JPS61158304A - Single mode-type optical fiber - Google Patents

Abstract

PURPOSE:To prevent an increase in the loss of long waves even when the title fiber is exposed to the atmosphere contg. hydrogen molecules by forming >=1 glass layer on the outer periphery of a glass clad, and composing at least one glass layer of hydrogen-resistant doped quartz having a glass structural defect. CONSTITUTION:A core 1 and a clad 2 consist of a quartz material, the core 1, for example, consists of SiO2-GeO2, and the clad 2 consists of SiO2. A hydrogen-resistant glass layer 3, for example, consists of SiO2-P2O5. Anyelements capable of generating a structural defect in the quartz glass can be adopted as the dopant of the glass layer 3, and germanium can be exemplified as the dopant other than phosphorus. A glass layer 4, for example, consists of SiO2. The porous glass layer for the core 1 and the porous glass layer for the clad 4 are simultaneously synthesized by the VAD method to prepare a porous glass base material. Then, the base material is placed in an electric furnace, treated, and vitrified into transparent glass. Meanwhile, the inside of a synthetic quartz into used as the glass layer 4 is lined with the glass used as the glass layer 3. The lined synthetic quartz tube is jacketed on the outer periphery of the base material, and spinning is carried out to obtain the desired SM-type optical fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a single mode (Slit type) optical fiber for communication.

"Prior Art" With the rapid growth of optical fiber technology, optical communications are becoming mainstream, and submarine communication cables are also being put into practical use using optical fibers.

The optical fibers used for these are Glaceon index type (Gl type), single mode type (SM type), etc., but low loss and wide band characteristics are required for submarine cables, so we have to satisfy these requirements. SN type optical fiber is considered a no-go.

In addition, SN type optical fibers for submarine cables are required to have strict characteristics such as high strength and no increase in long wavelength loss, so research and development from these viewpoints is also progressing.

f Problems to be Solved by the Invention J Generally, when obtaining a high-strength SN type optical fiber, a jacket layer made of synthetic quartz is formed around the outer periphery of the optical fiber, but this jacket layer (synthetic quartz) is When the molecules pass through, some of the hydrogen molecules are sent as they are to the cladding and the core, and this causes 5
Since i-H is generated, an absorption peak appears at 1.52g+e, etc., causing an increase in long wavelength loss.

In view of the above-mentioned problems, the present invention aims to provide a single-mode optical fiber that does not cause an increase in long wavelength loss even when exposed to an atmosphere containing hydrogen molecules. be.

Means for Solving Problem T" The present invention provides a single-mode optical fiber in which a quartz-based cladding is formed on the outer periphery of a quartz-based core, in which one or more glass layers are formed on the outer periphery of the L-shaped rad. The glass layer is characterized in that at least one glass layer is made of a hydrogen-resistant doped quartz system with glass structural defects.

(7. Effect) The 5M type optical fiber according to the present invention has a doped quartz-based hydrogen-resistant glass layer having glass structural defects formed on the outer periphery of its cladding.

For example, if the core is Sin2-Gem2. The cladding is SiO
When the hydrogen-resistant glass layer of an SN-type optical fiber made of phosphorus-doped quartz is made of 5i02-P2O3, structural defects in the glass dramatically increase due to the following reasons.

P is stable when the valence is ÷5, but in quartz glass, P is
Since it is easy to coordinate four ugliest atoms around it, it has a charge equal to ÷1.

However, electrical neutrality cannot be maintained with this, so P with -1 valence charge, which coordinates six uglies, exists nearby, and in other words, an electric field exists within the quartz glass. It turns out.

When hydrogen molecules pass through this electric field, the originally nonpolar hydrogen molecules become polarized, creating a cloud of unevenly distributed electrons.

Such hydrogen molecules have a high energy state and are thought to cause the following reaction with structural defects in the glass.

-G, e-Q-0-('e-+H2+ 2GeOH*
e e e (1) The high-energy hydrogen reacts with the defect shown in the following formula, but due to its high reactivity, the reaction progresses further and reaches the right side in a short time.

I 1 → −s, i −0−5, + −+ ) No. 12 ・ ・
・Fist (2) Therefore, in the case of synthetic quartz containing P etc. as a dopant, 1
, 521h m absorption peak and 1,3' due to 5iOH
Almost no absorption peak of Jgm is observed.

On the other hand, when hydrogen molecules pass through synthetic quartz that does not contain any P, there is no large electric field in the quartz, so the polarization described above is not so large and the energy of the hydrogen molecules is not high.

Such hydrogen causes the reaction shown in the formula below, but its low reactivity means that it takes a long time to reach the right side. 5i-H for synthetic quartz
Absorption peak at 1,52 u ta associated with binding, 5i
Absorption peaks of 1, 39u and layers due to OH are observed.

By the way, in the case of an SN type optical fiber, its core diameter is extremely small, such as 8:125, compared to the outer diameter (diameter) of the optical fiber, and in actual use at room temperature, most of the hydrogen molecules hardly reach the core.

Therefore, as in the previous example, the core is S i 02-G
A general S consisting of e 02, cladding force <, 5i02
In the case of N-type optical fibers, the reaction of equation (3), which attacks the structural defects of Si in the cladding, is much more important than the reaction of equation (1), which attacks the structural defects of Ge in the core. .

As described above, the SM type optical fiber according to the present invention is
Since a doped quartz-based hydrogen-resistant glass layer having glass structure defects is formed on the outer periphery of the cladding, an increase in long-wavelength loss can be prevented by the hydrogen-resistant glass layer.

7 Embodiment j Hereinafter, an embodiment of the SN type optical fiber according to the present invention will be described.
This will be explained with reference to the drawings.

In FIG. 1, l is a core, 2 is a cladding, 3 is a hydrogen-resistant glass layer formed on the outer periphery of the cladding 2, and 4 is a glass layer formed on the outer periphery of the glass layer 3.

Both the core 1 and the cladding 2 are quartz-based, and as an example, the core 1 is S+02-GeO2 and the cladding 2S +
Consists of 02.

For example, the hydrogen-resistant glass layer 3 is 5i02-P2O3.
However, as the dopant for the glass layer 3, various elements can be used as long as they are elements that cause structural defects in silica glass, and dopants other than phosphorus include germanium, tin, titanium, aluminum, boron, sodium, Examples include lithium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, iron, copper, and nickel.

Further, the glass layer 4 is made of 5102 as an example.

The SN type optical fiber exemplified above is manufactured by the following method, for example.

First, by the VAD method, a porous glass layer for the core 1 made of S+02-GeO2 and a porous glass layer for the cladding 2 made of S+02 are simultaneously synthesized to create a porous glass base material.

Next, the porous glass base material was placed in an electric furnace at 1200°C, and inside the furnace) Ie: 30, 02: 3IL, C12
The base material was dehydrated while supplying He:301tttN.
While doing so, the base material is made into transparent glass.

On the other hand, MC was added to the inner peripheral surface of the synthetic quartz tube for glass layer 4.
Glass for the glass layer 4 is attached internally through the VD, and the internal structure is made by jacketing the synthetic quartz tube on the outer periphery of the transparent glass base material and attaching them by a conventional method. Spinning.

In this way, the desired 9M type optical fiber is obtained.

Figure 2 shows the SN type optical fiber of the present invention (
solid line) and a conventional 9M type optical fiber without a hydrogen-resistant glass layer (dotted line) at 80°C, respectively.

This is the result of being exposed to a hydrogen atmosphere for 30 minutes.

Incidentally, the dashed dotted line in FIG. 2 shows the initial spectra of the present invention and the conventional example.

As is clear from FIG. 2, the SN type optical fiber of the present invention (
The solid line) has no long wavelength loss λ even when exposed to a hydrogen atmosphere, whereas the conventional SN type optical fiber (dotted line) has a problematic long wavelength loss.

In the embodiment described above, the hydrogen-resistant glass layer 3 is formed on the outer periphery of the cladding 2, and the glass layer 4 is further formed on the outer periphery, but this glass layer 4 may be omitted in some cases.

In this case, glass for the hydrogen-resistant glass layer 3 may be externally attached to the outer periphery of the transparent glass base material described above, and this may be spun using a conventional method.

However, from the point of view of increasing the strength of the SN type optical fiber, it is desirable to form the glass layer 4 on the outer periphery of the glass layer 3.

"Effects of the Invention j As explained above, the SiM optical fiber according to the present invention has a doped quartz-based hydrogen-resistant glass layer having glass structural defects formed on the outer periphery of the cladding.
For long wavelengths such as 1.394 m and 1.59 h*, it is possible to prevent an increase in loss due to hydrogen.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of an SN type optical fiber according to the present invention, and FIG. 2 is a characteristic comparison diagram between the optical fiber l< of the present invention and a conventional example. 1...Core 2...Clad 3 -Φ・Hydrogen-resistant glass layer 4...Fist glass layer

Claims (3)

[Claims] (1) In a single-mode optical fiber in which a quartz-based cladding is formed around the outer periphery of a quartz-based core, one or more glass layers are formed around the outer periphery of the cladding, and at least one of the glass layers has a glass structure. A single-mode optical fiber characterized by being made of hydrogen-resistant doped quartz that has defects. (2) The single mode optical fiber according to claim 1, wherein a hydrogen-resistant glass layer is formed on the outer periphery of the cladding, and a quartz-based glass layer is formed on the outer periphery of the glass layer. (3) The hydrogen-resistant glass layer contains phosphorus as a dopant.
Claim 1 containing at least one of germanium, tin, titanium, aluminum, boron, sodium, lithium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, iron, copper, and nickel; The single mode optical fiber according to any one of Item 2.