JPS5944013A - Optical coupler - Google Patents

Abstract

PURPOSE:To prevent an increase in connection loss due to the sticking of dust and also to prevent a return of Fresnel reflection by fixing a ferrule which holds an optical fiber in a sleeve constituting a plug at a prescribed position and a prescribed angle. CONSTITUTION:A distributed index lens 1 is fitted in the fitting through hole 2b of the sleeve 2 so that its center axis is at a prescribed angle to the center axis of the sleeve 2, and the ferrule 4 is fixed in the sleeve 2 so that the end surface 3a of the optical fiber held by the ferrule 4 is at a prescribed position and a prescribed angle to the top end surface 1a of the lens 1. Parallel luminous flux 16 is projected by selecting the distance between the end surfaces 3a and 1a properly. Further, the inclination of the luminous flux 17 is set properly to make the position of the projected luminous flux 16 coincident with the position of the center axis S of the sleeve 2. When the angles of the optical fiber 3 and the normal 20 of the end surface 19 of the distributed index lens 1 to optical axes of pieces of transmitted luminous flux 21 and 22 are specified, no Fresnel reflection occurs on the normal 20.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical coupling device for coupling an optical component in which an incident light beam or an output light beam has a parallel beam end to a source fiber.

Conventionally, in this type of optical coupling device, a gradient index lens having a parallel light beam/blocking function is provided inside the optical component or a plug seat attached to the optical component, and An optical fiber is housed in a plug attached to the optical fiber, and the end faces of these gradient index lenses and the end faces of the optical fiber are arranged at right angles to the optical axis of the light beam passing through them.

Therefore, with this configuration, there is a problem that the core of the optical fiber inside the connector is exposed and dust adheres to the exposed core, increasing connection loss. R☆ High standard IW to fix the second set
It was difficult to maintain the accuracy, especially in a single mode 2 eyeball. Furthermore, since the end face of the optical fiber and the end face of the gradient index lens are arranged at right angles to the optical axis of the light flux passing through them, the Fresnel reflection from these ends m1 returns to the optical path of the optical coupler. There were drawbacks such as reduced performance.

゛, λObject of the invention 17i, 1. To provide a tying device that eliminates the drawbacks of the conventional one, (a) installing a refracting lens in the spigot, and (b) installing a lens in the spigot, By making the incident or emitted light beam an expanded parallel light beam, an increase in splice loss due to the adhesion of dust is prevented, and (b) the ferrule that holds the optical fiber is placed at a predetermined position and angle within the sleeve that constitutes the plug. By fixing them with optical adhesive, the mounting accuracy required for the parts that make up these connectors is greatly reduced, and the normals of the end faces of the fiber and the gradient index lens are By arranging it at a predetermined angle with the light flux passing through Il+, the Fresnel reflection from these end faces is prevented from returning to the original optical path. It has one characteristic.

The present invention will be explained below with reference to the drawings. Figure 1 shows 1.
4≦゛This is a sectional view of an actual example showing the structure of the optical coupling device according to the invention, in which a gradient index lens l made of a cylindrical lens body is fitted into the lower part 2a of the sleeve 2;
The optical fiber 3 is fitted and attached to the upper middle part of the sleeve 2 at a predetermined angle, and the optical fiber 3, which is viewed by the ferrule 4, has a predetermined angle with respect to the central axis of the eye fiber 3 that runs along its end surface 3a. It is polished like this. Furthermore, optical fiber 3
The optical fiber 3 is housed with the optical adhesive 5 so that the end face 3a of the lens 1 has a predetermined position and inclination with the upper end face 1a of the gradient index lens 1.
is fixed within the opening 2c.

Noel housing the gradient index lens 1 and the Optical Noiba 3
The sleeve 2 with the guide 4 is inserted into the guide 7.
When the threaded part of the outer shell part of the sleeve 2 and the threaded part of the inner peripheral part of the coupling nut 6 are engaged, the collar part 2e at the upper end of the opening of the sleeve 2 is clamped by the guide 7 and the coupling nut 6. Fixed.

Thus, the car (gradient index lens 1. Sleeve 2. Errule 4. Optical adhesive 5. Coupling now; h'11
In addition, the guide 7 forms a contact seat 111, and the guide 7 is fixed to the optical component 8.

FIG. 2 shows an oblique incidence 1 on the refractive index splitting lens 1 in FIG. 1.
This is to explain an example in which rays of light are converted into parallel light beams and emitted obliquely.

Here, the gradient index lens 1 is a transparent body whose refractive index in the radial direction decreases in proportion to the square from the center. If the refractive index is N, then N = No (1--r2)
”-(1) holds true. However, A is a positive constant.

Now, from the entrance side end surface 11 of the gradient index lens 1, +ll+
The distance d1 in the direction of 10 is the distance rIVζ from the axis 10, and the inclination from the axis 10 is r1'
Suppose that light @13 is emitted.

(jj L, ray 10) M axis 10 of gradient index lens 1
shall be on the same plane as At this time, the output end face 14
The light ray 15 emitted from the shaft 10 is also on the same instep surface as the axis 10,
The distance r2 from #il+10 and the direction r2' from the axis 10 are (2). However, if Z is the length of the gradient index lens 1 and the length Z of the cloth lens 1 is not selected, then the 2nd row and 2nd column element of the first term matrix on the right side of equation (2) will be zero. non-negative value
a=aO exists.

Therefore, to cos eight Z −do Noosing Z =
0 -- (3) is formed W[~, then equation (2) is i%1-(-No IA sin+/A Z) r 1
- (5) Tatsunaru.

From equation (5), the beam r2 of the light ray 15 emitted from the end surface 14 is
1 is the slope rl of the light ray 13 exiting the optical fiber 3
The collection of light rays 15 becomes a parallel light beam, and the inclination r2' of the optical axis of this parallel light beam is uniquely determined by the distance rIK of the end surface of the optical fiber 3 from the axis 1o. In this way, the distance kYt, r1 is determined. According to equation (4), the center 0'f position of the emitted light beam is determined by the distance r1' of the original glue 1 emitted from the optical fiber 3.

FIG. 3 shows a light beam 16 that enters the gradient index lens 1 by 11 inches.
The distance between the end surface 3a of the optical fiber 3 and the entrance side end surface 1a of the gradient index lens 1 is adjusted so that the optical axis of the sleeve 2 matches the center #1+S of the sleeve 2. If it is selected so as to satisfy the formula 3), the emitted light beam 16 becomes a parallel light beam.

Next, if the inclination between the central axis of the gradient index lens 1 and the central axis S of the sleeve 2 is r2°, then the position of the center of the end surface 3a of the optical fiber 3 that satisfies equation (5) [1] jr
By selecting l, the angle between the optical axis of the emitted light beam 16 and the central axis S of the sleeve 2 can be set to %t.

, 4, and if the distance between the center axis of the gradient index lens 1 on the exit end surface 1b of the gradient index lens 1 and the center axis S of the sleeve 112 is r2, then the optical fiber 3 is By selecting the inclination rlo of the light beam 17 to satisfy equation (4), the position of the emitted light beam 16 can be made to coincide with the position of the central axis S of the sleeve 2. Since the paths of the above-mentioned light beams 16 and 17 are reversible, the parallel light beams incident on the central axis S of the sleeve 2 at points 1 to 1 are condensed into the optical fiber 3. Therefore, optical fiber 3
The position and inclination of can be determined using the procedure described above.

Next, FIG. 4 shows the optical path of the reaction light beam when the normal 20 of the end surface 19 of the optical fiber 3 or the gradient index lens 1 is inclined with respect to the optical axis of the transmitted light beam 21, 22. It is a diagram. In general, the refractive index n1 of the medium constituting the optical fiber 3 or the gradient index lens 1, the refractive index n2 of the outer medium, iJ, -%l, I, and the Arenel normal to the lens. A reflection occurs.

Now, let's say fiber 3, also (1.11, gradient index lens 1
The light beam 21 incident on the inside toward the end surface 19 is the end surface 19.
shall make an angle θ with the normal 20 of
The light beam 22 emitted from is refracted and the normal line 20 and ψ(nls
The end face 19 forms an angle of
The light beam 23 reflected at the reflection angle θ forms a reflection angle θ. Therefore, the incident luminous flux 21 and the reflected luminous flux 23 form an angle of 2θ, and if the divergence angle of the incident luminous flux 21 is smaller than θ, the components of the reflected luminous flux 23 return to the incident luminous flux 210 optical path. Never. Similarly, the light beam 22 entering the optical fiber 3 or the gradient index lens l is
0 and ψ, the emitted light 21 is refracted to form an angle of y with respect to the normal line 20, and the reflected light beam 24 forms an angle of ψ with the normal line 20. Therefore, since the incident luminous flux 2'2'-' and the reflected luminous flux 24 form an angle of 2ψ, if the divergence angle of the incident luminous flux 22 is smaller than ψ, the components of the reflected luminous flux 24 It does not return to the optical path of the incident light beam 22.

As described above, since the plug and the plug seat in the optical coupling device according to the present invention can be coupled with an enlarged parallel light beam, it is possible to prevent an increase in loss due to adhesion of dust. or,
The necessary parallelism of the parallel light beams entering and exiting the plug can be easily achieved, and as a means for aligning the optical axis of the parallel light beams with the center axis of the sleeve, it is possible to easily achieve the necessary parallelism of the parallel light beams entering and exiting the plug. By adjusting and fixing the position and inclination within the sleeve, the precision required for mounting each component of the plug can be greatly reduced, thereby greatly reducing the manufacturing cost of the optical coupling device. It is possible. Furthermore, since the end face of the optical fin and the end face of the gradient index lens each have an inclination angle with respect to the transmitted optical axis, the optical meter returns to the original optical path by Fresnel reflection from these end faces. It has great features such as being able to significantly reduce the amount of water used.

',y轡'<1. , - are shown as an embodiment of the optical coupling device according to the present invention, but it is possible to make modifications and changes to the f1p without departing from the essence of the present invention. It should be obvious.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment showing the configuration of an optical coupling device according to the present invention, and FIG. 2 is an explanation showing an example in which a light ray incident obliquely on a gradient index lens is converted into a parallel light beam and exits obliquely. Figure 3 is an explanatory diagram showing how to adjust the optical axis of the light beam emitted from the refractive index distribution/Z1 to coincide with the central axis of the sleeve, and Figure 4 is an illustration of the optical fiber or the refractive index distribution. FIG. 6 is an explanatory diagram showing the optical path of a reflected light beam when the end surface of the lens is inclined with respect to the optical axis of transmitted light. 1... Gradient index lens 2... Sleeve 3...
Optical fiber 4... Ferrule 5... Optical adhesive 6... Coupling nut 7... Guide 8... Optical component patent applicant Japan Radio Co., Ltd.

Claims (1)

[Claims] (1) A sleeve, a gradient index lens provided at the bottom of the sleeve (θ; fitted and fixed in an oil hole), and an end surface of an optical fiber opposite to the end surface of the gradient index lens. They nod at each other in a prescribed manner, and are positioned at a distance.
A plug consisting of a ferrule containing the above-mentioned optical fiber and a coupling nand fixed in the opening of the sleeve with an optical adhesive is inserted into a plug seat made of a guide fixed to the optical component with the above-mentioned clamping nut. the light propagating through the optical fiber is converted into a parallel beam of light by the gradient index lens fixed to the sleeve of the connector, and is emitted to the optical component; An optical coupling device characterized in that a parallel light beam incident on the gradient index lens is condensed by the gradient index lens and outputted to the optical fiber. 2. The optical coupling device according to claim 1, characterized in that the optical coupling device has a length shorter by 1/4). (3) The optical axis of the light beam entering or exiting both end surfaces of the gradient index lens is the center ti of the gradient index lens.
1. The optical coupling device according to claim 1, wherein the optical coupling device is arranged so as to form a predetermined angle with lt. (4) The optical coupling device according to claim 1, wherein the central axis of the gradient index lens forms a predetermined angle with the central axis of the sleeve. (5) A parallel beam of light exiting from the gradient index lens to the optical component and a parallel beam of light entering the gradient index lens from the optical component are aligned with the central axis of the sleeve. An optical coupling device according to claim 1, characterized in that: (6) A patent claim characterized in that the end face of the above-mentioned optical fiber, which faces the end face of the gradient index lens, has a normal line thereof forming a predetermined angle with the central axis of the optical fiber. The 'L coupling device according to item 1.