JP2001083381A - Coated optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated optical fiber which can maintain good transmission characteristics at low temperature even when the fiber includes a glass fiber having poor bending strength. SOLUTION: The coated optical fiber 1 consists of, successively from the center, the glass fiber 11, a primary layer 12 and a secondary layer 13. The glass fiber 11 essentially comprises quartz glass with addition of impurities such as Ge and F elements in a specified distribution and has a core region having a high refractive index and a clad region having a low refractive index. Each of the primary layer 12 and the secondary layer 13 is made of, for example, a UV-curing resin. The resin of the primary layer 12 has 0.03 to 0.10 kg/mm2 Young's modulus at normal temperature. The tear strength of the primary layer 12 at 0 deg.C is 1.0 to 7.0 kg/mm. The adhesion strength between the glass fiber 11 and the primary layer 12 at 0 deg.C is 100 to 800 g/cm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated optical fiber in which a primary layer and a secondary layer are sequentially coated on the outer periphery of a glass fiber, and more particularly to a coated optical fiber coated with an improved primary layer resin. is there.

[0002]

2. Description of the Related Art In a coated optical fiber used for optical communication or the like, a primary layer having a low Young's modulus and a secondary layer having a high Young's modulus are sequentially coated on the outer periphery of the glass fiber in order to protect the glass fiber. Glass fiber is
The outer diameter is 125 μmφ. The primary layer is a resin having a Young's modulus of about 0.05 to 0.15 kg / mm ² and an outer diameter of about 180 to 210 μmφ. The secondary layer is a resin having a Young's modulus of about 50 to 150 kg / mm ² and an outer diameter of about 230 to 250 μmφ.

[0003] Such a coated optical fiber is required to have stable transmission characteristics under the environment in which it is used. However, transmission loss may increase at low temperatures compared to normal temperatures. This phenomenon is caused by non-uniform stress being applied to the glass fiber for some reason such as the material properties (Young's modulus, Poisson's ratio, coefficient of linear expansion, etc.) of the resin in the primary layer and the secondary layer, the structure and the coating conditions. You.

In order to solve such a problem, Japanese Patent Application Laid-Open No.
The coated optical fiber disclosed in Japanese Patent Application Publication No. 200515 reduces the lateral pressure applied to the glass fiber even at a low temperature by appropriately defining the Young's modulus, the coefficient of linear expansion, and the thickness of each of the primary layer and the secondary layer. Therefore, stable transmission characteristics are obtained even at low temperatures.

[0005]

In recent years, in order to carry out long-distance and high-bit-rate optical communication such as submarine optical communication, a zero-dispersion wavelength in a wavelength band of 1.55 μm and a large effective core area are required. A dispersion-shifted optical fiber is being put to practical use. This dispersion-shifted optical fiber has a larger effective core area and a weaker transmission characteristic than a standard single-mode optical fiber having a zero-dispersion wavelength in the 1.3 μm wavelength band. Therefore, even in the case where the single-mode optical fiber has a small bending which has not been a problem in the past, the transmission characteristics of the dispersion-shifted optical fiber having a large effective core area are deteriorated due to the microbending.

That is, even if a coated optical fiber is constructed according to the invention disclosed in the above publication, if the glass fiber contained in the coated optical fiber is weak to bending, the transmission characteristics of the coated optical fiber deteriorate at low temperatures. May be. However, coated optical fibers used in submarine optical communication are constantly exposed to a low-temperature environment of 0 to 5 ° C, so that even when glass fibers that are weak to bending are included, good transmission characteristics are maintained at a low temperature of about 0 ° C. It is necessary to.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a coated optical fiber capable of maintaining good transmission characteristics at a low temperature even when a glass fiber which is weak in bending is included. The purpose is to do.

[0008]

A coated optical fiber according to the present invention is a coated optical fiber in which a primary layer and a secondary layer are sequentially coated on the outer periphery of a glass fiber,
The primary layer has a Young's modulus at room temperature of 0.03 to
0.10 kg / mm ² , and the tear strength at 0 ° C. by the right angle tearing method of JIS K7128 is 1.0 to 7.0.
kg / mm, and the adhesion to the glass fiber at 0 ° C. is 100 to 800 g / cm. According to this coated optical fiber, the tear strength at 0 ° C. is 1.0
kg / mm or more and the adhesion at 0 ° C. is 100 g / cm
With the above, destruction or peeling of the primary layer can be prevented against stress caused by contraction of the primary layer at a low temperature, and an increase in transmission loss at a low temperature can be suppressed. A tear strength at 0 ° C. of 7.0 kg / m
m or less, and the Young's modulus of the primary layer is 0.03-0.
By setting the value within the range of 10 kg / mm ² , the lateral pressure characteristics can be improved. Further, by setting the adhesion at 0 ° C. to 800 g / cm or less, it is easy to remove the coating of the coated optical fiber.

The coated optical fiber according to the present invention has an effective core area of 60 μm ² or more and a wavelength of 1.55 μm.
It has a zero-dispersion wavelength in the m band, and has a zero dispersion wavelength of 1.55 μm.
The difference between the transmission loss at 23 ° C and the transmission loss at 23 ° C is 0.00
5 dB / km or less, and an increase in transmission loss in a lateral pressure test is 1.0 dB / km or less. According to this coated optical fiber, good transmission characteristics can be maintained even at a low temperature, and an increase in transmission loss in a lateral pressure test is within an allowable range. It is suitably used as an optical transmission line for performing optical communication at a high bit rate over a distance.

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view illustrating a coated optical fiber according to the present embodiment. The coated optical fiber 1 according to the present embodiment has a glass fiber 11, a primary layer 12, and a secondary layer 13 in order from the center. The secondary layer 13 may be composed of a plurality of layers having different characteristics such as Young's modulus and expansion coefficient.

The glass fiber 11 is mainly composed of quartz glass, is doped with impurities such as Ge element and F element in a predetermined distribution, and has a high refractive index core region and a low refractive index cladding region. The outer diameter of the glass fiber 11 is generally 125 μmφ. The values such as the effective core area and the zero dispersion wavelength of the glass fiber 11 may be arbitrary. However, as described later, even if the glass fiber 11 is a dispersion-shifted optical fiber having an effective core area of 60 μm ² or more and having a zero-dispersion wavelength in the 1.55 μm band, good transmission characteristics are maintained even at a low temperature. can do.

Primary layer 12 and secondary layer 13
Each is, for example, an ultraviolet-curable polyether-based urethane acrylate-based resin. The resin of the primary layer 12 has a Young's modulus at room temperature of 0.03 to 0.10 kg / mm.
² The primary layer 12 has a tear strength at 0 ° C. of 1.
0 to 7.0 kg / mm. The adhesion between the glass fiber 11 and the primary layer 12 at 0 ° C. is 100 to 8
00 g / cm. Note that the resin of the secondary layer 13 has a Young's modulus of about 50 to 150 kg / mm ² . The outer diameter of the primary layer 12 is about 180 to 210 μmφ, and the outer diameter of the secondary layer 13 is about 230 to 250 μmφ.

A method for measuring the Young's modulus is Push in Modulus.
Test (issued in 1994, IWCS, Vol. 43, No. 522
Page), the primary layer 1 of the coated optical fiber 1
The Young's modulus of the resin No. 2 is directly evaluated. Primary Tier 1
This is because, in the resin used in 2, the Young's modulus measured with the glass fiber 11 covered is lower than the Young's modulus measured in the film state. This is because a glass fiber 11 is drawn from an optical fiber preform, and a resin is applied and cured. In a drawing apparatus, the temperature becomes high due to radiant heat and heat generated by a curing reaction in an ultraviolet irradiation apparatus for curing the resin. This is because the crosslinking reaction does not proceed because the termination reaction becomes dominant. Therefore, the Young's modulus of the resin of the primary layer 12 is measured in a state where the primary layer 12 is applied and cured on the outer periphery of the glass fiber 11.

The measuring method of tear strength is based on JIS K71.
28 right angle tearing method. The primary resin sheet serving as a measurement sample was cured in a nitrogen gas atmosphere at an irradiation amount of ultraviolet light of 100 mJ / cm ² to have a cured thickness of 100 mJ / cm ^2.
μm.

The method for measuring the adhesion is as follows.
First, a quartz glass plate is immersed in sulfuric acid for 5 minutes or more to wash the surface, and a resin liquid is applied on the surface of the washed quartz glass plate and cured, so that the thickness of the cured resin is 200 μm. After leaving this at 25 ° C. in an atmosphere of 50% RH for one week, the cured resin was removed from the quartz glass plate in a 180 ° direction over a width of 50 mm at a pulling speed of 200 mm / min.
Peel off by mm. Then, the maximum value of the force per unit width when peeling the cured resin is defined as the adhesion force.

Next, the coated optical fiber 1 according to the present embodiment
Four Examples 1 to 4 will be described together with six Comparative Examples 1 to 6.

In each of Examples 1 to 4 and Comparative Examples 1 to 6, a dispersion-shifted optical fiber having a zero-dispersion wavelength in a wavelength band of 1.55 μm was used as the glass fiber 11. This glass fiber 11 had a double-core type refractive index profile, an effective core area of 85 μm ² , and an outer diameter of 125 μm. Examples 1-4 and Comparative Examples 1
6. The outer diameter of each primary layer 12 was 190 μm, the outer diameter of secondary layer 13 was 240 μm, and the Young's modulus of the resin of secondary layer 13 was 80 kg / mm ² . As a resin for each of the primary layer 12 and the secondary layer 13, an ultraviolet-curable polyether-based urethane acrylate-based resin was used.

The tear strength and Young's modulus of the primary layer 12 were adjusted according to the molecular weight of the polyether portion of the UV-curable resin and the type of diluent monomer. That is, by increasing the molecular weight of the polyether portion of the ultraviolet-curable resin, or by selecting a linear monofunctional monomer having a large molecular weight, the primary layer 1
2, the tear strength and Young's modulus can be reduced. Conversely, by reducing the molecular weight of the polyether portion of the ultraviolet curable resin, by increasing the concentration of urethane groups, or by selecting a monomer having a rigid molecular structure such as a benzene ring or a polyfunctional monomer. Thereby, the tear strength and the Young's modulus of the primary layer 12 can be increased by increasing the crosslinking density of the ultraviolet curable resin.

The adhesion between the primary layer 12 and the glass fiber 11 was adjusted by the amount of a polar monomer (for example, acrylamide, N-vinylpyrrolidone, acryloylmorpholine) used in the above-mentioned ultraviolet curable resin. Also, the adhesion can be adjusted by the amount of the silane coupling agent.

FIG. 2 shows Examples 1-4 and Comparative Examples 1-6.
4 is a table summarizing characteristics and the like in each of them. This chart shows, from left to right, tear strength at 0 ° C., adhesion at 0 ° C., state of primary layer 12 at 0 ° C., loss increment at 0 ° C. low temperature test, Young's modulus of primary layer 12 at room temperature. , Loss increments in the cold side pressure test, and collective stripping of the tape core wire. The measuring methods for the tear strength, adhesion and Young's modulus are as described above.

With respect to the state of the primary layer 12, the presence or absence of abnormalities such as destruction or peeling of the primary layer 12 was confirmed by observing each coated optical fiber from the side with a magnification of 50 times using an optical microscope. . For the loss increment in the 0 ° C. low temperature test, each coated optical fiber was
As a 0 m bundle, the transmission loss of each coated optical fiber at 23 ° C. was measured with an optical power meter, and after leaving each coated optical fiber at 0 ° C. for 100 hours, the transmission loss of each coated optical fiber at 0 ° C. was measured. It was measured with a power meter and determined by subtracting the transmission loss at 23 ° C. from the transmission loss at 0 ° C. For the loss increment in the room temperature side pressure test,
Tension 1 on the bobbin wrapped with No. 000 sandpaper
The transmission loss at a wavelength of 1.55 μm was measured by OTD in a state where each coated optical fiber was wound by a length of 600 m at 00 g and a bundle of each coated optical fiber having a length of 1000 m.
R was measured, and the transmission loss of the latter was subtracted from the transmission loss of the former.

As can be seen from this figure, the primary layer of each of the coated optical fibers of Examples 1 to 4 included in this embodiment has a Young's modulus at room temperature of 0.03 to 0.10 kg.
/ Mm ² and the tear strength at 0 ° C. is 1.0 to 7.0 k.
g / mm, and the adhesion to the glass fiber at 0 ° C. was 100 to 800 g / cm. And Examples 1 to
4 In each of the coated optical fibers, the primary layer did not have any abnormality at 0 ° C., the loss increment in the 0 ° C. low temperature test was −0.001 dB / km, which was good, and the loss increment in the room temperature side pressure test was good. Is 0.264 to 0.488 dB / k
m, which was within an allowable range, and the tape core wire collective coating removal property was good.

On the other hand, the coated optical fiber of Comparative Example 1 has a large tear strength at 0 ° C. of 10.7 kg / mm.
Since the Young's modulus at room temperature is as large as 0.20 kg / mm ² , the loss increment in the room temperature side pressure test is 1.746 dB / k.
m. Since the coated optical fiber of Comparative Example 2 has a small tear strength at 0 ° C. of 0.5 kg / mm,
As a result, thermal stress fracture was observed in the primary layer, and the increase in loss in the 0 ° C. low temperature test was as large as 0.019 dB / km.

The coated optical fiber of Comparative Example 3 has an adhesion of 830 g / c between the glass fiber and the primary layer at 0 ° C.
m, the tape core wire collective coating removal property was poor. In the coated optical fiber of Comparative Example 4, since the adhesion between the glass fiber and the primary layer at 0 ° C. was as small as 70 g / cm, the interface between the primary layer and the glass fiber was separated at 0 ° C. The loss increment in the low temperature test was as large as 0.010 dB / km.

Since the coated optical fiber of Comparative Example 5 had a large Young's modulus at room temperature of 0.12 kg / mm ² , the loss increment in the room temperature side pressure test was as large as 1.060 dB / km. In addition, the coated optical fiber of Comparative Example 6 has a small tear strength at 0 ° C. of 0.3 kg / mm and a small Young's modulus at room temperature of 0.01 kg / mm ^2. Stress fracture was observed, and the loss increment in the 0 ° C. low temperature test was as large as 0.021 dB / km.

As a result of trial production of coated optical fibers under various conditions for the primary layer including Examples 1 to 4 and Comparative Examples 1 to 6, the deterioration of the transmission characteristics at 0 ° C. It was found that the primary layer was caused by destruction or delamination. There was a correlation between the ease of fracture of the primary layer and the tear strength. The tear strength at 0 ° C is 1.0 kg / mm or more, and the adhesive strength at 0 ° C is 10 kg / mm.
By setting it to 0 g / cm or more, it is possible to prevent the primary layer from being broken or peeled against the stress caused by the contraction of the primary layer at a low temperature, and to suppress an increase in transmission loss at a low temperature. did it.

If the tear strength at 0 ° C. is higher than 7.0 kg / mm, the cross-linking density of the resin in the primary layer is high and the Young's modulus is large, so that the loss due to lateral pressure increases. Was. When the Young's modulus of the primary layer was set to a value within the range of 0.03 to 0.10 kg / mm ² , the lateral pressure characteristics could be improved.

If the adhesion at 0 ° C. is too large to exceed 800 g / cm, it is difficult to remove the coating of the coated optical fiber at the time of fusion splicing with another optical fiber. Was. From this, the adhesion at 0 ° C. is 800 g
/ Cm or less was suitable.

Further, as a result of trial production of coated optical fibers under various conditions with respect to glass fibers and evaluation thereof, it was found that dispersion-shifted optical fibers having an effective core area of 60 μm ² or more and having a zero dispersion wavelength in the wavelength band of 1.55 μm were obtained. Even in the case of being weak in bending, good transmission characteristics could be maintained even at low temperatures, and the increase in transmission loss in the lateral pressure test was within an allowable range. Specifically, transmission loss at 0 ° C. and 23
The difference from the transmission loss at 0 ° C. was 0.005 dB / km or less. In addition, the transmission loss increase in the side pressure test was 1.0 dB /
km or less.

[0030]

As described above in detail, according to the present invention, by setting the tear strength at 0 ° C. to 1.0 kg / mm or more and the adhesion at 0 ° C. to 100 g / cm or more, The primary layer can be prevented from being broken or peeled against stress caused by contraction of the primary layer at a low temperature, and an increase in transmission loss at a low temperature can be suppressed. The tear strength at 0 ° C. is set to 7.0 kg / mm or less, and the Young's modulus of the primary layer is set to 0.03 to 0.10 kg / mm.
By setting the value in the range of ² , the lateral pressure characteristics can be improved. Further, the adhesion at 0 ° C. is 800 g / c.
By setting m or less, it is easy to remove the coating of the coated optical fiber.

The effective core area is 60 μm ² or more, has a zero-dispersion wavelength in the 1.55 μm band, and the difference between the transmission loss at 0 ° C. and the transmission loss at 23 ° C. at a wavelength of 1.55 μm. Is 0.005 dB / km or less and the transmission loss increase in the lateral pressure test is 1.0 dB / km or less, so that good transmission characteristics can be maintained even at a low temperature, and the transmission loss in the lateral pressure test can be reduced. Since the increase is within an allowable range, the coated optical fiber is suitably used as an optical transmission line for performing long-distance, high-bit-rate optical communication such as undersea optical communication.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a coated optical fiber according to an embodiment.

FIG. 2 is a table summarizing characteristics and the like in each of Examples 1 to 4 and Comparative Examples 1 to 6.

[Explanation of symbols]

1: coated optical fiber, 11: glass fiber, 12: primary layer, 13: secondary layer.

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Claims (2)

[Claims] 1. A coated optical fiber in which a primary layer and a secondary layer are sequentially coated on an outer periphery of a glass fiber, wherein the primary layer has a Young's modulus at room temperature of 0.03 to 0.03.
0.10 kg / mm ² , and the tear strength at 0 ° C. by the right angle tearing method of JIS K7128 is 1.0 to 7.0.
a coated optical fiber having a weight of 100 kg / mm and an adhesion of said glass fiber at 0 ° C. of 100 to 800 g / cm. 2. An effective core area is 60 μm ² or more, a zero-dispersion wavelength in a wavelength band of 1.55 μm, and a wavelength of 1.0 μm.
A coating characterized in that the difference between the transmission loss at 0 ° C. and the transmission loss at 23 ° C. at 55 μm is 0.005 dB / km or less, and the transmission loss increase in the side pressure test is 1.0 dB / km or less. Optical fiber.