JPH0442803Y2 - - Google Patents

Description

[Detailed description of the invention] [Summary] Technical field of the invention The present invention relates to a coupling structure between an optical fiber and a spherical lens, which eliminates the need to adjust the optical axis between the optical fiber and the spherical lens, and which is simple and inexpensive. The purpose of this invention is to provide an optical fiber coupling structure using a lens holder, and a ferrule that holds an optical fiber in the axial center is fitted and inserted into one of the ferrule insertion holes of the same inner diameter passing through the lens holder. The spherical surface of the spherical lens is brought into contact with the periphery of the end of the ferrule insertion hole on the other opening end surface of the insertion hole, so that the optical axis of the optical fiber and the center of the spherical lens are aligned, and the lens holder has a A lens accommodating recess whose inner surface does not come into contact with the periphery of the spherical lens is formed.

[Industrial application field]

The present invention relates to a coupling structure of an optical fiber and a spherical lens.

In recent years, optical fibers have been widely used in optical communication devices, optical measuring instruments, etc., and for this reason, optical components such as optical connectors for optically connecting optical fibers have been actively developed.

A lens is reversibly used to condense and convert the spread light emitted from the optical fiber into a parallel light beam that travels in the axial direction of the optical fiber. However, it is necessary to accurately align the optical axes of the optical fiber and the lens. Alignment adjustment to match these positions is difficult and requires complicated equipment, skill, and time.

[Conventional technology]

FIG. 2 is a positional relationship diagram for explaining the necessity of position adjustment for optical coupling between the optical fiber and the lens.

In FIG. 2, in order to convert the spread emitted light from the optical fiber 2 into a parallel light beam and to convert it into a light beam traveling in the axial direction of the optical fiber 2, a lens is placed on the optical axis at the tip of the end of the optical fiber 2. Place 1. At this time, the distance d from the lens 1 is adjusted and set so that the end face of the optical fiber 2 is located at the focal position of the lens 1. In addition, optical fiber 2 and lens 1
It is necessary to adjust and set so that there is no mutual axis deviation ΔX.

In order to perform the above positioning, a conventional example using a lens holder for setting and fixing the mutual positions of the optical fiber and the lens is shown in FIGS. 3 and 4.

Fig. 3 is a sectional view of the lens press-fitted into the lens holder, and Fig. 4 is a cross-sectional view of the lens being pressed into the lens holder, and Fig. 4 showing the lens being brought into contact with a ring-shaped spacer interposed between the lens holders.
FIG. 3 is a sectional view showing positioning.

In FIG. 3, a ball lens 1 is held and fixed to a lens holder 3 so as to face the end surface of an optical fiber 2. As shown in FIG. The tip of the optical fiber 2 is inserted into an optical fiber insertion hole precisely and precisely drilled in the center of a ferrule 21 made of a metal sleeve such as stainless steel or a sleeve made of ceramics, etc., and the tip end is aligned and glued. It is fixed with adhesive. On the other hand, the lens holder 3 has a cylindrical shape made of metal such as stainless steel, and has a ferrule insertion hole 31 in which the ferrule 21 can be tightly fitted with almost no gap on one side, and a ball lens 1 on the other side. A lens insertion hole 32, which is a recess that can be precisely press-fitted and held, is formed.

The ball lens 1 is press-inserted into the lens insertion hole 32 of the lens holder 3 from its open end, and is fixedly held in the state shown. Next, the ferrule 21 is inserted into the ferrule insertion hole 31 from its open end, positioned at the focal point in the axial direction, and fixed using an adhesive or the like. In this way, the lens holder 3 holds the lens 1 and the optical fiber 2 so that their optical axes coincide, and the distance from the lens 1 is set by moving the ferrule 21 forward and backward within the ferrule insertion hole 31.

In FIG. 4, the ball lens 1, the optical fiber 2, the ferrule 21, and the ferrule insertion hole 31 of the lens holder, which are indicated by the same reference numerals as in FIG. 3, are the same as in FIG. 3, and their explanation will be omitted. Here, the inner diameter of the lens insertion hole 32, which is a lens accommodation recess of the lens holder 3, is larger than the ball lens 1, and a gap is secured around the ball lens 1.

The ferrule 21 is then inserted until its end surface coincides with the boundary step between the ferrule insertion hole 31 and the lens insertion hole 32. A ring-shaped spacer 4 is inserted into the lens insertion hole 32, and the spherical surface of the spherical lens 1 is brought into contact with the peripheral edge of the end surface of the hole of the spacer 4, and fixed to the lens holder 3 with an adhesive or the like. The spacer 4 sets the distance between the end faces of the ball lens 1 and the optical fiber 2 to be a predetermined distance.

[Problem that the invention attempts to solve]

In the conventional structure shown in FIG. 3, it is necessary to align the mutual axes of the ferrule insertion hole 31 and the lens insertion hole 32, and the difference in diameter requires two-stage processing. A slight deviation inevitably occurred, and it was difficult to obtain a value in which ΔX in FIG. 2 was close to zero. In addition, in the case shown in FIG. 4, although the mutual spacing can be set, in order to align the axes, it is necessary to position the spacer 4 by slightly moving it along the end surface of the ferrule 21. Not only does this require an optical measuring device with an attached device and skilled operation, but it is also difficult to fix the spacer 4 after setting.

The present invention has been developed in view of the above-mentioned conventional problems, and it eliminates the need for optical axis adjustment between the spherical lens and the optical fiber, and combines the optical fiber and the spherical lens using a lens holder that is simple in construction and inexpensive. The purpose is to provide structure.

[Means for solving the problem] The gist of the present invention to achieve the above object is that an optical fiber is held centrally in one of the ferrule insertion holes of the same inner diameter passing through the lens holder. The ferrule is fitted and inserted, and the spherical surface of the spherical lens is brought into contact with the periphery of the end of the ferrule insertion hole on the other open end surface of the ferrule insertion hole, which is formed to form a plane perpendicular to the central axis of the ferrule insertion hole. The lens holder is characterized in that the optical axis of the optical fiber and the center of the spherical lens are made to coincide with each other, and that the lens holder is formed with a lens accommodating recess whose inner surface does not come into contact with the periphery of the spherical lens. It has a combined structure of optical fiber and spherical lens.

[Effect]

According to the above-mentioned coupling structure of the ball lens and the optical fiber, the optical fiber is accurately held at the axial center of the ferrule. On the other hand, the ferrule insertion holes with the same inner diameter that pass through the lens holder are machined in a straight line so that the ferrules fit tightly together.
Naturally, the axes of the opening end faces on both sides coincide.
Therefore, the center of the spherical lens that is seated in contact with the concentric circle of the opening end surface is automatically positioned on the extension of the axis of the ferrule insertion hole.
That is, the axes of the ball lens and the optical fiber coincide. The end face of the optical fiber can be positioned at the focal point by moving the ferrule back and forth into the ferrule insertion hole.

〔Example〕

FIG. 1 is a diagram for explaining one embodiment of the present invention, in which a is a cross-sectional view and b is a cross-sectional view when a spacer is used. In addition, parts given the same reference numerals throughout the drawings indicate the same target parts.

This invention basically consists of a ball lens 1 and an optical fiber 2.
and a lens holder 3. Then, as in the past, the optical fiber 2 is inserted into an optical fiber insertion hole that is precisely and precisely drilled in the center of the ferrule 21 whose tip is made of a metal sleeve such as stainless steel or a sleeve made of ceramics or the like. The end face is aligned with the end face and fixed with adhesive, and the end face is polished to an optical mirror surface.

The lens holder 3 has a cylindrical shape made of metal such as stainless steel, and has a perfect circular shape with a smaller diameter than the outer diameter of the spherical lens 1 so as not to block the optical path, and a ferrule 21 that fits in the gap. A ferrule insertion hole 31 that can be precisely fitted in an almost empty state;
On the other side, there is a lens insertion hole 3 which is a lens accommodation recess.
2 is formed. This lens insertion hole 32 is
The diameter is larger than the outer diameter of the ball lens 1, and it is set so that a slight gap is formed around the ball lens 1. Further, the opening end surface of the ferrule insertion hole 31 on the side of the lens insertion hole 32 is formed to form a plane that is accurately orthogonal to the central axis of the ferrule insertion hole 31.

With the above configuration, first, the spherical lens 1 is inserted into the lens insertion hole 32 of the lens holder 3, and its spherical portion is brought into concentric contact with the end periphery 33 of the opening end surface of the ferrule insertion hole 31. While seated in this manner, the ball lens 1 is pressed in the axial direction, and the gap between the lens insertion hole 32 and the ball lens 1 is bonded and fixed with solder, adhesive, or the like so that the lens insertion hole 32 and the ball lens 1 do not move.

Next, as shown in FIG. 1a, the optical fiber 2 is inserted into the ferrule insertion hole 31 of the lens holder 3.
Insert the ferrule from the open end of the ferrule,
It is positioned by moving forward and backward within the hole to a position where the end surface coincides with the focal position of the ball lens 1, and is fixed by appropriate fixing means (welding, adhesive, etc.). Note that the surface of the ball lens 1 and the end face of the optical fiber 2 are coated with a known optical non-reflection film in advance to prevent optical reflection loss from occurring.

FIG. 1b is the same as described above up to the point where the ball lens 1 is inserted and fixed into the lens holder 3. In FIG. b, the cylindrical pipe-shaped spacer 5 is then inserted into the open end of the ferrule insertion hole 31, and then the optical fiber 2 is inserted into the ferrule end surface through the open end of the ferrule insertion hole 31 of the lens holder 3. Insert it from the side, push it in so that the tip of the spacer 5 is in contact with the surface of the ball lens 1, and then tighten the ferrule 2.
1 to the lens holder 3 by the same means.

Since the length of the spacer 5 is set so that the end face of the optical fiber 2 coincides with the focal position of the spherical lens 1, it is possible to eliminate the work of adjusting the position of the ferrule 21 by moving it forward and backward within the hole. Further, the inner diameter of the hole in the spacer 5 is set to be large enough so as not to block the optical path.

In the above embodiment of the present invention, the lens holder 3 is made of stainless steel, but it is not limited to this and may be made of other metals with a relatively small coefficient of thermal expansion.

The coupling structure of the ball lens and optical fiber of this invention is
It can be applied to optical connectors that optically couple optical fibers, optical couplers between light emitting/receiving elements and optical fibers, optical multiplexers/demultiplexers using optical fibers, optical switches, and other optical devices. It goes without saying that the present invention can be applied reversibly to either the signal light output from the optical fiber or the signal light input to the optical fiber.

[Effect of idea]

As detailed above, according to the coupling structure of the ball lens and optical fiber of the present invention, by bringing the spherical surface of the ball lens into contact with the periphery of the opening end surface of the ferrule insertion hole, the spherical surface of the spherical lens is brought into contact with the periphery of the hole. Since it is possible to align on concentric circles and automatically align both axes with the optical fiber, the practical effect of aligning all optical axes with the axis of the optical fiber without any adjustment is remarkable. It is something. Furthermore, it is extremely effective in reducing costs due to ease of manufacture.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of one embodiment of the present invention, Fig. 2 is a positional relationship diagram showing the positional relationship for optical coupling between a ball lens and an optical fiber, and Fig. 3 is a conventional ball lens attached to a lens holder. A cross-sectional view of the press-fitted fixation,
FIG. 4 is a sectional view of a conventional lens in which a ball lens is fitted into a ring-shaped spacer and positioned on the end face of a ferrule. In the figure, 1 is a ball lens, 2 is an optical fiber,
3 is a ball lens, 5 is a spacer, 21 is a ferrule, 31 is a ferrule insertion hole, 32 is a lens insertion hole, and 33 is a peripheral portion, respectively.

Claims (1)

[Scope of utility model registration request] A ferrule 21 that holds the optical fiber 2 at its axial center is fitted into one of the ferrule insertion holes 31 having the same inner diameter and passes through the lens holder 3, and is inserted so as to form a plane perpendicular to the central axis of the ferrule insertion hole 31. The other open end surface of the ferrule insertion hole 31 formed has an end peripheral edge 3 of the ferrule insertion hole 31.
By bringing the spherical surface of the spherical lens 1 into contact with 3,
The optical axis of the optical fiber 2 and the center of the spherical lens 1 are made to coincide with each other, and the lens holder 3 is formed with a lens housing recess 32 whose inner surface does not come into contact with the periphery of the spherical lens 1. A combination structure of optical fiber and spherical lens.