JPH09152513A - Non-reflection terminal part of coated optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to produce the terminal part of a coated optical fiber in a short time, to prevent the direct adhesion of dust, etc., on the end face in the exposed part of the optical fiber and to prevent the adverse influence by moisture by forming a carbon layer on the outer side of the front end part of the optical fiber in this terminal part. SOLUTION: The coating layer 2 in the terminal part of the coated optical fiber 3 constituted by forming the coating layer 2 on the outer side of the coated optical fiber 1 is removed by a prescribed length, by which the exposed part 4 of the optical fiber is formed in the non-reflection terminal part of the coated optical fiber 3. The end face of the exposed part 4 of the optical fiber is cut perpendicularly to the longitudinal direction. A carbon layer 9 is densely formed on the outer side of the exposed apart 4 of the optical fiber. Further, the exposed part 4 of the optical fiber and the carbon layer 8 formed on the outer side of the exposed part 4 of the optical fiber are housed into a ferrule 5 consisting of ziroconia, etc. An adhesive is applied on the inside of the ferrule 5, by which the ferrule 5 and the coated optical fiber 3 are adhered and fixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-reflecting end portion of an optical fiber core wire.

[0002]

2. Description of the Related Art When an optical transmission line is formed by laying an optical fiber core wire having a coating layer made of an ultraviolet curable resin or the like formed on the outside of an optical fiber between communication terminal devices,
Of the optical fiber cores of the optical transmission line, an unnecessary terminal unit that is not connected to the communication terminal device may occur.

The light transmitted to the end portion of the optical fiber core wire is reflected by the end face of the terminal portion and returns inside the optical fiber core wire, and for example, enters the light emitting source and is emitted from the light emitting source. It is known to have various adverse effects on the optical communication characteristics and devices of this optical transmission line, such as deterioration of light emission characteristics and incidence of noise on the light receiving side of the communication terminal device. There is.

For this reason, the so-called non-reflective terminal portion in which the light transmitted therethrough does not return to the terminal portion of the above-mentioned unnecessary optical fiber core wire (has good anti-reflection characteristics). You need to keep it.

FIG. 7 shows an example of a non-reflective terminal portion of an optical fiber core wire which has been conventionally used for optical parts such as an optical fiber coupler and an optical amplifier. As shown in FIG. 7, the conventional non-reflective end portion of the optical fiber core wire 3 has a tip end of the coating layer 2 at the end portion of the optical fiber core wire 3 formed by forming the coating layer 2 on the outside of the optical fiber 1. A side is removed by a predetermined length to form an optical fiber exposed portion 4, and the optical fiber exposed portion 4 is covered with a ferrule 5 made of, for example, zirconia or the like, and both are adhered with an adhesive or the like to expose the optical fiber together with the ferrule 5. The end surface of the portion 4 is obliquely polished.

In the non-reflective end portion of the optical fiber core wire 3, the light is reflected in the desired direction on the end face of the optical fiber exposed portion 4 in this way and is deflected to the outside of the optical fiber 1 to be expelled. I was trying not to go back inside.

FIG. 8 shows another example of the conventional non-reflective terminal portion of the optical fiber core wire 3. As shown in FIG. 8, the non-reflective end portion of the optical fiber core wire 3 forms the optical fiber exposed portion 4 and covers the ferrule 5 as in the case of FIG. 2, the optical fiber exposed portion 4 together with the ferrule 5 is cut or polished perpendicularly to the longitudinal direction, and the double-layer film filter 8 is vapor-deposited on the end face composed of the optical fiber exposed portion 4 and the ferrule 5. Here, this double-layered film filter 8 is formed of, for example, Al ₂ O ₃ and S.
This is a filter in which a low-refractive index layer 6 and a high-refractive index layer 7 such as iO ₂ are sequentially formed.

In the non-reflective terminal portion of the optical fiber core wire 3, light is transmitted from the end face of the optical fiber exposed portion 4 to the low refractive index layer 6,
The high refractive index layer 7 was sequentially ejected so that the light did not return in the optical fiber 1.

[0009]

However, in the non-reflective end portion of the optical fiber core wire 3 as shown in FIG. 7, the optical fiber exposed portion 4 made of a hard glass material is slanted together with the hard ferrule 5 made of zirconia or the like. Since it is necessary to polish with high precision, this polishing process takes a lot of time.
Further, if dust or the like adheres to the exposed end surface of the optical fiber exposed portion 4, the light moving in the optical fiber core wire 3 may be reflected by the dust or the like and may return inside the optical fiber core wire 3. It was

In the non-reflective end portion of the optical fiber core wire 3 as shown in FIG. 8, the process of forming the double-layer film filter 8 on the end face of the optical fiber 1 is complicated, and the double-layer film filter 8 is also required.
Since it is necessary to control the film thickness and the like of the film with high accuracy, it took a lot of time to form the double-layer film filter 8.

Further, in the non-reflective end portion of the optical fiber core wire 3 shown in FIGS. 7 and 8, the optical fiber exposed portion 4 or the double-layered film filter 8 is corroded or deteriorated due to moisture, and the non-reflective characteristic is exhibited. Long-term reliability was not obtained.

The present invention has been made to solve the above problems, and an object thereof is to easily manufacture in a short time and to prevent dust or the like from directly adhering to the end face of an exposed portion of an optical fiber. By preventing the adverse effects of water,
An object of the present invention is to provide a non-reflective terminal portion of an optical fiber core wire which can obtain long-term reliability of non-reflective characteristics.

[0013]

The non-reflective end portion of the optical fiber core wire according to the first aspect of the present invention is the end portion of the optical fiber core wire formed by forming a coating layer on the outside of the optical fiber. A carbon layer is formed outside the tip portion of the optical fiber.

The non-reflective end portion of the optical fiber core wire according to the second aspect of the present invention is the one according to the first aspect of the present invention,
The core layer at the tip of the optical fiber has a tapered shape.

The non-reflective end portion of the optical fiber core wire according to the third aspect of the present invention is the one according to the first or second aspect of the present invention, wherein the carbon layer has a thickness of 30 nm or more. And

As described above, in the non-reflective end portion of the optical fiber core wire according to the first aspect of the present invention, the carbon layer is formed outside the tip portion of the exposed portion of the optical fiber. The light that has traveled through is absorbed by this carbon layer. Further, since the carbon layer is formed on the end surface of the exposed portion of the optical fiber, dust and the like are prevented from directly adhering to the end surface of the optical fiber. Therefore, the light is prevented from returning in the optical fiber core wire.

Moreover, as can be seen from the results of the high temperature and high humidity test described later, since this carbon layer is inert to water and does not allow water to pass therethrough, water does not cause pain in the optical fiber. In the non-reflective terminal portion of the core wire, long-term reliability of anti-reflective characteristics can be obtained.

In order to form such a non-reflective end portion of the optical fiber core wire, a carbon layer is simply formed on the outer side of the front end portion of the optical fiber by, for example, vapor deposition. Therefore, the non-reflective end portion of the optical fiber core wire can be easily formed in a short time.

In the non-reflective end portion of the optical fiber core wire according to the second aspect of the present invention, since the core layer at the tip of the exposed portion of the optical fiber is tapered, the light that has moved to this portion is not formed. However, it cannot be completely accommodated in the core layer, leaks from the core layer into the clad layer, and is absorbed by the carbon layer formed outside the tip of the optical fiber. In this way, in the non-reflective end portion of the optical fiber core wire, the light that has moved to the non-reflective end portion of the optical fiber core wire can be more efficiently absorbed in the carbon layer.

However, in claim 2 of the present application, the tapered portion of the core layer may be narrower or wider than the portion on which the carbon layer is formed. From the viewpoint of improvement, it is preferable that the area is narrow as shown in FIG.

In the non-reflective end portion of the optical fiber according to the third aspect of the present invention, the carbon layer has a thickness of 30 nm.
Therefore, the carbon layer is formed with sufficient strength,
In addition, stable antireflection characteristics can be obtained.

However, it is preferable that the carbon layer in the present invention is densely formed so as to surely prevent the passage of water which causes the deterioration of the strength of the optical fiber.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a non-reflective terminal portion of an optical fiber core wire 3 as an example of an embodiment of the present invention. As shown in FIG. 1, in the non-reflective terminal portion of the optical fiber core wire 3, the coating layer 2 at the terminal portion of the optical fiber core wire 3 formed by forming the coating layer 2 on the outside of the optical fiber 1 has a predetermined length. The removed optical fiber exposed portion 4 is formed. Then, as shown in FIG. 2, the end face of the exposed optical fiber portion 4 is cut perpendicularly to the longitudinal direction by, for example, an optical fiber cutting device. However, in FIG. 2, reference numeral 10 indicates a core layer and reference numeral 11 indicates a cladding layer.

A film thickness of 40 nm is formed on the outside of the exposed portion 4 of the optical fiber by, for example, a thermal CVD method or a plasma CVD method.
The carbon layer 9 is densely formed. Further, the optical fiber exposed portion 4 and the carbon layer 9 formed outside the optical fiber exposed portion 4 are housed in a ferrule 5 made of zirconia or the like. However, an adhesive (not shown) is applied to the inside of the ferrule 5, so that the ferrule 5 and the optical fiber core wire 3 are adhered and fixed.

FIG. 3 shows an embodiment of a carbon layer forming apparatus for forming the carbon layer 9 on the outside of the exposed portion 4 of the optical fiber as described above. As shown in FIG. 3, the carbon layer forming apparatus includes a reaction container 12 capable of forming the carbon layer 9 in an airtight state, a gas supply pipe 13 for feeding the reaction gas into the reaction container 12, and exhausting the reaction gas. An exhaust pipe 14 and a light emitting unit 15 such as a carbon dioxide gas laser,
Condensing lens 1 that collects the irradiation light 16 emitted from the light emitting unit 15.
7, and a through hole 18 for inserting the optical fiber core wire 3 into the reaction container 12 for forming the carbon layer 9 therein.
Is provided.

In order to form the carbon layer 9 on the outer side of the exposed portion 4 of the optical fiber with such a carbon layer forming apparatus,
First, the optical fiber core wire 3 having the optical fiber exposed portion 4 formed at the tip is inserted into the reaction container 12 through the through hole 18, and in that state, a mixed gas of (acetylene gas + helium gas) is supplied from the gas supply pipe 13 to the reaction container. The mixed gas is fed into the reaction container 12 to fill the reaction container 12 with the mixed gas. However, at any time, the mixed gas or the product gas after the reaction is supplied from the exhaust pipe 14 to the reaction vessel 1.
Remove from within 2.

In this state, while moving the optical fiber core wire 3 in the longitudinal direction and rotating the optical fiber core wire 3 around the axis of the optical fiber core wire 3, the irradiation light 16 is emitted from the light emitting portion 15 through the condenser lens 17. The surface of the exposed portion 4 of the optical fiber is irradiated, and the acetylene gas is heated and reacted thereby, and the carbon layer 9
Are formed on the surface of the exposed portion 4 of the optical fiber.

The carbon layer 9 thus formed had a dense and uniform thickness and was stably coated on the outer surface of the exposed portion 4 of the optical fiber. Further, in the non-reflective end portion of the optical fiber core wire 3 thus formed, when light was sent to the end portion side of the optical fiber core wire 3, the light was absorbed by the carbon layer 9 and the inside of the optical fiber 1 I didn't go back.

Next, the long-term reliability of the non-reflective end portion of the optical fiber core wire 3 shown in FIG.
A test in which a sample is left under conditions of 1000C for 85 hours at 85 ° C. Here, 10 samples were used for evaluation. As a result, in the inspection after the test, no problem occurred in the appearance of one of the samples, the return loss did not change before and after the test, and the reflection-free end portion of the optical fiber core wire 3 of the present invention was Long-term reliability was confirmed.

On the other hand, as a comparative example, the same high temperature and high humidity test was conducted on the non-reflective end portion of the conventional optical fiber core wire 3 shown in FIGS. As a result, in appearance inspection, pain such as erosion and cracking occurs due to water on the end surface of the exposed optical fiber portion 4 of the non-reflective end portion of the optical fiber core wire 3 in FIG. 7, and the optical fiber core wire 3 in FIG. The two-layer filter 8 in the reflection terminal portion was also damaged by the deterioration due to moisture, and the wavelength characteristics were changed. Therefore, in the non-reflective end portion of the optical fiber core wire 3 of FIGS. 7 and 8, the return loss after the test is lower than that before the test, and stable long-term reliability of the non-reflective property is obtained. I couldn't do it.

As described above, the optical fiber core wire 3 of the present invention
It was confirmed that the non-reflective terminal part of No. 2 has longer-term reliability of non-reflective characteristics than the conventional one.

Here, in the example of the present embodiment, as shown in FIG.
Although formed perpendicularly to the longitudinal direction, in the non-reflective terminal portion of the optical fiber core wire 3 of the present invention, the shape of the tip of the optical fiber exposed portion 4 is not limited to this, and, for example, as shown in FIG. The tip of the exposed portion 4 of the optical fiber, especially the core layer 10 may be processed into a tapered shape to increase the light absorption efficiency of the carbon layer 9 (see a portion in FIG. 4).

To process the tip of the exposed optical fiber portion 4 into such a shape, for example, first, as shown in FIG. 5, the tip of the exposed optical fiber portion 4 (portion b in FIG. 5) is The optical fiber 1 is pulled by a burner 19 or the like while being heated to a temperature near the softening temperature, and then cut into pieces. The tip of the new optical fiber exposed portion 4 thus formed is stretched by being pulled and has a tapered taper shape, and the core layer 10 as well as the cladding layer 11 also has a taper shape.

After that, however, in order to smooth the shape of the tip of the uneven optical fiber exposed portion 4 as shown in FIG. 4, this portion is again softened by a burner 19 as shown in FIG. Heat to the vicinity and expose the optical fiber 4
It is better to soften the tip of and to make its shape smooth by surface tension.

In the example of the present embodiment, the carbon layer 9 is formed to have a film thickness of 40 nm, but in the non-reflective terminal portion of the optical fiber core wire 3 of the present invention, the film thickness of the carbon layer 9 is not limited to this. , May be thinner. However, it is preferable to form the carbon layer 9 with a film thickness of 30 nm or more in order to obtain stable non-reflection characteristics.

The carbon layer 9 is formed on the entire surface of the exposed portion 4 of the optical fiber.
Is sufficient to be formed so as to include at least the end surface of the exposed portion 4 of the optical fiber.

In the example of the present embodiment, the coating layer 2 is removed by a predetermined length at one end of the optical fiber core wire 3 to form the optical fiber exposed portion 4, and then the carbon is provided outside the optical fiber exposed portion 4. Although the layer 9 is formed, it goes without saying that the coating layer 2 may be applied to the optical fiber 1 on which the carbon layer 9 is previously formed.

In the non-reflective terminal portion of the optical fiber core wire 3 in the example of the present embodiment, the ferrule 5 is formed on this portion with the carbon layer 9 formed outside the exposed portion 4 of the optical fiber.
Although the carbon layer 9 is attached to reinforce the carbon layer 9 and the like, instead of the ferrule 5, for example, a resin coating layer may be provided on the outside of the carbon layer 9, or the carbon layer 9 may be formed densely and thickly to reinforce. . However, the non-reflective terminal portion of the optical fiber core wire 3 of the present invention does not necessarily require such reinforcement.

Although the optical fiber core wire 3 in the example of the present embodiment is a single core and has a single coating, the mode of the optical fiber core wire 3 in the present invention is not limited to this, and the optical fiber core wire 3 is not limited to this. Any core wire 3 can be used.

[0040]

The non-reflective end portion of the optical fiber core wire of the present invention can be easily manufactured in a short time, and in the non-reflective end portion of the optical fiber core wire, the end face of the exposed portion of the optical fiber is By preventing dust and the like from directly adhering, stable antireflection characteristics can be obtained, and further deterioration of the optical fiber due to moisture can be prevented, so that long-term reliability of the antireflection characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a non-reflective terminal portion of an optical fiber core wire according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a tip portion of an exposed portion of an optical fiber in a non-reflective end portion of the optical fiber core wire of FIG.

FIG. 3 is an explanatory view showing, in a partially cross-sectional state, one embodiment of a carbon layer forming apparatus that applies a carbon layer to the outside of an exposed portion of an optical fiber in the process of manufacturing the non-reflective end portion of the optical fiber core wire of FIG.

FIG. 4 is a cross-sectional view showing an embodiment other than FIG. 2 of the tip portion of the exposed portion of the optical fiber in the non-reflective end portion of the optical fiber core wire which is an example of the embodiment of the present invention.

5 is a cross-sectional view showing a first process in one embodiment for manufacturing the tip portion of the exposed portion of the optical fiber in FIG.

FIG. 6 is a cross-sectional view showing a second process in one embodiment for manufacturing the distal end portion of the exposed optical fiber portion of FIG.

FIG. 7 is a cross-sectional view showing an example of a conventional non-reflective terminal portion of an optical fiber core wire.

FIG. 8 is a cross-sectional view showing another example of a conventional non-reflective terminal portion of an optical fiber core wire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 optical fiber 2 coating layer 3 optical fiber core wire 4 optical fiber exposed portion 5 ferrule 6 low refractive index layer 7 high refractive index layer 8 bilayer film filter 9 carbon layer 10 core layer 11 clad layer 12 reaction vessel 13 gas supply pipe 14 Exhaust pipe 15 Light emitting part 16 Irradiation light 17 Condensing lens 18 Through hole 19 Burner

Claims (3)

[Claims] 1. An optical fiber core, wherein a carbon layer is formed outside an end portion of the optical fiber in a terminal portion of an optical fiber core wire formed by forming a coating layer on the outside of the optical fiber. Non-reflective end of line. 2. The non-reflective end portion of the optical fiber core wire according to claim 1, wherein the core layer at the tip of the optical fiber is tapered. 3. The non-reflective terminal portion of the optical fiber core wire according to claim 1, wherein the carbon layer has a film thickness of 30 nm or more.