JPS5946605A - Optical fiber - Google Patents

Abstract

PURPOSE:To improve long-term reliability and to enable the use under adverse environmental conditions by storing optical fiber strands coated thereon with metallic layers in a metallic pipe, and filling ceramics in the gaps among the strands thereby constituting an optical fiber. CONSTITUTION:A unit of an optical fiber cable is manufactured from three optical fiber strands 31 each coated thereon with a metallic layer 32 and further coated thereon with a ceramic layer 33, a central tension member 41, and three feeders 51. Each strand 31 having 50mum core diameter and 150mum clad diameter is used, and each layer 32 is formed by coating WSi (tungsten silicide) and forming the same to 2mum thickness. The layer 33 consists essentially of Al2O3 and has 2mm. outside diameter. These members (three optical fiber strands, one tension member and three feeders) are assembled in a copper pipe 61 of 10mm. outside diameter and 6mm. inside diameter, and the gaps in the pipe 61 are filled with a ceramic layer 71 of Al2O3.

Description

[Detailed description of the invention] This invention relates to the structure of optical fibers.

Optical fibers are generally not used in the form of a bare wire consisting of only a core and a cladding; in fact, they are covered with an organic substance to form a core fiber, or one or more core wires are used. They are used together as a cable.

In this specification, optical fibers configured as core wires or cables are simply referred to as optical fibers.

By the way, optical fibers are processed under high pressure and at high temperatures.
When used in adverse environmental conditions such as high humidity, optical fibers coated with organic substances or cables containing such optical fibers may be decomposed and the organic substances may release water-containing substances, causing the optical fiber to deteriorate. It has a negative effect on the line itself. Therefore, in cases of such adverse environmental conditions or cases where high long-term reliability is required, it is considered appropriate to use optical fiber coated with a metal layer, but it may bend due to high pressure. powerless against it.

In view of the above, this invention consists of an optical fiber coated with a metal layer, housed in a metal pipe, and the gap filled with ceramic to form an optical fiber. An object of the present invention is to provide an optical fiber that can be used under adverse environmental conditions without causing microbending.

The optical fiber according to the present invention does not include an optical fiber whose outer surface is coated with a metal layer, a metal pipe containing the optical fiber, and a ceramic filled in a gap within the metal pipe. , which has excellent long-term reliability because it does not contain organic substances. In addition, since ceramic is hard, it does not cause microbends in the optical fiber even when subjected to pressure, and the pressure applied to the metal pipe is transmitted to the optical fiber through the ceramic. Since the wire functions as a structural material that supports the metal pipe from the inside, it can prevent the metal pipe from being destroyed by high pressure. Therefore, the strength is significantly increased compared to simply inserting an optical fiber (or core wire) into a metal pipe. Therefore, it can be used reliably for a long period of time even under adverse environmental conditions such as high temperature and high humidity.

Here, the optical fiber is mainly composed of quartz-based material, and the metal coated on the optical fiber is tungsten, molybdenum, etc. Titanium, aluminum, etc. are used. The coated metal layer is for preventing the intrusion of moisture, and its thickness is preferably thin for low loss and thick for protection.

Ceramic is Si (17, Al!203, Zr02
, i rU2 , Ge (A high-temperature refractory such as J2 is used. Especially when used in a high-temperature environment, one that does not contain alkali metal oxides is preferable.

Next, embodiments of this invention will be described.

<Example 1> As shown in FIG. 1, the diameter of the core 11 is 50 μm, the diameter of the cladding 12 is 200 μm, and the refractive index difference between them is 1%.
The outer surface of a quartz-based graded index optical fiber strand 1 is coated with Ti metal to form a metal layer 2 with a thickness of 10 μm, and Ai! 20
A ceramic layer 3 was formed by coating and baking a ceramic containing 383% Si0 and 27% Si0, and the outer diameter of this ceramic layer 3 was set to 1.5 mm. And on top of this, outer diameter 3
A core wire was made by covering a copper pipe 4 with an inner diameter of 1.5 mm and an inner diameter of 1.5 mm.

Using this core wire, a submarine cable was fabricated as shown in Figure 2. The outside of the core wire (specifically, the copper pipe 4
Copper wires 5 with a diameter of 2 mm were wrapped in two layers of 1 J on the outside of the tube, and a copper pipe 6 was attached and fixed from the outside. Further, this was inserted into a copper pipe 7 having an outer diameter of 15 mm and an inner diameter of 11 mm, and a sheath 8 was applied thereon. In this way, the outer diameter is 20m
A cable of m was made.

The initial loss of this cable was 2 dB/Km at a wavelength of 1.3 μm. This cable was placed under pressure of 200 atmospheres, but the above loss did not change. Further, this cable was put into water at 150° C. and used under pressure, but no change was observed in its characteristics.

<Example 2> As shown in FIG. 3, three optical fiber strands 31 coated with a metal layer 32 and further coated with a ceramic layer 33 and a central tension member 4 are used.
1 and three feeder lines 51, an optical fiber cable unit was manufactured. The optical fiber wire 31 has a core diameter of 50
μm, cladding diameter 150 μm, metal layer 32
was coated with WSi (tungsten silicide) to a thickness of 2 μm. Ceramic layer 33! 2(
．． )3 as the main ingredient, and the outer diameter is 2 ml. The tension member 41 used was a copper wire with an outer diameter of 2 mm, and the power supply line 51 was a Pt alloy wire 52 covered with an insulating layer 53 of Al203 and had an outer diameter of 2 mm. These (3 optical fiber wires, 1 tension member, 3 power supply lines) were connected to a copper pipe 6 mm in outer diameter and 6 mm in inner diameter.
1, and the gap inside this copper pipe 61 is AQ2U3.
It was filled with a ceramic layer 71 of. This is how I made the cable unit.

Further, although not shown in the drawings, this unit was covered with two layers of twisted steel wire having a diameter of 3 mm, and a sheath was applied to this for use as an underground exploration cable. We conducted underground exploration at a depth of 5km to 10km, but the loss was 1.3μm at a wavelength of 1.3μm.
It was 2 dB/km, and was able to perform a sufficient transmission function.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an optical fiber according to a first embodiment of the present invention, FIG. 2 is a sectional view showing a submarine cable using the same optical fiber, and FIG. 3 is a sectional view showing a submarine cable according to a second embodiment of the present invention. FIG. 2 is a cross-sectional view showing an example optical fiber cable unit. 1, 31... Optical fiber wire 2, 32... Metal layer 3, 33. 7] Ceramic, black layer 4, G, 7, +
31...Copper pipe 5...Steel wire 8...Sheath

Claims (1)

[Claims] (1) It is characterized by consisting of an optical fiber whose outer surface is coated with a metal layer, a metal pipe containing the optical fiber inside, and a ceramic filled in the gap within the metal pipe. optical fiber.