JP3273489B2 - Core alignment method for optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to optical fiber with low loss core shaft connected to the combined method and lightweight simple core axis alignment apparatus and an optical connector fabricated how.

[0002]

2. Description of the Related Art As is well known, if the core axes of butted optical fibers are misaligned, the connection loss increases. In order to connect an optical fiber with low loss, it is necessary to minimize the axial misalignment between cores of the optical fiber to be connected.

(1) FIG. 6 is a view for explaining a method of aligning a conventional core direct-view type optical fiber connection device (Japanese Patent Application Laid-Open No. 60-1985).
-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 placed at the rear (range OB) of the core 5 in 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 a direction perpendicular to the paper surface).

The apparent position of the core with respect to the central axis of the optical fiber is caused by the lens effect of the optical fiber. Observed at magnification,
In the center of the optical fiber, the observation magnification is increased to an observation magnification of about 1.5, and when the position of the observation surface is brought closer to the microscope objective lens 3, the observation magnification is reduced to 1 or less. Is done. With respect to the apparent core position, the true core position described below is the actual core position and is not affected by the lens effect of the optical fiber. 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 butted optical fibers 1-1 and 1-2 are observed from two directions of y and z, and the positions of the core images of the optical fibers are detected. This operation needs to be performed on the two butted optical fibers 1-1 and 1-2. At this time, since the optical fiber has a lens effect, each time a core image is detected, the observation surface of the objective lens is moved to a predetermined position of the optical fiber by the microscope 8 with a fine adjustment mechanism for focusing.
Must be set to high precision. 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 from two systems to one system. Next, based on the true core position, the microcomputer calculates the axis shift amount between the cores. Finally, in two directions y and z, at least one of the optical fibers 1-1 and 1-2 is moved by the two-direction V-groove fine movement mechanism to perform core alignment, and the optical fiber is connected with low loss.

(2) FIG. 8 is a view for explaining a shaft aligning portion of a conventional simple optical fiber fusion splicing apparatus using a fixed V-groove shaft alignment. As shown in FIG. 8, the optical fibers 1-1, 1
-2, butted on the alignment table 9 having the fixed V-groove 9a, and simply aligned on the basis of the outer diameter of the optical fiber clad,
The optical fibers 1-1 and 1-2 are connected.
Even if there is a difference in outer diameter between the optical fibers 1-1 and 1-2, or even if the center axes of the optical fibers are misaligned before connection, the optical fiber butted portion is kept for a relatively long time (around 10 seconds). When the fusion splicing is performed by heating, surface tension acts on the fused silica glass at the end of the optical fiber, and the self-centering effect between the butted optical fibers causes the optical fibers 1-1 and 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 bonding an optical fiber to the optical fiber insertion through-hole 11 of the ferrules 10-1 and 10-2 through an optical fiber and fixing the ferrule fitting pin hole 12.
Insert a fitting pin (not shown) into the ferrules 1
By joining 0-1 and 10-2, the optical fibers 1-1 and 1-2 are positioned and connected as a result.

[0008]

[Problems to be solved by the invention]

(1) However, in the case of the optical fiber connection device of the core direct view type shown in FIG. 6, a microscope with a fine adjustment mechanism for focus adjustment for observing a core image from two directions, a core axis shift calculator, and a two-way V-groove fine movement mechanism are indispensable. , Detection time and axis alignment time are both long,
Multiple fine movement mechanisms and their highly rigid support members have become larger,
Therefore, the weight increases, and the price increases according to the core detection and the precision of the fine movement mechanism.

Furthermore, in recent years, with the improvement in optical fiber manufacturing technology, the magnitude of the core eccentricity and the variation in the cladding outer diameter have become smaller. Therefore, as the optical fiber manufacturing error becomes smaller and the variation in the parameters of the optical fiber structure becomes smaller, errors in 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 shift are reduced to zero. In order to sufficiently reduce the core position detection and positioning error caused by the fine movement positioning mechanism, the conventional equipment requires a core detection system and a positioning fine movement mechanism with higher accuracy, resulting in an increase in the size of the connection device. In addition, the weight and the price are increased, which is not practical.

(2) In the case of the simple optical fiber fusion splicer shown in FIG. 8, the center axes of the optical fibers are aligned by the self-centering effect between the optical fibers. However, the direction of eccentricity of the core axis with respect to the optical fiber center axis (hereinafter, referred to as
(Expressed as the core eccentric direction) is random. Simply, when an optical fiber is abutted on a fixed V-groove, the core eccentricity causes a core axis misalignment, and the connection loss corresponds to the axis misalignment amount generated at that time. Becomes larger. The maximum deviation amount of the core axes of the butted optical fibers is the sum of the core eccentricity amounts of the respective optical fibers. A large connection loss occurs in the vicinity of the optical fiber butting position where the maximum core axis shift occurs.

For example, the core of a normal single mode optical fiber is allowed to have an eccentricity of at most 1 μm. Now, when optical fibers having a core eccentricity of 1 μm and a core eccentricity of 0.9 μm are randomly abutted with the center axes of the optical fibers coincident with each other, a probability density function for the axial misalignment between the cores is calculated as shown in FIG. As shown. FIG.
The worst case is that an axis shift of 1.9 μm occurs, and this axis shift is converted to a loss of about 0.8 dB. Normally, another loss error factor such as an optical fiber cutting angle is added, and the connection loss further increases. The risk of starting over is greater.
For example, in the case of fusion splicing, if it exceeds 0.5 to 0.6 dB, reconnection may occur as a connection failure. Failure to do so will increase connection time. 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 IEICE Technical Report CS95-49, OCS95-15 (1995-06) p.56 “Design and characteristics of an optical cable with an ultra-high-density double-ended connector”, see FIG. Then, at present, the axis deviation error caused by the gap of the optical fiber insertion through-hole 11 is 0.
The axis 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. In comparison, the current allowable value of the core eccentricity of the optical fiber is 1 μm.
m (at this time, the maximum axis deviation error is 2 μm). As described above, the factor of the manufacturing error of the connector that causes the axial misalignment and the core eccentricity of the optical fiber are at the same level. As a result, when the optical fibers are abutted, 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, as described in the above (2), when the optical fibers are abutted, the core axis misalignment loss due to the core eccentricity of the optical fibers has become a problem. .

However, this core axis misalignment loss has been regarded as an inevitable loss. For this reason, after forming and finishing the optical fiber with a ferrule, it is connected to a reference connector or the like to evaluate 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 marginal 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 (slightly large), the connection is often reconnected as a connection failure. If you fail, the connection time will be longer. Conventionally, it has been desired to reduce the frequency of such reconnection to improve connection efficiency.

[0014]

In order to solve the above-mentioned problems, a first method of aligning the core of an optical fiber according to the present invention is a method of connecting optical fibers on a fixed V-groove. A first procedure of abutting the end faces on the V-groove, and while rotating each optical fiber on the V-groove,
Observing a core image of the optical fiber from one side direction of the optical fiber, each observed core image is on one side of an 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 central axis of the optical fiber, and a third procedure for fixing each optical fiber at the rotation angle. It is characterized by the following.

[0015]

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

[0017]

In the first or second optical fiber axis alignment method, in the method of connecting an optical fiber by placing it on a V-groove, the optical fiber may be connected to an optical fiber at a position of an observation surface of the one-way core image observation apparatus with respect to the optical fiber. Based on this, a procedure for calculating a true core axis deviation amount and estimating a core axis deviation loss is added.

In the method of manufacturing an optical connector according to the present invention, in the method of forming an end portion of an optical fiber with a ferrule and connecting the ferrule with the ferrule, the optical fiber is inserted into an optical fiber insertion through hole of the ferrule. A first procedure of placing the optical fiber on the V-groove just before fixing it with an adhesive or mechanically,
While rotating on the groove, a core image of the optical fiber is observed from one side direction of the optical fiber, and the core image is located on one predetermined side of an observation field of view divided into two by the central axis of the optical fiber. A second procedure for finding the rotation angle of the optical fiber so as to be positioned and the core image being farthest from the central axis of the optical fiber; and a third procedure for fixing the optical fiber at the rotation angle. And a fourth step of fixing the optical fiber to the ferrule such that the core eccentric direction of the optical fiber to be connected is the same direction at the ferrule joint surface when the connector is connected. .

[0020]

[Operation] The direction in which the core is decentered is the same for the two optical fibers butted together. Therefore, when the optical fibers are butted or connected by aligning the center axes of the optical fibers, the displacement between the core axes of the butted optical fibers is minimized. At this time, the butting loss of the optical fiber is also minimized.

Further, since the directions in which the two cores are eccentric are the same, and the two cores are butted in the same plane, accurate core alignment can be achieved only by one-way alignment. In this case, irrespective of the lens effect of the optical fiber, accurate core axis alignment can be performed using an apparent core image obtained by only one core image simultaneous observation.

[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 show a first embodiment of the present invention and are views for explaining a method of aligning a core of an optical fiber.

FIGS. 1A and 1B are views showing the state of an optical fiber butting portion displayed on an LCD (liquid crystal display screen). FIG. 2 shows the state of movement of the core with respect to the optical fiber center axis of the optical fiber butting portion displayed on the LCD, as seen from the direction of the optical fiber cross section (x), 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 portions, and the width of the dark portions is determined by the numerical aperture of the objective lens (the limit of the angle of light rays that can be received) and the position of the observation surface. As described with reference to FIG. 7 in the “Prior Art” section, in FIG. 2, when the optical fibers 1-1 and 1-2 are observed from the z direction when the core is eccentric, the core is fixed. When the optical fibers 1-1 and 1-2 on the V-grooves 9a and 9b are rotated, the two dark lines 7-1 and 7-2, which are core images, move closer to or away from the optical fiber central axis. Now, the core images 7-1 and 7-2 correspond to the optical fibers 1-1 and 1-2.
Are located on one side of the observation field of view divided into two by the central axis of the optical fiber, and each of the optical fibers 1-1 and 1- is arranged so that each core image is furthest from the central axis of the optical fiber.
By searching for the rotation angle of 2 and fixing each optical fiber to the rotation angle, the amount of axial misalignment between the cores of the butted optical fibers can be set to the minimum (see FIG. 2B).

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

On the other hand, in FIG. 2B, of the V-grooves 9a and 9b carrying the optical fiber, one of the V-grooves 9a and 9b carrying the optical fiber is moved in the y direction.
If the groove fine movement mechanism is used, one of the optical fibers can be moved in the y direction to make the axes of the core images 7-1 and 7-2 coincide (see FIG. 2C). When the optical fibers 1-1 and 1-2 are rotated on the V-grooves, the rotation directions of the optical fibers 1-1 and 1-2 are selected so that the twist generated in the connected optical fibers is minimized. Good to connect.

Here, when the V-groove 9a and the V-groove 9b are fixed, the procedure for setting the amount of axial misalignment between the cores to the minimum is as follows. (1) "First procedure" in which end faces of two optical fibers 1-1 and 1-2 to be connected are butted on V-grooves 9a and 9b.
(2) Each optical fiber 1-1, 1-2 is connected to the V-groove 9
While rotating on the optical fibers 9a and 9b, the core images of both optical fibers are observed from one side direction of the optical fiber, and each observed core image is divided into two parts by the central axis of the optical fiber. A "second procedure" for finding the rotation angle of each optical fiber so that it is on one side and each core image is farthest from the central axis of the optical fiber; The “third procedure” for fixing the fiber is included. (4) Further, in the first, second, and third procedures described above, at least one V groove is oriented in a direction orthogonal to a plane formed by the optical axis of the objective lens used for the observation and the central axis of the optical fiber. In addition, by adding the "fourth procedure" for aligning the cores of the optical fibers to be connected, the core alignment can be performed more accurately.

FIG. 3 is a view for explaining an optical fiber core axis aligning apparatus, which is one of the apparatuses for realizing the first embodiment of the present invention. As shown in FIG. 3, the optical fiber connection device of the present invention includes V grooves 9a and 9b where the optical fibers 1-1 and 1-2 abut, and the optical fibers 1-1 and 1-2 which abut each other. An optical fiber rotation angle determining mechanism 13 that rotates on the V-grooves 9a and 9b and fixes the rotation of the optical fibers 1-1 and 1-2 at an arbitrary rotation position; -2 core image 7-1,
And a core image one-way observation device 14 for observing 7-2. In addition to the above configuration, optical fibers 1-1,
A fusion splicing apparatus is configured by adding a butt heating section 1-2 (arc discharge or glow discharge heating, gas heating, laser heating apparatus) and a control mechanism for moving the optical fiber in the axial direction and butt. .

Here, the optical fiber rotation angle determining mechanism 13
Are an optical fiber gripper 13-1 having a cylindrical outer periphery, a sliding cylinder 13-2 of the optical fiber gripper, and a rotation fixing component 13 of the optical fiber gripper 13-1 provided on the sliding cylinder 13-2. -3
It is composed of Here, the optical fiber gripper 13-1
Is configured to be able to make at least one rotation. Further, the optical fiber holding portion 13-1 and the sliding cylinder 13-2 are configured to be split into two at a plane including the optical fiber axis. Optical fiber 1
-1 and 1-2 with a slight bending force so that the optical fiber rotates with the rotation axis of the optical fiber rotation angle determining mechanism 13 so that the optical fiber always rotates while being in contact with the fixed V-groove about the optical fiber center axis as the rotation axis. The optical fibers 1-1 and 1 mounted on the grooves 9a and 9b, respectively.
The center axis of 1-2 is at a small angle. A V-groove clamp 90 is attached to the optical fiber so that the optical fiber rotates while securely contacting the V-groove.
A configuration in which the groove is slightly pressed may be used.

By the way, as shown in FIG.
9b and the V-groove clamp 90, and if the covering portions 1-1-0 and 1-2-0 of the optical fibers 1-1 and 1-2 are turned directly by hand, the rotation angle of the optical fiber is functionally increased. It has the same function as the deciding 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 one-way observation device 14 includes a parallel light source 14-1, a microscope 14-2, a CCD imaging device 14-3, a signal drive control board 14-4, and an LCD (liquid crystal display screen). 14-5.

In FIG. 3, the optical fiber butting portion is irradiated with parallel light from a parallel light source 14-1, and the observation surface of the objective lens of the microscope 14-2 is viewed from the core as viewed from the CCD imaging device 14-3 side. When the transmitted light is set in front (“set range OB” shown in FIG. 7) and the transmitted light is observed by the one-way core image 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
b, the observation surface of the objective lens is set at the same position with respect to the optical fibers 1-1 and 1-2, and the sizes of the two core images (the distance between the 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 observed at the same observation magnification. For this reason, regardless of the position of the observation surface of the microscope objective lens with respect to the optical fiber, and thus using the apparent core image position,
Accurate core alignment can be performed.

Further, since the two core images are both on the same observation plane, the core alignment is performed by setting at least one of the V grooves 9a and 9b in one direction (y direction: the direction of the objective lens). This can be achieved by using a fine movement mechanism that is movable in a direction perpendicular to the plane formed by the optical axis and the optical fiber center axis (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 increases, and the apparent core position with respect to the optical fiber center axis is enlarged and observed. A more accurate alignment is possible by the amount.

Next, since the center axes of the optical fibers are shifted in the observation (Z) direction due to, for example, variations in the outer diameter of the optical fibers, the set position of the observation surface of the objective lens is shifted to the optical fiber 1-1 which has been abutted. , 1-2 are different. In FIG. 7, even if the center axes of the optical fibers butted on the V-groove are displaced 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 and 1--1. For 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 V-groove surface, 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. When the heat fusion time of the butted optical fibers is set to about 10 seconds, the central 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 butted optical fibers are displaced in the observation direction or the y direction before the connection, the cores are connected to each other by the self-centering effect after the connection (as shown in FIG. 2B). Closest.

However, when the core axis is accurately aligned using a one-way (y-direction) V-groove fine movement mechanism, the V-shape must be adjusted before connection.
It is necessary to remove dust on the groove surface and to 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 the outer diameter and the amount of core eccentricity. Consider a case in which 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 in the outer diameter and the amount of core eccentricity of the conventional optical fiber are both ± 2 μm, and the variation in the outer diameter and the amount of core eccentricity of the recent optical fiber are ± 1 μm and ± 0.5 μm, respectively, V Groove 9a,
Even if both cores 9b are fixed (without core alignment), the center axes of the optical fibers coincide with each other due to the self-alignment effect (absorption of the outer diameter error), and the eccentric directions of the cores are aligned (core axis deviation). Extremely large connection loss (maximum axis deviation loss of about 1.2 dB / axis deviation of 2.5)
(Micron) is suppressed (minimum axis deviation loss of about 0.1 mm).
43 dB / axis misalignment 1.5 microns), (1.2-0.4
3 = 0.77 dB because the axis shift loss can be reduced.)
There is an effect that a practical connection loss can be obtained.

Compared with the conventional core detection axis alignment method of the core direct-view type optical fiber connection device, the two-way core axis alignment has been conventionally performed based on the true core position. On the other hand, in the present invention, if one of the V grooves 9a and 9b is slightly moved based on the apparent core position, the one-way core axis alignment can be performed. That is, the present invention sets the observation surface of the objective lens to a predetermined position of the optical fiber with high precision by the microscope fine-movement mechanism every time the core position is detected, as has been performed by the conventional method. The core position can be detected with high accuracy, or the true axis shift amount (2
There is no need to calculate the relative distance between the two cores) or to perform core axis alignment using the two-way V-groove fine movement mechanism. As a result, the device can be simplified.

Further, according to the present invention, the adjacent cores are simultaneously observed only once under the same observation conditions, and the core position detection error and the axis alignment error are reduced by the amount that only the unidirectional core axis alignment is required. As a result, it is possible to perform more accurate axis alignment than before.

Further, in the conventional method, the core detection and alignment are extremely difficult unless they rely on an automatic device.
The present invention provides a V-groove by attaching a V-groove to an elastic cantilever while introducing a fine movement mechanism for feeding the V-groove with an accuracy of 0.1 μm or less by a piezoelectric actuator while watching a core image on an LCD. Can be moved manually, it is possible to align the axes 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 shift amount can be calculated based on the lens effect of the optical fiber. Similarly to the conventional method, the core axis shift loss before and after the connection can be estimated.

The mode field diameter of a normal single-mode optical fiber is about 9.5 μm, and unless a low-loss connection is required, even if the core axis is not aligned by a one-way V-groove fine movement mechanism, it can be used practically. Connection loss results. On the other hand, the mode field diameter of the dispersion-shifted optical fiber is as small as about 8 μm. Therefore, if a one-way fine movement mechanism is added to perform core alignment, a loss result with lower loss can be obtained.

Note that the core may be observed using a normal microscope instead of the one-way core image observation device 14. In the case of an optical fiber in which the core is doped with Ge, the core image can also be observed as a temperature emission image or a luminescence image excited by ultraviolet light.
1, 7-2 can be used.

[Second Embodiment] FIG. 4 shows a second embodiment of the present invention.
FIG. 4 is a diagram illustrating an optical connector manufacturing tool for forming a terminal by attaching a ferrule to an optical fiber according to the embodiment. In the optical connector manufacturing tool of the present invention, just before inserting the optical fiber 1-1 into the optical fiber insertion through hole 11 of the ferrule 10-1 and fixing it with the adhesive, the ferrule main body 10-1 is used.
After determining the direction in which the core of the optical fiber 10-1 is eccentric with respect to (the center 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.

The present device has a fixed V-groove 9 on which an optical fiber is placed.
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. Core image one-way observation device 14 for observing
And a ferrule positioning table 15. Here, the upper surface of the ferrule positioning table 15 is set to be parallel to the observation surface of the microscope objective lens. The distance between the fixed V-groove 9a and the ferrule positioning table 15 is set to be longer than the length of the optical fiber enough to penetrate the optical fiber 1-1 into the optical fiber insertion through hole 11 of the ferrule 10-1.

Also, the optical fiber rotation angle determining mechanism 1
3 and the ferrule positioning table 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, and insert the optical fiber 1-1 into the optical fiber insertion through hole. 11 so that the optical fiber rotation angle determining mechanism 13 or the ferrule positioning table 1 can be inserted.
Numeral 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, a heater 16 may be incorporated in the ferrule positioning table 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 main body. The optical fibers 1-1 and 1-2 are fixed to ferrules 1-1 and 1-2, and the ferrules 1-1 and 1-2 are positioned by ferrule fitting pins. Regarding the butted ferrules, if the eccentric directions of the core of the optical fiber 1-1 bonded and fixed to the ferrule 10-1 coincide in the y direction, the situation of the optical fiber butted portion is as shown in FIG. As described above, the axis deviation between the cores of the optical fibers can be set to the minimum.

An optical connector manufacturing method is as follows.
Immediately before inserting the optical connector into the optical fiber insertion through hole of the ferrule and fixing it with an adhesive or mechanically,
(1) The “first procedure” for placing the optical fiber on the V-groove,
(2) While rotating the optical fiber on the V-groove, a core image of the optical fiber is observed from one side of the optical fiber, and the core image is divided into two parts by the central axis of the optical fiber. (2) searching for the rotation angle of the optical fiber so that the core image is located farthest from the central axis of the optical fiber so as to be located on one predetermined side, and (3) a "third means" for fixing the fiber at the rotation angle; and (4) aligning the direction of the core eccentricity of the optical fiber with the direction of the ferrule with respect to the axis of the optical fiber insertion through-hole to convert the optical fiber into a ferrule. It consists of a "fourth procedure" for 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 main body, one of the causes of the misalignment in the connector connection can be eliminated. However, this is effective when a commonly used single mode optical fiber having a core eccentricity of 1 μm or less and a ferrule manufactured with high accuracy (with submicron accuracy) are used.

In the second embodiment, the case of connector connection in a ferrule or the like has been described.
Also applicable to mechanical splices. For example, there is a mechanical splice in which optical fibers are butted on one V-groove and optical fibers are fixedly connected to the V-groove.

As described above, according to the shaft alignment method and apparatus of the present invention, in the fusion splicing or the connector connection of the optical fibers, the eccentric directions of the cores of the butted optical fibers are the same. For this reason, when the center axes of the optical fibers coincide with each other, the amount of deviation of the core axes of the butted optical fibers can be set to a minimum (0.1 μm in FIG. 10), the butting loss is also minimized, and connection failure occurs at the same time. Can also 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 axis alignment. The axis shift between cores can be set to a minimum using the apparent core position by the observation system.
Furthermore, if one of the V-grooves is a one-way movable V-groove fine movement mechanism, the axis deviation can be removed in principle, and as a result, low-loss connection can be achieved.

In the present invention, about 1 fiber
Rotational torsion is applied, but is eliminated in the longitudinal direction of the optical fiber. Alternatively, this torsion can be completely removed on the side of the drawn core when a single core is taken out of the optical cable and connected to a separately prepared core. Alternatively, this twist
The excess optical fiber length is absorbed in the winding of the core wire at the time of extra length processing for accommodating it in a bag or the like. As described above, twisting of the optical fiber core by about one rotation due to core axis alignment due to rotation of the optical fiber does not pose a practical problem.

The eccentricity of the optical fiber to be connected is
Although many cases are known, if optical fibers with similar eccentricity are connected to each other, the amount of core axis misalignment becomes zero in principle without using a one-way movable V-groove fine movement mechanism, enabling even lower loss connection. Becomes

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

[0057]

As described in the foregoing, according to the core axis combined Way Method of optical fiber, during fusion splicing or connector of an optical fiber, one way only observed or by a one-way V groove movable mechanism, cores Can be minimized or the axial misalignment can be eliminated, and as a result, low-loss connection is possible, and connection failure due to core axial misalignment loss is extremely reduced. Therefore, the connection work cost can be reduced. Further, since an observation device with a two-way fine movement mechanism for the core image or a two-way fine movement mechanism for the core is not required, there is an advantage that the connecting device can be reduced in size, weight and cost.

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

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams for explaining a first embodiment of the present invention, showing a state of an optical fiber butting portion displayed on an LCD.

FIG. 2 is a diagram illustrating a first embodiment of the present invention,
FIG. 5 is a diagram showing a state of movement of a core of an optical fiber butting portion displayed on an LCD, viewed from an optical fiber cross-section (x) direction.

FIG. 3 is a view for explaining an optical fiber core alignment device, which is one of the devices for realizing the first embodiment of the present invention.

FIG. 4 is a view for explaining an optical connector manufacturing tool according to a second embodiment of the present invention, which forms a terminal by attaching a ferrule to an optical fiber.

FIG. 5 is a diagram illustrating the direction of eccentricity of the core of the optical fiber with respect to the ferrule.

FIG. 6 is a view for explaining a method of aligning a conventional core direct-view type optical fiber connection device.

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

FIG. 8 is a view for explaining a shaft aligning portion of a conventional simple optical fiber fusion splicer using fixed V-groove shaft alignment.

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

FIG. 10 is a diagram illustrating an example of calculating a probability density function of axis shift between cores when optical fibers are randomly butted.

[Explanation of symbols]

 1, 1-1, 1-2 Optical fiber 1-1-0, 1-2-0 Coated portion 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 Direction observation device 15 Ferrule positioning table 16 Heater 17 Slide mechanism

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 6/255 G02B 6/38

Claims (4)

(57) [Claims] 1. A method for 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 direction of the optical fiber, each observed core image is on one side of an observation field of view divided into two by the central axis of the optical fiber, and The second step is to find the rotation angle of each optical fiber so that the core image is farthest from the central axis of the optical fiber.
And a third step of fixing each optical fiber at the rotation angle. 2. A method for connecting optical fibers on a V-groove, comprising: a first step of abutting end faces of two optical fibers to be connected on the V-groove; and rotating the respective optical fibers on the V-groove. A core image of the optical fiber is observed from one side direction of the optical fiber, and each observed core image is on one side of an observation field of view divided into two by the central axis of the optical fiber, and each core image is observed. Search for the rotation angle of each optical fiber so that is farthest from the central axis of the optical fiber.
A third procedure of fixing each optical fiber at the rotation angle; and at least one V-groove is perpendicular to a plane formed by the optical axis of the objective lens used for the observation and the central axis of the optical fiber. And a fourth step of moving the cores of the optical fibers to be connected to each other by moving the cores in the direction in which the optical fibers are to be connected. 3. A method of forming an end of an optical fiber with a ferrule, connecting the ferrules to each other with a connector, and inserting the optical fiber into an optical fiber insertion through hole of the ferrule using an adhesive or mechanically. Immediately before fixing, a first procedure of placing the optical fiber on the V-groove, and observing a core image of the optical fiber from one side direction of the optical fiber while rotating the optical fiber on the V-groove; Of the observation field of view divided into two by the central axis of the optical fiber, so as to be located on one predetermined side, and such that the core image is farthest from the central axis of the optical fiber,
A second procedure for finding the rotation angle of the optical fiber, a third procedure for fixing the optical fiber at the rotation angle, and the core eccentric direction of the optical fiber to be connected is the same at the ferrule joint surface when the connector is connected. And a fourth step of fixing the optical fiber to the ferrule so that the optical fiber is oriented in the direction. 4. A method of connecting an optical fiber by placing the optical fiber on a V-groove, wherein after connecting the optical fiber, a true core axis shift amount is calculated based on a position of an observation surface of the one-way core image observation apparatus with respect to the optical fiber. 3. An optical fiber alignment method according to claim 1, further comprising a step of estimating a core axis shift loss.