JP2989794B2 - Optical fiber connection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an optical connector used for connecting an optical fiber. More specifically, the present invention relates to an optical fiber connection device capable of significantly reducing insertion loss in a connection portion of a connector such as a single mode optical fiber applied to long-distance, large-capacity communication.

[0002]

2. Description of the Related Art In order to reduce transmission loss, a single mode optical fiber having an optical fiber core having a diameter of 7 to 10 .mu.m for transmitting an optical signal is generally employed. There are many factors that affect the insertion loss when connecting with a connector. It has been found that the largest factor is the amount of displacement of the axial centers of the optical fiber cores connected in opposition. For example, when the diameter of the optical fiber core is 10 μm, the deviation of the axis is 1 μm.
It is said that when it occurs, the insertion loss becomes 0.25 dB in the role and 1.8 dB in the case of 3 μm. As the target value, a maximum value of 0.5 dB and an average value of 0.2 dB or less are required. The maximum value of the axial center deviation of the optical fiber core satisfying this condition is 1.
6 μm, average value must be within 0.9 μm.

However, in actuality, a manufacturing error of the optical fiber itself, a manufacturing error of the ferrule, a fitting error when attaching the optical fiber to the ferrule, and the like are added, so that the center of the optical fiber core relative to the outer diameter of the ferrule is added. Is a maximum of about 3 to 4 μm and an average of about 1.5 μm, and it is impossible to achieve the target value as it is.

[0004]

Attention is paid to the phenomenon that the axis of the optical fiber core is eccentric to the outer axis of the ferrule at least in most of the optical connectors to which the optical fiber is attached due to the unavoidable accumulated error described above. Various proposals have been made on a method of minimizing the amount of deviation of the optical fiber core axis by matching the angle of the maximum eccentric position of the optical fiber core axis with respect to the ferrule outer diameter axis of the pair of optical connectors. ing. However, these methods have been inadequate because of the technical difficulty in manufacturing optical connectors and the limitation to only a few steps of adjustment. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber connection device which can greatly reduce insertion loss of a connection portion of an optical fiber connector with a simple structure.

[0005]

SUMMARY OF THE INVENTION To achieve the above object, an optical fiber connection device according to the present invention includes a pair of optical connector plugs and an alignment sleeve. The optical fiber connector plug includes a ferrule member in which an optical fiber is inserted and fixed in a center hole, and a threaded portion is provided at one end of an outer diameter portion, a screw hole rotatably engaged with the threaded portion, and one positioning member in the outer diameter portion. Cylindrical movable positioning ring with key,
The ferrule member includes a compression coil spring for biasing a ferrule member slidably fitted to an outer diameter portion of each of the ferrule members, and an engagement nut provided with a screw hole for coupling, wherein the alignment sleeve has an outer diameter portion at both ends. A key groove for inserting the positioning key of the movable positioning ring, a threaded portion to which an engagement nut of each optical connector is engaged, and a central portion through hole through which a tip of each ferrule can be inserted from both ends. Have been. Insert the positioning key of the movable positioning ring of each optical connector plug into the key groove of the alignment sleeve,
With the ferrule tip inserted into the through hole and the optical fiber connected, both or one of the ferrules can be rotated with respect to each positioning key to individually adjust the contact angle phase of each ferrule. The screw hole surface of the movable positioning ring and the screw surface of the outer diameter of the ferrule member can be fixed with an adhesive.

The optical connector of the present invention is constituted by the above-mentioned members. The procedure for assembling the optical connector is as follows.
First, the engaging nut is fitted to the outer diameter portion of the ferrule member, and then the ferrule member biasing coil spring is fitted. Finally, screw the positioning nut to complete. However, the positioning ring is screwed about 2 mm extra from the screw end face position of the ferrule member, a small amount of epoxy adhesive is applied to the tip of the screw portion of the ferrule member, and then the positioning ring is returned to the original position. Assemble two optical connectors in the same procedure.

[0007] Next, the procedure for attaching to the alignment sleeve is performed as follows. The ferrule tip of the first optical connector is inserted into the alignment hole of the alignment sleeve from one end of the alignment sleeve, and the engaging nut is screwed into the thread portion of the alignment sleeve outer diameter to complete the operation. Similarly, the second optical connector is attached. However, the second optical connector does not screw the engagement nut. In this state, by slightly pressing the second optical connector toward the center of the alignment sleeve, the ferrule tips of the optical connectors are brought into close contact with each other in a crimped state. Therefore, the optical fiber surface at the tip of the ferrule is also closely connected at the same time. At this time, the optical connector at the other end of the first optical connector is connected to the light source, and the optical connector at the other end of the second optical connector is connected to the optical power meter to measure the insertion loss. The optical fiber with respect to the outer diameter axis of the ferrule of the first optical connector based on the positioning key held in the key groove of the alignment sleeve by continuously rotating the ferrule member of the second optical connector until the ferrule member shows a value. The angle of the maximum eccentric position of the optical fiber core axis with respect to the outer diameter axis of the ferrule of the second optical connector can accurately match the angle of the maximum eccentric position of the core axis. After the adjustment, each positioning ring can firmly fix the pre-applied epoxy adhesive to the threaded portion of the ferrule member by heating curing or natural curing. Therefore, even when the optical connector is repeatedly attached and detached, there is no change in the adjusted angle, and no re-adjustment is required each time.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the drawings. FIG. 1 is a view showing a connection state of an embodiment of an optical fiber connection device according to the present invention. 2A to 2C are views for explaining the assembly of the optical fiber connection device according to the present invention. FIG. 2A is a cross-sectional view of an optical fiber connector, FIG. 2B is a cross-sectional view of an alignment sleeve, and FIG. 2C is an alignment sleeve and a ferrule tip. FIG. 3A and 3B are explanatory diagrams of the adjustment principle of the optical fiber core axis. The structure of the optical connector and the alignment sleeve of the present invention will be described with reference to FIGS. 2A to 2C. At one end of a cylindrical ferrule member 1, a ferrule portion 2 inserted into an alignment sleeve hole, a microhole 4 for inserting an optical fiber 3 and a stepped hole 6 for inserting a protective coating 5 of the optical fiber 3 are provided at the center. . On the outer diameter side of the ferrule member 1, a screw portion 7 is provided at one end, and a flange portion 8 is provided at the other end. The engagement nut 10 is provided with a screw hole 9 that engages with the alignment sleeve 15. The optical connector of the present invention is constructed by assembling members of a compression coil spring 11, a screw hole 12, and a positioning ring 14 provided with a positioning key 13 on an outer diameter surface for urging a ferrule.

The assembling procedure is as follows. First, the tip of the protective coating 5 is partially removed to fix the optical fiber 3 in the microhole 4 and the stepped hole 6 in a state where the optical fiber 3 is exposed. Is polished. Next, engaging nut 1
0, the compression coil spring 11 is fitted to the outer diameter portion of the ferrule member 1 in this order. Next, the positioning ring 14 is screwed into the thread portion 7 of the ferrule member 1 to complete the positioning. In order to fix the positioning ring 14 to the screw portion 7 of the ferrule member 1, the positioning ring 14 is screwed extra by about 2 mm, a thin epoxy adhesive is applied to the screw portion 7, and then the positioning ring 7 is returned. The epoxy adhesive penetrates into the meshing portion and can be firmly fixed.

At the center of the alignment sleeve 15, a through hole 16 for precisely inserting the outer diameter portion of the ferrule portion 2, and stepped holes 17a, 17 for inserting the positioning ring 14 at both ends thereof.
b, a threaded portion 18 for engaging the engaging nut 14 at both ends of the outer diameter
a, 18b and keyway 1 for inserting positioning key 13
9a and 19b are provided. FIG. 1 shows a state in which the optical connector of the present invention is attached to an alignment sleeve and optical fibers are connected. First, the engagement nut 10b is screwed into the threaded portion 18b of the alignment sleeve 15 while the positioning key 13b of the first optical connector B (only a part of which is shown) is inserted into the key groove 19b of the alignment sleeve 15. If the axis of the optical fiber core needs to be adjusted, the optical connector at the other end of the optical connector B is connected to the light source, the optical connector at the other end of the second optical connector B is connected to the light source, 2, the optical connector at the other end of the optical connector A is connected to the optical power meter, and only the positioning key 13 and the ferrule portion 2 are attached to the alignment sleeve without mounting the engagement nut 10 to the alignment sleeve as shown in the figure. 19a, the ferrule member 1 is inserted into the through hole 16 and the tip of the ferrule is gently brought into contact with the ferrule member 1 until the read value of the optical power meter reaches the best value.
Rotate the flange part 8 carefully left and right. When the best value is obtained, the optical connector A is pulled out of the alignment sleeve and removed, and the epoxy adhesive in the threaded portion of the threaded portion 7 of the positioning ring 14 and the ferrule member 1 is dried and solidified. By such a simple operation, insertion loss between the optical connector B and the optical connector A can be easily minimized.

Next, the principle of adjusting the optical fiber core axis will be described with reference to FIGS. 3A and 3B. FIG. 3A is a diagram illustrating a state before the adjustment where the axial deviation of the optical fiber core is maximized. That is, a state is shown in which the ferrules 2a and 2b are inserted into the through holes 16 of the alignment sleeve 15 as shown.
The keys 13a and 13b are respectively the ferrules 2a and 2b
The key grooves 19a and 19b are key grooves provided in the alignment sleeve 15. O is through hole 16
Oa is the axis of the optical fiber core Fa attached to the ferrule 2a. The axis of the optical fiber core Fa is located at a point decentered by Ea from the point O.
Similarly, Ob is the axis of the optical fiber core Fb attached to the fiber 2b, and is assumed to be at a point decentered by Eb from the point O. Further, the angle between the Oa point and the Ob point is 18
Assuming that there is a shift of 0 °, the axis shift amount E between the Oa point and the Ob point is E.
Can be easily understood that E = Ea + Eb. FIG. 3B is a diagram illustrating a state after the adjustment. That is, by rotating the fiber 2a by 180 ° clockwise or counterclockwise, the axis shift amount E ′ between the Oa point and the Ob point becomes:
E ′ = | Ea−Eb |, which can be minimized.

Further, the optical connector of the present invention is used not only for improving the insertion loss performance but also for a special optical fiber, for example, a constant polarization optical fiber which transmits an optical signal only at a certain angle of a cross section of the optical fiber. Also available. In the case of a constant-polarization fiber, it is easy to adjust the angle phase of the connection surface of the optical connector and fix the adjustment angle. it can.

[0013]

According to the present invention, the angle of the maximum eccentric position of the axis of the optical fiber of the pair of optical connectors to be connected is rotated steplessly with reference to the positioning key of the optical connector inserted into the key groove of the alignment sleeve. Due to the optical connector structure that can be adjusted, the deviation of the center of the pair of optical fiber cores to be connected is the difference between the absolute value of the eccentricity of the optical fiber core and the outer diameter axis of the ferrule of each optical connector (minimum axis deviation) Only could be improved exactly. Furthermore, since the positioning key of the optical connector can be firmly fixed to the ferrule member after the adjustment, there is no change in the adjustment angle even when the optical connector is repeatedly attached and detached, and no adjustment is required each time.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a connection state of an embodiment of an optical fiber connection device according to the present invention.

FIG. 2A is a sectional view of the optical fiber connector of the embodiment.

FIG. 2B is a sectional view of the alignment sleeve of the embodiment.

FIG. 2C is a diagram showing the alignment sleeve and the ferrule tip of the embodiment in correspondence with each other.

FIG. 3A is a schematic diagram illustrating the principle of adjustment of an optical fiber connection device according to the present invention.

FIG. 3B is a schematic diagram illustrating the principle of adjustment of an optical fiber connection device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical ferrule member 2 Ferrule part 3 Optical fiber 4 Micro hole 5 Optical fiber protective coating 6 Stepped hole 7 Screw part 8 Flange part 9 Screw hole 10 Engagement nut 11 Compression coil spring 12 Screw hole 13 Positioning key 14 Positioning Ring 15 Alignment sleeve 16 Through hole 17a, 17b Stepped hole 18a, 18b Screw 19a, 19b Keyway

Claims (3)

(57) [Claims] 1. An optical fiber connecting device for connecting a pair of optical fiber connector plugs using an alignment sleeve, wherein the optical fiber connector plug has an optical fiber inserted and fixed in a center hole, and a threaded portion at one end of an outer diameter portion. A ferrule member provided, a cylindrical movable positioning ring provided with a screw hole rotatably engaged with the screw portion and one positioning key on the outer diameter portion, and slidably fitted to an outer diameter portion of each of the ferrule members. A compression coil spring for urging the ferrule member, and an engagement nut provided with a screw hole for connection, wherein the alignment sleeve has a key groove for inserting a positioning key of the movable positioning ring into an outer diameter portion at both ends; A light configured to include a threaded portion to which an engagement nut of each optical connector is engaged, and a central through-hole into which a tip of each ferrule can be inserted from both ends. Aiba connecting device. 2. A positioning key of a movable positioning ring of each optical connector plug is inserted into a key groove of an alignment sleeve, and a tip end of a ferrule is inserted into a through hole to connect an optical fiber. hand,
2. The optical fiber connection device according to claim 1, wherein the contact angle phase of each ferrule can be individually adjusted by rotating both or one of the ferrules. 3. The optical fiber connection device according to claim 1, wherein the screw hole surface of the movable positioning ring and the screw surface of the outer diameter of the ferrule member are fixed with an adhesive.