JPH01296202A - Optical fiber for coupling and its production - Google Patents

Abstract

PURPOSE:To form the optical fiber so as to comply with the shape of the beam of a light source and to improve coupling efficiency by forming one end face thereof to a circular shape and the other end to an elliptical shape and gradually changing the intermediate part from the circular shape to the elliptical shape. CONSTITUTION:One end face of the sectional shape of a core 2 of the optical fiber is formed circular and the other end face elliptical and the intermediate part thereof is formed to the shape gradually changing from the circular shape to the elliptical shape. Production of such optical fiber is executed by intermittently pressing a pair of rollers 18 to both side faces of the fiber in a still softened state after heating of a fiber base material 10 by a heater 12 and taking up the fiber by a bobbin 16. The optical fiber periodically having the elliptical parts is, therefore, obtd. This fiber is properly out. Since the core end having such elliptical shape is disposed to face the elliptical radiation beam of an LED or LD, etc., the high coupling efficiency is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention is directed to a light source of about 10 c
The present invention relates to a coupling optical fiber having a length of approximately m and has improved coupling efficiency.

(Prior Art) An optical fiber having a core with a normal circular cross section is used as a big teal for light sources such as semiconductor LEDs and LDs.

(Problems to be Solved by the Invention) Since the light emitting surface shape of an LED or LD is rectangular, the resulting beam has an oblong cross section, and the coupling efficiency with the core having a circular cross section is low.

Further, this generally applies to coupling with a flat plate waveguide.

(Means for Solving the Problem) The cross-sectional shape of the core of the optical fiber is such that one end is circular, the opposite end is oval, and the intermediate portion gradually changes from circular to oval, The end portion of the elliptical core is arranged to face the light source side such as an LED or LD.

In order to obtain this fiber, immediately after drawing a core-clad base material with a circular cross section to form a fiber, a pair of rollers are intermittently brought into contact with the opposite sides of the fiber, so that the cross section of the fiber is intermittently shaped into an elliptical shape. It was designed so that

Note that by appropriately setting the fiber drawing speed and the contact interval of the rollers, it is possible to obtain a fiber in which an elliptical core appears periodically with a predetermined length.

(Function) Since the shape of the radiation beam from the light source such as an LED or LD and the cross-sectional shape of the fiber core are similar, high coupling efficiency can be obtained.

In addition, a fiber in which an elliptical core is periodically repeated in the length direction can be obtained with a simple structure in which a roller is intermittently brought into contact with the roller immediately after the fiber is drawn. can be obtained in large quantities.

(Example) FIG. 1 is an explanatory diagram of a coupling fiber of the present invention, and FIG. 2 is a schematic diagram of an apparatus used in the method of this invention.

In the figure, ■ indicates the entire coupling fiber; 2 is a core with one end having a circular cross section and the other end having an elliptical shape, and a core that gradually deforms from circular to elliptical in the middle; 3 is the same-shaped cladding that covers this core. This fiber is manufactured using the apparatus shown in FIG. Reference numeral 10 denotes a core-clad fiber base material having a circular cross section, which is heated and softened by a heater 12 at its lower end, drawn at a predetermined speed by a capstan 14 to form a fiber, and wound onto a bobbin 16. Numeral 18 is a row arm which is brought into contact at predetermined time intervals with the opposing side surface of the fiber, which is still in a softened state immediately after being heated and drawn, thereby deforming the cross section of the fiber into an elliptical shape at predetermined intervals. 20 is a pot containing a coating material to protect the fiber; 22
is a furnace for curing this coating material. Using this device, a long fiber with periodic elliptical interiors can be obtained, and by cutting it appropriately, a coupling fiber with one end circular, the other end oval, and the middle gradually changing from circular to oval is obtained. It can be done.

(Specific example) The diameter of the core equivalent part is 2mm+, the outer diameter is 28+am, Δ=
The lower end of the 0.35% GeO□ doped silica core and silica clad optical fiber preform lO was heated to 210°C in a heating furnace 12.
It was heated to 0°C and drawn at a linear speed of 10 m/min using a capstan 14 to form a fiber 100 with a diameter of 125 μm (core diameter IO μm), and the fiber 100 with a diameter of 301 installed at a position of 10 ci+ directly below the heating furnace 12 rotates freely. A pair of rollers 16 that can be used to rotate the fiber 10 periodically every minute.
0, and then passed through the bot 20 containing epoxy acrylate type V curing resin to 37.5μ■
After being coated thickly, it was cured using an ultraviolet lamp 22 and wound onto a bobbin 16. The obtained fiber 100 is as follows.

The length of the inner part of the tank where the ratio of the long axis to the short axis is 5:1 in cross section is 1
It appeared periodically every 000c■. The fiber 100 thus obtained was cut to a length of 800 cm.
The core at one end is a perfect circle with a diameter of 10 μm.

The coupling efficiency with the LD was measured using an elliptical fiber 100 whose other end had a long axis of 20 μm, a short axis of 4 μm, and a ratio of 5:1. The active layer of the LD used was 0.8 gmX
It is a 1.36m band DFβ laser with 30μra. The result was a coupling efficiency of 43%, compared to the conventional core diameter of lOμm.
This was excellent compared to 25% for the circular fiber.

(Effects of the Invention) As described above, the present invention is a fiber in which the core shape is different at both ends and one end is oval, so by making this oval side face the light source, it is possible to match the beam shape of the light source. Therefore, it is possible to improve the coupling efficiency. In addition, as a method for obtaining this fiber, we adopted a method in which a pair of rollers are intermittently brought into contact with both sides of the glass fiber, which is still in a softened state immediately after drawing, to deform the fiber into an elliptical shape. By appropriately cutting the fiber, it is possible to obtain a large amount of coupling fiber whose one end is circular, the other end is oval, and the intermediate portion gradually deforms from circular to oval.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the coupling fiber of the present invention, and FIG. 2 is a schematic explanatory diagram of the apparatus used in the method of the present invention.

Claims (2)

[Claims] (1) A coupling optical fiber characterized in that one end has a circular cross-section, the other end has an elliptical cross-section, and the intermediate portion gradually deforms from the circular cross-section toward an elliptical shape. (2) Immediately after drawing a core-clad optical fiber having a circular cross section, a pair of rollers are intermittently brought into contact with the opposing sides of the fiber to deform the cross-sectional shape of the fiber into an ellipse. Production method.