JPS6242108A - Optical fiber terminal and its manufacture - Google Patents

Abstract

PURPOSE:To minimize connection loss by cutting the outer periphery of a lens holder part so that the optical axis of a light beam formed after output light from an end surface of an optical fiber is transmitted through a collimator lens is aligned with the axis of the lens holder, and making a connection on the basis of the outer periphery. CONSTITUTION:The optical fiber 2 is adhered and fixed to a fiber end grip part 3 and the collimator lens is adhered and fixed to the lens holder part 5. In this case, the axis of a light beam 9 projected from the collimator lens 4 slants slightly downward to the axis of the optical fiber 2. At this time, the outer peripheral surface of the lens holder part 5 is machined cylindrically so that its axis is aligned with the axis of the light beam. The completed lens holder part 5 has such a little bit slanting outward appearance that the outer peripheral part 5'' is removed. When an optical fiber terminal which is worked with high precision is coupled with an optical fiber terminal which is grounded owing to a shift in axis by a connection sleeve, light beams of the both are nearly equal to each other and their axes aligned with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical fiber terminal processed for connection between optical fibers and a method for manufacturing the same.

[Conventional technology]

As a type of optical connection method between optical fibers or between a light emitting element or a light receiving element and an optical fiber, there is a method using a collimating lens. An optical fiber terminal using this method is called a space propagation type optical fiber terminal.

An example is shown in FIGS. 5 and 6. Both figures are longitudinal sectional views of optical fiber terminals with different configurations.

In FIG. 5, a jacket 1 made of nylon or the like is
The optical fiber 2 that has been peeled off to a predetermined length is fixed in a metallic connector member. This connector member includes a fiber end gripping part 3 for fixing the end of the optical fiber, a collimating lens 4 disposed opposite to the end surface 2' of the optical fiber 2, and a lens holder 5 for supporting and fixing this lens. It is provided.

The optical fiber 1 is fixed in a small diameter through hole 6 provided in the fiber end gripping part 3 with an adhesive such as epoxy resin. Further, the jacket 1 is fixed to the large diameter gB7 using the same type of adhesive or the like.

On the other hand, the collimating lens 4 is fixed in advance in the lens holder 5 at a position such that the end face 2' of the optical fiber is at its focal point using an adhesive or the like. Further, the lens holder 5 is initially separate from the fiber end gripping section 3. After the optical fiber 2 is completely fixed in the fiber end gripping part 3, the lens holder 5 is moved in the direction of arrow 8 to completely align the optical axis of the optical fiber 2 and the optical axis of the collimating lens 4. let After that, adhesive 10 was applied between the lens holder 5 and the fiber end gripping part 3.
etc. to connect and fix the two.

This optical fiber terminal is manufactured in this way.

In addition, in the case of the one shown in FIG. 6, the fiber end gripping part 3
and lens holder 5 are integrally constructed. The optical fiber 2, jacket 1 and collimating lens 4 are fixed in a manner similar to that in FIG. However, optical fiber 2
The small diameter through hole 6 into which the optical fiber 2 is inserted is processed with high precision so that the optical axis of the optical fiber 2 can be aligned with a fixed axis. Further, the collimating lens 4 is fixed so as to be inscribed in a tapered surface 5' provided on the inner surface of the lens holder 5, so that the optical axis of the optical fiber 2 and the optical axis of this collimating lens 4 are precisely aligned. has been done.

Therefore, the outer surface of the lens 4 itself, the tapered surface 5' of the lens holder 5, etc. must be processed with high precision.

In this way, in each optical fiber terminal, the light emitted from the optical fiber is made into a parallel beam, and conversely, the parallel beam incident from the outside is focused and enters the end face of the optical fiber. .

[Problem that the invention seeks to solve]

Here, as shown in FIG. 7, when the focal length of the collimating lens 4 is f, if the optical axis of the collimating lens 4 and the optical axis of the optical fiber 2 are misaligned by ΔX, then
The output light beam 9 is directed to the desired light beam 9',
It will be tilted by an angle θ. This angle θ is calculated by the following formula.

For example, if a collimating lens with f=500 Cμm is used and the axis deviation ΔX is 1O [μm], the inclination of the light beam will be approximately 1.2°.

FIG. 8 shows a side view of a straight connection between two optical fibers 2.2'. In this example, two collimating lenses 4.4' are used and the light beam 9' propagates as shown by the solid line. Here, if one of the collimating lenses 4 is axially misaligned and the light beam 9 is tilted as shown by the broken line, the projected images of the beams from the left and right will no longer match on the surface 11. cause a loss.

For example, in the case of straight connection of graded type (CI type) optical fibers with a core diameter of 50 μm, the connection loss becomes 1 dB or more.

Therefore, alignment of the optical axes of the optical fiber 2 and the collimating lens 4 requires extremely high accuracy.

In the case of the example shown in FIG. 5, in addition to the highly accurate adjustment work of adjusting the fiber end gripping part 3 and the lens holder part 5 while moving them relative to each other, this alignment work also involves adjusting both of them after adjustment. This requires processing work that requires stability and precision, such as fixing it in place. Therefore, it has serious drawbacks, especially in terms of productivity and price.

On the other hand, in the case shown in FIG. 6, both the fiber end gripping part 3 and the lens holder part 5 are required to be molded with high accuracy, and both the collimating lens 4 and the optical fiber 2 are required to have highly accurate outer diameter dimensions. Therefore, it still has serious drawbacks in terms of parts management and cost.

The present invention has been made with attention to the above points, and even if the optical fiber and the collimating lens are fixed in such a way that an axis misalignment occurs between the optical fiber and the collimating lens in the connector member, the connection loss increases. It is an object of the present invention to provide an optical fiber terminal and a method for manufacturing the same that can suppress the above.

"Means for Solving the Problems" The optical fiber terminal of the present invention includes a fiber end gripping part for fixing an optical fiber end, a collimating lens disposed opposite to the end surface of the optical fiber, and a collimating lens for collimating the optical fiber. and a lens holder portion for supporting and fixing the lens, and the optical axis of the light beam formed after the output light from the end face of the optical fiber passes through the collimating lens is tilted with respect to the optical axis of the optical fiber. The outer circumferential surface of the lens holder is cut into a cylindrical shape so that its axis coincides with the axis of the light beam.

In addition, the manufacturing method involves fixing an optical fiber end to a fiber end gripping part, arranging a collimating lens to face the end surface of this optical fiber, fixing this collimating lens in a lens holder, and then fixing the collimating lens in a lens holder. The outer periphery of the holder is cut into a cylindrical shape so that the optical axis of the light beam formed after the output light from the end face of the optical fiber passes through the collimating lens coincides with the optical axis of the light beam.

[Effect]

In this way, the outer periphery of the lens holder part is cut so that the optical axis of the light beam formed after the output light from the end face of the optical fiber passes through the collimating lens matches the axis of the lens holder part, so this lens If the connection is made based on the outer periphery of the holder part, connection loss can be minimized.

〔Example〕

1 to 3 are longitudinal cross-sectional views of each manufacturing process of the optical fiber terminal of the present invention, and the one in FIG. 1 shows the optical fiber terminal of the present invention after completion. The steps are arranged in the order of FIG. 3, FIG. 2, and FIG. 1, and the explanation will start from FIG. 3.

In FIG. 3, a metal connector member provided with a flange 12 on its outer periphery is provided with a through hole having a large diameter portion 7 and a small diameter portion 6 at its center, and a fiber end gripping portion 3 is formed. There is. Further, on the left side thereof, a lens holder portion 5 is formed which has a tapered surface 5' whose axis is substantially aligned with this through hole 6.

This through hole 6 has an inner diameter slightly larger than the outer diameter of the optical fiber 2, and the tapered surface 5' and the outer circumferential surface of the collimating lens 4 are not processed with such high precision.

Therefore, when the optical fiber 2 is adhesively fixed to the fiber end grip part 3 and the collimating lens 4 is adhesively fixed to the lens holder part 5, as shown in the figure, the light beam 9 output from the collimating lens 4 is The axis is tilted slightly downward in the figure with respect to the axis of the optical fiber 2.

Here, as shown in FIG. 2, for example, the outer peripheral surface of the lens holder portion 5 is cut using a copying lathe or the like while moving the cutting tool 13 in the direction of the arrow 14, using the axis of the light beam 9 as a reference.

As a result, as shown in FIG. 1, the outer circumferential surface of the lens holder section 5 is cut into a cylindrical shape so that its axis coincides with the axis of the light beam. After completion, as shown in Figure 1,
The lens holder portion 5 has a slightly inclined outer shape with an outer peripheral portion 5'' removed.

FIG. 4 is a longitudinal cross-sectional view of the optical fiber connecting portion, showing the state in which the optical fiber terminal of the present invention manufactured in this manner is used.

In the figure, on the left side, there is a high-precision machined or
Optical fiber terminals manufactured so that their axes align relatively accurately are arranged, and on the right side, due to axis misalignment, the first to
Optical fiber terminals that have been cut as shown in Figure 3 are arranged.

The two are connected by a connecting sleeve 16 having an inner diameter approximately equal to the outer diameter of each lens holder portion 5.

Within this connection sleeve 16, the light beam output from the left optical fiber 2 and the light beam output from the right optical fiber 2' are substantially equal and have the same axes.

Therefore, connection loss in this part is suppressed to a minimum.

[Modified example]

The optical fiber terminal and its manufacturing method of the present invention are not limited to the above embodiments.

For the optical fiber, not only the CI type but also a step index type (SI type), a plastic corer 4-eye fiber, etc. may be used. In addition, the outer periphery of the lens holder is machined into a cylindrical shape to serve as a reference surface for connection, but other parts are polygonal or knurled, and various parts necessary for connection fixation, etc. I don't mind having it installed. Further, the optical fiber terminal of the present invention may be used for coupling with a light emitting element or a light receiving element. At this time, the outer periphery of the lens holder portion is inserted and fixed into a suitable female holder or the like.

〔Effect of the invention〕

In the present invention, even if the processing accuracy of the fiber end gripping part and the lens holder part or the accuracy of the collimating lens and the outer diameter of the optical fiber are relatively low, the ends may be processed and fixed as they are. Then, by simply performing a certain cutting process, it is possible to obtain the same level of quality as a product manufactured with high precision. Therefore, according to the invention:
Optical fiber terminals with low splice loss can be manufactured at low cost.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the optical fiber terminal of the present invention, FIGS. 2 and 3 are perspective views and longitudinal cross-sectional views of each manufacturing process of the optical fiber terminal of the present invention, and FIG. is a vertical cross-sectional view of the optical fiber connection section using this, Figures 5 and 6 are vertical cross-sectional views of conventional optical fiber terminals, and Figures 7 and 8 are vertical cross-sectional views of the connection loss due to axis misalignment. It is an explanatory diagram. 2... Optical fiber, 3... Fiber end grip part, 4... Collimating lens, 5... Lens holder part, 9...・Light beam. Figure 1, Part 2] Figure 3, Figure 4, Figure 5, Figure 60 Figure 7, Figure 8

Claims (1)

[Claims] 1. A fiber end gripping part that fixes the end of an optical fiber, a collimating lens arranged opposite to the end surface of this optical fiber, and a lens holder part that supports and fixes this collimating lens. the optical axis of the light beam formed after the output light from the end face of the optical fiber passes through the collimating lens is inclined with respect to the optical axis of the optical fiber, and the outer peripheral surface of the lens holder is An optical fiber terminal characterized in that the optical fiber terminal is cut into a cylindrical shape so that its axis coincides with the axis of the optical beam. 2. Fix the optical fiber end to the fiber end gripping part, arrange a collimating lens to face the end surface of this optical fiber, and fix this collimating lens inside the lens holder. Then, the outer periphery of this lens holder is A method for manufacturing an optical fiber terminal, comprising cutting the optical fiber into a cylindrical shape so that the optical axis of the light beam formed after the output light from the end face of the optical fiber passes through the collimating lens coincides with the optical axis of the light beam.