JP2001154031A - Optical fiber end face treatment method - Google Patents

Abstract

(57) [Problem] To provide an end face processing method for an optical fiber that can terminate a desired end face shape such as a flat shape or a convex shape in the end face processing of an optical fiber. SOLUTION: In an end treatment method for an optical fiber in which an end surface 1b of an optical fiber 1 is pressed against a smooth heating surface 5 to terminate the surface, at least a region 5a of the heating surface 5 where the end surface 1b abuts is provided. Was adopted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating an end face of a plastic optical fiber used for optical transmission.

[0002]

2. Description of the Related Art An optical fiber made of plastic is obtained by coating a core material made of a fiber such as methacrylic resin with a fluorinated methacrylic resin having a lower refractive index than the core material. It is used for optical transmission applications such as. When applying this type of optical fiber to optical transmission, it is required to treat the end face as smoothly as possible. That is, if the end face has a rough finish, transmitted light causes irregular reflection at the end face to cause an optical loss, and thus a finish for minimizing the loss is required.

[0003] The main methods of such finishing methods include, for example, a polishing treatment method for polishing the end face, a free cut treatment method for cutting the end face, and a hot plate treatment method for pressing the end face against a smooth heated surface. There is. The polishing treatment method has an advantage that a treatment surface with high smoothness can be obtained, but also has a disadvantage that the treatment takes time.
Further, the free cut processing method has an advantage that the processing can be performed in a short time, but also has a disadvantage that the smoothness of the processing surface is low. On the other hand, the hot plate processing method has an excellent feature that an end face having higher smoothness can be obtained than the free cut processing method and that the processing can be performed in a shorter time than the polishing processing method.

With respect to the method for processing the end face of an optical fiber by this hot plate processing method, the end face of the multi-core type optical fiber 1 shown in FIG. 6A or the multilayer type optical fiber 1 shown in FIG. The case will be described below with reference to the drawings. For example, the optical fiber 1 of the type shown in FIG. 6B has a core 1a having a multilayer structure made of different materials.

First, as shown in FIG. 7, a smooth heating surface 2 provided on a hot plate heater is heated so as to have a uniform surface temperature distribution, and an optical fiber 1 is placed above the heating surface 2. After being held perpendicular to the heating surface 2, it is lowered and its end face 1 b is pressed against the heating surface 2, and the state shown in FIG. 8 is obtained. At the time of this pressing, the end face 1 b of the optical fiber 1 is
From the heat to form a smooth flat surface 3.

[0006]

The optical fiber 1 terminated flat as described above is pulled up from the heating surface 2 and immediately after that, the flat surface 3 as shown in FIG. 9 is maintained. While cooling and solidifying for a while, each core 1
Due to the difference in heat shrinkage of a (difference in material), etc.
Since there is a difference in the heat shrinkage of each core 1a, the flat surface 3 cannot be maintained, and the convex surface 4a shown in FIG. 10A or the concave surface shown in FIG. It may be deformed to an unexpected end surface shape such as the surface 4b.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is directed to a method of processing an end face of an optical fiber that can terminate a desired end face shape such as a flat shape or a convex shape in the end face processing of a plastic optical fiber. For the purpose of providing.

[0008]

Means for Solving the Problems An end face processing method and an end face processing method for an optical fiber according to the present invention employ the following means in order to solve the above problems. That is, in the method for treating an end face of an optical fiber according to claim 1, in the method for treating an end face of an optical fiber in which an end face of the optical fiber is pressed against a smooth heating surface, at least the area of the heating surface where the end face abuts. In addition, a surface temperature distribution is provided.

According to the method for treating an end face of an optical fiber according to the first aspect, first, at least a region of the heating surface where the end face of the optical fiber is in contact is heated so that a predetermined surface temperature distribution is formed. Then, when the optical fiber is pressed perpendicularly to this area, this end face is melted on the entire surface by the heat transfer from the heating surface and deformed so as to be in close contact with the smooth heating surface, so that it is once formed into a smooth shape. You. At this time,
At the tip of the optical fiber, a temperature distribution corresponding to the surface temperature distribution of the contact area is formed. Thereafter, the optical fiber is separated from the heating surface and is radiated and cooled, so that the distal end portion thermally contracts so as to generate a thermal contraction difference based on the temperature distribution. This difference in heat shrinkage is controlled by adjusting the surface temperature distribution in the area of the heated surface. That is, by adding the heat shrinkage difference based on this temperature distribution to the heat shrinkage difference due to the difference in the material of the optical fiber, the tip portion of the optical fiber can be terminated into a desired shape.

According to a second aspect of the present invention, in the method of treating an end face of an optical fiber according to the first aspect, the surface temperature distribution is obtained by bringing a heating source into point contact with a back surface of the heating surface. It is characterized by.

According to the method for treating an end face of an optical fiber according to the second aspect of the present invention, the heating source is point-contacted to the back surface of the heating surface to heat the heating surface, so that the heating source is in point contact with the heating surface. It is possible to form a mountain-shaped surface temperature distribution in which the temperature is the highest and the temperature gradually decreases as the distance from the point increases.

According to a third aspect of the present invention, in the method of treating an end face of an optical fiber according to the first aspect, the surface temperature distribution is such that different thermal conductivity is provided on the back side of the heating face. It is characterized in that it is obtained by contacting a heating source with a plurality of heat conductors interposed therebetween.

According to the method for treating an end face of an optical fiber according to the third aspect, the heating of the heating surface is performed by bringing a heating source having a plurality of heat conductors having different thermal conductivity into contact with the back surface. By doing so, the temperature of the portion where the heat conductor having a high thermal conductivity is in contact is relatively high, and the temperature of the portion where the heat conductor having a low thermal conductivity is in contact is relatively low.
By adjusting the arrangement of these heat conductors, a surface temperature distribution having an arbitrary shape can be formed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical fiber end face treatment method according to the present invention is to terminate an optical fiber by pressing the end face of the optical fiber against a smooth heating surface. Although described below, it goes without saying that the present invention is not construed as being limited thereto. In each of the embodiments, similarly to the description of the related art, the multi-layered optical fiber 1 having the multi-layered core 1a is used. An example in which the end face 1b is deformed to be flat will be described as an example.

[First Embodiment] A first embodiment will be described with reference to FIGS. As shown in FIG. 1, in the first embodiment, a heating source 7 is provided on the back surface 6 of the heating surface 5.
Is different from the related art in that the surface temperature distribution is provided in the area 5a of the heating surface 5 where the end face 1b of the optical fiber 1 abuts. This point will be mainly described.

First, the end face 1 of the optical fiber 1 of the heating face 5
By bringing the heating source 7 into point contact with the back surface 6 of the heating surface 5 corresponding to the center 5 of the end face 1b of the optical fiber 1, the area 5a where the contact b contacts with, as shown by the solid curve in FIG.
The temperature T is highest at the point where the heating source 7 is in point contact (r = 0), and the temperature T gradually increases as the distance from this point increases.
Is heated so as to form a chevron-shaped surface temperature distribution 8 that lowers the temperature. Then, as shown in FIG. 3, when the end face 1 b of the optical fiber 1 is pressed against the area 5 a, the end face 1 b is melted on the entire surface by the heat transfer from the heating surface 5 and adheres to the smooth heating surface 5. By deforming as
It is formed into a smooth flat surface 9. At this time, a temperature distribution 10 (broken line curve shown in FIG. 2) corresponding to the surface temperature distribution 8 of the contact area 5a is formed at the tip of the optical fiber 1.

Thereafter, as shown in FIG. 4, the optical fiber 1 is separated from the heating surface 5 to be radiated and cooled. Then, when the end face 1b is heated by the heating surface 2 having a uniform surface temperature distribution as in the related art, each of the cores 1a has a different heat shrinkage rate (difference in material) due to the difference in the heat shrinkage. A difference in heat shrinkage occurs, and an attempt is made to deform into an unexpected convex shaped surface (the lower hatched area 11b in FIG. 4 shows the difference in the amount of heat shrinkage in this case). In the first embodiment, the temperature distribution 10 is given to the tip portion, and the heat shrinkage difference between the cores 1a based on the temperature distribution 10 (the upper region 11c of the broken line 11a in FIG. In the same case, the difference in the amount of heat shrinkage caused by the temperature is schematically shown). As a result, the unevenness is offset, so that the difference in the heat shrinkage due to the difference in the heat shrinkage etc. Since the difference is canceled out, the flat surface 9 is maintained. In other words, in the first embodiment, the core 1a made of a material having a large heat shrinkage at the same temperature is heated at a lower temperature than the other cores to reduce the heat shrinkage,
Conversely, a core 1a made of a material having a small heat shrinkage at the same temperature
In order to increase the heat shrinkage by heating at a higher temperature than the other cores and adjust the temperature distribution so that the heat shrinkage of each core 1a becomes equal as a result, After cooling, the end face 1b can be kept flat.

The difference in thermal contraction between the cores 1a based on the temperature distribution 10 is controlled by adjusting the shape of the surface temperature distribution 8 in the area 5a of the heating surface 5 in advance. The test data obtained by changing the shape of the surface temperature distribution 8 can be acquired, and the optimum surface temperature distribution 8 for obtaining a desired end face shape can be determined based on the results.

According to the method for treating an end face of an optical fiber of the first embodiment, the surface 5 is provided with the surface temperature distribution 8 when the heating surface 5 is heated. Since the amount of heat shrinkage of each core 1a after cooling can be adjusted, the end face 1b of the optical fiber 1 can be terminated to a desired flat face 9.

Further, according to the method for treating an end face of an optical fiber of the first embodiment, the heating source 7 is point-contacted with the back surface 6 of the heating surface 5 to heat the heating surface 5. It is possible to easily form a chevron-shaped surface temperature distribution 8 in which the temperature T is the highest at the point where the source 7 is in point contact, and the temperature T gradually decreases as the distance from the point increases. . In the first embodiment, the heating source 7 is brought into point contact with a portion substantially corresponding to the center position of the end face 1b of the optical fiber 1, but in the present invention, in order to form an arbitrary surface temperature distribution, The position at which the heating source 7 is brought into point contact can be appropriately set, and a plurality of heating sources 7 may be used.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. As shown in FIG. 5, in the second embodiment, the surface temperature distribution 8
Is obtained by bringing a heating source 16 in which a plurality of thermal conductors 15 having different thermal conductivities are interposed into contact with the back surface 6 of the heating surface 5. .

According to the method for treating an end face of an optical fiber according to the second embodiment, the heating surface 5 is heated by the heating source 16 having a plurality of heat conductors 15 having different thermal conductivity on the back surface 6 thereof. As a result, the temperature is relatively high in the portion where the heat conductor 15 having a high thermal conductivity contacts, and the temperature is relatively low in the portion where the heat conductor 15 having a low thermal conductivity contacts. By adjusting the arrangement of 15
The surface temperature distribution 8 similar to that of FIG. 2 described in the first embodiment can be easily formed.

Thus, similarly to the first embodiment, the heating surface 5 is provided with the surface temperature distribution 8 so that the amount of heat shrinkage of each core 1a of the optical fiber 1 in contact therewith after cooling can be adjusted. Thus, the end face 1b of the optical fiber 1 can be terminated to a desired shape, for example, a flat face 9.

In the first embodiment and the second embodiment, the case where the end face 1b of the optical fiber 1 is terminated to the flat surface 9 having a flat shape has been described as an example. However, the present invention is not limited to this. The present invention may be applied to termination to another desired shape such as a convex shape or a concave shape. In particular, when the end is formed in a convex shape, the light condensing area becomes large and the end face 1b has a convex lens function, so that the light condensing ability can be improved.

In the first and second embodiments, the optical fiber 1 is a multilayer type. However, the present invention is not limited to this. A multi-core optical fiber or a single-core optical fiber (not shown) May be applied to terminate the end face into a desired shape. INDUSTRIAL APPLICABILITY The present invention can be particularly preferably used for an optical fiber such as a multilayer type or a multi-core type in which the central portion of the optical fiber is made of a plurality of materials having different heat shrinkage rates. In the first embodiment, the surface temperature distribution 8 is formed by bringing the heating source 7 into point contact. In the second embodiment, the heating is performed by interposing a plurality of heat conductors 15 having different thermal conductivity. Although the surface temperature distribution 8 is formed by the source 16, the method of forming the surface temperature distribution 8 is not limited thereto, and other methods may be employed.

[0026]

According to the method for treating an end face of an optical fiber according to the first aspect of the present invention, a surface temperature distribution is provided at least in a region where the optical fiber is in contact with the heating surface, so that the end portion of the optical fiber can be provided. Since a difference in heat shrinkage based on the surface temperature distribution of the region can be generated, by adjusting the surface temperature distribution of the region, the end surface of the optical fiber is formed into a desired end surface shape such as a flat shape or a convex shape. It is possible to end.

Further, according to the method for treating an end face of an optical fiber according to the second aspect, the heating source is point-contacted to the back surface of the heating surface to perform heating, so that the heating source is in point contact with the heating surface. Thus, it is possible to easily form a chevron-shaped surface temperature distribution in which the temperature is the highest and the temperature gradually decreases as the distance from the point increases.

According to the method for treating an end face of an optical fiber according to the third aspect of the present invention, the heating surface is heated by applying a heating source having a plurality of heat conductors having different thermal conductivity to the back surface. By doing so, the temperature is relatively high in the portion where the heat conductor having high thermal conductivity contacts, and the temperature is relatively low in the portion where the heat conductor having low heat conductivity contacts,
By adjusting the arrangement of these heat conductors, an arbitrary surface temperature distribution can be easily formed.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a step of a first embodiment of an optical fiber end face processing method of the present invention.

FIG. 2 is a graph showing a surface temperature distribution of a heating surface in the same step of the end face processing method and a temperature distribution of an end face of the optical fiber in a next step shown in FIG. 3;

FIG. 3 is a side sectional view showing a next step of the end face processing method.

FIG. 4 is a side sectional view showing a next step of the end face processing method.

FIG. 5 is a side sectional view showing Embodiment 2 of the method for treating an end face of an optical fiber of the present invention.

6A is a cross-sectional view illustrating a cross section of a multi-core optical fiber, and FIG. 6B is a cross-sectional view illustrating a cross section of a multilayer optical fiber.

FIG. 7 is a side sectional view showing a step of a conventional optical fiber end face processing method.

FIG. 8 is a side sectional view showing a next step of the end face processing method.

FIG. 9 is a side sectional view showing a next step of the end face processing method.

10A and 10B are diagrams showing the optical fiber obtained by the same end face processing method after cooling, in which FIG. 10A is a side cross-sectional view in the case where the optical fiber is thermally contracted in a convex shape, and FIG. It is a sectional side view at the time of heat contraction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical fiber 1b ... End surface 5 ... Heating surface 5a ... Region 6 ... Back surface 7, 16 ... Heating source 8 ... Surface temperature distribution 15 ... Thermal conductor

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayuki Sugiura 4-1-1 Ushikawa-dori, Toyohashi-shi, Aichi Prefecture F-term (reference) 2H036 JA04 JA05 KA03 2H038 CA23

Claims (3)

[Claims] 1. A method for treating an end face of an optical fiber in which an end face of an optical fiber is pressed against a smooth heating face to terminate the optical fiber, wherein at least a region of the heating face where the end face abuts,
An end face treatment method for an optical fiber, wherein a surface temperature distribution is provided. 2. The method for treating an end face of an optical fiber according to claim 1, wherein the surface temperature distribution is obtained by bringing a heating source into point contact with the back surface of the heating surface. 3. The method for treating an end face of an optical fiber according to claim 1, wherein the surface temperature distribution includes a heating source in which a plurality of heat conductors having different thermal conductivity are interposed on a back surface of the heating surface. An end face treatment method for an optical fiber, which is obtained by contacting the end face.