JPH04132632A - Production of glass structure for light transmission, glass structure for light transmission and optical fiber - Google Patents

Abstract

PURPOSE:To obtain a glass structure of single mold for light transmission free from foams, striae, etc., by putting glass for clad having end faces subjected to specular processing and glass for core having end faces subjected to specular processing in an extrusion molding device, heating, and extrusion molding. CONSTITUTION:(A) A first glass member 21 consisting of glass for clad having both approximately parallel end faces and at least one end face subjected to abrasion processing and (B) a second glass member 3 having smaller outer diameter than that of the first glass member, both approximately parallel end faces and at least one end face subjected to abrasion processing are treated so as to make central axes of both the glass member coincident, the abrasion faces are mutually contacted, the face of the first glass member 21 at the opposite side of the contact face is positioned at a molding hole part 12, both the members are put in a storage part 11 of molding material, extrusion molded while heating to give a glass structure for light transmission having at least two layer structure of core and clad.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for manufacturing a glass structure for optical transmission such as an optical fiber preform or an optical waveguide, and a method for manufacturing a glass structure for optical transmission such as an optical fiber preform or an optical waveguide, and a method for manufacturing a glass structure for optical transmission such as an optical fiber preform or an optical waveguide. The present invention relates to a glass structure for light transmission and an optical fiber, and is particularly suitable for obtaining a single mode glass structure for light transmission and an optical fiber made of multi-component glass.

[Prior Art] One method of manufacturing an optical fiber is to create a relatively large-diameter preform consisting of a core and a cladding, and then draw this preform.

Further, a glass structure for optical transmission having substantially the same configuration as the preform is used as an embedded optical waveguide used in various optical circuits. Hereinafter, this preform and optical waveguide will be referred to as an optical transmission glass structure. In recent years, optical fibers or optical waveguides using multi-component oxide and non-oxide glasses are expected to find a variety of applications in various fields. For example, optical fibers for long-distance communications that take advantage of their low theoretical loss, temperature and chemical sensors that make use of their ability to transmit far-infrared light, or medium- to long-distance optical fibers that are obtained by doping the core with active ions. It is possible to obtain infrared laser media, optical amplifiers or high-efficiency ultra-compact solid-state laser devices that take advantage of their large optical signal amplification gain, fiber switching devices or wavelength conversion devices that take advantage of their large nonlinear optical effects, etc. is being attempted.

Now, when manufacturing optical transmission glass FTFI structures such as single-mode optical fiber preforms or optical waveguides using this multi-component glass, the multi-component glass is composed of multi-component materials with significantly different vapor madness. The vapor phase synthesis method (CV) is commonly used to manufacture single-mode preforms from quartz glass.
D method) is difficult to apply. For this reason, attempts have been made to manufacture a single-mode optical transmission glass structure using multi-component glass using the following method.

■ Built-in casting method In this method, first, glass melt for cladding is poured into a casting mold until it is full. Then, the glass melt begins to assimilate from its surroundings. Next, before the solidification spreads throughout, the casting mold is turned upside down, the glass melt in the center is discharged, and the core melt is poured into the center instead. After that, let the whole thing solidify. As a result, a glass structure for optical transmission consisting of a core and a cladding is obtained (see Japanese Patent Laid-Open No. 143508/1983). This method has been applied to non-oxide glasses that have a higher tendency to crystallize. In order to obtain a glass structure such as a single-mode preform with a high ratio of the cladding diameter to the core diameter using this method, it is necessary to set the initial assimilation time long so that the cladding portion becomes sufficiently thick.

■ Rotational casting method In this method, a small amount of glass melt for cladding is poured into a casting mold, the mold is rotated, and centrifugal force causes the glass melt to adhere and assimilate to the inner wall of the mold, forming a cylindrical cladding part. form. Next, the core glass melt is poured all at once into the cylindrical cladding and assimilated (see Japanese Patent Laid-Open No. 61-21174). This method has also been applied to non-oxide glasses that have a higher tendency to crystallize. In order to obtain a glass structure such as a single-mode preform using this method, it is necessary to thickly adhere and solidify the cladding glass to the inner wall of the mold.

■ Rod-in-tube method The cladding glass is processed into a tube shape, and a core glass rod having an outer diameter smaller than the inner diameter of the center hole is inserted into the center hole to form a preform or direct optical fiber. This is what you get. In order to obtain a single-mode glass structure using this method, it is necessary to reduce the inner diameter of the cladding glass tube and to correspondingly reduce the outer diameter of the core glass rod. Note that in order to manufacture an optical fiber from this preform, the preform is drawn while being heated.

■ Double crucible method: Using a double crucible consisting of an inner crucible that houses the glass melt for the core, and an outer crucible that surrounds this inner crucible and houses the glass melt for the cladding,
To solidify each glass melt by ejecting it simultaneously and continuously from a circular nozzle provided in the inner crucible and a ring nozzle of the outer crucible formed to surround this circular nozzle. Accordingly, a glass structure (preform or optical fiber) having a core-clad structure is obtained (see Japanese Patent Laid-Open No. 190741/1983).

[Problems to be Solved by the Invention] However, each of the above-mentioned methods has the following problems.

In both of these methods, the glass for the cladding and the glass for the core are cast into a mold in a low viscosity state (melt state), so bubbles and striae are likely to be mixed into the glass, and the glass may begin to solidify. To further cast the core glass melt on the clad glass in the
There is also the problem that the clad glass is reheated and cannot be crystallized. Furthermore, for example, if the cladding diameter is 5 to 50% of the core diameter,
In order to obtain a glass structure for a single mode with a magnification of 10 times, it is necessary to drain the glass melt in the center immediately before the entire clad glass solidifies (in the case of Building I hayne casting method), or to remove the core glass in the center. (in the case of the rotational casting method), but since the timing of this process varies greatly depending on slight differences in conditions, setting this timing is almost always dependent on experience and intuition. Furthermore, if this timing is inappropriate, there is a high possibility that the obtained glass structure will not have the performance necessary for single mode use.

Rod-in-tube: In this method, clad glass is formed into a tube shape,
In addition to forming the core glass into a rod shape, it is necessary to cut and polish the inner and outer circumferential surfaces of these to a specified surface precision, but in general, polishing the inner circumferential surface of the tube and the outer circumferential surface of the rod is Even when the inner diameter of the tube and the outer diameter of the rod are relatively large, as in the case of multimode glass structures, it is significantly more difficult than polishing a flat surface.
Surface accuracy also decreases. However, in the case of a single-mode glass structure, the inner diameter of the tube and the outer diameter of the rod are significantly smaller. Therefore, it is extremely difficult to finish the surface with the necessary surface precision to obtain a single-mode glass structure with the desired performance, and it is also difficult to drill a hole with a small inner diameter in the cladding tube. It is extremely difficult. Therefore, it is difficult to obtain a single-mode glass structure with a predetermined performance using this method.

Dual J-Bi Insertion Method This method requires the viscosity of the glass melt to be set low in order to continuously jet the glass melt from the nozzle.
As a result, it is difficult to maintain the ratio of the core glass to the cladding glass precisely at a predetermined ratio while maintaining it large enough to be suitable for a single-mode glass structure, and it is also difficult to accurately control the temperature of both during assimilation. is difficult to maintain at a given temperature. Moreover, there is a risk of contamination with impurities from the crucible. Therefore, it is difficult to obtain a single-mode glass structure with predetermined performance using this method.

Furthermore, by first using an extrusion molding method, the applicant has been able to obtain a long multi-component glass preform that is free of bubbles, striae, and crystals and has a good core-cladding interface. Please suggest a possible method (Patent Application Hei 1-254)
(Refer to Book No. 848, Mei #I). In this proposed method,
Although it is possible to increase the ratio of the cladding diameter to the core diameter to some extent by reducing the thickness of the core glass set in the extrusion molding device, it has been difficult to obtain the ratio necessary for single mode use. A possible method for increasing the above ratio using this method is to make the diameter of the core glass set in the extrusion molding device smaller than the diameter of the cladding glass. However, with that method,
The glass for the core is embedded in the glass for the cladding and then extrusion molding is performed, but at that time, bubbles etc. tend to get caught in the boundary between the peripheral side of the glass for the core and the glass for the cladding. Since the polishing accuracy of the peripheral side of the glass is inferior to that of flat polishing, it has not been possible to make the condition of the core-cladding interface sufficiently good for single mode use.

The present invention was made against the above-mentioned background, and provides a single mode optical transmission glass structure with excellent performance and a method for manufacturing the optical transmission glass structure capable of producing an optical fiber. The purpose is to provide a glass structure for light transmission and an optical fiber.

[Means for Solving the Problems] The present invention solves the above problems by having the following configurations.

(1) Glass for cladding and glass for core, both end surfaces of which are formed substantially parallel to each other, are sequentially stacked and accommodated in the molding material accommodating portion of an extrusion molding device, and extrusion molded while heating. Glass structure for optical transmission having a two-layer structure of cladding]-2 In a method for manufacturing an optical transmission glass structure for obtaining a structure, the glass structure is made of glass for cladding, both end surfaces are formed substantially parallel, and at least a first glass member having one end surface polished; a columnar core glass having an outer diameter equal to or less than the outer diameter of the first glass member;
A second glass member having at least a two-layer cladding structure and having both end faces substantially parallel to each other and having at least one end face polished is prepared; The polished surfaces of the two glass members are brought into contact with each other with their central axes substantially common, and the surface of the first glass member opposite to this contact surface is located in the molding hole of the extrusion molding device. A configuration characterized in that a glass member and a second glass member are housed in a molding material storage section of an extrusion molding device, and extrusion molding is performed while heating.

(2) Manufacture of the glass structure for optical transmission according to claim (1)]
3. In the molding method, the second glass member stores a cladding glass and a core glass, each of which has both end surfaces substantially parallel to each other, in a stacked manner in a molding material storage section of an extrusion molding device, and heats the glass. It is characterized in that it is manufactured using a method for manufacturing an optical transmission glass structure, in which an optical transmission glass 'MIJ structure having at least a two-layer structure of a core and a cladding is obtained by extrusion molding. A method for manufacturing a glass structure for optical transmission.

(3) A light transmission glass structure having at least a two-layer structure of a columnar core glass and a clad glass surrounding the core glass, wherein the light transmission glass structure according to either structure (1) or (2) A configuration characterized in that it is manufactured using a method for manufacturing a transmission glass structure.

(4) An optical fiber having at least a two-layer structure of a columnar core glass and a clad glass surrounding the core glass, the optical transmission glass structure according to either structure (1) or (2). 1. A structure characterized in that the structure is manufactured by using a preform as a light transmission glass structure manufactured using a method for manufacturing a glass structure, and drawing the preform.

[Operation] According to the above configuration (1), by making the outer diameter of the second glass member smaller than the outer diameter of the first glass member, the ratio of the cladding diameter to the core diameter can be adjusted to a preform for single mode. can be increased to a degree suitable for glass structures such as However, in this case, by using a second glass member in which the core-clad interface in the glass member is in good condition with no bubbles, etc., the core-clad formed after extrusion molding can be improved. The boundary surface can be in good condition without bubbles or the like. After extrusion, the core of this second glass member
This is because the cladding interface directly forms the core-cladding interface of the glass structure of the molded product. Therefore, by the conventional method, it is possible to obtain a core-clad interface in good condition without bubbles or the like. In this case, as described in configuration (2), if a method using extrusion molding is used to obtain the second glass member, it is possible to obtain one with an extremely good boundary surface, and the configuration An optical transmission glass structure having the configuration described in (3) and having desired characteristics can be obtained. Moreover, according to configuration (4), an optical fiber with desired characteristics can be obtained.

[Example] FIGS. 1 and 2 are diagrams for explaining a method of manufacturing a light transmission glass structure according to an example of the present invention. Hereinafter, one embodiment will be described in detail with reference to these drawings.

First, the main points of the method of this embodiment are as follows.

(a) Manufacture the first glass member.

(Opening) Manufacture the second glass member.

(c) Heat-sealing the polished surface of the first glass member to the polished surface of the second glass member. Note that this step can also be omitted.

(d) Put the heat-fused first glass member and second glass member into an extrusion molding device and extrude them under a predetermined temperature and atmosphere, cut out a predetermined portion of the obtained molded product, and transmit light. Obtain a glass structure for use.

Each step will be explained in detail below.

(a) Manufacturing of the first glass member This first glass member 21 (see FIG. 1) constitutes a part of the cladding portion when the optical transmission glass structure is completed.

A predetermined amount (about several tens of grams) of a batch obtained by weighing and mixing multi-component fluoride raw materials at a predetermined mixing ratio is placed in a crucible made of carbon or the like and heated at a predetermined temperature (for example, 950°C) and a predetermined atmosphere ( For example, by heating for a predetermined time (several hours) in an inert gas atmosphere (inert gas atmosphere) to melt and then slowly cooling to obtain a disk-shaped first glass member 21 with an outer diameter of several tens of meters and a thickness of several tens of mm. . Note that the first glass member 21 has a refractive index that is equal to the core glass portion 32a of the second glass member 3 (see FIG. 3), which will be described later.
It is slightly smaller than the core glass 32a of the second glass member 3, and the viscosity at the temperature (for example, 400°C) during extrusion molding described later is almost the same as that of the core glass 32a of the second glass member 3 (]-〇 ~ 1010
poise, preferably about 10 7 to 10 9 poise).

Note that this first glass member 2]- is a thin (for example, about 10 ml) disk-shaped clad glass piece (2
1a, 21b, 21c, 21d) using the same method as described above, and after precisely polishing them so that both end surfaces are parallel, stacking them together to create a shape of several tens of mm.
It may be made as thick as .

According to this, high-quality glass can be obtained relatively easily, and both end faces can be easily polished. FIG. 1 (a) shows this case.

(B) Manufacturing of the second glass member This second glass member 3 (see Fig. 3) has a core clad structure and has an outer diameter equal to or less than the outer diameter of the first glass member 21 described above, and is completed when completed. It constitutes a part of the cladding part and a core part of the optical transmission glass structure to be described later. Further, the glass constituting the cladding portion 31a of the second glass member 3 is the same as that of the first glass member 21 described above. It is the same glass as the glass that makes up the glass.

This second glass member 3 is manufactured by the preform manufacturing method using the conventional extrusion method described above (Japanese Patent Application No. 1-25
4846)). A detailed description will be given below with reference to FIGS. 1 and 2.

In FIGS. 1 and 2, reference numeral 1 indicates an extrusion molding device;
Reference numeral 11 is a cylindrical molding material storage part (with an inner diameter of several tens of mm); 2 is a circular hole (with an inner diameter of several mm); 13 is an extrusion punch; 31 is glass for cladding;
Reference numeral 32 is glass for the core.

First, the cladding glass 31 is manufactured. This cladding glass has the same structure as the first glass member 21 described above, and therefore is manufactured by the same method as the first glass member 21 described above. In FIG. 2, this cladding glass 31 is divided into four thin cladding glass pieces 3.
1a, , 31b, 31c, 3]-d, and the two end faces are polished and overlapped.

Next, core glass 32 is manufactured. This core glass 32 has a composition different from the above-mentioned cladding glass 31-, and has a refractive index slightly larger than that of this cladding glass 31-, but the viscosity at the temperature during extrusion molding is lower than that of the cladding glass 31-. ] (-first glass member). Note that the outer diameter is the same as that of the cladding glass 31, but the thickness is made thinner than that of the cladding glass 31.9 In this case, by selecting the ratio of the thickness of the cladding glass to the thickness of the core glass, The ratio of the cladding diameter to the core diameter of the glass structure obtained after extrusion can be selected to a certain extent.

This core glass 32 is manufactured by the same method as the method for manufacturing the first glass member 21 described above, except that the composition of the glass is changed.

Next, the clad glass 31 and the core glass 32 thus obtained are stacked one on top of the other and stored in the molding material storage section 11 of the extrusion molding device 1, as shown in FIG. 2(a). do. In this case, one end surface of the clad glass is located on the forming hole 12 side, and one end surface of the core glass 32 is in contact with the extrusion surface 13a of the extrusion punch ]-3.

Further, when stacking these, it is preferable to completely remove gaps at the interface and scratches on the glass surface so that the mutual contact surfaces form optical contact. Then,
This extrusion molding apparatus 1 is heated and maintained at several hundred degrees Celsius so that the viscosity of both the cladding glass 31 and the core glass 32 is about 107 to 109 poise, as shown in FIG. 2(b). , pressure P(
(approximately several tens of bar) and extrusion molding. As a result, the cladding glass 31 and the core glass 32 are extruded together from the molding hole 12, cooled and solidified, and have a total length IJ1 and a diameter rl (hole diameter ro of the molding hole 7.0).
mm, a rod-shaped molded body 30 with rl =7.3 mm (around 7.3 mm) is obtained. This rod-shaped molded body 30 has a distance of 92 (total length, Q
When i = 1000 mm, the molding device 1. The part located on the side has a two-layer structure of core and cladding, and from this distance g2 there is a distance of 113 (Q 3
= 50mm inward/outward)/from the point to the molding device 1-
In the part located on the side, the core diameter (r2) is approximately 2 to 3 mm.
It becomes. Therefore, from this 93 to the molding hole]-2 area and the core diameter is a predetermined value (r2 = 2 mm inside and outside).
The second crow member 3 is obtained by cutting out a portion having a predetermined thickness (tl = 2 mm or less) and precisely polishing it so that both end surfaces are parallel. FIG. 3 is a perspective view of the second glass member 3 thus obtained.

(c) Heat fusion Next, the first glass member 21 and the second glass member 3 obtained in the above steps are heat fused.

This thermal fusion is performed by bonding one end surface of the second glass member 3 and any one of the clad glass pieces of the second glass member 21, for example, one end surface of the clad glass piece 21d, so that their central axes are common to each other. and heated to several hundred degrees Celsius (for example, 390 degrees Celsius) in an inert gas atmosphere such as argon gas, and for ten minutes (for example, 10 minutes) under a load of several hundred grams.
This is done by holding.

Note that this step is not necessarily necessary in the present invention, and is one of the preferred embodiments of the present invention. That is,
In the present invention, the extrusion molding step described below may be carried out without heat-sealing and in a state of slight contact.

(d) Extrusion Next, as shown in FIG. 1 (a, accommodate. In this case, the end surface of the second glass member 3 on the side that is not thermally fused is the extrusion surface 13a of the extrusion punch 13 of the extrusion molding device.
so that it is in contact with

Next, this extrusion molding apparatus 1 is heated and maintained at several hundred degrees Celsius so that the viscosity of both the cladding glass 31 and the core glass 32 is about 1.0 to 109 poise, and as shown in FIG. 1(b). As shown, extrusion molding is performed by applying a pressure P (approximately several + I) to the extrusion punch 13. As a result, from the molding hole 12 to the first glass member 3
and the second glass member 21 are extruded together, cooled and solidified, and the entire length is increased! J4, diameter r3 (when the hole diameter of the molding hole rO = 7.0 mm, r3 = 7.3 mm inside and outside)
A rod-shaped molded body 300 is obtained. This rod-shaped molded body 300
is the distance (5 (total length (J 4 = 850 mm), (J 5
The part located on the molding device 1 side from 650 mm (inner and outer) has a two-layer structure of core and cladding.
In the part located above the forming apparatus from a point further moved from distance 〃5 to the forming apparatus 1 side by a distance of 96 (β6 = 20 mm or less), the core diameter (r4) is almost constant (r4 m0.2 mm inside and outside).

Therefore, by cutting out a region from a portion where the core diameter is approximately constant to the molding hole portion 12, an optical transmission glass structure 33 having a length of 11 (r1 = 130 mm inside and outside) can be obtained. . FIG. 3 is a perspective view of the optical transmission glass plate 33 obtained in this manner. This optical transmission glass structure 33 has a core diameter that is extremely small compared to the overall diameter, and has no bubbles or striae, so it can be used as a preform for a single-mode optical fiber or as an embedded optical waveguide. I can do it. Further, for example, if a core glass portion 32a of the second glass member 3 containing a laser active substance is used, an optical waveguide type laser medium can be obtained.

In addition, by cutting out a part of the optical transmission glass '1M structure obtained in this way to a thickness of several mm, using this as the second glass member 3, and further extruding it (step c), it is possible to A light transmission glass structure with a small core diameter can be obtained.

In order to manufacture a single mode optical fiber using this optical transmission glass structure as a preform, this preform is drawn using a fiber drawing device. In this drawing, for example, the preform is sent to a heating section in a heating furnace at a predetermined rod feeding speed, heated and fused, and then drawn at a predetermined fiber drawing speed. in this case,
For example, the drawing temperature should be around 460℃, and the drawing speed should be several meters.
/mn, an optical fiber with an outer diameter of several μm and a core diameter of several μm can be obtained.

It has been confirmed that the optical fiber obtained by such G-filtering exhibits single-mode transmission in a predetermined wavelength region, and has significantly lower transmission loss than optical fiber manufactured by conventional manufacturing methods.

In addition, in the above-mentioned embodiment, non-oxidizing! T'l! I gave an example using multi-component glass, but ordinary optical glass may also be used, and in this case too, a single-mode optical transmission glass structure manufactured by a conventional method and an optical It has been confirmed that performance superior to that of fiber can be obtained.

The inventors of the present application actually manufactured a 1-meter optical transmission glass structure and an optical fiber using the method of the above-mentioned embodiment, and some of the manufacturing examples are listed below.

Mouse genes (A) 1st - Production of glass member (21) AlF3, Z
rF4, YF3, MgF2, CaF2, SrF
2, BaF2, NaF and NaC1, the glass composition (mo1% display), A I F3 is 30
%, ZrF4 10%, YF3 6%, MgF2 4%
, CaF2 20%, SrF2 13%, BaF2 8
%, NaF: 3%, and NaCl: 6%. 50 g of the resulting batch was placed in a carbon crucible, and heated at 950° C. for 2 hours in an argon atmosphere.
Do not heat or melt. After that, the molten glass liquid was heated to 370°C.
35mm 1φ×10
mm disc-shaped glass (clad glass piece 2), a
.

21b, 21c, 21d) Good value. The refractive index of this glass is 1.438 for light with a wavelength of 1.9 μm.

Then, the same operation was repeated four times to obtain a total of four disc-shaped glasses. Thereafter, precision polishing was performed so that both surfaces were parallel to each other.

(b) Production of second glass member (3) First, four clad glass pieces (31a
, 31b, 31c, and 31d), and these were combined to form a cladding glass (31).

Next, AI F3, ZrF4, YF3, MgF2
, CaF2, SrF2, BaF2, and NaC1, the glass composition (indicated by mo1%) is 25% AlF3, 13% ZrF4, 1]-% YF3, MgF
2 is 4%, CaF2 is 15%, SrF2 is 14%, Ba
15 g of a batch obtained by weighing and mixing F2 to 12% and Na and C to 16% was placed in a carbon crucible and melted by heating at 950° C. for 2 hours in an argon atmosphere. Thereafter, the molten glass liquid was rapidly heated to 370°C and then slowly cooled to obtain a glass disc having a diameter of 35 mm and a diameter of 3 mm. The refractive index of this glass is 1.9 for the wavelength
It was 1.456 for μm light. Next, this disk-shaped glass was precisely polished until both end surfaces became parallel and the thickness became 2 mm to obtain a core glass (32).

Both the cladding glass (31) and core glass (32) thus obtained had a viscosity of about 108 poise at 400°C.

Next, the molding material storage section (11) of the extrusion molding device (1) is
) with four clad glass pieces (31a) inside.

31b, 31c, 31d) for cladding (
(See Figure 2). In this case, one end surface of the cladding glass (31) in contact with the outside was positioned on the molding hole (12) side.

Next, one end surface of the core glass (32) is brought into contact with the other end surface of the cladding glass (31), and the two are brought into optical contact so that their central axes are common. In this case, the hole diameter of the molded hole (12) is set to 7 mm.
It was set as φ.

Thereafter, this extrusion molding device (1) was heated to 400°C, and extrusion molding was performed by applying a pressure of 50 ba, r to the extrusion punch (13).

As a result, from the molding hole (12), a rod-shaped molded body (30
)was gotten. 80 mm from the tip of this rod-shaped molded body (30)
The core glass penetrated from a point located at 0 mm, and the core diameter was about 3 to 2 mm at about 50 mm beyond this point. Therefore, this rod-shaped molded body (30) was cut out to a thickness of 2 mm at a core diameter of 2 mm, and the bottom surface was polished while paying attention to the parallel accuracy.
A second glass member (3) having a two-layer cladding structure was obtained.

(c) Heat fusion Next, one end surface of the second glass member (3) manufactured in step (a) is attached to the first glass member (21) manufactured in step (b).
The clad glass piece (2]-d) was brought into contact with one end surface of the clad glass piece (2]-d), and the two pieces were optically contacted so that their central axes were common.
After applying a load of 0.00 g, the material was thermally fused by slowly cooling it to room temperature.

(d) After extrusion molding, the first glass member (21) and the second glass member (
3) were stacked one on top of the other and stored in the molding material storage section (11) of the extrusion molding device (1). In this case, the end surface of the second glass member (3) on the side that was not thermally fused was in contact with the extrusion surface (13a) of the extrusion punch (13) of the extrusion molding device 1.

Next, this extrusion molding apparatus (1) was heated and maintained at 400° C., and extrusion molding was performed by applying a pressure of 50 ba, r to the extrusion punch (13). As a result, the first glass member (3) and the second glass member (21) are integrally extruded from the molding hole (12), cooled and solidified, and the total length is 850 m.
n1 (=Il 4 > , diameter 7.3 mm (-r3
) A rod-shaped molded body (300) was obtained. This rod-shaped molded body (300) has a two-layer structure of a core and cladding at a distance of 650 mm (==Q5) from its tip toward the extrusion molding device (1) and toward the molding device (1). The core diameter (r4〉) is 0.0 mm in the part located on the forming apparatus (1) side from a point further moved from this part to the forming apparatus (1) side by a distance of 20 mm (-96).
It remained constant at 2 mm. Therefore, when we cut out the area from the area where the core diameter is constant to the molding hole (13), we found that it had a length of 130 mm (,
The optical transmission glass structure (33) of Q) was obtained.

Now, apply Teflon F to the preform created as above.
When heat-shrinkable EP (trade name of DuPont) was coated, heated to 460°C, and drawn at a drawing speed of 7 m/min, approximately 90 m of optical fiber with an outer diameter of 230 μm and a core diameter of 6.3 μm was obtained. It was done.

The roundness of the core portion was extremely good, and the roundness and core diameter were maintained in the longitudinal direction of the fiber.

The transmission loss of this fiber is approximately 0.0 at 2.94 μm.
It was 1 dB/m. Also, the wavelength is 1.6 to 1.9 μm.
An increase in loss due to higher-order mode cutoff was observed over
It was found that the fiber was in a single mode at wavelengths of 1.9 μm or more (normalized frequency V-2, 39). In addition, when a preform was made using the built-in casting method using a combination of glasses with the same composition as above and an attempt was made to make it into a fiber, crystals precipitated at the core-clad interface, and the transmission loss of the resulting fiber was also 3 dB/m. It was big.

Remarks: This manufacturing example is an example in which an optical waveguide type laser medium is manufactured. This production example is basically the same as the process of Production Example 1 above, but in order to make it into a laser medium, a laser active substance is included in the core glass part (32a) of the second glass member. Therefore, the composition, thickness, heating conditions, etc. of the second glass member and the first glass member are slightly different.

Furthermore, in order to reduce the core diameter, a second glass member (
To obtain 3), perform the extrusion process twice. Only this difference will be explained below.

(A) First Glass Member Manufacturing Example 1 The only difference is the composition, refractive index, and thickness, and the other things are the same.

*Composition of the first glass member (21) (displayed as mo1%) Al
F2...25% ZrF4...13% YF3...11% MgF2...4% CaF2...15% SrF2・...14% BaF2...12% NaC1...6% *Refractive index: 1.448 for light with a wavelength of 2.7 μm *Thickness of 10 mm is 1 I used one.

(b) Second glass member Core glass for forming the second glass member (3) (
The composition and thickness of 32), the composition and thickness of cladding glass (31), and the fact that the extrusion molding process is performed twice are as follows:
This is different from Production Example 1.

*Composition of core glass (32) (mo1% display) A I
F3...25% ZrF4...13% ErF3...10% (laser active substance) YF3
...... 1% MgF2... 4% CaF2...15% SrF2...14% BaF2...12% NaC1... ...6% *Refractive index of core glass (32) 1.454 for light with a wavelength of 2.7μη] The composition and refractive index of cladding glass (31) are
2], Same as in ) Now, using these core glass (32) and cladding glass (31), the same process as the second glass member (3) in Manufacturing Example Co.
Outer diameter (rl) is 7.3mm, core diameter (F2) is 0.2m
A disk body having a thickness (tl) of 1.5 mm (in Manufacturing Example 1, this disk body was used as the second glass member) was manufactured.

Next, this disk body was used as the second glass member of Production Example 1, and on the other hand, two pieces of glass similar to the cladding glass pieces (21a, etc.) of the above-mentioned cladding glass were cut out and used as cladding glass. Glass thickness: 10mm
X2>, extrusion molding was performed again. In this case, fl of the molded body corresponding to the rod-shaped molded body (300) in FIG.
4 = 350 mm1.115 = 100 mm, ρ
6 = 20 mm, F4 (core diameter) - 22 μm. Furthermore, a part of this rod-shaped molded body 300) was added to 1.
Cut it out to a thickness of 5 mm and attach it to the second glass member (3
).

(c) Heat fusion The first glass member (thickness: 10 m) obtained in each of the above steps.
mX]-sheet) and a second glass member (thickness 1.5 mm) were heat-sealed by the same method as in Production Example 1- above.

(d) Extrusion molding The heat-sealed first glass member and second glass member are extrusion molded in the same manner as the extrusion molding process in [Manufacturing Example].

As a result, a rod-shaped glass molded body with a diameter of 7.3 mm and a length of 250 mm was obtained. The core glass began to penetrate from a position 50 mm from the tip of this molded body. Also,
Approximately 20 mm ahead of this position, the core diameter was approximately constant, and the diameter was 8 μm (normalized frequency V = 1.23). From the molded body thus obtained, a 20 mm portion with a substantially constant core diameter was cut out.
After polishing both end faces and vapor-depositing mirrors, a semiconductor laser beam with a wavelength of 0.8 μm was focused by a lens and incident on the core part. Laser light oscillation was observed. This oscillation efficiency was 9% in terms of slope efficiency.

In addition, when a preform was produced using the built-in casting method using a combination of glasses with the same composition as above, crystals were precipitated at the core-clad interface. In order to make the core diameter of this preform the same as that of the laser medium obtained above, the transmission loss of the fiber obtained by fiberization was also 5d.
It grew to b/m. When an oscillation experiment was conducted using a fiber having the same core diameter and length as above, the oscillation efficiency was 5% in terms of slope efficiency.

In this manufacturing example, an optical fiber was manufactured using ordinary optical glass.

(a) Manufacturing of the first glass member Optical glass F2 (refractive index at wavelength 0.6328 μm = 1.61655), diameter 35 mm, thickness 20 mm
A first glass member was obtained by processing the glass into a cylindrical shape and precision polishing with an area degree of λ/2 so that both end faces were parallel.

(b) Production of the second glass member Optical glass F7 (refractive index -1,62178 at wavelength 0.6328 μm) is processed into a cylinder shape with a diameter of 35 mmφ and a thickness of 1 mm, and the two end faces are parallel to each other by λ/ It was precision polished to a surface accuracy of 2 and made into core glass.

The viscosity of this glass is approximately 108 poise at 510°C.

On the other hand, the optical glass F2 has a diameter of 35 mm and a thickness of 40 m.
It is machined into a cylindrical shape of m, and the end faces are parallel to each other with λ
Precision polished to a surface accuracy of /2 and used as cladding glass.

The viscosity of this glass is also about 1-08 poise at 510°C.

Next, these processed optical glasses F7 and F2 are subjected to optical contact I in a class 100 clean room.
-L. Then, these were extruded using an extrusion molding device (1) at a pressure of 50 bar while heating at 510°C in the same manner as in each of the above production examples.

As a result, the diameter (clad diameter) is 7.3 mmφ, and the length is 95 mm.
A rod-shaped molded body of 0 mm was obtained. 60mm from the tip of this molded body
The core glass penetrates from a point located at 0 mm, and the core diameter is approximately constant at 2 m from about 50 mm ahead of this point.
It was m. The molded body thus obtained was cut out to a thickness of 1 mm at a core diameter of 2 mm, and both end faces were polished to an area of λ/2, resulting in a size of 7.3 mmφ x 1 m.
A second glass member of m was obtained.

(c) Heat fusion Next, the first glass member and the second glass part were pasted together so that their central axes were the same, and optical contact was made in a class 100 clean room. Then, it is fused in air at 510°C and slowly cooled to room temperature.

(d) Extrusion molding After that, the fused first glass member and second glass member are heated to 51°C using an extrusion molding machine in the same manner as described above.
Extrusion was carried out at 0°C and 50 bar pressure.

As a result, a rod-shaped molded body with a diameter of 7.3 mm and a length of 850 mm was obtained. The core glass began to penetrate from three positions 550 mm from the tip of this molded body.

The core diameter was approximately constant at a location approximately 20 mm beyond this position, and the size was 0.2 mm in diameter.

As a result, an effective length of about 100 mm was obtained as a preform for a single mode optical fiber.

Now, when the preform produced as described above was heated to 580°C and drawn at a drawing speed of 10 m/min, a fiber with an outer diameter of 125 μm and a core diameter of 3.4 μm was obtained by approximately 3.
00 m obtained. The roundness of the core portion was extremely good, and the roundness and core diameter were well maintained in the longitudinal direction of the fiber. The transmission loss of this fiber is 0.6328μ at wavelength
It was about 0.1 dB/m at m light. Also, at a wavelength of 0.6328 μm, the fiber has a normalized frequency of V=2
．． 200 was observed to be unimodal.

When single mode optical fibers with the same F7 and F2 core clad structures and the same core diameter were fabricated by the rod-in-tube method, the transmission loss was 1 dB/m. .

Manufacturing Example 4 In this manufacturing example, a laser fiber was manufactured using phosphate-based laser glass.

(a) First glass member phosphate-based laser glass LHG-8 (trade name of HOYA Corporation) glass with Nd doping amount of 0 wt% (
This will hereinafter be referred to as LHG-8CL.

The refractive index for a wavelength of 0.8 μm is 1.526. The first glass member is processed into a cylindrical shape with a diameter of 35 mm and a thickness of 20 mm, and precision polished to an area of λ/2 so that both end surfaces are parallel. I got it.

(b) Production of second glass member LHG-8CL was processed into a cylindrical shape with a diameter of 35 mm and a thickness of 2 mm, and both end faces of the LHG-8CL were precision polished to a surface accuracy of λ/2 to obtain a cladding glass.

On the other hand, a glass in which the Nd doping amount of LHG-8 was 3 wt% (hereinafter this glass will be referred to as L I-I G-8CO. The refractive index at a wavelength of 0.8 μm is 1.528) was made into a glass with a diameter of 35 mm and a thickness of 40 mm. It was machined into a cylindrical shape, and its both end faces were precisely polished with an area degree of λ/2.

The viscosities of both LHC, -8CL and LHG-8CO at 580°C are approximately ]-08 poise.

Next, L HG -8CO and I-I-I G-8CI-
Optical contact was carried out in a class 100 clean room. Then, these were extruded using an extrusion molding device at a temperature of 580° C. and a pressure of 50 bar. As a result, the diameter (clad diameter) is 7.3 mmφ and the length is 10
A rod-shaped molded body of 00 mm was obtained. 8 from the tip of this molded body
The core glass penetrates from a place located at 50mm,
Approximately 50mm beyond this point, the core diameter is approximately constant at 2mm.
It became. The molded body thus obtained is cut to a thickness of 1 mm at a core diameter of 2 mrr+, and both end surfaces thereof are polished to a surface precision of λ/2 to obtain a second glass member.

(C) Heat fusion Next, the first glass member and the second glass member are pasted together so that their central axes are the same, and optical contact is made in a class 100 clean room.Next, in air at 590°C The mixture was fused and slowly cooled to room temperature.

(d) Extrusion molding After that, the fused first glass member and second glass member are heated to 58°C using an extrusion molding machine in the same manner as described above.
Extrusion molding was carried out at 0° C. and a pressure of 50 bar.

As a result, a molded body with a diameter of 7.3 mm and a length of 850 mm was obtained. The core glass began to penetrate from a position 550 mm from the tip of this molded body.

Approximately 20 mm ahead of this position, the core diameter was approximately constant, and the size was 0.2 mmφ. Therefore, an effective length of about 100 mm was obtained as a preform for single mode fiber.

Now, when the preform produced as described above was heated to 580°C and drawn at a drawing speed of 10 m/min,
Approximately 30 fibers with an outer diameter of 125 μm and a core diameter of 4.0 μm
0 m obtained. The roundness of the core portion was extremely good, and the roundness and core diameter were maintained in the longitudinal direction of the fiber.

The transmission loss of this fiber was approximately 1 dB/m at a wavelength of 1.3 μm and 2 dB/m at a wavelength of 0.8 μm. A 10 mm long fiber was taken, both end faces were polished, mirrors were deposited on the core, and a wavelength of 0.8 μm was applied to the core.
m semiconductor laser light was input (normalized frequency ■2.
30) However, laser oscillation with a wavelength of 1.3 μm (normalized frequency V=1.41) was observed, and the oscillation efficiency was 2.4% in terms of slope efficiency.

When a laser fiber with the same core diameter was fabricated by the rod-in-tube method using the same glass as above, the transmission loss was 10 dB/m (wavelength 1.3 μm), and the oscillation efficiency was also 0 in terms of slope efficiency. .255%
Met.

Atsushi Kiyaku 5 This production example is almost the same as Production Example 3 described above, except that the thickness of the optical glass F2 constituting the cladding glass of the second glass member in Production Example 3 is 20 mm ( (In Production Example 3, this is 40 mm.) As a result, the rod-shaped molded product obtained after extrusion has a diameter of 7.3 mm, a length of 850 mm, and a distance of 350 mm from the tip.
The core glass had begun to penetrate from where it was located.

The core diameter was approximately constant approximately 15 mm ahead of this position, and the diameter was 0.4 mm. Therefore, a preform with an effective length of about 480 mm was obtained.

Now, when the preform produced as described above was heated to 580°C and drawn at a drawing speed of 10 m/min,
Approximately 1200 m of small-core fiber with an outer diameter of 125 μm and a core diameter of 7 μm was obtained. The roundness of the core portion was extremely good, and the roundness and core diameter were maintained in the longitudinal direction of the fiber. The transmission loss of this fiber is 0.6328μm
It was approximately 0.06 dB/m.

In addition, when optical fibers with the same F7 and F2 core clad structures and the same core diameter were manufactured using the rod-in-tube method, the transmission loss was 0.5 dB/m, so the effect of this manufacturing example is it is obvious.

[Effects of the Invention] As detailed above, the present invention has a first glass member constituting a cladding, and a second glass member having an outer diameter equal to or smaller than the first glass member and having a two-layer structure of a core and a cladding. By extruding the two glass members with their polished surfaces in contact with each other, after extrusion molding, the core-cladding interface of the second glass member remains the same as that of the core-cladding of the glass structure of the molded product. By forming an interface, it is possible to relatively easily obtain a single-mode optical transmission glass structure with a high core-clad ratio without bubbles at the core-clad interface. This is what I did.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining a method of manufacturing a glass structure for optical transmission according to an embodiment of the present invention, FIG. 3 is a perspective view of a second glass member, and FIG. 4 is an example of an embodiment of the present invention. FIG. 2 is a perspective view of a light transmission glass structure manufactured by an example method. 1... Extrusion molding device, 3... Second glass member, 1
DESCRIPTION OF SYMBOLS 1... Molding material storage part, 12... Molding hole part, 21.
...First glass member.

Claims (4)

[Claims] (1) Glass for cladding and glass for core, both end surfaces of which are formed substantially parallel to each other, are sequentially stacked and accommodated in the molding material accommodating portion of an extrusion molding device, and extrusion molded while heating. In a method for manufacturing an optical transmission glass structure for obtaining an optical transmission glass structure having a two-layer cladding structure, the optical transmission glass structure is made of cladding glass, both end surfaces are formed substantially parallel, and at least one end surface is polished. A first glass member that has been processed, and a columnar core glass having an outer diameter equal to or less than the outer diameter of the first glass member, the periphery of which is covered with a cladding glass to form a core.
A second glass member having at least a two-layer cladding structure and having both end faces substantially parallel to each other and having at least one end face polished is prepared; The polished surfaces of the two glass members are brought into contact with each other with their central axes substantially common, and the surface of the first glass member opposite to this contact surface is located in the molding hole of the extrusion molding device. 1. A method of manufacturing a glass structure for optical transmission, comprising storing a glass member and a second glass member in a molding material storage part of an extrusion molding device, and performing extrusion molding while heating. (2) In the method of manufacturing a glass structure for optical transmission according to claim (1), the second glass member is a cladding member having both end surfaces substantially parallel to each other formed in a molding material storage part of an extrusion molding device. A method for producing a glass structure for optical transmission, in which a glass structure for optical transmission having at least a two-layer structure of a core and a cladding is obtained by sequentially stacking glass and core glass and extruding the glass while heating. 1. A method for manufacturing a glass structure for optical transmission, characterized in that the glass structure is manufactured using (3) A light transmission glass structure having at least a two-layer structure of a columnar core glass and a clad glass surrounding the core glass, the structure according to any one of claims (1) or (2). A glass structure for optical transmission, characterized in that it is manufactured using a method for manufacturing a glass structure for optical transmission. (4) An optical fiber having at least a two-layer structure of a columnar core glass and a clad glass surrounding the core glass, the optical transmission glass according to claim 1 or 2. An optical fiber characterized in that it is manufactured by using a light transmission glass structure manufactured using a method for manufacturing a structure as a preform, and drawing the preform.