JPS6060952A - Manufacture of coated optical fiber - Google Patents

Abstract

PURPOSE:To obtain a product maintaining its satisfactory and stable transmission characteristics for a long term without requiring any special coating means by bringing the primary coating layer of a coated optical fiber into contact with water, removing harmful gases, and forming a secondary coating layer. CONSTITUTION:A coated optical fiber 3 having a coating layer 2 of silicone resin is introduced into a heating furnace 12, where it is heated. At this time, atmospheric gas contg. water is fed to the furnace 12 to bring the layer 2 into contact with water unless moisture is absorbed in the layer 2 by contact with water. Si-H groups in the layer 2 are converted into stable Si-O-Si bonds through Si-OH groups, so the problem of OH groups is solved. The fiber 3 is then introduced into a harmful gas removing vessel 13, and the vessel 13 is evacuated to remove harmful gases such as H2 from the layer 2. A coating layer 4 of nylon or the like is formed around the layer 2 with a coating means 15 provided with an extrusion molding machine 14A to obtain a product 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a coated optical fiber that can maintain good and stable transmission characteristics over a long period of time.

Optical fibers for communications are coated immediately after they are spun.

This coated optical fiber may be made into a cable as it is and used as an optical path, but normally, following the first coating layer formed immediately after spinning, a second coating layer for reinforcement is applied to the first coating layer. formed on top.

The first coating layer is silicone resin, polyurethane resin,
Epoxy resins, acrylic resins, polyvinylidene fluoride resins, etc. are used, and these become films with predetermined physical properties by heat curing, photocuring, etc. after application.

The second coating layer is formed by extrusion molding a thermoplastic resin such as nylon, polyethylene, or PVC, but the above-mentioned curable resin may also be used.

By the way, when coating at this time, care must be taken not to cause dust or scratches on the first coating layer, or to cause moisture absorption or gas absorption, between after the first coating and before the second coating is applied. .

For example, if the first coating layer absorbs moisture, this may deteriorate the mechanical properties of the optical fiber in later steps or cause the first coating layer to absorb moisture.
or alter it.

In addition, when silicone resin is used as the covering material, H2 is generated according to the following equation, which is diffused into the optical fiber and O
This results in the generation of H groups, resulting in an increase in transmission loss.

~S i H+H20+H3i~→~Si 'OSi+
Hz...(2゜In the conventional technology, efforts have been made to store the coated optical fiber after the first coating in a clean environment until the second coating layer is formed, but this alone is insufficient. Therefore, the coated optical fiber has been cleaned in a cleaning process before the second coating process, but this method has not achieved sufficient results as a measure to ensure the high quality and high characteristics of the coated optical fiber. .

In particular, if formula 1 or 2 above is allowed to occur over a long period of time,
Embrittlement of the optical fiber surface due to moisture also occurs.

The object of the present invention is to make it possible to obtain a coated optical fiber that can maintain good and stable transmission characteristics over a long period of time by applying special innovations to the coating means of the optical fiber when manufacturing a coated optical fiber. It is.

The feature of the present invention is that after the coating layer of the coated optical fiber is brought into contact reaction with water, harmful gas components are removed from the existing coating layer and a further coating layer is formed around the outer periphery of the coating layer. There is a particular thing.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a coated optical fiber 3 in which a coating layer 2 is formed on the outer periphery of the optical fiber 1, and FIG. 2 shows a covered optical fiber 5 in which a coating layer 4 is further formed on the outer periphery of the coated optical fiber 3. show.

In the case of the above-mentioned coated optical fiber 3, the optical fiber 1 immediately after spinning
By passing it through a die-type coating machine and a curing furnace,
A coating layer 2 can be formed on its outer periphery, and the optical fiber 1 is made of a quartz-based material having a core and a cladding, and the coating layer 2 is made of any of the various resins listed as the MU of the first coating layer.

The coating layer 2 formed on the outer periphery of the optical fiber 1 has the function of either a primary coat or a buffer coat, or both, and the coating layer 2 is either a primary coat or a buffer coat. In some cases, the other coating layer may be formed separately, and the number of coating layers around the outer periphery of the optical fiber may be further increased until the coating layer 4 is formed.

The buffer coating layer preferably has a Young's modulus of 10 Ky/- or less, preferably 2 Ky/- or less, in order to obtain lateral pressure resistance.

In the case of a coated optical fiber 5 obtained by further forming a coating layer 4 on the outer periphery of the coating layer 2, the coating layer 4 is made of any one of the various resins listed as the coating phase of the second coating layer. , the coating layer 4 performs reinforcing and protective functions.

In the embodiment of the present invention described below, a coating layer 2 is previously formed on the outer periphery of an optical fiber 1, and a coating layer 4 is formed on the outer periphery of the thus obtained coated optical fiber 3.

That is, although the process of forming the coating layer 2 and the process of forming the coating layer 4 are performed on separate lines, these two processes may be combined in tandem and performed continuously.

Further, although the above-mentioned matters and the matters to be described later relate to a single-core coated optical fiber, all of these matters can also be applied to a multi-core coated optical fiber called a tape type or the like.

In the embodiment of FIG. 3, the coated optical fiber 3 is wound onto a supply bobbin 10 from which it is unwound.

The unwound coated optical fiber 3 passes through a tension controller 11 in which one of two rollers approaches and moves away from the other, and then enters a heating furnace 12.

Equipped with a heater, atmospheric gas (Arb He, N2
The coated optical fiber 3 passing through the furnace is heated to a temperature of 400° C. or lower.

In this case, if the coated optical fiber 3 has already come into contact with water and has absorbed moisture, this is not necessary, but normally an atmospheric gas containing water (humidity) is supplied into the heating furnace 12. The coating layer 2 is caused to contact and react with water.

Water here refers to water at room temperature, heated water, steam, etc.

In this way, the coating layer 2 was brought into contact with water, and thus it can be said that the problem of OH groups was solved for the first time.

The coated optical fiber 3 that has passed through the heating furnace 12 enters the harmful gas remover 13.

This remover 13 is used to remove harmful gas components such as N2 from the coating layer 2, and is connected to a vacuum pump (not shown).

Therefore, when the coated optical fiber 3 passes through the remover 13, the harmful gas components in the coating layer 2 are degassed and removed.

Note that this harmful gas removal step can also be achieved by passing the coated optical fiber 3 through a harmless gas, for example an inert gas, at a low speed, and when such a means is taken, the remover If a known inert gas is supplied to the inside of 13 without evacuation, the harmful gas is replaced with harmless gas.

Of course, deaeration and gas replacement may be used together, and
By evacuating the inside of the heating furnace 12 as described above, the harmful gas generated within the heating furnace 12 can be immediately removed without using the remover 13.

After the coating layer 2 has been treated as described above, the coated optical fiber 3 is applied to a coating means 16 consisting of an extrusion molding machine 14A to form a coating layer 4 around the outer periphery of the coating layer 2, thereby forming a coated optical fiber 5. get.

After that, the coated optical fiber 6 is passed through the outer diameter measuring device 16 and the cooling tank 1.
7. It passes through a capstan 18 and an accumulator 19 and is wound up by a winder 20.

In the above, when the coated optical fiber 5 is cooled by the cooling bath 17, a cooling medium (for example, water) at or below room temperature is used.
However, it is clear from experiments that favorable results in terms of transmission characteristics can be obtained when hot water at room temperature or higher is used as the cooling medium.

In the above, the degree of pressure reduction when using the remover 13 to reduce the pressure inside it is preferably 45 cmHg or less, and when the remover 13 and the extrusion molding machine 14A are connected, the degree of pressure reduction of the remover 13 is 25 cmHg or less. ~45αHg is good,
When the remover 13 does not affect the extruder 14A,
It is preferable that the inside of the container 13 be as close to vacuum as possible.

Further, when forming the coating layer 4 on the outer periphery of the coated optical fiber 3 to obtain the coated optical fiber 5, the tension is set to 30 to 30
It is preferable to set the weight to 0 g, preferably 50 to 150 g.

The reason for this is that if the tension is less than 30 g, the optical fiber will be undulated (microbend), which will increase transmission loss during coating, and if the tension exceeds 300 g, the tension will become too large and the optical fiber may break.

Next, the embodiment shown in FIG. 4 will be explained.

In the embodiment shown in FIG. 4, compared to the embodiment shown in FIG.
'The covering means 16 are different.

That is, the coating means 16 in FIG. 3 consists of an extrusion molding machine 14A and forms the coating layer 4 made of thermoplastic resin, whereas the coating means 15 in FIG. 4 consists of a die-type coater 14.
The B1 curing furnace 14C is used to form a coating layer 4 made of thermosetting or photocurable resin.

Furthermore, the embodiment shown in FIG. 4 does not have the cooling tank 17 shown in FIG.
A dancer roller 21 is provided instead of the accumulator 19.

In the embodiment shown in FIG. 4, the coated optical fiber 6 is manufactured in the same manner as in the embodiment shown in FIG. 3, except for the above-mentioned differences.

Next, specific examples of the present invention and comparative examples thereof will be explained.

Specific example 1 A silica-based optical fiber 1 with a core diameter of 50 μmφ and an outer diameter of 125 μmφ is coated with silicone rubber with an outer diameter of 400 μm on the outer periphery.
Prepare a coated optical fiber 3 on which a coating layer 2 of φ is formed,
A coating layer 4 having an outer diameter of 900 μmφ made of nylon 12 is coated on the outer periphery of the coated optical fiber 3 by means shown in FIG.
A coated optical fiber 5 was obtained.

The linear speed at this time was 30 m/min on average, and the outer diameter of the coating layer 4 was controlled by feeding back the value measured by the outer diameter measuring device 16 to the take-up speed of the capstan 18.

The tension controller 11 was set to provide a tension of 75 g.

The heating furnace 12 was 240 m long, and the temperature inside the furnace was 260° C., and the atmosphere was an atmosphere with a room temperature of 25° C. and a humidity of 85%.

The degree of reduced pressure in the remover 13 is 35t7nHg, and the cooling tank 17
In this case, hot water at 70°C was used as a cooling medium to avoid rapid cooling of the ff1lfJ4.

The properties of the obtained coated optical fiber 6 are shown in the table.

Each of these figures was carried out in the same manner as in Specific Example 1 except for the conditions shown in Specific Examples 2 to 6 and Comparative Example Table, and coated optical fibers 6 were obtained respectively.

In the table, the increase in transmission Ps due to high temperature means coated optical fiber 6 and 8
The increase in transmission loss of the optical fiber 1 was measured at a wavelength of 0.85 μm after heating at 0° C. for 10 days.

This also refers to "increase in transmission loss at high temperatures" below.

In both Examples 1 to 6 and the comparative example, the transmission loss after forming the coating layer 4 was 2. s dB/Km (wavelength: 0.85 μm), and no increase in transmission loss was observed, but in the case of the comparative example, the increase in transmission loss due to high temperature was considerably large.

Concerning the cooling medium (hot water) in the cooling tank 17, in concrete example 1 at 70°C and concrete example 2 at 30°C, concrete example 1 is at 130°C.
The increase in transmission loss in Example 2 was 6 dB, less than 4 m, whereas that in Example 2 was more than 7 d13 J+++.

Specific Example 7 A coated optical fiber 6 was obtained in the same manner as in Specific Example 1 except that the coating layer 4 was made of polybutylene terephthalate resin.

In this specific example, the transmission loss after forming the coating layer 4 was 2.5 dB/hI (wavelength: 0.85 .mu.㎎), and the increase in transmission loss due to high temperature was 0.5 dB/Km.

Concrete Example 8 A coated optical fiber 6 was obtained in the same manner as in Concrete Example 1, except that the coating layer 4 was made of an epoxy acrylate photocurable resin using the means shown in FIG.

In this specific example, the transmission loss after forming the coating layer 4 is 2.5 dB/Km ('wavelength 0.8'5 μm)
The increase in transmission loss due to high temperature was 0.1 dB/Km.

Specific Example 9 A coated optical fiber 5 was obtained in the same manner as in Specific Example 8, except that the coating layer 4 was made of a silicone acrylate thermosetting resin.

In this specific example, the transmission port after forming the coating layer 4,
The increase is 2.5 dB/Km (wavelength 0.85μr=z)
The increase in transmission loss due to temperature increase was O, WB/KIrl.

As explained above, according to the present invention, after the coating layer of a coated optical fiber is brought into contact reaction with water, harmful gas components are removed from the existing coating layer, and an additional coating layer is added around the outer periphery of the existing coating layer. As a result, a coated optical fiber that can maintain good and stable transmission characteristics over a long period of time can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a primary coated optical fiber according to the present invention;
FIG. 2 is a sectional view of a secondary coated optical fiber manufactured according to the present invention, and FIGS. 3 and 4 are explanatory diagrams hinting at various embodiments of the present invention. 1110・@L optical fiber 2...Coating layer (primary) 3...Coated optical fiber (primary) 4...Coating layer (secondary) 6...Coating Optical fiber (secondary) 12...Heating furnace 13...Harmful gas remover 16...Coating means procedure amendment (-7:1t) 1. Indication of the case Patent application 1701852/1982 Title of the invention Method for manufacturing coated optical fiber 3, person making the amendment Relationship to the case Patent applicant Furukawa Electric Co., Ltd. , I) Subject power of attorney, full text of the specification, and drawing 7 Contents of the amendment Submit the attached power of attorney, typewritten full text of the specification (no change in content), and traced drawings (no change in content). that's all

Claims (6)

[Claims] (1) Manufacture of a coated optical fiber by causing the coating layer of the coated optical fiber to react with water, removing harmful gas components from the existing coating layer, and forming an additional coating layer around the outer periphery of the existing coating layer. Method. (2) A method for manufacturing a coated optical fiber according to claim 1, wherein harmful gas components are removed by degassing. (3) The method for manufacturing a coated optical fiber according to claim 1, wherein the harmful gas component is removed by replacing it with another harmless gas. (4) Young's modulus of the existing coating layer at room temperature is 2Kf/+g
The method for manufacturing a coated optical fiber according to claim 1rj4, which is A or less. (5) The method for manufacturing a coated optical fiber according to claim 1 or 4, wherein the existing coating layer is made of a thermosetting or photocurable resin. (6) A method for manufacturing a coated optical fiber according to claim 1, wherein a coating layer is formed on the outer periphery of an existing coating layer using an extrusion molding machine, and the coating layer is slowly cooled with hot water.