KR20040000926A - Optical fiber - Google Patents

Abstract

PURPOSE: An optic fiber is provided to be capable of increasing the focal length of light by forming a semi-circular type concave part at the end portion of the optic fiber and filling predetermined material having a higher refraction index than that of the optic fiber into the semi-circular type concave part. CONSTITUTION: An optic fiber is provided with a core part(11) and a clad part(12). The optic fiber further includes a concave part(15) formed at one end portion of the core part and the clad part. And, predetermined material having a higher refraction index than that of the core part is filled into the concave part. In the device, the concave part is formed into a semi-circular type structure, a wet etching process is carried out for forming the concave part.

Description

Optical fiber

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber, and more particularly, to an optical fiber in which a hemispherical recess is formed at an end portion, and a focusing distance of the emitted light is increased by embedding a substance having a high refractive index in the recess.

In general, an optical fiber used to manufacture an optical module has a core (Core) 1 through which light is transmitted to the center of the cladding (Cladding) 2, as shown in FIGS. 1A and 1B, and is formed outside the clad 2. The ferrule 4 for protecting the optical fiber is enclosed. An epoxy 3 for adhesion is interposed between the clad 2 and the ferrule 4.

Since the refractive index of the core 1 portion is higher than that of the clad 2 portion, the optical fiber made in this way proceeds in the direction of the central axis of the core 1 without the incident light exiting to the outside.

The optical fiber has no external interference or interference from electromagnetic waves, is difficult to tap, and is light in weight. In addition, since it is easy to bend and can accommodate many communication lines, it is recently used for communication, image transmission, detector, and the like.

However, since the optical fiber has a short focal length of the emitted light, the working distance is short when optical coupling with an optical device such as a light emitting diode, a light emitting diode, a laser diode, etc., and it is difficult to manufacture an optical module. Coupling efficiency is also low.

Therefore, in order to improve the optical coupling efficiency, a method of focusing a laser beam emitted from a laser diode chip using an optical element such as a ball lens or processing an end of an optical fiber in the form of a convex lens is proposed to efficiently focus light. It became.

2 shows an example in which a convex lens 5 having a small size is attached to one end of an optical fiber to reduce the focusing distance of the emitted light. A single mode light wave traveling in parallel along the optical fiber is focused by the convex lens 5. Focused on P). See paper "Ideal Microlenses for Laser to Fiber Coupling" published by C. A. Edwards et al. In "Journal of Lightwave Technology [Vol. 11, No. 2, February 1993]".

However, when the optical module is manufactured using the optical fiber with a lens attached, as the number of parts increases, it is difficult to align with the optical element and the manufacturing cost increases. In addition, the optical fiber processed in the form of a convex lens is manufactured by fusion-bonding a silica glass rod or a multimode optical fiber to a single mode optical fiber, and then polishing the end of the silica glass rod or processing using heat. This takes a lot, and the working distance with the optical element is also short, making the optical module difficult.

Accordingly, the present invention provides an optical fiber that can solve the above-mentioned disadvantages by forming a hemispherical recess at the end of the optical fiber and embedding a material having a higher refractive index than the optical fiber in the recess to increase the focusing distance of the emitted light. There is a purpose.

The present invention for achieving the above object is characterized in that in the optical fiber consisting of a core and a clad, a recess is formed at one end of the core and the clad, and a material having a higher refractive index than the core is embedded in the recess.

The recess is formed in a hemispherical shape, characterized in that formed by a wet etching or polishing method.

In addition, the high refractive index material is characterized in that the resin, silicon oxide film or nitride film.

1a and 1b are a cross-sectional view and a front view of a typical optical fiber used for manufacturing the optical module.

2 is a cross-sectional view of a conventional optical fiber using microlenses to focus light in a single mode;

3 and 4 are cross-sectional views of the optical fiber according to the present invention.

<Description of Symbols on Main Parts of Drawing>

1 and 11: cores 2 and 12: clad

3 and 13: epoxy 4 and 14: ferrule

5: lens 15: main part

16: high refractive index material

In general, a plano-convex lens having a spherical surface where light is incident may have less spherical aberration than a lens having a planar surface, thereby reducing alignment and increasing optical coupling efficiency. The present invention utilizes this optical principle. That is, by forming a concave portion at one end of the optical fiber by wet etching or polishing method, and attaching or depositing a material having a higher refractive index than the optical fiber on the concave portion, the focusing distance of the emitted light is increased and optical coupling with the optical element is achieved. It can be achieved easily and efficiently.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a cross-sectional view of an optical fiber according to an embodiment of the present invention.

The core 11 includes a core 11, a clad 12 surrounding the core 11, and a ferrule 14 interposed between the clad 12 and an epoxy 13 for adhesion. A hemispherical recess 15 is formed at the end of the optical fiber made as described above, and the recess 15 has a higher refractive index than the core 11, for example, an epoxy resin, a silicone resin, a silicon nitride film, and a silicon oxide film. And the like are embedded in the deposition or deposition method.

The recess 15 may be formed by a wet etching method or a polishing method. In case of using wet etching, potassium hydroxide (KOH) or BOE (Buffered Oxide Etching) solution is used as the optical fiber dissolving agent. When the end portion of the optical fiber made up of the core 11 and the clad 12 or the ferrule 14 is immersed in the optical fiber dissolving agent, the core 11 and the clad 12 are isotropically etched to form a hemispherical recess 15. . At this time, the ends of the core 11 and the cladding 12 should form a straight line in a vertical direction to form a concave surface having a constant diameter, and the curvature of the concave surface is adjusted according to the etching time.

The diameters of the core 11 and the cladding 12 are preferably produced at, for example, about 6 to 10 µm and 125 µm.

The optical fiber manufactured as described above has a refractive index different from that of a light exiting part, compared with a conventional optical fiber having a fine convex lens attached to the end thereof, and is made of a material 16 having a high refractive index embedded in a hemispherical recess 15. The focusing distance of light is longer than that of a conventional optical fiber. That is, a single mode light wave traveling in parallel along the optical fiber passes through a material 16 having a high refractive index embedded in the recessed portion 15, and is focused at a focal point Q at a longer distance than conventional.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and various modifications and equivalent other embodiments will be possible to those skilled in the art. Therefore, the true technical protection scope of the present invention should be defined by the technical spirit of the appended claims.

As described above, the present invention forms a hemispherical recess at the end of the optical fiber, and embeds a material having a higher refractive index than the optical fiber in the recess to increase the focusing distance of the emitted light. Therefore, the optical coupling with the optical device can be easily and efficiently achieved by keeping the distance to the optical device wide enough without using a separate lens, thereby saving the manufacturing cost and time of the optical module. In addition, the present invention can easily and accurately change the focusing distance of the light to various values by adjusting the etching time.

Claims (6)

In an optical fiber consisting of a core and a clad, A recess is formed at one end of the core and the clad, and the recess is filled with a material having a refractive index higher than that of the core. The optical fiber according to claim 1, wherein the recess is formed in a hemispherical shape. The optical fiber of claim 1, wherein the recess is formed by wet etching. The optical fiber of claim 3, wherein the wet etching is performed in a solution of any one of potassium hydroxide and BOE. The optical fiber according to claim 2, wherein the recess is formed by a polishing method. The optical fiber of claim 1, wherein the material having a high refractive index is any one of a resin, a silicon oxide film, and a nitride film.