JPS59155804A - Optical fiber having metallic coated layer - Google Patents

Abstract

PURPOSE:To obtain a titled optical fiber which is excellent in its moisture resistance and has a long life and a small transmission loss, and also to constitute it so that the transmission loss does not increase even if an external force is applied, by coating successively a metallic coated layer, a thermosetting resin layer and a buffering resin layer onto the outside circumferential surface of an optical fiber bare wire. CONSTITUTION:An optical fiber bare wire 1 is protected by a metallic coated layer 2, moisture does not work on a minute surface defect of the bare wire 1, and it is excellent in its moisture resistance. The metallic coated layer 2 is formed thinly, and its transmission loss does not become large as a usual metallic coated optical fiber. Also, it is prevented that the thinly formed metallic coated layer 2 is stripped off from the optical fiber bare wire 1 by a thermosetting resin layer 3, therefore, the metallic coated layer 2 can protect enough the optical fiber bare wire 1, and an optical fiber which is excellent in its reliability for a long period of time. Also, since a buffering resin layer 4 is provided on the outside circumferential surface of the resin layer 3, an external force applied to the optical fiber is softened and absorbed by this resin layer 4, and an increase of the transmission loss by an external force is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure of an optical fiber provided with a metal sheathing having low loss.

BACKGROUND ART Conventionally, in applications requiring moisture resistance, long-term reliability, etc., metal-broken optical fibers, in which bare optical fibers made of quartz glass are coated with metal, have been used.

The purpose of applying the metal coating is to block moisture that acts on minute surface defects in the optical fiber loincloth made of silica glass, causing the defects to fully grow and reducing the strength of the optical fiber.

However, in conventional metal-coated optical fibers, the metal coating layer is thick, which increases microbending loss due to shrinkage when the metal cools and solidifies after metal coating is applied to the bare wire. Not only do hiIllllll
Mainly because it becomes a rich light and fiber.

When the optical fiber is bent during the installation of the optical fiber, there is a problem in that microbending loss increases by as much as pJ.

The research was conducted in view of the above circumstances, and the purpose is to provide an optical fiber coated with a metal coating, which is moisture resistant, has a long life, and has low transmission loss.

The present invention will be explained below with reference to the drawings.

FIG. 1 shows an example of an optical fiber having a metal coating layer according to the present invention, and numeral 1 in the figure is a bare optical fiber made of quartz glass. The outer peripheral surface of this bare optical fiber 1 is coated with a metal coating layer 2, a thermosetting resin layer 3. A buffering resin layer 4 made of silicone rubber is successively formed to form the optical fiber of the present invention.

The metal coating layer 2 formed on the outer circumferential surface of the bare optical fiber 1 prevents moisture from penetrating from the outside, which acts on the surface defects of the optical fiber ridge l, causing the defects to grow and reducing the strength of the optical fiber. This protects the bare optical fiber.
,U,,Si,W.

Metals such as Au can be processed by dip method, sputtering method, CVD method, P
It is coated by a VD method or the like.

This metal coating layer 2 is formed thinner than the metal coating layer of a general metal coated optical fiber, and has a thickness of 0.1 to 2 μm.
It is desirable to set it to m. Metal coating layer 2 is 0.1 μm
,! : If υ is thin, it will not be possible to prevent moisture from penetrating, and it will easily peel off when some kind of mechanical contact occurs, and if the metal coating layer 2 is thicker than 2 μm. As described above, the rigidity of the optical fiber increases, causing minute bends in the optical fiber and increasing transmission loss, making it impossible to achieve the object of the present invention.

However, if the metal coating layer 2 is formed thinly in this way,
A hillox phenomenon occurs in which the metal coating layer 2 peels off from the bare optical fiber l. This hillox phenomenon occurs when the optical fiber expands/contracts/stiffs when it is bent, and expands/contracts due to temperature changes, causing a misalignment at the interface between the bare optical fiber 1 and the metal coating layer 2, and this misalignment is repeated. It is something that happens due to this.

The thermosetting resin layer 3 is applied to prevent the metal coating layer 2 from peeling off from the bare optical fiber 1 due to this hillox phenomenon. 1
The fat layer 3 is generally made of highly rigid thermosetting material in order to tightly adhere the metal coating layer 2 to the surface of the bare optical fiber 1 so that the metal coating layer 2 does not peel off from the surface of the bare optical fiber 1. It is made of resin, and its thickness is 0.5~
3μm! : It is desirable to do so. When this thermosetting resin layer 3 becomes thinner than 0.5 μIn, the effect of preventing the hillox phenomenon of the metal coating layer 2 becomes small, and when it becomes thicker than 3 μm, the coated thermosetting resin 1-3 hardens. When the optical fiber contracts, it tends to cause a slight bend in the optical fiber, increasing the transmission loss of the optical fiber! liI!
Becomes an author. The thermosetting resin forming this thermosetting resin layer 3 is preferably polyimide resin or epoxy resin 7, and these resins have a tensile rupture limit of 0-17 x 10 tAm resin 2 x 1051
/l-1n2, its tensile strength is that of polyimide I (lIm
l, 3-1. OX 10 kg 7 cm , epoxy position 4 resin 703 ky 7 cm , and has excellent strength, so it is a resin suitable for preventing the hillox phenomenon in the metal coating layer 2. Further, thermosetting polybutadiene, aromatic cyano acid ester resin, polybenzimidazole, polyimidazopyrrolone, and the like are also resins suitable for forming the thermosetting resin layer 3.

By the way, such a bare optical fiber 1 and metal coating layer 2
Since each layer of the fiber consisting of the thermosetting resin layer 3 and the thermosetting resin layer 3 is hard, it has high rigidity, and is therefore susceptible to minute bends that cause transmission loss due to external forces. Therefore, on the outer periphery of the thermosetting resin layer 3, a buffering resin layer 4 made of a relatively soft resin, such as silicone rubber, which relaxes and absorbs external forces is provided. This buffering resin layer 4 is relatively thick and has a thickness of 50 to
It is broken down to a thickness of about 50 μm.

In the optical fiber formed in this way, since the optical fiber ridge 1 is protected by the metal coating layer 2, moisture does not act on minute surface defects of the optical fiber ridge 1, making it moisture resistant. Are better. , since the metal coating layer 2 is formed thinly, the transmission loss does not become large as in conventional metallized optical fibers.Furthermore, the metal coating layer 2, which is formed thinly, is thermosetting. Since the resin layer 3 prevents it from peeling off from the bare optical fiber 1, the metal coating I@2 can sufficiently protect the optical fiber ``# line 1'', making it an optical fiber with excellent long-term reliability. Become.

Furthermore, since four buffering resin layers are provided on the outer peripheral surface of the thermosetting resin layer 3, the external force applied to the optical fiber is relaxed and absorbed by the buffering resin layer 4, so that the external force increases transmission loss. There aren't many things.

Next, the present invention will be specifically explained with reference to Examples.

〔Example〕

A metal coating layer 2 made of S+ and having a thickness of 1 μm was formed on the outer peripheral surface of a bare optical fiber 1 having a core diameter of 50 μm and a cladding diameter of 125 μm by CVD. The raw material gas used to form the metallized i-layer 2 was Si)4, the carrier gas was Ma, and the reaction temperature was 700°G. Next, a solvent-dissolved polyimide intermediate was applied to the outer surface of the metal coating layer 2, and the film was squeezed with felt to make a uniform film thickness.
The resin was cured by heating at 0° C. for 3 minutes to form a thermosetting resin 1-3 made of polyimide and having a thickness of 1.2 μm. After this, silicone rubber is coated to form a cushioning resin layer 4 with an outer diameter of 4.
A 20 μm optical fiber was created.

In order to understand the characteristics of this optical fiber, a bare optical fiber with an outer diameter of 125 μm was coated with a thickness of 10 μIT+.
, fr-All coated optical fiber, outer diameter 125μm
The silicone rubber is 420 Atm on the bare optical fiber.

The following three types of tests were conducted for comparison with organic coated optical fiber for general use, which was sequentially coated with 900 μm thick nylon fiber.

First of all, we conducted a tensile strength test at a chuck interval of 10rIL%.
The test was conducted at a strain rate of 10%/min and a number of 52 pieces each, and the probability of breakage was evaluated using a Weipul distribution as shown in FIG. Next, to evaluate the lifespan of the optical fiber,
A static fatigue test was conducted by pulling a fiber with a length of 1 cm with a force of 600 Jcy/vun2, and the time lX1) at the point of breakage was measured, and the results are shown in the table below. In addition, the transmission loss of each optical fiber was determined for wavelengths of 0.85 μm and 1.3 μm,
The results are shown in the table below.

From the results shown in Figure 2, the optical fiber of the present invention has a minimum strength of 2.
．． 4~, it was stronger than the M-coated optical fiber, and the slope of the graph became steeper, indicating stable strength. In the static fatigue test, it showed a value close to that of A and e-coated optical fibers, and is expected to have a long life.Also, the transmission loss was almost the same as that of organic-coated optical fibers, and it was larger than that of jJ-coated optical fibers. It can be seen that the rp has been improved.

Note that the optical fiber of the present invention may be further extruded and coated with a resin such as nylon on the outer peripheral surface of the buffering resin layer 4 and used as a core wire of an optical fiber cable.

As explained above, the optical fiber having a metal coating layer of the present invention has moisture resistance because the bare optical fiber wire or outer peripheral surface is sequentially coated with a metal coating layer, a thermosetting resin layer, and a buffering resin layer. Excellent: jL, long life, low transmission loss, and no increase in transmission loss even when external force is applied.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the optical fiber of the present invention, and FIG. 2 is a graph showing the breakage probability of the optical fiber of the present invention using a Weipul distribution. 1...Hikari Buaiba bare wire, 2...Metal sputum layer, 3...Thermosetting resin layer, 4...
Buffering at lJ layer. Figure 1 Figure 2 Goai@fkg)

Claims (2)

[Claims] (1) A bare optical fiber, a metal coating layer formed on the outer circumferential surface of the bare optical fiber, a thermosetting resin layer formed on the outer circumferential surface of the metal breaking layer, and this thermosetting resin layer. ! 1. An optical fiber having a metal coating layer, comprising a buffering resin layer formed on the outer peripheral surface of a fat layer. (2) The metal coating according to claim 1, characterized in that the thickness of the metal coating layer is 0.1 to 2 μm (1 heat) (the thickness of the hardening resin layer is 0.5 to 3 μm) Optical fiber, with layers.