JPH0954221A - Optical fiber core alignment method and alignment device - Google Patents

Abstract

(57) Abstract: A core axis aligning method for connecting an optical fiber with low loss, a small and lightweight simple core axis aligning apparatus, an optical connector making method and the apparatus are provided. SOLUTION: In a method of connecting optical fibers 1-1 and 1-2 on a fixed V groove, end faces of two optical fibers 1-1 and 1-2 to be connected are butted on V grooves 9a and 9b. First procedure and each optical fiber 1-1, 1-
While rotating 2 on the V-shaped grooves 9a and 9b, the core image of the optical fiber was observed from one side surface direction of the optical fiber, and each observed core image was divided into two by the central axis of the optical fiber. The second procedure for finding the rotation angle of each optical fiber so that each core image is located farthest from the central axis of the optical fiber and is on one side of the observation field, and each optical fiber is set to the rotation angle. Third to fix
And the procedure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core axis aligning method for connecting an optical fiber with low loss, a compact and lightweight simple core axis aligning apparatus, an optical connector manufacturing method and an apparatus therefor.

[0002]

2. Description of the Related Art As is well known, if the core axes of abutted optical fibers are misaligned with each other, the connection loss increases. In order to connect the optical fibers with low loss, it is necessary to reduce the axial misalignment between the cores of the optical fibers to be connected as much as possible.

(1) FIG. 6 is a diagram for explaining an axial alignment method of a conventional core direct-view type optical fiber connecting device (Japanese Patent Laid-Open No. Sho 60).
-46509). FIG. 7 is a diagram for explaining a conventional method for observing a core. As shown in FIG. 7, the optical fiber 1 is irradiated with the parallel light 2, and the objective lens 3 of the microscope is attached to the rear portion (range OB) of the core 5 with respect to the irradiation direction.
When the observation surface 4 is set and the transmitted light 6 is observed, the core 5 is observed as two dark lines 7 (in the direction perpendicular to the paper surface).

The apparent position of the core with respect to the center axis of the optical fiber is generated by the lens effect of the optical fiber, and about 1 time of observation is performed at the observation surface position of 1/4 of the outer diameter of the optical fiber shown in FIG. Observed at magnification, and optical fiber 1
It is observed by magnifying it to the observation magnification of about 1.5 in the central part of the optical fiber, and when the position of the observation surface is approached to the microscope objective lens 3 side, the observation magnification is reduced to 1 time or less. To be done. The true core position described below is the actual core position with respect to the apparent core position and is not affected by the lens effect of the optical fiber, that is, the observation magnification due to the lens effect of the optical fiber 1 is It is obtained in the case of 1 time.

The connection procedure will be described with reference to FIG. First, the core images of the abutted optical fibers 1-1 and 1-2 are observed from two directions of y and z, and the position of the core image of the optical fiber is detected. This operation needs to be performed on the two abutted optical fibers 1-1 and 1-2. At this time, since the optical fiber has a lens effect, the observation surface of the objective lens is moved to a predetermined position of the optical fiber by the microscope 8 with the fine adjustment mechanism for focus adjustment every time the core image is detected.
It must be set with high accuracy. In this way, the core position is detected with high accuracy four times in total. As shown in FIG. 6, by using the mirror M, both the illumination system and the light receiving system can be reduced to two systems. Next, based on the true core position, the microcomputer calculates the amount of axial deviation between the cores. Finally, in two directions of y and z, at least one of the optical fibers 1-1 and 1-2 is moved by the two-way V-groove fine movement mechanism to perform core axis alignment, and the optical fibers are connected with low loss.

(2) FIG. 8 is a view for explaining an axial alignment portion of a simple optical fiber fusion splicing device using a conventional fixed V groove axial alignment. As shown in FIG. 8, the optical fibers 1-1, 1
-2 are butted against each other on the axis alignment table 9 having the fixed V groove 9a, and simply aligned on the basis of the optical fiber clad outer diameter,
The optical fibers 1-1 and 1-2 are connected to each other.
Even if there is a difference in outer diameter between the optical fibers 1-1 and 1-2, or if there is an axial misalignment between the center axes of the optical fibers before connection, the optical fiber abutting portion will have a relatively long time (around 10 seconds). ) When heating and fusion splicing, the surface tension acts on the fused silica glass at the end of the optical fiber, and the self-centering effect between the abutted optical fibers causes the optical fibers 1-1,
The center axes of 1-2 coincide with each other.

(3) FIG. 9 is a view for explaining a conventional connector connection for forming and connecting an optical fiber with a ferrule. As shown in FIG. 9, the connector connection is performed by passing an optical fiber through the optical fiber insertion through hole 11 of the ferrules 10-1 and 10-2, and fixing it to the ferrule fitting pin hole 12.
Insert a mating pin (not shown) into the ferrules 1
By joining 0-1 and 10-2, as a result, the optical fibers 1-1 and 1-2 are positioned and connected.

[0008]

[Problems to be Solved by the Invention]

(1) However, in the case of the core direct-view optical fiber connecting device of FIG. 6, a microscope with a focus adjustment fine movement mechanism for observing the core image from two directions, a core axis deviation calculation unit, and a two-way V groove fine movement mechanism are indispensable. , Both the detection time and the alignment time are long,
Multiple fine movement mechanisms and their high-rigidity support members have become larger,
Therefore, the weight becomes heavy, and the price increases as the core detection and the fine movement mechanism become more accurate.

Further, in recent years, with the improvement of optical fiber manufacturing technology, the amount of variation in the amount of core eccentricity and the outer diameter of the cladding has become smaller. Therefore, as the manufacturing error of the optical fiber becomes smaller and the dispersion of the parameters of the optical fiber structure becomes smaller, the error of the optical system such as the depth of focus and aberration, the resolution in the CCD image pickup unit, and the amount of core axis deviation are set to zero. In order to sufficiently reduce the core position detection / positioning error due to the fine movement positioning mechanism, etc., the conventional device requires a more accurate core detection system and the positioning fine movement mechanism, resulting in a larger connection device. However, it becomes heavy and expensive, making it impractical.

(2) In the case of the simple optical fiber fusion splicing device of FIG. 8, the central axes of the optical fibers are aligned by the self-centering effect of the optical fibers. However, the direction of eccentricity of the core axis with respect to the optical fiber center axis (hereinafter,
The eccentricity of the core is random), and when the optical fibers are butted against each other on the fixed V-groove, the eccentricity of the core causes the core axis deviation, and the connection loss is equal to the amount of the axis deviation generated at that time. Grows larger. The maximum deviation of the core axes of the abutted optical fibers is the sum of the core eccentricity of the optical fibers. A large splice loss occurs in the vicinity of the optical fiber abutment positional relationship that produces the maximum amount of core axis deviation.

For example, the core of a normal single-mode optical fiber is allowed to have a maximum eccentricity of 1 μm. Now, when optical fibers with a core eccentricity of 1 μm and core eccentricity of 0.9 μm are randomly abutted with their center axes aligned, the probability density function for the axial misalignment between cores is calculated. As shown. FIG.
Therefore, in the worst case, an axis deviation of 1.9 μm will occur, and when this axis deviation is converted into a loss, it will be about 0.8 dB. Usually, another loss error factor such as the optical fiber cutting angle will be added, and the connection loss will be further increased. There is a greater risk of starting over.
For example, in the case of fusion splicing, if it exceeds 0.5 to 0.6 dB, the connection may be re-established as a connection failure. Failure will result in longer connection times. Therefore, conventionally, it has been desired to reduce the frequency of such reconnection and improve the connection efficiency.

(3) In recent years, ferrules have been manufactured with extremely high precision. For example, according to the IEICE Technical Report CS95-49, OCS95-15 (1995-06) p.56 "Design and Characteristics of Optical Cable with Ultra High Density Both-Ends Connector", refer to FIG. Then, at present, the axial deviation error caused by the gap of the optical fiber insertion through hole 11 is 0.
2 μm, the axial deviation error due to the gap between the ferrule fitting pin hole 12 and the fitting pin is about 0.5 μm, and the manufacturing error at the center of the optical fiber insertion through hole 11 is about 0.6 μm. Compared to this, the current allowable value of the core eccentricity of the optical fiber is 1μ.
m (at this time, the maximum axis deviation error is 2 μm). As described above, the manufacturing error factor of the connector which causes the axial deviation and the core eccentricity amount of the optical fiber have reached the same level. As a result, when the optical fibers are butted against each other, the misalignment between the central axes of the optical fibers has become very small. Therefore, also in the case of the connector connection of FIG. 9, when the optical fibers are abutted with each other, the core axis misalignment loss due to the core eccentricity of the optical fibers becomes a problem, as described in (2) above. .

However, this core misalignment loss has been regarded as an unavoidable loss. Therefore, after finishing the optical fiber by forming a terminal with a ferrule, it is connected to a reference connector or the like to evaluate the connection loss. For example, in the case of connector connection,
(Ferrule fitting pin hole 12 and optical fiber insertion through hole 1
If the allowable limit loss exceeds 0.6 to 1 dB due to the addition of an error in the relative position with respect to 1 and the like, it is often re-connected as a connection failure. If it fails, the connection time will increase accordingly. Conventionally, it has been desired to reduce the frequency of such reconnection and improve the connection efficiency.

[0014]

A first optical fiber core alignment method of the present invention which solves the above problems is a method of connecting optical fibers on a fixed V groove. The first procedure of abutting the end faces on the V groove, and rotating each optical fiber on the V groove,
The core image of the optical fiber is observed from one side surface direction of the optical fiber, and each of the observed core images is on one side of the observation field of view divided into two by the central axis of the optical fiber,
And a second procedure for finding the rotation angle of each optical fiber so that each core image is farthest from the center axis of the optical fiber, and a third procedure for fixing each optical fiber to the rotation angle. It is characterized by

The configuration of the first optical fiber aligning device is as follows:
A fixed V groove for abutting the end faces of two optical fibers to be connected, an optical fiber rotation angle determining mechanism for rotating the abutted optical fiber on the fixed V groove, and fixing the rotation, and the optical fiber from one side surface. And a one-way core image observation device for observing the core image.

The second method for aligning the core axes of the optical fibers is a method of connecting the optical fibers on the V groove, and a first step of abutting the end faces of the two optical fibers to be connected on the V groove, respectively. While rotating the optical fiber on the V groove, the core image of the optical fiber is observed from one side surface direction of the optical fiber, and each observed core image is divided into two by the central axis of the optical fiber. A second step of finding the rotation angle of each optical fiber so that each core image is located farthest from the central axis of the optical fiber, and fixing each optical fiber to the rotation angle. The third procedure and moving at least one of the V-grooves in a direction orthogonal to the plane formed by the optical axis of the objective lens used for the observation and the central axis of the optical fiber to connect the optical fiber to be connected. 4 to the axial combined cores of Iba
It is characterized in that it consists of the procedure of.

Further, in the construction of the second optical fiber axis aligning device, in the device for connecting the optical fibers on the V groove, the end faces of the two optical fibers to be connected are abutted, and at least one of them is in the optical fiber observation direction. And a V-groove configured to move in a direction perpendicular to a plane formed by the optical fiber central axis, and an optical fiber configured to rotate the abutted optical fiber on the V-groove and fix the rotation. It is characterized by comprising a fiber rotation angle determining mechanism and a core image unidirectional observation device for observing the core image of the optical fiber from one side surface.

In the above first or second optical fiber alignment method, in which the optical fiber is placed on the V groove and connected, after the optical fiber is connected, the position of the observation surface of the core image one-way observation device with respect to the optical fiber is set. Based on the above, a procedure for calculating the true core axis deviation amount and estimating the core axis deviation loss is added.

Further, in the method for producing an optical connector of the present invention, the end portion of the optical fiber is formed with a ferrule and the ferrules are butted against each other to connect the connector, and the optical fiber is inserted into the optical fiber insertion through hole of the ferrule. The first step of placing the optical fiber in the V-groove, just before fixing it with an adhesive or mechanically, and
While rotating on the groove, the core image of the optical fiber is observed from the one side surface direction of the optical fiber, and the core image is on one side of the observation field divided into two by the central axis of the optical fiber. A second step of finding the rotation angle of the optical fiber so that the core image is positioned and the farthest from the central axis of the optical fiber; and a third step of fixing the optical fiber at the rotation angle. And a fourth step of fixing the optical fiber to the ferrule so that the eccentric direction of the core of the optical fiber to be connected is the same direction at the ferrule joining surface when the connector is connected. .

The optical connector manufacturing apparatus of the present invention has a fixed V groove for mounting an optical fiber in an optical connector manufacturing tool for forming an end of an optical fiber with a ferrule.
An optical fiber rotation angle determining mechanism for rotating the optical fiber on the fixed V groove and fixing the rotation of the optical fiber;
The core image unidirectional observation device for observing the core image of the optical fiber from one side surface direction of the optical fiber, and the eccentric direction of the core of the optical fiber to be connected should be the same direction at the ferrule joint surface when the connector is connected. It is characterized by comprising a ferrule positioning table provided and a slide mechanism for inserting the optical fiber into the optical fiber insertion through hole of the ferrule while keeping the core eccentric direction of the optical fiber.

[Operation] The cores of the two abutted optical fibers have the same eccentric direction. Therefore, when the optical fibers are butted against each other or connected by aligning the optical fiber central axes, the amount of deviation between the core axes of the butted optical fibers is minimized. At this time, the butt loss of the optical fiber is also minimized.

Further, since the two cores are eccentric in the same direction and the two cores are butted against each other in the same plane, accurate core axial alignment can be achieved by only one-directional axial alignment. In this case, regardless of the lens effect of the optical fiber, it is possible to perform accurate core axis alignment by using an apparent core image obtained by one-time simultaneous observation of core images.

[0023]

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

[First Embodiment] FIGS. 1 and 2 are views for explaining a core axis aligning method of an optical fiber according to a first embodiment of the present invention.

FIGS. 1A and 1B are views showing the state of the optical fiber butting portion displayed on the LCD (liquid crystal display screen). FIG. 2 is a view showing the movement of the core with respect to the optical fiber center axis of the optical fiber abutting portion displayed on the LCD, as viewed from the optical fiber cross section (x) direction, corresponding to FIGS. 1 (a) and 1 (b). It shows the situation. In FIG. 1, the shaded portions of the optical fibers 1-1 and 1-2 are dark areas, and the width of the dark areas is determined by the numerical aperture of the objective lens (angle limitation of light rays that can be received) and the position of the observation surface. As described above with reference to FIG. 7 in the “Prior Art” section, in FIG. 2, when the cores are decentered, the optical fibers 1-1 and 1-2 were fixed when observed from the z direction. When the optical fibers 1-1 and 1-2 on the V-shaped grooves 9a and 9b are rotated, the two dark lines 7-1 and 7-2, which are core images, move closer to or farther from the center axis of the optical fiber. Now, the core images 7-1 and 7-2 are the optical fibers 1-1 and 1-2.
Each of the optical fibers 1-1, 1- is located on one side of the observation field of view divided into two by the central axis of the optical fiber, and each core image is located farthest from the central axis of the optical fiber.
By finding the rotation angle of 2 and fixing the respective optical fibers to the rotation angle, the amount of axial misalignment between the cores of the abutted optical fibers can be set to the minimum (see FIG. 2B).

It can be seen from FIGS. 1 and 2 that the axial misalignment between the cores of the optical fibers 1-1 and 1-2 can be set to a minimum by observing from one direction. That is, in FIG. 10, the core axis deviation amount can be set to the minimum value.

On the other hand, in FIG. 2B, of the V grooves 9a and 9b on which the optical fiber is mounted, the V groove 9a or 9b on which one of the optical fibers is mounted is movable in the y direction.
With the groove fine movement mechanism, either one of the optical fibers can be moved in the y direction so that the axes of the core images 7-1 and 7-2 coincide with each other (see FIG. 2C). When the optical fibers 1-1 and 1-2 are rotated on the V groove, the rotation directions of the optical fibers 1-1 and 1-2 are selected so that the twist generated in the optical fiber after connection is minimized. Good to connect.

Here, when the V-groove 9a and the V-groove 9b are fixed, the procedure for setting the axial misalignment amount between the cores to the minimum can be summarized as follows. (1) "First procedure" in which the end faces of the two optical fibers 1-1 and 1-2 to be connected are butted against each other on the V grooves 9a and 9b.
(2) Connect the optical fibers 1-1 and 1-2 to the V groove 9
While rotating on a and 9b, the core images of both optical fibers are observed from one side surface direction of the optical fiber, and each of the observed core images is divided into two parts by the central axis of the optical fiber. “Second procedure” for finding the rotation angle of each optical fiber so that each core image is located farthest from the center axis of the optical fiber on one side, and (3) each light at that rotation angle. It consists of the "third procedure" of fixing the fiber. (4) Further, in the above first, second, and third procedures, at least one of the V grooves is in a direction orthogonal to the plane formed by the optical axis of the objective lens used for the observation and the optical fiber central axis. When the "Fourth procedure" for aligning the cores of the optical fibers to be connected with each other is added, the core alignment can be performed more accurately.

Next, FIG. 3 is a view for explaining an optical fiber core axis aligning device which is one of the devices for realizing the first embodiment of the present invention. As shown in FIG. 3, the optical fiber connecting device of the present invention includes V-grooves 9a and 9b that abut the optical fibers 1-1 and 1-2, and the optical fibers 1-1 and 1-2 that abut each other. An optical fiber rotation angle determining mechanism 13 for rotating the optical fibers 1-1, 1-2 at arbitrary rotational positions by rotating the optical fibers 1-1, 1 from one direction. -2 core image 7-1,
It is mainly composed of a core image unidirectional observation device 14 for observing 7-2. In addition to the above configuration, the optical fibers 1-1,
A fusion splicing device is configured by adding a 1-2 butting part heating unit (arc discharge or glow discharge heating, gas heating, laser heating device) and a control mechanism for moving the optical fiber in the axial direction and making abutting. .

Here, the optical fiber rotation angle determining mechanism 13
Is an optical fiber holding part 13-1 having a cylindrical outer circumference, a sliding tube 13-2 of the optical fiber holding part, and a rotation fixing part 13 of the optical fiber holding part 13-1 provided on the sliding tube 13-2. -3
It is composed of Here, the optical fiber grip 13-1
Is configured so that it can rotate at least once. Further, the optical fiber gripping portion 13-1 and the sliding cylinder 13-2 are configured to be split into two at a surface including the optical fiber axis. Optical fiber 1
A slight bending force is applied to -1, 1-2 so that the optical fiber rotates about the optical fiber center axis as a rotation axis while always in contact with the fixed V groove. Optical fibers 1-1 mounted on the grooves 9a and 9b
A small angle is formed with the center axis of 1-2. The V-groove clamp 90 is attached to the optical fiber so that the optical fiber rotates while surely contacting the V-groove.
You may make it the structure lightly pressed in a groove.

By the way, as shown in FIG. 3, the V groove 9a,
9b and the V-groove clamp 90 are combined, and if the covering portions 1-1-0 and 1-2-0 of the optical fibers 1-1 and 1-2 are directly turned by hand, the optical fiber rotation angle is functionally. It has the same function as the determining mechanism 13. Therefore, if the V-grooves 9a and 9b and the V-groove clamp 90 are used as an optical fiber rotation angle determining mechanism instead of the optical fiber rotation angle determining mechanism 13 shown in FIG. 3, the optical fiber rotation angle determining mechanism shown in FIG. The mechanism 13 may be removed.

The core image unidirectional observation device 14 includes a parallel light source 14-1, a microscope 14-2, a CCD image pickup device 14-3, a signal drive control board 14-4 and an LCD (liquid crystal display screen). 14-5.

In FIG. 3, the collimated light from the collimated light source 14-1 is applied to the optical fiber abutting portion, and the observation surface of the objective lens of the microscope 14-2 is seen from the core as viewed from the CCD image pickup device 14-3 side. When it is set to the front (“setting range OB” shown in FIG. 7) and the transmitted light is observed by the core image one-way observation device 14, the core image can be observed by the LCD 14-5.

The optical fibers 1-1 and 1-2 are connected to the V grooves 9a and 9
When abutting on b, the observation surface of the objective lens is set to the same position with respect to the optical fibers 1-1 and 1-2, and the sizes of the two core images (distance between two dark lines) are the same. At the same time, the position of the core with respect to the center of the optical fiber is also observed at the same observation magnification. Therefore, regardless of the position of the observation surface of the microscope objective lens with respect to the optical fiber, therefore, even if the position of the apparent core image is used,
Accurate core alignment is possible.

Further, since the two core images are both on the same observation plane, the core axes are aligned in at least one of the V grooves 9a and 9b in one direction (y direction: the direction of the objective lens). This is possible if the fine movement mechanism is movable in a direction orthogonal to the plane formed by the optical axis and the central axis of the optical fiber (fourth procedure).

Further, as the position of the observation surface of the microscope objective lens is set closer to the center of the optical fiber, the lens effect of the optical fiber is increased, and the apparent core position with respect to the center axis of the optical fiber is enlarged and observed. The more accurate axis alignment becomes possible.

Next, since the center axes of the fibers are deviated in the observation (Z) direction due to variations in the outer diameter of the optical fiber, for example, the set position of the observation plane of the objective lens is the abutted optical fiber 1-1. , 1-2 are different. In FIG. 7, even if the center axes of the optical fibers abutted on the V-groove are deviated in the observation direction, the core image can be observed if the position of the observation surface of the objective lens is within the range of OB, and the optical fibers 1-1, 1- Regarding 2, the eccentric directions of the cores can be aligned. In addition to the observation direction,
Even if the center axes of the optical fibers are displaced in the y direction due to dust or the like on the surface of the V groove, if the core image can be observed, the eccentric directions of the cores of the optical fibers 1-1 and 1-2 can be aligned. In the abutted optical fibers, if the heat fusion time is about 10 seconds, the center axes of the optical fibers coincide with each other due to the self-centering effect after the fusion splicing. Therefore, even if the center axes of the abutted optical fibers are deviated in the observation direction or the y direction before the connection, the cores are separated by the self-centering effect after the connection (as shown in FIG. 2B). The closest.

However, in the case of accurately aligning the core axes using the one-direction (y-direction) V-groove fine movement mechanism, before connecting, V
It is necessary to remove dust on the groove surface and also remove the coating (primary coat) of the optical fiber. Further, as is well known, the discharge power and the discharge time (about 1 second) are selected so as to reduce the influence of the self-centering effect.

Conventional optical fibers have large variations in structural parameters such as outer diameter and core eccentricity. Consider a case where a conventional optical fiber having a relatively large core eccentricity (existing) is connected to a recent optical fiber having a small outer diameter and a small core eccentricity. For example, when the variation of the outer diameter of the conventional optical fiber and the variation of the core eccentricity are both ± 2 μm, and the variation of the outer diameter of the conventional optical fiber and the core eccentricity of the variation of ± 1 μm and ± 0.5 μm, respectively, Groove 9a,
Even if both 9b are fixed (no core alignment), the center axes of the optical fibers are matched by the self-alignment effect (absorption of outer diameter error), and the eccentric directions of the cores are aligned (core axis misalignment). By setting the amount to the minimum), an extremely large connection loss (maximum axial deviation loss of about 1.2 dB / axial deviation of 2.5)
(Micron) generation is suppressed (minimum axial misalignment loss of about 0.
43 dB / axis deviation of 1.5 micron), (1.2-0.4
3 = 0.77 dB because the axial displacement loss can be reduced.)
There is an effect that a practical connection loss can be obtained.

Compared with the conventional core detection axis aligning method for a direct-view type optical fiber connecting device, conventionally, bidirectional core axis alignment was performed based on the true core position. On the other hand, according to the present invention, if one of the V grooves 9a and 9b is finely moved based on the apparent core position, unidirectional core axis alignment becomes possible. That is, according to the present invention, as is the case with the conventional method, the observation surface of the objective lens is set to a predetermined position of the optical fiber with high precision by the microscope fine movement mechanism at each time of detecting the core position with high accuracy. The core position can be detected with high accuracy, and the true amount of axial deviation (2
There is no need to calculate the relative distance between two cores or to perform core axis alignment with the bidirectional V-groove fine movement mechanism. As a result, the device can be simplified.

Further, according to the present invention, the core position detection error and the axis alignment error are small because the adjacent cores are simultaneously observed only once under the same observation condition and the unidirectional core axes are aligned. As a result, it is possible to perform more accurate axis alignment than in the past.

Further, in the conventional method, in actuality, core detection and axis alignment are extremely difficult unless an automatic device is used.
According to the present invention, for example, a V-groove is attached to an elastic cantilever while viewing a core image on an LCD, and a fine movement mechanism for sending the V-groove with an accuracy of 0.1 μm or less by a piezoelectric actuator is introduced. If it is possible to move, the axis can be adjusted manually. Further, also in the case of the present invention, if the observation surface of the objective lens is set at a predetermined position of the optical fiber, the true axial deviation amount can be calculated based on the lens effect of the optical fiber, and thus the true axial deviation amount is used. As with the conventional method, the core axis deviation loss before and after connection can be estimated.

By the way, the mode field diameter of an ordinary single-mode optical fiber is about 9.5 μm, and unless there is a request for a low-loss connection, the one-way V-groove fine movement mechanism does not require core alignment for practical use. Connection loss results are obtained. On the other hand, since the mode field diameter of the dispersion-shifted optical fiber is as small as about 8 μm, if a one-way fine movement mechanism is added to perform core axis alignment, a loss result with even lower loss can be obtained.

Instead of the core image one-way observing device 14, an ordinary microscope may be used to observe the core. Further, in the case of an optical fiber in which Ge is doped in the core, the core image can be observed as a temperature radiation image or a luminescence image by ultraviolet light excitation, and the two dark lines 7-
1, 7-2 can be used instead.

[Second Embodiment] FIG. 4 shows a second embodiment of the present invention.
FIG. 4 is a diagram for explaining an optical connector manufacturing tool that is an embodiment example of, and forms a terminal by attaching a ferrule to an optical fiber. In the optical connector manufacturing tool of the present invention, the ferrule body 10-1 is provided immediately before the optical fiber 1-1 is inserted into the optical fiber insertion through hole 11 of the ferrule 10-1 and fixed with an adhesive.
After determining the direction in which the core of the optical fiber 10-1 is eccentric with respect to (the central axis of the optical fiber insertion through hole 11), the optical fiber 1-1 and the ferrule 10-1 are bonded and fixed to form a terminal. It is an optical connector manufacturing tool.

This device has a fixed V groove 9 for mounting an optical fiber.
a, an optical fiber rotation angle determining mechanism 13 for rotating the optical fiber 1-1 on the fixed V groove 9a, and fixing the rotation of the optical fiber at an arbitrary rotation position, and a core image of the optical fiber from one direction. Image of one-way observation device 14
The ferrule positioning table 15 is mainly included. Here, the upper surface of the ferrule positioning table 15 is made parallel to the observation surface of the microscope objective lens. Further, the distance between the fixed V groove 9a and the ferrule positioning base 15 is set to be equal to or longer than the optical fiber length sufficient to penetrate the optical fiber 1-1 through the optical fiber insertion through hole 11 of the ferrule 10-1.

The optical fiber rotation angle determining mechanism 1 is also provided.
3 and the ferrule positioning base 15 slide the optical fiber 1-1 on the V groove 9a in the x direction while maintaining the core eccentric direction of the optical fiber to insert the optical fiber 1-1 into the optical fiber insertion through hole. The optical fiber rotation angle determining mechanism 13 or the ferrule positioning base 1 so that it can be inserted into
5 is installed on the slide mechanism 17 (in this embodiment, the optical fiber rotation angle determining mechanism 13 is installed on the slide mechanism 17).

When a thermosetting adhesive such as epoxy is used as the ferrule adhesive, the heater 16 may be incorporated in the ferrule positioning base 15, or another heater may be prepared so that the ferrule can be heated. .

FIG. 5 is a view for explaining the direction in which the core of the optical fiber is eccentric with respect to the ferrule body. The optical fibers 1-1 and 1-2 are fixed to the ferrules 1-1 and 1-2, and the ferrules 1-1 and 1-2 are positioned by the ferrule fitting pin. If the eccentric direction of the core of the optical fiber 1-1 adhered and fixed to the ferrule 10-1 is the same in the y direction with respect to the butted ferrule, the situation of the optical fiber butted portion is as shown in FIG. As described above, the axial deviation between the cores of the optical fibers can be set to the minimum.

The optical connector manufacturing method is as follows.
Immediately before inserting the optical connector into the optical fiber insertion through hole of the ferrule and immediately before fixing with an adhesive or mechanically,
(1) "First procedure" for placing the optical fiber on the V groove,
(2) While rotating the optical fiber on the V groove, the core image of the optical fiber is observed from one side surface direction of the optical fiber, and the core image is divided into two by the central axis of the optical fiber. , A "second procedure" in which the rotation angle of the optical fiber is searched so that it is located on one side that is predetermined and the core image is farthest from the central axis of the optical fiber; "Third means" for fixing the fiber at the rotation angle, and (4) aligning the eccentric direction of the core of the optical fiber with the direction of the ferrule with respect to the axis of the optical fiber insertion through hole to make the optical fiber into a ferrule. It consists of the "fourth procedure" of fixing.

As described in the first embodiment, by determining the direction in which the core of the optical fiber is eccentric with respect to the ferrule body, it is possible to eliminate one of the factors causing axial misalignment in the connector connection. However, this is effective when using a single mode optical fiber having a core eccentricity amount of 1 μm or less, which is usually used, and a ferrule manufactured with high precision (submicron precision).

In the second embodiment, the case of connecting a connector such as a ferrule has been described.
It can also be applied to mechanical splices. For example, as a mechanical splice, there is a mechanical splice in which optical fibers are butted against one V groove and the optical fibers are fixedly connected to the V groove.

As described above, according to the axis aligning method and apparatus of the present invention, in the fusion splicing or connector connection of the optical fibers, the eccentric directions of the cores of the abutted optical fibers are the same. Therefore, when the center axes of the optical fibers are aligned, the amount of core axis misalignment between the abutted optical fibers can be set to a minimum (0.1 μm in FIG. 10), the abutment loss is also minimized, and at the same time the connection fails. Can be significantly reduced. Further, in the past, since it was necessary to observe the true core position, a two-way fine movement mechanism and an observation system with a two-way focus adjustment fine movement mechanism were indispensable for core alignment. By using the apparent core position by the observation system, the axial misalignment between cores can be set to the minimum.
Furthermore, if either one of the V-grooves is a unidirectionally movable V-groove fine movement mechanism, axial misalignment can be removed in principle, and as a result, low loss connection is possible.

In the present invention, the optical fiber core wire has about 1
A twist of rotation is added, but it is eliminated in the longitudinal direction of the optical fiber. Alternatively, this twist can be completely removed on the side of the drop core wire when one core wire is taken out of the optical cable and connected to a separately prepared drop core wire. Or this twist is
The extra length of the optical fiber is accommodated in the winding of the core wire when the extra length is accommodated in a bag or the like. As described above, the twisting of the optical fiber core wire for about one rotation accompanying the core axis alignment due to the rotation of the optical fiber is not a practical problem.

The eccentricity of the optical fiber to be connected is
It is known in many cases, but if optical fibers with similar eccentricity are connected, the core axis deviation amount becomes zero in principle without using the one-way movable V-groove fine movement mechanism, and even lower loss connection is possible. Becomes

Further, in the above description, the case of the single-core connection has been described, but if the single-core connection is repeated a plurality of times, it can be applied to the multi-core connection.

[0057]

As described above, according to the method and apparatus for aligning the cores of the optical fiber, only one-way observation or the one-way V-groove moving mechanism is used for the core connection of the optical fiber during fusion splicing or connector connection. The axial misalignment between them can be minimized, or the axial misalignment can be removed, and as a result, low-loss connection can be achieved, and therefore connection failure due to core axial misalignment loss can be extremely reduced. Therefore, the connection work cost can also be reduced. Further, since there is no need for the observation device with the bidirectional fine movement mechanism for the core image or the fine movement mechanism for the bidirectional positioning of the core, there is an advantage that the connecting device can be made smaller, lighter and less expensive.

As an application field, if it is used for optical fiber connection of an optical subscriber line which will be developed in the future, a connection device excellent in portability and workability can be realized, and further, a low loss and low cost optical line can be realized. It is effective for realization.

[Brief description of drawings]

1 (a) and 1 (b) are views for explaining a first embodiment of the present invention, which is a view showing a state of an optical fiber butting portion displayed on an LCD.

FIG. 2 is a diagram for explaining the first embodiment of the present invention,
It is the figure which looked at the mode of movement of the core of the optical fiber butted part displayed on LCD from the optical fiber cross section (x) direction.

FIG. 3 is a diagram illustrating a core axis aligning device for an optical fiber, which is one of the devices for realizing the first embodiment of the present invention.

FIG. 4 is a diagram for explaining an optical connector manufacturing tool that is a second embodiment of the present invention and is used to form a terminal by attaching a ferrule to an optical fiber.

FIG. 5 is a diagram for explaining a core eccentric direction of an optical fiber with respect to a ferrule.

FIG. 6 is a diagram illustrating a method of aligning a conventional core direct-view type optical fiber connecting device.

FIG. 7 is a diagram illustrating a conventional method for observing a core.

FIG. 8 is a diagram for explaining an axial alignment portion of a simple optical fiber fusion splicing device using conventional fixed V-groove axial alignment.

FIG. 9 is a diagram illustrating a conventional connector connection for forming and connecting an optical fiber with a ferrule.

FIG. 10 is a diagram showing an example in which a probability density function of axial misalignment between cores is calculated when optical fibers are randomly abutted against each other.

[Explanation of symbols]

 1,1-1,1-2 optical fiber 1-1-0,1-2-0 coating part of optical fiber 2 parallel light 3 objective lens 4 observation surface of objective lens 5 core 6 transmitted light 7,7-1, 7-2 Core image (dark line) 8 Microscope with fine movement mechanism for focus adjustment 9a, 9b V groove 90 V groove clamp 10 Ferrule 11 Optical fiber insertion through hole 12 Ferrule fitting pin hole 13 Optical fiber rotation angle determining mechanism 14 Core image 1 Direction observation device 15 Ferrule positioning table 16 Heater 17 Slide mechanism

Claims (7)

[Claims] 1. A method of connecting optical fibers on a fixed V-groove, comprising a first step of abutting end faces of two optical fibers to be connected on the V-groove, and rotating each optical fiber on the V-groove. Observing a core image of the optical fiber from one side surface direction of the optical fiber, and each of the observed core images is on one side of an observation field of view divided into two by the central axis of the optical fiber, and Search for the rotation angle of each optical fiber so that the core image is farthest from the center axis of the optical fiber.
And the third step of fixing each optical fiber at the rotation angle, the method of aligning the core axes of the optical fibers. 2. A device for connecting an optical fiber on a fixed V groove, wherein a fixed V groove for abutting end faces of two optical fibers to be connected and an optical fiber abutted on the fixed V groove are rotated, An optical fiber alignment device comprising: an optical fiber rotation angle determining mechanism for fixing the optical fiber; and a core image unidirectional observation device for observing the core image of the optical fiber from one side surface. 3. A method for connecting an optical fiber on a V groove, comprising a first step of abutting the end faces of two optical fibers to be connected on the V groove, and rotating each optical fiber on the V groove. The core image of the optical fiber is observed from one side of the optical fiber, and each of the observed core images is on one side of the observation field of view divided into two by the central axis of the optical fiber, and each of the core images is To find the rotation angle of each optical fiber so that is farthest from the center axis of the optical fiber.
And a third procedure of fixing each optical fiber at the rotation angle, and at least one V groove is orthogonal to a plane formed by the optical axis of the objective lens used for the observation and the optical fiber central axis. And a fourth step of axially aligning the cores of the optical fibers to be connected with each other. 4. An apparatus for connecting optical fibers on a V-groove, wherein the end faces of two optical fibers to be connected are butted and at least one is perpendicular to a plane formed by the optical fiber observation direction and the optical fiber central axis. A V-groove configured to move in any direction, an optical fiber rotation angle determining mechanism configured to rotate the optical fiber abutted on the V-groove and fix the rotation, and the optical fiber from one side surface. A core image unidirectional observation device for observing the core image of the optical fiber alignment device. 5. A method of forming an end portion of an optical fiber with a ferrule and connecting ferrules to each other to connect a connector, wherein the optical fiber is inserted into an optical fiber insertion through hole of the ferrule, and an adhesive is used or mechanically. Immediately before fixing, the first procedure of placing the optical fiber on the V groove, and observing the core image of the optical fiber from one side surface direction of the optical fiber while rotating the optical fiber on the V groove, So as to be located on one side that is predetermined in the observation field of view divided into two by the central axis of the optical fiber, and so that the core image is farthest from the central axis of the optical fiber,
The second procedure for finding the rotation angle of the optical fiber, the third procedure for fixing the optical fiber at the rotation angle, and the core eccentric direction of the optical fiber to be connected are the same at the ferrule joint surface when the connector is connected. A method for producing an optical connector, which comprises a fourth step of fixing an optical fiber to a ferrule so as to be oriented. 6. An optical connector manufacturing tool for forming an end portion of an optical fiber with a ferrule, a fixed V groove for mounting the optical fiber, rotating the optical fiber on the fixed V groove, and fixing the rotation of the optical fiber. Optical fiber rotation angle determining mechanism, a core image unidirectional observing device for observing a core image of the optical fiber from one side surface direction of the optical fiber, and a eccentric direction of the core of the optical fiber to be connected when the ferrule is joined at the time of connector connection. And a slide mechanism for inserting the optical fiber into the optical fiber insertion through hole of the ferrule while maintaining the core eccentric direction of the optical fiber. Optical connector manufacturing equipment. 7. A method of connecting an optical fiber by mounting it on a V-groove, wherein after the optical fiber is connected, a true core axis deviation amount is calculated based on the position of the observation surface of the core image one-way observation device with respect to the optical fiber. The optical fiber axis alignment method according to claim 1 or 3, further comprising a step of estimating a core axis misalignment loss.