JPH073493B2 - Method of fusion splicing of constant polarization optical fiber - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fusion splicing method for a constant polarization optical fiber, and more particularly to a method for aligning an optical fiber before fusion. .

[Prior Art and Its Problems] In the case of a normal single optical fiber connection, the tip of the optical fiber may be moved in the x and y directions to perform alignment, but in the case of a constant polarization optical fiber, Further rotation is required.

The following is a more detailed explanation of this. The polarization maintaining optical fiber illustrated in FIG. 7 is a so-called panda type, where 12 is the whole optical fiber, 14 is a core, 16 is a clad, and 18 is a stress applying part.

When connecting such a polarization-maintaining optical fiber, generally, the birefringent principal axes are made to coincide with each other as shown in FIG.
Alternatively, the birefringent principal axes are made orthogonal to each other as shown in FIG.
In either case, there must be no deviation from the desired angle (0 or 90 degrees) between the birefringent principal axes.

In either case, before fusion, the optical fiber 12 is moved in the x and y directions to align the core 14 and at the same time
It is necessary to rotate 12 around the z-axis (hereinafter referred to as the θ direction) with high accuracy to set the positional relationship of the stress applying portion 18 as described above.

[Means for Solving Problems] As described above, in both cases where the birefringence principal axes of the polarization-maintaining optical fibers to be connected are matched or orthogonal to each other, both optical fibers are butted and one of the optical fibers is butted. When the extinction ratio is measured at the exit end of the other optical fiber by sending a linearly polarized light from the fiber, the absolute value of the extinction ratio becomes maximum when the birefringence principal axes of both optical fibers are completely coincident or exactly orthogonal to each other. (It is assumed that the core has been aligned).

The present invention utilizes the relationship between the shift of the birefringent main axis and the extinction ratio to enable accurate alignment, particularly in the θ direction of the polarization-maintaining optical fiber.

[Embodiment] In FIGS. 1 and 2, 20 is a V-groove block on which the optical fiber 12 is placed and is held by a fiber clamp 22 (not shown in FIG. 1).

24 is a support block on which the coated portion 10 of the optical fiber is provided.
And press it with a sheath clamp 26 (not shown in FIG. 1). The block 24 can be swung around the pin 28 in the direction of the arrow 30.

By turning the dial 32 by hand and rotating the swash plate cam 34,
The block 24 swings via the spindle 36, and the optical fiber 12 moves forward and backward in the z direction accordingly.

Reference numeral 38 is an electrode, 39 is an abutting rod, and mirrors 41 are provided on both surfaces of the apex orthogonal to each other so that the end face of the optical fiber can be observed. The above-mentioned parts are almost the same as those conventionally known.

Reference numeral 40 denotes a bracket, and an upper portion 42 thereof is slightly tilted forward to hold arms 52 and 54 (see later) in a tilted state.

44A is the whole rotation mechanism on the right side (referring to the drawing),
This is for giving rotation to the optical fiber in the θ direction.

A forwardly tilted upper portion 42 of the bracket 40 rotatably supports a cylindrical portion 46 of its base. The cylindrical portion 46 can be manually rotated by an integral dial 48.

As shown in FIG. 3, the groove 50 is formed in the cylindrical portion 46 and the dial 48.
To provide. The lower ends of the grooves 50 reach the respective central axes. Further, a groove 43 is also provided in the bracket 40. These grooves 43,5
When the optical fiber is dropped into 0, the optical fiber is positioned at the center of the cylindrical portion 46 and the like, and even if they are rotated, the optical fiber is not twisted.

From the cylindrical portion 46, the fixed arm 52 and the movable arm 54 project forward and slightly downward. Fixed arm 52 has a cylindrical section 46
The movable arm 54 is supported at its rear end by a pin 56 and can be opened and closed by the action of a spring 58 and a cam 60.

The fixed part 62 of the rotary clamp 61 is attached to the tip of the fixed arm 52.
Further, the movable part 64 of the rotary clamp 61 is attached to the tip of the movable arm 54.
Are provided respectively. These are semi-cylindrical, as shown in FIG. 4, and when joined together form a cylinder. Fixed part
A V groove 66 is provided in 62.

A fiber guide 68 is provided in front of the rotary clamp 61. This is fixed only to the fixed arm 52. Fiber optic on this
10 is mounted, the cam 60 is rotated to align the movable portion 64 with the fixed portion 62, and the rotary clamp 61 is closed, the optical fiber 10 is V-shaped.
Enter 66 and hold in the center. When the dial 48 is rotated in this state, the entire rotation mechanism 44A rotates about the central axis of the optical fiber.

The rotation mechanism 44B is also provided on the left side.

This is almost the same structure as the one on the right, but only the differences are as follows.

Gear 70 is provided instead of dial 48. Then, it is rotated by a motor 72 (with a reducer) through a train of gears 74, 76, 78. The gears 76 and 78 are integrated,
It is free to rotate with respect to the shaft 33.

To eliminate the backlash of the gear 70, a constant tension spring 82 pulls it through a wire 80. That is, in order to automatically obtain the optimum angle, it is necessary to reduce the backlash of the gear in forward rotation and reverse rotation, but the backlash is zero due to the function of the constant tension spring, and the angle adjustment is ± 0.5.
And the angle with extremely high accuracy can be obtained.

In order to determine the origin of rotation of the motor 72, a sensor plate 84 is attached to the gear 74 as shown in FIG. This is, for example, a fan-shaped plate with α of 45 °. As the gear 74 rotates, it swings to the left (clockwise) and to the right (counterclockwise), but in the state shown in FIG. 5, when the light beam of the optical sensor 86 is blocked and it moves slightly to the right, It is designed to let light pass through.

This time is the origin, and the groove 71 provided in the gear 70 or the cylindrical portion 46 faces directly upward so that the optical fiber inserted therein can be taken out (the groove 71 faces sideways). , And the optical fiber cannot be taken out because it is inconsistent with the groove provided in the bracket 40).

Therefore, for example, when the sensor plate 84 is swung to the right and is returned, when the sensor plate 84 is rotated to the left and stopped when the light receiver of the optical sensor 86 is turned off, Stop at the origin.

Also, when the sensor plate 84 is swinging to the left, the light from the optical sensor 86 is blocked, so turn it to the right to
It should stop at the moment it is turned on.

A gear train such as the rotation mechanism 44B, the motor 72, and the gear 74 is mounted on the frame 88 of the z-axis drive mechanism and is movable in the z-axis direction.

FIG. 2 briefly shows an extinction ratio measuring system. 90 is a light source,
Reference numeral 92 is a polarizer, 94 is an analyzer, 96 is a photodetector, and 98 is an optical power meter. A control device 99 calculates the extinction ratio based on the output of the power meter 98, and controls the rotation of the motor 72 so as to maximize the extinction ratio.

[Operation] The optical fiber is set on the rotating mechanisms 44A, B and the blocks 24, 20 and pressed by the fiber clamp 22 and the sheath 26 as in the conventional case, and the cam 60 is rotated and pressed by the rotating clamp 61.

As shown in FIG. 6, while looking at the image of the end face of the optical fiber 12 with the microscope 90 by the mirror 41 provided at the tip of the abutting rod 39, the dial 48 of the rotation mechanism 44A on the right side is turned to apply stress. Coarse adjustment is manually performed so that the positions of the parts 18 are symmetrical (or orthogonal).

Next, the x- and y-directions are automatically adjusted in the same manner as in the prior art, and then the left-hand rotation mechanism 44B is used to perform the θ-direction automatic adjustment as follows.

For this, the extinction ratio is used as described at the beginning.

As described above, the absolute value of the extinction ratio is maximized when the birefringent principal axes of both optical fibers are completely coincident or exactly orthogonal to each other.

Therefore, linear polarized light is sent from one (right) optical fiber through the light source 91 and the polarizer 92, and the analyzer 94, the photodetector 96, the optical power meter 98, at the emission end of the other optical fiber.
The extinction ratio is detected via the control device 99, and thereby the rotation angle of the motor 72 is feedback-controlled to rotate the rotating mechanism 44B so that the absolute value of the extinction ratio becomes maximum.

As described above, the absolute value of the extinction ratio is maximized when the birefringent principal axes are either coincident or orthogonal, but the birefringent principal axes are substantially coincident or orthogonal to each other by rough adjustment in advance. Therefore, there is no error such as feedback control so that the birefringent principal axes are made to coincide with each other, but are made orthogonal to each other.

[Advantages of the Invention] (1) Utilizes the phenomenon that the absolute value of the extinction ratio becomes maximum when the birefringence principal axes of both optical fibers to be connected are completely coincident or exactly orthogonal to each other, The relationship between the angle deviation of the birefringent principal axes of both optical fibers to be connected and the extinction ratio is very sensitive, and the absolute value of the extinction ratio changes greatly with a slight angle deviation.

Therefore, accurate adjustment can be performed.

(2) Since the rotating mechanism on one side is manually rotated, if the birefringent main axes are substantially matched or substantially orthogonal to each other in advance by coarse adjustment manually, for example, the birefringent main axes will be matched. However, there is no mistake that feedback control is performed so that they are orthogonal to each other.

(3) From the characteristics of the polarization-maintaining optical fiber, even if self-alignment is performed while monitoring the extinction ratio, depending on the positional relationship of the fiber end faces to be connected, it is impossible to do so, and the amount of light passing through the splice is too great. Is reduced.

Therefore, if an attempt is made to perform automatic alignment by relying on the fluctuation of the optical power that has passed through the connecting portion, there is a possibility that alignment will be impossible.

However, according to the present invention, since the coarse alignment can be performed manually, there is no concern.

(4) Since the device for automatic adjustment uses the device for automatic adjustment in the xy direction (power monitor system) as it is, and only needs to add a polarizer and the like, the whole optical fiber aligning device is particularly suitable. It doesn't get complicated.

[Brief description of drawings]

FIG. 1 is an explanatory view of a plane of an embodiment of the present invention, and FIG. 2 is an explanatory view of a side surface thereof, III-III, IV-IV thereof,
V-V arrow views are shown in FIGS. 3, 4, and 5, respectively. FIG. 6 is an explanatory view of the field of view of the microscope, and FIGS. 7 (a) and 7 (b) are general explanatory views when connecting a constant polarization optical fiber. 12: optical fiber, 18: stress applying part 39: abutting rod, 41: mirror 40: bracket, 42: upper part of bracket 44A, B: rotating mechanism, 46: cylindrical part 48: dial, 50: groove 52: Fixed arm, 54: Movable arm 60: Cam, 61: Rotary clamp 62: Fixed part of rotary clamp 61 64: Same movable part, 66: V groove 68: Fiber guide, 70: Gear 72: Motor, 80: Wire 82: Constant tension spring, 84: Sensor plate 86: Optical sensor, 90: Light source 92: Polarizer, 94: Analyzer 96: Photodetector, 98: Optical power meter 99: Control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Go Yamada 1440 Rokuzaki, Sakura-shi, Chiba Fujikura Cable Co., Ltd.Sakura factory (72) Inventor Tsutomu Onodera 1440 Rokuzaki, Sakura City, Chiba Fujikura Cable Co., Ltd. 72) Inventor Mikio Yoshinuma 1-5-1 Kiba, Koto-ku, Tokyo Within Fujikura Electric Wire Co., Ltd. (72) Inventor Yasuyuki Kato 162 Shirane, Shirane, Tokai-mura, Naka-gun, Ibaraki Prefecture Nippon Telegraph and Telephone Corporation Ibaraki (56) Reference JP-A-59-49511 (JP, A) JP-A-60-260906 (JP, A) JP-A-56-83712 (JP, A)

Claims (1)

[Claims] 1. A fusion device comprising a mechanism capable of aligning an optical fiber in the x-direction and the y-direction, clamping the optical fiber, and rotating the optical fiber about the axis of the clamped optical fiber. When connecting the polarization-maintaining optical fiber by the connecting / disconnecting device, the rotating mechanism on one side is manually rotated, and the rotating mechanism on the other side is rotated by the motor. After manually rotating the optical fiber to roughly adjust the birefringent main axes so that they are substantially coincident with or at right angles to each other, and align the optical fiber by aligning the optical fiber in the x-direction and the y-direction. The rotation of the motor is automatically controlled so that the absolute value of the extinction ratio at the exit end of the polarization mode propagating through both the optical fibers becomes maximum. Wave splicing method for optical fiber.