JP2015199626A - Optical fiber wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber wire capable of suppressing a plasticizer from transiting toward a coating layer formed on an outer periphery of an optical fiber, from a resin material including the plasticizer disposed in the vicinity, suppressing peeling between the optical fiber and coating layer even when being exposed to high temperature, and maintaining preferable side pressure transmission characteristic.SOLUTION: Provided is an optical fiber wire 10 having a coating layer 12 contacting an outer periphery of an optical fiber 11 and formed of crosslinked resin having equilibrium modulus of 10 MPa or more at 150°C. The crosslinked resin forming the coating layer 12 has equilibrium modulus of 50 MPa or less at 150°C. The layer coating the outer periphery of the optical fiber is formed of only the coating layer 12.

Description

  The present invention relates to an optical fiber, and more particularly to an optical fiber in which a coating layer made of a resin material is provided on the outer periphery of an optical fiber.

  Optical fibers are used for various purposes such as information communication in automobiles because they can perform high-speed communication of a large amount of information. In general, the optical fiber is used in the form of an optical fiber in which a coating layer made of a resin material such as an ultraviolet curable resin is formed on the outer periphery.

  FIG. 4 shows a cross-sectional structure of a conventional general optical fiber 90. Usually, the coating layer 92 formed on the outer periphery of the optical fiber 91 has a two-layer structure of a primary layer 92a disposed on the inner side and a secondary layer 92b disposed on the outer side. The primary layer 92a is made of a soft material having a relatively low Young's modulus, and the secondary layer 92b is made of a hard material having a relatively high Young's modulus. Thus, by coating the outer periphery of the optical fiber with two types of layers having different Young's moduli, both the microbend loss due to the side pressure and the macrobend loss due to bending or the like can be effectively reduced. The primary layer 92a contributes particularly to the reduction of microbend loss. An optical fiber 90 having this type of primary layer 92a and secondary layer 92b is disclosed in, for example, Patent Document 1 below.

JP 2001-10874 A

  When the optical fiber 90 as described above is used for short-distance communication in a vehicle, a so-called tight coat formed by adhering a protective layer made of polyvinyl chloride (PVC) to the outer periphery of the optical fiber 90 It is often used in the form of an optical fiber cord having a structure, or in the form of an optical fiber cord having a so-called loose tube structure in which an optical fiber 90 is housed in a PVC tube together with a tensile body such as Kevlar fiber. Generally, a plasticizer is added to PVC used for these applications for the purpose of ensuring flexibility. When PVC containing a plasticizer is in contact with the coating layer 92 or placed in the vicinity of the coating layer 92 and is heated for a long time in an on-vehicle environment, the plasticizer may move to the coating layer 92. There is. In particular, the primary layer 92a made of a soft material easily swells by absorbing a plasticizer. Due to the swelling and thermal aging of the primary layer 92a, the adhesive force at the interface between the primary layer 92a and the optical fiber 91 may be extremely reduced, resulting in a gap at the interface. If the swelling is large, the primary layer 92a may crack due to stress concentration. Further, the elasticity of the primary layer 92a is lowered (the modulus of elasticity is increased) due to the migration of the plasticizer, so that the microbend loss is increased, and the lateral pressure transmission characteristics of the optical fiber 90 may be reduced.

  An object of the present invention is to suppress the migration of a plasticizer from a resin material containing a plasticizer disposed in the vicinity to a coating layer formed on the outer periphery of the optical fiber, and even if exposed to a high temperature, the optical fiber It is an object of the present invention to provide an optical fiber in which peeling between the coating layer and the coating layer is suppressed and good lateral pressure transmission characteristics are maintained.

  In order to solve the above-mentioned problems, the optical fiber according to the present invention is provided with a coating layer made of a crosslinked resin having an equilibrium elastic modulus of 10 MPa or more at 150 ° C. in contact with the outer periphery of the optical fiber. And

  Here, the crosslinked resin constituting the coating layer preferably has an equilibrium elastic modulus of 50 MPa or less at 150 ° C.

  Moreover, it is preferable that the layer which consists of crosslinked resin which coat | covers the outer periphery of the said optical fiber consists only of the said coating layer.

  In the optical fiber according to the present invention, the coating layer covering the outer periphery of the optical fiber is made of a crosslinked resin having an equilibrium elastic modulus of 10 MPa or more at 150 ° C. As the equilibrium elastic modulus of the cross-linked resin increases, the distance between cross-linking points decreases, so that it becomes difficult for plasticizer molecules to pass through the cross-linked structure, and the cross-linked resin has an equilibrium elastic modulus of 10 MPa or more at 150 ° C. Even when heated in a state in which a resin material containing a plasticizer is disposed in the vicinity, it is possible to effectively suppress the migration of the plasticizer to the coating layer. As a result, peeling of the coating layer from the optical fiber can be suppressed and high lateral pressure transmission characteristics can be maintained.

  Here, when the cross-linked resin constituting the coating layer has an equilibrium elastic modulus of 50 MPa or less at 150 ° C., the coating layer has an appropriate flexibility and exhibits a buffering effect. Is more likely to be acquired.

  Further, when the layer made of the crosslinked resin covering the outer periphery of the optical fiber is composed of only one coating layer as described above, the coating layer does not have a two-layer structure such as a primary layer and a secondary layer. It will be. However, since only one coating layer is made of a material having an equilibrium elastic modulus of 10 MPa or more at 150 ° C., it can also serve as a primary layer and a secondary layer, and high lateral pressure transmission can be achieved with only one coating layer. It becomes an optical fiber that gives characteristics.

(A) is sectional drawing which shows the optical fiber strand concerning one Embodiment of this invention, (b) is an optical fiber core wire using this optical fiber strand, (c) is this optical fiber strand. It is sectional drawing which shows the used optical fiber cord. It is a graph which shows the estimate of the relationship between the equilibrium elastic modulus of crosslinked resin, and the distance between bridge | crosslinking points. It is a figure which shows the estimate of the size of a plasticizer, (a) is DINP, (b) has shown TOTM. It is sectional drawing which shows the conventional general optical fiber strand.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Fig.1 (a) has shown the cross section of the optical fiber strand 10 concerning one Embodiment of this invention. The optical fiber 10 has a structure in which a coating layer 12 is provided in contact with the outer periphery of the optical fiber 11.

  The optical fiber (glass fiber) 11 includes a core and a clad that has a lower refractive index than the core and covers the outer periphery of the core. Quartz glass, plastic, or the like is used for the core or clad of the optical fiber 11. The optical fiber 11 constituting the optical fiber 10 may be of any kind, but a multimode type is often used for in-vehicle use.

  The coating layer 12 is composed of a crosslinked resin, that is, a resin composition having a crosslinked structure. In particular, from the viewpoint that it is easy to form a structure in which the outer periphery of the optical fiber 11 is adhered and covered, the coating layer 12 is made of a curable resin, in particular, a resin composition having photocurability (particularly ultraviolet curable). It is preferable. The specific resin type of the cross-linked resin is not particularly limited as long as it provides an equilibrium elastic modulus as defined below. In the case of an ultraviolet curable resin, urethane acrylate, epoxy acrylate, silicone acrylate, etc., acrylate type The ultraviolet curable resin can be illustrated. Moreover, the crosslinked resin may contain an additive as appropriate.

  The crosslinked resin constituting the coating layer 12 has an equilibrium elastic modulus of 10 MPa or more at 150 ° C. Preferably, this equilibrium elastic modulus is 35 MPa or more. On the other hand, this equilibrium elastic modulus is preferably 50 MPa or less.

  When the optical fiber 10 is mounted and used in a vehicle or the like, the outer side is often formed in a form in which the outer side is covered with a protective layer or tube made of polyvinyl chloride (PVC). For example, the optical fiber strand 10 is used as the optical fiber core wire 20 shown in FIG. Here, a so-called tight coat structure is formed in which the protective layer 21 made of PVC is formed in close contact with the outer periphery of the optical fiber 10. Alternatively, the optical fiber strand 10 is used as an optical fiber cord 30 shown in FIG. Here, a so-called loose tube structure in which the optical fiber 10 is housed together with the strength member 32 is formed in a protective tube 31 made of PVC. The tensile body 32 is generally made of resin fibers such as Kevlar fibers. There may be a plurality of optical fiber strands 10 accommodated in the protective tube 31.

  The PVC constituting the protective layer 21 of the optical fiber core 20 and the protective tube 31 of the optical fiber cord 30 is usually made of soft PVC by blending a plasticizer. Examples of the plasticizer include dioctyl phthalate (DOP), diisononyl phthalate diisononyl (DINP), phthalate plasticizers such as diisodecyl phthalate (DIDP), diisodecyl adipate (DIDA), and trioctyl trimellitic acid. Non-phthalic acid plasticizers such as (TOTM). Among them, DINP and TOTM are plasticizers that are generally added to PVC that forms a protective layer or a protective tube that covers an optical fiber.

  Since the cross-linked resin constituting the covering layer 12 has an equilibrium elastic modulus of 10 MPa or more at 150 ° C., the optical fiber 10 having the protective layer 21 and the protective tube 31 formed outside is mounted on the vehicle. Even if the optical fiber 10 is heated by the heat generated by the peripheral members accompanying the driving of the vehicle, the plasticizer is difficult to move from the protective layer 21 or the protective tube 31 to the covering layer 12.

  If the crosslinked resin constituting the coating layer 12 exhibits an equilibrium elastic modulus of less than 10 MPa at 150 ° C., the plasticizer migrates from the protective layer 21 or the protective tube 31 to the coating layer 12 during heating. It happens easily. Then, the cross-linked resin constituting the coating layer 12 absorbs the plasticizer and swells, and due to this swelling and thermal aging, the adhesiveness of the coating layer 12 to the optical fiber 11 decreases, and the coating layer 12 and the light There is a possibility of creating a gap between the fibers 11. In particular, when the swelling is large, cracks may occur in the coating layer 12 due to stress concentration. In addition, the transition of the plasticizer reduces the elasticity of the coating layer 12 and causes non-uniform swelling along the axial direction, thereby increasing the microbend loss of the optical fiber 10 and increasing the lateral pressure transmission characteristics. There is a possibility that the (signal transmission characteristics in a state of receiving a side pressure) may be deteriorated. In particular, the primary layer 92a in the conventional general optical fiber 90 has a low equilibrium elastic modulus, and is liable to be peeled off due to the migration of the plasticizer and the lateral pressure transmission characteristics are deteriorated. Even if the outer periphery of the primary layer 92a is covered with the secondary layer 92b, the transition of the plasticizer to the primary layer 92a proceeds through a long time through the secondary layer 92b. Note that PVC containing a plasticizer is also widely used as an insulation coating for in-vehicle electric wires, and is used for electric wires when the optical fiber core wire 20 and the optical fiber cord 30 are arranged in parallel with the electric wires. There is a possibility that the plasticizer is transferred from the PVC to the coating layer 12 of the optical fiber 10. Thus, if the coating layer 12 in contact with the optical fiber 11 has a low equilibrium elastic modulus, the plasticizer may migrate from the resin material containing the plasticizer disposed in the vicinity to the coating layer 12. There is.

  On the other hand, in the optical fiber strand 10 according to the present embodiment, the coating layer 12 has an equilibrium elastic modulus of 10 MPa or more at 150 ° C., and is made of a resin material containing a plasticizer disposed in the vicinity. By suppressing the migration of the plasticizer, the coating layer 12 can easily maintain the initial characteristics even after the use of the optical fiber core wire 20 or the optical fiber cord 30 in a heating environment or the like. Thereby, even if it heats, while peeling at the interface of the coating layer 12 and the optical fiber 11 is suppressed, a high lateral pressure transmission characteristic is maintained. Such an effect becomes even higher when the equilibrium elastic modulus of the coating layer 12 at 150 ° C. is 35 MPa or more.

  Thus, since the cross-linked resin constituting the coating layer 12 has a high equilibrium elastic modulus, it is possible to avoid a specific decrease in lateral pressure transmission due to the migration of the plasticizer, but the equilibrium elastic modulus is too high. However, there is a possibility that the lateral pressure transmission characteristics may be reduced due to a decrease in the buffering property of the coating layer 12. When the equilibrium elastic modulus at 150 ° C. of the crosslinked resin constituting the coating layer 12 is 50 MPa or less, the coating layer 12 is in a relatively soft state and has high buffering properties, so that high lateral pressure transmission characteristics are further achieved. Cheap.

  The equilibrium elastic modulus of the crosslinked resin may be measured by a known method. For example, the storage elastic modulus is measured by dynamic viscoelasticity measurement while changing the temperature. And the value of the storage elastic modulus in the flat region where the logarithmic value of the storage elastic modulus exists only in the region higher than the glass transition temperature where the storage elastic modulus decreases rapidly with respect to the temperature rise, It can be an equilibrium elastic modulus.

  The coating layer 12 corresponds to having an equilibrium elastic modulus of 10 MPa or more at 150 ° C., and has a hardness corresponding to the middle between the primary layer 92a and the secondary layer 92b in the conventional optical fiber strand 90 having a two-layer structure. In many cases, only one layer can function as a semi-hard layer that serves as both the primary layer 92a and the secondary layer 92b. Thereby, both the microbend loss and the macrobend loss can be effectively suppressed only by the single coating layer 12 without providing a layer made of another crosslinkable resin in contact with the outer periphery of the coating layer 12. Can do. From this viewpoint, the covering layer 12 preferably has a Young's modulus in the range of 200 to 600 MPa at room temperature.

  Or you may provide the layer which contacts the outer periphery of the above coating layers 12, and consists of bridge | crosslinking resin harder than the coating layer 12 corresponding to the secondary layer 92b further. In this case, macrobend loss can be more effectively suppressed and strong physical protection can be given to the optical fiber 10.

  From the viewpoint of enhancing the effect of maintaining the lateral pressure transmission characteristics, the outer diameter of the optical fiber 10 on which the coating layer 12 is formed is approximately 245 to 255 μm when the outer diameter of the optical fiber 11 is 125 μm. preferable.

  The optical fiber 10 having the coating layer 12 as described above can be manufactured by, for example, arranging the coating layer 12 on the outer periphery of the drawn optical fiber 11 while forming the optical fiber 11 by drawing. it can. When the cross-linked resin constituting the coating layer 12 has ultraviolet curable properties, the outer periphery of the optical fiber 11 immediately after drawing is coated with an uncured ultraviolet curable resin, and then irradiated with ultraviolet rays immediately after. By making it harden | cure, the elongate optical fiber strand 10 can be manufactured continuously.

[Relationship between equilibrium elastic modulus of coating layer and plasticizer migration]
Since the crosslinked resin constituting the coating layer 12 has an equilibrium elastic modulus of 10 MPa or more at 150 ° C., the migration of the plasticizer from the resin material containing the plasticizer disposed in the vicinity to the coating layer 12 is suppressed. As a result, it is proved experimentally that the coating layer 12 hardly peels off even when heated and the high lateral pressure transmission characteristic is maintained, as will be shown later in the examples. It can also be derived by calculation using a model.

The equilibrium elastic modulus of the cross-linked resin has a strong correlation with the cross-linking point density, and the cross-linking point density increases as the equilibrium elastic modulus increases. It is known that the relationship of the following formula (1) is established between the equilibrium elastic modulus E ′ (MPa) and the crosslinking point density n (mol / m ³ ).
n = E ′ / (3RT) (1)
Here, R is a gas constant of 8.31 (J / (K · mol)). T is the temperature (K) at the time of measuring the equilibrium elastic modulus, and may be 150 ° C. (= 423 K).

When the cross-linked structure of the cross-linked resin is approximated to an aggregate of cubic lattice networks, the average distance d (nm) between cross-linking points has the following relationship with the cross-linking point density n (mol / m ³ ). .
n = (d · 10 ⁹ ) ³ · N _A (2)
N _A is Avogadro's number.

  Therefore, the relationship between the (average) inter-crosslinking point distance d and the equilibrium elastic modulus E ′ can be estimated by using the equations (1) and (2). FIG. 2 shows the relationship between the distance d between cross-linking points and the equilibrium elastic modulus E ′, which was estimated as T = 150 ° C. From this, it is confirmed that the distance between the cross-linking points exhibits a monotonically decreasing behavior with respect to the equilibrium elastic modulus E ′.

  In order to prevent the plasticizer from being transferred to the coating layer 12, the distance between the crosslinking points estimated above may be made smaller than the size of the plasticizer. Then, the plasticizer molecules cannot pass through the network-like crosslinked structure of the crosslinked resin, and cannot diffuse from the surface of the coating layer 12 to the inside.

  FIG. 3 shows size estimates for (a) DINP and (b) TOTM as representative plasticizers that can be added to the PVC listed above. Here, the length of each site shown in the figure was estimated by performing geometric calculation by approximating the length per bond to 0.139 nm which is the CC bond length in the benzene ring. .

  According to FIG. 3, the length of each displayed part is about 1-2 nm in any plasticizer. If the distance between the crosslinking points of the crosslinked resin constituting the coating layer 12 is shorter than this length, it can be considered that the plasticizer cannot pass through the crosslinked structure of the coating layer 12. According to FIG. 2, when the equilibrium elastic modulus is 10 MPa, the distance between the crosslinking points is about 1 nm, which corresponds to the estimated plasticizer size. That is, if the equilibrium elastic modulus of the crosslinked resin constituting the coating layer 12 is 10 MPa or more, the plasticizer having the above size cannot pass through the crosslinked structure and moves to the inside of the coating layer 12. Will be suppressed.

  This is an experiment in which, as will be shown later in Examples, if the equilibrium elastic modulus of the crosslinked resin is 10 MPa or more, peeling of the coating layer 12 due to migration of the plasticizer and reduction in the lateral pressure transmission characteristics are effectively suppressed. The result is in good agreement. In other words, in the above model, the crosslinked structure of the crosslinked resin and the molecular size of the plasticizer are estimated using a simplified approximate model, and the chemical interaction between the crosslinked resin and the plasticizer is taken into account. In spite of this, it is possible to estimate the equilibrium elastic modulus necessary for suppressing the migration of the plasticizer.

  Examples of the present invention and comparative examples are shown below. In addition, this invention is not limited by these Examples.

[Preparation of test sample]
(Examples 1-5, Comparative Examples 1-3)
A graded index (GI) fiber having an outer diameter of the core of 50 μm and an outer diameter of the cladding of 125 μm is used as an optical fiber, and the outer periphery is made of urethane acrylate having various equilibrium elastic moduli shown in Table 1 below at 150 ° C. An optical fiber having a coating layer composed of one layer was produced by coating the ultraviolet curable resin composition and curing the composition by ultraviolet irradiation. The diameter of the optical fiber was 190 μm. And the outer periphery of the obtained optical fiber strand was tightly coated with PVC by a PVC extruder to form a protective layer, thereby obtaining an optical fiber core having an outer diameter of 0.9 mm. The PVC used contains 30% by mass of DINP as a plasticizer. As described above, optical fiber cores according to Examples 1 to 5 and Comparative Examples 1 to 3 were obtained.

(Comparative Example 4)
A protective layer made of PVC is formed on the outer periphery of a conventional two-layer coated optical fiber (outer diameter 250 μm) having a conventional primary layer and secondary layer, and an optical fiber core according to Comparative Example 4 is formed. did.

[Evaluation method]
(Measurement of equilibrium elastic modulus)
Each ultraviolet curable resin composition was cured by ultraviolet irradiation to form a sheet having a thickness of 200 μm and a width of 3 mm, and dynamic viscoelasticity measurement was performed. In the measurement, the distance between chucks was 30 mm, the strain was ± 10 μm, the frequency was 1 Hz, and the heating rate was 2 ° C./min. It was. In the graph of the temperature dependence of the logarithmic value of the obtained storage elastic modulus, after confirming that 150 ° C. is in a flat region, the value of the storage elastic modulus at 150 ° C. was defined as the equilibrium elastic modulus.

(Evaluation of covering condition)
The optical fiber core wires according to each of the examples and the comparative examples were wound around a mandrel made of stainless steel having an outer diameter of φ20 mm for 50 turns with a tension of 10 g. In this state, it was aged by leaving it in a constant temperature bath at 120 ° C. for 300 hours. Thereafter, the PVC protective layer was removed, and the coating state of the coating layer on the optical fiber was visually observed. The case where peeling of the coating layer from the optical fiber was observed over almost the entire area along the axial direction of the optical fiber was defined as “x” in which the coating state was poor. Although peeling of the coating layer from the optical fiber was observed in some areas along the axial direction, in most areas no peeling or cracking was observed in the coating layer, the covering state was good. " Then, over the entire axial direction, the case where neither peeling nor cracking was observed in the coating layer was defined as “◎” indicating that the coating state was excellent.

(Evaluation of side pressure transmission characteristics)
The optical fiber core wire having a total length of 10 m according to each of the examples and comparative examples was bundled in a diameter of 300 mm and left in a constant temperature bath at 120 ° C. for 300 hours for aging. Thereafter, the lateral pressure transmission characteristics were evaluated. That is, a pair of metal plates 100 mm in length along the axial direction sandwich a midway part of the optical fiber core, and a side pressure is applied by applying a 50 kg load from one metal flat plate to the optical fiber core. It was. Side pressure transmission characteristics were evaluated as an increase in transmission loss due to application of side pressure. The measurement was performed at a wavelength of 0.85 μm. When the increase in transmission loss is 0.5 dB / 100 mm or more, the lateral pressure transmission characteristics are poor “×”, and when the transmission loss is 0.1 dB / 100 mm or more to less than 0.5 dB / 100 mm, the lateral pressure transmission characteristics are good “O”. In the case of less than 0.1 dB / 100 mm, the side pressure transmission characteristics are excellent as “◎”.

<Results and discussion>
Table 1 summarizes the equilibrium elastic modulus at 150 ° C. and the evaluation results for the samples according to each example and comparative example.

  According to Table 1, in Comparative Examples 1 to 3 in which the equilibrium elastic modulus of the coating layer at 150 ° C. is less than 10 MPa, peeling occurs at the interface between the coating layer and the optical fiber after heating. In the two-layer coated optical fiber according to Comparative Example 4 in which the equilibrium elastic modulus of the primary layer is particularly low at 0.2 MPa, cracking of the coating layer occurs in addition to peeling of the interface between the coating layer and the optical fiber. ing. On the other hand, in Examples 1 to 5 in which the equilibrium elastic modulus of the coating layer at 150 ° C. is 10 MPa or more, the occurrence of peeling at the interface between the coating layer and the optical fiber is suppressed. In particular, in Examples 2 to 5 in which the equilibrium elastic modulus is 35 MPa or more, no peeling is observed over the entire axial direction. As a result, the equilibrium elastic modulus at 150 ° C. of the coating layer is 10 MPa or more, so that the migration of the plasticizer from the PVC protective layer arranged outside the coating layer to the coating layer is suppressed, and as a result, heating is reduced. Even if it receives, it is interpreted that the adhesiveness of the coating layer to the optical fiber is kept high, and the swelling of the coating layer is suppressed.

  Focusing on the lateral pressure transmission characteristics, in the region where the equilibrium elastic modulus of the coating layer at 150 ° C. is 35 MPa or less, the decrease in transmission loss due to the lateral pressure is generally smaller as the equilibrium elastic modulus is larger. This result shows that as the equilibrium elastic modulus increases, the migration of the plasticizer from the PVC protective layer to the coating layer is suppressed, and deterioration of the lateral pressure characteristics due to swelling and a decrease in elasticity is suppressed. It also matches the prediction based on the model that showed the results.

  On the other hand, in the region where the equilibrium elastic modulus of the coating layer at 150 ° C. exceeds 35 MPa, the transmission loss due to the side pressure starts to increase again. This is interpreted as a decrease in the flexibility of the coating layer and a decrease in the buffering property against the applied lateral pressure. In the region where the coating layer has an equilibrium elastic modulus of 10 MPa to 50 MPa at 150 ° C., the increase in transmission loss due to side pressure is suppressed to 0.1 dB / 100 mm or less, and particularly excellent side pressure transmission characteristics are obtained. .

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. In the above, the molecular size of the plasticizer was estimated using DINP and TOTM, which are typical plasticizers used for addition to PVC, but the molecular size is significantly larger or smaller than these. In the case of using a plasticizer, after appropriately estimating the size of the plasticizer, based on the relationship between the equilibrium elastic modulus and the distance between the crosslinking points shown in FIG. 2, the distance between the crosslinking points corresponding to the size of the plasticizer is calculated. What is necessary is just to select the equilibrium elastic modulus of crosslinked resin so that it may become more than the value of the equilibrium elastic modulus to give.

DESCRIPTION OF SYMBOLS 10 Optical fiber 11 Optical fiber 12 Coating layer 20 Optical fiber core wire 21 (PVC) protective layer 30 Optical fiber cord 31 (PVC) protective tube 32 Tensile body

Claims (3)

  An optical fiber, wherein a coating layer made of a crosslinked resin having an equilibrium elastic modulus of 10 MPa or more at 150 ° C. is provided in contact with the outer periphery of the optical fiber.   2. The optical fiber according to claim 1, wherein the cross-linked resin constituting the coating layer has an equilibrium elastic modulus of 50 MPa or less at 150 ° C. 3.   3. The optical fiber according to claim 1, wherein the layer made of a crosslinked resin covering an outer periphery of the optical fiber is composed of only one coating layer.

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