JPS6160403B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a connector for communication optical fiber. In particular, it relates to an optical fiber connector that connects the ends of two optical fibers with low loss.

[Description of prior art]

FIG. 1 is a diagram showing the basic configuration of a conventional optical fiber connector. In the same figure, ferrule 4
is constructed by sequentially arranging a ceramic pipe 2 and a cylindrical tube 3 coaxially around an optical fiber 1, and this ferrule 4 is aligned by butting against a mating ferrule 4' within an alignment sleeve 5. Note that 6 and 6' are cables in which optical fibers 1 and 1' are coated with nylon.

Normally, when optical fibers are connected using the above configuration, connection loss occurs mainly due to mechanical imperfections of the optical connector (for example, axial misalignment, angular misalignment, etc.) and Fresnel reflection loss. As countermeasures to this problem, the former can be solved by introducing a highly accurate alignment technique, and the latter can be solved by eliminating the air layer that occurs between the abutting surfaces of the optical fibers 1 and 1'.

A specific method for eliminating Fresnel reflection loss is to polish the abutting end surfaces of the ferrules 4, 4' including the optical fibers 1, 1' shown in FIG. There is a method in which 1' is brought into direct contact (hereinafter referred to as "optical contact"). Furthermore, in order to easily obtain this optical contact effect, an optical fiber connector is constructed in which conical ferrules 7, 7' and a drum-shaped alignment sleeve 8 are molded in plastic as shown in FIG. There is.

As for the drawbacks of these conventional optical fiber connectors, firstly, in the case of Fig. 1, the ferrule 4,
A drawback is that a gap is likely to be formed between the end faces depending on the perpendicularity of the end faces of the end faces 4' and the opposed positions of the end faces in the alignment sleeve 5. For this reason, the reproducibility of optical contact deteriorates due to multiple attachment/detachment operations, resulting in variations in contact loss. In addition, in the case of FIG. 2, the contact surface of the ferrules 7, 7' is made small and the optical fiber 1
The ferrules 7, 7' have a conical shape.
Since the fitting error caused by the combination of the alignment sleeve 8 and the alignment sleeve 8 causes a slight gap between the butt end surfaces,
Difficult to obtain good optical contact. Furthermore, since the conventional method shown in Fig. 2 is configured to make connections by actively utilizing the elasticity of the plastic material, if the material is deformed due to the usage environment, good optical contact may not be achieved. There is a risk that it will not be possible to maintain it.

As described above, the quality of optical contact with conventional optical fiber connectors is greatly influenced by the fitting mechanism and the shape of the ferrule end face, and it is extremely difficult to realize optical fiber connectors with stable and reproducible performance. It was difficult.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned drawbacks, and an object of the present invention is to provide a low-loss optical fiber connector with which stable optical contact can be easily obtained.

[Features of the invention]

In the present invention, a fiber is fixed in a ferrule having an abutting surface whose tip end is narrowed into a generally rectangular shape, and the pair of ferrules are aligned within a sleeve so that the long axes of the abutting surfaces of the approximately rectangular shape intersect with each other. Characterized by butting.

[Explanation based on examples]

Hereinafter, the present invention will be explained based on the drawings.

FIG. 3 is an external perspective view of a main part of an optical fiber connector according to an embodiment of the present invention.

In the figure, 1, 1' are optical fibers, 2,
2' is a ceramic pipe, 9, 9' are ferrules, and 10, 10' are abutting surfaces made into rectangular shapes by narrowing the tips of the ferrules 9, 9' by tapered portions 11, 11'. The abutting surfaces 10, 10' are arranged vertically and horizontally on a plane perpendicular to the optical axis of the optical fibers 1, 1'.
It is formed with dimensions of 0.7 mm x 2.5 mm, and its surface, including the optical fibers 1 and 1', is optically polished to a near-mirror surface. The ferrules 9, 9' have a cylindrical structure similar to that shown in FIG.
It is characterized by a rectangular cross section at 0 and 10'.

The ferrule 9 and the opposing ferrule 9' are arranged using the alignment sleeve 5 of FIG. 1 so that the longitudinal directions of their abutting surfaces 10, 10' are substantially orthogonal to each other, as shown in FIG. do. With this arrangement, when the two ferrules 9, 9' are in contact with each other, the abutting surfaces 10, 10' of the ferrules 9, 9' have a small square surface centered on the optical fibers 1, 1', and this contact surface By applying a suitable pressing force from the outside, it is possible to create a complete mechanical contact between the end faces of both optical fibers without any gaps. That is, the cylindrical ferrules 9, 9'
After aligning and fitting the ferrules in the cylindrical sleeve 5, and narrowing the abutting contact surfaces of the ferrules 9 and 9', they are crossed in a cross shape, so there is no possibility of axial misalignment or angular misalignment when facing each other due to pressure. Gaps in the contact surface caused by mechanical imperfections can be extremely reduced. This means that, as mentioned above, the cross-shaped surfaces are subject to rotational moment applied to the ferrules 9 and 9' by external forces in the axial and rotational directions, especially external forces from the screw fasteners placed on the outer periphery. This can be proven by the fact that the displacement exerted on the contact surface is extremely small. By the way, the second
In the case of the conical ferrule shown in the figure, it is difficult to obtain stable optical contact because the rotational moment causes changes in the contact surface at any position within 360 degrees. The validity of the above effect is also supported by the measured data on the connection performance of the optical fiber connector, which will be described later.

Furthermore, since the abutting surface of the optical fiber connector of this example is mainly made of ceramic material, the contact surface protects the optical fiber and has excellent abrasion resistance, maintaining good mechanical strength performance. be able to. Therefore, stable optical contact can always be achieved even during repeated attachment and detachment, and connection characteristics with good reproducibility can be obtained. In addition, regarding the phenomenon in which dust, etc. generated during attachment/detachment adheres to the ferrule contact surface, the structure of the present invention has fewer contact surfaces and has a shape similar to a tapered edge, so the effect is extremely small and good optical contact can be achieved. You can get it all the time.

A sufficient effect can be obtained when the ratio of the long axis to the short axis of the abutting surfaces 10, 10' is approximately 1.5 to 15 times, and a ratio of approximately 3 to 4 times is particularly desirable.

Figure 4 shows a more specific embodiment of the present invention, which is an FC that is currently being standardized.
FIG. 2 is a structural diagram of a shaped optical fiber connector.

This fiber optic connector consists of a plug 12 and an adapter 17. The plug 12 includes the optical fiber 1, a ferrule 9 having the same configuration as in FIG. 14,
Positioning key 1 placed on the outer periphery of the frame 14
5, and a coupling nut 16 for screw fastening. On the other hand, the adapter 17 is composed of an alignment sleeve 18 and a housing 19, and cutout grooves 20 and 20' are formed at the input and output ends of the housing 19, respectively, and are offset by 90 degrees from each other.

To operate the connector 12, place the plug 12 into the adapter 1 by aligning the positioning key 15, which has been attached in advance in the long axis direction or short axis direction of the butt end faces, with the notch grooves 20 and 20' of the adapter 17.
7 and screwed together, the two ferrules are butted against each other in the alignment sleeve 18 and aligned, resulting in a mechanism in which the end surfaces of the two optical fibers are always in optical contact.

FIGS. 5 to 7 show test results for structures according to the present invention. This figure shows the characteristics of splice loss when two very thin optical fibers with a core diameter of 10 μm are connected using a connector. Figure 5 shows the characteristics when using a conventional optical fiber connector. FIG. 6 shows the characteristics of the optical fiber connector according to the embodiment of the present invention shown in FIG. The method for measuring this characteristic is to use two ferrules as a master, connect a sample ferrule to each of these two ferrules 5 to 10 times, and calculate the average value. It uses ferrule. FIG. 7 is shown for reference, and is a characteristic diagram when the optical fiber connector having the structure shown in FIG. 4 is connected in a structure in which the abutting ends of the ferrules are not perpendicular to each other.

As is clear from FIGS. 5 and 6, the connection loss of the connector of the present invention is 0.13 dB on average, which is much smaller than the average of 0.63 dB of the conventional connector. In particular, the reproducibility during attachment and detachment is stable, with a standard deviation of 0.1 dB or less, compared to the standard deviation of 0.33 dB for conventional connectors, making it possible to realize optical fiber connectors with good reproducibility.

In addition, the effect that good optical contact can be obtained by making the long axes or short axes of the abutting surfaces of the pair of ferrules substantially orthogonal to each other in the optical fiber connector of the present invention is due to the characteristics shown in FIGS. 6 and 7. It is also clear by comparing the

In the embodiment described above, the abutment surface at the tip of the ferrule has a shape in which the surface containing the optical fiber is narrowed into a rectangular shape, but the present invention is not limited to this embodiment, and as shown below. Modifications in which a ferrule tip is formed are also included in the present invention, and similar effects can be obtained with these as well.

In other words, the same rectangle 22 is also narrowed in the major axis direction (Fig. 8), elliptical 23 (Fig. 9), hyperbolic 24 (Fig. 10), and eyebrow-shaped. 25 (Fig. 11), trapezoid 26 (Fig. 12), and so on. Furthermore, the present invention can be applied to the structure of the ferrule main body in addition to the cylindrical shape, such as fan-shaped, rectangular, semicircular, etc., and the material of the ferrule can also be made of ceramic pipe for the optical fiber fixing part as in this embodiment. In addition to using, plastic or the like can also be used.

〔Effect of the invention〕

As explained above, the present invention maintains the optical fibers in a good condition by narrowing the tips of the ferrules into a roughly rectangular shape along the axial direction and by facing the rectangular end surfaces of the mating ferrules so as to intersect with each other. Optical contact can be made, connection loss can be reduced, and stability can be achieved during attachment and detachment. As described above, the present invention plays a very large role in improving the performance of optical transmission systems.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of conventional optical fiber connectors, FIG. 3 is an external perspective view of an optical fiber connector according to an embodiment of the present invention, and FIG. 4 is a more specific embodiment of the present invention. FIG. 5 is a splice loss characteristic diagram of a conventional optical fiber connector, FIG. 6 is a splice loss characteristic diagram of an optical fiber connector according to an embodiment of the present invention, and FIG. Figures 8 to 12 are splice loss characteristic diagrams for reference.
The figure shows a modification of the ferrule tip. 1, 1'... Optical fiber, 5... Alignment sleeve,
2, 2'... Ceramic pipe, 9, 9'... Ferrule, 10, 10'... Butting surface, 11, 11... Taper part, 12... Plug, 13... Spring, 15
...Positioning key, 17...Adapter, 20, 20'
...notch groove.

Claims (1)

[Scope of Claims] 1. A pair of ferrules into which the ends of two optical fibers are respectively inserted and fixed, and each of which has an abutment surface that includes the end surfaces of the two optical fibers in the same plane, and an alignment sleeve for aligning a pair of ferrules so that the end faces of the two optical fibers face each other; the pair of ferrules are inserted from both ends of the alignment sleeve so that the end faces of the optical fibers on the abutting surfaces face each other; In an optical fiber connector configured to optically connect two optical fibers by bringing them into contact, each of the two abutting surfaces is a plane perpendicular to the optical axis of the end surface of the optical fiber. , the outer peripheral shape of the plane has a shape having different lengths in two directions perpendicular to the optical axis, and when the two abutting surfaces are opposed in the alignment sleeve, the abutting surfaces of the pair of ferrules are What is claimed is: 1. An optical fiber connector characterized in that the outer peripheral shapes are butted against each other so as to be substantially perpendicular to each other. 2. The optical fiber connector according to claim 1, wherein the ferrule has a rectangular abutting surface, and is abutted so that the long and short sides of the rectangle are substantially perpendicular to each other. 3. The optical fiber connector according to claim 1 or 2, wherein at least a portion of the ferrule into which the optical fiber is inserted and fixed is formed of a ceramic material.