JPS5999408A - Ferrule structure for optical connectors - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention Technical Field of the Invention The present invention relates to a ferrule structure for an optical connector, and more particularly to a ferrule structure that prevents reflections at the abutting portions of optical fibers that are aligned and fixed on an axis. It is.

(2), Technology background FIG. 1 is a diagram for explaining a conventional optical connector.

In the same figure, numerals 11 and 11' are optical fiber sheathing IJ12, 12' is an optical fiber, 13.13' is a ferrule for aligning and fixing the optical fiber, 14 is an alignment sleeve, and 15.15' is a bag hole)k Each is shown below.

As shown in FIG. 1, the ferrules 13 and 13' align and fix the original fibers l2 and 12', respectively, and are inserted into the alignment sleeve 14, and their opposing end surfaces 13a and 13'
a comes into contact and is removably fixed by cap nuts 15 and 15'. Such optical connectors are formed to reduce optical transmission loss by eliminating eccentricity of opposing optical fibers and angular deviation of end faces as much as possible. However, even if the opposing end surfaces 13a and 13'a of the ferrule are in contact and fixed, in most cases, the opposing ends m12a and 1 of the original fiber are
2'a do not come into close contact with each other, leaving a gap between them. Since air having a refractive index different from that of the optical fiber exists in this gap, multiple reflections occur between the opposing end surfaces 12a and i2'a of the optical fiber due to the difference in refractive index, resulting in so-called Fresnel loss. will occur. This Fresnel loss cannot be ignored compared to the transmission loss of the optical connector metal rod.

The second factor is 1, which indicates the state of multiple reflection between the opposing end faces i2a and 12'a of the original fiber. In the same figure, 12 and 1z indicate optical fibers r, 12a and 12'a are opposite end faces of the original fibers 12 and i2', respectively, A is the passing light, B and C are the multiple reflected lights, and G is the opposite end 1I012.
The gap dimensions between a, , and M'a are shown, respectively. In such a case, depending on the relationship between the size of the gap size G and the wavelength of the light, the multiple reflected light may interfere with each other and be amplified, or it may be attenuated.

However, the Fresnel loss is, for example, about 0.3 dB between glass (optical fiber) and air, and about 0.5 to 0.6 dB during loss fluctuations due to the above-mentioned interference. The structure of the ferrule in the connector is simple, and even if the machining accuracy is not perfect, the opposing end surfaces of the optical fibers can be butted together sufficiently closely, and there is no gap between the two surfaces. It is desirable that the

(3), Prior Art and Problems FIGS. 3 and 4 are diagrams for explaining the conventional ferrule structure. 3 is a basic drawing of the ferrule 23, (a) is a longitudinal cross-sectional view cut in the axial force direction, and (b) is an end face viewed from the direction of arrow (a). FIG. 4 is a diagram showing a state in which the optical fiber 22 is inserted into the ferrule 23 in FIG.
is a longitudinal sectional view, and (b) is an end view seen from the direction of the arrow in (a). In both figures, the ferrule 23 is made of stainless steel,
A narrow insertion hole 23b for inserting the optical fiber 22 along the axis is formed on the opposing end surface 23&, and a portion Vcl- on the opposite side to the opposing end surface 23a is formed from steel. 1: An accommodation hole 23c for accommodating the optical fiber coating 21' (5) is formed coaxially with the insertion hole 23b.The outer peripheral surface of the ferrule 23 is
It is coaxial with b and has a well polished finish of 4fik. Furthermore, the third
The recesses 23d, 23e, and 23f shown in Figure (b) are formed as a result of press working the insertion hole 23bi, as will be described later. The insertion hole 23b thus formed has a sufficient length and precision that cannot be obtained by drilling, and therefore the original fiber 22 can be stably fixed as shown in FIG. 4. As illustrated in FIG.
3a are polished perpendicularly to the axis, and as a result, the opposing end surfaces 22a and 23a are finished to be almost the same plane. However, these opposing end surfaces (22a, 2
3a) Surface polishing has its own limitations in processing accuracy.
For this reason, the opposing end surface (22a).

There is a problem in that the perpendicularity to the axis of 23a) cannot necessarily be ideally perpendicular. Therefore,
In the case of this ferrule structure, the opposing end faces of the optical fiber are not completely brought into close contact with each other, creating a gap between the two end faces, causing multiple reflections as explained in Figure 2 above, and causing fluctuations in the light level. There is a problem.

(4) 1. Purpose of the Invention In view of the above-mentioned problems of the prior art, the purpose of the present invention is to perform finishing processing so that the perpendicularity of the opposing end surfaces (butt end surfaces) of the 7-erule containing the optical fiber is ideally perpendicular to the axis. To provide a ferrule structure for an optical connector that allows opposing end faces of optical fibers to be brought into close contact with each other even when the optical fibers are not connected to each other, and that does not create a gap between the two end faces.

(5) Structure of the invention In order to achieve this object, according to the present invention,
In a ferrule in which a pair of optical fibers are aligned on a straight line in an optical connector and each of the optical fibers is aligned and fixed on an axis so that the end faces of the optical fibers are aligned and fixed on the axis, an inner end face that is the opposite end face of the ferrules is An optical fiber insertion hole (if
The optical fiber insertion hole is formed to extend toward the inner end surface of the TJ ferrule, and the optical fiber insertion hole in the inner end surface portion is formed into an enlarged hole having an opening diameter approximately twice or more than the outer diameter of the original fiber. A ferrule structure for an optical connector is provided, which is characterized by being provided with a fiber adhesive layer.

(6), Examples of the invention The following are examples of the invention? This will be explained in detail based on the drawings.

5 to 7 are diagrams showing embodiments of ferrule structures according to the present invention.

FIG. 5 is a single view of the ferrule 33, (A) is a longitudinal cross-sectional tooth cut in the axial direction, and (B) is an end view seen from the direction of arrow E in (A). FIG. 6 is a diagram showing a state in which the optical fiber 32 is inserted into the ferrule 33 of FIG. 5 together with its covering part 31 and fixed with an adhesive 34, and (A) is a longitudinal cross-sectional view;
(B) is an end view seen from the direction of arrow E in (A). FIG. 7 is a partially enlarged detailed view of the opposite end surface portion of FIG. 6(A).

In these sections, the reference numeral 31 indicates the coating part of the optical fiber;
32 is an optical fiber, 33 is a ferrule, 34 is an adhesive, and 35 is an adhesive layer at the end surface. The ferrule 33 is made of stainless steel, and has a narrow insertion hole 33b for fitting and inserting the optical fiber 32 along the axis on the opposite end surface (butting end surface) 33& side, and the opposite end surface. A storage hole 33c for accommodating the optical fiber coating 31 is formed coaxially with the insertion hole 33b on the opposite side of the optical fiber 33a, and the insertion hole 33b on the opposing end surface 33a has a diameter approximately equal to the outer diameter of the optical fiber 32. 2
The enlarged hole 733d has an opening diameter that is more than twice as large. The outer peripheral surface of the ferrule 33 is coaxial with the insertion hole 33b and is precisely polished.

Now, by forming the insertion hole 33b in the opposing end surface 33a portion into the enlarged hole 33d as described above, as shown in FIG.
is filled to form an adhesive layer 35, which is a feature of the present invention. The adhesive 34 is made of epoxy resin or the like.

Therefore, the hardness of the adhesive 34 is υ lower than that of both the optical fiber 32 and the 7-element rule 330.
The hardness of the optical fiber 32 is also lower than that of the optical fiber 32. In general, the lower the hardness of a material, the easier it is to be polished, and conversely, the higher the hardness, the harder it is to be polished. Therefore, Figures 6 and 7
In the case of the ferrule structure shown in the figure, the amount of polishing during polishing of the opposing end surfaces (butt end surfaces 32a, 33a) differs depending on each member. In other words, the amount of polishing is greatest for the adhesive 34, followed by the ferrule 3.
3, and the optical fiber 32 is the smallest.
In the case of the conventional example shown in the figure, the 5-element fiber 22 and the felt 23
Because of the structure in which the optical fibers 220 and ferrules 230 are in close contact with each other, the opposing end surface 22a of the optical fiber 220 and the opposing end surface 23a of the ferrule 230 are finished to be almost the same plane by the end surface polishing process. On the other hand, in the case of this embodiment shown in FIG. 6, since the adhesive layer 35 is provided between the optical fiber 32 and the ferrule 33, the abrasive grains enter the recesses of the adhesive in the adhesive layer 35. Therefore, the difference in the amount of polishing between the original fiber 32 and the ferrule 33 is much greater than in the conventional example. As a result, as shown in FIG.
) is polished to a protruding state. Therefore, when a pair of ferrules formed in such a structure are brought into contact with each other in their opposing end surfaces within an optical connector, the opposing end surfaces 32a of the original fibers 32 first come into contact with each other, and then the opposing end surfaces 33a of the ferrules come into contact with each other. They will come into contact with each other.

As a result, even if the perpendicularity of the opposing end surfaces 33a of the ferrule is not finished to be ideally perpendicular to the axis, the opposing end surfaces 32a of the optical fibers are strongly pressed against each other and come into close contact9. The formation of a gap between the end surfaces 32a is completely prevented.

Incidentally, the recesses 33e, 33f, and 33g shown in FIG. 5 are made of stainless steel or the like having an inner diameter corresponding to the receiving hole 33c and an appropriate wall thickness.The recesses 33e, 33f, and 33g shown in FIG. This is the result of pressing inward. This manufacturing method is ``Method for manufacturing support for optical fiber coupling device-1'' (Japanese Patent Application Laid-open No. 11309/1983) which the inventors of the present invention have already proposed. The insertion hole of the ferrule 33 can be formed to a sufficient length that cannot be obtained by trill processing, etc., and the enlarged hole 33d can also be easily formed into an IC. Since the eccentricity and angular deviation of the fibers within the fiber 33b are small, and at the same time adhesive strength is ensured, the fibers can be fixed in a sufficiently stable manner.
It is possible to align and fix within the ferrule 33 so that it can sufficiently withstand the pressure even if it is subjected to instep pressure.

(7) Effects of the First Invention As explained in detail above, the ferrule structure for the original connector according to the present invention has a simple structure, and by providing a contact layer around the end face of the pair of optical fibers, It is possible to polish and finish the opposing end face of the fiber so that it protrudes beyond the opposing end face of the ferrule, and for this reason, it is possible to always bring the opposing end faces of the optical fibers into perfect contact with each other, and as a result, there is no gap between the two end faces. It is possible to completely prevent the occurrence of Fresnel loss, and therefore, there is a great effect that it is possible to optically connect optical fibers with almost no Fresnel loss.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of a conventional optical connector, Figure 2 is a diagram showing the state of multiple reflections between opposing end faces of optical fibers, and Figure 3 is a diagram showing the state of multiple reflections between opposing end faces of optical fibers.
The figures show a vertical cross-sectional view (a) and an end view (b) showing the conventional ferrule structure for the original connector, and a vertical cross-sectional view showing a state in which an optical fiber is inserted and fixed together with its covering part into the ferrule shown in Fig. 4fd and Fig. 3. A top view (A), an end view (B), and FIG. 5 is a longitudinal sectional view showing the ferrule structure for an optical connector according to the present invention.
(a) and end view 1 (b), Fig. 6 is a vertical cross-sectional view showing the state in which the optical fiber is inserted and fixed together with its coating into the ferrule shown in Fig. '5), and end view 1 (b), FIG. 7 is a partially enlarged detailed view of the opposite end surface portion of FIG. 6(A). 31...--Coating portion of original fiber, 32...
・Optical fiber, 32a... Opposite end face of optical fiber (butt end face), 33... Ferno lz
, 33a... Opposite end face of ferrule (butt end face), 33b... Original fiber insertion hole, 33c...
...Accommodating hole of optical fiber coating part, 33d...
...Enlarged hole, 34...Adhesive, ? , 5...
...Adhesion r%. Patent applicant Fujitsu Ltd. Patent agent Akira Yoiki Patent attorney Ome Nishidate Akio Uchida Patent attorney Akira Yamaguchi Figure 3 Figure 7

Claims (1)

[Claims] 1. In a ferrule containing FF3 in which a pair of original fibers are all aligned on a straight line in the original connector and the optical fibers are aligned and fixed on the @ line so that their end faces face each other, the opposing end faces of the ferrules. A hole for accommodating the covering part of the original fiber is formed along the axis Ka in the outer end surface side portion corresponding to the same end surface, and a hole for inserting the optical fiber into which the optical fiber is inserted is coaxially communicated with the accommodating hole. The optical fiber insertion hole is formed to extend toward the inner end surface of the 7-hole rule, and the optical fiber insertion hole in the FfiV3 end surface portion is formed into an enlarged hole having an opening diameter approximately twice or more than the diameter of the original fiber. A ferrule structure for optical connectors that features an adhesive layer for fibers.