JP2014092757A - Optical fiber and optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber having little fluctuations of a transmission loss by temperature change even when an effective core cross-sectional area is large, and to provide an optical fiber cable including the optical fiber.SOLUTION: An optical fiber 20 includes a glass fiber 21 composed of a core and a cladding, a primary resin layer 22 covering the glass fiber 21, and a secondary resin layer 23 covering the primary resin layer 22. The primary resin layer 22 has a glass transition temperature of -40°C or lower. A transmission loss of the optical fiber 20 is denoted by α1 at a wavelength W1 in a range from 1520 nm to 1580 nm in a wound state on a bobbin having a diameter of 150 mm or more and 300 mm or less under the condition of room temperature; a transmission loss of the optical fiber is denoted by α2 at the wavelength W1 under the condition of no lateral pressure to the optical fiber 20; the difference (α1-α2) between α1 and α2 at +25°C is 0.003 dB/km or more; and in an environment of -40 to +25°C, α2 is equal to α1-0.005 dB/km or more up to α1.

Description

  The present invention relates to an optical fiber used for optical communication and an optical fiber cable including the same.

  In recent years, since the capacity of data transmitted by a single optical fiber has increased, the need to input signal light having a stronger optical power to the optical fiber has increased. However, when a strong optical power is input to the optical fiber, the signal light waveform is distorted due to a nonlinear effect corresponding to the optical power density in the optical fiber, so that the quality of the transmission signal is deteriorated. For this reason, the usefulness of an optical fiber in which the optical power density is reduced, that is, the effective core area (hereinafter referred to as Aeff) is increased. However, if Aeff is easily enlarged, it becomes weak against external stress, and transmission loss increases only by winding on a bobbin. Further, since transmission loss after cable processing tends to increase in a low temperature environment, special attention must be paid to temperature characteristics.

  Patent Document 1 discloses a shrinkage stress defined on the basis of Young's modulus, cross-sectional area, effective linear expansion coefficient, etc. of a resin layer at −40 ° C. in an optical fiber in which a glass fiber is coated with a plurality of ultraviolet curable resin layers. It is described that it has been found that deterioration of transmission characteristics of an optical fiber under a low temperature environment can be sufficiently prevented when the index is a certain value or less.

Japanese Patent No. 4134724

In the case of an optical fiber having an Aeff larger than 125 μm ² , for example, when the optical fiber is wound around a resin bobbin for an optical fiber having a diameter of about 150 mm to 300 mm, the stress applied from the side by being wound in multiple layers A phenomenon is known in which optical transmission loss increases due to (hereinafter referred to as lateral pressure). However, in a general loose tube structure optical cable, the side pressure applied to the optical fiber is smaller in the state after cable formation than in the bobbin winding state. This is because the optical fiber in the loose tube is housed together with Jerry in a freely movable state. That is, it can be considered that the increase amount of the optical transmission loss of the optical fiber cable after the cable processing is smaller than the increase amount of the optical transmission loss of the optical fiber in the bobbin winding state.
On the other hand, there is a known problem that, even in a low temperature environment, the optical transmission loss increases as Aeff increases. This is because, in a low temperature environment, the coating resin of the optical fiber becomes hard, so that external stress is easily transmitted to the glass. As a countermeasure, it is effective to lower the Young's modulus of the coating layer, particularly the primary layer, in a low-temperature environment. However, if the Young's modulus of the primary layer is too low, the mechanical strength of the coating layer decreases. . As a result, the primary layer is destroyed by a large external stress that is temporarily applied during processing of the optical fiber and handling during use, etc., causing deterioration in the performance of the optical fiber, particularly an increase in optical transmission loss in a low temperature environment. End up.
However, the optical fiber described in Patent Document 1 does not solve these problems.

  An object of the present invention is to provide an optical fiber in which fluctuation of optical transmission loss is small due to a temperature change at a low temperature while being wound around a bobbin even when Aeff is large, and an optical fiber cable including the optical fiber.

The optical fiber of the present invention capable of solving the above problems is
An optical fiber comprising a glass fiber composed of a core part and a clad part, a primary resin layer covering the glass fiber, and a secondary resin layer covering the primary resin layer,
The glass transition point of the primary resin layer is −40 ° C. or lower,
Any wavelength in the range of 1520 to 1580 nm is W1, and the transmission loss of the optical fiber at the wavelength W1 when wound on a bobbin having a diameter of 150 mm or more and 300 mm or less at room temperature is α1, and there is no lateral pressure on the optical fiber When the transmission loss at the state wavelength W1 is α2, the difference between α1 and α2 at + 25 ° C. (α1−α2) is 0.003 dB / km or more,
The α2 in an environment of −40 to + 25 ° C. is α1−0.005 dB / km or more and α1 or less.

  In the optical fiber of the present invention, α2 is preferably smaller than 0.17 dB / km.

In the optical fiber of the present invention, the effective core area Aeff at a wavelength of 1550 nm is preferably larger than 125 μm ² .

In the optical fiber of the present invention, it is preferable that 0.3 μm ² dB / km ≦ Aeff * (α1−α2) ≦ 1.7 μm ² dB / km.

  In the optical fiber of the present invention, it is preferable that a Young's modulus at + 25 ° C. of the primary resin layer is 0.65 MPa or less, and a Young's modulus at −40 ° C. of the primary resin layer is 30 MPa or less.

  The optical fiber cable of the present invention that can solve the above-mentioned problems is an optical fiber cable including the above-described optical fiber.

  According to the optical fiber of the present invention, by designing the glass transition point of the primary resin layer to be low, it is possible to reduce transmission loss in a low-temperature environment after cable formation even for an optical fiber having a large Aeff.

It is sectional drawing which shows an example of the optical fiber cable which concerns on embodiment of this invention. It is sectional drawing which shows an example of the optical fiber which concerns on embodiment of this invention. It is a perspective view which shows the state by which the optical fiber shown in FIG. 2 was wound around the bobbin. It is a graph which shows the relationship between the loss increase from the transmission loss in +25 degreeC, and temperature of the optical fiber shown in FIG. It is a graph which shows the relationship between the Young's modulus and temperature of the primary resin layer of the optical fiber shown in FIG.

  Hereinafter, an example of an embodiment of an optical fiber and an optical fiber cable concerning the present invention is described with reference to drawings.

  As shown in FIG. 1, an optical fiber cable 10 is provided inside a plurality of thermoplastic resin tubes 11 that accommodate a plurality of optical fibers 20 and a circle in which the plurality of tubes 11 are arranged circumferentially. And a pressing roll 13 for pressing the outer circumferences of the plurality of tubes 11 and the tensile strength bodies 12 and a thermoplastic resin coating 14 provided on the outer circumference of the pressing roll 13.

  The tube 11 is made of polyethylene, nylon, polybutadiene terephthalate (PBT), or the like, and an optical fiber 20 is accommodated in the tube 11 together with a jelly-like mixture 15.

  As the mixture 15, a thermosetting or ultraviolet curable silicone gel, or a jelly-like resin in which a rubber such as butadiene or silicon is swollen in an oil such as silicone or naphthene, and a filler is added as necessary, is used. In order to prevent the extra length of the optical fiber 20 from being concentrated unevenly in the length direction and suppressing an increase in loss that occurs locally, the filled mixture 15 has at least a viscosity that does not flow naturally, and Although it deforms with respect to a gentle external force, it preferably has a property of exhibiting resilience with respect to an abrupt external force.

  As shown in FIG. 2, the optical fiber 20 accommodated in the optical fiber cable 10 is made of, for example, a glass fiber 21 having a diameter of 125 μm and an ultraviolet curable resin having a thickness of 22.5 to 27.5 μm, for example. A primary resin layer 22 and a secondary resin layer 23 made of an ultraviolet curable resin having a thickness of 32.5 to 37.5 μm, for example, are provided.

The primary resin layer 22 covering the glass fiber 21 has a Young's modulus lower than that of the outermost secondary resin layer 23 and is made of a soft resin. Specifically, the Young's modulus of the primary resin layer 22 is preferably 0.65 MPa or less at + 25 ° C., and preferably 30 MPa or less at −40 ° C.
Since the secondary resin layer 23 is a protective layer constituting the outermost layer of the optical fiber 20, the Young's modulus is preferably 400 MPa or more at + 25 ° C.

  In general, as Aeff increases, the optical fiber 20 becomes sensitive to the lateral pressure. Therefore, as shown in FIG. 3, transmission loss caused by microbending is a problem when the optical fiber 20 is wound around the bobbin B. However, after the optical fiber 20 is turned into a cable and, for example, the loose tube type optical fiber cable 10 is manufactured, the periphery of the optical fiber 20 is filled with the jelly-like mixture 15. The applied side pressure is reduced, and the effect on transmission loss is reduced. Therefore, if Aeff is large, the difference between the transmission loss when the optical fiber 20 is wound around the bobbin B and the transmission loss when there is no lateral pressure on the optical fiber 20 (difference in transmission loss between manufacturing processes) increases. Cheap.

Here, Aeff is changed, and any wavelength within 1520 to 1580 nm is set to W1, and the transmission loss α1 at the wavelength W1 of the optical fiber 20 in a state where the optical fiber 20 is wound around the bobbin B having a body diameter of, for example, 168 mm. Then, the transmission loss α2 at the wavelength W1 of the optical fiber cable 10 in which the optical fiber 20 is converted into a loose tube cable and there is no lateral pressure on the optical fiber 20 is measured at + 25 ° C. The difference (α1-α2) was evaluated. The results are shown in Table 1.
In Examples 1 to 3, an optical fiber having an Aeff of greater than 125 μm ² was used. As Comparative Example 1, an optical fiber having an Aeff of 118 μm ² was used. In addition, the length of the optical fiber used in Examples 1 to 3 and Comparative Example 1 is 16,000 m.

As shown in Table 1, in Comparative Example 1 where Aeff is 125 μm ² or less, there is no difference between the transmission loss α1 of the optical fiber 20 and the transmission loss α2 of the optical fiber cable 10 in the bobbin winding state.
On the other hand, in Examples 1 to 3 where Aeff is greater than 125 μm ^2, the transmission loss α2 of the optical fiber cable 10 after cable formation is smaller than the transmission loss α1 of the optical fiber 20 in the bobbin winding state, and α1 at + 25 ° C. And α2 (α1−α2) was 0.003 dB / km or more. As described above, this is because α1−α2 increases in the case of the optical fiber 20 having a large Aeff.

As described above, in the present embodiment, as the optical fiber 20 having a large Aeff, the difference between the transmission loss α1 of the optical fiber 20 and the transmission loss α2 of the optical fiber cable 10 in the bobbin winding state is 0.003 dB / km or more. Stipulate. In addition, when the value obtained by multiplying Aeff and α1−α2 is used as an index indicating that the optical fiber 20 has a large Aeff and a variation in transmission loss between processes, the optical fiber according to the present embodiment is used. 20 is 0.3 μm ² dB / km ≦ Aeff * (α1-α2) ≦ 1.7 μm ² dB / km.

  In the optical fiber 20 having a large Aeff as in the first to third embodiments, the inventor sets the cable even in a low temperature environment of −40 ° C. when the glass transition point of the primary resin layer 22 is set to −40 ° C. or lower. It has been found that the transmission loss α2 after conversion can be made smaller than before.

Here, in order to evaluate the temperature characteristic of the transmission loss depending on the resin layer, the primary resin layer 22 in which the glass transition point of the primary resin layer 22 is set to −40 ° C. or less as in Example 4 as in Examples 1-3. And optical fiber 20 including primary resin layer 22 having a glass transition point set to about −10 ° C. as in the past as Comparative Examples 2 and 3, and transmission at + 25 ° C. in each sample The loss increase from the loss was measured. The results are shown in Table 2. In all of Example 4 and Comparative Examples 2 and 3, the same glass fiber 21 is used except for the coating resin, and the Aeff of the optical fiber is about 126 μm ² .

  As shown in Table 2 and FIG. 4, in Comparative Examples 2 and 3, it can be seen that the transmission loss of the optical fiber increases in proportion to the decrease in the environmental temperature, and the transmission loss increases rapidly particularly at −40 ° C. . On the other hand, in Example 4, the transmission loss of the optical fiber 20 is almost flat even when the environmental temperature is lowered to −40 ° C.

  From the above, it was confirmed that even in the optical fiber 20 having a large Aeff, by using the primary resin layer 22 in which the glass transition point is set to −40 ° C. or less, there is little variation in transmission loss due to temperature change. Specifically, the α2 in an environment of −40 to + 25 ° C. is α1−0.005 dB / km or more and α1 or less, and it was confirmed that an increase in transmission loss is suppressed even in a low temperature environment.

Next, for the primary resin layers of Example 4 and Comparative Examples 2 and 3, the temperature dependence of Young's modulus was evaluated. The results are shown in Table 3 and FIG.

As shown in Table 3 and FIG. 5, in Comparative Examples 2 and 3, the Young's modulus of both the primary resin layer and the secondary resin layer increased rapidly in the environment of −40 ° C. compared to the environment of 25 ° C. and 60 ° C. Yes.
On the other hand, in Example 4, the Young's modulus of the primary resin layer 22 is 10 MPa at −40 ° C., and is designed to be a lower value than Comparative Examples 2 and 3.

  As described above, by using the primary resin layer 22 of the present embodiment having a low glass transition point, the Young's modulus of the primary resin layer 22 does not rapidly increase even in a low temperature environment of −40 ° C. It was confirmed that even in the environment, the primary resin layer 22 does not become harder than necessary and the transmission loss does not increase.

  According to the optical fiber 20 according to the present embodiment described above, even if the optical fiber 20 has a large Aeff by setting the glass transition point of the primary resin layer 22 to −40 ° C. or lower, which is lower than the conventional one. An increase in transmission loss in a low-temperature environment after manufacturing the cable 10 is suppressed, and fluctuations in transmission loss due to temperature changes can be reduced.

  Although an example of an embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and other configurations can be adopted as necessary.

  In the above embodiment, the transmission loss α1 in the state where the optical fiber 20 is wound around the bobbin B having a body diameter of 168 mm is described. However, the body diameter of the bobbin B when measuring α1 is a general-purpose bobbin. What is necessary is just 150 mm or more and a certain 300 mm or less.

  10: optical fiber cable, 20: optical fiber, 21: glass fiber, 22: primary resin layer, 23: secondary resin layer, B: bobbin

Claims (6)

An optical fiber comprising a glass fiber composed of a core part and a clad part, a primary resin layer covering the glass fiber, and a secondary resin layer covering the primary resin layer,
The glass transition point of the primary resin layer is −40 ° C. or lower,
Any wavelength in the range of 1520 to 1580 nm is W1, and the transmission loss of the optical fiber at the wavelength W1 when wound on a bobbin having a diameter of 150 mm or more and 300 mm or less at room temperature is α1, and there is no lateral pressure on the optical fiber When the transmission loss at the state wavelength W1 is α2, the difference between α1 and α2 at + 25 ° C. (α1−α2) is 0.003 dB / km or more,
The optical fiber characterized in that the α2 in an environment of −40 to + 25 ° C. is α1−0.005 dB / km or more and α1 or less.   The optical fiber according to claim 1, wherein α2 is smaller than 0.17 dB / km. 3. The optical fiber according to claim 1, wherein an effective core area Aeff at a wavelength of 1550 nm is larger than 125 μm ² . The optical fiber according to claim 1, wherein 0.3 μm ² dB / km ≦ Aeff * (α1−α2) ≦ 1.7 μm ² dB / km.   5. The Young resin modulus at + 25 ° C. of the primary resin layer is 0.65 MPa or less, and the Young modulus at −40 ° C. of the primary resin layer is 30 MPa or less. The optical fiber described.   An optical fiber cable provided with the optical fiber as described in any one of Claim 1 to 5.

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