JPH1129334A - Silica glass doped with bismuth, its production, optical fiber using its glass, and optical amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical fiber capable of amplification in a lower disperse region by using a silica glass provided with uniformly dispersed zeolite materials therein each formed of unit cells whose central sites each doped with bismuth to be clustered. SOLUTION: This silica glass for the optical fiber is obtained by the following: forming a zeolite doped with bismuth by mixing a zeolite with an aqueous solution of bismuth nitrite, stirring the mixture at room temperatures for a predetermined time, and subjecting it to filtration and dehydration; adjusting an acidity of an aqueous solution of silicon alcoholate such as tetraethyl orthosilicate and mixing this solution with an aqueous solution containing silica particles obtained by mixing silicon alcoholate, ethanol, and ammonium in the ratio of 1:1 in terms of SiO2 ; blending this resultant mixture with an aqueous solution of the zeolite doped with bismuth adjusted to a predetermined concentration so as to form a gel; and subjecting the gel to dehydration, temporary bake, and burning, thus obtaining the silica glass with clustered bismuth in the central sites of the unit cells forming a zeolite material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing B in quartz glass.
The present invention relates to a technique for doping i (bismuth).

[0002]

2. Description of the Related Art In general, in an optical communication system, an inexpensive and easily available single-mode quartz optical fiber is usually used for signal transmission. In addition, in order to amplify light attenuated during transmission in such an optical fiber, an amplification optical fiber that directly amplifies signal light without photoelectrically converting it by the stimulated emission effect may be used.

Incidentally, the zero-dispersion wavelength of an ordinary silica-based optical fiber for signal transmission is in the 1.3 μm band.

[0004] Therefore, also as an amplification optical fiber,
There is a demand to use an amplifier having an amplification characteristic in the 1.3 μm band where signal distortion is small.

[0005] As such an optical fiber having an amplification characteristic in the 1.3 µm band, conventionally, for example, P-fluoride glass has been used.
A configuration doped with r (praseodymium) is provided.

[0006]

However, such an amplification optical fiber mainly composed of fluoride glass is liable to be deteriorated in strength due to the influence of moisture and lack reliability. Fusion splicing with a silica-based optical fiber for transmission is difficult due to the different component configurations, and is more expensive than a quartz-based optical fiber.

For this reason, there is a demand to obtain a silica-based optical fiber having an amplification characteristic in the 1.3 μm band.

On the other hand, there is also a demand for obtaining a laser medium capable of generating high-brightness, high-output laser light in a 1.3 μm band as a laser medium used for nuclear fusion and the like.

Accordingly, an object of the present invention is to provide a silica-based glass, an optical fiber and an optical amplifier using the same, which can meet such demands.

[0010]

The present invention employs the following structure in order to solve the above-mentioned problems.

That is, in the bismuth-doped quartz glass according to the first aspect, zeolite is uniformly dispersed in the quartz glass, and bismuth is clustered and doped at a central site in a unit cell constituting the zeolite. It is characterized by the following.

Further, in the method for producing bismuth-doped quartz glass according to claim 2, zeolite is mixed with an aqueous solution of bismuth nitrate, and the aqueous solution is stirred at room temperature for a predetermined time and then dried to dry the bismuth-doped quartz glass. A zeolite is produced, this bismuth-doped zeolite is mixed into a sol containing quartz as a main component, the sol is gelled, dried, sintered and vitrified.

According to a third aspect of the present invention, there is provided an optical fiber using the bismuth-doped quartz glass according to the first aspect.

An optical amplifier according to a fourth aspect uses the optical fiber according to the third aspect as an amplifying element.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the bismuth-doped quartz glass of the present invention, zeolite is uniformly dispersed in quartz glass. As shown in FIG. 1, bismuth is clustered at a central site in a unit cell constituting the zeolite. And doped.

In the method for producing bismuth-doped quartz glass according to the present invention, a bismuth-doped zeolite is produced by mixing zeolite with an aqueous solution of bismuth nitrate, stirring this aqueous solution at room temperature for a predetermined period of time, and drying it. I do. Next, by applying a sol-gel method, the bismuth-doped zeolite is mixed into a sol containing quartz as a main component, the sol is gelled, dried, sintered and vitrified.

Further, the optical fiber of the present invention is constituted by using the bismuth-doped quartz glass according to the first aspect.

Further, in the optical amplifier of the present invention, the optical fiber according to claim 3 is used as an amplifying element.

FIG. 2 shows a configuration of an optical amplifier using such an optical fiber made of bismuth-doped quartz glass as an amplifying element.

In FIG. 2, a is an optical fiber as an amplifying element, b is a laser diode as a pumping light source for generating pumping light for pumping the optical fiber a, and c is an optical coupler for guiding the pumping light to the optical fiber a. , D is a polarization-independent isolator that passes only signal light in one direction,
e ₁ and e ₂ are an input end and an output end of the signal light.

An ordinary silica-based optical fiber is connected before and after the optical fiber a serving as an amplification element.

In this configuration, the pump light (for example, 0.81 μm) from the laser diode b is incident on the amplification optical fiber a via the optical coupler c and is pumped while the signal light (eg, 0.81 μm) is being pumped. When a wavelength of 1.3 μm passes through the isolator d and enters the optical fiber a, this signal light is amplified by the stimulated emission effect, and only the amplified signal light passes through the optical coupler c and the isolator d. Is emitted.

Although FIG. 2 shows a so-called backward pumping type, a forward pumping type in which signal light and pumping light are incident from the same direction may be used.

[0024]

Next, a method for producing bismuth-doped quartz glass will be described with reference to specific examples, and characteristics of the bismuth-doped quartz glass after production will also be described.

(Manufacturing method) 1. Pretreatment step Step a First, a raw material zeolite (in particular, type X in this case) is charged into a saturated aqueous ammonium chloride solution.

Then, the aqueous solution mixed with the zeolite is stirred for a sufficient time, and is left to stand. Then, the supernatant is discarded.

Thus, the Na ^{+ in} the zeolite becomes NH ₄ ⁺
Is obtained.

Step b The zeolite obtained in step a is converted to bismuth nitrate [Bi (N
O) ₃ ] and stirred at room temperature (around 25 ° C.) for a sufficient time (for example, about 1 hour).

In this case, the mixing ratio of zeolite, bismuth nitrate, and water is set to, for example, a weight ratio of (zeolite), (bismuth nitrate) :( water) = 2: 1: 10.

As a result, N ₄ ⁺ in the zeolite becomes Bi ³⁺
To obtain a bismuth-doped zeolite. In addition, the bismuth-doped zeolite in this case is present in a state where bismuth is clustered at the central site (super cage) in the unit cell constituting the zeolite as shown in FIG.

Step c Next, the bismuth-doped zeolite is filtered to remove water, and further dried sufficiently using a dryer or the like.

It is also possible to omit step a and start from step b, ie, a step of directly mixing the raw material zeolite into an aqueous solution of bismuth nitrate.

The following processing can be performed instead of the step a.

First, a raw material zeolite (particularly type X in this case) is charged into an aqueous solution of yttrium chloride [YCl ₃ ] at 100 ° C., and the aqueous solution is stirred for a sufficient time (for example, 2 weeks). After standing still, discard the supernatant. This gives a zeolite in which Na ⁺ has been completely replaced by Y ⁺ . Subsequently, the zeolite is mixed into an aqueous solution of saturated ammonium chloride, and the aqueous solution is stirred for a sufficient time (for example, 4 hours), left to stand, and the supernatant is discarded. Thereby, the central site (Super Cag) in the unit cell constituting the zeolite is obtained.
Most of Y ⁺ present in e) is extracted. After that,
Move to step b.

When the treatment using yttrium chloride is performed as described above, sodium in the zeolite can be further reduced, so that improvement of characteristics such as improvement of water resistance can be achieved.

2. This Step In this step, the so-called sol-gel method (for example, by Sakubana Shizuo: published by Agne Shofusha. "Science of the sol-gel method")
Apply). Hereinafter, a specific description will be given.

Step d: Silicon alcoholate and water are mixed at a predetermined ratio, and the acidity is adjusted with hydrochloric acid (for example, to pH = 1.5). Stir.

As the silicon alcoholate in this case, tetra-ethyl-ortho-silicate (TEOS)
Alternatively, tetra-methyl-ortho-silicate (TMOS) or the like can be used. When TEOS is used, the mixing ratio with water is, for example, (T
EOS) :( water) = 208: 180 ≒ 10: 9.

Step e On the other hand, water is mixed at a predetermined ratio with water, which is obtained by mixing commercially available Tegusa OX50 or the like, TEOS, quartz particles produced by mixing ethanol and an aqueous ammonia solution (pH ≒ 11.5), and mixing for a predetermined time.
This is stirred for about 2 hours, for example.

Step f The aqueous solution obtained in step d and the aqueous solution obtained in step e are mixed at a predetermined ratio and stirred.

The mixing ratio of the aqueous solutions obtained in steps d and e is, for example, 1: 1 in terms of the amount of SiO _2.
Set to.

Step g The bismuth-doped zeolite obtained in the preceding steps a to c is dissolved in water at a weight ratio of 5 times.

Step h Subsequently, the aqueous solution obtained in the previous step f is combined with the aqueous solution obtained in the previous step g.
After mixing with the aqueous solution obtained in the above, so that the desired bismuth concentration is equivalent, a 0.1 N ammonia solution is added to the mixture to cause gelation.

Step i This gel is sufficiently dried to remove water and the like. For example,
The gel was dried at 80 ° C. for 24 hours, followed by 110
Dry at 2O 0 C for 2 weeks.

Step j Next, this gel is pre-sintered at a relatively low temperature for a predetermined time (for example, at 1200 ° C. for 4 hours) to obtain a porous soot state. (For example, at 1750 ° C. for 1.5 hours) to obtain a transparent glass.

In the bismuth-doped quartz glass thus obtained, the zeolite becomes amorphous, but the bismuth present at the central site (super cage) in the zeolite unit cell is clustered without diffusing much. It remains in a state.

This can be determined to some extent from the appearance. That is, when zeolite is not contained, the whole is light yellow, whereas in the case of bismuth-doped quartz glass containing zeolite as in the present invention, the whole is light pink. Can also determine the difference in characteristics.

The various conditions in the above manufacturing process are merely examples, and the present invention is not necessarily limited to such conditions.

For example, in this example, the zeolite
(Here, in particular, type X) is premised on containing sodium ions, but the present invention is also applicable to zeolite of a different type containing other elements such as calcium ions.

In addition, instead of the above-described embodiment, the following modified example can be considered.

1. Regarding zeolite Zeolite is usually a crystal having ion-exchange properties, and it has been confirmed that several hundred or more zeolites, including natural and synthetic ones, are present. All of them have applicability. That is, it can be used instead of the X type. In particular, since the Y and A types have the same crystal structure, they can be used similarly to the X type.

Most of the zeolite is composed of Si and Al, but as special substances, P and A
There is also a substance (aluminoline-based zeolite) composed of l, so if it is necessary to mix P, such a zeolite can be used.

2. Production of zeolite with less Na ion By replacing the zeolite with Y ion as described above, it is possible to produce zeolite with less Na ion contamination.
The same effect can be obtained by the a ion.

(Characteristics of Bismuth-Doped Quartz Glass) With respect to the bismuth-doped quartz glass obtained according to the above-described production method, the results of examining the fluorescence characteristics and the results of examining the absorption characteristics are shown in FIGS. Show.

In these figures, the solid line represents the bismuth-doped quartz glass of the present invention doped with bismuth using zeolite (hereinafter, referred to as the present invention), and the broken line represents bismuth simply without using zeolite. It shows a product doped into quartz glass (hereinafter referred to as a conventional product).

The conditions for measuring the fluorescence characteristics were as follows: excitation light source: Xe lamp (peak wavelength 500 nm, full width at half maximum 50 n
m), Receiver: Ge semiconductor, resolution of spectrometer is about 1nm,
The dimensions of the sample were 5 × 5 × 1 mm.

The conditions for measuring the absorption characteristics are those obtained by measuring the transmitted light of a halogen lamp. The photoreceiver is a photomultiplier tube, the resolution of the spectroscope is about 1 nm, and the thickness of the sample is 1-2 mm. Of the degree.

As can be seen from FIG. 3, in the conventional product, 1.
While no fluorescence is observed in the 3 μm band, the product of the present invention shows a large fluorescence intensity in the 1.3 μm band. In addition, a long life (τrad = 650 μs) and a wide width (Δλ = 2
50 nm) and a moderate stimulated emission cross section (≒ 1.0 × 1.0 ⁻²⁰⁾
cm ² ).

For this reason, it is possible to manufacture a silica-based amplification optical fiber capable of amplification in a low dispersion region (λ = 1.3 μm band).
Moreover, application as a laser medium for high luminance, high heat resistance, and high output is also possible.

As can be seen from FIG. 4, BandX and BandY are the products of the present invention, and have absorption peaks at 500 nm and 70 nm.
There are two lines of 0 nm. In particular, when used as an optical fiber amplifying medium, excitation by a semiconductor laser of around 680 nm is possible, and as a laser medium for nuclear fusion, excitation by a conventional flash lamp can be sufficiently used.

[0061]

According to the present invention, the following effects can be obtained.

(1) It is possible to manufacture a silica-based amplification optical fiber capable of amplification in a low dispersion region (λ = 1.3 μm band).

(2) It can be applied as a laser medium for high brightness, high heat resistance, and high output.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the structure of a unit cell of bismuth-doped zeolite obtained in the course of manufacturing the bismuth-doped quartz glass of the present invention.

FIG. 2 is a configuration diagram of an optical amplifier using an optical fiber composed of bismuth-doped quartz glass of the present invention as an amplification element.

FIG. 3 is a diagram showing the fluorescence characteristics of the bismuth-doped quartz glass of the present invention.

FIG. 4 is a diagram showing the absorption characteristics of the bismuth-doped quartz glass of the present invention.

Continued on the front page (72) Inventor ▲ Yoshi ▼ Minoru 4-chome, Ikejiri, Itami-shi, Hyogo Mitsubishi Cable Industry Co., Ltd. Itami Works (72) Inventor Yasuhide Sudo 4-3-1, Ikejiri, Itami-shi, Hyogo Mitsubishi Cable Industries Inside Itami Works

Claims (4)

[Claims] 1. Bismuth-doped quartz glass, characterized in that zeolite is uniformly dispersed in quartz glass and bismuth is clustered and doped at a central site in a unit cell constituting the zeolite. 2. A zeolite is mixed with an aqueous solution of bismuth nitrate, and the aqueous solution is stirred at room temperature for a predetermined time, and then dried to produce a bismuth-doped zeolite. A method for producing bismuth-doped quartz glass, comprising mixing into a sol to be formed, gelling the sol, drying, sintering and vitrifying the sol. 3. An optical fiber comprising the bismuth-doped quartz glass according to claim 1. 4. An optical amplifier, wherein the optical fiber according to claim 3 is used as an amplifying element.