JP2002087827A - Method for manufacturing rare earth-added glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing rare earth-added glass which is capable of preventing the peeling and crack of glass particulate deposition layers. SOLUTION: This method for manufacturing the rare earth-added glass includes a first process step of introducing glass-forming material vapor into a glass tube and forming glass particulate layers within this glass tube by gaseous phase reaction, a second process step of packing a metal element- containing solution into the glass particulate layer, a third process step of drying the glass particulate layers after removing the solution from the inside of the glass tube or as it is, a fourth state of forming the composite glass tube by heating the glass particulate layers to make the layers transparent and a fifth process step of making the composite glass tube solid. The viscosity at >=500 deg.C of the glass constituting the first glass particulate layers formed in contact with the inside surface of the glass tube by forming a plurality of the glass particulate layers in the glass tube is lower than the viscosity of the glass constituting the other glass particulate layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for producing a glass product containing a rare earth element, and more particularly to a method for producing a preform for a glass fiber containing a rare earth element.

[0002]

2. Description of the Related Art An optical fiber preform has an internal CV.
It is manufactured by the D method (MCVD method). Usually, a metal chloride reaction gas such as SiCl ₄ or GeCl ₄ is introduced into a rotating glass tube together with oxygen gas, and this tube is heated by an external torch. The reaction gas inside the pipe and oxygen are caused to react uniformly. Thus, a silica fine particle deposit (soot deposition layer) is formed on the inner wall surface of the tube as a thin porous film.

In this method, a dopant such as phosphorus or boron is generally introduced in the form of a reactive gas such as a gaseous halide, and after a deposition step, the tube is collapsed into a preform. However, certain dopants that are important for optical devices, such as lasers and amplifiers, do not have a suitable gaseous or volatile halide having a vapor pressure comparable to that of the raw materials used as ordinary glass materials for optical fibers. . For example, erbium suitable for the MCVD method,
There are no gaseous compounds of rare earth elements such as yttrium, praseodymium or neodymium. Such dopants can generally be introduced using solution doping.

[0004] In the above-mentioned solution doping method, fluctuations in the dopant concentration for each preform and the dopant concentration along the length of the optical fiber drawn from the preform occur, so that a method capable of solving these drawbacks is required. Development was desired. In order to eliminate the non-uniformity in the solution-doped preform, it has been proposed to use a gas such as N ₂ O to lower the reaction temperature in the MCVD method (Japanese Patent Laid-Open No. 2000-56144).

In order to provide a rare earth doped fiber and a method of manufacturing a preform thereof in which the concentration of the rare earth element in the center of the core is not extremely reduced, a first core glass not doped with a rare earth element is used. After forming and performing the primary collapse, the second soot-like core glass doped with the rare earth element is formed to perform the final collapse, and the number of scans of the heating burner in the collapse step of doping the rare earth element is reduced. It has been proposed that the processing be performed only once (Japanese Patent Application Laid-Open No. 3-212504).

[0006]

The solution doping method according to the above-mentioned conventional method has a problem that inconsistency in the dopant concentration for each preform or the dopant concentration along the length of the optical fiber is unavoidable. Even in the method of forming a plurality of fine particle deposition layers, very precise control of glass fine particle deposition conditions is required, and the glass fine particle deposition layer is cracked or peeled off, and the yield is reduced.
Further, in order to add the dopant at a higher concentration, it is necessary to form a soot particle layer having a low bulk density, and as a result, the adhesion between the glass tube and the soot particle layer is reduced, and the glass fine particle layer is broken. , Peeling occurs. The present invention has been developed in order to solve the above-mentioned problems of the prior art in the method of manufacturing a rare-earth-added glass product, and prevents separation and cracking of a glass fine particle deposition layer (soot deposition layer),
An object of the present invention is to provide a method for producing a rare earth-added glass to which a rare earth element, a co-additive, and the like can be added at a high concentration.

[0007]

The present invention and its embodiments for achieving the above object are summarized below: (1) A glass-forming material vapor is introduced into a glass tube, and the vapor-phase reaction is carried out by a gas phase reaction. A first step of forming a glass particle layer inside the glass tube, a second step of filling the glass particle layer with a rare earth element-containing solution, and after removing the solution from the glass tube or as it is, A third step of drying, a fourth step of heating and clearing the glass fine particle layer to form a composite glass tube, and a fifth step of solidifying the composite glass tube. In the manufacturing method, a plurality of glass fine particle layers are formed inside the glass tube, and the viscosity of the glass constituting the first glass fine particle layer formed in contact with the inner surface of the glass tube at a temperature of 500 ° C. or more is: A method for producing a rare earth-doped glass, wherein the viscosity of the glass is lower than that of another glass constituting the glass fine particle layer.

(2) The method for producing a rare earth-doped glass according to the above (1), wherein the bulk density of the first glass fine particle layer is higher than the bulk density of the other glass fine particle layers. (3) When forming the first glass particle layer, at least one of an additive for increasing the refractive index with respect to quartz and an additive for decreasing the refractive index with respect to quartz is added. The method for producing a rare earth-added glass according to the above (1) or (2).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the above invention (1), the required viscosity and refractive index conditions such as silicon tetrachloride, germanium chloride, boron trichloride, and phosphorous chloride are used as the glass forming material introduced into the glass tube. Gas mixed with oxygen in addition to the steam selected to satisfy the above. Normal high temperature MC
By the VD method, the mixed gas is introduced into a hollow quartz glass tube and heated by a flame formed by an oxyhydrogen gas from the outside, and the thickness range is preferably 0.005 to 0.1 mm inside the quartz glass tube. Is formed. At this time, the surface temperature of the quartz glass tube is about 1200 to 1
Adjust to 500 ° C. The glass tube used here is not only made of quartz as described above, but also may be a glass formed by adding various additives to quartz in a tubular shape, and these are optical fibers finally obtained. Is appropriately selected based on the structure of

[0010] Preferably, the tube is rotated during this process. The first layer is a conventionally produced glass based on a mixture of SiCl ₄ and oxygen, to which additives such as phosphorus, germanium, fluorine, boron and aluminum can be added as appropriate. Raw materials to be used as precursors for doping the above elements include P
_{OCl 3, PCl 3, GeCl 4} , C 2 F 6, CF 4,
SiF ₄ , SF ₆ , BCl ₃ , AlCl _{3 and the} like are generally used, but are not limited thereto. The refractive index of the first glass particle layer can be appropriately adjusted depending on the type and ratio of the material to be doped, and either the clad or the core can be used.

Next, silicon tetrachloride, germanium chloride, etc.
A mixed gas obtained by mixing oxygen in addition to steam selected so as to satisfy the necessary viscosity and refractive index conditions is introduced in the same manner as described above, and the thickness range is preferably 0.05 mm inside the quartz glass tube.
A glass fine particle layer of about 0.2 mm is formed. At that time, the surface temperature of the quartz glass tube is adjusted to be about 1200 to 1400 ° C.

As described above, one of the features of the present invention is that a plurality of glass fine particle layers are formed, and the glass constituting the first glass fine particle layer formed in contact with the inner surface of the glass tube has a temperature of 500 ° C. or higher. The viscosity at the temperature is made smaller than the viscosity of the glass constituting the other glass particle layer.
In order to realize this state, generally, one or both of them is appropriately added with at least one of germanium, boron, and a commonly used additive, for example, phosphorus, fluorine and the like. That is, by forming a low-viscosity glass particle deposition layer at the boundary between the inner surface of the glass tube and the glass particle deposition layer, it serves as an adhesive, and even when performing glass particle deposition at a low temperature, the inner surface of the glass tube can be maintained. It can maintain or increase the adhesion of the glass fine particle deposition layer, and it is possible to add rare earth elements, co-additives, etc. at high concentration while preventing peeling and cracking of the glass fine particle deposition layer in subsequent steps Becomes In this case, the measurement of the viscosity can be confirmed by preparing and analyzing a glass sample formed at a predetermined additive ratio in advance, and forming a glass layer having a predetermined additive ratio according to the result. do it. As a method of measuring the viscosity itself, a method commonly used for measuring the viscosity of glass is used.

Next, preferably, erbium is contained inside the tube.
0.001 concentration of at least one rare earth element selected from yttrium, praseodymium and neodymium
To 0.1 mol / L, and if necessary, an aqueous solution or an alcohol solution in which aluminum or cobalt is adjusted to a concentration of 0.1 to 10 mol / L, and the solution and the whole quartz glass tube are cooled to about 20 to 80 ° C. 0.5 while holding
Hold for ~ 50 hours.

Next, the above solution is removed from the inside of the glass tube, or dry nitrogen is flowed directly into the quartz glass tube to dry the inside. At that time, the dry nitrogen gas may be heated if necessary. Next, the inside of the glass tube is set to a gas atmosphere containing chlorine, and the glass tube is heated from the outside to perform a dehydration treatment, and then the glass fine particle deposition layer is made transparent.

The invention (2) is characterized in that the bulk density of the first glass fine particle layer is higher than the bulk density of the other glass fine particle layers. This is effective in preventing the exfoliation of the glass fine particles, and as an advantageous means for realizing this state, generally, a composition which reduces the viscosity of the glass forming the first soot particle layer is used. In addition, it is preferable to increase the temperature during deposition, if necessary. In addition, the bulk density can be confirmed by preparing a soot deposition layer formed at a predetermined temperature and additive material ratio in advance, measuring the weight and volume, and adjusting the additive material ratio and the deposition temperature according to the result. Good. The progress of the integration (sintering) between the particles is determined by the temperature and how much the soot body (particle group) is heated, and the softer the soot particles are at the same heating temperature and time (= As sintering proceeds (depending on viscosity), these conditions ultimately determine the bulk density of the soot body.

In the above invention (3), when forming the first glass fine particle layer, for example, phosphorus, germanium, aluminum, titanium, nitrogen, or the like is used as an additive for increasing the refractive index with respect to quartz. As an additive for lowering the refractive index, for example, fluorine, boron,
And so on. The method of adding the additive is performed, for example, by flowing a precursor vapor into the glass tube at the same time as the formation of the glass to cause a reaction. Further, the addition of the above-mentioned additives is also one means of adjusting the viscosity. The viscosity increases when aluminum, nitrogen or the like is added, while the viscosity decreases when other additives are added.

[0017]

The present invention will be described in more detail with reference to the following examples, which are not intended to limit the present invention. (Example 1) Inside a quartz glass tube having an outer diameter of 20 mm and an inner diameter of 10 mm, 100 cc of silicon tetrachloride vapor, 100 cc of germanium chloride vapor, and 30 c of boron trichloride vapor every minute.
c, while introducing 1000 cc of oxygen and heating from the outside with a flame formed by oxyhydrogen gas, a glass fine particle layer having a thickness of about 0.03 mm was formed inside the quartz glass tube. At that time, the temperature of the surface of the glass tube was adjusted to about 1200 ° C. Next, 500cc of silicon tetrachloride vapor,
480cc of germanium tetrachloride vapor and 1500c of oxygen
In the same manner as described above, a glass particle layer having a thickness of about 0.3 mm was further formed inside the quartz glass tube. At this time, the temperature of the surface of the glass tube was adjusted to about 1200 ° C.
Next, the inside of the tube was filled with an aqueous solution adjusted to have an erbium concentration of 0.01 mol / l and an aluminum concentration of 3 mol / l. . Next, after taking out the whole quartz glass tube from the solution, 5 liters of dry nitrogen at a temperature of 50 ° C. per minute was flown into the quartz glass tube for about 7 minutes.
By continuing for 2 hours, the inside was completely dried. Next, while flowing 100 cc of chlorine per minute inside the glass tube,
Heat was applied from the outside with an oxyhydrogen flame to completely clarify the glass particle deposition layer. The obtained glass tube was further heated to gradually reduce the hollow portion, and finally a glass rod having a diameter of about 12 mm was obtained. After stretching this glass rod by heating to a diameter of about 8 mm, the glass rod is further inserted into a quartz tube having an outer diameter of 25 mm and an inner diameter of 10 mm, and integrated by heating.
m of rare earth-doped optical fiber preform was obtained. During the above steps, no peeling or cracking of the glass fine particle layer occurred.
A part of the glass rod was cut, and the concentration of erbium and aluminum in the central portion was examined by ICP emission spectroscopy. As a result, 700 ppm by mass and 6.5% by mass were added, respectively.

Comparative Example 1 A glass particle layer having a thickness of about 0.25 mm was formed on the inner surface of a quartz glass tube under the same conditions as in the second formation of the glass particle deposited layer in Example 1.
Subsequently, filling, drying, and heat transparency were performed under the same steps and conditions as in Example 1. Then, during drying using nitrogen, a part of the glass particle deposition layer inside the tube was completely detached, and a transparent glass was not obtained.

Comparative Example 2 In the same manner as in Comparative Example 1, a glass fine particle deposition layer was formed. However, the maximum temperature of the quartz tube surface at that time was set to about 1350 ° C. The solution was filled, dried, and heated and clarified under the same steps and conditions. Although the filling of the solution, the drying, and the heating and clearing could be performed without any problem, the concentration of erbium and aluminum in the central portion was examined by ICP emission analysis in the same manner as in Example 1. As a result, 200 mass ppm and 1.5 mass% were obtained. Only had been added.

(Example 2) In the same manner as in Example 1, two glass fine particle deposition layers were formed. When forming the first layer,
Instead of germanium tetrachloride vapor and boron trichloride vapor, 50 cc of phosphorus trichloride vapor was added, and the temperature of the glass tube surface was adjusted to about 1200 ° C. Next, 500 cc of silicon tetrachloride vapor and 48 germanium tetrachloride vapor were used.
0 cc and oxygen 1500 cc, as in Example 1,
A glass particle layer having a thickness of about 0.3 mm was further formed inside the quartz glass tube. At this time, the temperature of the glass tube surface was about 11
It was adjusted to be 00 ° C. Thereafter, in the same manner as in Example 1, when the solution was immersed, dried and made transparent, etc., no peeling or cracking of the glass fine particle layer occurred. When a part of the glass rod was cut and the concentration of erbium and aluminum in the center portion was examined by ICP emission analysis, 650 mass ppm and 6.3 mass% were added, respectively.

[0021]

According to the present invention, a low-viscosity glass particle deposition layer is formed at the boundary between the inner surface of the glass tube and the glass particle deposition layer, thereby serving as an adhesive and performing glass particle deposition at a low temperature. Even, it is possible to maintain or increase the adhesion between the inner surface of the glass tube and the glass particle deposition layer,
It is possible to add a rare earth element, a co-additive, or the like at a high concentration while preventing peeling and cracking of the glass fine particle deposition layer in the subsequent steps.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadashi Enomoto 1 Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Yuichi Oga 1-Tagamachi, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Sumitomo Electric Ki Kogyo Co., Ltd. Yokohama Works F-term (reference) 4G014 AH23 4G021 EA02 EB24 5F072 AB09 AK06 JJ05 YY17

Claims (3)

[Claims] 1. A first step of introducing a glass forming material vapor into a glass tube and forming a glass fine particle layer inside the glass tube by a gas phase reaction, and applying a solution containing a metal element to the glass fine particle layer. A second step of filling, a third step of drying the glass fine particle layer after removing the solution from the inside of the glass tube or as it is, and a fourth step of heating and clearing the glass fine particle layer to form a composite glass tube. And a fifth step of solidifying the composite glass tube, the method comprising the steps of: forming a plurality of glass fine particle layers inside the glass tube and forming the glass particle layer in contact with the inner surface of the glass tube. 50 of the glass constituting one glass particle layer
A method for producing a rare earth-doped glass, wherein the viscosity at a temperature of 0 ° C. or higher is lower than the viscosity of the glass constituting the other glass particle layer. 2. The bulk density of the first glass fine particle layer is as follows:
The method for producing a rare-earth-added glass according to claim 1, wherein the bulk density is higher than the bulk density of the other glass particle layer. 3. When forming the first glass particle layer, at least one of an additive for increasing the refractive index with respect to quartz and an additive for decreasing the refractive index with respect to quartz is added. The method for producing a rare-earth-added glass according to claim 1 or 2, characterized in that: