JPH0534545A - Optical fiber coupler - Google Patents

Abstract

PURPOSE:To inexpensively constitute an optical fiber coupler, to reduce adjustment and to improve an optical characteristic. CONSTITUTION:An optical fiber 2 is arranged so that it is faced to a spherical lens 1 and the central position of the end surface thereof is placed at the focus position of the lens 1. Besides, a spacer 3 which is optically transparent and whose both end surfaces are respectively brought into contact with the lens 1 and the fiber 2 is arranged between the lens 1 and the fiber 2. Then, a concentric grid-like groove pattern 4 for canceling the deviation of a phase caused by spherical aberration is formed on the end surface of the lens 1 side of the spacer 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber coupler for coupling light propagating through an optical fiber and spatially propagating light.

[0002]

2. Description of the Related Art Optical fiber couplers are used, for example, in fiber sensors, spatial optical communications, optical connectors, and fiber photoelectric switches. FIG. 8 shows a conventional example of such an optical fiber coupler. In FIG. 8, 12 is an optical lens (for example, a convex lens), 2 is an optical fiber arranged to face the optical lens 12, and 13 is the optical lens 12 and the optical fiber. It is a holder part for fixing the fiber 2 and is set so that the center of the end face of the optical fiber 2 is located at the focal position of the optical lens 12.

In the above structure, the parallel light propagating in the space is converged by the optical lens 12 at one point on the center of the end face of the optical fiber 2 and propagated through the optical fiber 2. On the contrary, the light emitted from the end face of the optical fiber 2 becomes parallel light by passing through the optical lens 12. Therefore, in the optical fiber coupler, it is necessary to satisfy such optical characteristics,
Therefore, one with high optical coupling efficiency is required.

FIG. 9 shows a configuration in which the optical characteristics are poor, and since the light from the optical lens 12 is not converged on the end face of the optical fiber 2 at one point, the optical coupling efficiency is lowered and the optical characteristics are not good. . That is, in the optical fiber coupler,
It is important to reduce the spherical aberration of the optical lens 12, and as such a lens, a compound lens shown in FIG. 10A, an aspherical plastic lens shown in FIG. 10B, and a lens shown in FIG. There are aspherical glass lenses and the like shown.

Further, in order to increase the optical coupling efficiency, it is usually necessary to adjust the positioning of the optical lens 12 and the optical fiber 2, and especially in the case of a single mode fiber, the adjustment at the micron level is necessary. For the adjustment, as shown in FIG. 11, the adjustment parameters are the optical axis direction (a), the direction perpendicular to the optical axis (b), the lens tilt (c), and the like.

[0006]

In such a conventional optical fiber coupler, it is necessary to reduce the spherical aberration in FIG.
The assembled lens of (a) has a large number of parts and is expensive, and the aspherical plastic lens of (b) of the figure changes the shape and refractive index of the plastic due to temperature change and deteriorates the characteristics. The aspherical glass lens of 1) has a problem that the structural process is complicated and expensive.

Further, as described above, a large number of adjustment parameters are required for the positioning adjustment of the optical lens and the optical fiber, and there is a problem that the assembling and mounting of the optical coupler becomes highly accurate and complicated.

Therefore, an object of the present invention is to inexpensively construct,
An optical fiber coupler with few adjustments and good optical characteristics is provided.

[0009]

DISCLOSURE OF THE INVENTION The present invention, which has been made to solve the above-mentioned problems, is provided with a spherical lens, and the spherical lens is arranged so that the center of the end face is located at the focal position of the spherical lens. Optical fiber, an optically transparent spacer located between the spherical lens and the optical fiber so that both end surfaces contact the spherical lens and the end surface of the optical fiber, and concentric circles on the spherical lens side end surface of the spacer. And a grid-like groove pattern formed in a shape.

Further, it is characterized in that it further comprises a ferrule having an optical fiber previously mounted therein, and a split sleeve or a tubular member into which a spherical lens, a spacer and a ferrule are integrally mounted.

Further, the present invention is characterized in that the two optical fiber couplers are arranged so that the spherical lenses face each other.

[0012]

The parallel light incident on the spherical lens is converged through the spacer to the center position of the end face of the optical fiber at one point and propagates through the optical fiber. Light emitted from the optical fiber enters the spherical lens through the spacer, and parallel light is emitted from the spherical lens. At this time, a phase shift from the reference wavefront due to spherical aberration is canceled by the concentric grating groove pattern formed on the end surface of the spacer on the spherical lens side, so that high optical coupling efficiency can be maintained.

Further, a ferrule having a spherical lens, a spacer and a fiber is integrally mounted inside by a split sleeve or a tubular member.

Further, two optical fiber couplers are prepared, and the respective spherical lenses thereof are arranged so as to face each other, thereby forming an optical connector.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.
In FIG. 1, 1 is a spherical lens, 2 is an optical fiber facing the spherical lens 1, and an optical fiber 3 is arranged so that the center 5 of the end face is located at the focal position thereof. 3 is between the spherical lens 1 and the optical fiber 3. An optically transparent spacer positioned so that both end surfaces are in contact with the end surfaces of the spherical lens 1 and the optical fiber 2,
Reference numeral 4 is a lattice-shaped groove pattern formed concentrically on the end surface of the spacer 3 on the spherical lens 1 side. The center (core) of the optical fiber 2, the center of the groove pattern 4, and the center of the spherical lens 1 are arranged linearly, and the center 5 of the end face of the optical fiber 2 is located at the focal position of the spherical lens 1 as described above. The length of the spacer 3 is set so that

In the above structure, the parallel light is converted into the spherical lens 1.
The incident light is further focused on the center 5 of the end face of the optical fiber 2, that is, the focal position of the spherical lens 1 at one point through the spacer 3, and the light is propagated through the optical fiber 2.
On the contrary, the light emitted from the optical fiber 2 enters the spherical lens 1 through the spacer 3, and the parallel light is emitted from the spherical lens 1. At this time, the spherical lens 1 has a spherical aberration, and since the spherical aberration is generated by the spacer 3, the optical coupling efficiency between the optical fiber propagating light and the spatial propagating light is lowered.
Therefore, the above-mentioned aberrations are canceled by the concentric lattice-shaped groove pattern 4 formed on the end surface of the spacer 3 on the spherical lens 1 side. That is, as shown in FIG. 2A, the groove pattern 4
When the groove pattern 4 is not formed, a phase shift 8 is generated from the reference wavefront 9 due to spherical aberration, but when the groove pattern 4 is formed, the phase shift 8 is canceled as shown in FIG. . It should be noted that when a lattice-shaped groove pattern is used, there is a concern that aberrations will increase due to fluctuations in wavelength of light and changes in temperature. However, since the pattern period is sufficiently larger than the wavelength, the change is negligible. The groove pattern 4 is formed, for example, in a saw-tooth shape in cross section.

The spherical lens 1 is made of, for example, a glass polishing lens, and the spacer 3 is made of glass, plastic, or the like. As shown in FIGS. 3 (a) and 3 (b), the spacer 3 may have a hollow interior, leaving a surface in contact with the spherical lens 1. Further, the spacer 3 can be formed by using a 2P method or the like in which a molding die is used using an ultraviolet curable resin or the like.

FIG. 4 shows an embodiment according to claim 2 of the present invention. In FIG. 4, 6 is a ferrule in which an optical fiber 2 is mounted, 7 is a ball lens 1, a spacer 3 and a ferrule 6 inside. It is a split sleeve (or a cylindrical member) that is integrally mounted, and the split sleeve 7 allows the centers of the spherical lens 1, the spacer 3, and the ferrule 6 to be arranged on a straight line. Here, as described above, the spherical lens 1 can be processed to have a diameter of a micron level by polishing, and the spacer 3 can also be formed to the same level of processing accuracy by a molding die, for example. Further, the ferrule 6 can be assembled without adjustment because the diameter of the ferrule 6 and the optical fiber 2 can be centered with the same degree of accuracy. The spherical lens 1, the spacer 3, the ferrule 6, and the split sleeve 7 may be fixed by adhesion with, for example, an ultraviolet curable resin or an epoxy resin. When such adhesive fixation is performed, as shown in FIG. Predetermined location (Fig. 5
Then, the opening portion 10 may be formed in a portion where the spacer 3 is exposed). According to the configuration shown in the figure, the bonding work can be facilitated by loading an epoxy resin or the like through the opening 10. In FIG. 5, the inner diameter of the split sleeve 7 is not constant, but is formed in a step shape corresponding to the diameters of the spherical lens 1, the spacer 3 and the ferrule 6.

FIG. 6 shows an embodiment according to claim 3 of the present invention. Two optical fiber couplers shown in FIG. 4 are prepared, and the spherical lenses 1 of the respective couplers are opposed to each other to form an optical connector. Is configured. Further, in FIG. 7, a guide member 11 is provided around the two split sleeves 7 in order to align the optical axes of the two fiber couplers of FIG. Also F
A screw part such as a C connector may be provided to fix the two optical fiber couplers.

[0020]

As described above, according to the present invention, an optical fiber coupler can be constructed at low cost by using an inexpensive spherical lens. Further, since it is a spherical lens, it is not necessary to adjust the tilt, and since the space between the spherical lens and the optical fiber is physically set by the spacer, the adjustment is easy and good optical characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an optical fiber coupler according to the present invention.

FIG. 2A is a diagram showing characteristics of a conventional optical fiber coupler, and FIG. 2B is a diagram showing characteristics of an optical fiber coupler according to the present invention.

FIG. 3 is a diagram showing another configuration of the spacer in FIG.

FIG. 4 is a diagram showing another embodiment of the optical fiber coupler according to the present invention.

5 is a diagram showing another configuration of the split sleeve or the tubular member in FIG.

FIG. 6 is a diagram showing another embodiment of the optical fiber coupler according to the present invention.

FIG. 7 is a diagram showing another configuration example in FIG.

FIG. 8 is a diagram showing a conventional optical fiber coupler.

9 is a diagram showing the characteristics of FIG.

10 is a diagram showing a configuration example of a lens in FIG.

FIG. 11 is a diagram showing the positioning adjustment in FIG.

[Explanation of symbols]

1 ball lens 2 optical fiber 3 spacers 4 groove pattern 5 Center position of the end face 6 ferrules 7 Split sleeve or tubular member 8 Position shift 9 Reference wavefront 10 Openings 11 Guide member

Claims (3)

[Claims] 1. A ball lens, an optical fiber which is arranged so as to face the ball lens and whose center of an end face is located at a focal position of the ball lens, and which is located between the ball lens and the optical fiber, Optically transparent spacers arranged so that both end surfaces are in contact with the spherical lens and the end surface of the optical fiber, and a lattice-shaped groove pattern formed concentrically on the spherical lens side end surface of the spacer. An optical fiber coupler characterized in that. 2. A ferrule to which an optical fiber is attached in advance, and a split sleeve or a tubular member into which the spherical lens, the spacer and the ferrule are integrally attached inside. Optical fiber coupler. 3. The optical fiber coupler according to claim 1, wherein the two optical fiber couplers are arranged such that spherical lenses face each other.