JPS6215843B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently connecting optical fibers with low loss using an imaging device.

When performing fusion splicing of optical fibers, align the cores of the optical fibers, set the distance between the end faces of the optical fibers, and heat the end faces of the optical fibers at the softening point temperature of the optical fiber material. It is necessary to press the Conventional core alignment methods for this type of optical fiber include the following.

(1) Figure 1 shows an optical fiber core alignment method called the power monitor method. In this method, a light source 2 and a receiver 3 are arranged on the optical fibers 1 and 1' to be connected, and the cores of the optical fibers 1 and 1' are aligned in the x and y directions so that the transmitted power at the connection point is maximized. This is a method of matching. However, this method requires a large number of personnel and equipment, and has the drawback of poor work efficiency, since the work points for connection are distributed over three locations: the light source, the connection point, and the light receiving point.

(2) Literature, 1985 National Conference of the Institute of Electronics and Communication Engineers
934 "Method for aligning the core axis of a single mode optical fiber", page 4-131, there is a method that utilizes the fluorescence phenomenon caused by ultraviolet excitation of a Ge-doped optical fiber. However, this method requires a laser light source in the ultraviolet region, which has the disadvantage of increasing the size of the apparatus.

(3) Literature, Journal of the Institute of Electronics and Communication Engineers '82/5Vol.J65-
B, No. 5, P. 662 ``Single-mode optical fiber connection method without a monitor'', the optical fiber is immersed in a liquid with the same refractive index as its cladding, and the core is detected using a phase contrast microscope. There is a way to align the axes. However, this method
The drawback was that the core could not be detected in the air.

(4) There is a method of detecting the core of an optical fiber in air using a differential interference microscope and aligning the core. However, this method has the disadvantage that it requires a special device called a differential interference microscope, and that the design of the fine movement mechanism for aligning the optical fiber is limited by the size of the microscope body.

By the way, the distance between the end faces of optical fibers to be connected can be determined manually by an operator while visually observing the distance between the end faces of optical fibers using a marker installed in a microscope, or by determining when the end faces of opposite optical fibers to be connected are connected. There is a method in which the operator manually performs visual observation by separating the contact point by a certain distance using a fine movement mechanism such as a micrometer. However, this method is done manually, so
The disadvantage is that work efficiency is poor, and work quality deteriorates depending on skill level.

In addition, as shown in FIG. 2, the connected optical fiber 1
There is a method of setting the distance between the end faces by abutting the end face against an abutting plate 4 having a certain thickness. However, this method requires a special mechanism to move the abutment plate 4, and dust attached to both sides of the abutment plate 4 may adhere to the connection end surfaces of the optical fibers 1 and 1' to be connected, resulting in connection loss. There were disadvantages such as increased size.

In addition, the distance between the end faces is set to a constant value based on the amount of push-in of the optical fiber to be connected, etc., but the distance between the end faces changes depending on the roughness of the end face and the fusion heating temperature, so the actual push-in amount has changed, resulting in drawbacks such as connection failures and poor connection quality.

On the other hand, the heating temperature of the end face of the optical fiber to be spliced is set to a constant value based on the softening point temperature of the optical fiber material, the end face spacing, the temperature that reduces splicing loss, etc. In the case of gas discharge, fusion splicing The disadvantage was that the heating device settings had to be changed several times because the molten fibers were scattered onto the discharge electrode and the heating temperature changed.

In order to eliminate these drawbacks, the present invention uses an imaging device to detect the image and light intensity emitted by the optical fiber to be connected during fusion heating using a gas discharge device, and to adjust the axis of the core, adjust the pushing amount, and adjust the optical fiber. Optical fibers are fusion spliced while adjusting one or more of the fusion heating temperature adjustments at the splicing part.The purpose is to reduce splice loss, reduce splice failures, and improve splicing efficiency. be. The present invention will be explained in detail below with reference to the drawings.

FIG. 3 is a diagram showing one embodiment of the present invention, and shows 1,
1' is the optical fiber to be connected, 5 and 5' are the electric motors,
6, 6' are fine movement mechanisms, 7, 7' are optical fiber fixing bases, 8 is a gas discharge circuit, 9, 9' are discharge electrodes, 1
0 is a heating discharge unit, 11 is a filter, 12 is an objective lens system, 13 is an image sensor, 14 is an image sensor drive device, 15 is an image processing device, 16 is a control device, and 17 and 17' are electric motor drive units. .

To operate this, the coated and cut fibers are placed on optical fiber fixing tables 7, 7' that are moved in the x, y, and z directions by fine movement mechanisms 6, 6' driven by electric motors 5, 5'. The optical fibers 1 and 1' to be connected are fixed facing each other. Optical fiber fine movement mechanism system 5,
5', 6, 6', 7, 7' send the optical fibers 1, 1' to be connected in the z direction, and the connecting portion of the optical fiber 1 to be connected is connected to the discharge electrodes 9, 9 driven by the gas discharge circuit 8. When reaching the heating discharge section 10 that occurs between
The cladding and core portions of the optical fibers 1 and 1' to be connected are softened by heat, and at the same time, the core containing Ge dopant absorbs the ultraviolet light generated during the gas discharge, causing the optical fibers in the visible wavelength range to appear as shown in Fig. 6a. As shown, fluorescent lights 20 and 20' are generated at different positions. At this time, the connected optical fiber 1, The position of the core of 1' in the x direction is
The light intensity distribution shown in FIG. 6a can be detected by observing it from the y direction with the imaging device through the filter 11. On the other hand, the core position in the y-direction orthogonal to the x-direction can also be detected by observing from the x-direction with the imaging device in the same manner as in FIG. 6a. Further, the opposed connected optical fibers 1,
The distance between the end faces 1' can be detected by the imaging device as a distance d from the light intensity distribution in the z direction shown in FIG. 7b. Furthermore, the heating temperature of the connecting portion of the optical fibers 1, 1' to be connected can be detected by the imaging device as the light intensity P from the light intensity distribution in the z direction shown in FIG. 7b. In the manner described above, the core position, the distance between the end faces, and the heating temperature of the optical fiber to be connected in two orthogonal directions can be detected. FIG. 4 shows a side view of this imaging device. The control device 16 controls the electric motor drive units 17, 17' based on the signal from this imaging device, and the right angle By adjusting the positions of the connected optical fibers 1 and 1' in the x and y directions in the two-direction imaging system so that the positions of the fluorescent lights 20 and 20' obtained from the imaging device as shown in FIG. 6 coincide with each other. , align the cores of the optical fibers 1, 1' to be connected. In addition, the remaining amount of movement in the z direction, that is, the amount of pushing of the optical fibers 1 and 1' to be connected, is
The emission intensity P of the fibers 1 and 1' in the heating section 10 shown in FIG. 7 obtained from the imaging device based on the distance d between the end faces shown in FIG. 7b obtained from the imaging device is determined at a predetermined heating temperature. By adjusting the current of the gas discharge circuit 8 according to the light intensity corresponding to the heating temperature, the heating temperature can be kept constant. Therefore, for illumination of the connected optical fiber 1, there is no need for a lighting device, and since the heating temperature is constant, that is, the light intensity emitted by the optical fiber is constant, there is no need to adjust the brightness of the light source. . Furthermore, even if the molten fiber is scattered and attached to the gas discharge electrodes 9, 9' during fusion splicing, the intensity of the light is directly detected, so that the heating temperature can be adjusted to a constant value. Note that the light emitted from the gas discharge itself has a lower light intensity than the light generated by heating the optical fiber, so there is no need to pose a problem.

In this embodiment, the imaging systems 11, 12, 13,
14, but by introducing an optical system using two mirrors 18, 18' and one half mirror 19, as shown in FIG. For one direction, the imaging systems 11, 12, 13, and 14 can be omitted.

Furthermore, in this example, a case is described in which the core alignment, push-in amount, and heating temperature of the optical fiber to be connected are adjusted at the same time, but in the case of a single mode optical fiber, core alignment is necessary. However, in the case of multimode optical fibers, core alignment may not be necessary. However, even in the case of multimode optical fibers, core position detection can be used to check the quality of the work.

In this embodiment, the connected optical fibers 1,
If there is a problem that the operating speed of the fine movement feed system 5, 5', 6, 6', 7, 7' of 1' is slow compared to the fusion splicing speed, perform so-called preheating discharge,
Alternatively, the problem can be solved by setting heating conditions such as heating time, heating intermittent time, and heating temperature.

As explained above, since the optical fiber fusion splicing method of the present invention utilizes light emission by heating the optical fiber, it has the advantage that the configuration of the splicing device is simplified, such as eliminating the need for an illumination device for the optical fiber. others,
Compared to illumination methods using transmitted light or reflected light, this method has the advantage that there are fewer negative effects such as a decrease in resolution due to the lens effect of the connected optical fiber.

Furthermore, since it uses the ultraviolet light generated during gas discharge, it does not require a light source in the ultraviolet region. Therefore, there is an advantage that the connecting device itself can be made smaller and more economical.

In addition, the fundamentally important connection conditions such as the alignment of the core of the optical fiber to be connected, the amount of push-in, and the heating temperature of the connection part are adjusted, resulting in optical fibers with low loss, fewer connection failures, and high work efficiency. It has the advantage of being able to realize connections between

Therefore, it will greatly contribute to the practical application of communication systems using optical fiber cables.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of how to align the cores of optical fibers to be connected using a conventional power monitor, Figure 2 is an explanatory diagram of how to set the distance between the end faces of optical fibers using an abutment plate, and Figure 3 is One embodiment of the present invention, FIG. 4 is a side view of the imaging device for detecting the core of the optical fiber to be connected in FIG. 3, and FIG. Figure 6a is an explanatory diagram of a situation in which the core of an optical fiber generates fluorescence, and Figures 6b and c are diagrams on the x-x line near the fusion splice in Figure 6a. and a diagram showing the light intensity distribution on the x'-x' line, Figure 7a is an explanatory diagram of the situation in which the optical fiber emits light when it becomes high temperature, and Figure 7b is a diagram showing the light intensity distribution on the z-z line in Figure 7a. FIG. 2 is a diagram showing a light intensity distribution of FIG. 1... Connected optical fiber, 2... Light source, 3...
Light receiver, 4... Abutment plate, 5, 5'... Electric motor, 6, 6'... Fine movement mechanism, 7, 7'... Optical fiber fixing base, 8... Gas discharge circuit, 9, 9' ... Discharge electrode, 10 ... Heating discharge section, 11 ... Filter, 12 ... Objective lens system, 13 ... Image sensor, 14 ... Image sensor drive device, 15 ...
...Image processing device, 16, 16'...Control device, 1
7, 17'...Electric motor drive section, 18, 18'...
...Mirror, 19...Half mirror, 20, 20'
...Fluorescence, d...Distance between the end faces of optical fibers to be connected, P...Emission intensity.

Claims (1)

[Claims] 1. In a method of fusion splicing optical fibers by heating and abutting the end faces of opposing optical fibers to be spliced, a core containing a Ge dopant is heated during fusion splicing using a gas discharge device. A photographing device that uses the phenomenon of generating fluorescence by absorbing the generated ultraviolet light to determine the core position of the optical fiber to be connected, and the distance between the end faces or the heating temperature from the image of the optical fiber emitted by heat. By detecting this using a An optical fiber fusion splicing method using an imaging device characterized by fusion splicing fibers.