JPS6254206A - Covered optical fiber - Google Patents

Abstract

PURPOSE:To hold the satisfactory transmission characteristic at the low temperature area by specifying the physical properties of the photo-setting resin to constitute the external covered layer of the covered optical fiber. CONSTITUTION:In the covered optical fiber where the external covered layer composed of the hard photo-setting resin is formed at the outer circumference of the optical fiber, a light absorption coefficient of the photo-setting resin to constitute the external covered layer is alpha, the transmitting distance of the light in the photo-setting resin is X1 and X2, the strength of the light in the transmitting distance X1 and X2 is I(X1) and I(X2), and then, alpha=-1/(X1-X2).log10I(X2)/I(X1) is >=1.3(1/mm). Thus, for the photo-setting resin having the comparatively large light absorption coefficient, as the process of the setting, the setting of the resin surface occurs, the surface setting part suppresses or eases the shrinkage and the tightening force to the optical fiber is made smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION 1.Field of Application of Industry-1-J The present invention relates to a coated optical fiber with a center of gravity or with multiple cores, the outer coating layer of which is made of a photocurable resin.

``Prior Art J'' The following is known as one type of coated optical fiber.

This has a diameter of 125. ■The outer periphery of a quartz-based optical fiber made of The outer coating layer is formed by coating a hard resin such as a resin, and the outer diameter of the coating is about 250 to 900 mm.

In the above, the reason why the inner coating layer is made of soft resin is to obtain a buffering effect, and the reason why the outer coating layer is made of hard resin is to prevent external forces from affecting the optical fiber. This is to provide mechanical properties.

rProblem to be Solved by the Invention 1 By the way, in the case of synthetic resins, they generally shrink when cured, and in the case of optical fiber coating layers (made of synthetic resins), they shrink in the axial and radial directions of the optical fibers. The radial contraction force tightens the optical fiber.

Such shrinkage of the coating layer also occurs depending on the environmental temperature in which the coated optical fiber is used. In particular, when the outer coating resin of the coated optical fiber is hard and the coated optical fiber is used in a low temperature range, the outer coating layer shrinks at low temperature F. The clamping force of the coating layer and the axial shrinkage stress caused by the clamping force have an unfavorable effect on the transmission characteristics of the optical fiber.

In other words, in a low temperature range, the hard outer coating layer wraps around the optical fiber and contracts, and the tightening force and axial contraction stress at this time distort the optical fiber, increasing the transmission loss of the optical fiber. cause

In view of the problem described in I--, the present invention provides a coated optical fiber that can maintain good transmission characteristics in a low temperature range by appropriately setting the physical properties of the photocurable resin that constitutes the outer coating layer of the coated optical fiber. This is what we are trying to provide.

Means for Solving Problem 1 The present invention provides a coated optical fiber in which an outer coating layer made of a hard photocurable resin is formed on the outer periphery of the optical fiber. Let α be the light absorption coefficient of the photocurable resin, let the transmission distances of light in the photocurable resin be XI, X2, and let the intensity of light at the transmission distances x1, X2j be I (XI ), I (X2), a −-1/(XI−X211og+ol(X
2)/I(X1) is 1.3 (1/mm) or more -1-.

In the coated optical fiber of the present invention described in Section 1, the outer coating layer is made of a hard photocurable resin, and the light absorption coefficient α of the resin is 1.
．． 3 (1/m) or more, 1-, the transmission characteristics in the low temperature range can be maintained well.

The reason is as follows.

That is, in the case of a photocurable resin having a relatively large light absorption coefficient such as α-1,3 (1/am), the surface of the resin is cured during the curing process, and then the rest of the resin is cured.

In this resin curing process, the outer diameter of the coating layer is determined at the surface curing stage and the physical properties of the surface hardened area are stabilized, so the remaining resin subsequently hardens and the resin tends to shrink in the radial direction. When the hardened surface of the bipedal part suppresses or alleviates its contraction, the clamping force against the optical fiber (
&J! Reduce the contraction force.

Next, even if the outer coating layer is exposed to a low temperature range and this generates a clamping force (low-temperature contraction force) on the optical fiber, the clamping force (curing contraction force) is small, so the overall The clamping force does not increase, therefore, the clamping force does not directly distort the shape of the optical fiber, and the axial shrinkage stress acting on the optical fiber is alleviated.
As a result, the low-temperature transmission characteristics of the coated optical fiber can be maintained well.

In addition, the light absorption coefficient of the outer coating layer is α-1,3 (17H)
When the coating layer is less than 100%, the entire coating layer is cured at once, so the clamping force (curing shrinkage force) on the optical core/f-bar becomes large, and the clamping force in the low temperature range (low-temperature shrinkage force) increases. When multiplied, the overall clamping force on the optical fiber increases.

In other words, distortion occurs in the optical fiber due to large clamping force or axial shrinkage stress caused by the clamping force.
Transmission characteristics deteriorate at low temperatures.

rExample 1 Examples of the coated optical fiber according to the present invention will be described below with reference to drawings, tables, and the like.

FIG. 1 shows the central coated optical fiber l in the present invention.

In the coated optical fiber 1 shown in FIG. 1, an inner coating layer 3d is formed at -1- of a silica-based optical fiber 2 having a core and a cladding, and an outer coating layer 4 is formed at 4- of the inner coating layer 3a. It is something.

FIGS. 2 and 3 show a multi-core coated optical fiber 1 according to the present invention.

Of these, in the coated optical core f-bar 1 shown in FIG.
It has a circular cross-sectional shape.

In the coated optical fiber 1 shown in FIG. 3, optical fibers 2 having inner coating layers 3a and 3b are arranged in parallel with each other and are collectively covered with an outer coating layer 4, and its cross-sectional shape is similar to that of a tape. It has a flat shape.

In the above, the inner coating layer 3a is made of a soft resin such as a photocurable resin, thermosetting silicone, thermoplastic elastomer, or ethylene vinyl acetate, and the Young's+E of the inner coating layer 3a at room temperature is E≦1 kg/ll112.
It is desirable that

The inner coating layer 3b is also made of a suitable resin such as a photocurable resin, a thermosetting resin, a thermoplastic resin, etc.
The Young's modulus E at room temperature is larger than that of the inner coating layer 3a.

The outer coating layer 4 is made of a photocurable resin having a light absorption coefficient of α-1.3 (+/am) or more by 1°, and the outer coating layer 4 has Young's “4.iE” at room temperature of E≧Ikg/m. ■2.Especially E≧1
0 kg/■■2 is desirable.

Note that 1- on the outer periphery of the coated optical fiber 1 mentioned above.

A colored layer may be provided for the purpose of core wire identification.

Next, specific examples of the present invention and comparative examples thereof will be described. In these examples, a coated optical fiber l having the structure shown in FIG. 1 was used.

The optical fiber 2 in this case is a GI type with a core diameter of 50 μΦ, a cladding diameter (outer diameter) + 25tΦ, an inner coating layer 3a has a diameter (outer diameter) of 300 ILsΦ, and an outer sheathing layer 4 has a diameter (outer diameter) of 300 ILsΦ. ) are 900μ■φ (Table 1) and 5
00 feed amount φ (Table 1).

Table 1 Table 2 In the table, A is E=0.23kg/Ryu2 ultraviolet curable acrylate resin, B is E=0.31kg/mm2+7)l
The resin, C is E=59kg/Peng m2, the resin D is E=7? kg/intestinal ugliness 2''2 resin, F is E=E14k
g/fat 2 of the above resin, G is E=35kg/intestinal 2 of 1
-Resin, H is 42 resin with E=35kg/Hoho 2.

Note that H is the resin of G, in which α is changed by changing the photoinitiator without changing the physical property values.

E is Young's modulus at room temperature (23°C), which is
Regarding a sheet sample with a thickness of 0.2 tm having the shape of dumbbell No. 2 according to JIS K7113, the gauge line interval is 25
■It was determined from the stress when a strain of 2.5 t was applied under the condition of a hat pulling speed of 1 m/min.

In addition, α is the light absorption coefficient of the outer coating layer 4 before curing, and the light absorption coefficient here refers to the wavelength range 320 to 3.
It was determined from the average value of light intensity at 90 nm.

That is, let the intensities of light with wavelength λ at transmission distances X1 and x2 be respectively I(X+) and I(X, ri), and the average value in these wavelength ranges = 320 to 390 tv, as shown in the enlarged O , the outer coating layer 4 has a light absorption coefficient α-
In Examples 1 to 4 of the present invention, which are made of a photocurable resin of 1,3 (1/Peng) or more, the temperature characteristics are extremely good, whereas the outer coating layer 4 has a light absorption coefficient α= 1.3 (1/
In Comparative Examples 1 to 3 consisting of a photocurable resin with a thickness of less than
Extremely poor temperature characteristics.

This can be said to be due to the reason stated in the section 1 of the effect.

Note that the outer coating layer 4 has a light absorption coefficient α-1,3 (1/as
) If the photocurable resin is made of the following photocurable resin, a coated optical fiber l with good transmission characteristics at low temperatures can be obtained, as is clear from iz, but if the light absorption coefficient of the outer coating layer 4 is 7.0 (1 /■
m) If it is above υ, the curing speed of the resin will be slow and productivity will be reduced, so the light absorption coefficient of the outer coating layer 4 is 7.
It is preferable to set it to 0 (1/am) or less.

1. Effects of the invention, I As explained above, the coated optical fiber according to the present invention has an outer coating layer made of a photocurable resin having a light absorption coefficient of 1.3 (1/am) or more, so that it can be used at low temperatures. It is possible to maintain good transmission characteristics in the region.

[Brief explanation of drawings]

The drawings show various embodiments of the coated optical fiber according to the present invention.
FIG. 3 is a cross-sectional view of a multi-core coated optical fiber. 1... Coated optical fiber 211 dispute Q... Optical fibers 3d, 3b... Inner coating layer 4... Φ, Outer coating layer agent Patent attorney Yoshio Saito f Rith 2 Figure 3 Jρ Figure 3] b2 r 73α = 4 0L 3b h

Claims (4)

[Claims] (1) In a coated optical fiber in which an outer coating layer made of a hard photocurable resin is formed around the outer periphery of the optical fiber, the light absorption coefficient of the photocurable resin constituting the outer coating layer is α. , the transmission distance of light in the photocurable resin is
_1, X_2, and the intensity of light at the transmission distances X_1,
A coated optical fiber characterized in that (X_2)/I (X_1) is 1.3 (1/mm) or more. (2) The coated optical fiber according to claim 1, wherein an outer coating layer is formed directly on the outer periphery of the optical fiber. (3) The coated optical fiber according to claim 1, wherein one or more inner coating layers made of a soft resin are formed on the outer periphery of the optical fiber, and an outer coating layer is formed on the outer periphery of the inner coating layer. . (4) The coated optical fiber according to any one of claims 1 to 3, comprising a single optical fiber within the outer coating layer.