JPS5827213B2 - Optical transmission line and its manufacturing method - Google Patents

Description

[Detailed description of the invention] The present invention relates to an optical transmission line and its manufacturing method.

Conventionally, optical transmission lines are often made of optical glass, but optical glass is more susceptible to impurities than quartz glass, and there are limits to the purity of raw materials and the melting process. Light absorption loss is large.

Further, as another example, there is a cladding type fiber made of quartz glass.

This is made by laminating quartz glass doped with a metal oxide to increase the refractive index higher than that of quartz glass on the inside of a quartz glass pipe, sintering it in oxygen, heating it, melting it, spinning it, and crushing the holes. making fiber.

After this, it is annealed in an oxygen atmosphere to remove distortion and completely oxidize the metal.

However, it is impossible to uniformly apply the metal oxide layer inside the quartz glass pipe because of the non-uniform flow, and it is very difficult to maintain dimensional accuracy in the length direction.

Also, since air bubbles are introduced during spinning, it is necessary to apply vacuum to close the holes.

However, evacuation reduces some of the metal oxides and Si02, which increases light absorption, which is not preferable.

The present invention eliminates the deficiencies of the prior art described above, and its purpose is to create a SiO2 layer with a low refractive index by doping F around high-purity quartz glass (with a high refractive index). Another object of the present invention is to provide an optical transmission line in which a quartz glass layer is laminated around the fiber and a method for manufacturing the same.

The high-purity silica glass shown here may contain trace amounts of elemental impurities that do not adversely affect optical transmission loss, but it does not substantially contain transition metal impurities such as Fe and Cu that adversely affect optical transmission loss. This indicates quartz glass that does not contain the above.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

Figures 1a and 1b show an example in which a quartz glass layer is grown on the outside. 1 shows the cross-sectional structure and refractive index of a fiber according to an embodiment of the present invention obtained by heating and melt-spinning a glass rod or pipe.

In the figure, A indicates a cladding type fiber, B indicates an optical zero guide, and C indicates a parabolic graded index fiber. In Fig. 1a, 1 indicates a high-purity quartz glass rod or pipe, and 2 indicates a Indicates a high-purity quartz glass part whose refractive index is lower than that of quartz glass by adding fluorine (F), 3 indicates a layer of quartz glass, and 4 indicates a hollow part (air part in this case) or F This shows high purity quartz glass doped with .

FIG. 1 shows the cross-sectional structure of a fiber obtained by melt-spinning the quartz glass rod or pipe shown in FIG. 1A, and the numbers of each part correspond to those in FIG. 1A.

Note that C indicates that near the boundary layer between the portion 2 and the portion 3, that is, the portion 2 near the layer 3, the amount of F contained increases and the refractive index decreases.

In the example shown above, the reason why the quartz glass layer 3 is attached to the outside is because H2O or H2 in the outside air reacts with F contained in this transmission line to become HF, and the part 2 is eroded. prevents it from happening.

FIG. 2 shows a diagram for explaining an example of how to make a quartz glass rod or pipe for spinning into the fiber shown in FIG.

This S describes an example in which a SiO2 layer containing F is laminated on a rod or pipe, but it goes without saying that a method of laminating the SiO2 layer on the inner surface of the pipe may also be used.

Further, as a combination of these, the following examples can be given.

(1) F-doped quartz glass is laminated on a high-purity quartz glass pipe or quartz glass rod, and then inserted into the quartz glass pipe and fused and thread-proofed.

(2) F-doped quartz glass is laminated on the inner surface of the quartz glass pipe, and then high-purity quartz glass is laminated on the inner surface of the quartz glass pipe, and this is directly or collapsed into a rod shape, and then melt-spun.

(3) After laminating F-doped quartz glass on the inner surface of a quartz glass pipe, a high-purity quartz glass rod is inserted into the inner surface of the quartz glass pipe, and this is directly or collapsed into a rod shape and then melt-spun.

In the above case, a method is used in which 5in4 is oxidized to form SiO2, and at this time, a small amount of F is included in SiO2.

As a method for synthesizing SiF4, the well-known high-purity compound Ba
S i F6 may be thermally decomposed with 2S iF6 , H2SiF6, etc., H3O3F may be applied to SiO2, or F2 may be applied to S iCl 4 .

In FIG. 2, 11 is a high-purity quartz glass rod or pipe, 12 is a burner, 13 is a matzuru, and 14 is an exhaust port.

High purity quartz glass rod or pipe with no dirt on the surface 11
arranged so that it can reciprocate in the axial direction and rotate,
On top of that, an oxyhydrogen flame from a burner is brought into contact, and SiF4 gas is fed into the burner to form SiF4 through the reaction of the following formula.
02 is made and F is contained in 5102.

When the temperature is high and there is a slight excess of oxygen, S + 0 containing F
2 is formed, which is laminated on the quartz rod or pipe 1 described above.

Since the HP produced by the reaction corrodes the quartz SiO2 by a reverse reaction when the temperature becomes low, it is necessary to treat the quartz in the furnace 3 which is evacuated and maintained at a high temperature.

The equilibrium constant is shown as follows.

In addition, oxidation with 02 containing F20 may be performed using a halide, hydride, or organic compound other than SiF4.

In some cases, a gaseous fluorine compound such as F2 may be introduced during the 02 oxidation.

It is more preferable to carry out the above oxidation using high frequency plasma or the like since HF cannot be produced.

Next, an experimental example of the present invention will be explained.

First, B a S + F a was placed in a Terex reaction tube, placed in an electric furnace, and the temperature was raised to 200° C. while reducing the pressure to dry it, and then decomposed at 300° to 500°.

The generated gas was passed through a dry ice-acetone trap to condense HF and H2SiF6, and then a white solid of SIF4 was produced in a liquid air trap.

Next, this was immersed in a C2H4 solution, evaporated at -104°C, and sent to an oxyhydrogen burner made of quartz glass as shown in FIG.

The reaction was carried out at a flow rate of 9 g of oxygen, 7 ml yr, and hydrogen of 51/ml yx, and a 5 in 2 film containing F was laminated on a moving 10 mm φ high-purity quartz glass, resulting in a diameter of 20 mm.

At this time, the pressure was reduced using several aspirators while passing an exhaust neutralizer.

Furthermore, after that, 5i (J'. is carried by 02 and sent to the same burner, a layer of only 5102 is stacked and 25 mm φ
It became.

After making the silica glass rondo in this way, it was melt-spun by heating it to a high temperature (approximately 2000°C) in an oxygen atmosphere furnace, and a clad-type fiber with an outer diameter of 235μ and an inner diameter of 95μ (i.e., part 1) was obtained. It was done.

When laser light was injected into this fiber, the light was trapped and a fiber with low transmission loss was obtained.

As explained above, in the case of the A and B types shown in Figure 1, the optical transmission line made by the method of the present invention is capable of absorbing and scattering, since the portion where light energy is concentrated is made of high-purity quartz glass. Since no defects are formed at the boundary between portions 1 and 2, scattering loss at the boundary is small, and a transmission line with low optical transmission loss can be obtained.

In addition, in the case of type C shown in Figure 1, even if F is contained, it does not have much effect on light absorption, so a product with low transmission loss comparable to quartz glass can be obtained, and the refractive index can be controlled by the amount of F. is easy, and a transmission line with little transmission loss can be obtained as a whole.

In addition, since the transmission line according to the present invention has a quartz glass layer 3 on the outside, it is stable against outside air (mainly moisture), and the part 2 containing F is protected from moisture. It does not erode due to HP reaction.

Furthermore, the method of the present invention is capable of controlling the amount of F in Si02 and uniformly dispersing F. Moreover, it prevents the incorporation of H during production, and melt-spinning is performed in an oxygen atmosphere during spinning. Therefore, it cannot be destroyed.

The optical transmission line according to the present invention is extremely effective when used as a communication cable for optical transmission, a feeder for connecting devices, a light guide, etc.

[Brief explanation of the drawing]

The figures are detailed explanatory diagrams of the present invention, in which Figure 1a shows a cross-sectional view of a quartz glass rod or pipe before spinning, and Figure 1a shows the cross-sectional structure of an embodiment of the present invention and its refractive index. Show the distribution. Here, A is clad fiber, B is optical O guide,
C indicates a parabolic graded index fiber. FIG. 2 shows a diagram for explaining a method of manufacturing a quartz glass iron or pipe for spinning into the fiber shown in FIG. In FIG. 1, 1 indicates high-purity quartz, 2 indicates high-purity quartz doped with fluorine (F), and 3 indicates quartz glass. In FIG. 2, 11 is a high-purity quartz glass rod or pipe, 12 is a burner, 13 is a matzuru, and 14 is an exhaust port.

Claims (1)

[Claims] 1. A cladding type characterized by having a high refractive index central region made of high purity quartz glass, and a low refractive index region made of high purity quartz glass doped with fluorine arranged outside the region. optical transmission line. 2 Si halides, hydrides, or organic compounds are mixed with oxygen containing gaseous fluorine compounds and burned on top of a starting member consisting of a high-purity quartz glass pipe or quartz glass rond to form fluorine-doped quartz glass. A cladding comprising a high-refractive-index central region made of high-purity quartz glass and a low-refractive-index region made of high-purity quartz glass doped with fluorine arranged outside the said region, which is characterized by laminating the layers and melt-spinning them. Manufacturing method for molded optical transmission line.