JPS60232515A - Apparatus for producing optical fiber coupler - Google Patents

Abstract

PURPOSE:To prevent exertion of undue tension on optical fibers during stretching speed by floating stretching bases by gas to make the bases freely movable and moving the stretching bases by means of a weight suspended with wire rods to the stretching bases. CONSTITUTION:The gas is introduced through gas introducing pipes 418, 418a into base plates 410, 410a of a stretching device and the gas is ejected toward the stretching bases 49, 40a when a stretching stage is started. As a result the bases 49, 49a are floated by the gaseous pressure and are made freely glidable and movable on the base plates of the stretching device. The bases 49, 49a are connected to the weight 415 through wires 412, 412a and these stretching bases receive the force in the directions where the bases are parted from each other. When the welded part is heated by an oxygen propane flame burner 48, the bases 49, 49a move toward the direction where the bases are parted from each other by the weight 415. The welded part of the optical fiber is thus smoothly stretched without receiving undue stress.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an apparatus for manufacturing an optical fiber coupler used in the fields of optical communications and optical fiber sensors.

[Prior art and its similar issues]

The optical fiber coupler fuses parts of two optical fibers 1-1a and 2-2a as shown in FIG.

By stretching, the light incident on one fiber 1 (or fiber 2) is fused and split into the other fiber 2 (or fiber 1) side at the stretching part so that it can be emitted from both fibers 1a and 2a. It is used as an optical circuit component connected to optical fiber in the fields of optical communications and optical fiber sensors.

In addition, recently, a single mode optical fiber that stably preserves linearly polarized waves along its principal axis over long distances has been developed, and is called a linear polarization maintaining optical fiber, which has made a new appearance in the fields of optical communications and optical fiber sensors. However, when such a linear polarization maintaining optical fiber is used, the optical fiber coupler connected to the optical fiber is also required to have linear polarization maintaining property.

As an optical fiber coupler connected to such a linear polarization maintaining optical fiber, an optical fiber coupler having a structure shown in FIG. 6 has been proposed.

This optical fiber coupler is made by fusion bonding and stretching of two linear polarization maintaining optical fibers 2l-21a and 22-22a, each linear polarization maintaining optical fiber 2l-21a, 22-22a has a stress applying part 25 in the cladding part 24b around the core part 24a, and the linear polarization maintaining light 7? Iba spindle 26
a, the fused and stretched parts 2 so that the 26 sides are aligned parallel to each other.
It has a structure in which optical fibers are arranged in a cross section 27 of 3. Thus, the main axis 26a of each optical fiber.

If the optical fibers are arranged in such a way that the optical fibers 26b are aligned in parallel, the linearly polarized wave 28 incident on the optical fiber 21 will be
The light propagates along the main axis of the optical fiber, is split into the other optical fiber at the fusion and stretching section 23, and is emitted from the optical fiber 218.2'2a as linearly polarized light 29.210, respectively.

As described above, in addition to the example shown in FIG. 6, two other arrangements of two optical fibers are known in which the linear polarization state is not destroyed in the fusion/stretching section 23. If this is shown together with the one shown in Fig. 6, the 7th
As shown in the figure (in Figure 7, reference numeral 31 indicates a fusion operation), when manufacturing these optical fiber couplers, fusion is required to suppress the crosstalk of the optical fiber couplers. It is necessary to arrange the linear polarization-maintaining optical fibers to be attached in advance so that their principal axes are aligned as shown in the figure. To explain this point specifically, in order to reduce the crosstalk to -20 dB or less, in the arrangement shown in Figure 7(a), it is necessary to suppress the arrangement error from the ideal arrangement shown to 5 degrees or less. (Reference: Masao Kawachi, Institute of Electronics and Communication Engineers, Microwave Research Group Materials MW83-85).

By the way, as a conventional optical fiber coupler manufacturing apparatus, the one shown in FIG. 8 is known.

In Figure 8, 1-18.2-2a is an optical fiber, 3
．． 3a is a fiber fixing device f for fixing the optical fibers 1-1a and 2-28; 4.4a is a stretching table that supports the optical fiber fixing devices 3 and 3a, respectively; 5 is a substrate; 6 is a fusion splice of optical fibers; This is a stretching part.

This device fixes optical fibers 1-1a and 2-2a to fiber fixing devices 3 and 3a, and fuses them together.

The stretched portion 6 is heated and fused, and then this fusion is performed.

While heating the stretching section 6, the stretching table 4 is moved in the direction of the arrow 7 to perform stretching. However, since this conventional device was configured to move the stretching table 4 using a gear mechanism,
There is a drawback that unreasonable tension is easily applied to the optical fiber during stretching, and clear stretching cannot be performed.

In addition, this conventional device has a linear polarization maintaining optical fiber of m
It was developed before the 'ia' and was originally for use with ordinary optical fibers, so it is similar to the one shown in Figure 6.
Even if an attempt is made to create an optical fiber coupler that maintains the IIl wave, it is difficult to modify the arrangement of the optical fibers to be fused so that the directions of their principal axes are aligned, and it is difficult to create an optical fiber coupler that maintains linear polarization. It was unsuitable for fabrication.

[Purpose of the invention]

Two inventions made in view of the above circumstances will be described below. The first invention is an optical fiber coupler that does not apply unreasonable tension to the optical fiber during drawing, and therefore can be drawn smoothly. Aiming at providing a manufacturing device, the second invention is further capable of detecting the orientation of the principal axes of linear polarization maintaining optical fibers, and arranging each optical fiber so that the principal axes of each optical fiber are aligned. It is an object of the present invention to provide an optical fiber coupler manufacturing apparatus that can be modified and easily manufactures a linear polarization-maintaining optical fiber coupler.

[Structure of the invention]

The first invention includes a pair of stretching device bases fixed on a substrate at an appropriate interval, and the stretching device being placed on these stretching device bases, and a gas ejected from these stretching device bases. A pair of stretching tables movably supported while floating above the stretching device base, and a pair of fiber fixing devices that are fixedly installed on these stretching tables and hold a plurality of optical fibers in a closely aligned state. and a weight that is suspended from the ends of the filament bodies connected to the pair of stretching tables and biases the pair of stretching tables in a direction to separate them from each other. The structure is such that a plurality of optical fibers are heated and fused together at a predetermined position and are stretched by the tension applied by the weight. a main axis detection device that optically detects the main axis direction of each optical fiber by immersing the optical fiber in a refractive index matching liquid; It has a configuration in which a main shaft adjustment device that rotates around the main shaft is added.

(Embodiment of the Invention) FIGS. 1 and 2 show an embodiment of an optical fiber coupler manufacturing apparatus incorporating the two inventions described above.

In these figures, 2l-21a, 22-228 are linear polarization maintaining optical fibers, 41-418 are optical fiber fixing devices, 42.428 are optical fiber horizontal position, vertical position adjustment parts, 43.43a, 43b, 43c is a main axis adjustment device for rotating the optical fiber around its central axis;
4 is a microscope, 45° 45a is a polarizing plate, 46.46a is a glass plate, 47 is a lighting device, 48 is an oxygen/propane flame burner, 49.49a is a stretching table, 410, 410a is a stretching device base, 411 is a substrate , 412, 412a are wires,
413.413a, 413b, 413c.

414.414a, 414b, 414c are pulleys, 4
15 is a weight, 416 is a weight stand, 417 is a polarizing plate 45.4
5a and a support stand for supporting the glass plate 46.468, 418.
4188 is a gas introduction pipe.

Hereinafter, the configuration of each part will be clarified and its operation will be explained according to the procedure for actually manufacturing a linear polarization-maintaining optical fiber coupler.

First, the linear polarization maintaining optical fibers 2l-21a, 22-22a are connected to the horizontal position/upper/lower ffi adjustment parts 42, 42a.
is grounded, and the positions of the linear polarization maintaining optical fibers are adjusted so that they are parallel and close to each other in the horizontal direction. FIG. 3 is a detailed illustration of the horizontal position/vertical position adjustment parts 42, 42a, and in this FIG. 3, 51.52. 53 is a clamping member 52 for adjusting the horizontal position;
55 and 56 are fiber holders for vertical position adjustment. The linear polarization maintaining optical fibers 2l-21a and 22-22a are held by the sandwiching member 51.5.
2, and by moving the clamping member 52 along the arrow 54 using the knob 53, the linear polarization-maintaining optical fibers 2l-21a and 22-22a are placed in parallel and close to each other between the clamping members 51 and 52. It is designed to be aligned.

In addition, the linear polarization maintaining optical fiber 2l-
By installing 21a and 22-22a, the vertical direction can be adjusted. Because of this structure, 2l-21
The two linear polarization maintaining optical fibers 22-22a are adjusted in position so that they are parallel and close to each other and lined up in the horizontal direction while being able to rotate freely. continue,
Enter the spindle arrangement process.

Fusion of optical fibers 2l-21a and 22-22a.

The stretched portion is sandwiched between two glass plates 46 and 46a, and is immersed in a matching liquid having approximately the same refractive index as the cladding portion of the optical fiber. The light from the illumination light source 47 is turned into linearly polarized light by a polarizing plate 45a, and after crossing the optical fiber, it is converted into linearly polarized light by another polarizing plate 4 that is orthogonal to the polarization of the polarizing plate 45a.
Pass 5.

When polarized light crosses an optical fiber, the plane of polarization rotates due to the photoelastic effect of the stress applying part, and by observing it with the microscope 44, the position of the stress applying part can be detected as a difference in brightness, and the principal axis direction can be detected. Can be detected.

If this detection method is adopted in which the optical fiber is immersed in a matching liquid, the refractive index of the stress-applying part matches the refractive index of the cladding part with high precision, so the position of the stress-applying part can be determined by ordinary microscopic observation. Even if it cannot be detected, the direction of the main axis can be detected easily and satisfactorily.

In this way, the detection method of immersing in a matching liquid was adopted because the optical fibers 2l-21a and 22-22a have linear polarization maintaining properties in which the refractive index of the stress applying part is matched to the refractive index of the cladding part. This is simply because optical fiber is used.

An optical fiber coupler that uses a normal linear polarization maintaining optical fiber has an insertion loss of about 3 dB, but a linear polarization maintaining optical fiber that matches the refractive index of the stress applying part to the refractive index of the cladding part is used. Insertion loss can be reduced to 1d by using
Can be made below B. In addition, as described above, as a principal axis detection method when using an optical fiber whose refractive index has been matched in this way, a linear polarization-maintaining optical fiber is immersed in a refractive index matching liquid, and the plane is measured using polarized light. The best method is to observe the image due to the photoelastic effect from the
8-192174 (Fiber type optical coupler and method for manufacturing the same).

Next, after detecting the main axis direction, Fig. 2 43.43a,
The optical fiber 2 is adjusted by the main axis adjustment devices 43b and 43c.
1-21a and 22-22a are rotated to adjust to the desired alignment in the main axis direction. Main shaft adjustment device 143.43a
, 43b, and 43c have a structure that allows the optical fiber to be fixed at the center of rotation.As for the optical fiber 21-218, by turning 43 and 43c in the same direction and the same angle, the optical fiber 21-218 is free from twisting or slack. Rotation operations can be performed without causing any turbulence. Also,
The rotation angle can also be measured using a rotation angle measurement of 43.430. 43a for optical fiber 22-22a
, 43b perform similar operations.

As a result, the linear polarization-maintaining optical fibers 2l-21a and 22-22a can be arranged in the desired principal axis direction.

Subsequently, the optical fiber 2l-21a is attached to the support stand 41.41a.
, 22-22a are fixed, the support base 417 is removed, and the glass plates 46, 4681 and polarizing plate 45a are removed. From the optical fiber end 21 or 22, the light having the wavelength used by the optical fiber coupler is connected to the optical fiber 2l-21a or 22-2.
2a, the light output is detected from the output ends 21a and 22a, and is monitored. Next comes the fusing process. oxygen·
The propane flame burner 48 heats a portion of the two dark optical fibers on the support base 41 and 418, and the fusion is performed while observing the fusion state using the microscope 1144.

Next, the stretching process begins. Introducing gas into the stretching device base 410.4108 through the gas introduction pipe 418.418a,
Gas is ejected toward the stretching table 49, 49a. the result,
The stretching table 49.degree. 49a floats due to the gas pressure, and becomes in a state where it can be moved clearly and freely on the stretching device base. The stretching table 49.498 is connected to the weight 415 through a wire 412.412a. Wires 412.412a are connected to pulleys 413.413a, 413b, 413c, 41
4.414a, 414b, 414c, weight 41
Bring it up to 5. As a result, the stretching tables 49, 49a are subjected to a force in the direction of separating them from each other. Under normal conditions, the stretching table 49.degree. 49a remains stationary due to the tension of the optical fiber. In this state, the fused portion is heated using an oxygen-propane flame burner 48.
When heated by
a are moved away from each other by the weight 415, and the fused portion of the optical fiber is smoothly stretched without being subjected to excessive force. As a result, the shape of the tapered portion of the extended portion of the optical fiber coupler is smooth, and an optical fiber coupler with no body loss can be realized. Furthermore, by changing the weight of the weight 415, the stretching speed can be adjusted, the stretching speed can be selected in accordance with the diameter and strength of the optical fiber, and the shape of the taper of the stretching section can also be adjusted.

The light output from the optical fiber output ends 21a and 22a is monitored, and when the desired optical coupling ratio is reached, the heating is stopped and the stretching is stopped. This completes the fabrication of the optical fiber coupler.

In addition, in the embodiment, a weight 415 was used to move the stretching table 49,498 during stretching, but by fixing the stretching table 49 and tilting the substrate 411, the stretching table 49a floated by gas pressure can be moved. Stretching can be performed. In this case, the stretching speed can be adjusted by adjusting the inclination angle of the substrate 411.

Furthermore, although the above embodiment is an example of fabricating an optical fiber coupler using two optical fibers, the present invention can also be applied to fabricating an optical fiber coupler using a plurality of optical fibers.

In addition to the linear polarization maintaining optical fiber described in this example, an optical fiber 21-1 having a stress applying structure as shown in FIG. 4(a) or an elliptical fiber as shown in FIG. 4(b) may be used. Of course, the manufacturing apparatus of the present invention can also be applied to manufacturing an optical fiber coupler using the core fiber 21''.

As explained above, the manufacturing apparatus according to the first invention of the present application has a configuration in which the stretching table is made movable by being floated by gas, and the stretching table is moved by a weight suspended from the stretching table via a filament. Therefore, the tension applied to the stretched optical fiber is determined by the weight of the weight and remains constant without fluctuation. Therefore, by simply setting the weight of the weight appropriately, it is possible to prevent excessive tension from being applied to the optical fiber during stretching, and it is now possible to achieve smooth stretching and adjustment of the stretching speed at the same time. .

Further, the manufacturing apparatus according to the second invention is the equipment according to the first invention.
A main axis detection device that detects the main axis direction of the optical fiber to be further fused and stretched, and a main axis that supports both ends of each optical fiber and rotates each optical fiber around its central axis as necessary. Since the configuration is equipped with an adjustment device, when linear polarization maintaining optical fibers are fused together, it is possible to easily and accurately align the principal axes of each optical fiber. As a result, it has become possible to easily produce a polarization-maintaining optical fiber coupler with low loss and low crosstalk without destroying the linearly polarized state.

[Brief explanation of the drawing]

FIG. 1 is a top view of an embodiment of the present invention, FIG. 2 is a side view of the same, FIG. 3 is an enlarged view of the main parts in FIG. 2, and FIGS.
b)' is an explanatory diagram of an optical fiber that can be used in the device of the present invention, Fig. 5 is an explanatory diagram of a conventional optical fiber coupler, and Fig. 6 is an explanatory diagram of an optical fiber coupler using a linear polarization-maintaining optical fiber. Structure explanatory diagram, Figure 7 (a) (b) (c)
are explanatory diagrams of the main axis arrangement that does not destroy the polarization state, respectively.
FIG. 8 is an explanatory diagram of a conventional optical fiber coupler manufacturing apparatus. 2l-21a, 22-22a...Linear polarization maintaining optical fiber, 23...Fusion and stretching part, 24a
... core part, 24b ... clad part,
25...Response imparting portion, 26a, 26b...
...Linear polarization maintaining optical fiber, 29,210...
...Output electric ring polarization, 31...Arrow indicating fusion operation, 41.41a...Optical fiber fixing device,
42.42a...Optical fiber horizontal position. Vertical position adjustment section, 43.43a, 43b, 43c.
...Spindle adjustment device, 44 ...Microscope, 4
5.45a...Polarizing plate, 46.46a...
...Glass plate, 47...Lighting equipment, 48...
...Oxygen/propane flame burner, 49.49a...
...Stretching table, 410.410a...Stretching device base, 411...Substrate, 412, 412a...
...Wire, 413, 413a, 413b. 413c, 414.414a, 414b, 414
C... Liquor wheel, 415... Weight, 416.
... Weight stand, 417 ... Support plate, 41
8.418a... Gas introduction pipe, 51.52...
... Clipping member, 53 ... Knob, 55.5
6...Fiber holder. Applicant Nippon Telegraph and Telephone Public Corporation Figure 4 Figure 5 Figure 7 Figure 8

Claims (1)

[Claims] 1. A pair of stretching device bases fixed on a substrate with an appropriate distance of lI1wA, and a stretching device placed on these stretching device bases and ejected from these stretching device bases. A pair of stretching tables movably supported while floating from the stretching device base by gas, and a pair of fibers fixedly installed on these stretching tables to grip a plurality of optical fibers in a closely aligned state. The pair of fiber fixing devices includes a fixing device and a weight that is suspended from an end of a filament connected to the pair of stretching tables and biases the pair of stretching tables in a direction away from each other. An optical fiber coupler manufacturing apparatus characterized in that a plurality of optical fibers are heated and fused to each other at a predetermined position between them, and are stretched by tension applied by the weight to form an optical fiber coupler. 2. A pair of stretching device bases fixed on the substrate at appropriate intervals, and the stretching device bases are placed on these stretching device bases, and the stretching device bases are stretched by the gas ejected from these stretching device bases. a pair of stretching tables movably supported in a floating state; a pair of fiber fixing devices fixedly installed on these stretching tables and gripping a plurality of optical fibers in a closely aligned state; a weight that is suspended from an end of a filament body connected to the stretching table and biases the pair of stretching tables in a direction away from each other, at a predetermined position between the pair of fiber fixing devices, An optical fiber coupler manufacturing apparatus that forms an optical fiber coupler by heating and fusing a plurality of optical fibers together and stretching them by tension applied by the weight, wherein the refractive index of the plurality of optical fibers is matched at the predetermined position. A main axis detection device that optically detects the main axis direction of each optical fiber by immersing it in a liquid, and a main axis adjustment device that supports both ends of each optical fiber and rotates each optical fiber around its central axis as necessary. An optical fiber coupler manufacturing device comprising: