CN113461321B

CN113461321B - Titanium dioxide doped quartz optical fiber, preparation method and application thereof, and evaporation device thereof

Info

Publication number: CN113461321B
Application number: CN202110847653.3A
Authority: CN
Inventors: 杨亮亮; 贾金升; 孙勇; 余刚; 孟政; 孔壮; 张志芳; 刘波; 王一苇
Original assignee: China Building Materials Academy CBMA
Current assignee: China Building Materials Academy CBMA
Priority date: 2021-07-27
Filing date: 2021-07-27
Publication date: 2023-03-24
Anticipated expiration: 2041-07-27
Also published as: CN113461321A

Abstract

The invention relates to a titanium dioxide-doped silica fiber, a preparation method, application and an evaporation device thereof, wherein the titanium dioxide-doped silica fiber sequentially comprises a fiber core, a fiber core cladding, a titanium diffusion layer and an organic cladding from inside to outside; the fiber core cladding is a quartz cladding; the titanium diffusion layer is a titanium dioxide doped quartz cladding; the first cladding layer and the second cladding layer are geometrically concentric with the fiber core. The invention directly mixes the dissolved low-expansion doped TiO ₂ Quartz glass is as the target, adopts electron beam evaporation's mode to carry out the coating film to optical fiber perform, and the rete layer associativity is good, and thickness is even controllable, utilizes this kind of coating mode easily mass production, and the flexibility is good, and is efficient, and the cost of manufacture is lower relatively.

Description

Titanium dioxide doped quartz optical fiber, preparation method and application thereof, and evaporation device thereof

Technical Field

The invention relates to the technical field of optical fiber reinforcement, in particular to a titanium dioxide-doped quartz optical fiber, a preparation method, application and an evaporation device thereof.

Background

Tensile strength is an important index for evaluating the performance of optical fibers. The main component of the silica optical fiber is silica glass, and the theoretical strength of the silica glass is composed of (SiO) ₂ ) Bond strength between molecules is determined when SiO ₂ When the bond is broken, the breaking strength is as high as 20GPa. When the external force exceeds this value, the optical fiber is broken.

In order to increase the tensile strength of the silica optical fiber, the silica optical fiber is usually reinforced by an organic coating, which can increase the tensile strength of the silica optical fiber, but the organic coating has a mechanical strength only in MPa level, so the organic coating mainly serves to protect the optical fiber from mechanical damage. In addition, the surface of the silica optical fiber is subjected to a drawing process before being coated with an organic coating, and microcracks are generated on the surface during cooling after molding, and the microcracks reduce the tensile strength of the optical fiber. Furthermore, during use, air, water vapor, etc. can cause the continuous micro-crack to spread, which may cause the strength of the quartz optical fiber to decrease rapidly to only one tenth or even lower of the theoretical tensile strength. Meanwhile, after the quartz optical fiber has microcracks, breakpoints are usually formed in the optical fiber, although the surface of the optical fiber is not broken, the transmission of light is actually influenced, and when the light meets the breakpoints, reflection is generated, so that the transmission is influenced.

Therefore, before the silica optical fiber is coated with the organic coating, it is necessary to increase the tensile strength of the silica optical fiber by breaking the generation and propagation of cracks by developing an outer cladding layer on the surface of the bare fiber, which has better flexibility than silica glass.

Disclosure of Invention

In view of the above, the main objective of the present invention is to provide a titania-doped silica fiber, a method for preparing the same, an application thereof, and a deposition apparatus thereof, which solve the technical problem of how to enhance the tensile strength of the silica fiber by doping titanium on the surface of a silica fiber preform by a high-energy plasma implantation method on the premise of uniform thickness of the filament diameter.

The purpose of the invention and the technical problem to be solved are realized by adopting the following technical scheme. According to the titanium dioxide-doped silica fiber provided by the invention, the titanium dioxide-doped silica fiber sequentially comprises a fiber core, a first cladding, a second cladding and an organic cladding from inside to outside;

the first cladding is a quartz cladding;

the second cladding is a titanium dioxide-doped quartz cladding;

the first cladding layer and the second cladding layer are geometrically concentric with the fiber core.

The object of the present invention and the technical problem to be solved can be further achieved by the following technical solutions.

Furthermore, in the titania-doped silica optical fiber, the thickness ratio of the first cladding, the second cladding and the organic cladding is (52.5-58.4): 0.0025-0.25): 62.5.

Further, in the titania-doped silica optical fiber, the mass ratio of silica to titania in the second cladding is (90-98): 2-10.

The purpose of the invention and the technical problem to be solved can be realized by adopting the following technical scheme. The invention provides a preparation method of a titanium dioxide doped silica optical fiber, which comprises the following steps:

s1, melting titanium dioxide powder and silicon dioxide powder at 1800-2100 ℃ and preserving heat to obtain first glass liquid;

s2, clarifying the first glass liquid obtained in the step S1 at 2000-2100 ℃ to obtain a second glass liquid;

s3, performing water quenching and crushing on the second glass liquid obtained in the step S2 to obtain a glass particle target material;

s4, placing the glass particle target material and the quartz optical fiber preform obtained in the step S3 in a vapor deposition vacuum value, and baking; then, under the oxygen-containing vacuum condition, the quartz optical fiber perform rod carries out vapor deposition under a set electron beam while rotating and coaxially reciprocating to obtain a titanium dioxide-doped quartz optical fiber perform rod;

s5, carrying out wire drawing treatment on the optical fiber preform obtained in the step S4 to obtain a quartz glass fiber with a titanium-doped quartz cladding;

s6, coating an organic cladding on the quartz glass fiber wire obtained in the step S5.

Further, in the above method for preparing a silica fiber doped with titanium dioxide, in step S1, the mass ratio of the titanium dioxide powder to the silica powder is (90-98) to (2-10).

Further, in the preparation method of the titanium dioxide doped silica optical fiber, in the step S1, the heat preservation time is 1 to 3 hours.

Further, in the above method for preparing a silica optical fiber doped with titanium dioxide, in step S2, the clarifying time is 30 to 60min.

Further, in the above method for preparing a silica fiber doped with titanium dioxide, in step S3, the particle size of the water quenched and crushed fiber is 0.1-2 mm.

Further, in the above method for preparing a silica optical fiber doped with titanium dioxide, in step S4, the baking temperature is 300 to 500 ℃.

Further, in the foregoing method for manufacturing a silica-doped silica optical fiber, in step S4, the oxygen-containing vacuum condition includes: vacuum degree of less than 5.9X 10 ^-3 Pa, the introduction rate of the oxygen is 10-15 sccm.

Further, in the above method for preparing a silica fiber doped with titania, wherein in step S4, the diameter of the silica fiber preform is 10 to 50mm.

Further, in the above method for manufacturing a silica-doped optical fiber, in step S4, the set value of the electron beam is 100 to 150mA.

Furthermore, in the preparation method of the titania-doped silica optical fiber, the autorotation speed of the optical fiber perform is 20-100 r/min, the speed of the coaxial reciprocating motion is 90-500 mm/s, and the amplitude is consistent with the rod length of the perform.

Further, in the above method for preparing a silica-doped silica optical fiber, in step S4, the silica optical fiber preform is rotated and coaxially moved under the vacuum condition containing oxygenThe evaporation under the set electron beam while reciprocating specifically includes: when the vacuum degree is lower than 1.6 multiplied by 10 ^-3 When Pa, oxygen is introduced at a rate of 10-15 sccm until the vacuum degree is stabilized at less than 5.9 × 10 ^-3 When Pa, opening electron beam and adjusting the position of the electron beam to make the electron beam face the target material, then increasing the electron beam at a speed lower than 25mA/min until the electron beam is stabilized at 100-150 mA, so that the optical fiber preform is evaporated under the conditions that the autorotation speed is 20-100 r/min, the coaxial reciprocating speed is 90-500 mm/s, and the amplitude is consistent with the rod length of the preform.

Further, in the preparation method of the titania-doped silica optical fiber, the crucible is made of copper, high temperature resistant stainless steel, molybdenum or tungsten.

The purpose of the invention and the technical problem to be solved can be realized by adopting the following technical scheme. According to the invention, the communication optical fiber is the titanium dioxide doped silica optical fiber.

The purpose of the invention and the technical problem to be solved can be realized by adopting the following technical scheme. The evaporation device for the quartz optical fiber perform rod comprises a vacuum chamber, wherein a base is arranged in the vacuum chamber, a crucible for containing a target material, two bearing supports, a film thickness detector and a roaster are respectively fixed on the base, a baffle is arranged above the crucible and connected with the base, and a gear transmission mechanism is arranged above the bearing supports; the bearing support is movably connected with a metal fixing piece for fixing the quartz optical fiber preform;

the gear transmission mechanism comprises a first disc gear, a second disc gear, two bevel gears and a displacement cycle expansion piece which are connected with each other.

Further, in the evaporation device for the quartz optical fiber preform, the metal fixing member is connected with one end of the displacement cyclic expansion unit, the other end of the displacement cyclic expansion unit is connected with one of the bevel gears, the two bevel gears are meshed with each other, the other bevel gear is meshed with the second disc gear, the second disc gear is meshed with the first disc gear, and the first disc gear is connected with the motor through a shaft.

Further, in the evaporation device for the silica optical fiber preform, a vacuum pump is connected to the lower portion of the base through a pipeline.

Further, in the evaporation device for the quartz optical fiber preform, an oxygen hole is formed in the top of the vacuum chamber, and the oxygen hole is connected with a high-pressure oxygen tank through a pipeline.

Compared with the prior art, the invention has the following beneficial effects:

1) Low expansion coefficient doped TiO ₂ The preparation process of the quartz glass coating is simple

Directly mix the dissolved low-expansion doped TiO ₂ Quartz glass is used as a target material, an electron beam evaporation method is adopted to carry out film coating on the optical fiber preform, the film layer binding property is good, the thickness is uniform and controllable, mass production is easy to realize by using the coating method, the flexibility is good, the efficiency is high, and the manufacturing cost is relatively low;

2) The tensile property of the quartz optical fiber is obviously improved

Because the electron beam evaporation coating is carried out on the optical fiber perform in advance and then the optical fiber perform is subjected to subsequent wire drawing, the film layer has good bonding performance on the surface of the quartz optical fiber, and simultaneously, because the TiO-doped film is doped ₂ The expansibility of the quartz glass is lower than that of the quartz glass, a layer of protective compressive stress is formed on the surface of the quartz optical fiber, the generation and the expansion of micro cracks on the surface of the bare quartz optical fiber are effectively avoided, and the tensile strength of the quartz optical fiber is obviously improved.

The foregoing is a summary of the present invention, and in order to provide a clear understanding of the technical means of the present invention and to be implemented in accordance with the present specification, the following is a detailed description of the preferred embodiments of the present invention.

Drawings

FIG. 1 is a schematic structural view of a titania-doped silica optical fiber according to the present invention;

FIG. 2 is a schematic structural diagram of an evaporation apparatus according to the present invention;

FIG. 3 is a plot of the EDS element area scan for the E-beam evaporated ultra-low expansion quartz glass film of example 1 of the present invention.

Detailed Description

To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description will be made with reference to the accompanying drawings and preferred embodiments of a titania-doped silica optical fiber, its preparation method, its application, and its evaporation apparatus, and its specific embodiments, features and effects. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features or characteristics of one or more embodiments may be combined in any suitable manner.

The following materials or reagents, unless otherwise specified, are all commercially available.

As shown in fig. 1, the invention provides a titania-doped silica optical fiber, which sequentially comprises a fiber core 1, a first cladding 2, a second cladding 3 and an organic cladding 4 from inside to outside; the first cladding 2 is a quartz cladding; the second cladding 3 is a titanium dioxide-doped quartz cladding; the first cladding 2 and the second cladding 3 are geometrically concentric with the fiber core 1.

In the specific implementation, the thickness ratio of the first cladding layer 2, the second cladding layer 3 and the organic cladding layer 4 is (52.5-58.4): (0.0025-0.25): 62.5. For example, the thickness of the first clad layer 2 may be 52.5 to 58.4 μm; the thickness of the second cladding layer 3 can be 0.0025 to 0.25 μm; the organic cladding layer 4 may have a thickness of 62.5 μm. Preferably, the thickness of the first cladding layer 2 is 54.5 to 55.5 μm; the thickness of the second cladding layer 3 is 5 μm, and the thickness of the organic cladding layer 4 may be 62.5 μm; this is preferred to maximize the reinforcement effect of the silica fiber. The organic clad layer 4 is preferably thicker only in view of mechanical strength, and is usually selected to be 62.5 μm because the coating is too thick in view of the transmission characteristics of the optical fiber, which causes not only microbending in bending, stretching and temperature change but also increase in loss of the optical fiber.

The diameter of the titania-doped silica fiber before being coated with the organic cladding is strictly controlled to 125 μm (i.e., the outer diameter of the second cladding is 125 μm), which is obtained by on-line monitoring with a wire diameter thickness gauge of a drawing machine. Wherein the diameter of the fiber core of the titanium dioxide-doped silica optical fiber is 9 +/-1 mu m and is fixed; the ratio of the diameter of the titania-doped silica optical fiber preform to the thickness of the titania-doped silica cladding layer is equal to the ratio of the filament diameter of the titania-doped silica optical fiber before being coated with the organic cladding layer 4 to the thickness of the second cladding layer 3, whereby the thickness of the second cladding layer 3, and the thickness of the first cladding layer 2 can be calculated. The thickness of the organic clad layer 4 is controlled by the outlet of the existing organic coating cup die so that the filament diameter is 250 μm after the organic clad layer (paste) is coated, and thus the thickness of the organic clad layer 4 can be obtained.

The "first cladding layer" and "second cladding layer" are artificially divided by the thickness measurement for convenience of description, and there is no distinct interface between layers; the "second cladding" and the "organic cladding" are two different materials, and have a distinct interface therebetween, but can be tightly bonded to the "organic cladding" due to its good toughness.

The mass ratio of the silicon dioxide to the titanium dioxide in the second cladding is (90-98) to (2-10); in the above mass ratio range, the doped TiO of the film ₂ The expansibility coefficient of the quartz glass is lower than that of the quartz glass, a layer of protective compressive stress is formed on the surface of the quartz optical fiber, the generation and the expansion of microcracks on the surface of a bare quartz optical fiber are effectively avoided, the tensile strength of the quartz optical fiber is obviously improved, and in order to better improve the tensile strength, the mass ratio is preferably 95; if the mass ratio is more than (90-98) to (2-10), the expansion coefficient of the film layer is close to the quartz glass, so that good compressive stress is difficult to form on the surface of the quartz optical fiber, and the enhancement effect is not obvious; if the mass ratio is less than (90-98) to (2-10), the combination effect of the film layer is poor, and the enhancement effect is not obvious.

In the titania-doped silica optical fiber prepared by the preparation method of the present invention, the second cladding layer has the following functions: the size and the number of the micro cracks possibly appearing on the surface layer are reduced, and the reinforcing effect of the optical fiber is realized. When the microcracks propagate to the vicinity of the second clad layer (titanium diffusion layer), since the metallic titanium does not have the brittleness of quartz glass, the propagation of the microcracks is suppressed, and the tensile strength of the optical fiber is enhanced.

Specifically, the organic cladding is provided to maintain the strength of the optical fiber, prevent the surface of the optical fiber from being damaged, and serve to buffer external stress during the use of the optical fiber. For example, the organic cladding layer may be made of acrylic resin and has a thickness of 62.5 μm.

The invention is not limited to the cross-sectional shape of the optical fiber, and the cross-sectional shape of the titania-doped silica optical fiber can be selected as desired. Preferably, the cross-sectional shape of the titania-doped silica optical fiber is circular, square, triangular or hexagonal, and more preferably, the cross-sectional shape of the titania-doped silica optical fiber is circular, because the reinforcing effect of the circular shape is greater than that of the other shapes.

The invention also provides a preparation method of the quartz optical fiber, which comprises the following steps:

s1, melting titanium dioxide powder and silicon dioxide powder at 1800-2100 ℃, and preserving heat to obtain first glass liquid;

the mass ratio of the titanium dioxide powder to the silicon dioxide powder is (90-98) to (2-10), preferably 95 ^-8 The temperature is lower than the expansion coefficient of the quartz, and a pressure stress layer can be formed on the surface of the quartz optical fiber to inhibit the expansion of microcracks; if the mass ratio of the titanium dioxide powder to the silicon dioxide powder is higher than (90-98) to (2-10), the expansion coefficient difference is too large, the interlayer is difficult to be well fused during film coating, and the phenomenon of interface or peeling occurs; if the mass ratio of the titanium dioxide powder to the silicon dioxide powder is lower than (90-98) to (2-10), the difference between the expansion coefficients of the prepared glass and quartz is not large enough, and the reinforcing effect is not obvious.

The heat preservation time is 1-3 h, the glass liquid can be uniformly melted only by sufficient heat preservation time, the heat preservation time is usually 2h, a good effect can be obtained, the heat preservation time is usually 1h, and the phenomenon of nonuniform melting sometimes occurs. And the heat preservation time is 3 hours, the good effect can be achieved, but the requirements on energy consumption and equipment are high.

S2, clarifying the first glass liquid obtained in the step S1 at 2000-2100 ℃ to obtain a second glass liquid; if the clarifying temperature is higher than 2100 ℃, the requirements on equipment, vessels and the like are higher, and the manufacturing cost is increased; if the temperature is lower than 2000 ℃, the fluidity of the melted silicon dioxide is poor, and the mixing and melting uniformity of the silicon dioxide and the titanium dioxide is poor; the clarification time is 30-60 min, and in view of time saving, 30min is generally selected.

S3, performing water quenching and mechanical crushing on the second glass liquid obtained in the step S2 to obtain a glass particle target material; the crushed granularity is 0.1-2 mm, so that the glass particle target material is relatively compact in a crucible and long in evaporation time; if the granularity is too large, the gaps among the glass particle targets are large, so that the actually available targets are reduced during evaporation; if the particle size is too small, the powder is likely to be dusted or splashed by the impact of the electron beam.

S4, placing the glass particle target material and the quartz optical fiber preform obtained in the step S3 in a vapor deposition vacuum value, and baking; then, under the oxygen-containing vacuum condition, the quartz optical fiber perform rotates and coaxially reciprocates, and simultaneously carries out evaporation under a set electron beam to obtain a titanium dioxide-doped quartz optical fiber perform (an optical fiber perform with a titanium dioxide-doped quartz skin layer);

the baking temperature is 300-500 ℃, preferably 400 ℃, at the temperature, the quartz rod has better bonding force, the film layer can not fall off or peel, if the temperature is lower than 300 ℃, the bonding force effect of the film layer is not good, and if the temperature is higher than 500 ℃, the bonding force improving effect is not obvious, and the service life of other components of the equipment can be influenced.

The oxygen-containing vacuum conditions include: the vacuum degree is lower than 5.9 multiplied by 10 ^-3 Pa; the introduction rate of the oxygen is 10-15 sccm; less than 5.9X 10 ^-3 When Pa is used, the vacuum chamber can not only be ensured to contain a trace amount of oxygen to prevent the oxygen mismatch problem between the silicon dioxide and the silicon dioxide, but also the evaporation efficiency at a certain speed can be ensured,the vacuum chamber can better perform the evaporation test, and the evaporation efficiency is very high; if the degree of vacuum is higher than 5.9X 10 ^-3 Pa, the evaporation efficiency is obviously reduced, and even the evaporation device can not normally operate; the oxygen content is a conflicting process, and in order to prevent oxygen mismatch between titania and silica, more oxygen is supplemented as good as possible, and on the other hand, in order to improve the evaporation rate and film quality, less gas is better. Therefore, the oxygen charging flow is set to be in the range of 10-15 sccm, preferably 10-12 sccm, so that the vacuum pump is started and releases oxygen at the same time, and micro oxygen is released in a vacuumized dynamic environment, and the vacuum pump and the micro oxygen finally reach a dynamic balance integral state or a vacuum state.

The diameter of the preform is generally determined according to the size of the drawing furnace, and usually 10 to 50mm is selected as the diameter of the silica optical fiber preform.

The set value of the electron beam is 100-150 mA, preferably 100mA, and TiO is doped at the time ₂ The quartz target can be evaporated, and the evaporation rate is not too high, so that the uniformity and the stable control of the film layer are facilitated.

The autorotation speed of the optical fiber preform is 20-100 r/min, the speed of coaxial reciprocating motion is 90-500 mm/s, and the amplitude is consistent with the rod length of the preform; preferably, the rotation speed of the optical fiber perform is 50r/min, the speed of the coaxial reciprocating motion is 200mm/s, and at this speed, a uniform and stable film layer can be formed on the surface of the optical fiber perform, the speed is too slow, the uniformity is not good, the vibration of the optical fiber perform is easily caused too fast, and the quality of the film coating of the optical fiber perform is also influenced.

The evaporation under the vacuum condition containing oxygen to enable the quartz optical fiber perform to rotate and coaxially reciprocate and simultaneously perform evaporation under a set electron beam specifically comprises the following steps: when the vacuum degree is lower than 1.6 multiplied by 10 ^-3 Pa (less than 1.6X 10) ^-3 Pa, below which there is no contamination by other impurity gases; if it is higher than 1.6X 10 ^-3 Pa, impurity gas is easily contained in the vacuum chamber, which affects the purity of the substrate and the film layer and reduces the evaporation rate), oxygen is introduced at a rate of 10-15 sccm until the vacuum degree is stabilized below 5.9 × 10 ^-3 When Pa, opening electron beam and adjusting the position of the electron beam to make the electron beam face the target material, then increasing the electron beam at a speed lower than 25mA/min until the electron beam is stabilized at 100-150 mA, so that the optical fiber preform is evaporated under the conditions that the autorotation speed is 20-100 r/min, the coaxial reciprocating speed is 90-500 mm/s, and the amplitude is consistent with the rod length of the preform.

S5, drawing the optical fiber preform with the titanium dioxide-doped quartz skin layer, wherein a shallow titanium dioxide-containing diffusion layer is formed on the outer surface layer of the diameter of the drawn quartz optical fiber, and the quartz glass fiber with the titanium dioxide-doped quartz cladding is obtained; the ratio of the thickness of the titanium dioxide-doped quartz cladding of the quartz glass fiber yarn to the thickness of the quartz glass fiber yarn is equal to the ratio of the thickness of the titanium dioxide-doped quartz skin layer of the prefabricated rod to the thickness of the prefabricated rod;

s6, after the quartz glass fiber is cooled to room temperature, organic coating is formed on the surface of the titanium-doped quartz cladding, and the titanium dioxide-doped quartz fiber with the fiber diameter of 250 mu m is obtained, wherein the tensile strength of the titanium dioxide-doped quartz fiber is obviously improved by 5.19% compared with that of the common titanium metal-undoped quartz fiber.

In some embodiments, the step S4 may specifically include:

as shown in fig. 2, placing a glass particle target material in a crucible, then placing the crucible and a quartz optical fiber preform in an evaporation vacuum value, covering a baffle, and opening a baking mode; starting a vacuum pump to vacuumize when the vacuum degree is lower than 1.6 multiplied by 10 ^-3 When Pa, slowly introducing a certain amount of oxygen into the vacuum chamber at a rate of 10-12 sccm until the vacuum degree is stabilized to be lower than 5.9 × 10 ^-3 Pa, starting an electron beam, adjusting the position of the electron beam to enable the electron beam to be located in the crucible, and then slowly increasing the electron beam at a speed of less than 25mA/min until the electron beam is stabilized at 100-150 mA; starting mechanical rotation of the optical fiber perform to enable the optical fiber perform to rotate and perform coaxial reciprocating motion so as to ensure that a film layer evaporated on the outer surface of the perform is uniform; turning off the baffle plate for evaporation and timing, wherein the thickness of the film layer is regulated and controlled through evaporation time, and the thickness of the film layer is thickened along with the increase of the evaporation time;the single-layer thickness of the film layer is controlled to be between 1 and 20 mu m, in the range, the low-expansion characteristic of the film layer can be exerted, the uniform and stable evaporation of the film layer can be realized, the film layer is too thick, cracks or peeling delamination are easy to occur, and if the film layer is too thin, the reinforcing effect is not achieved. The baffle plate is used for blocking the target material so as to prevent evaporation on the quartz rod. Closing the baking, closing the electron beam, cooling for 0.5-1 hour along with the vacuum chamber (generally, the cooling time is more than 30min, the temperature of the chamber is close to the room temperature after the furnace door is opened), and filling air into the vacuum chamber (the vacuum value is a vacuum negative pressure state, the chamber door can be opened only when the vacuum chamber is filled with air and reaches the standard atmospheric pressure to take out the sample), so as to obtain the deposited doped TiO ₂ Quartz optical fiber preforms with a quartz glass film layer, i.e. with TiO ₂ A quartz optical fiber preform with a doped quartz skin layer.

The crucible can be made of high-temperature refractory metal such as copper, high-temperature-resistant stainless steel, molybdenum or tungsten, preferably molybdenum which is high-temperature refractory metal, and the technology for processing the molybdenum crucible is relatively mature.

The invention adopts the doped TiO with low expansion coefficient ₂ The quartz glass is used as an evaporation target material to carry out evaporation coating on the quartz optical fiber preform, and the low expansion characteristic of the coating can form a layer of compressive stress on the surface of the optical fiber, thereby playing a remarkable role in optical fiber reinforcement; the optical fiber perform is subjected to vapor deposition coating by adopting a radial autorotation and alternate reciprocating motion mode, so that the thickness uniformity of the coating on the perform is good, and the appearance limitation that only a coating plane is totally coated is effectively avoided; by carrying out electron beam evaporation coating on the optical fiber perform in advance and then carrying out subsequent drawing on the optical fiber perform, the surface layer of the drawn optical fiber is provided with a layer of titanium dioxide-doped low-expansion quartz optical fiber with equal proportional thickness, the process has good controllability and is easy to realize, so that the tensile strength of the quartz optical fiber is improved by 5.19 percent at most.

The invention also provides a communication optical fiber which is the titanium dioxide doped quartz optical fiber.

As shown in FIG. 2, the present invention also provides an evaporation apparatus for a silica optical fiber preform, comprising a vacuum chamber 6A base 2 is arranged in the empty chamber 6, and the base 2 is respectively fixed with a device for containing doped TiO ₂ The crucible 1 of the quartz glass target C, two bearing supports 11, a film thickness detector 4 and a roaster 7; the crucible is placed on the base, so that water cooling and evaporation are facilitated, and evaporation is performed from bottom to top. The bearing support is placed on the base to support more stably; a baffle 3 is arranged above the molybdenum crucible 1, and whether the upper part of the crucible is covered or not is controlled by a PLC control cabinet; the baffle 3 is connected with the base 2 through a rotating shaft, so that the crucible can be covered or uncovered; a gear transmission mechanism is arranged above the bearing support 11, so that the rotation of the quartz optical fiber perform rod can be realized; the bearing support 11 is movably connected with a metal fixing piece for fixing the preform B;

the gear transmission mechanism comprises a first disc gear 8, a second disc gear 8a, two bevel gears 9 and a displacement cycle telescopic device 10 which are connected with each other; the metal fixing piece is connected with one end of a displacement cycle expansion piece 10, the other end of the displacement cycle expansion piece 10 is connected with one bevel gear 9, the two bevel gears 9 are meshed and connected with each other, the other bevel gear 9 is meshed and connected with a second disc gear 8a, the second disc gear 8a is meshed and connected with a first disc gear 8, the first disc gear 8 is connected with a motor through a shaft 12, the motor is arranged outside the vacuum chamber 6, and a circuit and the motor cannot be connected in the vacuum chamber due to high temperature in an evaporation coating vacuum chamber, so that the purpose of the arrangement is to transmit power of an external motor to a quartz optical fiber preform to realize rotation and reciprocating motion, and therefore uniform film plating on the surface of the quartz optical fiber preform is realized;

the lower part of the base 2 is connected with a vacuum pump 5 through a pipeline and used for continuously vacuumizing a vacuum chamber 6; the top of the vacuum chamber is provided with an oxygen through hole, the oxygen through hole is connected with a high-pressure oxygen tank through a pipeline, and the bottom of the vacuum chamber is vacuumized, so that the dynamic balance flow of oxygen from the top to the bottom in the vacuum chamber can be realized, and the possible small amount of oxygen mismatch caused by evaporation can be compensated;

in addition, the evaporation device further comprises a beam current device (not shown in the figure, conventional in the field) positioned in front of and below the base 2 and used for passing throughDeflecting voltage control electron beam bombarding doped TiO in molybdenum crucible 1 ₂ And heating and evaporating the quartz glass target C to form a film M on the surface of the preform B.

In addition, a PLC control cabinet (not shown in the figure, conventional in the art) is included for controlling the size and position of the electron beam stream of the beam current device, the opening and closing of the vacuum pump, and the opening and closing of the baffles.

Will dope TiO ₂ Putting a quartz glass target material C into a molybdenum crucible 1 (for example, the diameter is 40 mm), wherein the target material does not exceed 4/5 of the volume of the molybdenum crucible; then, the preform is placed on a holder, the inlet of the vacuum chamber is closed, and vacuum pumping is performed by a vacuum pump 5 while the degree of vacuum is lower than 1.6X 10 ^-3 When Pa, slowly introducing oxygen into the vacuum chamber at a rate of 10-12 sccm until the vacuum degree is stabilized at less than 5.9 × 10 ^-3 When Pa, starting an electron beam of the beam current device, adjusting the position of the electron beam to enable the electron beam to be located in the molybdenum crucible 1, and then slowly increasing the electron beam at a speed of less than 25mA/min until the electron beam is stabilized at 100-150 mA;

in the vacuum chamber, because the temperature is high, a control circuit cannot be arranged in the vacuum chamber of the evaporation chamber, an external motor is started to enable a shaft 12 to start to operate, a gear transmission mechanism starts to operate under the driving of the shaft 12, a first disc gear 8 drives a second disc gear 8a to rotate, then the second disc gear 8a drives a bevel gear 9 to rotate, then the bevel gear 9 drives another bevel gear 9 to rotate, and the other bevel gear 9 enables an optical fiber preform to radially rotate and coaxially reciprocate (namely, axially rotate and periodically move) through a shaft and a displacement expansion piece, so that the two-dimensional movement of the optical fiber preform is realized, and a film layer evaporated on the outer surface of the preform is uniform;

then, starting a roaster 7 and a film thickness detector 4, turning off the baffle 4 for evaporation and timing, regulating and controlling the thickness of the film layer through evaporation time, and feeding back the thickness on line through the film thickness detector; closing the baking, closing the electron beam, cooling along with the vacuum chamber, filling air into the vacuum chamber, opening the door of the vacuum chamber and taking out the sample to obtain the product with TiO ₂ A quartz optical fiber preform with a doped quartz skin layer.

The following is a further description with reference to specific examples.

Example 1

The embodiment provides a preparation method of a titanium dioxide-doped silica optical fiber, which comprises the following steps:

(1) Weighing SiO ₂ 190g of powder, tiO ₂ 10g of powder; mixing and uniformly stirring the weighed powder, and then placing the mixed powder in a tungsten crucible;

(2) Placing the tungsten crucible containing the mixed powder into a high-temperature furnace, heating the tungsten crucible to 2000 ℃ from room temperature at a heating rate of 10 ℃/min, and preserving heat for 2h;

(3) Clarifying at 2050 ℃ for 1 hour after the powder is completely melted;

(4) Pouring the quartz glass liquid into a mould, when the temperature is reduced to about 1200 ℃, pouring the glass into cold water for water quenching and crushing, and combining mechanical crushing to ensure that the granularity of target particles is distributed in the range of 0.1-2 mm;

(5) Soaking cullet in ethanol, ultrasonically cleaning (power of 70W and time of 10 min), drying (60 ℃ and 4 h), and placing cullet particles serving as a target material in a molybdenum crucible, wherein the target material is not more than 4/5 of the volume of the molybdenum crucible (after the target material exceeds 4/5 of the volume of the crucible, the target material particles are easily scattered out of the crucible under the excitation of electron beams);

(6) Preparing a commercial quartz optical fiber preform with the diameter of 30mm, the length of 600mm and the purity of 99.9999%, placing the optical fiber preform on a bracket right above a vacuum chamber of a vapor deposition machine, wherein the bracket can control the optical fiber preform to perform radial autorotation and axial reciprocating motion, as shown in figure 2;

(7) Placing a molybdenum crucible and a quartz optical fiber preform in an evaporation vacuum value, covering a baffle, and starting a baking mode, wherein the baking temperature is set to 400 ℃;

(8) Starting a vacuum pump to vacuumize when the vacuum degree is lower than 1.6 multiplied by 10 ^-3 When Pa, slowly introducing oxygen into the vacuum chamber at a rate of 10sccm until the vacuum degree is stabilized at 5.8 × 10 ^-3 Pa, starting the electron beam, adjusting the position of the electron beam to enable the electron beam to be located in the molybdenum crucible, and then slowly increasing the electron beam at the speed of 25mA/min until the electron beam is stabilized at125mA。

(9) The motor is started to make the shaft 12 start to operate, so that the optical fiber perform rod realizes radial autorotation and performs coaxial reciprocating motion, and the film layer evaporated on the outer surface of the perform rod is ensured to be uniform. The autorotation speed of the optical fiber preform is 40r/min, the speed of coaxial reciprocating motion is 100mm/s, and the amplitude is 600mm;

(10) Turning off the baffle plate for evaporation and timing, regulating and controlling the thickness of the film layer through evaporation time, feeding back the thickness on line through a film thickness monitor, controlling the thickness of a single layer of the film layer to be 8 mu m, and controlling the evaporation time to be 80min;

(11) Closing the baking, closing the electron beam, cooling for 1 hour along with the vacuum chamber, and filling air into the vacuum chamber (the vacuum value is vacuum negative pressure state, only the vacuum chamber is filled with air to reach standard atmospheric pressure, the chamber door of the vacuum chamber can be opened to take out the sample), to obtain the deposited doped TiO ₂ Quartz optical fiber preforms with a quartz glass film layer, i.e. with TiO ₂ A quartz optical fiber preform doped with a quartz skin layer;

in order to verify whether or not the film layer composition and the target material composition changed after the vapor deposition, the following description deals with the above-mentioned TiO-containing material ₂ The silica optical fiber preform doped with silica sheath was subjected to energy dispersive element surface scanning analysis (EDS) and the results are shown in fig. 3. As can be seen from FIG. 3, the film layer contains Ti and is uniformly distributed, which indicates that doped TiO is deposited during the vacuum evaporation process ₂ The quartz glass film layer does not have element mismatch phenomenon.

To further illustrate the above-mentioned having TiO ₂ Uniformity of titanium distribution in silica optical fiber preform doped with silica sheath layer deposition of doped TiO for example 1 ₂ The titanium of the quartz glass film layer was analyzed quantitatively by XRF as shown in table 1. It can be seen from table 1 that the content of titanium is within the normal fluctuation range, the content of Ti in the film layer after evaporation is substantially consistent with the content of Ti in the target material, and the film layer has no obvious component mismatch.

TABLE 1

(12) Will have TiO ₂ Fixing the quartz optical fiber prefabricated rod doped with the quartz skin layer on the top of a drawing tower, heating the bottom of the quartz optical fiber prefabricated rod at 2000 ℃, and forming a shallow low-expansion doped TiO on the outer surface layer of the drawn quartz optical fiber after the bottom of the quartz optical fiber prefabricated rod is melted ₂ A quartz glass film layer, a quartz glass fiber with a fiber diameter of 125 μm, and TiO doped ₂ The thickness of the quartz glass film layer is 33nm, namely the thickness of the titanium dioxide-doped quartz cladding layer is 33nm; the wire diameter is controlled by the wire drawing speed, and the wire diameter is monitored and fed back on line by an electronic monitor. After the quartz glass fiber is cooled to room temperature, coating organic paint on the surface of the titanium dioxide-doped quartz cladding with the coating thickness of 62.5 mu m to form an organic coating, and finally obtaining the titanium dioxide-doped quartz fiber with the fiber diameter of 250 mu m.

According to the national standard GB/T15972.31-2008 optical fiber test method specification-part 31: the method and procedure for measuring mechanical properties-tensile strength-the average tensile strength of the prepared titania-doped silica optical fiber was 6.086GPa. The titania-doped silica fiber is different from a common silica fiber in that the first cladding of the titania-doped silica fiber is a silica cladding, the second cladding of the titania-doped silica fiber is a titania-doped silica cladding, and the thickness of the titania-doped silica fiber is 33nm; and the first cladding and the second cladding of the common silica optical fiber are silica claddings.

Example 2

(1) Weighing SiO ₂ Powder 180g, tiO ₂ 20g of powder. Mixing and uniformly stirring the weighed powder, and then placing the mixed powder in a tungsten crucible;

(2) Placing the tungsten crucible containing the mixed powder into a high-temperature furnace, heating the tungsten crucible to 1900 ℃ from room temperature at a heating rate of 10 ℃/min, and preserving the heat for 2 hours;

(3) Clarifying at 2000 ℃ for 1h after the powder is completely melted;

(4) Pouring the quartz glass liquid into a mould, pouring the glass into cold water for water quenching and crushing when the temperature is reduced to be about 1200 ℃, and continuously mechanically crushing large particles in the glass to ensure that the crushed particle size is in the range of 0.1-2 mm;

(5) Soaking cullet in ethanol, ultrasonically cleaning (power of 70W and time of 10 min), drying (60 ℃,4 h), and placing cullet particles as a target material in a molybdenum crucible, wherein the target material does not exceed 4/5 of the volume of the molybdenum crucible (after the target material exceeds 4/5 of the volume of the crucible, the target material particles are easy to fall out of the crucible under the excitation of an electron beam);

(6) Preparing a commercial quartz optical fiber preform rod with the diameter of 30mm and the length of 600mm, and placing the optical fiber preform rod on a bracket right above a vacuum chamber of an evaporator, wherein the bracket can control the optical fiber preform rod to perform radial autorotation and axial reciprocating motion, as shown in figure 2;

(7) Placing a molybdenum crucible and a quartz optical fiber preform in an evaporation vacuum value, covering a baffle, and starting a baking mode, wherein the baking temperature is set to 350 ℃;

(8) Starting a vacuum pump to vacuumize when the vacuum degree is lower than 1.6 multiplied by 10 ^-3 When Pa, slowly introducing oxygen into the vacuum chamber at a rate of 10sccm until the vacuum degree is stabilized at 5.8 × 10 ^-3 Pa, starting an electron beam, adjusting the position of the electron beam to enable the electron beam to be located in the molybdenum crucible, and then slowly increasing the electron beam at the speed of 25mA/min until the electron beam is stabilized at 100mA;

(9) And starting the motor to enable the optical fiber perform to realize radial autorotation and perform coaxial reciprocating motion so as to ensure that the film layer evaporated on the outer surface of the perform is uniform. The autorotation speed of the optical fiber preform is 60r/min, the speed of coaxial reciprocating motion is 150mm/s, and the amplitude is 600mm;

(10) Turning off the baffle plate for evaporation and timing, regulating and controlling the thickness of the film layer through evaporation time, feeding back the thickness on line through a film thickness monitor, controlling the thickness of a single layer of the film layer to be 15 mu m, and controlling the evaporation time to be 150min;

(11) Closing the baking, closing the electron beam, cooling for 1h along with the vacuum chamber, and filling air into the vacuum chamber to obtain the deposited doped TiO ₂ Quartz fiber preform with quartz glass filmMaking rods, i.e. with TiO ₂ A quartz optical fiber preform doped with a quartz skin layer;

(12) Will have TiO ₂ Fixing the quartz optical fiber prefabricated rod doped with the quartz skin layer on the top of a drawing tower, heating the bottom of the quartz optical fiber prefabricated rod at 2000 ℃, and forming a shallow low-expansion doped TiO on the outer surface layer of the drawn quartz optical fiber after the bottom of the quartz optical fiber prefabricated rod is melted ₂ A quartz glass film layer, a quartz glass fiber with a fiber diameter of 125 μm, and TiO doped ₂ The thickness of the quartz glass film layer is 62.5nm, namely the thickness of the titanium dioxide-doped quartz cladding layer is 62.5nm; the wire diameter is controlled by the wire drawing speed, and the wire diameter is monitored and fed back on line by an electronic monitor. After the quartz glass fiber is cooled to room temperature, coating an organic coating on the surface of the titanium dioxide-doped quartz cladding with the coating thickness of 62.5 mu m to form an organic coating, and finally obtaining the titanium dioxide-doped quartz optical fiber with the fiber diameter of 250 mu m.

According to the national standard GB/T15972.31-2008 optical fiber test method specification-part 31: the method and procedure for measuring mechanical properties-tensile strength-the average tensile strength of the prepared titania-doped silica optical fiber was 6.079GPa. The titania-doped silica fiber is different from a common silica fiber in that the first cladding of the titania-doped silica fiber is a silica cladding, the second cladding is a titania-doped silica cladding, and the thickness of the titania-doped silica fiber is 62.5nm; and the first cladding and the second cladding of the common quartz optical fiber are quartz claddings.

Example 3

(1) Weighing SiO ₂ 196g of powder TiO ₂ 4g of powder. Mixing and uniformly stirring the weighed powder, and then placing the mixed powder in a tungsten crucible;

(2) Placing the tungsten crucible containing the mixed powder into a high-temperature furnace, heating the tungsten crucible to 2100 ℃ from room temperature at a heating rate of 10 ℃/min, and preserving heat for 2 hours;

(3) Clarifying for 1h at 2150 ℃ after the powder is completely melted;

(6) Preparing a commercial quartz optical fiber preform with the diameter of 30mm and the length of 600mm, and placing the optical fiber preform on a bracket right above a vacuum chamber of a vapor deposition machine, wherein the bracket can control the optical fiber preform to perform radial autorotation and axial reciprocating motion, as shown in figure 2;

(7) Placing a molybdenum crucible and a quartz optical fiber preform in an evaporation vacuum value, covering a baffle, and starting a baking mode, wherein the baking temperature is set to be 500 ℃;

(8) Starting a vacuum pump to vacuumize when the vacuum degree is lower than 1.6 multiplied by 10 ^-3 When Pa, slowly introducing oxygen into the vacuum chamber at a rate of 10sccm until the vacuum degree is stabilized at 5.8 × 10 ^-3 Pa, turning on the electron beam and adjusting the position of the electron beam to enable the electron beam to be located in the molybdenum crucible, and then slowly increasing the electron beam at the speed of 25mA/min until the electron beam is stabilized at 140mA.

(9) And starting the motor to enable the optical fiber perform to realize radial autorotation and perform coaxial reciprocating motion so as to ensure that the film layer evaporated on the outer surface of the perform is uniform. The autorotation speed of the optical fiber preform is 20r/min, the speed of coaxial reciprocating motion is 90mm/s, and the amplitude is 600mm;

(10) Turning off the baffle plate for evaporation and timing, regulating and controlling the thickness of the film layer through evaporation time, feeding back the thickness on line through a film thickness monitor, controlling the thickness of a single layer of the film layer to be 4 mu m, and controlling the evaporation time to be 40min;

(11) Closing the baking, closing the electron beam, cooling for 1h along with the vacuum chamber, charging air into the vacuum chamber,the resulting deposited doped TiO ₂ Quartz optical fiber preforms with a quartz glass film layer, i.e. with TiO ₂ A quartz optical fiber preform doped with a quartz skin layer;

(12) Will have TiO ₂ Fixing the quartz optical fiber prefabricated rod doped with the quartz skin layer on the top of a drawing tower, heating the bottom of the quartz optical fiber prefabricated rod at 2000 ℃, and forming a shallow low-expansion doped TiO on the outer surface layer of the drawn quartz optical fiber after the bottom of the quartz optical fiber prefabricated rod is melted ₂ A quartz glass film layer, a quartz glass fiber with a fiber diameter of 125 μm, and TiO doped ₂ The thickness of the quartz glass film layer is 17nm, namely the thickness of the titanium dioxide-doped quartz cladding layer is 17nm; the wire diameter is controlled by the wire drawing speed, and the wire diameter is monitored and fed back on line by an electronic monitor. After the quartz glass fiber is cooled to room temperature, coating organic paint on the surface of the titanium dioxide-doped quartz cladding with the coating thickness of 62.5 mu m to form an organic coating, and finally obtaining the titanium dioxide-doped quartz fiber with the fiber diameter of 250 mu m.

According to the national standard GB/T15972.31-2008 optical fiber test method specification-part 31: the method and procedure for measuring mechanical properties-tensile strength-the average tensile strength of the prepared titania-doped silica optical fiber was 6.042GPa. The titania-doped silica fiber is different from a common silica fiber in that a first cladding of the titania-doped silica fiber is a silica cladding, a second cladding of the titania-doped silica fiber is a titania-doped silica cladding, and the thickness of the titania-doped silica fiber is 17nm; and the first cladding and the second cladding of the common silica optical fiber are silica claddings.

Example 4

(1) Weighing SiO ₂ Powder 180g, tiO ₂ 6g of powder; mixing and uniformly stirring the weighed powder, and then placing the mixed powder in a tungsten crucible;

(3) Clarifying for 1h at 2150 ℃ after the powder is completely melted;

(6) Preparing a commercial quartz optical fiber preform rod with the diameter of 30mm, the length of 600mm and the purity of 99.9999 percent, placing the optical fiber preform rod on a bracket right above a vacuum chamber of an evaporator, wherein the bracket can control the optical fiber preform rod to perform radial autorotation and axial reciprocating motion, as shown in figure 2;

(8) Starting a vacuum pump to vacuumize when the vacuum degree is lower than 1.6 multiplied by 10 ^-3 When Pa, slowly introducing oxygen into the vacuum chamber at a rate of 10sccm until the vacuum degree is stabilized at 5.8 × 10 ^-3 Pa, turning on the electron beam, adjusting the position of the electron beam to enable the electron beam to be located in the molybdenum crucible, and then slowly increasing the electron beam at the speed of 25mA/min until the electron beam is stabilized at 125mA.

(9) And starting the motor to enable the optical fiber perform to realize radial autorotation and perform coaxial reciprocating motion so as to ensure that the film layer evaporated on the outer surface of the perform is uniform. The autorotation speed of the optical fiber preform is 40r/min, the speed of coaxial reciprocating motion is 100mm/s, and the amplitude is 600mm;

(11) Close offBaking, closing electron beam, cooling with the vacuum chamber for 1h, and charging air into the vacuum chamber (vacuum value is vacuum negative pressure state, 8 only charging air into the vacuum chamber to reach standard atmospheric pressure, opening the vacuum chamber door to take out the sample), to obtain the deposited doped TiO ₂ Quartz optical fiber preforms with a quartz glass film layer, i.e. with TiO ₂ A quartz optical fiber preform doped with a quartz skin layer;

According to the national standard GB/T15972.31-2008 optical fiber test method specification-part 31: the method and the test procedure of the mechanical property, namely tensile strength, carry out the strength test on the prepared quartz optical fiber doped with the titanium dioxide, and the average tensile strength reaches 6.061GPa. The titania-doped silica fiber is different from a common silica fiber in that a first cladding of the titania-doped silica fiber is a silica cladding, a second cladding of the titania-doped silica fiber is a titania-doped silica cladding, and the thickness of the titania-doped silica fiber is 33nm; and the first cladding and the second cladding of the common quartz optical fiber are quartz claddings.

Example 5

(1) Weighing SiO ₂ Powder 180g, tiO ₂ 20g of powder; mixing the weighed powdersUniformly stirring, and then placing the mixed powder in a tungsten crucible;

(3) Clarifying at 1950 deg.C for 1h after the powder is completely melted;

(8) Starting a vacuum pump to vacuumize when the vacuum degree is lower than 1.6 multiplied by 10 ^-3 When Pa, slowly introducing oxygen into the vacuum chamber at a rate of 10sccm until the vacuum degree is stabilized at 5.8 × 10 ^-3 Pa, starting an electron beam, adjusting the position of the electron beam to enable the electron beam to be located in the molybdenum crucible, and then slowly increasing the electron beam at the speed of 25mA/min until the electron beam is stabilized at 125mA;

(11) Closing the baking, closing the electron beam, cooling the electron beam along with the vacuum chamber for 1h, and filling air into the vacuum chamber (the vacuum value is vacuum negative pressure state, only the vacuum chamber is filled with air to reach standard atmospheric pressure, the chamber door of the vacuum chamber can be opened to take out the sample), so as to obtain the deposited doped TiO ₂ Quartz optical fiber preforms with a quartz glass film layer, i.e. with TiO ₂ A quartz optical fiber preform doped with a quartz skin layer;

(12) Will have TiO ₂ Fixing the quartz optical fiber prefabricated rod doped with quartz skin layer on the top of a drawing tower, heating the bottom of the quartz optical fiber prefabricated rod at 2000 ℃, and forming a shallow low-expansion doped TiO on the outer surface layer of the drawn quartz optical fiber after the bottom of the quartz optical fiber prefabricated rod is melted ₂ A quartz glass film layer, a quartz glass fiber with a fiber diameter of 125 μm, and TiO doped ₂ The thickness of the quartz glass film layer is 33nm, namely the thickness of the titanium dioxide-doped quartz cladding layer is 33nm; the wire diameter is controlled by the wire drawing speed, and the wire diameter is monitored and fed back on line by an electronic monitor. After the quartz glass fiber is cooled to room temperature, coating organic paint on the surface of the titanium dioxide-doped quartz cladding with the coating thickness of 62.5 mu m to form an organic coating, and finally obtaining the titanium dioxide-doped quartz fiber with the fiber diameter of 250 mu m.

According to the national standard GB/T15972.31-2008 optical fiber test method specification-part 31: the method and procedure for measuring mechanical properties-tensile strength-the average tensile strength of the prepared titania-doped silica optical fiber was 6.098GPa. The titania-doped silica fiber is different from a common silica fiber in that a first cladding of the titania-doped silica fiber is a silica cladding, a second cladding of the titania-doped silica fiber is a titania-doped silica cladding, and the thickness of the titania-doped silica fiber is 33nm; and the first cladding and the second cladding of the common quartz optical fiber are quartz claddings.

Comparative example 1

The same procedure as that of example 1 is adopted for drawing, only a commercial high-purity silica optical fiber preform (the preform has a smooth and flat surface, a diameter of 30mm and a length of 600 mm) of an original optical fiber preform is drawn, the wire diameter of the drawn wire is 125 μm, the optical fiber is coated with an organic coating (the coating material is acrylic resin and the coating thickness is 62.5 μm) after the drawing, and after the coating is finished, the optical fiber is taken up by a roller; when the optical fiber is cooled, according to the national standard GB/T15972.31-2008 optical fiber test method specification-part 31: method and procedure for measuring mechanical properties-tensile strength, the optical fiber thus prepared was subjected to strength test to obtain a tensile strength of 5.785GPa.

Comparative example 2

The comparative example provides a preparation method of a titania-doped silica optical fiber, comprising the following steps:

(1) Weighing SiO ₂ Powder 180g, tiO ₂ 2g of powder; mixing and uniformly stirring the weighed powder, and then placing the mixed powder into a tungsten crucible;

(3) After the powder is completely melted, clarifying for 1h at 2150 ℃;

(11) Closing the baking, closing the electron beam, cooling the electron beam along with the vacuum chamber for 1h, and filling air into the vacuum chamber (the vacuum value is a vacuum negative pressure state, and only when the vacuum chamber is filled with air and reaches the standard atmospheric pressure, the door of the vacuum chamber can be opened to take out the sample), so as to obtain the deposited doped TiO ₂ Quartz optical fiber preforms with a quartz glass film layer, i.e. with TiO ₂ A quartz optical fiber preform doped with a quartz skin layer;

(12) Will have TiO ₂ Fixing the quartz optical fiber prefabricated rod doped with the quartz skin layer on the top of a drawing tower, heating the bottom of the quartz optical fiber prefabricated rod at 2000 ℃, and forming a shallow low-expansion doped TiO on the outer surface layer of the drawn quartz optical fiber after the bottom of the quartz optical fiber prefabricated rod is melted ₂ A quartz glass film layer, a quartz glass fiber with a fiber diameter of 125 μm, doped with TiO ₂ The thickness of the quartz glass film layer is 33nm, namely the thickness of the titanium dioxide-doped quartz cladding is 33nm; the wire diameter is controlled by the wire drawing speed,the wire diameter is monitored and fed back on line through an electronic monitor. After the quartz glass fiber is cooled to room temperature, coating organic paint on the surface of the titanium dioxide-doped quartz cladding with the coating thickness of 62.5 mu m to form an organic coating, and finally obtaining the titanium dioxide-doped quartz fiber with the fiber diameter of 250 mu m.

According to the national standard GB/T15972.31-2008 optical fiber test method specification-part 31: the method for measuring mechanical properties and the test procedure-tensile strength, the strength test is carried out on the prepared quartz fiber doped with titanium dioxide, and the average tensile strength reaches 5.787GPa. The titania-doped silica fiber is different from a common silica fiber in that a first cladding of the titania-doped silica fiber is a silica cladding, a second cladding of the titania-doped silica fiber is a titania-doped silica cladding, and the thickness of the titania-doped silica fiber is 33nm; and the first cladding and the second cladding of the common quartz optical fiber are quartz claddings.

Comparative example 3

The comparative example provides a preparation method of a titanium dioxide doped silica optical fiber, which comprises the following steps:

(1) Weighing SiO ₂ Powder 180g, tiO ₂ 30g of powder; mixing and uniformly stirring the weighed powder, and then placing the mixed powder in a tungsten crucible;

(3) Clarifying at 1950 deg.C for 1h after the powder is completely melted;

(8) Starting a vacuum pump to vacuumize when the vacuum degree is lower than 1.6 multiplied by 10 ^-3 When Pa, slowly introducing oxygen into the vacuum chamber at a rate of 10sccm until the vacuum degree is stabilized at 5.8 × 10 ^-3 Pa, turning on the electron beam and adjusting the position of the electron beam to enable the electron beam to be located in the molybdenum crucible, and then slowly increasing the electron beam at the speed of 25mA/min until the electron beam is stabilized at 125mA.

(10) Turning off the baffle plate for evaporation and timing, wherein the thickness of the film layer is regulated and controlled through evaporation time, the thickness is fed back on line through a film thickness monitor, the single-layer thickness of the film layer is controlled to be 8 mu m, and the evaporation time is 80min;

(12) Will have TiO ₂ The quartz optical fiber preform with the doped quartz skin layer is fixed at the top of a drawing tower, the bottom of the quartz optical fiber preform is heated at 2000 ℃, after the heating, the coating and the quartz rod are not drawn in an expected equal proportion, the skin layer largely drops and flows, and a small amount of bubbles appearThis shows that, under the composition, the film layer flows first after heating, so that the mass ratio of the film layer to the quartz layer is unbalanced during wire drawing, and the wire diameter is discontinuous and broken. This indicates that when the content of titanium dioxide is too high, the softening point of the vapor-deposited film layer is lower than that of quartz glass, and the difference between the expansion coefficient of the film layer and that of quartz is large, which causes the discontinuity phenomenon in the subsequent optical fiber drawing.

Comparative example 4

(1) Weighing SiO ₂ 199g of powder, tiO ₂ Powder 1g. Mixing and uniformly stirring the weighed powder, and then placing the mixed powder in a tungsten crucible;

(3) Clarifying for 1h at 2150 ℃ after the powder is completely melted;

(4) Pouring the quartz glass liquid into a mould, when the temperature is reduced to be about 1200 ℃, pouring the glass into cold water for water quenching and crushing, and then continuously mechanically crushing large particles in the glass to ensure that the crushed particle size is within the range of 0.1-2 mm;

(8) Starting a vacuum pump to vacuumize when the vacuum degree is lower than 1.6 multiplied by 10 ^-3 When Pa, slowly introducing a certain amount of oxygen into the vacuum chamber at a rate of 10sccm until the beam current is stabilized at 5.8 × 10 ^-3 Pa, turning on the electron beam, adjusting the position of the electron beam to enable the electron beam to be located in the molybdenum crucible, and then slowly increasing the electron beam at the speed of 25mA/min until the electron beam is stabilized at 150mA.

(12) Will have TiO ₂ Fixing the quartz optical fiber prefabricated rod doped with the quartz skin layer on the top of a drawing tower, heating the bottom of the quartz optical fiber prefabricated rod at 2000 ℃, and forming a shallow low-expansion doped TiO on the outer surface layer of the drawn quartz optical fiber after the bottom of the quartz optical fiber prefabricated rod is melted ₂ A quartz glass film layer, a quartz glass fiber with a fiber diameter of 125 μm, and TiO doped ₂ The thickness of the quartz glass film layer is 33nm, namely the thickness of the titanium dioxide-doped quartz cladding layer is 33nm; the wire diameter is controlled by the wire drawing speed, and the wire diameter is monitored and fed back on line by an electronic monitor. After the quartz glass fiber is cooled to room temperature, coating organic paint on the surface of the titanium dioxide-doped quartz cladding with the coating thickness of 62.5 mu m to form an organic coating, and finally obtaining the dioxide-doped quartz fiber with the fiber diameter of 250 mu mA titanium silica optical fiber.

According to the national standard GB/T15972.31-2008 optical fiber test method specification-part 31: the method and procedure for measuring mechanical properties-tensile strength-the average tensile strength of the prepared titania-doped silica optical fiber was 5.786GPa. The titania-doped silica fiber is different from a common silica fiber in that a first cladding of the titania-doped silica fiber is a silica cladding, a second cladding of the titania-doped silica fiber is a titania-doped silica cladding, and the thickness of the titania-doped silica fiber is 33nm; and the first cladding and the second cladding of the common quartz optical fiber are quartz claddings.

As can be seen from the data of examples 1 to 5 and comparative example 1, the tensile strength (6.086 GPa) of the silica optical fiber obtained in example 1 is improved by about 5.19% compared with the tensile strength (5.785 GPa) of the silica optical fiber obtained in comparative example 1; the tensile strength (6.079 GPa) of the silica optical fiber obtained in example 2 is improved by about 5.07 percent compared with the tensile strength (5.785 GPa) of the silica optical fiber obtained in comparative example 1; the tensile strength (6.042 GPa) of the quartz optical fiber obtained in example 3 is improved by about 4.43% compared with the tensile strength (5.785 GPa) of the quartz optical fiber obtained in comparative example 1; the tensile strength (6.061 GPa) of the silica optical fiber obtained in example 4 is improved by about 4.771% compared with the tensile strength (5.785 GPa) of the silica optical fiber obtained in comparative example 1; the tensile strength (6.091 GPa) of the quartz optical fiber obtained in example 5 is improved by about 5.29% compared with the tensile strength (5.785 GPa) of the quartz optical fiber obtained in comparative example 1; the tensile strengths of examples 1, 2, 3, 4, 5 were all improved to different degrees due to the doped TiO ₂ The quartz glass tube has low expansion characteristic, has a thermal expansion coefficient lower than that of quartz glass, and is doped with trace TiO ₂ When the quartz glass film layer is attached to the surface of the quartz optical fiber, the film layer has a small amount of compressive stress, so that the expansion of cracks can be effectively blocked, the crack expansion can be finally stopped, and the effect of reinforcing the optical fiber can be achieved.

As can be seen by comparing the data of comparative examples 2 to 4 with that of comparative example 1, the tensile strength (5.787 GPa) of the silica fiber obtained in comparative example 2 was improved by about 0.035% over the tensile strength (5.785 GPa) of the silica fiber obtained in comparative example 1, and the improvement effect was slight, indicating that the doped TiO was very slight ₂ Quality is inAt the content of 1.1wt%, the difference between the expansion coefficient of the film layer and the expansion coefficient of quartz is small, and no compressive stress is formed to inhibit crack propagation; in the comparative example 3, the mass ratio of the film layer to the quartz layer is unbalanced, and the wire diameter is discontinuous and broken. This shows that when the content of titanium dioxide is too high, the softening point of the vapor deposition film layer is lower than that of quartz glass, and the difference between the expansion coefficient of the film layer and the quartz is larger, which causes the discontinuity phenomenon of the subsequent optical fiber drawing; the tensile strength (6.042 GPa) of the silica fiber obtained in the comparative example 4 is improved by about 0.017% compared with the tensile strength (5.786 GPa) of the silica fiber obtained in the comparative example 1, and the improvement effect is slight, which shows that the doped TiO is ₂ At a mass of 0.5wt%, the difference between the expansion coefficient of the film and that of quartz is small, and no compressive stress is formed to suppress crack propagation.

In the description of the present invention, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some embodiments, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention can be made, and the same should be considered as the disclosure of the present invention as long as the idea of the present invention is not violated.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A preparation method of a titanium dioxide doped silica optical fiber is characterized by comprising the following steps:

s1, melting titanium dioxide powder and silicon dioxide powder at 1800-2100 ℃, and preserving heat to obtain first glass liquid; the mass ratio of the titanium dioxide powder to the silicon dioxide powder is (90-98) to (2-10);

s3, performing water quenching and mechanical crushing on the second glass liquid obtained in the step S2 to obtain a glass particle target material;

s4, placing the glass particle target material and the quartz optical fiber preform obtained in the step S3 in an evaporation vacuum chamber for baking; then, under the oxygen-containing vacuum condition, the quartz optical fiber perform rod carries out vapor deposition under a set electron beam while rotating and coaxially reciprocating to obtain a titanium dioxide-doped quartz optical fiber perform rod; the baking temperature is 300-500 ℃; the diameter of the quartz optical fiber preform is 10-50 mm; the oxygen-containing vacuum conditions include: vacuum degree of less than 5.9X 10 ^-3 Pa, the introduction rate of oxygen is 10-15 sccm; the set value of the electron beam is 100-150 mA; the autorotation speed of the optical fiber preform is 20-100 r/min, the speed of coaxial reciprocating motion is 90-500 mm/s, and the amplitude is consistent with the rod length of the preform;

2. The method for preparing the titania-doped silica optical fiber according to claim 1, wherein in step S1, the holding time is 1-3 hours; in the step S2, the clarification time is 30-60 minutes; in the step S3, the granularity of the water quenching and the mechanical crushing is 0.1-2 mm.

3. The titania-doped silica fiber prepared by the preparation method according to claim 1 or 2, wherein the titania-doped silica fiber comprises a fiber core, a first cladding, a second cladding and an organic cladding in sequence from inside to outside;

the first cladding is a quartz cladding;

the second cladding is a titanium dioxide-doped quartz cladding;

4. The titania-doped silica fiber of claim 3, wherein the thickness ratio of the first cladding, the second cladding and the organic cladding is (52.5-58.4) to (0.0025-0.25): 62.5.

5. the titania-doped silica optical fiber of claim 3, wherein the second cladding has a silica to titania mass ratio of (90-98) to (2-10).

6. An optical fiber for telecommunications, characterized in that it is the titania-doped silica optical fiber according to any one of claims 3 to 5.