JPS60251154A - Cladding process of optical fiber - Google Patents

Abstract

PURPOSE:To obtain a uniform clad layer having high strength by imparting a velocity component directing toward a direction of rotation around an axis of a die nozzle as the axis of the rotation to the fluid in the stage of applying the fluid to the optical fiber in an applicator provided with a nipple and a die. CONSTITUTION:Optical fiber 9 immediately after wire drawing is introduced into an applicator 11 provided with a nipple 12 and a die 13 provided with a nozzle arranged coaxially with said nipple 12. The fluid 10 for the cladding material is forced to between the nipple and the die and/or to between two dies 13, applying the fluid 10 to the optical fiber 9 in the die nozzle to clad the optical fiber 9. In this stage, the nipple 12 and/or the die 13 is (are) rotated by rotating gears 14, 15. Also, a helical or concentric buffer plate 16 is provided to the passage of the fluid 10, and a velocity component directing toward the direction of rotation around a die nozzle axis as an axis of the rotation is imparted to the fluid contained between the nipple and the die and/or in the die nozzle.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of coating an optical fiber with high strength and a uniform coating layer.

[Prior art]

Glass fiber for optical communication (hereinafter abbreviated as optical fiber) usually has a small outer diameter on the order of 100 μm.
It is an extremely fragile material.

Therefore, if used as is, friction during the manufacturing process or cable-making process will cause surface scratches, and the optical fiber will break at an extremely low strength compared to its original strength (approximately 7 mm). . That is, a highly reliable transmission line cannot be formed. For this reason, in order to protect the optical fiber surface and maintain its initial strength, the surface of the optical fiber is coated with plastic immediately after spinning.Of course, in this case, the plastic coating is performed. Optical fibers must not come into contact with solid objects before being treated.

Both thermosetting resins and thermoplastic resins can be used as the optical fiber coating material. Thermosetting resins are applied to Phino (in an uncured liquid state) and then cured by means such as heating or light irradiation.Also, thermoplastic resins are also applied to Phyno in an uncured liquid state and cured by means such as heating or light irradiation. (Applied to.

Currently, as a method for coating optical fibers with these resins, an open type die is generally used, and a pressure type die in which the die is completely semi-closed and the coating material is press-fitted has also been proposed.

In this case, as mentioned above, the optical fiber (does not come in contact with these dies). This optical fiber and the dies (
Several methods have been proposed to prevent contact (particularly with the nozzle part). For open type dies, there is a method in which the dies are split in half, the nozzle part of one die is aligned with the optical fiber running position, and then the other die is completely bonded together to form an integrated die. It is true that this method prevents the optical fiber from coming into contact with the die, but since the alignment of the die nozzle is done visually, slight positional deviations occur, resulting in uneven thickness of the coating layer, and it is difficult to integrate the die. Since the liquid resin is injected later, there is a risk that the optical fiber may break during the time until the liquid resin is injected, and this process requires a great deal of skill. In addition, as a common method for open-type dies and pressure-type dies, a method has been proposed in which the die is levitated by gas pressure and the die is self-aligned by the viscous resistance that acts between the optical fiber and the material to be welded within the die nozzle. has been done. However, this method has problems such as the die being tilted due to uneven weight of the die and the coating material filled in the die, and is not practical. Furthermore,
A method has been proposed in which uneven thickness of the coating layer is detected by irradiating light onto the coating layer immediately after coating and monitoring the forward scattered light pattern, thereby correcting the position of the die. This method certainly has the advantage of preventing uneven thickness, that is, contact between the optical fiber and the die nozzle, with high precision, but not only is the device configuration complicated, but it also requires the use of non-light-transparent coating materials, such as colored coating materials. It has the disadvantage that it cannot be applied to resins and the like.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned current situation, and its purpose is to provide a coated light beam with high strength and less uneven thickness without adding any special equipment or requiring special skill. An object of the present invention is to provide a method for manufacturing a fiber.

[Structure of the invention]

To summarize the present invention, the present invention relates to a method for coating an optical fiber, and the present invention relates to a method for coating an optical fiber, which includes a nipple having a through hole having an inner diameter larger than the outer diameter of the optical fiber immediately after drawing; between the nipple and the die and/or between the two dies of an applicator comprising a nipple and one or two dies having a nozzle having an inner diameter larger than the outer diameter of the optical fiber and arranged coaxially with the nipple; In an optical fiber coating method in which a fluid is pressurized between the nipple and the die and the fluid is applied to the optical fiber within the die nozzle, the fluid located between the nipple and the die, between the dies and/or within the die nozzle,
It is characterized in that a velocity component in a rotational direction about the axis of the die nozzle is applied.

The present invention is based on detailed study results regarding the relationship between the flow of the coating material near the entrance of the die nozzle and the center force acting on the optical fiber.
By forcibly applying a velocity component in the direction of rotation around the axis of the die nozzle, the positional deviation between the center of the optical fiber and the axis of the die nozzle is reduced and the distance is kept constant. .

The present invention will be described in detail below based on the results of a model experiment regarding the cardiac force acting on an optical fiber. Figures 1 (a) and (1)) are a sketch (a) and a cross-sectional view (b) of the experimental system when the fluid is not rotated, respectively, where 1 is a fluid supply pipe, 2 is a closed container, and 3 is a floating 4 is a support of the floating plate 3, 5 is a stainless steel wire having an outer diameter of α1, 6 is a nozzle, 7 is a fluid flow direction (streamline), and 8 is a bottom surface of a closed container. Here, 5
The stainless steel wires were attached to the nozzle center position of the floating plate 3 and at a position 51 points away from the nozzle center position, and hung down to the nozzle outlet. The inner diameter of the nozzle 6 was 10 mm.

Silicone oil with a viscosity of 1 poise was pressurized into the apparatus shown in FIG. Silicone oil was injected at a rate of ~50 t/min, but although the stainless steel wire no longer sags as the silicone oil flowed, the position (radial direction) of the stainless steel wire at the nozzle inlet hardly changed, and it The displacement of stainless steel wires attached at separate locations (when silicone oil is not press-fitted, they contact the nozzle inner wall at the nozzle inlet) toward the center of the nozzle is a5-
It was below. From this result, it can be seen that if there is no velocity component in the rotational direction in the flow of the coating material, the optical 7-eyeper is not subjected to cardiac force. On the other hand, when the bottom surface 8 of the closed container was rotated by a motor, it was observed that the stainless steel wire moved toward the center of the nozzle as the rotation speed increased. This amount of movement is determined at a rotational speed of 100 rpm (silicone oil flow rate of 21 rpm).
7 minutes) and approximately 4■.

Furthermore, when the baffle plate shown in FIG. 2 was inserted between the floating plate 3 shown in FIG. 1 and the bottom surface 8 of the closed container, the stainless steel wire was observed to move toward the center of the nozzle. The amount of movement in this case was 3 to 4 at a silicone oil flow rate of 217 minutes.

Furthermore, when silicone oil was press-fitted along the circumferential direction of the sealed container using the vortex type device shown in FIG. 3, it was also observed that the stainless steel wire moved toward the center of the nozzle.

The present invention has been made based on the above study results, and
Its feature is that it imparts a speed component in the rotational direction to the coating material, and there are no restrictions on the speed or the resin used.

In the present invention, in order to provide a speed component in the rotational direction,
said nipple and/or said die by rotating said nipple and said die, said nipple-die made by providing a spiral or concentric baffle plate between said nipple and said die and/or said two dies; The flow path of the fluid immediately before reaching the space between the nipple and the die is spirally or concentrically coaxial with the nipple and/or the die. There are methods such as press-fitting two different layers of fluid in a circular manner. Further, the fluid may be a thermoplastic resin heated above its melting temperature and/or an uncured thermosetting resin in a liquid state.

〔Example〕

The present invention will be explained in more detail below using Examples and Comparative Examples, but the present invention is not limited to these Examples. In addition,
4 to 6 are schematic diagrams showing the die/nipple structure of the applicator used in the optical fiber coating experiment. In each figure, 9 is an optical fiber, 10 is a coating material, 11 is a crosshead (applicator), 12ii is a nipple, 1
3 is a die, 14 is a nipple rotation gear, 15 is a die rotation gear, 21 is a coating material (inner layer), 17 is a coating material (outer layer), 16, 19, 20 is a baffle plate mounting position, and 1
8 means a partition plate.

The experimental results are also shown in Table 1 below. Here, the outer diameter of the optical fiber was 125 μm, and the baffle plates in Table 1 were the same as those in FIG. 2.

In addition, eccentricity in the case of using a thermosetting resin (S/Recone) was measured after the coated optical fiber immediately after coating was heated in a heating furnace to cure the resin. Furthermore, Figure 4~
In FIG. 6, in order to give the coating material a velocity component in the rotational direction in advance, an experiment was also conducted in which the material injection hole in the crosshead 11 was supplied in a direction perpendicular to the die nipple axis.

Examples 1 to 14 and Comparative Examples 1 to 7 Optical fibers were coated under the conditions shown in Table 1 below. Examples 1 to 5 are examples in which a baffle plate is attached to the position 16 of the applicator shown in FIG.
In the applicator shown in the figure, an example in which rotation is applied to the nipple or the die, Example 10 is an example in which the coating material is press-fitted in the die circumferential direction, and Examples 11 to 14 are examples in which the applicator shown in FIG. In the example in which the position of the plate was changed and the comparative example, the apparatus shown in FIGS. 4 to 6 was used, but none of the measures in each of the above embodiments were taken.

From the results in Table 1, it can be seen that according to the present invention, a coated optical fiber with extremely little eccentricity and high strength can be easily manufactured.

To further elaborate on the results in Table 1, when a baffle plate is inserted between the nipple and the die, the eccentricity decreases as the coating speed increases. On the other hand, when the nipple or die is rotated, the eccentricity decreases with rotational speed, but as the coating speed increases, eccentricity slightly increases. Therefore, inserting a baffle plate is the best method for high-speed coating), in which case it can be said that the optical fiber is automatically held at the center of the coating layer. Furthermore, the eccentricity of the coating light 7 eyer shown in the comparative example was randomly distributed in the longitudinal direction of the fiber and was not located at a fixed position within the coating layer. On the other hand, in the coated optical fiber shown in the example, the eccentricity was extremely uniform in the longitudinal direction of the optical fiber. This result is presumed to be due to the fact that the optical fiber rotates spirally around the center of the coating layer due to the velocity component in the circumferential direction of the coating material. However, according to the present invention, the coating structure is extremely stable in the longitudinal direction ( It is clear that a coated optical fiber with eccentricity) can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, coated optical fibers that are extremely stable in the longitudinal direction and with little eccentricity can be manufactured at high speed without requiring any special additional equipment or skill. Moreover, it has the advantage of being able to reduce the price.

[Brief explanation of the drawing]

Figures 1 to 3 are schematic diagrams of a device for observing cardiac force, a baffle plate, and a eddy current device used in the model experiment of optical fiber coating, and Figures 4 to 6 are diagrams of actual optical fibers. FIG. 3 is a schematic diagram showing the die/nipple structure of the applicator used in the coating experiment. 1: Fluid supply pipe, 2: Sealed container, 3: Floating plate, 4: Support column,
5 stainless steel wire, 6: nozzle, 7: streamline, 8: bottom of sealed container, 9: optical fiber, 10: coating material, 11: crosshead (applicator), 12: nipple, 13: die, 14: nipple Rotation gear, 15: Die rotation gear, 21: Covering material (inner layer), 17: Covering material (outer layer), 16.19.20: Baffle plate mounting position, 18: Partition plate patent applicant Nippon Telegraph and Telephone Public Corporation representative Hirodo Nakamoto Akito Inoue Katsura Yoshimine, λ (No. 1 (Mu)' Figure 2 Figure 1 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A nipple having a through hole having an inner diameter larger than the outer diameter of the optical fiber in an m-drawn straight edge optical fiber, and an optical fiber disposed coaxially with the nipple. The body of an applicator is equipped with one or two dies each having a nozzle with an inner diameter larger than the outer diameter of the applicator. In the optical fiber coating method of applying the fluid to the optical fiber, the fluid located between the nipple and the die, between the dice, and/or within the die nozzle is applied in a rotational direction about the axis of the die nozzle. 1. A method of coating optical 7-aipa characterized by imparting a velocity component of . 2. The method of coating an optical fiber according to claim 1, wherein the coating is performed by rotating the nipple and/or the die. 5. The method for coating an optical fiber according to claim 1, wherein the coating is performed by providing a spiral or concentric baffle plate between the nipple and the die and/or between the two dies. 4. The provision is made by making the fluid flow path between the nipple and the die and/or between the two dies into a spiral shape or a concentric circle coaxial with the nipple and/or the skeleton die. A method for coating an optical fiber according to claim 1. S. The coating of the optical fiber according to any one of claims 1 to 4, wherein the coating is applied by concentrically pressurizing two layers of the same or different fluids between the nipple and the die. Method. & The optical fiber according to any one of claims 1 to 5, wherein the fluid is a thermoplastic resin heated to a melting temperature or higher and/or an uncured thermosetting resin in a liquid state. coating method.