JPH055808A - Manufacturing method of optical fiber with expanded core diameter - Google Patents

Abstract

(57) [Summary] [Structure] A diameter-expanded portion of the optical fiber 1 is heated by a discharge (discharge electrode 4) to be in a molten state. In this state, a force along the longitudinal direction of the optical fiber 1 and facing each other is applied to this diameter-expanded portion, and this portion is pushed in from both longitudinal directions (indicated by the arrows in the figure) to obtain the fiber diameter and the core diameter. To expand. [Effects] An optical fiber with an expanded core diameter can be manufactured easily and in a short processing time, and an optical fiber with an expanded mode field diameter can be obtained. By embedding and using the embedded element in this, diffraction loss can be reduced and an excellent optical component can be constructed. In addition to being excellent in bending loss characteristics, it is possible to reduce mechanical strength due to heat and prevent adverse effects due to unnecessary diffusion.
It can be easily applied to various optical fibers such as plastic optical fibers and polarization maintaining optical fibers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical fiber having an expanded core diameter, which is used as an optical fiber in which an optical fiber embedded element is embedded.

[0002]

2. Description of the Related Art In recent years, as various optical elements for constructing optical parts, optical fiber embedded elements such as optical fiber embedded polarizers, optical fiber embedded isolators, and optical fiber embedded filters ( Hereinafter, abbreviated as an embedded device) has been developed. Such an embedded element is used by embedding the embedded element in a range where light propagates in an optical fiber. However, in order to embed these embedded elements in the optical fiber, it is necessary to cut the optical fiber, or to provide a notch portion or the like so that a part of the optical fiber is cut off. By this,
The light propagating through the optical fiber is diffracted to cause optical loss. As a method of reducing such diffraction loss, the core of the optical fiber in the portion where the embedded element is embedded is made thin,
Alternatively, there is a method of expanding the mode field diameter by expanding the diameter.

7 to 9 show an example of an optical fiber in which the mode field diameter is enlarged by reducing the diameter or expanding the diameter of the core. In the figure, reference numeral 1 is an optical fiber, 5 is a core, and 6
Indicates a clad.

The optical fiber 1 shown in FIG. 7 is one in which the confinement of light is weakened and the mode field diameter is expanded by heating and stretching the optical fiber 1 to reduce the diameter of the core 5 (down taper light). Fiber). The optical fiber 1 shown in FIG.
The core diameter is expanded by diffusing the, and the mode field diameter is expanded (core diffusion optical fiber). Further, in the drawing process of the optical fiber 1 shown in FIG.
Is formed in a tapered shape, and the mode field diameter is expanded by increasing the fiber diameter and the core diameter (up-tapered optical fiber).

[0005]

The downtapered optical fiber described above is easy to process, and it is relatively easy to obtain a desired optical fiber. However, bending loss tends to occur at a reduced diameter portion, It was inferior in mechanical strength. On the other hand, the above core diffusion optical fiber is easy to process, relatively easy to obtain a desired optical fiber, and has a bending loss comparable to that of the optical fiber before processing. However, it is difficult to set temperature conditions for diffusion control,
Since a long heating process is required, there is a disadvantage that the mechanical strength is likely to decrease. Further, the work efficiency of the up-tapered optical fiber is poor, it is difficult to control the fiber diameter and the core diameter in the drawing process, the reproducibility is poor, and it is difficult to obtain a desired optical fiber with high accuracy.

The present invention has been made in view of the above circumstances, and relates to a method of manufacturing an optical fiber having an enlarged core diameter, and easily manufacturing a desired optical fiber having an enlarged core diameter which is excellent in mechanical strength and bending loss characteristics. It is an object of the present invention to provide a manufacturing method capable of

[0007]

According to the method of manufacturing an optical fiber with an enlarged core diameter of the present invention, a force is applied along the longitudinal direction of the optical fiber and facing each other while heating the diameter-expanded portion of the optical fiber. The addition to the diameter portion was used as a means for solving the above problems.

[0008]

The present invention will be described in detail below. 1 to 5 show an embodiment of the present invention. A method for manufacturing an optical fiber with expanded core diameter according to the present invention is described in, for example, FIG.
It can be implemented by suitably using a device as shown as an example. This device comprises a pair of discharge electrodes 4 and 4 facing each other.
And a covering portion holder 3 for holding the optical fiber 1 with its covering portion. First, the coating layer 2 on the expanded portion of the optical fiber 1 is removed to remove the optical fiber 1
Is in a state of being exposed. Next, the coating layer 2 portion of the optical fiber 1 is fixed to the coating portion holder 3, and the optical fiber 1
The optical fiber 1 is arranged such that the longitudinal direction thereof and the opposing discharge electrodes 4, 4 are perpendicular to each other, and the diameter-expanded portion is located between the opposing discharge electrodes 4, 4. In this state, electric discharge is performed to heat the optical fiber 1, and subsequently, the coating portion holder 3 is moved in the longitudinal direction of the optical fiber 1 to move the optical fiber 1 in the longitudinal direction with respect to the heated diameter-expanded portion. Force is applied from both directions (indicated by arrows in the figure). As a result, the diameter-expanded portion which is heated and melted is pushed in from both longitudinal directions, and the core 5 and the clad 6 constituting the optical fiber 1 are expanded as shown in FIG. Diameter and core diameter are expanded, and core expanded area 7
Becomes At this time, the diameter-expanded portion may be pushed in only from one direction. Further, if necessary, the discharge state is maintained for a predetermined time, and then the discharge is stopped.

In this way, it is possible to easily obtain a core-diameter-increasing optical fiber in which the fiber diameter and the core diameter are enlarged in the middle part of the optical fiber. As shown in FIG. 2, the core diameter-enlarging optical fiber obtained here also has a maximum core diameter at or near the site where the fiber diameter is maximum. Therefore, the embedded element can be embedded by cutting the optical fiber 1 or providing a notch in this portion at or near the portion where the fiber diameter is maximum.

Here, parameters such as heating time and temperature in the manufacturing method of the present invention can be easily controlled by electrically controlling discharge time and discharge power. Therefore, the manufacturing method of the present invention has excellent controllability and reproducibility, can be easily applied to various optical fibers, and can be subjected to diameter expansion processing with high accuracy, and is highly productive and versatile. The diameter of the expanded diameter portion can be easily obtained by appropriately setting conditions such as the pushing speed and the pressing time.

Further, the material of the optical fiber which is subjected to the diameter expansion processing by the method of the present invention is not limited to glass and is applicable to the optical fiber manufactured using plastic as well as glass. be able to. Further, the heating means can be performed by any method, not limited to electric discharge, but by using electric discharge, the controllability of heating is improved, and the diameter expansion processing can be performed in a short time.
It is possible to minimize adverse effects such as deterioration of the optical fiber due to heat and increase in loss due to unnecessary diffusion.

Another embodiment of the present invention will be described. FIG. 3 shows a second example of the apparatus preferably used for carrying out the present invention. In this example, the covering portion holder 3 of the above embodiment is used.
In addition to the above, an optical fiber holder 8 for holding the exposed portion of the optical fiber 1 is provided. With this device, the same effect as the first embodiment can be obtained.

Further, in the manufacturing method of the present invention, as shown in FIG. 4 as a third example, an optical fiber tape core in which a plurality of optical fibers 1, 1 ... It can also be applied to lines. In this example, the collective coating layer 9 on the diameter-expanded portion is removed to leave the plurality of optical fibers 1, 1 ... Exposed, and then the plurality of optical fibers 1, 1. The same heating and pushing as in the method shown in the first example is performed. It is preferable to arrange the optical fibers 1, 1 ... In such a manner that the surface on which the optical fibers 1, 1 ... Are positioned and the surface on which the opposing discharge electrodes 4, 4 are positioned are parallel to each other. That is, a plurality of optical fibers 1,
The optical fibers 1, 1 ... Are preferably arranged so that a discharge is generated above or below the optical fibers 1, ... At this time, it is preferable to use the optical fiber holder 8 in addition to the covering portion holder 3 for fixing the optical fibers 1, 1.

Alternatively, in the manufacturing method of the present invention, in addition to heating and pushing the middle part of one continuous optical fiber 1 to expand the diameter of this part, as shown as a fourth example in FIG. , The two optical fibers 1, 1 that have been cut in advance can be connected, and at the same time, the diameter expansion processing can be performed. In this example, two optical fibers 1 and 1 are fixed to the cover holder 3 and the optical fiber holder 8 with their end faces abutted, and the tips of the discharge electrodes 4 and 4 facing each other are the optical fibers 1 and 1. The optical fibers 1, 1 are arranged so as to be located in the vicinity of the abutting portion of 1. In this state, the end portions of the optical fibers 1 and 1 are heated and pushed in the same manner as in the first example to connect the optical fibers 1 and 1, and the fiber diameter and The core diameter can be increased. In this method, the two optical fibers 1 and 1 fixed to the covering portion holder 3 and the optical fiber holder 8 are precisely aligned, and then heated and pushed in, whereby the optical fiber is twisted, misaligned, etc. It becomes easy to prevent. With this, even in the optical fibers 1 and 1 having the polarization maintaining structure, the polarization of the polarization is prevented from being twisted by pushing, and the polarization maintaining structure is maintained even in the expanded diameter region. Expanding processing can be performed.

(Example) A PANDA fiber 1 having a polarization plane maintaining structure was used as an example of an optical fiber to expand the core diameter. The cross-sectional shape of this PANDA fiber 1 is shown in FIG. In the figure, reference numeral 5 is a core, 6 is a clad, and 10 is a stress applying portion. The fiber diameter, core diameter, and stress-applying portion diameter of this PANDA fiber 1 were as follows. Fiber diameter 123.6 μm Core diameter 7.8 μm Stress applying portion diameter 34.2 μm First, the PANDA fiber 1 was cut in advance, the coating layer 2 at each end was removed, and the PANDA fiber 1 was left in a stripped state. Next, the PANDA fiber 1 was fixed to the covering portion holder 3 and the optical fiber holder 8 as shown in FIG. 5, and the axes were aligned. In this state, discharge was performed to heat the end of the PANDA fiber 1. The discharge current at this time was set to 17.4 mA, and after the preheating for 0.2 seconds, the coating portion holder 3 and the optical fiber holder 8 were set to P
The ANDA fiber 1 was moved in the longitudinal direction and pushed. The average relative pushing speed at this time is 517μ.
m / second, and pressing time was 0.325 seconds. Furthermore, the discharge state was maintained, and the discharge was stopped 3.5 seconds after the discharge was started. The obtained PANDA fiber 1 was cut at a site having the largest fiber diameter, and the cross-section fiber diameter, core diameter, and stress-applying portion diameter were measured. Fiber diameter after processing 153.5 μm Core diameter after processing 10.5 μm Stress-applying portion diameter after processing 44.0 μm As described above, a PANDA fiber with an expanded core diameter was obtained. In addition, the PAN obtained in this way
The DA fiber was not twisted in its plane of polarization, and was excellent not only in splice loss characteristics but also in mechanical strength and bending loss characteristics.

[0016]

As described above, according to the method for manufacturing an optical fiber with an enlarged core diameter of the present invention, while heating the diameter-expanded portion of the optical fiber, a force is applied along the longitudinal direction of the optical fiber and facing each other. It is to be added to the expanded area. Also,
Discharge can be suitably used as the heating means for the region to be expanded in diameter. Therefore, it is possible to manufacture an optical fiber with an expanded core diameter in an easy and short processing step,
An optical fiber having an expanded mode field diameter can be obtained. By embedding and using the embedded element in this, diffraction loss can be reduced and an excellent optical component can be constructed.

Further, in the manufacturing method of the present invention, the discharge time and the discharge power are electrically controlled even for various optical fibers,
By controlling the heating time, the temperature, etc., it can be easily applied, and the diameter expansion processing can be performed with high precision, which is highly productive and versatile. Further, by appropriately setting conditions such as pushing speed and pushing time, the diameter of the expanded diameter portion can be easily controlled, and an optical fiber having the expanded diameter portion of a desired size can be manufactured.

Further, the material of the optical fiber subjected to the diameter expansion processing by the method of the present invention is not limited to glass and may be applied to the optical fiber manufactured using plastic as well as glass. be able to. Furthermore, while not only ordinary single-mode fiber, etc., but also optical fibers having a polarization-maintaining structure, twisting due to diameter expansion processing is prevented, and the polarization-maintaining structure is maintained even in the core expanded portion. Diameter expansion processing can be performed.

The expanded core diameter optical fiber obtained by the manufacturing method of the present invention is excellent in bending loss characteristics and can be processed by heating for a short time, so that mechanical strength due to heat can be reduced. In addition, it is possible to minimize adverse effects such as increase in loss due to unnecessary diffusion.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a core expanded portion.

FIG. 3 is an explanatory diagram showing a second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a third embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a fourth embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a PANDA fiber.

FIG. 7 is a sectional view showing a downtapered optical fiber.

FIG. 8 is a cross-sectional view showing a core diffusion optical fiber.

FIG. 9 is a cross-sectional view showing an uptapered optical fiber.

[Explanation of symbols]

1 ... Optical fiber, 4 ... Discharge electrode, 5 ... Core, 7 ... Core expanded area

Claims (1)

Claims: 1. While heating a diameter-expanded portion of an optical fiber,
A method of manufacturing an optical fiber with an enlarged core diameter, characterized in that a force along the longitudinal direction of the optical fiber and facing each other is applied to the diameter-expanded portion. 2. The method of manufacturing an optical fiber with an enlarged core diameter according to claim 1, wherein heating of the diameter-expanded portion of the optical fiber is performed by electric discharge.