JPH0761885B2 - Coated optical fiber and waterproof optical fiber cable - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coated optical fiber and a coated optical fiber cable, and more particularly to a coated optical fiber and a coated optical fiber cable which are excellent in economy and reliability.

[Prior Art of the Invention and Problems]

It is known that the silica glass constituting the optical fiber undergoes strength reduction due to static fatigue in the presence of water. To prevent this, a plastic protective coating is applied.

Further, the coating material and the coating structure are selected from the viewpoint of such reduction in strength, the transmission loss of the coated optical fiber, and the compatibility with the drawing process of the optical fiber. Two layers, a primary coating having a low modulus and a secondary coating having a high Young's modulus, are formed as protective coatings. At present, a resin composition (hereinafter referred to as a UV material) which is curable by ultraviolet rays and which enables high-speed drawing of an optical fiber because of its fast curing speed is widely used.

By the way, as shown in the following formula, silica glass that constitutes an optical fiber has a Si-O bond hydrolyzed by an alkali (Source: RJ Charles, J. Appl. Phys., Vol. 29, 1554 (198
5)], the network structure of the glass is destroyed.

^{-Si-O-Si + OH -} → -SiOH + -SiO - -SiO + H 2 O → -SiOH + OH - destruction of the network structure is to lead to reduction in the strength of the glass.

On the other hand, an optical fiber cable accommodating a plurality of coated optical fibers is used in various environments, and the cable is often submerged in water in a pipe line or a manhole, which is one of the environments. In order to prevent the strength of the fiber from deteriorating under such an environment, gas maintenance has been put into practice in which dry air is passed through the cable, and a waterproof cable in which a waterproof material is filled in the cable has been put into practical use. However, in gas maintenance, waterproof cables, which are not particularly monitored, are being widely used because of the high cost of gas pressurizing devices and remote monitoring devices. The problem with waterproof cables is that there is no way to detect when a pinhole occurs in the cable. Therefore, when the cable is flooded, it is blocked by the waterproof material in the cable, but it is difficult to completely shield the water and prevent the water from advancing in the length direction of the cable. A known material as a waterproof material is petroleum jelly, but if this is not filled uniformly and without gaps in the cable, water will gradually progress over a long period of time. Thus, full filling of the cable is associated with manufacturing difficulties. Another material is a water-absorbing material that absorbs water to form a dam, but it is difficult to completely shield the fiber because the fiber absorbs water in principle.

As described above, the waterproof cable has a structure that does not significantly infiltrate due to the waterproof material, but it is difficult to protect the fiber or guarantee that water will not infiltrate the fiber surface over a long period (for example, 10 years of cable life). . Therefore, there are problems that the coating material is deteriorated by water and the strength of the fiber itself is reduced. In addition, in the pipes and manholes, the water accumulated in some places is alkaline. It is considered that this is because calcium hydroxide and the like in the concrete were eluted.

However, since UV materials generally contain polar groups such as urethane bond, ether bond, ester bond and hydroxyl group in the molecule, there is a problem that they are hydrolyzed in the presence of alkali. Therefore, the optical fiber coated with such a conventional UV material has a problem that the coating layer is deteriorated in an alkaline atmosphere, and thus the strength is easily reduced. That is, even with a waterproof cable, the coating deteriorates for a long period of time due to the infiltrated alkaline water, and the function of protecting the glass is lost. At the same time, the Si-O bond of the glass is destroyed by moisture in the presence of alkali on the fiber surface,
Strength is reduced. Therefore, it has a serious defect that it cannot essentially serve as a waterproof cable.

The present invention has been made in view of the above points, and an object thereof is to provide a highly reliable coated optical fiber with improved alkali resistance of the optical fiber coating layer, a coated optical fiber tape, and a waterproof fiber cable. is there.

[Means for solving problems]

(Differences Between Features of the Invention and Prior Art) In order to solve the above problems, in the coated optical fiber according to the present invention, in the coated optical fiber having one or a plurality of coating layers, at least one of the coating layers is exposed to ultraviolet rays. It is formed of a cured product of a resin composition that is cured by irradiation, and at least one of the cured products has a water absorption rate of 3.5% or less, and at least one of the cured products having a water absorption rate of 3.5% or less is an average crosslinked product. It is characterized by having an intermolecular weight of 1200 or less.

Further, the tape-shaped coated optical fiber according to the present invention (hereinafter referred to as an optical fiber tape) is a tape in which a plurality of coated optical fibers having one or a plurality of coating layers are arranged substantially parallel to each other and are covered with a tape coating layer to be integrated. In the fiber-shaped coated optical fiber, at least one of the optical fiber coating layer and the tape coating layer is a cured product of a resin composition that is cured by irradiation with ultraviolet rays, and at least one of the cured products.
The water absorption rate is 3.5% or less, and at least one cured product having a water absorption rate of 3.5% or less is characterized by having an average molecular weight between crosslinks of 1200 or less.

Further, the waterproof optical fiber cable according to the present invention is a waterproof optical fiber cable, wherein the optical fiber housed in the waterproof optical fiber cable is a coated optical fiber having one or a plurality of coating layers, and the coating layer of the coated optical fiber. Is formed of a cured product of a resin composition which is cured by irradiation of ultraviolet rays, and at least one of the cured products has a water absorption rate of 3.5% or less, or is housed in the waterproof optical fiber cable. Is a tape-shaped coated optical fiber obtained by arranging a plurality of coated optical fibers having one or a plurality of coating layers substantially in parallel and coating them with a tape coating layer to form an integrated optical fiber tape. At least one layer of the tape coating layer is a cured product of a resin composition that is cured by irradiation of ultraviolet rays, and the cured product At least one water absorption of 3.5%
The following waterproof optical fiber cable is characterized in that at least one of the cured products having a water absorption rate of 3.5% or less has an average molecular weight between crosslinks of 1200 or less. That is, it is characterized by accommodating the coated optical fibers or optical fiber tapes of the first and second inventions according to the present invention.

(Specific Description of the Invention) The present invention will be described in more detail.

As a result of various studies on obtaining a highly reliable optical fiber, in particular, an optical fiber and an optical fiber cable having a small strength reduction even in an alkaline atmosphere, the alkali resistance of the coated optical fiber largely depends on the alkali resistance of the coating layer. Furthermore, the present invention has been achieved by finding that the alkali resistance of the coating material has an extremely high correlation with the water absorption rate and the crosslink density. The details will be described below.

First, a method of evaluating the effects of water absorption and crosslink density will be described.

1. Water Absorption Rate Evaluation Method The water absorption rate was measured by immersing the cured product sheet in distilled water at 23 ° C. for 24 hours, removing the water, wiping off the surface water, and then measuring with a Karl Fischer moisture meter.

The alkali resistance of the cured product was evaluated as follows.

A sheet of the cured product is immersed in a solution of pH 13 (hydrogen ion concentration) 13 (about 0.5% aqueous solution of caustic soda) at 20 ° C or 80 ° C for a predetermined time, then taken out, washed with running water for 2 hours, and then at 23 ° C- The condition was adjusted for 24 hours in an atmosphere of 50% RH (relative humidity), and the Young's modulus was measured by a tensile test. The tensile test was carried out according to JIS standards, and the Young's modulus was calculated from the elongation value of 2.5% of the length of the test piece. The alkali resistance was evaluated by the residual rate of Young's modulus, that is, the value obtained by dividing the Young's modulus of the test piece after immersion by the Young's modulus of the test piece before immersion.

2. Evaluation method of crosslink density The crosslink density was evaluated by the molecular weight between crosslinks. The molecular weight between crosslinks was calculated from the molecular weight and the number of functional groups of the oligomers and monomers that were the raw materials used for the coating material. Since the molecular weight between crosslinks represents the length between the crosslinking points in the network structure of the cured product of the coating material, the smaller the molecular weight between crosslinks, the higher the crosslink density.

3. Evaluation Results of Water Absorption Rate Fig. 1 shows the experimental results of alkali resistance of polytetramethylene glycol urethane acrylate (PTMGUA) materials with different water absorption rates. The alkaline atmosphere is a caustic soda aqueous solution having a pH of 13, and the temperature is 20 ° C. PT used in this experiment
The MGUA-based material was prepared as follows. First, polytetramethylene glycol [HO (CH ₂ CH ₂ CH
₂ CH ₂ O) nH, PTMG] with tolylene diisocyanate and 2-hydroxyethyl acrylate (HEA), and polytetramethylene glycol urethane acrylate (PTMGUA) with HEA or ethylene acrylate (EA), and photopolymerization An initiator was added to form a resin composition, which was then irradiated with ultraviolet rays to prepare a cured product sheet. In the figure, L is a cured product of PTMGUA, M, N, O and P are cured products of a resin composition in which HEA is added to PTMGUA to change the water absorption rate, and R is EA instead of HEA in Q. Resin composition. Therefore, Q and R have similar chemical structures and different water absorption rates. Water absorption of L, M, N, O, P, Q and R is 1.55,
2.26, 3.52, 5.85, 11.60, 1.18 and 1.35%.
Also, since the oligomers used in this experiment are the same and the number of functional groups of the monomers is also the same, the molecular weight between crosslinks of these materials is the same.

From the figure, L (water absorption rate 1.55%), M (2.26%), N (3.52%)
%) And R (1.35%) show almost no change in Young's modulus after being immersed in alkali for 14 days. On the other hand, N (water absorption rate 5.
(85%) swelled by immersion for 3 days, making it impossible to measure Young's modulus. Similarly P (water absorption 11.62%) and Q
(21.18%) swelled one day after immersion in alkali. In addition, R (water absorption 1.35) with a chemical structure very similar to Q
%) Shows almost no deterioration even after soaking in alkali for 14 days.

From the results of this experiment, it can be seen that the alkali resistance of the UV material can be evaluated by the water absorption rate, and that the material having a low water absorption rate has the excellent alkali resistance.

In order to clarify the relationship between this water absorption rate and alkali resistance, various UV materials with different water absorption rates were dipped in an alkaline atmosphere at 80 ℃ -pH13 and subjected to an accelerated test for 30 days. The reason why such severe conditions are selected is that the superiority or inferiority of the material is easily revealed in this atmosphere. Results are shown in FIG.
Water absorption rate can be divided into those that deteriorate at 3.5% and those that do not. From the above experimental results, it can be seen that the alkali resistance of the UV material can be evaluated by the water absorption rate, and if the water absorption rate is 3.5% or less, the alkali resistance is excellent.

The reason why the material having a low water absorption rate is excellent in alkali resistance, that is, the material is less likely to hydrolyze in the presence of alkali, is as follows.
It is widely known that hydrolysis reactions occur on the surface of materials. Therefore, the amount of the alkaline aqueous solution that penetrates into the cured resin sheet, that is, the solubility of the alkaline aqueous solution in the cured product becomes important. Since the alkali concentration is low, this can be regarded as almost the same as the solubility of water in the cured product sheet, that is, the water absorption. Therefore, it is considered that the material with low water absorption had excellent alkali resistance.

4. Evaluation of Crosslink Density Conventional UV materials are generally focused on one of the most important features of UV materials, that is, to accelerate the curing speed. For this purpose, the material needs to have polar groups, and the more such polar groups are, the faster the curing speed tends to be. However, if a large amount of polar groups are contained, the water absorption rate naturally becomes high, so that the conventional UV material had a water absorption rate of about 5%. Therefore, the alkali resistance was not excellent.

Fig. 3 shows the resin composition of PTMGUA (L) with hexamethylene glycol diacrylate (HMGDA) to change the crosslink density. When the resin composition was immersed in an alkaline atmosphere of pH 13-80 ° C for 3 days, the molecular weight between crosslinks and alkali resistance Shows the relationship. The water absorption of the cured product shown in the figure is a low value of 1.40 to 1.55. From this figure, the average molecular weight between cross-links is
It can be seen that if it is 1200 or less, it has excellent alkali resistance.

5. Relationship between Water Absorption Rate and Crosslink Density From the above experimental results, it was found that the water absorption rate and crosslink density influence the alkali resistance of UV materials. That is, when the water absorption is 3.5% or less and the average molecular weight between crosslinks is 1200 or less, the alkali resistance is good. However, it is unclear whether both conditions are necessary. Therefore, the following experiment was conducted.

Fig. 4 shows the resin composition in which hexanemethylene glycol diacrylate (HMGDA) was added to polyethylene glycol urethane diacrylate (PEGDA) to control the crosslink density, and the molecular weight between crosslinks and alkali resistance under the condition of pH13-20 ℃ -3 days. Show the relationship. The numerical value in the parentheses in the figure indicates the water absorption of the cured product. The water absorption of these cured products is 5.2-34.3.
%, Which is a large value. From this figure, it is understood that the one having a higher crosslink density (the one having a lower molecular weight between crosslinks) is superior in alkali resistance. When the above cured product was immersed in an atmosphere of pH 13-80 ° C, it dissolved or expanded within 3 days. Another thing can be seen from these experimental results. That is,
The effect of the crosslink density reaches the ceiling in materials with high water absorption.

Therefore, the average cross-linking molecular weight of 1200 or less is not sufficient, and the average cross-linking molecular weight is 3.5%.
Effective characteristics can be realized only when the following conditions are satisfied.

The effect of such cross-linking density is that the low number means that the number of meshes is small, so even if one chain is cleaved by alkali, the effect on the whole is large, and therefore the mechanical properties are greatly affected. On the contrary, when the crosslink density is high, the number of meshes is large, so that the effect on the whole is small and therefore the effect on the mechanical properties is small. That is, it is considered to have excellent alkali resistance.

The resin composition which is cured by irradiation with ultraviolet rays in the present invention basically comprises a compound having a polymerizable double bond and a photopolymerization initiator (photoinitiator), and has a polymerizable double bond. A plurality of compounds are generally used. Although such a compound is not particularly limited, epoxy acrylate, urethane acrylate, polyester acrylate, acrylic ester, vinyl compound and the like are exemplified.

At least one coating layer of the coated optical fiber according to the first aspect of the present invention is formed of a cured product of a resin composition that is cured by irradiation with ultraviolet rays, and has a water absorption of 3.5% or less and a water absorption of 3.5. % Or less of the cured product has an average molecular weight between crosslinks of 1200 or less.

FIG. 5 shows a structural example of the coated optical fiber according to the present invention.

FIG. 5a discloses an example of a typical coating structure of a coated optical fiber having a single coating layer according to the present invention, in which:
Reference numeral 1 is an optical fiber, and 2 is a coating layer. As is clear from this figure, the coated optical fiber according to the present invention has a structure in which the coating layer 2 is coated around the optical fiber 1,
The coating layer 2 is a cured product of the above-mentioned resin composition that is cured by ultraviolet rays, and has a water absorption of 3.5% or less and an average molecular weight between crosslinks of 1200 or less.

FIG. 5b shows an example of a typical coating structure of a coated optical fiber having a plurality of coating layers according to the present invention, where 3 is a primary coating made of a low Young's modulus material and 4 is a secondary coating made of a high Young's modulus material. It is a coating.

In this coated optical fiber, a structure is disclosed in which the optical fiber 1 is provided with a primary coating made of a low Young's modulus material, and the primary coating 3 is further provided with a secondary coating made of a high Young's modulus material. . In this example, two layers of coating are provided, of which at least one
The layer is a cured product of a resin composition that is cured by ultraviolet rays, and at least one layer, that is, at least one layer of the primary coating 3 and the secondary coating 4 has a water absorption of 3.5% or less and an average molecular weight between crosslinks of 1200. It is as follows. Of course, both the primary coating 3 and the secondary coating 4 may be a cured product having a water absorption of 3.5% or less and an average molecular weight between crosslinks of 1200 or less.

In FIG. 5B, the case where the coating layer is two layers is illustrated, but when there are two or more coating layers, at least one of the coating layers is cured with a resin composition that is cured by ultraviolet rays. Of which at least one layer has water absorption
Obviously, it may be 3.5% or less and the average molecular weight between crosslinks is 1200 or less.

FIG. 5c is a diagram showing an example of the coated optical fiber tape which is the second invention according to the present invention.
The structural example of the optical fiber tape in which five optical fibers having the coating structure as shown in FIG.
In the figure, 5 indicates a tape coating layer made of a high Young's modulus material.

According to this optical fiber tape, at least one layer of the primary coating 3, the secondary coating 4 and the tape coating 5 is
A cured product of an ultraviolet curable resin composition, at least one layer of which has a water absorption of 3.5% or less,
The average cross-linking molecular weight is 1200 or less.

FIG. 5d shows an optical unit consisting of 6 cores of the coated optical fiber as shown in FIG. 5b, and FIG. 5e shows an example of a waterproof optical fiber cable structure according to the third invention of the present invention.
In the figure, 6 is a coated optical fiber, 7 is a metal center member, 8 is a cushion layer made of water-absorbing fibers, 9 is a press-wrap, 10 is an optical unit, 11 is a tensile member, 12 is a press-wrap tape, and 13 is a jacket. is there.

As is apparent from FIG. 5e, in the waterproof optical fiber cable, the optical unit 10 as shown in FIG. 5d is arranged around the strength member 11 and is integrated with the press-wrap tape 12 and the jacket 13. It is a thing. The absorbing fiber 8 in the optical unit 10 absorbs water from the pinhole generated in the outer cover 13 and expands to make a dam.

As described above, the coating of the coated optical fiber used for such a waterproof optical fiber cable is formed of a cured product of a resin composition that is cured by irradiation of ultraviolet rays, and the water absorption rate of the coating layer is 3.5. % And the average molecular weight between crosslinks is 1200 or less. Further, the coated optical fiber forming the waterproof optical fiber cable may have a plurality of coating layers. That is, it has two or more coating layers of the same kind or different kinds, and at least one of the coating layers is formed of a cured product of a resin composition which is cured by irradiation of ultraviolet rays, and at least one of the coating layers is Water absorption of the coating layer is 3.5% or less, and the average molecular weight between crosslinks is 1
It is a cured product of 200 or less.

Examples will be described below, but unless otherwise specified, the alkali resistance of the UV material was evaluated by the method for examining the residual Young's modulus as described above. That is, the optical fiber is immersed in an aqueous solution of pH 13 at 80 ° C for a predetermined time and then taken out
The tensile test was performed as it was. In the tensile test, the gauge length was 40 cm, and the tensile speed was 20% / min of the gauge length.

Example 1 A urethane acrylate X having a Young's modulus of the cured product of 60 kg / mm ² , a water absorption rate of 2.3% and an average molecular weight between crosslinks of 250 was prepared and irradiated with ultraviolet rays to obtain a cured product having a thickness of 200 μm. Got the sheet. This was immersed in an alkaline solution at 80 ° C-pH 13 and the change in Young's modulus with time was measured. Results are shown in FIG. No significant change in Young's modulus was observed even after 30 days.

Next, an optical fiber having an outer diameter of 125 μm was coated with urethane acrylate S having a water absorption rate of 2.5% and Young's modulus of 0.12 kg / mm ² to a thickness of about 40 μm on the coating of the first layer, and urethane acrylate X was further coated thereon. Coated to a thickness of about 100 μm, outer diameter of about 0.4
A coated optical fiber of mm was obtained. This optical fiber is 80 ℃ -pH
It was dipped in the alkaline solution of 13 and the time-dependent change of the fiber strength was measured. The results are shown in Fig. 7. The fiber strength gradually decreases, but no extreme decrease is observed.

Next, the life estimation of the coating material used in this example was considered as follows. PH of urethane acrylate X sheet
The change in Young's modulus with time was measured by changing the temperature in 13 alkaline atmospheres. The life of the material (tf) was defined as the time at which the residual Young's modulus reached 0.8, and the relationship between tf and temperature was plotted by Arrhenius plot, and the life at room temperature was estimated from this line. The results are shown in Fig. 8. Urethane acrylate X 20 ℃ -pH
Life expectancy at 13 is estimated to be about 4400 days (about 12 years).

For comparison, the same examination was performed on conventional coating materials. A commercially available urethane acrylate Y (Young's modulus of the cured product is 62 kg / mm ² , water absorption is 3.9%) is irradiated with ultraviolet rays to give a thickness of 2
A cured product sheet of 00 μm was obtained. This was immersed in an alkaline solution at 80 ° C-pH 13 and the change in Young's modulus with time was measured.
The results are also shown in FIG. Almost no change was observed up to 3 days of alkali immersion, but the sheet was dissolved on the 7th day, and the Young's modulus could not be measured.

Next, an optical fiber having an outer diameter of 125 μm was coated with urethane acrylate S on the first layer to a thickness of about 40 μm, and urethane acrylate Y was further coated on the first layer to a thickness of about 100 μm. A coated optical fiber was obtained. This optical fiber was dipped in an alkaline solution at 80 ℃ -pH13, and the change in fiber strength with time was measured. The results are also shown in FIG. The fiber strength gradually decreased until 3 days, and the coating layer was dissolved on the 7th day, and the strength could not be measured.

The life of the urethane acrylate Y sheet was estimated by the same method as above. The results are shown in Fig. 8. The lifespan of urethane acrylate Y at 20 ° C-pH 13 is estimated to be about 380 days (about 1 year).

Example 2 An optical fiber having a first layer coated with urethane acrylate S and a second layer coated with urethane acrylate X was manufactured, and a 60-fiber waterproof optical fiber cable was manufactured using this coated optical fiber. Put this cable in alkaline solution of 80 ℃ -pH13
After soaking for 30 days, it was taken out and the strength of the coated optical fiber was measured. The average breaking strength was 78% of the initial value, which was as good as or higher than the alkali resistance of the coated optical fiber.

[Example 3] A polyolefin urethane diacrylate (oligomer) having a molecular weight of 2600 (calculated value) was obtained by reacting a polyolefin diol having a molecular weight of 2000, tolylene diisocyanate, and 2-hydroxyethyl acrylate. N to this
-Vinyl-2-pyrrolidone (monomer) and a photoinitiator were added to obtain a resin composition. The water absorption of the resin composition was adjusted by changing the molar ratio of the monomer and the oligomer. The alkali resistance of the sheet prepared by irradiating the resin composition with ultraviolet rays was evaluated. FIG. 9 shows the Young's modulus residual ratio after immersion in an alkaline atmosphere at pH 13-80 ° C. for 7 days. Water absorption rate about 3.5%
It can be seen that the remaining Young's modulus is high below the boundary.

〔The invention's effect〕

As described above, according to the present invention, since it has a UV material having a low water absorption rate and a low crosslink density as a coating layer, the coated optical fiber and the optical fiber cable have excellent alkali resistance, and since they are UV materials, they are cured during drawing. It is easy to perform, and there is an advantage that it is economical because it does not need to change the conventional drawing technique.

[Brief description of drawings]

Figure 1 shows the relationship between water absorption and alkali resistance of PTMGUA resin composition, with the horizontal axis representing time (days) and the vertical axis representing 20 ° C.
-Residual percentage of Young's modulus of UV material after immersion in pH13 alkaline atmosphere, Fig. 2 is a graph showing the relationship between water absorption and alkali resistance of UV material, the vertical axis is 80 ℃ -pH13 atmosphere inside
Residual Young's modulus of UV material soaked for 30 days, Fig. 3 shows PTMG
FIG. 3 is a diagram showing the relationship between the crosslink density and alkali resistance of a UA resin composition, where the horizontal axis represents the average molecular weight between crosslinks of the resin composition and the vertical axis represents the average molecular weight after immersion in an alkaline atmosphere of pH 13-80 ° C. for 3 days. Residual Young's modulus, Fig. 4 shows pH 13-20 of polyethylene glycol urethane diacrylate (PEGUA) resin composition
It is a diagram showing the relationship between the crosslink density and alkali resistance under the condition of ℃ -3 days, the vertical axis shows the Young's modulus residual rate, the horizontal axis shows the molecular weight between crosslinks, and the numerical value in the figure shows the water absorption rate. FIGS. 5A, 5B and 5C are views showing an example of a coating structure of an optical fiber according to the present invention,
Fig. D is an optical unit, Fig. 5e is a diagram showing an example of the structure of an optical fiber cable, and Fig. 6 is two types of urethane acrylates X (water absorption rate 2.3%) and Y (water absorption rate 3.9%) at 80 ° C- pH13
FIG. 7 is a graph showing a change in Young's modulus with time in an alkaline atmosphere, where the vertical axis represents the Young's modulus residual rate, the horizontal axis represents time, and
The figure shows S / X coated optical fiber and S / Y coated optical fiber 80
It is a figure showing the change with time of the strength in an alkaline atmosphere of ℃ -pH13, the vertical axis is the residual ratio of strength, the horizontal axis is the time,
The figure shows two types of urethane acrylate X (water absorption 2.3%,
250) Average lifetime molecular weight between crosslinks), Y (water absorption 3.9%, average molecular weight between crosslinks unknown) shows the life estimation curve at pH 13, the vertical axis is the lifetime, the horizontal axis is the temperature (the reciprocal of absolute temperature multiplied by 10 ³ ). FIG. 9 is a diagram showing the relationship between the water absorption rate and the Young's modulus residual rate, in which the vertical axis represents the Young's modulus residual rate and the horizontal axis represents the water absorption rate. 1 ... Optical fiber, 2 ... Coating, 3 ... Primary coating made of constant Young's modulus material, 4 ... Secondary coating made of high Young's modulus material, 5 ... Tape coating made of high Young's modulus material , 6 ... Coated optical fiber, 7 ... Metal center member, 8 ...
... Cushion layer made of water-absorbent fiber, 9 ... Presser roll, 10
...... Optical unit, 11 …… Tensile body, 12 …… Presser winding tape, 13 …… Coating.

Claims (3)

[Claims] 1. A coated optical fiber having one or a plurality of coating layers, wherein at least one of the coating layers is formed of a cured product of a resin composition which is cured by irradiation of ultraviolet rays, and at least the cured product. A coated optical fiber having a water absorption of 3.5% or less and at least one cured product having a water absorption of 3.5% or less has an average molecular weight between crosslinks of 1200 or less. 2. A tape-shaped coated optical fiber obtained by arranging a plurality of coated optical fibers having one or a plurality of coating layers substantially in parallel and coating them with a tape coating layer to integrate them.
At least one layer of the optical fiber coating layer and the tape coating layer is a cured product of a resin composition that is cured by irradiation with ultraviolet rays, and at least one water absorption rate of the cured product is 3.5% or less, and the water absorption At least one cured product having a rate of 3.5% or less has an average molecular weight between crosslinks of 1200 or less. 3. A waterproof optical fiber cable, wherein the optical fiber accommodated in the waterproof optical fiber cable is a coated optical fiber having one or a plurality of coating layers, and at least one layer of the coating layers of the coated optical fiber is An optical fiber tape formed of a cured product of a resin composition that is cured by irradiation with ultraviolet rays, and at least one of the cured products has a water absorption rate of 3.5% or less, or an optical fiber tape accommodated in the waterproof optical fiber cable. A tape-shaped coated optical fiber obtained by arranging a plurality of coated optical fibers having one or a plurality of coating layers substantially parallel to each other and coating them with a tape coating layer to integrate the optical fiber coating layer and the tape coating layer. , At least one layer is a cured product of a resin composition which is cured by irradiation with ultraviolet rays, and at least one water absorption rate of the cured product is 3.5% or more. A waterproof optical fiber cable is waterproof optical fiber cable at least one average molecular weight between crosslinks of the water absorbing rate of 3.5% or less of the cured product, characterized in that it is 1200 or less.