JPH063559A - Structure for fixing lens in lens assembly for optical communication - Google Patents

Abstract

PURPOSE:To prevent the crack of a lens caused by heat in lens assembly constituting virtual fiber assembly used for optical communication. CONSTITUTION:In the lens assembly constituted of a metallic cylinder 1 which has a flange 2 at a front end and whose front and back are opened, and a lens 5 made of glass, which is press-fitted in the cylinder 1; a cut slit 3 having specified width, having T-shaped planar form and having a leading edge opened at the trailing edge of the cylinder is provided at a rear area far from the flange 2, and further annular space 4 having a tapered surface on the front end face of the inner wall of the cylinder 1 is formed. In the case of assembling, the lens is press-fitted and housed in the cylinder, and a gap part between the lens 5 and the cylinder 1 is soldered to be fixed by utilizing the space 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a virtual fiber assembly used in optical communication.
The present invention relates to a structure for fixing a lens in a lens assembly constituting a sembly).

[0002]

2. Description of the Related Art As shown in FIG. 5, a virtual fiber assembly includes a ferrule 11 attached to the end of an optical fiber cable 10, a metal sleeve 12 for accommodating the ferrule 11, and an inside of the sleeve 12. The lens assembly 13 is fitted and fixed in the tip region.

As shown in FIG. 6, the lens assembly 13
Is composed of a cylinder 15 having a flange 14 at its tip and a lens 16 inserted in close contact with the inside of the hollow thereof. The cylinder 15 has a slit 17 of constant width over its entire length. Even if the outer diameter of the lens 16 is slightly different from the inner diameter of the cylinder 15, the cylinder 15 can be elastically deformed through the slit 17, so that the lens 15 can be easily mounted in the cylinder 15.

After inserting the lens 16 into the cylinder 15,
The solder 18 is poured into the slit 17 to form the lens 1
The relative position between 6 and the cylinder 15 is fixed. Incidentally, although the lens 16 is made of glass, its surface is plated with gold, so that it can be fixed by soldering. Next, this lens assembly 13 is fitted in the tip region of the sleeve 12, and after accurate centering with the optical fiber cable in the ferrule 11, the tip of the sleeve 12 is spot-welded at an appropriate place on the flange 14 by laser. Fix on the surface.

[0005]

During this spot welding, heat is transferred to the cylinder 15 and expands it. The expansion of the cylinder 15 is amplified due to the presence of the slit 17,
On the other hand, since the expansion coefficient of the lens 16 is small, a tensile force may act on the lens to cause a crack. Even if such cracks do not occur during assembly, there is always the possibility of cracking as the slits expand and contract due to the temperature cycling of daily equipment operation.

An object of the present invention is to solve the above problems in the prior art and to provide a lens fixing structure capable of preventing cracking of the lens in the lens assembly.

[0007]

SUMMARY OF THE INVENTION The purpose is to house a sleeve with a ferrule mounted at the tip of a fiber optic cable to form a virtual fiber assembly, having a flange at the front end and open front and back. In a lens assembly for optical communication comprising a metal cylinder and a glass lens press-fitted into the cylinder, a T-shaped planar shape is formed in a rear region of the side wall of the cylinder far from a flange. Is provided with a slit having a predetermined width opened at the rear end of the cylinder, and further, an annular soldering space having a tapered surface that widens outward is formed on the front end surface of the inner wall of the cylinder. The lens is press-fitted and housed in the cylinder by utilizing the elastic deformation of the slit, and the lens and the cylinder are fixed by soldering by using the soldering space. It is achieved by the fixed structure of the lens in the optical communication lens assembly.

[0008]

When the lens is press-fitted into the cylinder during the assembly of the lens assembly, the width of the T-shaped slit changes and the inner diameter of the cylinder widens, which facilitates the work. Since the lens and the cylinder are fixed by pouring the solder into the soldering space provided at the front end of the cylinder where there is no slit, the temperature change of the inner diameter of the cylinder in the portion can be suppressed to a small level. Further, even if expansion and contraction of the slit occur in the cylindrical portion where the slit exists, the lens is not soldered in this region, so that cracking of the lens is prevented.

Based on the preferred embodiment shown in the drawings,
The present invention will be described in more detail.

[0010]

1 is a perspective view showing the outer appearance of a cylinder 1 of a lens assembly according to a first embodiment of the present invention, and FIGS. 2a and 2b are a side sectional view and a front view thereof. As is clear from these figures, the cylinder 1 has a flange 2 at the front end thereof, and a rear portion of the cylinder 1 is provided with a slit 3 having a T-shaped planar shape on a part of the side wall. This slit 3 extends the middle leg of the T-shape parallel to its axial direction, the tip of the leg being open at the rear face of the cylinder 1. With this configuration, the slit 3 has a width d.
Can be variably elastically deformed.

The inner wall of the flange 2 existing on the front end surface of the cylinder 1 is processed so as to form a taper surface that spreads outwardly to form an annular space 4 (hereinafter referred to as a soldering space). In this example, the soldering space 4 further has an extension region 4a that has entered the inside of the cylinder. At the time of assembling the lens assembly, the lens 5 is press-fitted inside the cylinder as shown by the alternate long and short dash line in FIG. This is cut 3
This is the same as the conventional method using the modification of.

Next, molten solder is poured into a gap between the lens surface and the inner wall of the cylinder in the soldering space 4,
Fix both. Since the flange area of the soldered cylinder does not have the slits 3, even if high heat is applied when spot-welding the assembled lens assembly to the sleeve 12, the expansion and contraction of this area of the cylinder is slight. As a result, cracking of the lens due to the difference in thermal behavior between the lens and the cylinder as in the related art is prevented.

FIG. 4 shows a second embodiment of the present invention. In addition to the structure of the first embodiment, this is the soldering space 4
An annular solder accommodating groove 6 is provided concentrically with the outer flange region of the, and the solder 7 is poured in advance therein. The function of the solder receiving groove 6 is that when the assembled lens assembly is spot-welded to the sleeve 12 at an appropriate position 8 of the flange 2, high heat for welding is transmitted to the lens 5 through the cylinder 1 and is applied to this. The purpose is to prevent cracking. That is, by storing the solder 7 in the solder receiving groove 6 on the path from the welded portion 8 to the lens 5, the heat is consumed as melting heat for melting the solder 7 and does not reach the lens.

[0014]

As described above, according to the present invention, the slit is provided only in the rear region of the cylinder for housing the lens so that the slit does not exist in the soldering region, and the solder is fixed between the lens and the cylinder. Since the position is limited only to the front end, the defect that the lens is cracked due to a large difference in thermal behavior between the lens and the cylinder during spot welding is eliminated.

Furthermore, since a solder receiving groove is provided in the vicinity of the spot welding spot and the solder is poured in advance here, the high heat of the spot welding is consumed as the melting heat of the solder and prevented from reaching the lens, and cracks are prevented. Is prevented.

[Brief description of drawings]

FIG. 1 is a perspective view of a cylinder according to a first embodiment of the present invention.

FIG. 2 is a side sectional view (a) and a front view in the X direction (b).

FIG. 3 is a side sectional view similarly accommodating a lens.

FIG. 4 is a side sectional view of a cylinder according to a second embodiment of the present invention.

FIG. 5 shows a virtual fiber to which the present invention is applied.
It is a sectional side view which shows the structure of an assembly.

FIG. 6 is a perspective view of a conventional lens assembly.

[Explanation of symbols]

 1 ... Cylinder 2 ... Flange 3 ... Notch 4 ... Soldering space 5 ... Lens 6 ... Soldering groove 7 ... Solder 8 ... Spot welding location

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tetsuo Ishizaka 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Koeko Yokoi 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (2)

[Claims] 1. A front and rear open metal having a flange (2) at its front end, which is housed in a sleeve (12) together with a ferrule mounted at the end of an optical fiber cable to form a virtual fiber assembly. A lens assembly for optical communication comprising a cylindrical (1) made of glass and a glass lens (5) press-fitted into the cylindrical cylinder (1), wherein a T-shaped portion is provided in a rear region of the cylindrical side wall far from a flange (2). Is provided with a slit (3) having a predetermined width, the front end of which is open at the rear end of the cylinder (1), and further a taper that spreads outward on the front end surface of the inner wall of the cylinder (1). A ring-shaped soldering space (4) having a surface is formed, and at the time of assembly, the lens (5) is press-fitted and housed in the cylinder (1) by utilizing the elastic deformation of the slit (3), and the soldering space is formed. Take advantage of (4) Use lens (5) and cylinder (1)
A lens fixing structure in an optical communication lens assembly, characterized in that it is soldered between 2. The annular solder accommodating groove (6) according to claim 1, wherein an annular solder receiving groove (6) is provided in a region of the front end face of the flange (2) further outside the soldering space (4). Fixed structure.