JPS61267708A - Terminal structure for optical fiber - Google Patents

Abstract

PURPOSE:To prevent optical fibers completely from optical interference due to reflection by satisfying the wavelength of light rays to be coupled, the diameter of a section of a ferule in the direction rectangular to the center axes of a pair of ferules and the inclination of the ferules from the surface rectangular to the center axes with prescribed relations. CONSTITUTION:A pair of ferules 3, 4 to which respective optical fibers 1, 2 are fitted along respective center axes are aligned and fixed on the inside of an aligning sleeve 5 and the leading ends of respective ferules 3, 4 are shaped like planes. Both the ferules 3, 4 are fixed so that respective leading surfaces are inclined from the plane 6 rectangular to the center axis of the ferules 3, 4 by angles theta1, theta2. When the diameter of a section rectangular to the center axis of the ferules 3, 4 is D and separated distances between the optical fiber 1 and the center axis and between optical fiber 2 and center axis are e1, e2 respectively, equations III, IV are formed if formulas I, II are satisfied, so that e1<lambda/4 and e2<lambda/4 are formed. In this case, e1+e2=3 (e is the separated distance between the optical fibers 1, 2) is formed, so that e<lambda/2 is formed and the interval between cores in the ferules is <lambda/2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber terminal structure, and more particularly to a ferrule tip structure in an optical connector used for optical fiber communication.

Conventionally, optical connector ferrules tend to reflect light at the tip of the ferrule, and a phenomenon often occurs in which the optical output emitted from a coherent light source is unstable near the optical connector.

In order to eliminate this phenomenon, in recent years, the methods shown in Figs.
The structure shown in FIG. 7 is adopted. In these figures, 1 and 2 are optical fibers to be coupled to each other, 3 and 4 are ferrules for holding the optical fibers 1 and 2 along the central axis, and 5 is an alignment sleeve. It is.

In FIG. 5, the tip of the ferrule is sloped, in FIG. 6, it is a convex spherical surface, and in FIG. 7, the tip of the optical fiber is led out and has a convex surface.

By making the tip of the ferrule convex as in the examples shown in FIGS. 6 and 7, interference of light due to reflection is prevented, but when a pair of optical fibers 1 and 2 are connected with a connector, There is a drawback that the core parts, which are made of glass, butt against each other, so the core parts are easily damaged.

By making the tip of the ferrule sloped as shown in Figure 5, reflected light is prevented from returning into the optical fiber and light interference is prevented. However, since the end face is sloped, the ferrules Butting them together has the drawback that axis misalignment is likely to occur, resulting in an increase in axis misalignment loss.

Furthermore, optical connectors generally require polishing to smooth the optical fiber end face, but since the end faces of the convex ferrules and beveled ferrules have special shapes, there is no established manufacturing method, and manufacturing is difficult. Cost increases.

An object of the present invention is to provide an optical fiber terminal structure that easily and reliably prevents light interference due to reflection and prevents optical fibers from damaging each other.

Composition of the Invention The optical fiber terminal structure according to the present invention is characterized in that the wavelength λ of light to be coupled, the cross-sectional diameter of a pair of ferrules to be connected in a direction perpendicular to the central axis thereof, and the cross-sectional radius perpendicular to the central axis of the ferrules. The inclination θ of the ferrule tip surface with respect to the surface of the ferrule is set to satisfy the relationship 0≦θ<tan” (λ/20).

Example Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, and parts equivalent to those in FIGS. 5 to 7 are designated by the same reference numerals. In the figure, a pair of ferrules 3 and 4 with optical fibers 1 and 2 attached along their central axes are fixed in alignment inside an alignment sleeve 5, and the tips of each ferrule are shaped into a planar shape. has been done. The tip surfaces of both ferrules are attached at angles θ1 and θ2, respectively, as shown in the figure, with respect to a plane 6 perpendicular to the central axis of the ferrule.

In this configuration, the diameter of the cross section perpendicular to the central axis of the tip of the ferrule is D, and the distance between the tips of the optical fibers 1 and 2 and the center plane 6 is e1. When e2, 0≦θ1 < j a n (λ/2D)0≦02
When the conditional expression < t a n (λ/2D) is satisfied, tanθ1 ”2e1/[), tanθ2=2e
Since it is 2/D, el is λ/4 and el is λ/4.

Here, since el + e2 = e (e indicates the distance between the optical fibers), e x λ/2, and the distance between the cores in the ferrule is less than λ/2. This λ/
If the spacing is less than 2, no light interference due to light reflection on the ferrule end face will occur, and stable connection will be possible.

Figures 2 to 4 are structural diagrams of embodiments of the present invention to which the structure of Figure 1 is applied. Figure 2 is an example in which the ferrule tip has a two-stage structure, and Figure 3 is an example in which the ferrule tip has a two-stage structure. This is an example in which the vicinity of the ferrule tip is conical. Both sleeve 5
Although the internal shape of the sleeve 5 is cylindrical, in FIG.
The internal shape of the ferrule is made up of two cones facing each other, and the ferrule is aligned on the conical surface.

Effects of the Invention According to the present invention, there is no interference of light due to reflection on the ferrule end face, making stable connection possible.Also, since the core does not protrude from the ferrule end face, damage to the core part is eliminated, and the ferrule end face is sloped. Because I'm getting used to it,
This has the effect of eliminating axis misalignment loss.・

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, FIGS. 2 to 4 are sectional views of each embodiment of an optical fiber terminal structure to which the structure of FIG. 1 is applied, and FIGS. 5 to 7 are conventional FIG. 3 is a diagram showing a cross section of an optical fiber terminal structure of FIG. Explanation of symbols of main parts

Claims (1)

[Claims] An optical fiber terminal structure in which an optical fiber is fixed along the central axis of a cylindrical ferrule, and a pair of ferrules are abutted against each other to connect the optical fibers, the wavelength λ of the light to be coupled, and the Between the cross-sectional diameter D of a pair of ferrules in the direction perpendicular to the central axis of the ferrules and the inclination θ of the ferrule tip surface with respect to the plane perpendicular to the central axis of the ferrules, 0≦θ<tan^-^1 (λ/ An optical fiber terminal structure characterized in that the structure is set to satisfy the relationship (2D).