CN105923988B - The extruding production of the arbitrary adjustable oval core polarization-preserving fiber preform of ovality - Google Patents

Abstract

The invention discloses an extrusion preparation method of an ellipse-core polarization-maintaining optical fiber preform whose ellipticity can be adjusted arbitrarily. core-cladding ratio, and the ellipticity of the core is basically the same as the ellipticity of the extrusion hole on the corresponding extrusion die, the core and the cladding are very tightly bonded, the core-cladding interface is clear, Complete; the method of the present invention has good controllability, can accurately control the ellipticity of the fiber core of the elliptical-core polarization-maintaining optical fiber preform, and overcomes the structural defects of the elliptical-core polarization-maintaining optical fiber preform prepared by the traditional drilling or decompression shrinkage method At the same time, compared with the traditional improved chemical vapor deposition (MCVD) method for preparing optical fiber preforms, the cost is greatly reduced. In addition, it solves the core- Problems with poor cladding interfaces.

Description

Extrusion preparation method of elliptic core polarization-maintaining optical fiber preform with adjustable ellipticity

technical field

The invention belongs to the field of optical fiber preform production, in particular to an extrusion preparation method of an ellipse-core polarization-maintaining optical fiber preform whose ellipticity can be adjusted arbitrarily.

Background technique

Chalcogenide glass has good infrared transmission performance (depending on the composition, the transmission range is 0.5~25 μm), low phonon energy (less than 350 cm ^-1 ), high refractive index (2~3.5 ). In addition, chalcogenide glass also has a low transition temperature (Tg is 150~250 ℃), good mechanical properties, good chemical stability and thermal stability, and the chalcogenide glass optical fiber based on chalcogenide glass has Good mechanical properties and physical and chemical stability and other advantages.

Polarization-maintaining fiber is a fiber with strong polarization-maintaining ability for linearly polarized light. Due to its good ability to maintain the polarization state, it is widely used in fiber optic sensing and various polarization coherent detectors. According to the different ways of birefringence, polarization-maintaining fibers can be divided into geometric polarization-maintaining fibers and stress-type polarization-maintaining fibers. Geometric polarization-maintaining fiber is mainly due to the change of the refractive index of the fiber material due to the asymmetry of the geometric structure of the material, resulting in a birefringence effect, such as an elliptical core polarization-maintaining fiber. Generally, the ellipticity e of the elliptical-core polarization-maintaining fiber core The calculation formula is e=a/b, where a is the length of the major axis of the ellipse, and b is the length of the minor axis of the ellipse; the stress-type polarization-maintaining fiber mainly relies on the difference in thermal expansion coefficient between the externally embedded stress rod and the fiber core, so that Thermal stress is generated, and under the action of thermal stress, the refractive index of the material changes, resulting in a birefringence effect, such as a panda-type polarization-maintaining fiber. Since the birefringence of the geometric polarization-maintaining fiber is mainly caused by the geometric birefringence, compared with the stress-type polarization-maintaining fiber, the birefringence of the geometric polarization-maintaining fiber has the characteristics of good stability and temperature independence.

At present, the main methods for preparing elliptical core polarization-maintaining optical fiber preforms are grinding method and vacuum shrinkage method. The elliptical core polarization-maintaining fiber is prepared by grinding method. After depositing the cladding and the core rod according to the requirements, the arcs on both sides of the round rod are ground to be flat, and then drawn at high temperature to obtain the elliptical core polarization-maintaining fiber. In this method, since the processed surface of the preform is approximately elliptical, the grinding and polishing process is difficult, and the cross-sectional shape of the drawn optical fiber is not uniform, and the longitudinal uniformity is not easy to guarantee. The elliptical core polarization maintaining optical fiber preform is prepared by the decompression shrinkage method. First, the cladding and the core layer are deposited on the inner wall of the substrate tube by vapor deposition process, and then the air pressure in the tube is reduced to ensure that the air pressure in the deposition tube is lower than that of the external environment. Atmospheric pressure, then raising the temperature, under the action of low pressure and high temperature, the core layer is melted and shrunk into an ellipse shape, and the elliptical core polarization-maintaining optical fiber preform can be produced. In the process of preparing elliptical core polarization-maintaining optical fiber preform by decompression and shrinkage method, it is difficult to realize the production of high-precision elliptical core polarization-maintaining optical fiber preform due to the need to accurately control the relationship between gas volume and temperature, and the actual control is difficult .

The preparation of optical fiber preforms by extrusion is very suitable for chalcogenide glasses with steeper viscosity-temperature curves or easier crystallization. In this method, the glass composite body is placed in the extrusion cylinder and the temperature is heated above the softening temperature of the glass, and then the glass is extruded through a die at the bottom under high pressure at a fixed rate, thereby obtaining a glass with a core. Chalcogenide glass preform with cladding structure. In extrusion, higher pressure and lower extrusion temperature can effectively reduce the crystallization probability of glass. Moreover, during the extrusion process, the glass surface will not be disturbed by mechanical damage and external impurities, and the smoothness of the surface of all the extruded chalcogenide glass optical fiber preforms is much higher than that of other preparation methods. Most domestic patents on the preparation of traditional polarization-maintaining optical fiber preforms are concentrated on stress-type polarization-maintaining optical fibers, and there are few patents and documents on the preparation of geometric-type polarization-maintaining optical fiber preforms. Among them, the patent CN104445912A introduces a method for making a Panda polarization-maintaining optical fiber preform. Two polarization-maintaining stress rods are symmetrically fixed on both sides of the core rod according to the stress distribution requirements. The outer cladding is deposited to obtain a preformed rod loose body, and finally the preformed rod loose body is sintered to obtain a panda-shaped polarization-maintaining optical fiber preform rod with a circular interface. This patent involves an external deposition step, so the production cost is high, and in the process of external deposition, the stress rod is easy to burst, and it is difficult to accurately fix the polarization maintaining stress rod on both sides of the mandrel according to the stress requirement, so the preparation accuracy is not high . In summary, it is necessary to develop an extrusion preparation method for an elliptical-core polarization-maintaining optical fiber preform, and the present invention is proposed based on this purpose.

Contents of the invention

The technical problem to be solved by the present invention is to provide an extrusion preparation method of an elliptical core polarization-maintaining optical fiber preform whose ellipticity can be adjusted arbitrarily, which can not only precisely control the elliptical core polarization-maintaining optical fiber preform The ellipticity of the fiber core, and any elliptical core polarization-maintaining optical fiber preform can be prepared, and the preparation cost is greatly reduced.

The technical solution adopted by the present invention to solve the above-mentioned technical problems is: the extrusion preparation method of an elliptical core polarization-maintaining optical fiber preform whose ellipticity can be adjusted arbitrarily, which is characterized in that it includes the following steps:

(1) Prepare an extrusion cylinder with an upper opening, the bottom wall of the extrusion cylinder is provided with an extrusion port; prepare an extrusion head, the outer diameter of the extrusion head is the same as the diameter of the extrusion cylinder The inner diameter is suitable, the bottom of the extrusion head is provided with a cavity with a lower opening, the center of the cavity is provided with a first push rod, and the upper end of the first push rod is detachably connected and fixed On the described extrusion head, the bottom surface of the first push rod is flush with the bottom surface of the described extrusion head; prepare a protective sleeve with an opening at the bottom, and the center of the top wall of the protective sleeve is provided with A longitudinal through hole, the external dimensions of the protective sleeve are adapted to the cavity, and the outer diameter of the first ejector rod is greater than the diameter of the longitudinal through hole; prepare a set of extrusion dies, The set of extrusion dies is composed of a plurality of extrusion dies, and an elliptical extrusion hole is opened in the middle of each of the extrusion dies, and the ellipticity of the extrusion holes on each of the extrusion dies is not equal. , the outer diameter of each of the extrusion dies is adapted to the inner diameter of the protective sleeve; a core chalcogenide glass ingot and a cladding chalcogenide glass ingot rinsed with alcohol and dried are prepared, And the linear refractive index of the core chalcogenide glass is greater than that of the cladding chalcogenide glass, the outer diameter of the core chalcogenide glass ingot is adapted to the inner diameter of the protective sleeve, and the cladding The outer diameter of the layered chalcogenide glass ingot is adapted to the inner diameter of the extrusion cylinder;

(2) According to the ellipticity of the core of the elliptical-core polarization-maintaining optical fiber preform to be prepared, an extrusion die matching the ellipticity of the extrusion hole is selected from the set of extrusion dies;

(3) Put the cladding chalcogenide glass ingot into the bottom of the extrusion cylinder first, then put the core chalcogenide glass ingot and the selected extrusion mold into the protective sleeve , and make the core chalcogenide glass ingot stacked above the extrusion mold, and then place the protective sleeve together with the core chalcogenide glass ingot and the extrusion mold on the cladding sulfur on the glass ingot, and finally put the extrusion head together with the first ejector rod into the extrusion cylinder, so that the bottom surface of the first ejector rod and the protective sleeve The top surfaces are in contact, and the centers of the first ejector pin, the longitudinal through hole, the extrusion hole on the extrusion die and the extrusion port are on the same straight line;

(4) Heat the extrusion barrel until the temperature of the extrusion barrel reaches T, and the temperature T of the extrusion barrel satisfies: Tg<T<Tx, where Tg takes the value of the core chalcogenide glass and the cladding The larger value of the transition temperature of the two glasses of chalcogenide glass, Tx is the smaller value of the crystallization temperature of the two glasses of the core chalcogenide glass and the cladding chalcogenide glass, after heating, squeeze the cylinder The inner core chalcogenide glass ingot and the cladding chalcogenide glass ingot are softened by heat; press the top of the extrusion head, and push the protective sleeve together with the core chalcogenide through the first ejector pin Extruding the glass ingot and the extrusion mold into the clad chalcogenide glass ingot together so that the bottom surface of the extrusion mold is flush with the bottom surface of the clad chalcogenide glass ingot;

(5) Keep the temperature T of the extrusion barrel constant, take out the extrusion head, disassemble the first ejector pin, and assemble the second ejector pin with the same length as the first ejector pin on the On the extrusion head, the outer diameter of the second ejector rod is smaller than the aperture diameter of the longitudinal through hole, and then the extrusion head together with the second ejector rod is put into the extrusion barrel, Make the bottom surface of the second ejector rod flush with the top surface of the protective sleeve, apply pressure to the top of the extrusion head again, and make the bottom end of the second ejector rod pass through the The above longitudinal through hole extends into the core chalcogenide glass ingot, the core chalcogenide glass is extruded from the extrusion hole on the extrusion die, and finally the core chalcogenide glass and the cladding sulfur The glass is extruded together from the extrusion port, and the extruded product is a semi-finished product of an elliptical core polarization-maintaining optical fiber preform, and the semi-finished product is synchronously pulled by a traction mechanism during extrusion;

(6) After annealing the extruded semi-finished elliptical-core polarization-maintaining optical fiber preform at the Tg temperature for 4-6 hours, and then slowly cooling down to room temperature, a single-mode chalcogenide elliptical-core polarization-maintaining optical fiber preform is obtained.

When preparing an ellipse-core polarization-maintaining optical fiber preform by extrusion by the method of the present invention, the core chalcogenide glass ingot is placed in a protective casing, and the protective casing can protect the fiber core chalcogenide glass to ensure that the fiber core chalcogenide glass can be squeezed into the package as a whole. In the chalcogenide glass ingot, in addition, when the extrusion head is taken out, the first ejector pin is disassembled and the second ejector pin is replaced, the protective sleeve can also prevent the glass inside it from flowing upward and reversely under pressure, ensuring extrusion Pressing went smoothly. The extrusion process of the present invention is carried out in two stages: in the first stage, the extrusion cylinder is heated, and at a specific temperature, the core chalcogenide glass ingot and the cladding chalcogenide glass ingot are heated and softened, and the extrusion head Press the top of the top, push the protective sleeve together with the core chalcogenide glass ingot and the extrusion mold into the cladding chalcogenide glass ingot through the first ejector rod, so that the bottom surface of the extrusion mold and the cladding chalcogenide glass ingot The bottom surface is flush; in the second stage, keep the temperature T of the extrusion cylinder unchanged, and after replacing the second ejector pin, apply pressure to the top of the extrusion head again so that the bottom end of the second ejector pin extends through the longitudinal through hole. into the core chalcogenide glass ingot, extrude the core chalcogenide glass from the extrusion hole on the extrusion die, and finally extrude the core chalcogenide glass and the cladding chalcogenide glass from the extrusion port together. The finished product is the semi-finished product of the elliptical core polarization maintaining optical fiber preform. After annealing at Tg temperature for 4-6 hours, and then slowly cooling down to room temperature, a single-mode chalcogenide elliptical core polarization maintaining optical fiber preform is obtained. The elliptical core polarization maintaining optical fiber preform is Optical fiber preforms have a stable core-cladding ratio.

The extrusion process in step (4) and step (5) is carried out in a vacuum chamber. Before extrusion, the vacuum chamber is evacuated by a vacuum pump. When the vacuum degree in the vacuum chamber is lower than 10 ^-2 Pa, the Nitrogen or inert gas is added inside to make the air pressure in the vacuum chamber the same as the outside atmospheric pressure.

In the preparation method of the present invention, a set of extrusion molds is equipped. When preparing elliptical core polarization-maintaining optical fiber preforms with different ellipticities, the extrusion mold can be adjusted according to the ellipticity of the core of the elliptical-core polarization-maintaining optical fiber preform to be prepared. The ellipticity of the fiber core of the preformed rod can be adjusted and precisely controlled by changing different extrusion dies, which overcomes the disadvantage that the traditional preparation method cannot accurately control the ellipticity of the fiber core of the preformed rod. The value range of the ellipticity e of the extrusion holes on each of the extrusion dies is 0<e<∞.

Compared with the prior art, the present invention has the advantages of: the extrusion preparation method of the elliptical core polarization-maintaining optical fiber preform provided by the present invention with arbitrarily adjustable ellipticity, through two-stage hierarchical extrusion, the prepared elliptical core The polarization-maintaining optical fiber preform has high dimensional accuracy and a stable core-cladding ratio, and the ellipticity of the core is basically the same as that of the extrusion hole on the corresponding extrusion die, and the core and the cladding are closely bonded. Very compact, the core-cladding interface is clear and complete; the method of the present invention has good controllability, can accurately control the ellipticity of the core of the elliptical core polarization-maintaining optical fiber preform, and overcomes the traditional drilling or decompression shrinkage method to prepare The elliptical core polarization-maintaining optical fiber preform has the disadvantages of structural defects. At the same time, compared with the traditional method of preparing optical fiber preform by improved chemical vapor deposition (MCVD), the cost is greatly reduced. The problem of poor core-cladding interface exists in core polarization maintaining optical fiber preform.

Description of drawings

Fig. 1 is a schematic diagram of the state inside the extrusion cylinder before the first stage of extrusion in Embodiment 1 and Embodiment 2;

Fig. 2 is a schematic diagram of the state inside the extrusion cylinder at the end of the first stage of extrusion (that is, the start of the second stage of extrusion) in Embodiment 1 and Embodiment 2;

Fig. 3 is a schematic diagram of the state inside the extrusion cylinder when the second stage of extrusion ends in Embodiment 1 and Embodiment 2;

FIG. 4 is an end view of the elliptical-core polarization-maintaining optical fiber preform prepared by extrusion in Embodiment 1 and Embodiment 2. FIG.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Example 1: Using As ₄₀ S ₃₀ Se ₃₀ as the core glass material and As ₃₈ S ₆₂ as the cladding glass material, an elliptical core polarization-maintaining optical fiber preform with a core ellipticity of about 3 was prepared by extrusion. The pressure preparation method comprises the following steps:

(1) Prepare an extrusion cylinder 1 with an upper opening, the bottom wall of the extrusion cylinder 1 is provided with an extrusion port 11; prepare an extrusion head 2, the outer diameter of the extrusion head 2 is compatible with the inner diameter of the extrusion cylinder 1 Matching, the bottom of the extrusion head 2 is provided with a cavity 21 with a lower opening, the center of the cavity 21 is provided with a first ejector rod 31, the upper end of the first ejector rod 31 is detachably connected and fixed on the extrusion head 2, The bottom surface of the first push rod 31 is flush with the bottom surface of the extrusion head 2; prepare a protective sleeve 4 with a lower opening, the center of the top wall of the protective sleeve 4 is provided with a longitudinal through hole 41, and the profile of the protective sleeve 4 The size is adapted to the cavity 21, and the outer diameter of the first push rod 31 is greater than the aperture of the longitudinal through hole 41; a set of extrusion dies is prepared, and the extrusion dies are composed of a plurality of extrusion dies, each extrusion die There is an elliptical extrusion hole in the middle part of each extrusion die, and the ellipticity of the extrusion holes on each extrusion die is not equal, and the outer diameter of each extrusion die is compatible with the inner diameter of the protective sleeve 4; it is prepared to be washed with alcohol Cleaned and dried As ₄₀ S ₃₀ Se ₃₀ core chalcogenide glass ingot 6 and As ₃₈ S ₆₂ cladding chalcogenide glass ingot 7, outer diameter and protective jacket of As ₄₀ S ₃₀ Se ₃₀ core chalcogenide glass ingot 6 The inner diameter of the tube 4 is compatible, and the outer diameter of the As ₃₈ S ₆₂ clad chalcogenide glass ingot 7 is compatible with the inner diameter of the extrusion cylinder 1;

(2) According to the ellipticity (e=3) of the core of the elliptical core polarization-maintaining optical fiber preform to be prepared, an extrusion die 5 with an ellipticity of the extrusion hole 51 of 3 is selected from a set of extrusion dies ;

(3) First put the As ₃₈ S ₆₂ clad chalcogenide glass ingot 7 into the bottom of the extrusion cylinder 1, then put the As ₄₀ S ₃₀ Se ₃₀ fiber core chalcogenide glass ingot 6 and the selected extrusion mold 5 into the protection inside the sleeve 4, and make the As ₄₀ S ₃₀ Se ₃₀ core chalcogenide glass ingot 6 stacked on the extrusion die 5, and then put the protective sleeve 4 together with the As ₄₀ S ₃₀ Se ₃₀ core chalcogenide glass ingot 6 and the extrusion die 5 are placed on the As ₃₈ S ₆₂ clad chalcogenide glass ingot 7, and finally the extrusion head 2 together with the first ejector pin 31 is put into the extrusion barrel 1, so that the first ejector pin 31 The bottom surface is in contact with the top surface of the protective sleeve 4, and the centers of the first ejector rod 31, the longitudinal through hole 41, the extrusion hole 51 on the extrusion die 5 and the extrusion port 11 are on the same straight line;

(4) Heat the extrusion cylinder 1 until the temperature of the extrusion cylinder 1 reaches T, and the temperature T of the extrusion cylinder 1 satisfies: Tg<T<Tx, where Tg takes the value of As ₄₀ S ₃₀ Se ₃₀ fiber core Chalcogenide glass and As ₃₈ S ₆₂ cladding chalcogenide glass, which is the larger transition temperature of the two glasses, Tx is taken as the value of As ₄₀ S ₃₀ Se ₃₀ core chalcogenide glass and As ₃₈ S ₆₂ cladding chalcogenide The smaller value of the crystallization temperature of these two kinds of glasses, specifically control the temperature T of the extrusion cylinder 1 at 210 ℃ < T < 240 ℃, and squeeze the As ₄₀ S ₃₀ Se ₃₀ fiber core in the extrusion cylinder 1 after heating Chalcogenide glass ingot 6 and As ₃₈ S ₆₂ -clad chalcogenide glass ingot 7 are softened by heat; pressure is applied to the top of extrusion head 2, the first stage of extrusion starts, and the schematic diagram of the state inside the extrusion cylinder before the first stage of extrusion starts As shown in Fig. 1, the protective sleeve 4 is pushed by the first ejector pin 31 together with the As ₄₀ S ₃₀ Se ₃₀ core chalcogenide glass ingot 6 and the extrusion die 5 to be extruded into the As ₃₈ S ₆₂ cladding chalcogenide glass ingot 7, Make the bottom surface of the extrusion die 5 flush with the bottom surface of the As ₃₈ S ₆₂ clad chalcogenide glass ingot 7. At this time, the first stage of extrusion is completed, and the schematic diagram of the state inside the extrusion cylinder is shown in Figure 2;

(5) Keep the temperature T of the extrusion cylinder 1 constant, take out the extrusion head 2, disassemble the first ejector rod 31, and assemble the second ejector rod 32 equal in length to the first ejector rod 31 on the extrusion head 2, The outer diameter of the second push rod 32 is less than the aperture of the longitudinal through hole 41, and then the extrusion head 2 together with the second push rod 32 is put into the extrusion barrel 1, so that the bottom surface of the second push rod 32 is in contact with the protective sleeve 4 The top surface of the top of the extrusion head 2 is flush, and the top of the extrusion head 2 is pressed again, and the second stage of extrusion begins, so that the bottom end of the second ejector rod 32 passes through the longitudinal through hole 41 and extends into the As ₄₀ S ₃₀ Se ₃₀ core sulfur In the glass ingot 6, the As ₄₀ S ₃₀ Se ₃₀ core chalcogenide glass is extruded from the extrusion hole 51 on the extrusion die 5, and finally the As ₄₀ S ₃₀ Se ₃₀ core chalcogenide glass and As ₃₈ S ₆₂ The clad chalcogenide glass is extruded together from the extrusion port 11, and the extruded product is the semi-finished product 8 of the elliptical core polarization-maintaining optical fiber preform. At the same time, the semi-finished product 8 is pulled synchronously by a traction mechanism. The second stage of extrusion At the end of the extrusion, the schematic diagram of the state inside the extrusion cylinder at the end of the second stage of extrusion is shown in Figure 3;

(6) After annealing the extruded elliptical-core polarization-maintaining optical fiber semi-finished product 8 at Tg temperature for 5 hours, and then slowly cooling down to room temperature, the single-mode chalcogenide elliptical-core polarization-maintaining optical fiber preform of Example 1 was obtained. The extruded elliptical core polarization-maintaining optical fiber preform was observed under a microscope. It can be seen that the ellipticity of the core is basically the same as the ellipticity of the extrusion hole on the corresponding extrusion die, and the As ₄₀ S ₃₀ Se ₃₀ fiber The core and the As ₃₈ S ₆₂ cladding are very tightly bonded, the core-cladding interface is clear and complete, and there is no problem of poor core-cladding interface of the preform prepared by the traditional method, so the prepared Example 1 The elliptical core polarization maintaining optical fiber preform has high dimensional accuracy. The end view of the elliptical-core polarization-maintaining optical fiber preform prepared by extrusion in Example 1 is shown in FIG. 4 . In Fig. 4, 81 is a core glass, and 82 is a cladding glass.

Example 2: Using As ₄₀ S ₆₀ as the core glass material and As ₃₉ Se ₆₁ as the cladding glass material, an elliptical core polarization-maintaining optical fiber preform with a core ellipticity of about 3 is prepared by extrusion, and its extrusion preparation The method includes the following steps:

(1) Prepare an extrusion cylinder 1 with an upper opening, the bottom wall of the extrusion cylinder 1 is provided with an extrusion port 11; prepare an extrusion head 2, the outer diameter of the extrusion head 2 is compatible with the inner diameter of the extrusion cylinder 1 Matching, the bottom of the extrusion head 2 is provided with a cavity 21 with a lower opening, the center of the cavity 21 is provided with a first ejector rod 31, the upper end of the first ejector rod 31 is detachably connected and fixed on the extrusion head 2, The bottom surface of the first push rod 31 is flush with the bottom surface of the extrusion head 2; prepare a protective sleeve 4 with a lower opening, the center of the top wall of the protective sleeve 4 is provided with a longitudinal through hole 41, and the profile of the protective sleeve 4 The size is adapted to the cavity 21, and the outer diameter of the first push rod 31 is greater than the aperture of the longitudinal through hole 41; a set of extrusion dies is prepared, and the extrusion dies are composed of a plurality of extrusion dies, each extrusion die There is an elliptical extrusion hole in the middle part of each extrusion die, and the ellipticity of the extrusion holes on each extrusion die is not equal, and the outer diameter of each extrusion die is compatible with the inner diameter of the protective sleeve 4; it is prepared to be washed with alcohol Cleaned and dried As ₄₀ S ₆₀ core chalcogenide glass ingot 6 and As ₃₉ Se ₆₁ cladding chalcogenide glass ingot 7, outer diameter of As ₄₀ S ₆₀ core chalcogenide glass ingot 6 and inner diameter of protective sleeve 4 Compatible, the outer diameter of the As ₃₉ Se ₆₁ clad chalcogenide glass ingot 7 is compatible with the inner diameter of the extrusion cylinder 1;

(2) According to the ellipticity (e=3) of the core of the elliptical core polarization-maintaining optical fiber preform to be prepared, an extrusion die with an ellipticity of the extrusion hole 51 of 3 is selected from a set of extrusion dies 5 5;

(3) First put the As ₃₉ Se ₆₁ clad chalcogenide glass ingot 7 into the bottom of the extrusion cylinder 1, then put the As ₄₀ S ₆₀ fiber core chalcogenide glass ingot 6 and the selected extrusion mold 5 into the protective sleeve 4, and the As ₄₀ S ₆₀ core chalcogenide glass ingot 6 is stacked above the extrusion die 5, and then the protective sleeve 4 together with the As ₄₀ S ₆₀ core chalcogenide glass ingot 6 and the extrusion die 5 Place them together on the As ₃₉ Se ₆₁ clad chalcogenide glass ingot 7, and finally put the extrusion head 2 together with the first ejector rod 31 into the extrusion cylinder 1, so that the bottom surface of the first ejector rod 31 is in contact with the protective sleeve 4 contact with the top surface of the first push rod 31, the longitudinal through hole 41, the extrusion hole 51 on the extrusion die 5, and the center of the extrusion port 11 are on the same straight line;

(4) Heat the extrusion cylinder 1 until the temperature of the extrusion cylinder 1 reaches T, and the temperature T of the extrusion cylinder 1 satisfies: Tg<T<Tx, where Tg takes the value of As ₄₀ S ₆₀ fiber core sulfur system Glass and As ₃₉ Se ₆₁ cladding chalcogenide glass, the larger value of the transition temperature of these two glasses, Tx is taken from the two types of As ₄₀ S ₆₀ core chalcogenide glass and As ₃₉ Se ₆₁ cladding chalcogenide glass The smaller value of the crystallization temperature of the glass, specifically, the temperature T of the extrusion cylinder 1 is controlled at 200°C<T<210°C, and the As ₄₀ S ₆₀ core chalcogenide glass ingot 6 and The As ₃₉ Se ₆₁ clad chalcogenide glass ingot 7 is softened by heat; the top of the extrusion head 2 is pressed, and the first stage of extrusion starts. The schematic diagram of the state inside the extrusion cylinder before the first stage of extrusion is shown in Figure 1. An ejector pin 31 pushes the protective sleeve 4 together with the As ₄₀ S ₆₀ core chalcogenide glass ingot 6 and the extrusion die 5 to squeeze into the As ₃₉ Se ₆₁ cladding chalcogenide glass ingot 7, so that the bottom surface of the extrusion die 5 is in contact with the The bottom surface of the As ₃₉ Se ₆₁ clad chalcogenide glass ingot 7 is flush, at this moment the first stage of extrusion is completed, and the schematic diagram of the state inside the extrusion cylinder is shown in Figure 2;

(5) Keep the temperature T of the extrusion cylinder 1 constant, take out the extrusion head 2, disassemble the first ejector rod 31, and assemble the second ejector rod 32 equal in length to the first ejector rod 31 on the extrusion head 2, The outer diameter of the second push rod 32 is less than the aperture of the longitudinal through hole 41, and then the extrusion head 2 together with the second push rod 32 is put into the extrusion barrel 1, so that the bottom surface of the second push rod 32 is in contact with the protective sleeve 4 The top surface of the top of the extrusion head 2 is flushed, and the pressure is applied to the top of the extrusion head 2 again, and the second stage of extrusion starts, so that the bottom end of the second ejector rod 32 passes through the longitudinal through hole 41 and extends into the As ₄₀ S ₆₀ fiber core chalcogenide glass In the ingot 6, the As ₄₀ S ₆₀ core chalcogenide glass is extruded from the extrusion hole 51 on the extrusion die 5, and finally the As ₄₀ S ₆₀ core chalcogenide glass and the As ₃₉ Se ₆₁ cladding chalcogenide glass are extruded from The extrusion port 11 is extruded together, and the extruded product is the semi-finished product 8 of the elliptical core polarization-maintaining optical fiber preform. At the same time, the semi-finished product 8 is synchronously pulled by a traction mechanism. The second stage of extrusion is completed, and the second stage See Figure 3 for a schematic diagram of the state inside the extrusion barrel at the end of extrusion;

(6) After annealing the extruded elliptical-core polarization-maintaining optical fiber semi-finished product 8 at Tg temperature for 6 hours, and then slowly cooling down to room temperature, the single-mode chalcogenide elliptical-core polarization-maintaining optical fiber preform of Example 2 was obtained. Put the extruded elliptical-core polarization-maintaining optical fiber preform under a microscope to observe, it can be seen that the ellipticity of the fiber core is basically consistent with the ellipticity of the extrusion hole 51 on the corresponding extrusion die 5, and the fiber core is consistent with the As ₃₉ The Se ₆₁ cladding is very tightly bonded, the core-cladding interface is clear and complete, and there is no problem of poor core-cladding interface of the preform prepared by the traditional method. Polarized fiber preforms have high dimensional accuracy. The end view of the elliptical-core polarization-maintaining optical fiber preform prepared by extrusion in Example 2 is shown in FIG. 4 . In Fig. 4, 81 is a core glass, and 82 is a cladding glass.

Claims (3)

1. The extrusion preparation method of the elliptic core polarization-maintaining optical fiber preform with adjustable ellipticity arbitrarily, it is characterized in that comprising the following steps: (1) Prepare an extrusion cylinder with an upper opening, the bottom wall of the extrusion cylinder is provided with an extrusion port; prepare an extrusion head, the outer diameter of the extrusion head is the same as the diameter of the extrusion cylinder The inner diameter is suitable, the bottom of the extrusion head is provided with a cavity with a lower opening, the center of the cavity is provided with a first push rod, and the upper end of the first push rod is detachably connected and fixed On the described extrusion head, the bottom surface of the first push rod is flush with the bottom surface of the described extrusion head; prepare a protective sleeve with an opening at the bottom, and the center of the top wall of the protective sleeve is provided with A longitudinal through hole, the external dimensions of the protective sleeve are adapted to the cavity, and the outer diameter of the first ejector rod is greater than the diameter of the longitudinal through hole; prepare a set of extrusion dies, The set of extrusion dies is composed of a plurality of extrusion dies, and an elliptical extrusion hole is opened in the middle of each of the extrusion dies, and the ellipticity of the extrusion holes on each of the extrusion dies is not equal. , the outer diameter of each of the extrusion dies is adapted to the inner diameter of the protective sleeve; a core chalcogenide glass ingot and a cladding chalcogenide glass ingot rinsed with alcohol and dried are prepared, And the linear refractive index of the core chalcogenide glass is greater than that of the cladding chalcogenide glass, the outer diameter of the core chalcogenide glass ingot is adapted to the inner diameter of the protective sleeve, and the cladding The outer diameter of the layered chalcogenide glass ingot is adapted to the inner diameter of the extrusion cylinder; (2) According to the ellipticity of the core of the elliptical-core polarization-maintaining optical fiber preform to be prepared, an extrusion die matching the ellipticity of the extrusion hole is selected from the set of extrusion dies; (3) Put the cladding chalcogenide glass ingot into the bottom of the extrusion cylinder first, then put the core chalcogenide glass ingot and the selected extrusion mold into the protective sleeve , and make the core chalcogenide glass ingot stacked above the extrusion mold, and then place the protective sleeve together with the core chalcogenide glass ingot and the extrusion mold on the cladding sulfur on the glass ingot, and finally put the extrusion head together with the first ejector rod into the extrusion cylinder, so that the bottom surface of the first ejector rod and the protective sleeve The top surfaces are in contact, and the centers of the first ejector pin, the longitudinal through hole, the extrusion hole on the extrusion die and the extrusion port are on the same straight line; (4) Heat the extrusion barrel until the temperature of the extrusion barrel reaches T, and the temperature T of the extrusion barrel satisfies: Tg<T<Tx, where Tg takes the value of the core chalcogenide glass and the cladding The larger value of the transition temperature of the two glasses of chalcogenide glass, Tx is the smaller value of the crystallization temperature of the two glasses of the core chalcogenide glass and the cladding chalcogenide glass, after heating, squeeze the cylinder The inner core chalcogenide glass ingot and the cladding chalcogenide glass ingot are softened by heat; press the top of the extrusion head, and push the protective sleeve together with the core chalcogenide through the first ejector pin Extruding the glass ingot and the extrusion mold into the clad chalcogenide glass ingot together so that the bottom surface of the extrusion mold is flush with the bottom surface of the clad chalcogenide glass ingot; (5) Keep the temperature T of the extrusion barrel constant, take out the extrusion head, disassemble the first ejector pin, and assemble the second ejector pin with the same length as the first ejector pin on the On the extrusion head, the outer diameter of the second ejector rod is smaller than the aperture diameter of the longitudinal through hole, and then the extrusion head together with the second ejector rod is put into the extrusion barrel, Make the bottom surface of the second ejector rod flush with the top surface of the protective sleeve, apply pressure to the top of the extrusion head again, and make the bottom end of the second ejector rod pass through the The above longitudinal through hole extends into the core chalcogenide glass ingot, the core chalcogenide glass is extruded from the extrusion hole on the extrusion die, and finally the core chalcogenide glass and the cladding sulfur The glass is extruded together from the extrusion port, and the extruded product is a semi-finished product of an elliptical core polarization-maintaining optical fiber preform, and the semi-finished product is synchronously pulled by a traction mechanism during extrusion; (6) After annealing the extruded semi-finished elliptical-core polarization-maintaining optical fiber preform at the Tg temperature for 4-6 hours, and then slowly cooling down to room temperature, a single-mode chalcogenide elliptical-core polarization-maintaining optical fiber preform is obtained. 2. The extrusion preparation method of an elliptical core polarization-maintaining optical fiber preform whose ellipticity can be adjusted arbitrarily according to claim 1, characterized in that the extrusion process in step (4) and step (5) is carried out in a vacuum chamber Before extrusion, use a vacuum pump to evacuate the vacuum chamber. When the vacuum degree in the vacuum chamber is lower than 10 ^-2 Pa, add nitrogen or inert gas to the vacuum chamber to make the air pressure in the vacuum chamber the same as the external atmospheric pressure. 3. The extrusion preparation method of an elliptic core polarization-maintaining optical fiber preform whose ellipticity can be adjusted arbitrarily according to claim 1 is characterized in that the value of the ellipticity e of the extrusion holes on each of the extrusion dies The range is 0<e<∞.