JPS5930661B2 - Method of manufacturing fiber for optical communication - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an optical fiber containing P in its core.

Background of the Invention Quartz doped with Ge and P is currently often used in the core of optical communication fibers.

Among these, material-specific loss (loss after subtracting transmission loss due to impurities and structural imperfections) is smaller in P-doped than in Ge-doped. However, fibers having a P-doped silica glass core have a coloration problem. The problem is that, almost without exception, large absorption losses occur in the fiber immediately after spinning in the ultraviolet to visible light to near-infrared range. In addition, this problem is
In the case of Ge doping, almost no occurrence occurs.

This coloration phenomenon is greatly influenced by the OH content in the core.

It is known that OH causes absorption loss at wavelengths such as 0.95 μm, but in order to reduce this absorption loss, OH
Decreasing H increases coloration. For example, OH
The one containing 20pμm of
There is a loss (coloration) with a peak value of about 40 dB/km centered at
etc., the loss value remains unchanged).

On the other hand, the same P-doped fiber with low OH has a loss of 80 dB/km at a wavelength of 0.53 μm immediately after spinning, and even after being left at room temperature for two months. The sweetness does not decrease. OBJECTS OF THE INVENTION It has been found that the coloration described above can be easily reduced by heat-treating the fiber after spinning.

The present invention is based on a new understanding of this natural phenomenon, and an object of the present invention is to provide a method for manufacturing a P-doped fiber that has low OH and low loss even in the visible range.

In the production of an optical fiber having a core including configuration P of the invention, after the fiber is spun and a primary coat is applied, it is characterized in that it is placed in an atmosphere at 80 to 100° C. for 10 to 100 hours.

Detailed Description Fibers containing P in their cores are susceptible to defects in the glass structure due to the high heat applied to the glass during the spinning process.

This is more intense than other additives. Coloration is thought to be due to this structural defect, but if an appropriate heat treatment is applied after spinning as described above, the defect will be inactivated.
It is thought that coloration will almost disappear. Until now, it has been known that coloration is reduced during the process of converting P-doped fibers into cables.

This is believed to be due to the heat received during the primary coating, extrusion of the plastic coating, and sheathing steps, but these alone are not sufficient. Therefore, the fibers are spun, applied with a primary coat, wound onto a drum, and then heat treated.

The heat treatment is performed at 80 to 200° C. for 10 to 100 hours so as not to damage the primary coat.

Also, this technique can sufficiently eliminate coloration. EXAMPLE The fiber 14 shown in FIG. 1 was made by the MCVD method.

・Core 140 is SlO2 + P2O5 (5m01%),・
Cladding 142 is SiO2+B2O3, Jacket 1
44 is SiO2, - Each refractive index is 1 as shown at the bottom of Figure 1, - Transmission loss is 3 dB/Km (AtO.85 μm), - The amount of OH in the core is about 1%.

The loss wavelength characteristic of the fiber immediately after spinning at 2100° C. is shown in curve A in FIG.

The peak loss is 90 dB/K near the wavelength of 0.53 μm.
Close to m.

When the same fiber was wound around a drum and placed in an oven at 100°C for 48 hours, the characteristics were as shown by curve B, with almost no b1 coloration.

Curve C shows the scattering loss (it is a straight line because it has a scale of λ-4 and 1 μm).

For reference, curve D shows the characteristics of a fiber having a core of low 0H (17) Ge doped silica glass immediately after spinning.

Next, FIG. 3 shows the case where the heat treatment temperature in the oven was changed.

The horizontal axis is time, and the vertical axis is scattering loss due to coloration (absorption band center wavelength 0.53 μm).

・Curve E is when left at room temperature of about 20℃ without heat treatment. ・Curve F is when heat treatment temperature is 70℃. ・Curve G is when heat treatment temperature is 80℃. ・Curve H is when heat treatment temperature is used. When is 100°C, Curve J shows when the heat treatment temperature is 200°C.

It is clear that coloration can be eliminated by any heat treatment at a temperature of 80 to 100° C. for 10 to 100 hours.

Effects of the Invention This invention is based on a new recognition of the natural phenomenon that the coloration phenomenon that occurs in fibers containing P in the core and having a low 0H can be easily reduced by heat treatment after spinning. It was done.

This invention makes it possible to produce a fiber containing P in its core, which has low 0H and almost no coloration.

Also, as mentioned at the outset, fibers containing P inherently have lower losses than those containing Ge.

A fiber with very low loss is thus obtained, especially in and near the visible region. In addition, heat treatment is 8
Since the coating is carried out at 0 to 200°C for 10 to 100 hours, there is no need to worry about damaging the primary coat.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the cross section and refractive index of the fiber used in the experiment.
FIG. 2 is a characteristic diagram of fiber wavelength vs. loss, and FIG. 3 is a characteristic diagram of heating time vs. loss in an example. 14: Faiba.

Claims (1)

[Claims] 1 In the production of an optical fiber having a core containing P, after the fiber is spun and a primary coat is applied, the fiber is left in an atmosphere at 80 to 100°C for 10 to 100 hours. method for manufacturing fibers for use in