platform is located until the carrying platform (46) and the telescopic device (7) on the carrying platform are contained in the avoidance area (45).

8. The method for preparing a large-sized optical fiber preform core rod according to claim 7, wherein:

the carrying platform (46) is provided with a lapping piece (47), the dielectric heating furnace (43) is rotatably connected with two hooks (48), and the two hooks (48) are respectively matched with the lapping piece (47) on the carrying platform (46) corresponding to the two baking lamps (44);

the carrying platform (46) is also provided with a boss (49), and the bosses (49) of the two carrying platforms (46) are arranged on the smelting and shrinking bed (40);

the boss (49) is configured to:

when the dielectric heating furnace (43) moves towards one end of the reaction tube (1), the hook (48) is supported by the boss (49) to rotate, and when the hook (48) passes through the boss (49), the hook (48) is reset and is hung on a corresponding bridging piece (47) on the carrier (46), and the carrier (46) moves to be accommodated in the avoiding area (45) under the driving of the dielectric heating furnace (43);

when the dielectric heating furnace (43) is removed, the hook (48) is rotated against the boss (49) to disengage the overlapping member (47), and the hook (48) is restored when passing through the boss (49).

9. The method for preparing a large-sized optical fiber preform core rod according to claim 7, wherein the telescoping device (7) comprises:

a fixing plate (70) provided to the stage (46);

a moving plate (71) movably provided on the fixed plate (70) and on which the roast lamp (44) is disposed;

and the driving mechanism (72) is arranged on the fixed plate (70) and connected with the moving plate (71), and the driving mechanism (72) is used for driving the moving plate (71) to drive the baking lamp (44) to move along the direction vertical to the moving direction of the dielectric heating furnace (43).