JPS5986017A - Connecting method of metal-coated optical fiber - Google Patents

Abstract

PURPOSE:To increase the connection strength of a connection part and to reduce an increase in light loss by removing the metallic coatings of optical fibers and forming a connection end surface newly, butting those connection end surface against each other and connecting them by fusion, and re-forming a metallic coating at the coating removal parts. CONSTITUTION:Tips of metal-coated optical fibers 1 and 1 are dipped in a solution of hydrochloric acid, acetic acid, or their mixed acid to remove metallic coatings. Then, those removal parts 5, 5 are washed and dried and then cut to obtain new smooth end surfaces 8, 8. Those end surfaces 8, 8 are connected together by fusion in an accurate abutting state. A metallic coating is re-formed by vapor deposition at the coating removal part 10 of the connected metal-coated optical fiber 9. Thus, the welding operation of optical fiber bare wires is performed smoothly and coating metal is prevented from mixing with a fiber fusion part during fusion connection, so high connection strength is obtained, reliability is superior for a long period, and an excellent connection with a less increase in light loss is made.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for connecting metal coated optical fibers.

Metal-coated optical fiber has silicon (
Si), aluminum (A e ), M (Cu) silver (
Ag), nail 1 (Sn), lead (Pb), indium (In
), etc., and the bare optical fiber is protected by this metal coating, which has excellent water resistance and long-term reliability. However, in the fusion splicing of such gold-curved optical fibers, various problems will arise if the method is used in the same manner as for ordinary optical fibers, as described by Kaneda et al. First, for fusion splicing, it is necessary to obtain a new smooth splicing end surface. To do this, normally a suitable scratch is made on the outer circumference of the bare optical fiber, and bending stress is applied to this part to cause brittle fracture, and the bare optical fiber is cut to create a connection end surface. In the case of optical fibers, it is difficult to penetrate the metal coating and make appropriate scratches on the outer periphery of the bare optical fiber, making it difficult to form new smooth connection end faces. Furthermore, even if it is possible to obtain a new, smooth connection end face by cutting a gold-4 coated optical fiber while it is metal-coated, the metal-coated optical fiber is still coated with metal up to the cut end, so this metal-coated optical fiber cannot be fused. When connecting, do you melt the bare optical fiber? )l
! Optical fiber +
At the same time as 'l li+, the metal coating is also heated.

Therefore, even if the metal of the coating combines with oxygen in the air or fusion splicing is performed in an inert atmosphere, the oxygen (02) of silicon dioxide (SiO2) in the bare optical fiber and the metal of the coating may combine to form metal oxides, and the metal coating will no longer be able to adequately protect the bare optical fiber. Moreover, if the bare optical fiber and the metal coating are heated at the same time,
The metal of the coating melts and mixes into the optical 7-eyeper bare wire, resulting in disadvantages such as a decrease in the strength of the bare optical fiber, a decrease in the purity of the bare optical fiber, and an increase in optical loss.

The present invention was made in view of the above-mentioned circumstances, and it is possible to easily form a new smooth connection end surface at the end of a bare optical fiber, and furthermore, the connection part of the metal coated optical fiber can be sufficiently large. This provides a method for connecting metal-covered optical fibers that has high intensity and reduces the increase in light f (1 loss) at the connection point. Below, an example of the connection method of the present invention will be explained with reference to the drawings. FIG. 1 shows the method for connecting metal-coated optical fibers according to the present invention in the order of steps. The metal coated optical fiber 1.1 is a bare silica core blood type optical fiber 2.2 whose main component is silicon dioxide (SIO2).
Silicon (Si) and aluminum oxide A (A e
), @4 (Cu), silver (A g
), (11jr (S n ), i(T'
b), made of metal such as indium (In), film thickness 05
A metal coating of about 3.3 to 30 μm was applied for 8J. This metal coating 3 is formed by chemical vapor deposition method (C, V, D
), molten metal immersion α method or physical vapor deposition method tp, y, n
), sputtering, etc. When such a metallic optical fiber 1.1 is connected, the metal coating 3.3 is first removed. As shown in FIG. 1(l), a pair of metal-covered optical fibers 1.
1, its end several centimeters is immersed in a solution 4 to remove the metal coating 3. This solution 4 contains 3 to 30
%(7))&(G('2(HCe), 6xiaoac(
)INOs) One of these acids is used,
'It is preferable to perform immersion for about 5 to 10 minutes at room temperature. Here, hydrochloric acid (IT C13), b'l'Jm (t
TNO3), A/'+IG;lt+1mtl (7)
The reason why a mixed acid is used in the solution 4 is that silicon dioxide (S 10x), which is the main component of Hikari 7 Ainokushi 2, is acidic oxidized.
As shown in the table below, it is hardly attacked by other acids except hydrogen fluoride (ml < I-IF), but the metals that form the film (Si, A/, Cu, Ag,
Sn, I'b, In, etc.) are all M,! : This is because it reacts and dissolves, and among acids, strong acids are practical because they can dissolve in a short time.

However, treatment with sulfuric acid (H7S 04 ) in a strong 112 is not preferred since SOs ions may remain in the immersed part of the metal-coated optical fiber 1.1. Nitric acid (HNOs) and (m acid (T(C/)) do not have this problem because they are volatile.

Table Gold and box-coated optical fiber 1.1 from which the metal coating 3.3 at the end has been removed by the solution 4 for reducing the amount of quartz glass by moromi, as shown in FIG. 1(C).
The removed portion 5.5 of the metal coating 3.3 is thoroughly cleaned,
dried. Bare optical fiber, obtained in this way?
A new smooth end face is required for the JE connection, but in this state the proboscis 6.6 is often dirty or Lfj is not smooth due to the environment in which the end face 6.6 was placed. Therefore, as shown in Figure 1 (Q),
A scratch 7.7 of appropriate depth is made on the outer periphery of the removed part 5.5 where the bare optical fiber is exposed, and bending stress is applied to this part to prevent it from being cut by brittle dust. Then, a new smooth connection 9a flJ! as shown in FIG. 1(d) is made.
8.8 is formed.

The two new connection end faces 8.8 obtained in this way are in a J4 shape in which they are butted against each other with the centers 111h a+ of the bare optical fibers exactly aligned, as shown in FIG. 1(e). ini' are connected by a conventional fusion splicer.

Next, the metal ij that was connected to this connection; ? The removed portion 10 of the l:f optical fiber 9 and its surroundings are processed by chemical vapor deposition (CN', D), molten metal dipping, sputtering, and vapor deposition (CP, V, D), etc. The metal coating is re-formed. Preferably, the metal to be removed is of the same type as the metal of the removed coating. In addition, according to the chemical vapor deposition method (CC, VJ)), the coatings formed by these methods are 0.5 to 32 ml.
%+gold PS According to dipping method 5-30 μm1 By sputtering 05-1 μm1 Physical vapor deposition method CP, Vl, D
), the film thickness is approximately 1 μm.

At this time, metal cover ti! 1. When wearing a JUV, metal clothing is applied to the entire part of the body that is covered with metal.
, 1F film removed portion and unremoved portions of the film on both sides: The metal film is re-formed in < minutes.

Therefore, the re-formed metallization 1i, -11 has an outer shape as shown in the 11th month (f).
In the area where the rays are concentrated, the thickness of the IJf,j is slightly thicker.

FIG. 2 illustrates a method of reshaping metallization IE't 11. Referring to these figures 7.1. +
, empty evaporation method [Figure 2 (a)], bipolar sputtering method [
Figure 2(b)), and '? Gas phase FIN'14':
(AP 215.U(c)) K.

The reshaping of the metal coating will be explained below. When forming the metal coating 11 by vacuum evaporation method, a vacuum container 12 is used.
The part to be removed 10 of the metal optical fiber 9 connected to the metal optical fiber 9 is accommodated, and gold is removed from the evaporation source 13 under a vacuum condition of about 1041 Torr. f; atom covered 1j; X! Vapor deposition is performed centering on the removed area. In addition, in the case of using the bipolar sputtering method, the vacuum container 14 accommodates the connected metal + end optical fiber sheath removal section 10, and after the inside of the vacuum container 14 is evacuated, gas is introduced and a suitable amount is applied. pressure (1~10-'To
rr culm IU).

By using the sputtered gold as the cathode 15 and causing a glow discharge between it and the anode 16, Inζ゛! A film is formed around removed sounds 1 to 10. Next, in the case of using the chemical phase precipitation method, the sealed container 17 houses the optical fiber 9 to be coated F'A (10) to be connected and the metal layer 9 is removed, and this is poured into the outer layer of the sealed container 17. i] is applied by the high-frequency heating coil 18 to this airtight container 17,
A reaction gas containing all compounds such as monosilane (S i H4) and monogermane (Gθ engineering 14) is fed. This metal compound becomes a metal through a gas phase chemical reaction, and adheres to the surface of the connected metal-covered optical fiber 90 to form a metal-covered IJ7;f11.

In this way, in this connection method, the bare optical fiber 2 is cut at a portion from which the metal coating 3 has been removed in advance, and the connection U
Since the 1^) surface is formed, a new smooth connecting end surface 8 can be obtained. In addition, since the metal coating 3 is removed and the optical fibers 2 having a new connection end face 8 are fusion spliced, metal atoms are melted into the optical fiber probe 2 during fusion splicing. I! There is no contamination, and the connection part has high connection strength and long-term reliability.1, Optical 11.1
There is also little increase in losses.

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

〔Example〕

The outer diameter of the optical fiber loincloth 12 is 1257 fm, metal J...
:.

The fiber 1 was connected to a metal sheath in which the film 3 had a thickness of 1 μm and was made of Ae to lJ9. 110% HCg solution 4), the tip of the optical fiber 1.1 is connected to the metal jacket CW of the optical fiber 1.1
5°CT 3 minutes? 'N rt,f shite1. Ne's gold times? fk II'43.3 was removed. Thoroughly wash and dry this removed part 5.5, or use normal cutting 1.
! A new smooth IY cut '11 edge 8.8 was obtained by cutting [17i] between the removal parts 5.5 and 5.5 using a machine. The two PJ' connecting ends frij8.8 obtained in this way are pressed against each other, and connected with an arc, and then connected with ζ by means of a thread.
Me L, ta. Next, the coating removed part 10 of the optical fiber 9 was placed in a bipolar sputtering device and sputtered at 5 x 10-'Torr% 5 mA.
Generate plasma with ion current to deposit Ae at 15%
A coating thickness of 0.8 μm was obtained. Connect the aluminum-coated optical fibers using the above procedure, and connect 100 samples.
I created this book. When the breaking strength of these pieces was measured, the lowest value was 4.2 kg and the average value was 7.0 kg.

As explained above, the method for splicing metal-coated optical fibers of the present invention is applicable when fusion-splicing bare optical fibers (gold coated fibers with a gold film around the circumference). , remove the gold and bow coating of the optical fiber, form a new connection surface in this part, and fusion splice with the T7 connection end surfaces butted against each other. Therefore, when making a cut on the outer periphery of a bare optical fiber, it is possible to make a cut directly on the optical fiber ridge line, rather than inserting a metal coating on the outer periphery of the bare optical fiber. Scratches can be easily made, and therefore a good new smooth end face for connection can be prepared.Also, when fusion bonding optical fibers and wires together, a metal coating can be formed. Metal atoms are not melted and mixed into the bare optical fiber, high connection strength is obtained, and long-term reliability is excellent] 1. Good connection with little increase in optical tp loss can be obtained. Furthermore, since the metal coating is re-formed at the connection part, the bare optical fiber at the connection part is sufficiently protected and the original excellent characteristics of the metal-coated optical fiber can be maintained. F
The gold-plated optical fibers connected in a V-connection by the J optical fiber connection method have less increase in optical loss, have high connection slack, and have excellent long-term reliability.

[Brief explanation of the drawing]

1(a) to 1(f) show the connection method of the present invention in order. 2 [View, Figure 1 (b
) is a perspective view showing the state where the connected KaR is immersed in the metal coating σ), and Figure 1 (c) is the state where the metal coating of the 4 parts has been removed. Strabismus 1a showing
Figure 1(d) is a perspective view showing a state in which a connecting hook is formed on the end portion to be joined, and Figure 1(e) is a perspective view showing a state in which a bare optical fiber is connected. , 1n(f) is a cross-sectional view showing the state in which the metal coating has been remolded, and FIG. 2<, )
- (0) are all schematic drawings of the shelf 1 of the equipment used for reshaping the metal drum F, and Fig. 2 (a) shows the vacuum evaporation equipment (4, 2nd
Figure (b) shows a two-pole sputtering device r1, and 2M(0) shows a chemical vapor deposition device. 1...Metal coated F1 optical fiber, 2...Optical fiber line, 3...Gold m coating, 4...-Dissolving solution, 5...Removal part , 6... end face, 7...
...Scratch, 8...Connection &t'' end face, 9...Connected gold r coating (f optical fiber, 10... Film removal part, 11... Gold Layer coating 0 Applicant I Taikura Electric Cable Co., Ltd. - Figure 1

Claims (1)

[Claims] 1. When fusion splicing metal-coated optical fibers having a metal coating formed on the outer periphery of the optical fiber, after removing the metal coating from the optical fibers to be spliced, a new A method for connecting metal-coated optical fibers, which comprises forming a connection end surface, fusion splicing with the connection end surfaces abutted, and then re-forming the metal coating on a1 (removal of the metal coating. Z metal coating lit) A method for connecting metal-coated optical fibers according to claim 1, characterized in that hydrochloric acid, nitric acid, or a mixed acid thereof is used for removing the metal coating. 2. The method for connecting metal-coated optical fibers according to claim 1, wherein the connecting method is performed by a physical pre-deposition method, a sputtering method, or a molten gold dipping method.