JPS60176008A - Optical fiber core - Google Patents

Abstract

PURPOSE:To flatten the frequency characteristics by forming an inner layer of silicone resin around an optical fiber, carrying out heat annealing, and forming an outer layer of thermoplastic resin. CONSTITUTION:A silicone resin coating 2 and a nylon coating 3 are successively formed around an optical fiber 1. At this time, the silicone resin coating 2 is formed, annealing is carried out by holding at 150 deg.C for 14hr, and the nylon coating 3 is formed. Annealing may be carried out by holding at 120 deg.C for 10hr after forming the coating 2, 3. Loss at about 1.4mum wavelength of light is considerably reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an optical fiber, and more particularly to a coated optical fiber in which the periphery of the optical fiber is coated.

(Background Art) Among optical fiber cores (hereinafter referred to as core fibers), which are coated optical fibers, Figure 1 shows an example of the structure of a core wire coated with silicone resin and thermoplastic plastic, which are commonly used. Shown below. In FIG. 1, reference numeral 1 indicates an optical 7-iper, 2 a silicone resin coating, and 3 a nylon coating. When the temperature of such a core wire is raised to, for example, 200C, there is a drawback that transmission loss increases abnormally.

In Fig. 1, when the optical fiber 1 is a multimode fiber doped with germanium oxide and having a core with a diameter of 50 μm, the initial characteristic of transmission loss is as shown by the solid line in Fig. 2. As shown by the dotted line in Figure 2, the transmission loss wavelength characteristics after heating to 200C and holding at 200C for 5 hours show an increase in OH absorption around 1.4 μm and an increase in wavelength from 1.5 to 1.8 μm. There is a significant increase in long wavelength loss. The instability of the characteristics at high temperatures is disadvantageous when using the optical fiber at high temperatures, or when considering long-term use even at low temperatures.

(Objective of the Invention) An object of the present invention is to provide an optical fiber core wire with improved stability of long-term characteristics at high temperatures and at room temperatures.

For example, the present invention provides a core wire with little deterioration in transmission loss even when the temperature is raised to about 200°C.

(Structure of the Invention) As shown in FIG. 2, the deterioration of transmission loss at high temperatures is caused by
This is considered to be due to the deterioration of the glass 1 and the deterioration of the glass 1.

As a result of research, the present inventors discovered that it is effective to improve the transmission loss deterioration described above by annealing the materials of each part of the optical fiber at high temperatures to remove defects in the materials. This led to the invention.

That is, the gist of the present invention is to provide an optical fiber core wire in which two or more layers of coating are applied to the outer periphery of an optical fiber wire, the outermost layer of the coating being a thermoplastic plastic, It is an object of the present invention to provide an optical fiber 6, which is characterized in that the stage #, which has been coated with more than one layer, has been previously subjected to a treatment to maintain it at a high temperature.

The annealing treatment may be performed after the final six optical fibers have been processed, or may be performed during the process. However, in the case of optical fibers, the glass base material is melted at approximately 20001r during drawing, so any annealing performed before this process will be erased in the drawing process, so annealing must be performed after the drawing process. . Therefore, there are two possible processes for performing annealing treatment, that is, high-temperature treatment: after coating the optical fiber 1 with the silicone resin 2, and after coating the outer periphery of the silicone resin 2 with the thermoplastic plastic 3. It is.

Regarding the temperature of the high-temperature treatment, due to the conflict between the upper limit of the applicable temperature and the time required to achieve the annealing effect, when performing the bed temperature treatment at the silicone resin coating stage, 1.
A value of 00C or more is suitable, and a value of 800 or more is suitable when a thermoplastic is coated and subjected to high temperature treatment.

Examples of the optical fiber core wire of the present invention whose characteristics have been stabilized by high-temperature treatment will be described below.

Example 1 A multimode fiber of the same design as the one whose transmission loss characteristics are shown in FIG. After being held for 14 hours and treated at high temperature, nylon was extruded and coated to prepare a core wire with a diameter of 900 μm.

Using this core wire, a heating test was conducted at 200C for 5 hours, and the results are shown in the graph of FIG.

In Figure 3, the solid line indicates the initial transmission loss characteristic of the core wire, and the dotted line indicates the transmission loss characteristic after temperature rise.

As shown in Figure 3, the OH absorption near 1.4 μm and the loss value between 1.5 and 1.8 μm are 0.46B/
Although it shows an increase of about
Increase in loss after temperature increase test near μm, i.e. △α(
1.4 μm) is approximately 5 dB/Krn and wavelength 1.6 μm
The loss increase Δα (1.6 μm) in the vicinity is approximately i aB/K
A significant improvement effect can be seen compared to the case of m.

In particular, the effect of stabilizing the OH absorption peak at 1.4 μm is significant.

The above shows the cord when the high temperature treatment condition is 150C and held for 14 hours, but even when the treatment temperature and treatment time are changed, the cord with improved loss characteristics equivalent to that shown in Figure 3 can be obtained. Obtained.

Example 2 The same multimode fiber used in Example 1 (and Figure 2) was coated with silicon to have a diameter of 400 μm.
After that, immediately coated with nylon and made into a diameter of 900 μm.
m core wires were created.

The core wire was subjected to high temperature treatment at 120C for 10 hours. FIG. 4 shows the results of a heating test in which the core wire after high-temperature treatment was held at 200C for 5 hours. In FIG. 4, the solid line is the initial characteristic curve of the transmission loss of the core wire, and the dotted line is the transmission loss characteristic of the wave maintained for 5 hours at 200C.
As shown in Figure 4, OH at a wavelength of around 1.4 μm
Absorption loss increase Δα after holding 200C for 5 hours
= 1 to 1.56 B/Km, and the increase in loss is suppressed to about % compared to K in the case of a conventional core wire that has not been subjected to high temperature treatment (Fig. 2).

In this method of performing high-temperature treatment after applying the nylon coating, even when the above-mentioned treatment conditions, treatment temperature, and treatment conditions were changed, the same effect as that shown in Fig. 4 was obtained as an example. Same as 1.

(Effect of the invention) As is clear from the description in Examples 1 and 2,
The optical fiber core wire of the present invention is an excellent core wire whose transmission characteristics at high temperatures and transmission characteristics over a long period of time are much more stable than those of conventional fibers.

In the explanation, the case where nylon is used as the outermost layer is exemplified, but this does not limit the application of the present invention to thermoplastic materials other than nylon, such as polyethylene, fluorine resin, etc. . Furthermore, it goes without saying that the method of the present invention is effective for use with optical fiber core wires in which the outer periphery of the optical fiber wire is coated with two or more multilayers.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating an example of an optical fiber core structure. Figures 2 to 4 show the transmission loss characteristic curves of the optical fiber core wire having the structure shown in Figure 1, where the solid line shows the initial characteristic at room temperature, the dotted line shows the temperature rise characteristic at 200C, and the m2 diagram shows the conventional In the case of the cord of the present invention, FIG. 3 shows the case of the cord of the present invention subjected to the high temperature treatment of Example 1, and FIG. 4 shows the case of the cord of the present invention subjected to the high temperature treatment of Example 2. - Fig. 1 Demon 2 Fig. 8 wave [μmn,] Fig. 3 Child 4 Wavelength -]

Claims (1)

[Scope of Claims] (11) An optical fiber core wire formed by applying two or more layers of coating to the outer periphery of an optical fiber strand, the outermost layer of the coating being a thermoplastic plastic; An optical fiber core wire characterized in that it has been previously subjected to a treatment to maintain it at a high temperature at the stage where the above-mentioned coating is applied. (2) The first layer of the coating is made of silicone resin and the second layer is made of thermoplastic plastic. The optical fiber core wire according to claim (1), which has been previously subjected to treatment to be maintained at a high temperature of 100 C or more at the stage of coating with silicone resin. (3) First layer of coating is a silicone resin, the second layer is a thermoplastic, and after applying the thermoplastic plastic coating, a treatment is performed in advance to maintain the thermoplastic at a high temperature of 80C or higher. Optical fiber core as described.