JPS59129803A - Metal coated optical fiber - Google Patents

Abstract

PURPOSE:To facilitate coating by a dipping method and to improve corrosion resistance by using a specified alloy for coating the outer circumference of a bare optical fiber. CONSTITUTION:An alloy consisting >=70at% Au or Pt and an element of group IIIB, IVb, or Vb of the periodic table is used for coating the outer circumference of a bare optical fiber. Its alloy compsn. is selected from combinations of Au and Al, Au and In, Au and Si, Au and Ge, Au and Sb, Pt and Sb, Pt and Si, etc. Since these alloys can be easily applied to the fiber by the dipping method even at low temps., thermal shock given to the fiber is reduced and does not damage it. The alloy is not corroded under corrosive environmental conditions, and therefore it can enhance reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber coated with a hexagonal metal by applying an alloy complex to the outer peripheral surface of a bare optical fiber.

Optical fibers have features such as broadband, low loss, and high capacity, and their uses are being expanded.

By the way, when manufacturing optical fibers, great care is taken because minute scratches on the surface of the bare optical fibers will significantly reduce the strength. However, the formation of microscopic surface defects on the surface of the bare optical fiber cannot be prevented.

As a result, minute surface defects react with moisture in the air,
It is necessary to protect the surface of the bare optical fiber by coating it to prevent it from becoming larger. Usually, it is coated with silicone rubber or the like for this purpose, but if further water resistance and long-term reliability are required, a hermetic coating of metal or ceramics (such as Si3N4) is used.

Methods for coating bare optical fibers with metal include chemical vapor deposition (C, V, D,), physical vapor deposition (P, V, D,),
Spunter method, dip method, etc. are used. Among them, the dipping method is considered to be an industrially suitable method for metal coating because it can form a thick coating of 2 to 30 μm continuously at a cylinder speed and is simple.

However, since the dipping method coats the outer periphery of the bare optical fiber with metal by passing the bare optical fiber through molten metal, the melting point of the coated metal is the temperature that the bare optical fiber can withstand. Must be less than or equal to. 5i
In the case of bare optical fiber whose main component is SiO2, the melting point of SiO2 is approximately /700°C and the strain point is approximately /100°C. Considering safety, the melting point of the metal coating the bare optical fiber is It is desirable that the temperature is 200°C or less. Therefore, the metal that can be coated by the dip method is Zn.
, InXPb, Sn, At, and alloys thereof. However, since all of these have poor corrosion resistance, conventional metal-coated optical fibers manufactured by the dip method have concerns about corrosion of the metal coating itself.

The present invention has been made in view of the above circumstances, and aims to provide a metal-coated optical fiber in which a metal coating layer, which has excellent corrosion resistance and can be easily formed by a dipping method, is applied to the surface of a bare optical fiber. This is the purpose.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 7 shows an example of a metal-coated optical fiber of the present invention, and reference numeral 1 in the figure indicates a metal-coated optical fiber. This metal-coated optical fiber 1 has a metal coating layer 3 formed on the outer peripheral surface of a bare optical fiber 2 mainly made of 5i02. This metal coating layer 3 is made of an alloy of 70 at % or more of Au or PT and elements classified into the 1llb group, the Vb group, and the Vb group in the periodic table of 30 at % or less.

Au is the safest metal against oxidation, does not react with air or water even at high temperatures, is stable against acids, and will only dissolve in special acids such as aqua regia and selenic acid. . Also,
Like Au, Pt is stable, does not combine directly with oxygen, and is only soluble in aqua regia, which is a special acid. However, such chemically stable substances often have high melting points, and Au1
In the case of Pt, its melting point is Au (1063℃), Pt (/
767° C.), and therefore it is impossible to coat the bare optical fiber 2 with Au or PT by the dip method. However, it is generally known that adding impurities to a substance lowers its melting point, and it has been confirmed that the melting point of A u %pt also decreases when other elements are mixed in to form an alloy. . Among these, alloys of Au or PT with elements of the ILB group, VB group, and VB group have a remarkable decrease in melting point in a range where the content of ILB group, VB group, and VB group elements is small. An alloy to which the above elements are added is preferable as a metal to be coated by the dip method. Especially A u -A Z XA u -I n
1A u -S i NAu-Ge, Au-8n, Au
-8b, Pt-8b and Pt-8t, as shown in Figures 7(a) to (h),
This alloy is suitable for the metal coating layer 3 of the present invention because it has a minimal eutectic point in a range where the t content is high and also has good corrosion resistance. Further, when manufacturing the metal coated optical fiber 1 of the present invention, since the metal coat layer 3 is a very thin film, the alloy coated on the bare optical fiber 2 is quickly cooled, and the structure of the metal coat layer 30 is extremely small. It becomes a fine structure. Therefore, if the content of Au or pt in the alloy is 7t7at% or more, Au-? Metal coating layer 3 with excellent corrosion resistance without significantly impairing the corrosion resistance obtained from the chemical stability of Pt
becomes.

Furthermore, as can be seen from the phase diagram shown in Fig. 2, Au
Alternatively, if the ratio of pt to other elements is changed, the temperature at which the alloy melts changes accordingly. By using this property,
By changing the ratio of Au or pt to other elements <ht, In, st, etc.), the heat resistance of the metal coating layer 3 can be freely selected between the eutectic point and the melting point of the pure substance. It is.

For example, according to the Au-At0 state diagram shown in Figure 2(a), the ratio of the Au content in the alloy is from 100 &t
When sequentially changing up to ♂at%, Au-A
The melting point of Alloy A is 12 from 7063℃! 'C along the liquidus line. However, in consideration of the heat resistance of the bare optical fiber, it is desirable that the melting point of the alloy is ♂θO°C or lower.

FIG. 3 shows the main parts of the apparatus used to manufacture this metal-coated optical fiber 1.

Au or pt of 70at% or more and ll of JOat% or less
An alloy consisting of elements of group B, group VB, and group VB is charged into a melting furnace 5 of a dip device 4 and melted at a high temperature. The molten alloy flows into a holding furnace 6 connected to the melting furnace 5, where its temperature is regulated, and further flows into a dip section 8 through a narrow conduit 7.

The interior of these is maintained in a reducing or neutral atmosphere. The dip part 8 is made of heat-resistant materials (metals, oxides, borides, carbides, nitrides, quartz glass, carbon, alumina,
It is made of metal (such as platinum) and has holes 9° and 10 of a predetermined size in its upper and lower parts, respectively. 5iOz
The bare optical fiber 2 spun from the optical fiber base material 11 made of The metal coated optical fiber 1 is coated with the metal coat layer 3 formed thereon.

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

[Example 1] An optical fiber base material 11 made of a quartz-based material and having a core doped with Ge and having a refractive index difference/% is spun while being heated to 2200°C to form an optical fiber with an outer diameter of 7.23 μm. It was made into a bare A2. This bare optical fiber a2 was introduced into the dip part 8 of the dipping device 4, and coated with an alloy of Au94 having a composition of 514 wt% base l to a thickness of 2θ μm. The diameter of the hole 9 at the top of the dip part 8 of the dipping device 4 is 1, and the diameter of the hole 10 at the bottom is 0j.
Bare optical fiber 2 passing through dip section 8 in tran
The speed of the train was 30 meters per minute. Further, the temperature of each part of the deimping device 4 is as follows: the melting furnace 5 is set at 000°C, and the holding furnace 6 is set at 39°C.
0°C, dip part 8 is maintained at 3i0°C, dip part 4 is
The depth of the molten alloy stored in was kept at just over /rran.

The transmission loss of the Au-8i metal-coated optical fiber 1 made by the above operations is as follows: when the transmission loss of the silicone rubber-coated optical fiber is for light with a wavelength of ays μm,
It was 2♂dB/- compared to B/b.

In order to confirm that the corrosion resistance of the Au-8t metal-coated optical fiber I was improved, an organic foot was prepared in which a bare optical fiber with an outer diameter of 2Jμm was sequentially coated with silicone rubber to a thickness of 4×20μm and nylon to a thickness of 200μm. An optical fiber with a thickness of θμm is attached to a bare optical fiber with an outer diameter of 7.2μm.
Sn metal-coated optical fibers coated with a metal consisting of n were subjected to the following conditions (1) to (3) for comparison, and then their tensile strength was examined.

(20 hours (2) in distilled water at 11 μθ℃) 2 (17 hours (3) in tap water at 0℃)
Seventy optical fibers were each placed in tap water at a temperature of
I did it with m.

The results are shown in the table below.

(Unit: kg/piece) When the Sn metal-coated optical fiber was immersed in μO°C tap water for 30 days under the condition (3), corrosion was observed in the Sn metal coating layer. In the case of the Au-5i metal coated optical fiber 1, no corrosion was observed in the Au-8i metal coat layer 3, and as shown in the table above, there was no significant decrease in tensile strength.

Furthermore, when the Au-8i metal-coated optical fiber 1 and the Sn metal-coated optical fiber were immersed in JN dilute hydrochloric acid, 3N dilute sulfuric acid, and 3N dilute nitric acid, the Sn metal coating layer 3 showed a remarkable change even after 4t♂ hours had passed. was not seen.

[Example 2] Using the same apparatus as in Example 1, a bare optical fiber with an outer diameter of /j01En was coated with Au at 7 wt% and Si at 3 wt%.
The temperature of the melting furnace 2 is 100℃, and the temperature of the holding furnace 3 is rao.
℃, and the dip part 4 was set to ♂θo℃. Further, the speed at which the bare optical fiber 2 passed through the dimpled portion 4 was 26 m/min.

The Au-8t metal-coated optical fiber prepared by the above procedure was placed under the environmental conditions (11 (2) and (3)) shown in Example 1, and then subjected to the same tensile test as in Example 1. As a result, the samples were immersed in tap water at Hiro θ℃ for 30 days (3
), no significant decrease in strength was observed as in the results of Example 1.

Furthermore, when the tensile strength of the Au-8t metal coated optical fiber 1 was measured at different temperatures, it was 3! No change was observed up to θ°C. Furthermore, this! ;'7wt Chi's Au and Jw
The temperature at which the metal coating layer 3 made of Si was melted was 70°C.

As explained above, in the metal-coated optical fiber of the present invention, the outer peripheral surface of the bare optical fiber is coated with an alloy consisting of 70 at% or more of AU or PT and elements of the MB group, the ■B group, and the VB group. The metal coating layer has excellent corrosion resistance, and even in corrosive environments, the metal coating layer will not corrode and affect the protection of the bare optical fiber, making it an optical fiber with excellent long-term reliability. becomes. Furthermore, when the metal coating layer of the metal coated optical fiber of the present invention is formed by the dipping method, it can be formed at a low temperature, so there is less thermal shock given to the bare optical fiber. It won't hurt. Furthermore, by changing the content of elements of the mb group, the b group, and the vb group in the alloy, the melting point of the alloy can be changed, so the desired heat resistance can be imparted to the metal coating layer of the metal coated optical fiber. can do.

[Brief explanation of drawings]

Figure 7 is a cross-sectional view of a metal coated optical fiber, Figures 2(a) -
01) is a phase diagram of some alloys that form metal coating layers (
a) is A11-At, (b) is Au-In, (c) is A
u-8i, (d) is Au-Qe, (e) ijA u −
S n, (f) is Au-8b, (g) HPt-8b,
(h) UPt-8i. FIG. 3 is an explanatory diagram of a dipping device for forming a metal coating layer of a metal coated optical fiber. 1... Metal coated optical fiber 2... Bare optical fiber 3... Metal coated layer Figure 1! Figure 3 ++ - Figure 252...% AU a-%
InW+%

Claims (1)

[Claims] l In a metal-coated optical fiber in which a metal coating is applied to the outer peripheral surface of a bare optical fiber, the coated metal is 70 at%.
The above gold (Au) or platinum (Pt) and the mb group of the periodic table,
(2) A metal-coated optical fiber characterized by being alloyed with elements of the B group and VB group. 2. The combination of alloy components is Au and Al, Au and In. Au and Si, Au and Qe, Au and 5n1Au and 3b. 8. The metal-coated optical fiber according to claim 7, wherein the metal-coated optical fiber is selected from the group consisting of pt and sb and pt and Si.