JPS5995506A - Optical fiber connecting method - Google Patents

Abstract

PURPOSE:To improve the efficiency of connecting operation and to reduce labor by detecting core positions through a microscope with a differential interfering function in two directions perpendicular to the axes of two fibers to be connected, and aligning and connecting the fiber only at a connection point. CONSTITUTION:The two fiber element wires 1 and 1' are arranged with end surfaces close to each other in the visual field where one microscope which consists of a light source 4, objective 6, and ocular 7 and has the differential interfering function is set in a direction X and another microscope is set in a direction Y; and the fibers are observed through oculars 7 and 7' in the orthogonal directions. When the cores of the fiber element wires 1 and 1' shift in position at this time, the grip part for the fiber 1' is moved finely to align axial centers to each other until they coincide completely with each other, and then they are welded by a discharging electrode 33. Thus, the alignment is performed with high precision only at the connection point and the operation is automated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for aligning the axes of two optical fibers and connecting the optical fibers without monitoring the transmission loss between the two fibers to be read. .

Conventionally, in the connection of single mode fibers, the axis alignment of a pair of fibers to be connected is done by gripping the fibers with a gripper that can be finely moved in 3 axes, and then adjusting the axis alignment of the core using gripper-1 and the alignment between the core and the cladding. In order to correct the axis misalignment caused by the eccentricity of the fiber, light is passed in the axial direction of the fiber, and the gripping tool is finely adjusted to minimize the amount of attenuation of the glare, thereby aligning the cores of the fiber with each other.

However, when actually performing the connection work at the work site using this method, the attenuation amount is measured, so the work place is divided into eight locations: the light source, the connection point, and the light receiving point, and each work location corresponds to This method had the disadvantages of having to deploy a large number of personnel and equipment, resulting in poor work efficiency and economical issues.

In addition, in the past, in order to observe the core of an optical fiber, there was an example of using a curved optical microscope and roughly immersing the fiber in matting oil to observe the position of the core, but the resolution was very poor. , and the core is almost undetectable, thus defeating its purpose. It had the disadvantage that it was not a complete <1 inkstone festival in the Mochiron air.

In order to eliminate these drawbacks, the present invention uses a microscope with a differential interference function to align and connect the fibers to be connected only at the connection point.The purpose of this invention is to improve the efficiency of the connection process. and labor saving. Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, 1, 1. ' is a bare fiber, 2, 2' is a coating of the optical fiber, 3°3' is a fine movement device, 4 is a light source, 5 is a condenser lens having a differential interference function, 6 is an objective lens having a differential interference function, 7 is an eyepiece, and IO is an observer. Although not shown in the figure, No. 1B is provided with another set of virtual d-threads having a differential interference function in the vertical direction at the low turn. It is also equipped with an e t[i pole for heating the fiber.

FIG. 2 is a schematic view of FIG. 1 viewed from the A-A' direction, where l is the optical fiber, 4 and 4' are the light sources, and 5° and 5' are the differentials in the orthogonal X and Y directions, respectively. A condenser lens having an interference function, 6 and 6' objective lenses having a differential interference function, 7 and 7' eyepiece lenses, 8 a prism that bends the optical axis in the Y direction, 9 a core, and 10 and 10' an observer. , 33 is a V electromagnetic pole. 0 Figure 3 (a) is a schematic diagram when a single mode fiber is observed in air using a microscope with differential interference function, and Figure 3 (b) is a diagram showing the intensity of transmitted light. Show the distribution. 11, 11' is a dark area visible outside the outer periphery of the core, 12.12' is a bright area corresponding to the outer periphery of the core (bright area outside the core), 18.13' is a dark area corresponding to the inside of the core (inside the core). 14.14' is the bright part visible inside the cladding, 15.15' is the darkest part visible as the reversal of the outer circumference of the cladding, 16.16' is the outside of the cladding,
17, 17/ is a bright area visible at the outer edge of the cladding,
18 and 18' are the background, and 19 and 19' are the outer periphery of the core. When the fiber is observed using an optical microscope having a differential interference function in this way, the core can be clearly observed.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

As described in the prior art, in order to correct the axis misalignment caused by the fiber gripping force and the eccentricity of the core, the first step is to
Place the two fibers within the field of view of the microscope as shown in the figure, and place the eyepieces in the eyepiece so that they are perpendicular to each other.

When observed from the Y direction, it looks like Figure 4.

FIG. 41(a) shows the case when viewed from the X direction, and the cores are aligned, but when viewed from the Y direction (FIG. 4(1)), an axis misalignment in the X direction can be observed in the cores. Therefore, the gripping portion of the fiber 1' is moved slightly in the X direction to align the axis. If the core positions match in both the X and Y directions, the cores are completely aligned. When the axes are aligned, the fibers are fused in a well-known manner by heating the discharge poles.

FIG. 5 shows an embodiment of f[[I, of the present invention, 20°2
0' is a mirror, and 21 is a wedge-shaped mirror.

This practical example makes it possible to cross the legs in the X and Y directions in the same field of view, and the transmitted light from both directions is reflected by the mirror 20°20
', 21 and guided into the eyepiece.

A prism may be used instead of the mirrors 20 and 20'.

FIG. 6 shows an example of an observed image according to the embodiment of FIG. 5. No. 1,
In figure b, by observing from the Y direction (the image at the top of the circle in figure 6), the axis deviation of the core can be observed in the X direction (c).
Move the grip slightly to align the core axis. The image at the bottom of the circle in FIG. 6 shows an image observed from the X direction.

Note that an optical microscope having a phase contrast function may be used instead of the optical microscope having a differential interference function described above.

FIG. 7(a) is a schematic diagram when a single mode fiber is observed in air using an optical microscope having a phase contrast function. FIG. 7(b) shows the intensity distribution of transmitted light. Figure 7(a).

In (1)), 22 and 22' are dark areas corresponding to the inside of the core, 23 and 28' are bright areas outside the core, and 24°24
' is the dark part inside the cladding, 25.25' is the darkest part visible inside the outer periphery of the cladding, 26.26' is the outer periphery of the cladding, 27.27' is the bright part visible outside the cladding, 28
, 28' is the background, and 29.29' is the outer periphery of the core.

As explained above, even if an optical microscope having a phase contrast function is used, the core can be observed in air without using matching oil, so it can be used to align the axis of a single mode fiber.

FIG. 8 shows an example of a fusion spliced portion of a single mode fiber observed from one direction using the optical fiber splicing method of the present invention. Actual observation involves observing and photographing the core in air using an optical g-microscope with a phase contrast function, and observing the core in air and in matching oil using an optical microscope with a differential interference function. , I went and took pictures.

Figure 8 is based on a photograph taken using a microscope with a differential interference function after immersing the fiber in matching oil.
1 indicates the fusion point, and 32.82' indicates the outer periphery of the cladding.

In the examples in air, the core could be identified in both cases when observed using a microscope with a phase contrast function and when observed using a microscope with a differential interference function, but it was more clearly identified in the latter case. In order to obtain a very clear image, it is sufficient to immerse the fiber in matching oil and observe it with a microscope equipped with a differential interference function. It has become possible.

FIG. 9 shows an embodiment of the present invention, in which 84 is a TV camera, 85 is an m-image processing device, and 36 is a control section for a fine movement device. Although not shown in Fig. 9, an optical system similar to that shown in Fig. 2 or Fig. 5 is installed so that the core position can be viewed simultaneously from the direction perpendicular to the page using a single TV camera. It is located. Also, 11 N % is not shown. In this embodiment, instead of an observer observing the core position and manually adjusting the fine adjustment device,
This is an example of automatic alignment using image processing, for example, processing to match the light intensity distributions of two optical fibers to be connected. However, instead of the original TV camera, a one-dimensional diode sensor array may be used.

FIG. 1O shows another embodiment of the invention and is a schematic diagram of a fusion splicer. Two condenser lenses 5.5' and 5.5' are disposed between the 3-axis tracking device 3.8' and are connected to the light source 4 by bundle fibers 37 and 37', respectively, and the fiber wire 1 .1' is illuminated from two directions. The objective lenses 6 and 6' are placed on the top surface of the fusing device with their optical axes aligned with the condenser lenses 5 and 5' in each direction, and the observation images in the two directions are made into one by a prism system (not shown). The core is observed through a single eyepiece lens 7. 33, 33' is included■
It is an electrode, and is retracted so as not to interfere with the observation while observing the axis misalignment of the core.

FIG. 11 is an enlarged view of the axis alignment part of FIG. 1O, and 8
8 and 88' are single-object lens moving motors; 39 and 3;
9' is a motor for moving the condenser lens, 40 and 40' are rack wheels for moving the objective lens, and 41° and 41' are rack gears for moving the condenser lens.

42, 42' are objective lens moving gears, 48, 43
' is a gear for moving the condenser lens, which is connected to the motor, and moves the objective lens and condenser lens forward and backward when the motor is operating. In addition, the crest electrode 33° 33' is movably inserted into a guide pipe 44, 44' made of an insulating material, and the rear part thereof is connected to a JJ commutator moving solenoid (not shown). . When the solenoid is in operation, the four poles advance to a predetermined electrode spacing l. When the solenoid is stopped, the d pole is moved back by springs 45 and 45'. Figure 11 (a
) shows the state in which the core of the fiber is being observed with the electrode retracted, and Fig. 11(b) shows the state in which the lens is retracted and further
The state shown is that the pole is advanced and set at the lowest potential. Next, to connect a fiber using this device, first grip the fiber in the following device, stop the electrode solenoid, move the electrode 2 backward, and roughly advance the objective lens and condenser lens. Observe the core of the fiber. Next, after operating the fine movement device μ to align the axes, the lens is retreated, the electrode solenoid is operated to advance the electrode to the discharge position, and the fiber is heated and fused. complete.

Figure 12 is an enlarged view of the IIqII mating part when the fiber is immersed in matching oil and the core is observed, (a) is a schematic view as seen from the axial direction of the fiber, (b)
is a cross-sectional view taken along one length of the fiber.

46 is 'dN to put matching oil 417,
In the center of the support rod is a hole 4 connected to a pump (not shown).
8 is open. 49 is a lid of a container in which matching oil is immersed. The tips of the support rods of both the container 46 and the lid 49 are movably fitted into guide vibrators 50, 50', and the rear portions thereof are connected to a container moving solenoid (not shown). When the solenoid is activated, the container and lid fit together to sandwich the fiber as shown. Either fill the container with matching oil in advance, or fill it with mating oil after fitting the mataha container.

In this case, a hole is made in the lid for injecting the matching oil, or a pump is used to supply the matching oil through the hole 48.

A glass window 51 is provided in a portion corresponding to the original axis of the lens.
51', 52, and 52' are opened so that the fibers inside the container can be observed.

When the container is filled with matching oil, the surface tension of the matching oil itself prevents the oil from leaking out of the container.

Next, a method for performing axis alignment using Example II will be described.

After the fiber is gripped by the following device, when the solenoid for moving the container is moved 1/closed, the container and the lid are fitted together. After that, match oil is poured into the container. In this state,
Similar to the embodiment described with reference to FIG.
Observe the core of the fiber through ', 52, 52' and perform alignment.

When the Q$J adjustment is completed, first move the lens backward, then stop the container moving solenoid, and the springs 58 and 5
8' retracts the container and lid.

At the same time, the matching oil is sucked in by the pump to prevent the matching oil from leaking out of the container. The operation of the pump is adjusted to occur immediately before the container movement solenoid stops (just before the container lid opens). After retracting the container, connections are made in the same manner as in the embodiment shown in Fig. 11. However, if a mixture of glycerin and alcohol is used as the matting oil, the oil will be completely burned during the core reforming heating process, and the fibers will be It is possible to cause damage to all < tlle < , M sequences.

As explained above, the connection method of the present invention has the advantage that it is easy to align the fiber axes only at the connection point, which improves work efficiency and saves labor. be.

Furthermore, the present invention is a temporary method suitable for automatically forming an optical fiber into a 1D model, that is, automatically removing the coating, cutting, aligning, fusing, and reinforcing the optical fiber.

[Brief explanation of drawings]

Fig. 1 is a diagram showing one embodiment of the present invention, Fig. 2 is a schematic diagram as seen from the A A' direction in Fig. 1, and Fig.
Figures (al and (1)) are diagrams showing the observed image and light intensity distribution of field a obtained by observing a single-mode DRA C fiber using a microscope with a differential interference function. FIG. 5 is a diagram showing an example of the pond of the present invention; FIG. 6 is a diagram showing an observed image in the example shown in FIG. 5d; FIG. 7 (al and (bl are Figure 8 shows the observed image and light intensity distribution when a single mode optical fiber is observed using a microscope with a phase contrast function. Fig. 9 shows an example of a pond according to the present invention, and Fig. 10 shows another embodiment of the present invention. Schematic diagram of Figure 11 (a) and (b) are enlarged views of the alignment part of No. 1013, Figure 12 (a) and (b i) are immersing the fiber in matching oil and observing the core. It is an enlarged view of the axis alignment part in the case. ■, 1'... Optical fiber bare wire, 2, 2'... Optical fiber torn part, 3, 8'... Fine movement device, 4, 4
'... Light source, 5.5'... Condenser lens with differential interference function, 6.6'... Objective lens, 7, 7
'...eyepiece, 8...prism, 9...core, 1fJ, 10'...observer, 11, 11'...
Dark areas visible outside the outer periphery of the core, 12, 12'...
Bright area outside the core, 13,13'...dark area inside the core,
14.14'...Bright area visible in the cladding, 15.1
5'...The darkest part visible as a reversal of the outer circumference of the cladding, 16
．． 16'...Outer periphery of the cladding, 17°17'...Bright part visible on the outer edge of the outer periphery of the cladding, 18°18'...
Background, 19.19'...outer circumference of core, 20°2 0'
... Mira, 21 ... Nail-shaped Mira, 22. 22'...Dark part inside the core, 28.23'...Bright part outside the core, 24, 24'...Dark part inside the cladding, 25°25'...Darkest part inside the outer periphery of the cladding. 2
6.26'...outer circumference of cladding, 27,27'...
Bright area visible on the outside of the cladding, 28.28'...background, 29.29'...outer periphery of the core, ao, ao
'... Outer periphery of core, 31... Melting point, 82, .
32'... Outer periphery of cladding, 38... Radiation, intense magnetic pole, 84... TV camera, 35... Image processing device, 3
6...Control section of fine movement device, 37.37'...
・Bundle fiber, 88, 38'...Motor for moving objective lens, 39, 39'...Motor for moving condenser lens, 40,410'...Rack gear for moving objective lens, 41.41'...・Rack gear for condenser lens A hyperactivity, 42, 42'... Teeth star for objective lens 4 hyperactivity, 43, 43'... Gear for moving condenser lens, 4444'... Guide vibe, 45.415'
... Spring, 46... Container, 47... Matching oil, 4+8... Hole, 49... Lid, 5 FJ,
50'...Guide pipe, 51, 51'. 52, 52'...Glass window, 53, 5 a'...
・Spring. Patent Applicant Nippon Tunshin Tunwa Public Corporation Figure 1 Figure 2 (b) Fig. 8 32' Fig. 9 1θ Fig. 11 (a) 33- Fig. 11 (b) Fig. 12

Claims (1)

[Claims] L: Detect the core position of the 2* fibers to be connected at least 20,000 times perpendicular to the axes of the fibers using an optical microscope with a differential interference function, and adjust the axes of the fibers using a fine adjustment device. An optical fiber connection method characterized in that the axial positions of these fibers are aligned and followed by fine adjustment of the fibers. An optical fiber connecting method according to claim 1, characterized in that the core position of the fiber is detected by immersing the fiber in matching oil. & An optical fiber splicing method according to claim 1 or 2, characterized in that the fibers whose axial positions are adjusted are fused by heating and connected.