CN107151092A - The preparation method and doped single crystal multi-core fiber of a kind of doped single crystal multi-core fiber - Google Patents

Abstract

The invention provides a preparation method of a doped single crystal multi-core optical fiber and a doped single crystal multi-core optical fiber. Doped single crystal multi-core fiber contains two or more doped single crystal cores in the same silica cladding, and the fiber waveguide structure is composed of low refractive index silica silica glass and high refractive index doped single crystal. It is to obtain a porous optical fiber preform rod, and then draw a porous capillary tube, and then inject the doped crystal melt into the micropores in the quartz capillary tube under high temperature and high pressure to form a polycrystalline core, and finally make the core through transverse heating. Steps such as single crystallization are completed to prepare a silica cladding doped single crystal multi-core optical fiber. By combining the capillary porous inner melt injection with later crystal growth, the doped single crystal multi-core optical fiber grown by this method has the advantages of controllable wire diameter length, arbitrary arrangement of core number and position, etc., and can be used in micro and small Phase modulators, optical switches and interferometers controlled by online photons.

Description

A preparation method of doped single crystal multi-core optical fiber and doped single crystal multi-core optical fiber

technical field

The invention relates to an optical fiber, in particular to a doped single crystal multi-core optical fiber. The invention also relates to a method of manufacturing such an optical fiber.

Background technique

Single crystal optical fiber is also called crystal fiber or fiber crystal. It is a single crystal that grows crystal material into a fiber shape, with a diameter ranging from a few microns to hundreds of microns. It has both the functions of bulk crystals and ordinary silica fibers. Compared with bulk crystals, single crystal optical fibers have the characteristics of small size, high integration, and can be coupled with quartz optical fibers. It has the advantages of matching the lasers in the visible and non-visible bands, and can be used for the transmission of high-power lasers. It has important practical value in the field of optoelectronics.

Ordinary pure single crystals have limited functions. In order to obtain the desired physical properties, it is often necessary to dope impurity elements in the crystal. For example, doping Mg elements in nonlinear optical lithium niobate crystals can enhance the ability to resist laser damage. Hydrogen can increase the refractive index of the crystal; doping a certain amount of phosphorus in the semiconductor silicon crystal can obtain an n-type semiconductor, and doping a certain amount of aluminum or gallium can obtain a p-type semiconductor; doping a lanthanide element in the crystal can obtain fluorescence characteristic materials, etc.

Common crystal fiber growth methods include: (1) Guided mode method, related literature and reports include: [1] NorioOhnishi and Takafumi Yao, A Novel Growth Technique for Single-Crystal Fibers: The Micro-Czochralski(μ-CZ) Method, Jpn.J.Appl.Phys., 28(2):L278-L280; 1989; [2] Dae-Ho Yoon, Ichiro Yonenaga, Tsuguo Fukuda, Norio Ohnishi, Crystal growth of dislocation-free LiNbO ₃ single crystals by micro pulling down method, J.Cryst.Growth, 142:339-343, 1994; [3] Zhong Heyu, Hou Yinchun, Zhi Ningsan, Chen Xingda, Wang Renshu, growth of lithium niobate single crystal optical fiber, Journal of Silicates, 19(6 ): 527-531, 1991. This type of growth method is that the melt is drawn from a mold with small holes or protrusions, and then fed into the seed crystal for directional growth. Its main advantage is that it can continuously grow long and special cross-section optical fibers, but limited by the mold material, it is difficult to grow crystal fibers with high melting point, and it is difficult to avoid pollution problems. (2) Laser heating pedestal method, related literature and reports are: [4] Yalin Lu, Dajani A.Iyad, and RJKnize, Fabrication and characterization of periodically poled lithium niobate single crystalfibers, Integrated Ferroelectrics, 90:53-62, 2007; [5] Japanese Patent Production of Single Crystal Optical Fiber, Bibliographic data: JPH0375292(A) - 1991-03-29. In this method, _CO2 laser heating is used to form a local melting zone, and single crystal fibers are continuously grown after feeding seed crystals. The advantage of this method is that it does not require molds and is pollution-free at high temperatures, and can grow high-melting-point optical fibers with a fast growth rate. However, limited by the growth conditions, it can only be made into short optical fibers, and it is difficult to control the diameter of the optical fiber. (3) Direct molding method, the literature and reports involved are: [6] P.Rudolph, T. Fukuda, Fiber crystal growth from the melt, Crystal Research and Technology, 34:3–40, 1999; [7] J. Ballato, T.Hawkins, and P.Foy et al.Siliconoptical fiber.Optics Express.2008 16:18675-18683; [8]Yi-Chung Huang, and Jau-Sheng Wang et al.Preform fabrication and fiber drawing of 320nm broadband Cr-doped fibers, Optics Express. 2007, 15:14382-14388. In this method, the capillary effect is used to make the melt crystallize and solidify at one time to form a crystal optical fiber, or to obtain a crystal core optical fiber through a tube rod method and wire drawing technology. However, this kind of preparation method can only make short optical fibers, and it is difficult to ensure that the core is a single crystal. (4) Other growth methods, such as the Japanese patent (Fibrous Oxide Optical Single Crystal and Its Production, Bibliographic data: JPH08278419 (A)-1996-10-22) provides a preparation method for lithium niobate crystal core optical fiber, the The method is to grow a layer of low refractive index oxide single crystal cladding layer on the surface of single crystal optical fiber by epitaxial growth technology. In this crystal fiber preparation method, the melting point of the oxide of the epitaxial layer must be lower than that of the single crystal fiber, and at the same time, limited by the melt of the epitaxial layer and the pulling mechanism, the grown crystal fiber is shorter and has a larger outer diameter. Also, as the U.S. Patent (Method of cladding single crystal optical fiber, Patent Number, 5077087; Claddings for single crystal optical fibers and devices and methods and apparatus for making such claddings, Patent Number, 5037181) describes a doped lithium niobate single crystal The preparation method of the optical fiber, the method makes the oxide coating coated on the surface layer of the single crystal optical fiber diffuse into the optical fiber through high temperature treatment, so as to reduce the refractive index of the surface layer of the single crystal optical fiber. In the preparation method of the crystal optical fiber, the ions in the cladding of the crystal optical fiber are distributed in a parabola, and the refractive index distribution of the cladding will gradually decrease from the outside to the inside, which will lead to an increase in fiber loss. In addition, the controllability of this method is poor, the degree of diffusion is uneven, the depth of diffusion is not suitable for control, and the stability of product performance is relatively poor. In addition, Chinese patents (a microstructure cladding single crystal fiber and its preparation method, CN102298170A; a cladding single crystal fiber with a Bragg structure and its preparation method, CN102253445A) disclose a single crystal fiber composed of a microstructure cladding and a crystal core. Preparation method of crystal fiber. The method is as follows: first, a hollow cladding sleeve is prepared, a micro-sized single crystal is inserted into the hollow cladding sleeve, and then the cladding sleeve is heated and stretched so that the fiber core is wrapped by the cladding sleeve to produce a microstructure clad single crystal optical fiber . The disadvantages of this optical fiber preparation method are: firstly, due to the surface electrostatic attraction, it is difficult to insert long-scale micro-single crystals into the micropores of the cladding sleeve; secondly, the large difference between the softening temperature point of quartz glass and the crystal melting point leads to In the process of stretching the cladding sleeve, the volatilization of the core melt occurs discontinuously or missing, and the quartz dissolves in the core melt, resulting in impurity pollution and hindering the crystallization process of the core melt, so that no single crystal can be formed; third, The stretching temperature gradient of the cladding sleeve is much higher than the temperature gradient force that promotes the crystallization of the core melt to nucleate and grow to form a single crystal, which does not meet the kinetic conditions of single crystal growth.

To sum up, the above-mentioned crystal fiber either has no cladding structure, or the core is difficult to guarantee to be a single crystal, and the fiber usually only contains a pure crystal core, which does not involve ion doping, so the prepared The function of the crystal fiber is limited, and it cannot meet the needs of further optical fiber sensing and new fiber integrated devices.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a doped single-crystal multi-core optical fiber with simple and practical process, controllable outer diameter of optical fiber quartz cladding and single crystal core diameter, and uniform crystal quality. The object of the present invention is also to provide a doped single crystal multi-core optical fiber which has the functions of bulk crystal and common silica optical fiber.

The preparation method of the doped single crystal multi-core optical fiber of the present invention is:

Step 1: Obtain a porous optical fiber preform by stacking beam method or quartz rod punching method, and heat and seal one end of the porous optical fiber preform with a hydrogen-oxygen flame, and then cooperate with the pumping and inflating device, use the optical fiber drawing tower at 1900 °C or more The temperature draws the porous optical fiber preform into a porous capillary;

Step 2: Nest the platinum inner crucible containing the doped polycrystalline powder in the sealed tungsten outer crucible, and place them together in a high-temperature muffle furnace to heat at a temperature slightly higher than the melting point of the polycrystalline powder to cause the doping in the inner crucible The heteropolycrystalline powder is completely melted and in an overheated state, and then an inert gas is filled into the inside of the outer crucible through a raised inner hole on the sealing cover of the outer crucible to maintain a constant positive pressure. The inner hole is inserted into the inner crucible melt, and the other end of the porous capillary is connected with the external air pumping device, so that a constant negative pressure is formed in the capillary hole. In the process, the internal stress of the optical fiber is eliminated by cooling down, the melt solidifies and becomes polycrystalline, and a doped polycrystalline multi-core optical fiber is obtained;

Step 3: Place the prepared doped polycrystalline multi-core fiber on a horizontal fiber taper machine with a rotating fixture. While the fiber is rotating laterally, the micro-heating device moves along the guide rail from one end to the other to heat the fiber. The micro-heating device The central temperature is higher than the melting point of the core polycrystal but lower than the softening point of quartz. At this time, the core in the doped polycrystalline multi-core fiber is heated into a melt, and the outer cladding keeps the quartz glass solid. In the micro-sized capillary inner hole And under the dynamic action of temperature gradient, the crystallization of the core melt nucleates and grows to form a single crystal, which is made into a doped single crystal multi-core optical fiber;

Step 4: After the fiber core between the two ends of the fixture has been single-crystallized, move the part of the fiber that has not been single-crystallized to the two ends of the rotating fixture, and repeat the process of steps 1 to 3. The entire doped polycrystalline multi-core fiber All fiber cores are single crystallized.

The manufacturing method of the doped single crystal multi-core optical fiber of the present invention may also include:

1. The method to obtain the porous optical fiber preform is: first select the quartz capillary rod, use the stacking technology to form a stacking bundle, replace the quartz capillary rods at two or more positions in the stacking bundle with quartz capillaries of the same material, and then stack the stacking bundle Put it into a thin-walled quartz glass tube to form a composite porous optical fiber preform, and heat and seal one end of the porous optical fiber preform with a hydrogen-oxygen flame.

2. The method of obtaining a porous optical fiber preform is: punch two or more through holes on a section of solid quartz rod, and then weld a thin-walled quartz tube with the same outer diameter on one end of the quartz rod to form a welded porous optical fiber preform. The other end of the porous optical fiber preform is heated and sealed with an oxyhydrogen flame.

The doped single-crystal multi-core optical fiber of the present invention is: the quartz cladding contains two crystal cores, and the positions of the two crystal cores are asymmetrically or symmetrically distributed.

The doped single-crystal multi-core optical fiber of the present invention is: three crystal cores are contained in the quartz cladding at the same time, and the positions of the three crystal cores are distributed in an isosceles triangle or a straight line.

The doped single-crystal multi-core optical fiber of the present invention is: four crystal cores are contained in the quartz cladding at the same time, and the positions of the four crystal cores are rectangularly distributed.

The doped single-crystal multi-core optical fiber of the present invention is: the quartz cladding contains five crystal cores at the same time, and the positions of the five crystal cores are symmetrically distributed.

The doped single crystal multi-core optical fiber of the present invention can also realize multi-core optical fibers doped with different single crystal cores and different ions according to different core materials and doping ions.

The doped single crystal multi-core optical fiber of the present invention contains two or more doped single crystal cores in the same quartz cladding, and the melting point of the core crystal is lower than the softening point of the quartz cladding.

The invention provides a function of both bulk crystals and ordinary silica optical fibers, organically combines the excellent physical and optical properties of bulk doped crystals with the light guiding properties and geometric shapes of optical fibers, and can be applied to optical fiber transmission. Doped single crystal multi-core optical fiber with sense and novel fiber integrated devices. The invention also provides a method for manufacturing a doped single crystal multi-core optical fiber with a simple and practical preparation process, controllable outer diameter of the quartz cladding of the obtained optical fiber and controllable single crystal core diameter, and uniform crystal quality.

Compared with prior art, the advantage of the present invention is:

1. The doped single-crystal multi-core optical fiber produced has both the functions of bulk crystal and ordinary silica fiber, and organically combines the excellent physical and optical properties of bulk doped crystal with the optical conductivity and geometric shape of the optical fiber. It can be made into a fiber optic device with multiple functions, and is widely used in the fields of new fiber optic sensing and fiber optic communication.

2. The quartz cladding of the doped single crystal multi-core optical fiber contains multiple crystal cores at the same time, which can flexibly realize the doped single crystal optical fiber with various core arrangements, and the preparation process is simple and practical.

3. In the preparation process of doped single-crystal multi-core optical fiber, the porous capillary is prepared first, and then the melt is filled into the pores by high-pressure technology, and finally the core is single-crystallized by post-heating treatment. Based on this process, the preparation of different single crystal core materials and doped multi-core optical fibers can be conveniently realized, the crystal defects are few, and the grown single crystal core optical fibers are longer.

The invention of the above optical fiber manufacturing technology has broadened the types of doped single crystal multi-core optical fiber, especially for the preparation method of doped single crystal multi-core optical fiber, the manufacturing process is simple, and the low cost will help to promote it. to the market.

Description of drawings

Fig. 1 is a schematic cross-sectional view of an asymmetrical double-core doped single crystal fiber shown in Embodiment 1;

2 to 3 are schematic cross-sectional views of two asymmetric dual-hole optical fiber preforms shown in Embodiment 1;

4 is a schematic cross-sectional view of an asymmetric double-hole capillary shown in Embodiment 1;

5 is a schematic diagram of the preparation of an asymmetric double-core doped polycrystalline fiber shown in Embodiment 1;

Fig. 6 is a partially enlarged view of the double crucible shown in Fig. 5;

Fig. 7 (a) is the front view of the sealing cover of the outer crucible shown in Fig. 6, and Fig. 7 (b) is the top view of the sealing cover of the outer crucible shown in Fig. 6;

Fig. 8 is a schematic diagram of the gasket structure of the outer crucible shown in Fig. 6;

Fig. 9 (a) is the front view of the sealing nut on the outer crucible shown in Fig. 6, and Fig. 9 (b) is the top view of the sealing nut on the outer crucible shown in Fig. 6;

Fig. 10 is a schematic diagram of the process of single-crystallization of the core in the asymmetric double-core doped polycrystalline fiber shown in Embodiment 1;

FIG. 11 is a schematic diagram of the temperature field distribution in the heated optical fiber core along the axial direction of the optical fiber shown in FIG. 10;

12(a) to 12(e) are schematic cross-sectional views of other doped single crystal multi-core optical fibers.

detailed description

The present invention is described in more detail below in conjunction with accompanying drawing example:

The meanings of the reference marks on the drawings of the specification are: 1-doped single crystal core; 2-quartz cladding; 3-quartz glass capillary rod; 4-quartz glass capillary; 5-thin-walled quartz tube; 6-quartz Glass filled rod; 7-quartz rod; 8-through hole; 9-capillary hole; 10-quartz cladding; 11-high-purity argon cylinder; 12-pressure display gauge; 13-rubber tube; 14-furnace heating element; 15-tungsten tube; 16-heating furnace; 17-porous capillary; 18-rubber tube; 19-vacuum pump; 20-alumina fiber mat; 21-tungsten crucible; 22-platinum crucible; 23-melt; 24-zirconia Insulation sand; 25-external thread; 26-inner hole; 27-external thread; 28-conical hole; 29-internal thread; 30-inner hole; 31-sealing cap hole; 32-inner thread; 33-optical fiber rotation Fixture; 34-microelectric heating furnace; 35-doped polycrystalline multi-core optical fiber; 36-guide rail; 37-single crystal core; 38-quartz cladding; 39-core melting zone; 40-polycrystalline core; 41- Solid-liquid interface between polycrystalline core and melting zone; 42-solid-liquid interface between single crystal core and melting zone; I-compound asymmetric double-hole optical fiber preform; II-welded asymmetric double-hole optical fiber preform; Ⅲ-Asymmetric double-hole capillary; Ⅳ-Double crucible; Ⅴ-Sealing cover of the outer crucible; Ⅵ-Sealing gasket of the outer crucible; Ⅶ-Sealing nut on the outer crucible _; Single crystal zone temperature; T ₂ - melting zone temperature; T ₃ - polycrystalline zone temperature.

Embodiment one

Fig. 1 is a schematic cross-sectional view of the first magnesium ion-doped lithium niobate single crystal double-core optical fiber of the present invention, the core 1 is a magnesium ion doped lithium niobate single crystal, the core position is asymmetrically distributed, and the cladding 2 is quartz, and the refractive index of the core 1 is greater than that of the cladding 2.

Used inner and outer double crucibles in the manufacturing process of the present invention. Referring to Fig. 6, the outer crucible 21 is made of tungsten material, with a tungsten sealing cover V on it, and a high temperature resistant (1800°C) alumina fiber sealing gasket VI is filled between the two, and a sealing nut is included on the outer crucible sealing cover V VII, after the porous capillary 17 passes through the small hole 31 on the sealing nut VII and the conical hole 28 on the crucible sealing cover V, it is inserted into the melt 23 of the inner crucible, and the gap between the porous capillary and the conical hole adopts Alumina fiber mat 20 is used for sealing. The inner crucible 22 is made of platinum, which is filled with doped polycrystalline powder. The gap between the inner and outer crucibles is filled with zirconia heat insulating sand 24, which plays the role of heat preservation and fixing the inner crucible 22; referring to FIG. 7, the crucible sealing cover V contains Two raised inner holes, one of which has an external thread 25 and a tiny inner hole 26, high-purity inert gas is injected into the outer crucible 21 from the hole 26, and the other raised inner hole has an external thread 27 and a conical Shaped inner hole 28, conical inner hole 28 is filled with alumina fiber sealing pad 20, crucible sealing cover V has internal thread 29, and it cooperates with the external thread on the crucible 21 to be sealed and connected; In conjunction with Fig. 8, alumina fiber sealing pad There are two circular holes 30 on the VI, one of which communicates with the small hole 26 on the sealing cover V, and the other circular hole communicates with the conical hole 28 on the sealing cover V; in conjunction with Fig. 9, the sealing nut VII has There is a small hole 31 through which the optical fiber 17 passes, and the inner surface of the nut has an internal thread 32, which cooperates with the external thread 27 of the raised inner hole on the outer crucible sealing cover V to be sealed and connected.

With reference to Figures 2 to 5, Figure 10 and Figure 11, the preparation method of the magnesium ion-doped lithium niobate single crystal double-core optical fiber shown in Embodiment 1 includes the following steps:

1) Select a quartz glass capillary rod 3 with a length of 700 mm and an outer diameter of 1 mm, and close-packed hexagonal stacking to form a stacking bundle, and replace the quartz capillary rods at the central position and a non-central position in the stacking bundle with the same length and inner and outer diameters Quartz capillary 4, and then pack the stacked bundle into a In the quartz glass tube 5 with a length of 750mm, the end face of the quartz glass tube 5 is exposed at the end of one side of the accumulation bundle, and the gap filling diameter between the accumulation bundle and the quartz glass tube 5 is The quartz capillary rod 6 forms a composite porous optical fiber preform I, as shown in Figure 2; one end of the porous optical fiber preform is heated and sealed with an oxyhydrogen flame, and an exhaust and Inflatable device, which pumps air from the gap between the capillary rod, capillary and outer quartz sleeve, and maintains the vacuum degree above 0.3×10 ⁵ Pa; inflates the inside of the capillary to maintain the internal pressure of the capillary at ~1000Pa; The holey optical fiber preform is drawn to the outer diameter at a temperature above 1900°C on the tower The double-hole capillary III, as shown in Figure 4, the double-hole capillary contains two The asymmetric micropore 9, and the quartz cladding 10.

2) Place lithium niobate polycrystalline powder of the same composition (Li/Nb=48.6:51.4) doped with a trace amount of magnesium oxide in a platinum crucible 22, then nested in a tungsten crucible 21, and put them into a high-temperature muffle furnace together In 16, one end of the double-hole capillary 17 placed in the muffle furnace passes through the conical hole 28 on the crucible sealing cover V and is inserted into the lithium niobate polycrystalline powder, and the other end of the capillary passes through the muffle furnace and passes through the hose 18 is connected with the external air extraction device 19, and one end of the tungsten tube 15 with internal thread is connected with the external thread 25 on the crucible sealing cover V, and the other end of the tungsten tube 15 passes through the muffle furnace and connects with the external high-purity high-pressure tube 13 through the hose 13. The argon cylinders 11 are connected; the temperature of the muffle furnace is raised to 1250°C slightly higher than the melting point of lithium niobate crystals, but lower than the softening temperature of quartz, so that the doped polycrystalline powder in the crucible is completely melted and is in an overheated melting state. At this time The porous capillary still maintains the solid state of quartz glass, and one end of the capillary is immersed in the melt 23 of the inner crucible; through the high-purity argon gas bottle 11, the pressure display gauge 12, the flexible pipe 13 and the tungsten tube 15, the outer crucible 21 is filled with gas, Maintain a constant positive pressure above 0.2×10 ⁶ Mpa; through the vacuum pump 19 and hose 18, pump air inside the porous capillary hole 17 to form a constant negative pressure above 0.5×10 ⁵ Mpa. , the molten liquid 23 quickly fills the pores in the capillary, maintains the positive and negative pressure values, and cools down to room temperature by program-controlled cooling to eliminate the internal stress of the optical fiber. The core melt solidifies and becomes polycrystalline, forming magnesium-doped Lithium niobate polycrystalline dual-core optical fiber 35;

3) Place the doped polycrystalline double-core optical fiber 35 on a horizontal optical fiber tapering machine with a rotating fixture 33, as shown in Figure 10, the optical fiber rotates at a speed of ~10r/min, and the microelectric heating furnace 34 is driven by a stepping motor Next, move the heating fiber slowly from one end to the other along the guide rail at a speed of v=30-50mm/h; the central temperature of the micro-heating device is slightly higher than the melting point of lithium niobate core polycrystal at 1250°C, but lower than the softening point of quartz at 1730°C ℃. Taking one of the cores as an example, as shown in Figure 11, the core in the doped polycrystalline dual-core fiber is heated to form a melting zone 39, with a solid-liquid interface 41 and 42 on both sides, while the outer cladding 38 remains Keep the quartz glass solid; in the heated core area, the temperature gradient of the solid-liquid interface 42 between the melting zone 39 and the single crystal 37 is (T ₂ -T ₁ ), in this area, in the micro-sized capillary inner hole and the temperature gradient Under the action of power, the core melt crystallizes nucleation and grows to form a single crystal 37, completing the single crystallization process of the fiber core; another solid-liquid interface 41 is between the melting zone 39 and the polycrystal 40 when the micro-heating furnace moves forward. The interface between them, the temperature gradient in this region is (T ₁ -T ₃ ), where T ₂ >T ₁ =T ₃ ; when the fiber core between the two ends of the clamp 33 has completed single crystallization, move the non-single crystal Repeat the above-mentioned process several times, so that the cores in the entire doped polycrystalline dual-core optical fiber are single-crystallized.

Embodiment two

With reference to Fig. 3 and Fig. 4, the preparation method of another kind of magnesium ion doped lithium niobate single crystal double-core optical fiber of the present invention is, in a section of diameter Two diameters are punched on a solid quartz rod II with a length of 70mm 8 holes, and then weld a thin-walled quartz tube with the same outer diameter on one end of the quartz rod, heat and seal the other end of the porous quartz rod with an oxyhydrogen flame, forming a welded double-hole optical fiber preform, which is installed at one end of the quartz tube The inflating device is used to inflate the inside of the hole 8 to maintain a positive pressure of ~1000Pa; draw the double-hole optical fiber preform to the outer diameter at a temperature above 1900°C on the drawing tower The dual-bore capillary III, the dual-bore capillary contains two The asymmetric micropore 9, and the quartz cladding 10. All the other technological processes are identical with embodiment one.

According to the preparation method of the doped single-crystal multi-core optical fiber described in the present invention, single-crystal multi-core optical fibers with different arrangement structures of the cores can also be realized. For example: according to the different positions of the doped single-crystal dual-core fiber on the cladding circular cross-section, an asymmetrical dual-core fiber (as shown in Figure 1), and a symmetrical dual-core fiber (as shown in Figure 12(a) ) or any other dual-core optical fiber with any angular position relationship. The same process can prepare other types of doped single crystal multi-core optical fiber, such as isosceles triangular three-core optical fiber (as shown in Figure 12(b)), inline three-core optical fiber (as shown in Figure 12(c) ), rectangular four-core optical fiber (as shown in Figure 12(d)), symmetrical five-core optical fiber (as shown in Figure 12(e)), etc.

According to the preparation method of the doped single crystal multi-core optical fiber described in the present invention, different single crystal cores and doped multi-core optical fibers can also be realized according to different core materials and doping ions. For example: Magnesium-doped lithium tantalate single crystal multi-core fiber with nonlinear effect (the doped material is magnesium oxide, during the preparation process, the temperature of the electric heating furnace on the muffle furnace and optical fiber tapering machine is slightly higher than the melting point of lithium tantalate single crystal , but lower than the softening temperature of quartz); phosphorous or aluminum-doped semiconductor silicon single crystal multi-core optical fiber (the doped material is phosphorus or aluminum simple substance, during the preparation process, the temperature of the electric heating furnace on the muffle furnace and optical fiber tapering machine is slightly higher than The melting point of silicon single crystal, but lower than the softening temperature of quartz); samarium-doped calcium fluoride single-crystal multi-core optical fiber with laser characteristics, etc. (the doped substance is samarium trifluoride. The temperature of the electric heating furnace is slightly higher than the melting point of calcium fluoride single crystal, but lower than the softening temperature of quartz).

Claims (7)

1. a kind of preparation method of doped single crystal multi-core fiber, it is characterized in that：

Step one：Optical fiber preform is obtained by accumulating beam method or quartz pushrod punch method, and with oxyhydrogen flame to porous optical fiber Prefabricated rods one end carries out heating sealing, then coordinates pumping, aerating device, utilizes temperature of the fiber drawing tower more than 1900 DEG C Optical fiber preform is drawn into porous capillary；

Step 2：It will be equipped with crucible in the platinum of doped polycrystalline powder to be nested in sealed tungsten outer crucible, height be positioned over together The doped polycrystalline powder in interior crucible is caused to be completely melt to be in the temperature heating of a little higher than polycrystal powder fusing point in warm Muffle furnace Superheat state, is then filled with inert gas into outer crucible inside by outer crucible closure one raised endoporus, maintains constant Normal pressure, porous capillary one end is from another raised endoporus on outer crucible closure is inserted into interior crucible melt, porous hair The tubule other end is connected with outside air extractor so that constant negative pressure is formed in capilar bore, in inflation malleation and pumping negative pressure Under effect, melt liquid be rapidly filled with capillary it is porous in, cooling eliminate optical fiber internal stress, melt solidification become polycrystalline, obtain To doped polycrystalline multi-core fiber；

Step 3：The doped polycrystalline multi-core fiber of preparation is positioned over into the horizontal fiber with rolling clamp to draw on cone machine, optical fiber While transverse rotation, micro- heater moves heating optical fiber, micro- heater center temperature from one end to the other side along guide rail Higher than fibre core polycrystalline bulk melting point but less than quartzy softening point temperature, now the fibre core in doped polycrystalline multi-core fiber is heated to form molten Body, extramural cladding keeps quartz glass solid-state, the fibre core melt knot under micro-dimensioned capillary endoporus and thermograde dynamic action Crystalline form core, generation monocrystal of growing up, are made doped single crystal multi-core fiber；

Step 4：After the fiber core between fixture two ends completes single crystallization, the fiber section of mobile non-single crystallization extremely rotates Fibre core in fixture two ends, the process of repeat step one to three, whole doped polycrystalline multi-core fiber all realizes single crystallization.

2. the manufacture method of doped single crystal multi-core fiber according to claim 1, it is characterized in that：Obtain porous optical fiber prefabricated The method of rod is：Quartzy capillary rod is first chosen, with accumulation technology formation accumulation beam, by two in accumulation beam and above position Quartzy capillary rod replaces with the quartz capillary of phase same material, and then accumulation is got one's things ready in thin-walled quartz glass tube, constitutes multiple Box-like optical fiber preform, and heating sealing is carried out to optical fiber preform one end with oxyhydrogen flame.

3. the manufacture method of doped single crystal multi-core fiber according to claim 1, it is characterized in that：Obtain porous optical fiber prefabricated The method of rod is：Two and above through hole are made a call on one section of stuffed quartz rod, then the equal external diameter in the welding of quartz pushrod one end The thin-walled quartz ampoule of size, constitutes welded type optical fiber preform, and the optical fiber preform other end is entered with oxyhydrogen flame Row heating sealing.

4. doped single crystal multi-core fiber made from a kind of manufacture method of the doped single crystal multi-core fiber described in claim 1, its It is characterized in：Containing two crystal fibre cores in silica clad, two crystal fibre core positions are distributed into asymmetric or symmetric.

5. doped single crystal multi-core fiber made from a kind of manufacture method of the doped single crystal multi-core fiber described in claim 1, its It is characterized in：Simultaneously containing three crystal fibre cores in silica clad, three crystal fibre core positions are divided into isosceles triangle or in-line Cloth.

6. doped single crystal multi-core fiber made from a kind of manufacture method of the doped single crystal multi-core fiber described in claim 1, its It is characterized in：Simultaneously containing four crystal fibre cores, four crystal fibre core position rectangularity distributions in silica clad.

7. doped single crystal multi-core fiber made from a kind of manufacture method of the doped single crystal multi-core fiber described in claim 1, its It is characterized in：Simultaneously containing five crystal fibre cores in silica clad, five crystal fibre core positions are symmetrically distributed.