JPH0352604B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an optical fiber fusion splicing apparatus designed to quickly and automatically perform permanent splicing with extremely high precision.

<Prior art> Conventional methods for connecting optical fibers include a method using a connector that can be separated at will even after connection, and a method using a permanent connection (splicing) that cannot be separated after connection. There is a method. In general, connectors are known to have a greater connection loss than permanent connectors due to reflection loss at the end face of the optical fiber, and these are used as appropriate depending on the conditions of use.

By the way, in order to permanently maintain communication optical fibers such as submarine optical cables that are often used as long-distance transmission lines, a fusion splicing method is used, which is less likely to deteriorate over time. Normally, when optical fibers are fused and spliced to each other, the end surfaces of the optical fibers are coaxially abutted against each other, and then the fusion spliced is performed by electrical discharge heating. In this case, if the core that participates in light transmission is eccentric with respect to the optical fiber, it is impossible to achieve the best connection simply by positioning the optical fiber coaxially, and this tendency tends to change as the core diameter increases. This is particularly noticeable in small single mode optical fibers. For this reason, there is generally a method of passing light from one optical fiber to the other optical fiber and adjusting the relative position of the butt ends of the two optical fibers so that the amount of light received by the other optical fiber is maximized. It has been adopted.

<Problems to be solved by the invention> When a repeater or the like is already connected to an optical fiber, such as in a submarine optical cable, a method is adopted in which light passes from one optical fiber to the other. This is fundamentally impossible, and since submarine optical cable connections are made at sea, there are many restrictions such as ship vibrations and ocean weather, making it difficult to establish a good permanent connection.

Based on this knowledge, the present invention focuses on the fact that the core position can be accurately determined when observing an optical fiber with transmitted illumination, and it is possible to maintain the optical fiber permanently in a short period of time with high precision. The purpose is to provide a device that can perform this automatically.

<Means for Solving the Problems> The optical fiber automatic connecting device of the present invention connects the abutted ends of two permanently sustained optical fibers in opposite directions and in two directions perpendicular to the opposite directions, respectively. a positioning drive device that can move relative to the two optical fibers, a fusing device that heats and fuses the butt ends of the two optical fibers, and an illumination device that transmits and illuminates the butt ends of the two optical fibers from the two directions. and an imaging device that is arranged opposite to the transmitted illumination light of these illumination devices across the abutted ends of the two optical fibers, and that obtains a transmitted image of the abutted ends of the two optical fibers; From the brightness distribution caused by the lens action of the two optical fibers and the refractive index difference between the core cladding of the two optical fibers in the transmitted image, the center of the core cladding boundary is determined as the core center; an image processing device that detects the axis misalignment of the cores of the two optical fibers along the two directions, and an image processing device that detects the axis misalignment of the cores along the two directions from the image processing device; and a control device that controls the operation of the positioning drive device so that the cores of the two optical fibers are coaxial.

<Operation> The abutting ends of the two optical fibers held by the positioning drive device are illuminated by the illumination device, and based on the transmitted image from the imaging device obtained thereby, the image processing device detects the two beams of light. The axis misalignment of the fiber cores is detected from two different directions, and based on this axis misalignment signal, the control device controls the operation of the positioning drive device so that the cores of the two optical fibers are coaxial, and then the fusion is performed. The device is activated to heat and fuse the butt ends of the two optical fibers.

<Example> As shown in FIG. 1 showing the state of connection work according to the present invention, a fixed base 11 and a movable base (positioning drive device) 12 corresponding to each other are provided with a structure for fixing optical fibers 13 and 14, respectively. A presser metal fitting 15 is provided. The presser metal fitting 15 of the movable base 12 is slidable in two directions, one in which the butt ends of the optical fibers 13 and 14 face each other and in two directions perpendicular to the opposite direction, representing the control system of this embodiment. As shown in FIG. 2, the movement in the two directions is performed by the operation of two drive motors 16 and 17 built into the movable table 12, and the movement in the opposite direction is also performed by the operation of a drive source (not shown). It is now being carried out by The drive mechanism of the presser fitting 15 of the movable base 12 can be the same as the conventional one, and the fixed base 11 can also be used as the movable base 1.
A configuration similar to 2 may be used, but in short, it is only necessary that the relative positions of the abutting ends of the two optical fibers 13 and 14 can be arbitrarily adjusted by some driving source. This fixed base 11 and movable base 1
A pair of discharge electrodes (fusion splicing device) 18 are installed between the optical fibers 13 and 14 to face each other across the abutting ends of the optical fibers 13 and 14, and to fusion splice these parts, and are further connected to a light source 19. The light emitting ends of the pair of light guides 20 and 21 are positioned so as to face the two directions, respectively. optical fiber 1
A television camera 24 is attached to each of the pair of microscopes 22 and 23 facing the light emitting ends of the pair of light guides 20 and 21 with the abutted ends of the light guides 20 and 21 in between. The optical fibers 13 and 1 are illuminated from the two directions by transmitted illumination light from the light guides 20 and 21.
The butt ends of No. 4 are now observed.

Although a pair of microscopes 22 and 23 and a television camera 24 are provided in this embodiment, as shown in FIG. ,2
By arranging the reflecting mirror 25 facing either one of the optical fibers 13 and 14 at an angle, the abutting ends of the optical fibers 13 and 14 can be observed from two different directions using only one of the microscopes 22 and the television camera 24. Also, it is of course possible to use other well-known magnifying optical systems in place of the microscopes 22 and 23.

The output from the television camera 24 is input to an image processing device 26, and as shown in FIG. The axis deviation x, y of the cores 13a, 14a along the direction is electrically detected and calculated, and as is well known, the optical fibers 13, 14 themselves act as cylindrical lenses, and the brightness of the optical fibers As shown in FIG. 5, which shows an example of the distribution, the obtained transmission image shows the cores 13a and 14 of the optical fibers 13 and 14.
It takes advantage of the fact that a difference in brightness and darkness appears at the boundary between these parts due to the difference in refractive index between a and the claddings 13b and 14b, and this state can be observed on the monitor television 27 provided in this embodiment.
Specifically, vertical sampling lines S ₁ and S ₂ are set on a television receiver (not shown), and the brightness distribution of the scanning line is measured along the sampling lines S ₁ and S ₂ to determine the cores 13a and 14a. 13
The boundary between the cores 13a and 14b is detected, and the center of this boundary is set as the center position of the cores 13a and 14a. Note that sampling S ₁ and S ₂ are performed using optical fibers 13 and 14.
are set at 100 to 300 micrometers from the butt ends of each. The brightness distribution along the sampling lines S ₁ and S ₂ is as shown in FIG. 5, and the change in brightness at the boundary of the core cladding, which is the object of observation, is extremely small.
Therefore, even if there is an error in reading each boundary, the error can be reduced by reading the centers of two boundaries located at symmetrical positions.

A control device 28 for controlling the operation of the drive motors 16 and 17 described above is connected to the image processing device 26, and the centers of the cores 13a and 13a of the optical fibers 13 and 14 are controlled based on signals from the image processing device 26. Although it works so that the signals are coaxial, it is actually a differential circuit that functions so that the detection signal of the image processing device 26 becomes zero. In other words, the drive motors 16, 17
is a constant speed motor, the control device 28 replaces the axis deviation signal with a drive time, and the drive motor 16,1
The drive motors 16 and 17 are rotated for a period of time such that the amount of rotation of the motor 7 becomes equal to the amount necessary for correcting the axis deviation. In addition, when the drive motors 16 and 17 are pulse motors, the control device 28 replaces the axis deviation signal with the number of pulses, and generates a pulse such that the amount of rotation of the drive motors 16 and 17 is equal to the amount required for axis deviation correction. The drive motors 16 and 17 are rotated by the number of rotations.

Therefore, the two optical fibers 13 and 14 are held on the fixed base 11 and the movable base 12 by the presser metal fittings 15, respectively.
After fixing it on top and operating the drive source so that these abutting ends come close to each other, automatic operation is started. From the image observed by the television camera 24 through one of the microscopes 23, the image processing device 26 calculates the axis deviation x of the cores 13a, 14a of the optical fibers 13, 14 in a plane perpendicular to the observation direction.
, and the control device 28 operates one of the drive motors 16 so that this value becomes zero. Similarly, the television camera 24 is connected to the other microscope 22.
From the image observed at
The axis deviation y of a and 14a is detected by the image processing device 26, and the control device 28 operates the other drive motor 17 so that this value becomes zero.

According to experiments, a microscope with a magnification of 200x22,
23 and a television camera 24 with about 1,000 scanning lines to perform image processing, it was possible to position the centers of the cores 13a and 14a with a detection accuracy of 1 micrometer or less, and the average It was found that misalignment could be suppressed to less than 0.5 micrometers.

From the above-mentioned state, the presser metal fitting 15 of the movable base 12 is moved a certain amount toward the fixed base 11 side, and the discharge electrode 1
8 and the abutting ends of the optical fibers 13 and 14 are fused and spliced by discharge heating, and the final splice loss can be reduced to a low value of about 0.1 dB. In addition, when working on a ship, it is preferable to install the entire apparatus on a vibration isolating table and set the dimensions and shapes of each part so that resonance does not occur.

<Effects of the Invention> According to the optical fiber automatic connection device of the present invention, images of the butt ends of optical fibers are imaged from two directions using transmitted illumination, and two connections are made from the outline of the core using image processing and a control device. Since these are automatically moved relative to each other so that the centers of the cores of the optical fibers coincide, it is possible to align the axis with extremely high precision even for small-diameter cores such as single-mode optical fibers. This makes it possible to shorten work time, automate the process, and improve the reliability of optical cable connections on ships.

[Brief explanation of drawings]

FIG. 1 is a working conceptual diagram showing the schematic structure of one embodiment of an automatic optical fiber connection device according to the present invention, FIG. 2 is a block diagram showing its control principle, and FIG. 3 is a diagram showing another embodiment of the present invention. FIG. 4 is a conceptual diagram showing an example of a transmitted image, and FIG. 5 is a graph showing the brightness distribution of the optical fiber. Further, in the figure, 11 is a fixed base, 12 is a movable base, 13 and 14 are optical fibers, 13a and 14a are cores, 13b and 14b are claddings, 15 is a presser metal fitting, 16 and 17 are drive motors, and 18 is a A discharge electrode, 19 a light source, 20 and 21 a light guide,
22 and 23 are microscopes, 24 is a television camera, 25
is a reflecting mirror, 26 is an image processing device, 28 is a control device, and x and y are axis deviations of the core.

Claims (1)

[Claims] 1. A positioning drive device capable of relatively moving the abutting ends of two permanently connected optical fibers in opposing directions and in two directions perpendicular to the opposing directions, and the abutting ends of the two optical fibers. a fusion device that heats and fuses the two optical fibers; a lighting device that transmits and illuminates the butt ends of the two optical fibers from the two directions; and a lighting device that holds the butt ends of the two optical fibers in between. an imaging device that is arranged to face the transmitted illumination light of and obtains a transmitted image of the abutting ends of the two optical fibers; a lens action of the two optical fibers and the two lights in the transmitted image; From the brightness distribution caused by the difference in refractive index between the core and cladding of the fibers, the center of the boundary between the core and cladding is determined as the core center, and from this, the axis misalignment of the cores of the two optical fibers along the two directions is determined. an image processing device that detects the image processing device; and an actuation of the positioning drive device so that the cores of the two optical fibers are coaxial based on axis deviation signals of the cores along the two directions from the image processing device. An optical fiber automatic connection device consisting of a control device that controls the