JPH05213626A - Production of beam extending fiber - Google Patents

Abstract

PURPOSE:To efficiently obtain a beam extending fiber by which the size of a spot of light having a propagation mode is taperingly increased. CONSTITUTION:One end of an optical fiber 1 is heated by irradiation with laser light 3 which is absorbed in the glass of the fiber 1 and a dopant in the core 1-1 of the fiber 1 near the heated end is thermally diffused to produce a beam extending fiber. The heating may be carried out in combination with heating with heat rays.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a beam expanding fiber in which the spot size of a propagating mode is expanded.

[0002]

2. Description of the Related Art A beam expanding fiber having a tapered spot size is used to reduce diffraction loss of an isolator having a structure in which a polarizer and a Faraday rotator are sandwiched between optical fibers, or a tip having a small core diameter. It is used to efficiently excite low-order modes by bringing the part closer to the light emitting diode and connecting the end face with a large diameter to the transmission fiber. This type of beam expanding fiber was produced by a method in which an optical fiber was once produced and then the intermediate portion thereof was heated by a resistance furnace to diffuse the dopant added to the core (1990. Institute of Electronics, Information and Communication Engineers: OQ.
E89-135).

[0003]

In order to manufacture the beam expanding fiber by heating the optical fiber by the resistance furnace and thermally diffusing the dopant, at least 1000 optical fibers are required.
The temperature must be raised above ℃. Conventionally, since it was not possible to locally heat the fiber, there was a problem that the fiber was heated for a longer period than necessary and the strength was deteriorated.

[0004]

The present invention relates to a method of manufacturing a beam expanding fiber for solving the above-mentioned drawbacks, which is characterized in that a laser beam having a wavelength absorbed by the glass of the optical fiber is This is a method of irradiating and heating the local part of the optical fiber to thermally diffuse the dopant of the core of the local part.

Here, it is preferable to use the local part of the optical fiber together with the heating by the hot wire. Further, the most preferable method is to irradiate and heat the end face of the optical fiber through a transmission line having a high laser beam transmission property.

[0006]

As shown in FIG. 1, the quartz glass of the optical fiber 1 absorbs heat without passing through C glass in the 10.6 μm band.
Since the O ₂ laser beam 3 is squeezed by the lens 2 to irradiate the end face of the optical fiber 1, the O ₂ laser beam 3 can be locally and efficiently heated. Therefore, the dopant in the core near the end face of the optical fiber can be efficiently diffused. Further, as shown in FIG. 2, when arc discharge 5 is also used in the vicinity of the end face in the direction perpendicular to the optical axis of the optical fiber 1, the heating effect is enhanced and at the same time, the tapered portion 1-1-1 of the core diffusion depends on the position of the discharge heating.
You can also adjust the slope of the. Hereinafter, the present invention will be described more specifically with reference to examples. This is merely an example of the present invention and does not limit the technical scope of the present invention.

[0007]

【Example】

Example 1 FIG. 1 is an explanatory diagram of an example related to a method for manufacturing a beam expanding fiber of the present invention. In the figure,
Reference numeral 1 is an optical fiber, 2 is a lens, and 3 is laser light. The optical fiber 1 has a core 1-1 formed by doping Ge into quartz glass.
To form a 1.3 μm band single mode fiber, and the spot size radius is 5 μm. Laser light 3
Is a CO ₂ laser beam with a wavelength of 10.6 μm, and its output is 0.3 W. The lens 2 is made of ZnSe that transmits CO ₂ laser light well. Plastic coating 1-3
The CO ₂ laser light 4 was irradiated for 5 minutes to the end surface of the optical fiber 1 from which the end portion of 20 mm was removed for heating. as a result,
The spot size radius was 10 μm.

(Embodiment 2) FIG. 2 is an explanatory view of another embodiment relating to the manufacturing method of the present invention. In the figure, 4 is a transmission line for irradiation laser light, 5 is an electrode for arc discharge,
The same numbers as in FIG. 1 represent the same objects as in FIG. The irradiation laser light transmission line 5 is 10.6 μm band CO ₂ laser light, 5.6.
CO laser light in the μm band is well transmitted, but 0.6 μm
It is a silver halide fiber having a core 4-1 having a diameter of 20 μm, which does not pass He—Ne laser light in the band and semiconductor laser light in the 1.3 μm band. The end face of the optical fiber 1 was irradiated with 0.3 W of laser light in the 10.6 μm band and 12 mA of arc discharge current in the direction perpendicular to the axial direction of the optical fiber 1 by the irradiation laser light transmission line 5 and heated for 1 minute. As a result, the spot size radius of 5 μm became 14 μm. Furthermore, when a pair of discharge electrodes were added and the vicinity of the end face of the optical fiber 1 was irradiated and the above heating was performed, the tapered portion for core diffusion 1-1-
The slope of 1 could be changed.

[0009]

As described above, the manufacturing method according to the present invention (1) locally irradiates and heats a laser beam having a wavelength absorbed by the glass material of the optical fiber. It can diffuse heat. (2) Further, the heating effect can be enhanced by also using heating by a heat ray such as arc discharge, and at the same time, the inclination of the tapered portion of the core diffusion can be adjusted depending on the heating position. (3) Since the heating is performed locally, the length of removing the coating that protects the optical fiber and the length of deterioration of the optical fiber due to heating are shortened, so that post-treatment such as reinforcement after that is easy.

[Brief description of drawings]

FIG. 1 is an explanatory view of an embodiment relating to a method of manufacturing a beam expanding fiber of the present invention.

FIG. 2 is an explanatory view of another embodiment relating to the method for manufacturing the beam expanding fiber of the present invention.

[Explanation of symbols]

 1: Optical fiber 2: Lens 3: Laser light 4: Transmission line for irradiation laser light 5: Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Isamu Fujita 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works

Claims (3)

[Claims] 1. A method of manufacturing a beam expanding fiber, characterized in that a laser beam having a wavelength absorbed by glass of an optical fiber is applied to a local portion of the optical fiber to heat the optical fiber, and a dopant of a core of the local portion is thermally diffused. . 2. The method of manufacturing a beam expanding fiber according to claim 1, wherein a local portion of the optical fiber is used together with heating by a heating wire. 3. The method of manufacturing a beam expanding fiber according to claim 1, wherein the end face of the optical fiber is irradiated with the light through a transmission line having a high laser light transmission property and heated.