JPS60179707A - Method for coupling optical fiber with lens - Google Patents

Abstract

PURPOSE:To set the distance between a lens and optical fiber and to align their optical axes without making any adjustment works, by arranging >=3 balls which are respectively in contact with three points on the end face of a cylindrical ferrule fixing the optical fiber with its central part, inner surface of a precision sleeve having cylindrical holes for holding the ferrule in an arranged condition, and spherical surface section of the lens. CONSTITUTION:A lens 13 is fixed by screwing its lens holder 14 in a precision sleeve 12 after >=3 balls 15 which are respectively in contact with three points on the end face of a ferrule 11 fixing an optical fiber 10, the inner surface of the precision sleeve 12 holding the ferrule 11, and the surface of the spherical lens 13 are arranged. Therefore, the center of the lens 13 is aligned to the center line of the hole of the precision sleeve 12 and, accordingly, to the optical axis of the optical fiber 10 fixed to the center of the ferrule 11. Moreover, the distance between the lens 13 and end face of the optical fiber 10 is determined by the diameter of the balls 15. The distance (l) between the lens 13 and end face of the optical fiber 10 (end face of the ferrule 11) is determined from the focal length of the lens 13 and the diameter 2r of the balls can be calculated from the formula I .

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for optically coupling an optical fiber and a lens.

Prior art and problems The conventional method of coupling an optical fiber and a lens is shown in Fig. 1a.
As shown in the figure, the ferrule 2 to which the optical fiber l is fixed is
The ferrule is inserted into a precision sleeve 3 into which the lens 4 can be inserted, the lens 4 is fixed to the lens holding member 5 with adhesive, etc., the source 6 is passed through the optical fiber 1, and the light transmitted through the lens 4 is directed onto the screen 7. After adjusting the optical axis and the distance between the fiber and the lens by projecting the lens onto the lens, the method used is to fill the gap between the lens holding member 5 and the precision sleeve 3 with adhesive 8 and fix it as shown in Figure 1. . However, such a method requires time for adjustment, and has the disadvantage that the adhesive often creates a floating shape of the lens and affects temperature characteristics, etc.

Purpose of the Invention In view of the above-mentioned conventional drawbacks, the present invention aims to provide a method for coupling the original fiber and the lens, which allows the distance between the lens and the optical fiber and the optical axis to be matched without any adjustment, and which does not affect the temperature characteristics. This is the purpose.

Structure and object of the invention According to the present invention, there is provided a method for coupling an optical fiber 1 and a lens, in which the end face of a cylindrical ferrule having an optical fiber fixed at its center and a cylindrical cylinder holding the ferrule in alignment are provided. An optical fiber characterized in that three or more spheres are arranged in contact with the inner surface of a precision sleeve having a hole and the spherical part of the lens, respectively, and the optical fiber and the lens are optically coupled without adjustment. This is accomplished by providing a method for combining lenses.

Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a diagram for explaining a method of coupling an optical fiber and a lens according to the present invention. In the figure, 10 is an optical fiber, 11 is a ferrule to which the original fiber is fixed, 12 is a precision sleeve between the ferrule end faces, 13 is a ball lens,
Reference numeral 14 indicates a lens holder, and reference numeral 15 indicates a sphere.

This embodiment has a ball 15 (for example, a steel ball) that contacts three points: the end face of a ferrule 11 to which an optical fiber IO is fixed at the center, the inner surface of a precision sleeve 12 that holds the ferrule 11, and the surface of a ball lens 13. It is preferable that three or more be arranged at equal intervals or as close to it as possible. ) After that, the lens 13 is fixed by screwing the lens holder 14 to the precision sleeve 12. By doing this υ
The center of the ball lens 13 must be located on the center line of the hole in the precision sleeve, and coincides with the optical axis of the optical fiber 100 fixed at the center of the seven errules 11.

Further, the distance between the ball lens 13 and the end face of the optical fiber 0 (ie, the end face of the ferrule 11) is determined by the diameter of the ball 15.

FIG. 3 is a diagram for explaining the method of selecting the sphere 15.6. Q
, 10 is an optical fiber, 11 is a ferrule, 12 is a precision sleeve, 13 is a ball lens, D is the inner diameter of the precision sleeve, t
is the distance between the lens and ferrule end faces, R is the radius of the lens, and r is the radius of the sphere.

The distance t between the lens and the end face of the optical fiber (ferrule end face) is determined from the focal length of the lens 13, and the diameter 2r of the sphere 15 can be calculated using the following relational expression.

According to this embodiment, the lens can be positioned without adjustment, and its precision is as high as the dimensional accuracy of 7 errules 11 (concentric with the optical fiber). degree, parallelism, and outer diameter), inner diameter of precision sleeve, ball 15
Although it depends on the outer diameter of the optical fiber and the like, even taking these into consideration, it is possible to position the optical fiber and lens with an accuracy of several 11 meters.

FIG. 4 is a diagram for explaining another embodiment.
When a plano-convex lens is used as the lens, b is the case when a biconvex lens is used. In this figure, the same parts as in FIG. 2 are designated by the same reference numerals.

In this embodiment, since the plano-convex lens 16 is used in the case of figure a,
Since the optical axes cannot be aligned with the lens alone, the optical axes are aligned using the perpendicularity of the end surface 14a of the lens holder 14 inserted into the precision sleeve 12, and since b is the biconvex lens 17, The perpendicularity of the end surface 14a of the lens holder 14 and the sphere 18 are used to align the optical axes. The size of the sphere 15, which determines the distance between the lens and the end face of the optical fiber, can be determined using the same calculation formula as in the previous embodiment. Furthermore, the effects are also similar to those of the previous embodiment.

However, the accuracy of determining the optical axis of the lens is related to the outer diameter and squareness of the lens holder in addition to the conditions of the previous embodiment.

Effects of the Invention As explained in detail, the method of coupling an optical fiber and a lens of the present invention uses three or more balls that are in contact with the ferrule end face, the inner surface of the precision sleeve, and the spherical surface of the lens, thereby generating 70% of light without adjustment. The optical connection between the eye and the lens can reduce assembly man-hours, and since the lens can be fixed mechanically, environmental characteristics (mainly temperature characteristics) can be stabilized, which is a great effect.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining a conventional method of coupling an original fiber and a lens, Fig. 2 is a diagram for explaining a method of coupling an optical fiber and a lens according to the present invention, and Fig. 3 is a diagram used for the coupling method. FIG. 4 is a diagram for explaining a method of selecting a sphere, and FIG. 4 is a diagram for explaining another embodiment. In the drawing, IO is the original fiber, 11 is the ferrule,
12ha! ffl sleeve, 13 is a ball lens, 14 is a lens holder, 15. ．． 18 is a sphere, 16 is a plano-convex lens, 17
indicate biconvex lenses, respectively. Patent applicant Fujitsu Ltd. Patent application agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Yukio Uchida Patent attorney Akira Yamaguchi (a) (b)

Claims (1)

[Claims] 1. A method for coupling an optical fiber and a lens, which includes: the end face of a cylindrical ferrule with an optical fiber fixed at its center; the inner surface of a precision sleeve having a cylindrical hole that holds the ferrule in alignment; and the spherical part of the lens. A method for combining an optical 7-eyeper and a lens, characterized by arranging three or more spheres that are in contact with three points, respectively, and optically combining the optical fiber, the eyeglass, and the lens without adjustment.