JP2000241680A - Coated optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated optical fiber of low transmission loss, excellent in a side pressure characteristic and a separation-resistant characteristic, and to allow application for an optical fiber, in particular a distributed shift type optical fiber, having a large effective cross-sectional area for a long distance and high pit rate communication weak in bending. SOLUTION: This coated optical fiber is coated with a flexible ultraviolet curing type resin layer (primary resin layer) 2 and a rigid ultraviolet curing resin layer (secondary resin layer) 3 in an outer circumference of an optical fiber 1 comprising silica glass, (a) a coating outside diameter is about 250 μm, (b) a ratio of a Young's modulus (kg/mm2) of the primary resin layer 2 to its film thickness (mm) is 0.7-1.5, (c) a product of a Young's modulus (kg/mm2) and a film thickness (mm) of the secondary layer 3 is 2.5-5.0, and (d) a glass transition point of the secondary resin layer 3 is 70-90 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved coated optical fiber used for optical communication, and more particularly to an improved coated resin layer.

[0002]

2. Description of the Related Art Conventionally, various optical fibers have been known as coated optical fibers used for optical communication. For example, Japanese Patent Application Laid-Open No. 8-24250 discloses that 1.0 to 3.0.
A coated optical fiber is described in which a primary resin layer having a Young's modulus of 0 Mpa and a glass transition point of −10 ° C. or less and a secondary resin layer having a Young's modulus of 400 Mpa or more are coated. Japanese Patent Application Laid-Open No. 1-133011 discloses that a Young's modulus of 0.1 to 10 Mpa and a coating thickness of 5 to 2
A coated optical fiber is described in which a primary resin layer of 0 μm and a secondary resin layer having a Young's modulus of 1000 Mpa or more are coated.

However, in the coated optical fiber described in Japanese Patent Application Laid-Open No. H8-24250, when the Young's modulus of the primary resin layer is 1.0 to 3.0 Mpa, the lateral pressure characteristics are insufficient, and the fiber is wound around a bobbin. The transmission characteristics of the optical fiber unit after the optical fiber unit is deteriorated. The reason is that in recent years,
Dispersion-shifted fibers with a large effective area are used for high bit rate communication.However, these optical fibers are vulnerable to bending, and are not suitable for single-mode optical fibers used in the past. Even when an excessive lateral pressure occurs, the transmission characteristics are degraded by micropending.

[0004] In the coated optical fiber described in Japanese Patent Application Laid-Open No. 1-133011, the transmission loss is degraded because a secondary resin layer having 1000 Mpa or more is used. This shrinks when the secondary resin layer hardens, but when the Young's modulus is large, the stress (curing shrinkage force) accompanying this shrinkage also increases. For this reason, the glass is meandered in the longitudinal direction, and the transmission characteristics deteriorate due to bending loss.

Further, when a primary resin layer having a Young's modulus of the order of 0.1 Mpa is used, the interface between the glass and the primary resin may be peeled off when the coated optical fiber is wound or when a force is applied from the outside in a unitization process or the like. It has been found that a problem that the resin coating is easily broken is caused.

[0006] Such a peeling occurrence mechanism will be described. That is, when a foreign substance (such as dust in a pass line of an optical fiber unit manufacturing apparatus) is pressed against the coated optical fiber, the coating is deformed into an elliptical shape at that portion. The primary resin is compressed in the direction in which the foreign matter is pressed, but is expanded in the direction perpendicular to that direction. At this time, in the stretching direction, a force is generated to separate the primary resin from the glass, and as a result, peeling occurs. Resin destruction refers to a phenomenon in which when the adhesion between glass and the primary resin is strong, the primary resin itself is destroyed instead of peeling off. In each case, since the primary resin is softer than that conventionally used, the amount of deformation is increased, and as a result, the primary resin is more likely to occur.

[0007]

Means for Solving the Problems In the coated optical fiber, the present inventors have found that (a) the coating outer diameter is about 250 μm, and (b) the ratio between the Young's modulus and the film thickness of the primary resin layer is 0.7 to 1 .
5. (c) The product of the Young's modulus and the film thickness of the secondary resin layer is 2.
5 to 5.0, (d) the glass transition point of the secondary resin layer is 7
It has been found that when the temperature is 0 to 90 ° C., the lateral pressure characteristics, the peeling resistance characteristics, and the mechanical characteristics can be improved, and the present invention has been completed. That is, the present invention comprises: an outer periphery of an optical fiber made of quartz glass coated with a soft ultraviolet-curable resin layer (primary resin layer) and a hard ultraviolet-curable resin (secondary resin layer); In the coated optical fiber having a diameter of about 250 μm, (b) the ratio of the Young's modulus (kg / mm ² ) to the film thickness (mm) of the primary resin layer is 0.7 to 1.
(C) the Young's modulus of the secondary resin layer (kg /
mm ² ) and the film thickness (mm) are ^2.5 to 5.0,
And (d) the glass transition point of the secondary resin layer is 70 to 9
Provide a coated optical fiber that is at 0 ° C.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram illustrating a process of manufacturing a coated optical fiber. FIG. 2 is a schematic diagram showing a cross-sectional structure of the coated optical fiber of the present invention. FIG. 3 is a schematic diagram showing a cross-sectional structure of an optical fiber unit in which the coated optical fiber of the present invention is arranged. In FIGS. 1 to 3, 1 is a (bare) optical fiber, 2 is a primary resin layer, 3 is a secondary resin layer,
4 is an optical fiber preform, 5 is a drawing furnace, 6 is a primary resin coating device, 6 'is a secondary resin coating device, 7, 7'
Is an ultraviolet irradiation lamp, 8 and 8 'are cylindrical bodies, 9 and 9' are ultraviolet irradiation devices, 10 and 10 'are reflection mirrors, 11 is a coated optical fiber, 12 is a winding machine, 15 is a central tensile strength member, 16 Denotes an ultraviolet-curable resin inner layer, and 17 denotes an ultraviolet-curable resin jacket.

[0009] The coated optical fiber of the present invention comprises an optical fiber made of quartz glass coated with a soft ultraviolet-curable resin layer (primary resin layer) and a hard ultraviolet-curable resin (secondary resin layer). (a) Coating outer diameter is about 25
In the coated optical fiber having a thickness of 0 μm, (b) the ratio of the Young's modulus (kg / mm ² ) to the film thickness (mm) of the primary resin layer is 0.7 to 1.5, and (c) the secondary resin layer Product of Young's modulus (kg / mm ² ) and film thickness (mm) is 2.5
To 5.0 and (d) the glass transition point of the secondary resin layer is 70 to 90 ° C.

(I) For the primary resin layer, it is desirable to use a soft (it means a resin having a Young's modulus of 1 kg / mm ² or less) ultraviolet-curable resin. The thickness of the primary resin layer may usually be about 20 to 60 μm. The primary resin is preferably a polyether or polyester urethane acrylate, and may contain a reactive diluent monomer and a photoinitiator as needed.

[0011] Reactive diluent monomers include N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylacetamide, methoxyethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, aromatic polyethylene glycol monoacrylate, and phenoxyethyl. (Meth) acrylate, phenoxypolypropylene (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl acrylate, isobornyloxyethyl (meth) acrylate, morpholine (meth) acrylate, etc. Functional compound; 2,2
-Dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate di (meth) acrylate, ethylene glycol di (meth) acrylate,
Propylene glycol di (meth) acrylate, 1,4
-Butanediol di (meth) acrylate, di (meth) acrylate of ethylene oxide adduct of bisphenol A, di (meth) acrylate of 2,2-di (hydroxyethoxyphenyl) propane, di (meth) tricyclodecane dimethylol A) bifunctional compounds such as acrylate and dicyclopentadiene di (meth) acrylate; and these may be used alone or in combination of two or more.

Known photoinitiators can be used, for example, 1-hydroxy-cyclohexyl-phenylketone, 2,2-dimethoxy-2-phenylacetophenone, phenylacetophenone diethylketal, alkoxyacetophenone, benzylmethylketal, benzophenone. And phenones such as 2-hydroxy-2-methylpropiophenone; 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide and the like. Examples thereof include phosphine oxide derivatives, and these may be used alone or in combination of two or more.

In this case, the Young's modulus of the primary resin layer was adjusted, for example, by the molecular weight of the polyether portion of the ultraviolet curable resin and the type of the diluting monomer. That is, in the primary resin layer, the Young's modulus can be reduced by increasing the molecular weight of the polyether portion and selecting a linear monofunctional diluent monomer having a large molecular weight.

(Ii) It is desirable to use a hard (it has a Young's modulus of 10 kg / mm ² or more) ultraviolet curing resin for the secondary resin layer. The thickness of the secondary resin layer may usually be about 20 to 60 μm. It is preferable to use a polyether-based or polyester-based urethane acrylate as the secondary resin, and may include a reactive diluent monomer and a photoinitiator as needed. That is, the secondary resin layer, by reducing the molecular weight of the polyester or polyether portion, by increasing the urethane group concentration, and by selecting a monomer having a rigid molecular structure such as a benzene ring or a polyfunctional monomer to increase the Young's modulus. Can be bigger.

As reactive diluent monomers, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylacetamide, methoxyethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate,
Phenoxypolypropylene (meth) acrylate, 2-
Monofunctional compounds such as hydroxypropyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isobornyloxyethyl (meth) acrylate, and morpholine (meth) acrylate; 2,2-dimethyl-3-hydroxypropyl-2, Di (meth) acrylate of 2-dimethyl-3-hydroxypropionate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, ethylene oxide of bisphenol A Di (meth) acrylate of adduct, di (meth) of 2,2-di (hydroxyethoxyphenyl) propane
Bifunctional compounds such as acrylate, di (meth) acrylate of tricyclodecane dimethylol, and dicyclopentadiene di (meth) acrylate; trimethylolpropane tri (meth) acrylate, trimethylolpropane trioxyethyl (meth) acrylate, penta Polyfunctional compounds such as erythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trihydroxyethyl isocyanuric acid tri (meth) acrylate, tris (acryloxymethyl) isocyanurate and triallyl isocyanurate; These may be used alone or in combination of two or more.

Known photoinitiators can be used, for example, 1-hydroxy-cyclohexyl-phenylketone, 2,2-dimethoxy-2-phenylacetophenone, phenylacetophenone diethylketal, alkoxyacetophenone, benzylmethylketal, benzophenone. Phenones such as 2-hydroxy-2-methylpropiophenone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide; Examples thereof include phosphine oxide derivatives, and these may be used alone or in combination of two or more.

The Young's modulus and the glass transition point of the secondary resin layer were adjusted by the type and amount of the ultraviolet curable resin as the oligomer and the reactive diluent monomer. That is,
The Young's modulus and the glass transition point can be increased by reducing the molecular weight of the oligomer that is the raw material of the secondary resin layer, or by increasing the rigidity of the urethane portion of the secondary resin. Further, by increasing the content of the urethane portion, the Young's modulus can be increased while suppressing an increase in the glass transition point. The Young's modulus and the glass transition point can be increased by increasing the blending amount of the polyfunctional monomer or selecting a monomer having high rigidity as the reactive diluent monomer.

[0018]

(1) The coated optical fiber of the present invention has a coating outer diameter of about 250 μm (specifically, in the range of 235 to 255 μm).
Otherwise, the compatibility with the general optical fiber becomes poor, for example, because it is different from the global standard, and the connection with general optical fibers becomes difficult. (2) In the coated optical fiber as in the present invention, it is effective to reduce the Young's modulus and increase the film thickness of the primary resin layer in order to improve the lateral pressure characteristics of the optical fiber. This is because the cushion effect increases.
However, when the Young's modulus of the primary resin layer is small (specifically, less than 0.02 kg / mm ² ), it is necessary to extremely reduce the crosslinking density of the resin, and the durability of the resin decreases. In addition, when the thickness of the primary resin layer is increased, the amount of deformation of the primary resin layer is increased, and the thickness of the secondary resin layer is relatively reduced, so that resistance to external force is reduced. The force acting on the interface between the glass and the primary resin layer increases, and peeling or resin breakage easily occurs. The present inventors have found that when the ratio of the Young's modulus to the film thickness of the primary resin layer is 0.7 to 1.5, preferably 0.8 to 1.3, the lateral pressure characteristics and the peeling resistance can be maintained. Was.

(3) In the coated optical fiber of the present invention, it is effective to increase the Young's modulus and the film thickness of the secondary resin layer in order to improve the lateral pressure characteristics and the peeling resistance. is there. This is because it is difficult for the secondary resin layer to transmit stress to the coating layer and the glass by resisting external stress. However, when the Young's modulus and the film thickness increase, the curing shrinkage force when the resin cures increases, and the transmission loss in which the optical fiber does not meander in the longitudinal direction increases. The present inventors have proposed that the product of the Young's modulus and the film thickness of the secondary resin layer is 2.5 to 5.0, and preferably 3.0 in order to improve the lateral pressure characteristics and the peeling resistance and not to deteriorate the transmission characteristics. It has been found that 0 to 4.0 is good.

(4) In the coated optical fiber of the present invention, the glass transition point of the secondary resin layer is 70 ° C.
If the temperature is less than about 70 ° C., the Young's modulus of the resin is significantly reduced at about 70 ° C., so that the temperature characteristics after the unitization is deteriorated. On the other hand, when the temperature exceeds 90 ° C., when the resin is cured, residual stress in the primary resin layer caused by a difference in linear expansion coefficient between the primary resin layer and the secondary resin layer becomes large, and the peeling resistance decreases. The present inventors have found that the glass transition point of the secondary resin layer needs to be 70 to 90 ° C., preferably 75 to 85 ° C. in order to improve mechanical properties, particularly toughness and peel resistance. Was found.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below, but they do not limit the scope of the present invention. (Evaluation method) (1) Transmission loss after trial production: OTDR wound around bobbin
(Abbreviation of Optical Time Domain Reflectometer) was used to measure the transmission loss. The wavelength at that time is 1.55 μm. (2) Lateral pressure characteristics: The coated optical fiber wound on the bobbin is
Tension 1 on the bobbin wrapped with No. 000 sandpaper
Wound 600 m at 00 g, bundled at 1000 m, 1.55 μm wavelength with OTDR in each state
The transmission loss at m was measured. The difference between the former transmission loss and the latter transmission loss was defined as an increase in the transmission loss due to the lateral pressure test.

(3) Peeling test: The coated optical fiber is wound around using a 240 mm diameter roller provided with a 0.2 mm diameter pin. The tension when passing through the roller is 500
g, the rewinding linear speed is 1 m / s. After rewinding, the coated optical fiber is observed with a microscope in the longitudinal direction under a microscope to check for peeling or resin breakage. In addition, 25 places where the pins contacted are observed, and the ratio of occurrences is obtained.

(4) Young's modulus: For the primary resin, a push-in-modulus method (issued in 1994, IW
CS, vol. 43, p. 552) was used to directly evaluate the Young's modulus of a coated optical fiber prototype. This is because the primary resin generally has a lower Young's modulus when fiberized than a Young's modulus measured with a film. This is because in an ultraviolet irradiation device used for a drawing device, the temperature becomes high due to radiant heat and heat due to a curing reaction, and chain transfer and termination reaction become dominant, so that crosslinking does not proceed. Therefore,
As for the Young's modulus of the primary resin of the coated optical fiber, the value in the coated optical fiber is important. A method of measuring the state of a coated optical fiber by measuring the Young's modulus of a primary resin is described in the in-site modulus method (issued in 1985, OFC
20) are also known. The Young's modulus of the secondary resin was evaluated by taking a sample from the coated optical fiber prepared by the following method.

(5) Glass transition point: The glass transition point of the secondary resin was measured by a dynamic viscoelasticity meter using a sample having a predetermined Young's modulus prepared using the drawing apparatus shown in FIG. The measured wave number was 11 Hz, and the maximum value of the loss tangent was defined as the glass transition point. (6) Heat cycle test: In this test, a sample of 1000 m was bundled into a bundle having a diameter of about 30 cm, and placed in a thermostat.
OTDR (measurement wavelength 1.
55 μm).

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical fiber preform 4 is drawn by a drawing furnace 5 into an optical fiber 1 using a drawing apparatus shown in FIG. 1, and a primary resin coating device 6 and a secondary resin coating device 6 'are applied to the optical fiber 1. After the coating, the coated optical fiber 11 having the structure shown in FIG. 2 was obtained by curing with the ultraviolet irradiation devices 9 and 9 ′, respectively. The tension at the time of winding was 50 g. As the optical fiber, a dispersion-type soft fiber having an effective area of 85 μm ² having a double-core profile was used, and the physical properties of the primary resin layer 2 and the secondary resin layer 3 were adjusted as follows.

The thickness of each coating layer is as shown in Tables 1 and 2. Each coated optical fiber was prototyped 5 km at a time. The coated optical fiber is cut to a length of several tens of cm, immersed in acetone, swelled, and a pipe-shaped coating is removed from glass. After drying, the measurement was performed at a mark of 25 mm and a tensile speed of 1 mm / min. Table 1 shows the evaluation results of the prototype coated optical fiber.
It is shown in FIG. An optical fiber unit shown in FIG. 3 was prepared using these coated optical fibers.

[0027]

[Table 1]

[0028]

[Table 2]

(Note) The primary resins used in Examples and Comparative Examples are as follows. P series: mainly composed of polyether type urethane acrylate having an average molecular weight of 4,000 to 10,000 obtained by polymerization of polypropylene glycol, tolylene diisocyanate and hydroxyethyl acrylate, and N-vinylpyrrolidone and aromatic polyethylene glycol as reactive diluent monomers Monoacrylate and lauryl acrylate were added at 3 to 20% by weight, respectively, and the molecular weight and the amount of the reactive diluent monomer were adjusted so as to obtain a predetermined Young's modulus. Secondary resins used in Examples and Comparative Examples are as follows. S series: mainly composed of polyether type urethane acrylate having an average molecular weight of 2,000 to 6,000 obtained by polymerization of polytetraethylene glycol, tolylene diisocyanate, and hydroxyethyl acrylate, and N-vinylpyrrolidone and ethylene glycol as reactive diluent monomers Diacrylate and trihydroxyethyl isocyanurate triacrylate were added in an amount of 5 to 50% by weight, respectively, and the molecular weight and the amount of the reactive diluent monomer added were adjusted so as to obtain a predetermined Young's modulus.

According to Tables 1 and 2, the coated optical fiber of the embodiment had a stable transmission loss after the unit was made.
The coated optical fiber of the comparative example is 0.05d
This indicates an increase in transmission loss of B / km or more, confirming that the transmission loss is unstable. Further, these prototype units were subjected to a heat cycle test at −20 to 70 ° C., and transmission loss was measured at each temperature with OTDR (measurement wavelength: 1.55 μm). As a result, the prototype unit using the coated optical fiber of the example showed a stable transmission loss characteristic of 0.03 dB / km or less. 133dB / km
Showed a loss increase.

[0031]

As described above, according to the coated optical fiber of the present invention, a coated optical fiber having a low transmission loss can be obtained, and at the same time, the improvement of the lateral pressure characteristic and the improvement of the peeling resistance can be realized. Therefore, it is particularly effective when applied to a dispersion-shifted optical fiber having a large effective area, particularly an effective area of 60 μm ² or more, for long distance and high bit rate communication that is weak to bending.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a process of manufacturing a coated optical fiber.

FIG. 2 is a schematic view showing a cross-sectional structure of a coated optical fiber of the present invention.

FIG. 3 is a schematic view showing a cross-sectional structure of an optical fiber unit in which a coated optical fiber of the present invention is arranged.

[Explanation of symbols]

 Reference Signs List 1 (naked) optical fiber 2 Primary resin layer 3 Secondary resin layer 4 Optical fiber preform 5 Drawing furnace 6 Primary resin coating device 6 'Secondary resin coating device 7, 7' Ultraviolet irradiation lamp 8, 8 'Cylindrical body 9, 9 'Ultraviolet irradiation device 10, 10' Reflecting mirror 11 Coated optical fiber 12 Winder 15 Central tensile strength member 16 Ultraviolet-curable resin inner layer 17 Ultraviolet-curable resin jacket

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshihisa Sato 1 Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Kazuya Kuwahara 1-Tagamachi, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo (72) Inventor Eiji Sasaoka, Inventor Eiji Sasaoka, Kanagawa Prefecture, Yokohama, 1st place, Tayacho, Yokohama, Japan Sumitomo Electric Industries, Ltd. Yokohama Factory (72) Inventor, Masashi Onishi 1, Tayamachi, Sakae-ku, Yokohama, Kanagawa, Japan Sumitomo Electric Industrial Co., Ltd. Yokohama Works F-term (reference) 2H050 BA32 BB07Q BB07S BB13Q BB13S BB14Q BB14S BB17Q BB17S BB31Q BB31S BB33Q BB33S BC03 BD00 BD07 4G060 AA03 AA06 AC02 AC10 AC15 CB09

Claims (1)

[Claims] 1. An outer periphery of an optical fiber made of quartz glass is coated with a soft UV-curable resin layer (primary resin layer) and a hard UV-curable resin (secondary resin layer). (B) the ratio of the Young's modulus (kg / mm ² ) to the film thickness (mm) of the primary resin layer is 0.7 to 1.5; The product of the Young's modulus (kg / mm ² ) and the film thickness (mm) of the resin layer is ^2.5 to 5.0, and (d) the glass transition point of the secondary resin layer is 70 to 90 ° C.
A coated optical fiber, characterized in that: