JPH04184307A - Small-diameter coated optical fiber - Google Patents

Abstract

PURPOSE:To make the diameter of a coated optical fiber small without lowering transmission characteristic and mechanical strength by setting the Young's modulus and the thickness of a secondry coat equal to or above a specified value and setting the Young's modulus of a primary coat equal to or under a specified value and the thickness thereof equal to or above a specified value so that the diameter of the coated optical fiber may be equal to or under a specified value. CONSTITUTION:The coated optical fiber 1 is constituted by providing the primary coat 3 on a bare optical fiber 2 whose diameter is 125mum and further providing the secondary coat 4 on the coat 3, and the outside diameter of the coat 4 is set at <=210mum. The Young's modulus and the thickness of the secondary coat 4 are set at >=40kg/mm<2> and >=20mum, respectively. Then, the Young's modulus and the thickness of the primary coat 3 are set at <=1kg/mm<2> and >=10mum, respectively. Thus, the diameter of the coated optical fiber is made small without changing an in-use optical communication system. The sufficient mechanical strength of the coated optical fiber is obtained and the coat is not damaged at the time of producing or handling. When a temperature is low, the contracting stress of the primary coat in a longitudinal direction directly acts on the bare optical fiber, so that a failure that the microbend occurs in the coated optical fiber is prevented and the diameter of the coated optical fiber is made small.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a coated optical fiber used for optical communication fibers, and more particularly to the structure of a coated optical fiber having a small diameter.

Small-diameter optical fiber cores are important for realizing high density and multi-core fibers in optical cables.

``Prior art'' Conventionally, optical fiber cores used for general optical communication have been coated on bare optical fibers with a diameter of 125 μm.
A primary coat (secondary coating) and a secondary coat (secondary coating) are applied, and the primary coat outer diameter is 0, 4.
mm, with a secondary coat outer diameter of 0.9 mm being used as standard. As the primary coat material, phosphor resin, UV curing resin, etc. are used, and as the secondary coat material, nylon resin, etc. are used.

[Problem to be solved by the invention] By the way, in long-distance optical communications, etc., a large number of optical fiber cores are housed in a cable to form a long-distance cable. In order to increase the density of optical fibers, it is desirable to make the diameter of each optical fiber as thin as possible. For this purpose, it is being considered to make the primary coat and secondary coat of the optical fiber thinner.

However, if these coatings are made too thin, the mechanical strength of the coating will decrease and it will no longer function as a coating layer. For example, if a hard secondary coat is directly coated on a bare wire without a soft primary coat, the shrinkage stress in the longitudinal direction of the coating acts directly on the bare optical fiber at low temperatures, causing microbends in the fiber and transmission loss. This may lead to an increase in

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a coated optical fiber whose diameter can be reduced without deteriorating the transmission characteristics or mechanical strength of the optical fiber.

"Means for Solving the Problems" The present invention provides a cored optical fiber in which a bare optical fiber is provided with a primary coat and a secondary coat thereon, in which the secondary coat has a Young's modulus of 40 kg/1 m' or more and a thickness of 20 μm. In addition, the above problems were solved by configuring the primary coat to have a Young's modulus of 1 kg/+n+n' or less, a thickness of 10 μm or more, and a diameter of the optical fiber core to be 210 μm or less.

The present invention will be explained in detail below.

FIG. 1 is for explaining an example of a coated optical fiber according to the present invention, and this coated optical fiber 1 includes a primary coat 3 provided on a bare optical fiber 2 having a diameter of 125 μm. Furthermore, a secondary coat 4 is provided thereon, and the outer diameter of the secondary coat 4 is set to 210 μm or less.

The Young’s modulus of the above secondary coat 4 is 40 kg/mi”
The thickness is 20 μm or more, and the primary coat 3
The Young's modulus is set to be 1 kg/mm' or less and the thickness is set to 10 μm or more.

The material for the primary coat 3 has a Young's modulus of 1 kg/mm so that it functions as a buffer material for the bare optical fiber.
The following materials are suitable. If the Young's modulus of this primary coat material is 1 kg/mm2 or more, its function as a buffer material for the bare optical fiber will deteriorate, and the shrinkage stress in the longitudinal direction of the primary coat will act directly on the bare optical fiber at low temperatures. , the optical fiber is likely to cause microbends.

In addition, the material for the secondary coat has a Young's modulus of 40.
Materials with high strength of kg/mm' or more are used. Yank rate of this secondary coat material is 40kg/mff
If it is less than 1', the mechanical strength of the core wire 1 decreases, the coating is likely to be damaged during the bruising or rewinding process of the core wire, and the average survival length of the core wire becomes short.

The materials for these primary coats and secondary coats include urethane acrylate ultraviolet curing resin,
UV-curable resins such as epoxy acrylate-based UV-curable resins, polyester acrylate-based UV-curable resins, and polybutadiene acrylate-based UV-curable resins are suitable, and among these various UV-curable resins, Young's modulus of 1 kg/ Soft material less than mm' and Young's modulus 40
kg/am” hard materials can be selected and used as appropriate.The resin material is not limited to ultraviolet curable resins, and soft materials such as silicone resins, styrene-based elastomers, and amide-based elastomers can be used as primary coating materials. A high-strength resin such as nylon may be used as a secondary coating material.

In the optical fiber core 1 according to this example, a primary coat 3 with a Young's modulus of I kg/mm2 or less and a thickness of 10 μm or more is provided on a bare end fiber 2 with a diameter of 125 μm, and a primary coat 3 with a Young's modulus of I kg/mm2 or less and a thickness of 10 μm or more is provided on top of the primary coat 3. 40kg/ll1m! As described above, the secondary coat 4 with a thickness of 20 μm or more is provided and the outer diameter of the optical fiber core is 210 μm or less, so that the mechanical strength of the core is sufficient and there is no damage to the coating during manufacturing or handling. In addition, the shrinkage stress in the longitudinal direction of the primary coat acts directly on the bare optical fiber at low temperatures, making it possible to reduce the diameter of the coated fiber while preventing the disadvantage that the coated optical fiber is susceptible to micro-bending.
A thin core wire with excellent mechanical strength and transmission characteristics can be obtained.

``Example'' A quartz-based single mode fiber bare wire with a diameter (indicated by A in FIG. 1) of 125 μm is coated with primary coats and secondary coats 1 of various thicknesses and materials shown in Table 1. Fiber core wire was manufactured.

As the primary coat and secondary coat materials, urethane acrylate-based ultraviolet curable resin was used, and the composition ratio of polymerizable oligomer and monomer in the resin was varied to achieve a Young's modulus of 0, 1 kg/mm', and 0 when cured.
, 5 kg/mm”, I, Okg/mm2.
5, 0 kg/mm', 40 kg/mm', 6
0 kg/mm" and 80 kg/mm2 were used.

Table 1 (Table 1) A tension of 1% x 1 second was applied to each optical fiber (test length 10 km) shown in Table 1, and the average survival length and number of breaks were measured. The results are shown in Table 2.

Margin below Table 2 From the results in Table 2, the thickness of the secondary coat is 20. c.
zn or less, or Young's modulus or 40 kg/l1lff
A core wire with a coating thickness of less than i' has a poor blue and is likely to break, while a coat thickness of 20 μm or more and a Young's modulus of 40
It was confirmed that the core wire with a strength of kg/mm' or more did not break and had sufficient mechanical strength.

Next, changes in loss due to temperature changes in each core wire were investigated. Each of the core wires 1 to 16 shown in Table 1 (the parameters of these core wires are that the average mode field diameter is 9.5 μm, the cutoff wavelength is 1.21 μl on average, 11. Δn is 0.30% on average)
) were formed into a bundle with a length of 500 m and a diameter of 300 mm, measurement light (wavelength 1.3 μm) was incident on one end to measure the loss, and the pieces were placed in a -40°C cryostat to measure the increase in loss. (dB/Kl1l) was measured. This result is the third
Shown in the table.

Margin below Table 3 Table 11 t O,31' From the results in Table 3, the loss of core wires whose primary coat material has a Young's modulus of 1 kg/mm' or more increases due to low temperature changes; It was confirmed that the core wire with a Young's modulus of 1 kg/mff1' or less had no increase in loss due to temperature changes.

"Effects of the Invention" As explained above, the optical fiber core of the present invention has a primary coat and a secondary coat on the bare optical fiber, and has an outer diameter of 210 μm or less, so it is not necessary to change the currently used optical communication system. It is possible to reduce the diameter of the core wire without causing any problems.

Moreover, the Young's modulus on the bare optical fiber is I kg/ml.
A primary coat with a thickness of 10 μm or more with llff1 or less is provided, and a Young's modulus of 40 kg/
A secondary coat with a thickness of 20 μm or more is provided, and the outer diameter of the optical fiber is 210 μm or less, so the mechanical strength of the core is sufficient and the coating will not be damaged during manufacturing or handling. Furthermore, at low temperatures, the shrinkage stress of the primary coat in the longitudinal direction acts directly on the bare optical fiber, making it possible to reduce the diameter of the coated optical fiber while preventing the inconvenience of micro-bending in the coated optical fiber. A thin core wire with excellent mechanical strength and transmission characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 shows one embodiment of the present invention, and is a cross-sectional view of a coated optical fiber.゛l... Optical fiber core 2... Bare optical fiber 3... Primary coat 4... Secondary coat

Claims (1)

[Claims] In an optical fiber core wire in which a primary coat and a secondary coat are provided on a bare optical fiber, the secondary coat has a Young's modulus of 40 kg/mm^2 or more and a thickness of 20 μm or more, and the primary coat has a Young's modulus of 20 μm or more. 1 kg/mm^2 or less and a thickness of 10 μm or more,
A thin optical fiber coated wire, characterized in that the diameter of the optical fiber coated wire is 210 μm or less.