JPH04119948A - Hermetic coated optical fiber cable - Google Patents

Abstract

PURPOSE:To obtain the hermetic coated optical fiber cable having good airtightness and tensile break strength by coating the outside surface of the optical fiber with the film of carbon or carbon compd. contg. a specific quantity of chlorine atoms. CONSTITUTION:The base material 2 for the optical fiber inserted into a drawing furnace 1 is drawn out as the optical fiber 3. The outside diameter of the optical fiber 3 drawn out of the drawing furnace 1 is measured by an outside diameter measuring instrument 4 and is introduced into a thermal CVD reaction furnace 5. Gaseous raw materials prepd. by mixing acetylene as an example of the carbon compd. and gaseous chlorine are supplied from a gaseous raw material introducing port 6. The gaseous raw materials are thermally decomposed by the heat of a heater 8 and the heat of the optical fiber 3 itself and the chlorine- contg. carbon coating layer (carbon hermetic coating layer) is formed on the outside surface of the optical fiber 3. Further, a resin for protection is applied thereon and cured thereafter, the hermetic coated optical fiber is taken up by a take-up machine 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical fiber cable, and particularly to a hermetically coated optical fiber cable with good airtightness and tensile strength at break for use in optical fiber communications.

[Conventional technology]

When hydrogen or water enters a silica glass optical fiber, the transmission loss of the optical fiber increases. In particular, in submarine optical fiber cables, there is a high possibility that water will enter the optical fiber. Furthermore, when manufacturing an optical fiber cable by coating an optical fiber, hydrogen or water may enter the optical fiber during the process of electroless (chemical) plating.

5 In this specification, an optical fiber refers to a portion consisting of a core and a crand, or a quartz-based glass jacket provided outside the crand as necessary, and an optical fiber cable refers to an optical fiber having a coating or the like. Say what is set.

In order to prevent hydrogen or water from entering the optical fiber, the optical fiber surface is coated with a high-density hermetic coating of an inorganic material, such as carbon or carbon compound, with a thickness of about 500 mm and high hydrogen resistance (airtightness). Optical fiber cables equipped with
08143).

A hermetic coating layer of carbon or a carbon compound formed on the outer surface of an optical fiber by thermal CVD becomes a high-density film containing a fine crystal structure when hydrocarbon gas is used as the main raw material. This carbon hermetic coating layer makes it difficult for hydrogen or water molecules to penetrate into the optical fiber, thereby greatly improving the hydrogen resistance properties and, moreover, improving the fatigue properties of the optical fiber.

[Problem to be solved by the invention]

Optical fiber cable in which an optical fiber is coated with carbon or carbon compound (outer diameter of optical fiber is 125 μm)
The tensile strength at break is about 4 to 5 Kgf. On the other hand, the tensile strength of the original optical fiber without hermetic coating with carbon or the like is 566 to 6. Since the tensile strength is approximately OKgf, the tensile strength at break is reduced by applying a hermetic coating.

The reason for this decrease in tensile strength at break is thought to be as follows. Because high-density carbon has strong covalent bonds, its elongation rate is significantly lower than that of optical fiber glass. Therefore, when a hermetic-coated optical fiber cable is pulled, even a small tensile stress causes a large stress to be concentrated on the hermetic coating, causing a break in the hermetic coating layer, and ultimately leading to breakage of the optical fiber.

As described above, a carbon hermetic coating made of carbon or a carbon compound has contradictory properties in terms of the relationship between airtightness and tensile strength at break.

Decrease in tensile strength of optical fiber cable.

This becomes a problem when handling optical fiber cables, such as during connection work.

Therefore, two objects of the present invention are to provide an optical fiber cable formed with a hermetic coating that does not reduce tensile strength while maintaining hydrogen resistance (airtightness).

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides carbon or carbon compounds containing chlorine having a large atomic radius in carbon or carbon compounds, preferably 1 carbon atom as a hermetic coating material. Approximately 1°Ox 10-'~1.0x1
Carbon or carbon compounds containing in the range 0-'' chlorine atoms are used.

[Function] It has been found that when carbon or a carbon compound contains a chlorine atom with a large atomic radius, a loose structure is formed in which a portion of the covalent bonds between carbons are broken. This loose structure allows for great elongation.

Does not reduce tensile strength. However, when the content of chlorine atoms increases, the structure becomes too loose and hydrogen resistance decreases. For example, even if it is possible to prevent water from entering an optical fiber, it is insufficient to prevent hydrogen from entering.

According to experiments, the content of chlorine atoms that satisfies both the above-mentioned airtightness against hydrogen and tensile strength at break is approximately 1.0x10-' to 1.0x10-2 per carbon atom.
A range of 100% was suitable.

(Embodiment) FIG. 1 shows a schematic configuration of a carbon hermetic coated optical fiber cable manufacturing apparatus as an embodiment of the present invention.

A method of manufacturing a hermetic coated optical fiber cable according to an embodiment of the present invention using this manufacturing apparatus will be described.

An optical fiber preform 2 inserted into a drawing furnace 1 is drawn out as an optical fiber 3. The optical fiber 3 has a core with a diameter of 10 μm and a cladding formed on the outside thereof, and the outer diameter of the optical fiber 3 is 125 μm. Drawing furnace 1
The outer diameter of the optical fiber 3 that has been pulled out is measured by an outer diameter measuring device 4 and then introduced into a thermal CVD reactor 5.

The thermal CVD reactor 5 has a raw material gas inlet 6° at the top and an exhaust lower at the bottom, and a heater 8 is provided around the thermal CVD reactor 5. From the raw material gas inlet 6, acetylene (Czt(z)), which is an example of a carbon compound, and chlorine gas (
A raw material gas containing CI□) mixed at six levels of mixing ratio was supplied. This source gas is thermally decomposed by the heat of the heater 8 and the heat of the optical fiber 3 itself, and a carbon coating layer with different chlorine contents, that is, a carbon hermetic coating layer, is formed on the outer surface of the optical fiber 3. The optical fiber 3 on which this carbon hermetic coating layer is formed is called a hermetic coating optical fiber 3A.The thickness of the carbon coating layer attached to the optical fiber 3 is, for example, 400.

The flow rate of the source gas introduced from the source gas inlet 6 is adjusted.

The carbon hermetically coated optical fiber 3A is introduced into a resin applicator 9, and a protective resin is applied to its surface.

It is then passed through a resin hardener 10 to harden the resin coating over the carbon hermetic coating layer. The outer diameter of the optical fiber cable 3B having this resin coating is 0.2
It is 5mm. The optical fiber cable 3B is wound as a core wire by a winder 11.

A cross-sectional view of the above-mentioned optical fiber cable 3B is shown in FIG. A core 31 with a diameter of 10 μm in the center. There is a quartz glass optical fiber 3 with an outer diameter of 125 μm on which a cladding 32 is formed, and a carbon hermetic coating layer 33 containing 400 chlorine atoms is formed on the outer surface, and a protective resin A coating 34 is formed and has an outer diameter of approximately 0.
．． A 25 mm optical fiber cable 3B is configured. The thickness of the hermetic coating layer 33 can be set to an appropriate thickness as shown in Table 1 below.

Table 1 shows the characteristics of optical fiber cables when the amount of chlorine atoms contained in the carbon hermetic coating layer 33 is varied.

(The following is a blank space) Table 1 The chlorine content per carbon atom in Table 1 is a value measured by secondary ion mass spectrometry and Auger electron spectroscopy. The film thickness indicates the thickness (in thickness) of the carbon hermetic coating layer 33, and is the result of measurement using a transmission electron microscope. The breaking strength indicates the tensile breaking strength (Kgf), and shows the results of a tensile test on five optical fiber cables each having a length of 10 m at a tensile speed of 5%/min and a median value of n=19. The dynamic fatigue coefficient (n value) is.

Each pulling speed at n=10 is 0°5.1
．． The results are shown at 0, 5, and 10.50%/min.

Hydrogen resistance is 2 in hydrogen, 1 atm, 75°C atmosphere.
Transmission loss (d
B/Km).

In Examples 1 to 3, the tensile strength at break is 5.7 to 5.8 Kgf, and no decrease in the tensile strength at break due to the attachment of the carbon hermetic coating layer 33 is observed. Furthermore, there is no deterioration in transmission loss and airtightness is maintained. Furthermore, while the dynamic fatigue coefficient is good, Comparative Example 1 which does not contain chlorine atoms
．． Comparative Example 2, which has a low chlorine atom content of 5.0x10-', has a low tensile strength at break. Furthermore, in Comparative Example 3, which has a high chlorine atom content of 2.0×10 −2 , hydrogen resistance decreases and transmission loss increases.

From the above results, it has been found that the suitable chlorine content that satisfies hydrogen resistance, tensile rupture strength, and dynamic fatigue coefficient is approximately in the range of 1.0x10-' to 10χ10-2 per carbon atom. Ta.

In the above embodiment, a case was described in which the outer surface of the carbon hermetic coating layer 33 was coated with resin, but since it is also used as a conductive optical fiber cable, a conductive metal coating or the like is formed on the carbon hermetic coating layer 33. You may. When the conductive coating is formed on the carbon hermetic coating 33 by electroless plating or the like, the hermetic coating layer 33 eliminates the possibility that hydrogen or water will enter the optical fiber when the optical fiber is immersed in an electrolyte. .

Furthermore, although a case has been described in which acetylene is used as the carbon compound in the above embodiment, other carbonized metals may be used.

〔Effect of the invention〕

As described above, according to the present invention, by containing an appropriate amount of chlorine atom per carbon atom, the optical fiber can maintain airtightness against hydrogen or water intrusion, while maintaining tensile strength at break. We were able to manufacture a hermetic coated optical fiber cable with good fatigue properties.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of an apparatus for manufacturing a hermetic coated optical fiber cable of the present invention. FIG. 2 is a cross-sectional view of a hermetically coated optical fiber cable according to an embodiment of the present invention manufactured by the apparatus of FIG. 1. (Explanation of symbols) 3... Optical fiber. 3A: Hermetic coated optical fiber 3B: Optical fiber cable. 31...Core. 32...Clad. 33... Hermetic coating layer. 34...Resin coating. Patent applicant: Furukawa Electric Co., Ltd. Agent: Patent attorney: Takahisa Sato

Claims (1)

[Claims] 1. Approximately 1.0x10^-^5~ for one carbon atom
A hermetic coated optical fiber cable characterized in that the outer surface of the optical fiber is coated with a film of carbon or carbon compound containing 1.0x10^-^2 chlorine atoms.