JPS6015608A - Manufacturing method of optical star coupler - Google Patents

Abstract

PURPOSE:To improve the accuracy and reproducibility of the shape in a tapered part by twisting a hollow glass tube contg. an optical fiber bundle to form a glass rod during heating and heating and stretching the glass rod. CONSTITUTION:Headstocks 3, 3' are rotated in arrow 11, 11' directions by motors 17, 17' to apply preliminarily a tension Pm on a twisted glass rod in the stage of stretching said rod and forming a tapered part 12. The Pm is the sum of the tension Pa for moving the headstocks and the tension Pl when the rod 9 is softened by heating and is stretched. The Pe is as large as >=several 100g and the headstocks 3, 3' do not move while the rod 9 is not heated. When the rod is rotated in the direction of an arrow 10 and is heated by a burner 5, the headstocks 3, 3' move by L and are stopped by switches 20, 20'. The motors 17, 17' are stopped by switches 19, 19' as well. The tension during stretching is measured with a tension analyzer 14 and the value thereof is compared with a reference tension value. A signal is generated in the output from a circuit 16 according to the result thereof and when the measured value is lower than the reference value, switches 22, 23 are turned off to stop supplying gaseous H2 and O2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method of manufacturing an optical star coupler that distributes a light beam propagating through an optical fiber to a plurality of optical fibers.

[Background of the invention]

BACKGROUND OF THE INVENTION With the rapid advancement of optical fiber transmission technology, research and development of optical data links that use optical fibers for data transmission between computers and between computers and one terminal are being actively conducted. In configuring this optical data link, an optical star coupler is an essential device that can mix optical signals from multiple input optical fibers and distribute them evenly and with low loss to multiple output optical fibers. It is.

The present inventor first proposed a structure and manufacturing method for an optical star coupler that has low insertion loss and distribution variation, is easy to manufacture, and is suitable for mass production, by inserting an optical fiber bundle into a hollow glass tube and heating the hollow glass tube. While adding a twist, the hollow glass tube and the optical fiber bundle are fused together to form a solid glass rod, and the twisted glass rod is stretched to form a tapered part, or while adding the above twist, We have discovered and proposed an optical star coupler with a completely new structure in which it is stretched to form a tapered part. An example of a method for manufacturing the optical star coupler is shown in FIG. 1(a)=(b)+('). First, in (a), the optical fiber bundle 1 is inserted into the hollow glass tube 2, and the chuck part 4 of the headstock 3.3' of the glass lathe 6 is
．． Chuck to 4'. Heat sources 5 are placed at eight points to heat the hollow glass tube, and when it begins to soften, the heat sources 5 are turned on while rotating the chuck portion 4' of the headstock 3' in the radial direction of the hollow glass tube, that is, in the direction of arrow 7. Move the hollow glass tube in the direction of arrow 8 along the axial direction, and when it reaches point E, chuck part 4
' and the heating source 5 is turned off to obtain the structure shown in (b).

The part 9 is a solid twisted glass rond in which an optical fiber and a hollow glass tube are fused together.

Next, as shown in (C), the chuck parts 4, 4' of the headstocks 3, 3/ are rotated in the direction of arrow 10, the heat source 5 is placed approximately in the center of the part 9, and the part 9 is After heating and starting to soften, move the headstocks 3 and 3' in the direction of arrows 11 and 11'.
Alternatively, the optical star coupler may be manufactured by moving only 3 in the direction of arrow 11 or only moving 3' in the direction of arrow 11' and stretching 9 parts to obtain tapered part 12.

However, in the process (C), when stretching is performed using an oxyhydrogen burner (or a burner of city gas, propane gas, etc.) as the heat source 5, there are certain issues such as the timing of stretching, the timing of stopping the burner gas, etc. The problem was that delicate adjustments and control were difficult.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing an optical star coupler with good controllability, that is, a method for manufacturing the shape (outer diameter, length) of the tapered portion 12 with high precision and high reproducibility in the process shown in FIG. 1 (CC). It is about providing.

[Summary of the invention]

The present invention involves heating and twisting a hollow glass tube into which an optical fiber bundle is inserted, fusing the hollow glass tube and the optical fiber bundle to form a solid glass rod, and creating a twisted glass rod portion. When further heating and stretching the glass tube to make it into a tapered shape, both ends of the glass tube are stretched to the desired tension, and when the glass rod portion is heated and softened, the glass rod portion is automatically stretched to the desired length. This is a method for manufacturing an optical star coupler, in which the heating source is controlled according to the stretching state. By using this method, the stretching length and the heating source during stretching can be controlled, so that the shape of the tapered portion can be manufactured with high precision and high reproducibility.

[Embodiments of the invention]

FIG. 2 shows a schematic diagram of the method for manufacturing the optical star coupler of the present invention. This corresponds to the process shown in FIG. 1(C). That is, the twisted glass rod portion 9 is stretched to form a desired tapered portion 12 (Fig. 1(C)
)reference. ).

In Figure 2, the same numbers as in Figure 1 have the same effect.
It has a function. Reference numeral 13 denotes a tension detection unit, which consists of guide rollers A and C and a tension detection roller B.
The accumulated displacement is converted into a voltage value VI proportional to the tension in the tension analyzer 14, and is applied to one input terminal of the control circuit 16. Reference numeral 15 denotes a reference voltage (VW) generator corresponding to a reference tension value P, which is applied to the other input terminal of the control circuit 16. 17 and 17'
is a motor that has the function of pulling in the directions of arrows 11 and 11' with a desired tension P, ..., and a desired speed V, 18.1
8' is a drive circuit for these motors. 20.20' is a beam set switch which operates to stop the movement of the headstock 3.3' when the headstock 3,3' moves by a length L in the direction of arrow 11°11'.

21.21' is a signal generating circuit for turning off the switch 19.19' when the reset switch 20.20' is operated. 22゜23 is H2 gas, 0
This is a switch for supplying (on state) or stopping the supply (off state) of the two gases to the burner 5, and is controlled on and off by the output signal of the control circuit 16. That is, 22 and 23 are normally in an on state, and when a signal occurs at the output of the control circuit 16, 22 and 23 are switched to an off state. Reference numerals 24 and 25 are pulp adjusting devices for adjusting the H2 gas flow rate and the 02 gas flow rate, and the gas flow rates are controlled by voltage. Next, the operation shown in FIG. 2 will be explained. An air bearing moving mechanism is used to move the headstocks 3 and 3' in the directions of arrows 11° and 11', and the coefficient of distortion caused by these movements is made extremely small. First, the motors 17, 17' apply tension P to the headstocks 3, 3' in the direction of arrows 11 and 11'.

Add. This P is the sum of the tension P required to move the headstock (3 or 3') and the tension PJ when the glass rod portion 9 is softened and stretched by heating. FIG. 3 shows the tensile tension pi at the time of stretching when the glass rod part 9 is heated (temperature T) to soften and stretch;
This is an example of an experimentally determined relationship between the tensile speed v during stretching.

However, the outer diameter of the glass rod portion 9 is approximately 2.5111J, and the outer diameter of the glass rod of the extended portion 12 is approximately 0.3 ttrm. In this way, when the glass rod portion 9 is softened, its tensile tension pz is several tens of grams. Therefore, Pa is also set to a value of several tens of grams. When the glass rod part 9 is not heated, PJ is several 10.
Since this is an extremely large value of 0 g or more, the headstocks 3, 3' do not move in the direction of arrows 11 and 11' in this state. Next, the glass rod portion 9 is rotated in the direction of the arrow 10, and the oxyhydrogen burner 5 is ignited to heat the glass rod portion 9. As time passes, the glass rod portion 9 begins to gradually soften, and when Pg +Pa becomes smaller than P, the main axis 83m
3' moves a distance in the direction of arrow 11.11' and is stopped by reset switch 20.20'. The motors 17 and 17' are also driven by switches 19 and 19'.
is stopped by turning off, and the desired taper portion 12 is obtained. The heavy equipment here is the oxyhydrogen burner 5, the motor 17,
If the ignition is continued after 17' is stopped, the extended taper part 1
2 is deformed or broken by heat. The same thing happens even if the material is heated to an extremely low tension value.

Therefore, the tension during stretching is measured by the tension analyzer 14, and the measured value is compared with the reference tension value P, and a signal is generated at the output of the control circuit 16, and the measured value is P.
If it becomes lower than 2, the above signal causes switch 22.
23 to stop the supply of H2,02 gas. Alternatively, it may be fed back to the pulp adjusting device 24, 25 for gas flow rate adjustment (26, 26
route shown by the dotted line). Alternatively, the switches 22 and 23 may be turned off using the signal from the signal generation circuit 21 (2
8).

Additionally, we have experimentally confirmed that the tension tends to decrease as the distance traveled during stretching increases, that is, as the stretching diameter decreases. Rotational speed, i.e. headstock 3.3'
may be controlled by the output signal of the control circuit 16. This is route 27.2
As indicated at 7', the output signal of the control circuit 16 is fed back to the motor drive circuit 18, 18'. This is control to gradually increase vm with the start of stretching.

In the above embodiment, the heating source is controlled by detecting the tension during stretching, but instead of the tension, the heating temperature of the glass rod portion may be detected to control the heating source. In that case, the tension sensor simply replaces the temperature sensor. Further, in the above embodiment, the headstock 3.3' is moved by two motors 17.degree. 17', but a mechanism capable of mechanically transmitting the movement using one motor may also be used. Further, instead of the oxyhydrogen burner, a carbon dioxide laser, a high frequency induction heating furnace, etc. may be used. Furthermore, if the optical fiber is not quartz-based glass but multi-component glass, a city gas burner or a propane gas burner may be used. One or more burners,
Furthermore, it may be ring-shaped. Further, L can be set arbitrarily.

Furthermore, instead of turning off the switches 22 and 23, a shutter for preventing flames may be used above the burner 5, and the shutter may be opened and closed by the output signal of the control circuit 16.

〔Effect of the invention〕

The present invention has the following effects.

+11 The shape (outer diameter, length) of the tapered part, which is the heart of the optical star coupler of the present invention, can be manufactured with high precision and reproducibility, resulting in an optical star coupler with low loss and low distribution variation. can.

(2) Since the heating source can be automatically controlled according to the stretching state, productivity can be increased.

Furthermore, since the tension during stretching is kept almost constant, residual stress is small and mechanical strength is excellent, and optical loss can also be reduced.

[Brief explanation of drawings]

FIG. 1 shows an example of the method of manufacturing an optical star coupler previously proposed by the present inventor, FIG. 2 shows an example of the method of manufacturing an optical star coupler of the present invention, and FIG. 3 shows an example of the method of manufacturing an optical star coupler of the present invention. This is an example of experimental results regarding the relationship between the temperature of the obtained glass rond and the tensile force during stretching.

Claims (1)

[Claims] 1. While heating the hollow glass tube with the optical fiber bundle inserted, add a twist to fuse the hollow glass tube and the optical fiber bundle to form a solid glass rod, and further heat the twisted glass rod part. , when stretching the glass tube to form a tapered shape, both ends of the glass tube are stretched with a desired tension,
A method for manufacturing an optical star coupler, characterized in that the heating source is controlled depending on the stretching state of the optical star coupler.