JPH02289804A - Optical fiber unit - Google Patents

Abstract

PURPOSE:To improve a low-temp. characteristic, productivity and color coding property and further terminating property by forming and integrating a primary coating consisting of a resin having small distortions at the time of coating and a secondary coating consisting of a foamed resin on the outer periphery of a laminate formed by superposing >=1 sheets of coated optical fiber ribbons. CONSTITUTION:This 12-fiber optical fiber unit is constructed by laminating three ribbons of the 4-fiber coated optical fibers 1 consisting of 4 optical fibers 5 and interposing two pieces of intervening cords 2, then forming the primary coating 3 and the secondary coating 4 of the foamed polyethylene thereon. The ribbon structure coated optical fibers 1 are formed by arranging 4 pieces of the optical fibers 5 in one row and integrally coating the fibers with a UV curing resin. The primary coating 3 is formed by extrusion molding of nylon and the secondary coating 4 of the foamed polyethylene of 50% foaming rate. The increase in low-temp. transmission loss is eliminated in this way and the temp. characteristics of the optical fiber unit are stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical fiber unit installed by a fluid flow flowing through a pipe, and particularly relates to an improvement in the structure of an optical fiber unit.

[Conventional technology]

As an example of a conventional optical fiber unit that is installed by a fluid flow flowing through a vibrator of this type, an optical fiber unit whose cross-sectional structure is shown in FIG. 3 is known (European Patent No. 0157610).

A plurality of optical fiber strands 35 are bundled, a primary coating 33 made of polypropylene with a high Young's modulus is applied to the outer periphery, and a secondary coating 34 made of foamed polyethylene is applied to the outer periphery of the primary coating 33.
It has a structure with

The reason why the primary sheathing 33 has a high Young's modulus is to prevent the shrinkage stress of the foamed polyethylene of the secondary sheath 34 from affecting the optical fiber strand 35 at low temperatures, so that it has a structure that resists shrinkage stress. This is because it is necessary.

Furthermore, in order to meet this structural requirement, it is desirable that the plurality of optical fiber strands 35 included in the primary coating 33 be tightly housed.

The reason why foamed polyethylene is used for the secondary coating 34 is that as an optical fiber unit that is installed by a gas flow flowing through a pipe, it is required to be lightweight and have a certain surface area. This is because the use of foamed resin is effective.

[Problem to be solved by the invention]

The structure of the conventional optical fiber unit illustrated in Fig. 3 is as follows:
No central tensile strength member is used for weight reduction and manufacturability.
Further, it is common that the optical fiber strands have a structure in which they are stored in a straight line without being twisted.

In the conventional structure, an increase in transmission loss was observed at low temperatures of the optical fiber.

It is easy to understand that the cause of this is the disordered arrangement and distortion of the optical fiber strands due to the low-temperature shrinkage force of the foamed polyethylene as the secondary coating in a low-temperature state.

On the other hand, the inventors believe that another reason for this increase in transmission loss is that polypropylene has low high-temperature fluidity and is coated in a considerably stretched state during extrusion, and after coating, the strain caused by the stretching during coating is released. It was predicted that the optical fiber would be in a meandering state and the transmission loss would be likely to increase.

In addition, in the conventional structure, the number of optical fibers that can be stored is limited, and in order to increase the number of fibers, it is necessary to place a large diameter intervening body in the center to increase the number of fibers per layer, or to increase the number of fibers per layer. Structures in which optical fibers are stacked and arranged in a two-layer structure have also been implemented, but these methods tend to complicate the manufacturing process, controllability of the process, and reduce transmission of the manufactured optical fiber unit. It is undesirable because it has problems with properties and mechanical properties.

Furthermore, the optical fiber unit of the conventional structure has a problem in that it is difficult to remove the primary coating when performing terminal processing such as color separation of the core wires, branching of the optical fibers, and splicing.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide an optical fiber unit that has significantly improved low-temperature characteristics, manufacturability, color separation properties, and terminal processing properties.

[Means to solve the problem]

To achieve the above object, the present invention provides an optical fiber unit that is installed by a fluid flow flowing through a pipe, and the optical fiber unit is a laminated layer formed by overlapping one or more tape-shaped optical fiber core wires. It is characterized by an integrated structure in which a primary coating made of a resin with little distortion during coating and a secondary coating made of a foamed resin are applied to the outer periphery of the body.

Here, as the resin for the primary coating, a thermoplastic resin with good high-temperature fluidity such as nylon, or a curable resin that is cured by ultraviolet rays, heat, etc. can be used.

In addition, a structure in which an intervening string is inserted into the space between the laminate formed by stacking the tape-shaped optical fiber cores and the primary coating to integrate it is effective. It is effective to have the function of a tear string for removing the primary coating and secondary coating when taking out the tape-shaped optical fiber strand.

[Effect]

The tape-shaped optical fiber core applied to the optical fiber unit of the present invention has a structure in which a plurality of optical fibers are arranged in a row and the outer periphery is coated with ultraviolet curable resin. Compared to the conventional structure in which fiber strands are bundled together, the tape-like structure of the present invention restricts the degree of freedom between the optical fiber strands, and since they are completely integrated, it is possible to reduce the temperature of the foamed polyethylene used as the secondary coating. The resistance to contraction force is also increased, and the increase in transmission loss due to the low temperature of the optical fiber is significantly reduced.

In addition, in the tape-shaped optical fiber core wire applied to the present invention, the individual optical fiber strands are arranged completely in a line, so that
There is no positional disturbance between the optical fiber strands, and therefore no increase in transmission loss due to positional disturbance of the optical fiber strands is observed in the manufacturing process, resulting in excellent manufacturability.

In addition, the tape-shaped optical fiber core can be used as a means of color identification, which can be freely selected depending on the purpose, such as the combination of the arrangement of the optical fibers and the coloring of the tape itself, making it easier to identify than the conventional bundle of individual optical fibers. much easier.

Further, by stacking a plurality of tape-shaped optical fibers, it is easy to increase the number of fibers.

Further, in the optical fiber unit of the present invention, by inserting the intervening string, the problem that the primary coating is difficult to form a perfect circle because the cross section of the laminate of tape-shaped optical fiber core wires is usually square is alleviated. The roundness of the covering can be improved. Furthermore, when the roundness is improved, the installation characteristics due to fluid flow can also be improved.

Furthermore, by selecting and applying a material having a certain level of strength and flexibility to the intervening string, it can also be used as a tearing string for removing the coating during terminal processing such as branching and splicing of optical fibers.

In addition, in order to address the problem of increased transmission loss at low temperatures, which was a problem in conventional technology, we have developed a primary coating for optical fiber units with a melt index of 2, an index of high-temperature fluidity.
Compared to conventional polypropylene, which has a value of Odg/min, an even greater improvement could be achieved by using nylon, which has this value of 5 to 10 dg/min.

Furthermore, by using a curable resin that has higher fluidity for this primary coating and can flow into gaps and integrate the entire primary coating, it is possible to suppress slipping and movement between the tape-shaped optical fiber cores. This enabled us to improve manufacturability and roundness of the primary coating.

Examples will be described below based on the drawings.

〔Example〕

FIG. 1 is a cross-sectional structural diagram of a first embodiment of the optical fiber unit of the present invention. 4 consisting of four optical fiber strands 5
This is a 12-fiber optical fiber unit having a structure in which three tape-shaped optical fiber cores 1 are laminated, two intervening strings 2 are inserted, and then a primary covering 3 and a secondary covering 4 of foamed polyethylene are applied. It is.

The optical fiber wire 5 is a glass fiber having an outer diameter of 0.125 mm and coated with two layers of ultraviolet curable resin to have an outer diameter of 0.25 IIItl.

The tape-shaped optical fiber coated wire 1 is made by arranging four optical fibers 5 in a row and forming a width l. 25au++
, which was formed by one-shot coating to a thickness of 0.4a+m.

The intervening string has an outer diameter of 0. 25 m of polyester string was applied.

The primary coating is made of nylon, and the secondary coating is made of extruded polyethylene foam with an expansion rate of 50%.

FIG. 2 is a cross-sectional structural diagram of a second embodiment of the optical fiber unit of the present invention. This embodiment has a four-core structure in which two tape-shaped optical fiber cores 21 each consisting of two optical fibers 25 are laminated, and a primary coating 23 and a secondary coating 24 of foamed polyethylene are applied. It is an optical fiber unit. 22 indicates an intervening string.

The tape-shaped optical fiber core wire 21 has a width of 0.7 mm and a thickness of 0.7 mm.
In the four cases, the same optical fiber wire 25 as in the first embodiment shown in FIG. 1 was used.

The glass fibers forming the optical fibers 5 and 25 used in the first and second embodiments have a core diameter of 50.
A μm multimode fiber was used.

In order to evaluate the low-temperature transmission characteristics and coating removability of the first and second embodiments of the present invention, an optical fiber unit having the conventional structure illustrated in FIG. 3 was also prototyped. The prototype optical fiber unit with a conventional structure had an outer diameter of 0.0 mm, which was the same as that used in the first and second embodiments. Seven multi-mode optical fibers coated with 25un of ultraviolet curable resin are bundled together, primary coated with polypropylene to an outer diameter of IIIfl+, and then secondary coated by extrusion molding of foamed polyethylene to an outer diameter of 2IIIfl+. It has a similar structure.

Furthermore, in order to clarify the curing of the present invention, an optical fiber unit having the structure shown in FIG. 4 was manufactured as Example 3, in which the primary coating of the second example was changed to polypropylene, which was used in conventional optical fiber units. .

A first embodiment of the present invention having the structure shown in FIGS. 1 to 4,
The measurement results of the increase in transmission loss at a temperature of -20°C and the time required to remove the lm-long coating of the terminal part for the optical fiber units of the second and third embodiments and the prototype example of the conventional structure are shown below. Shown in Table 1. The wavelength of the measured light was λ1.3 μm.

From the results shown in Table 1, the increase in low-temperature transmission loss was improved by 30% by changing the conventional structure to the configuration in which the tape-shaped optical fibers shown in Example 3 were laminated.

It was confirmed that the increase in transmission loss of an optical fiber having a nylon-sublayer coating structure using a shaped optical fiber core at a low temperature of -20°C can be reduced to about half or less compared to a conventional structure.

In addition, it was confirmed that by inserting an intervening string with a coating tearing function, the coating removal time could be shortened to about % compared to the conventional structure.

In addition, the fiber-end units of Example 1, Example 2, and Example 3 were integrated by inserting an intervening string, so that the roundness of the unit body was improved and the installation characteristics due to air flow were excellent. It was confirmed that there is.

On the other hand, as a fourth embodiment of the present invention, two pieces of the two-core tape-shaped optical fiber core wire 5l used in the second embodiment were laminated to form an example of an ultraviolet curable resin, which is one of the curable resins. A four-core optical fiber unit was manufactured, in which a primary coating 53 was applied using 950X 042 manufactured by DeSoto, USA, and a secondary coating 54 was applied using foamed polyethylene. The cross-sectional structure is shown in FIG. 5a, and reference numeral 52 indicates an intervening string.

In this embodiment as well, a multimode fiber with a core diameter of 50 μmφ was used as the optical fiber wire 55.

Table 2 shows the results of evaluating the transmission loss increase and coating removal time at low temperatures using the method described above.

As is clear from the results in Table 2, low-temperature transmission loss increases.
All of the coating removal times were greatly improved, and especially regarding the coating removal time, the elongation at break was 25% compared to the thermoplastic resin used for the primary coating in the first, second, and third examples.
Because of the small size, the result was that it was further shortened.

In addition, the good removability of the coating due to the use of a primary coating with low elongation at break means that the coating can be easily removed by pulling two tape-shaped optical fiber cores on both sides without the need for an intervening string used for tearing. There is also an intervening string 52 from the fourth embodiment of FIG. 5a shown in the fifth embodiment of FIG. 5b.
It was confirmed that the coating removal time by the above-mentioned method for the four-core optical fiber unit having the structure in which the coating was removed was 20 seconds/m, which was a good value.

〔Effect of the invention〕

As explained above, the optical fiber unit of the present invention has a completely integrated structure of tape-shaped optical fiber cores based on the tape-shaped optical fiber core structure for the optical fibers to be housed, so that the end fiber of the conventional structure can be We were able to solve the problem of increased low-temperature transmission loss due to the configuration of a bundle of single wires. Furthermore, by applying a highly fluid resin to the primary coating during coating, it was possible to stabilize the temperature characteristics of the optical fiber unit.

Further, due to the structure of the optical fiber unit of the present invention, remarkable improvements have been made in color discrimination and termination processing.

Furthermore, the tape-shaped fiber core structure makes it easy to increase the number of fibers in the optical fiber unit. Furthermore, by inserting the intervening string, it is possible to make the covering of the fiber unit tearable, and the roundness of the optical fiber unit is improved, as well as the installation characteristics.

[Brief explanation of drawings]

1, 2, 4, 5a and 5b are optical fiber unit embodiment 1 and embodiment 2 of the present invention, respectively.
, Example 3, Example 4, and Example 5. FIG. 3 is a cross-sectional view of an example of a conventional optical fiber unit. 1. 21, 41. 51... Tape-shaped optical fiber core wire, 2, 22, 42. 52... Intervening string, 3, 2
3, 33, 43. 53...Primary coating, 4,24
, 34. 44. 54...Secondary coating, 5, 2
5. 35, 45. 55... Optical fiber strand patent applicant Sumitomo Electric Industries, Ltd.

Claims (2)

[Claims] (1) In an optical fiber unit that is installed by a flow of fluid flowing through a pipe, the optical fiber unit is made of a resin on the outer periphery of a laminate formed by stacking one or more tape-shaped optical fiber cores. An optical fiber unit characterized by having an integrated structure with a primary coating and a secondary coating made of foamed resin. (2) In an optical fiber unit that is installed by a flow of fluid flowing through a pipe, the optical fiber unit is formed between a laminate formed by stacking one or more tape-shaped optical fiber cores and a primary coating. 1. An optical fiber unit characterized in that it has an integrated structure in which a primary coating made of resin and a secondary coating made of foamed resin are applied with an intervening string placed in the space.