JP3707937B2 - Glass and optical fiber manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing glass and an optical fiber, and more particularly to a method for producing glass and an optical fiber having a low OH group content.
[0002]
[Prior art]
In general, it is known that transmission characteristics of optical fibers deteriorate due to water (OH groups) contained therein, and various manufacturing techniques are being developed to reduce such OH groups.
[0003]
That is, for example, Japanese Patent Application Laid-Open No. 1-124805 discloses a so-called external method (OVD method = Outside Vapor-Phase Deposition) or gas phase axis method (VAD method = Vapor-Phase Axial) in the production of silica-based optical fibers. The glass particulate deposit (porous matrix) produced by Deposition) is held in a heating furnace at a temperature of 600 ° C to 800 ° C or higher, and D ₂ O (heavy water) vapor is fed into it to make it porous. of H ₂ O in the base material (water) is replaced with D ₂ O, further subjected to dehydration treatment with a chlorine-based gas, a method of reducing remove residual H ₂ O and substituted D ₂ O is described .
[0004]
Moreover, Te manufacturing odor multicomponent glass optical fiber, the glass being melted in the crucible was set in a heating furnace, the D ₂ O to dry gas, such as CO ₂ gas or N ₂ gas as a carrier through a pipe A method of replacing the OH group with the OD group by sending it in has also been proposed .
[0005]
[Problems to be solved by the invention]
However, in the former method, the substitution rate of H ₂ O to D ₂ O is not so high even though a large amount of D ₂ O vapor is sent into the heating furnace, and the content of OH groups is sufficiently reduced. It is difficult.
[0006]
On the other hand, the latter method also has a conversion rate of OH groups to OD groups of about 90%. In addition, the pipe must be inserted directly into the molten glass and gas must be sent in for a long time. There is a possibility of causing a shift in the glass composition due to melting.
[0007]
The present invention has been made in response to such a conventional situation, and a glass manufacturing method capable of manufacturing an optical fiber having a small OH group content and improved transmission characteristics, and an optical fiber using the same. It aims at providing the manufacturing method of.
[0008]
[Means for Solving the Problems]
In the first invention of the present application, a porous material composed of a glass raw material mainly composed of oxide or glass fine particles mainly composed of oxide is placed in an inert gas atmosphere containing heavy water at 0 ° C. to 100 ° C. for 1 hour. After the above holding, vitrification treatment is performed.
[0009]
Further, the second invention of the present application is the method for producing an optical fiber comprising a step of vitrifying a porous material comprising a glass raw material mainly composed of an oxide or glass fine particles mainly composed of an oxide. The raw material or porous body is maintained in an inert gas atmosphere containing heavy water at 0 ° C. to 100 ° C. for 1 hour or longer, and then vitrification is performed.
[0010]
In the present invention, by maintaining in an inert gas atmosphere containing heavy water for 1 hour or more prior to vitrification treatment, the substitution from OH groups to OD groups proceeds efficiently during vitrification treatment, and OH group containing A low-loss glass and an optical fiber with a small amount can be obtained. This is presumably because OD group substitution during vitrification proceeds efficiently by adsorbing D ₂ O molecules to the raw material or porous body before vitrification. In such a method, it is not necessary to keep the atmosphere at a particularly high temperature as in the conventional method, and contamination of impurities and compositional deviation due to insertion of a pipe are prevented.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0012]
FIG. 1 is a diagram showing an example of a method for producing glass by a so-called melting method, which is an embodiment of the present invention.
[0013]
As shown in FIG. 1, in the present invention, a glass raw material 2 prepared in a desired composition is put into a crucible 1 and put into a heating furnace 3. The glass raw material 2 used here is mainly composed of oxides, and is composed of silicic acid (SiO ₂ ), alumina (Al ₂ O ₃ ), soda (Na ₂ O), potash (K ₂ O), boron. Oxide-based glass materials mainly composed of oxides such as acid (B ₂ O ₃ ), lime (CaO), magnesia (MgO), and lithium oxide (LiO ₂ ) can be used as they are, and sodium carbonate (Na ₂ CO ₃ ), porous material obtained by pre-sintering glass materials containing carbonates such as calcium carbonate (Ca ₂ CO ₃ ) and hydroxide compounds such as aluminum hydroxide (Al (OH) ₃ ) Alternatively, a pulverized one, a glass powder obtained by pulverizing a glass material obtained by once melting various glass raw materials, a glass precursor produced by a sol-gel method, or the like is used.
[0014]
The inside of the heating furnace 3 is maintained in an inert gas atmosphere containing D ₂ O by sending an inert gas 5 such as N ₂ gas, Ar gas, and He gas passed through D ₂ O 4 through a pipe 6. Thus, the glass raw material 2 is held for 1 hour or longer in such an atmosphere. The temperature in the heating furnace 3 during this period is preferably in the range of 0 ° C. to 100 ° C. from the viewpoint of the substitution efficiency of OH groups to OD groups, and if it exceeds 100 ° C., the amount of adsorbed D ₂ O molecules decreases, Replacement efficiency of OH group to OD group decreases. Practically, the range of 10 ° C to 50 ° C is more desirable.
[0015]
Thereafter, the glass raw material 2 is maintained in an inert gas atmosphere containing D ₂ O in the heating furnace 3, and is usually subjected to normal vitrification treatment, that is, melting, fining according to the composition of the glass raw material, Each process of cooling is performed and glass is manufactured. In FIG. 1, 7 indicates a D ₂ O storage tank.
[0016]
In such methods, while being maintained under an inert gas atmosphere containing D ₂ O, results D ₂ O molecules are adsorbed to the glass material, upon melting, the raw material is sufficiently exposed to D ₂ O atmosphere Therefore, OH groups are efficiently substituted with OD groups, and a glass containing almost no OH groups is produced. Further, in this method, since the pipe is not inserted as in the conventional method, the change in the glass composition due to the mixing of impurities and the melting of the pipe is also prevented.
[0017]
In addition, by applying the above method to the double crucible method, that is, for example, using a heating furnace for manufacturing an optical fiber, a so-called spinning furnace instead of the above heating furnace, and using a double crucible for the crucible, OD A low-loss optical fiber having a high group substitution rate, that is, an extremely low OH group content can be obtained.
[0018]
Although not described with reference to the drawings, the present invention is also applicable to the case where an optical fiber preform is produced from a porous body obtained by depositing glass fine particles, and an optical fiber is produced from this preform. Can be applied.
[0019]
That is, an optical fiber glass fine particle deposit (porous base material) produced by an external method, an internal method, a gas phase axis method, etc. is set in a heating furnace, and D ₂ O is applied in the same manner as in the above example. After maintaining in an inert gas atmosphere containing glass, it is desirable to obtain a glass preform for optical fiber in which most of the OH groups are replaced with OD groups by transparent vitrification while maintaining the same atmosphere. This can be used to manufacture an optical fiber with excellent transmission characteristics with little absorption loss due to OH groups.
[0020]
【Example】
Next, examples of the present invention will be described.
[0021]
Example 1
SiO ₂ , Al (OH) ₃ , and Na ₂ CO ₃ as glass raw materials were mixed in a crucible, set in a heating furnace, and heated at a temperature of 620 ° C. for about 3 hours in an air atmosphere. Next, the heat-treated raw material was put in a quartz mortar and pulverized using a pestle, then transferred to a Teflon container, added with 3 to 4% by weight of D ₂ O of the raw material, and stirred using a ball mill. D ₂ O is added to prevent the dried raw material from absorbing moisture (H ₂ O) in the atmosphere and to suppress the scattering of the raw material when it is put into the electric furnace after stirring. is there.
[0022]
Thereafter, the sufficiently stirred raw material was put in a crucible and set in an electric furnace, while N ₂ gas passed through D ₂ O was poured into the electric furnace and left at room temperature. After about 3 hours, the temperature inside the furnace was raised, heated in a N ₂ gas atmosphere through D ₂ O for 2 hours at a temperature of 830 ° C, and further raised to 1400 ° C. After clarification for 6 hours, it was gradually cooled to obtain a multicomponent glass (Na—Al—Si—O-based glass). The transmittance-wavelength characteristic of the obtained glass is shown in FIG.
[0023]
For comparison, FIG. 2 shows the transmittance-wavelength characteristics of a multicomponent glass having the same composition without OD group substitution, that is, a glass obtained by melting a glass raw material as it is without being treated with D ₂ O. Shown in (B).
[0024]
As is clear from these figures, in the glass of the example, the absorption around 2.9 μm due to the OH group is decreased.
[0025]
Example 2
The same processing as in Example 1 was performed on the glass material for the core of the optical fiber and the glass material for the cladding. That is, glass raw materials are mixed in a crucible, set in a heating furnace, heated in an air atmosphere at a temperature of 620 ° C. for about 3 hours, and then the heat-treated raw materials are put in a quartz mortar and pulverized using a pestle. Then, it was transferred to a Teflon container, D ₂ O of about 3 to 4% by weight of the raw material was added, and the mixture was stirred using a ball mill.
[0026]
Then, the sufficiently stirred glass material for the core and the glass material for the clad are respectively put into the core part and the clad part of the platinum double crucible set in the spinning furnace, while passing through D ₂ O. _Two gases were poured into the spinning furnace from above the core of the double crucible using a platinum pipe and left at room temperature. After about 1.5 hours, the temperature inside the furnace was raised, heated in a N ₂ gas atmosphere passed through D ₂ O for 2 hours at a temperature of 830 ° C, and further raised to 1400 ° C. A 6-hour clarification was performed. Thereafter, the temperature was maintained at 800 ° C. to 900 ° C., and the fiber was spun when the glass temperature was sufficiently stabilized to obtain an optical fiber.
[0027]
The wavelength loss of the obtained optical fiber is shown in FIG.
[0028]
For comparison, the wavelength of an optical fiber using a glass raw material having the same composition without OD group substitution, that is, an optical fiber obtained by melting and spinning the glass raw material as it is without being treated with D ₂ O. The loss is shown in FIG.
[0029]
As is clear from these figures, in the optical fiber of the example, the absorption around 1.4 μm, which is a second harmonic wave of the absorption of 2.9 μm due to the OH group, decreases.
[0030]
【The invention's effect】
As is clear from the above examples, according to the present invention, the material is simply and at a high rate contained in the inert gas atmosphere containing heavy water before vitrification. An OH group can be substituted with an OD group, and a glass or an optical fiber with low absorption loss due to the OH group can be obtained.
[Brief description of the drawings]
FIG. 1 shows an example of a method for producing glass according to the present invention.
2A is a graph showing the transmittance-wavelength characteristics of the glass obtained in the example of the present invention, and FIG. 2B is a graph showing the transmittance-wavelength characteristics of the glass of the comparative example.
FIG. 3 is a diagram showing a wavelength loss spectrum of an optical fiber obtained in another example of the present invention.
[Explanation of symbols]
1 ……… Crucible 2 ……… Glass raw material 3 ……… Reheating furnace 4 ……… D ₂ O
5 ……… Inert gas 6 ……… Pipe 7 ……… D ₂ O storage tank

Claims (2)

A glass raw material mainly composed of oxide or a porous body composed of fine glass particles mainly composed of oxide is kept in an inert gas atmosphere containing heavy water at 0 ° C. to 100 ° C. for 1 hour or longer, and then vitrified. A method for producing glass, characterized in that: In a method for producing an optical fiber including a step of vitrifying a glass raw material mainly composed of oxide or a porous body composed of glass fine particles mainly composed of oxide, the glass raw material or porous body contains heavy water. A method for producing an optical fiber, comprising vitrification after holding in an inert gas atmosphere at 0 ° C to 100 ° C for 1 hour or more.

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