JP5407111B2 - Optical cable - Google Patents

Description

  The present invention relates to an optical cable used for optical connection between information devices (for example, LAN wiring and device wiring).

  With recent advances in optical communication technology, LAN (Local Area Network) wiring using optical communication, wiring between devices, and the like have been adopted. Optical cables used for indoor and in-vehicle optical LAN wiring and inter-device wiring include wiring in intricate or uneven parts, so it is flexible and thin. It is desirable to be. This optical cable is used in a relatively short length (1 m to 20 m) as compared with a normal cable. Therefore, the transmission loss is not required to be as low as that of a normal cable.

  If the outer dimensions of the optical cable are small, the surface area per unit volume will be large and it will be easy to touch the air, and it is necessary to use a halogen-free flame retardant with low flame resistance due to environmental problems. In many cases, a flame retardant of 30% or more by weight ratio is added.

  In addition, this optical LAN wiring or inter-device wiring is different from long-distance optical communication, for example, because it is short-distance optical communication between devices installed indoors or in vehicles. A multi-mode optical fiber having a large core diameter and superior optical connectivity is often used. However, multimode optical fibers are subject to disturbance factors such as temperature expansion and contraction, and transmission loss is likely to increase compared to general-purpose single mode optical fibers. For this reason, a soft ultraviolet curable acrylate resin having a Young's modulus of about 1 MPa is used for the coating layer immediately above the glass of the optical fiber core wire so as to mitigate disturbance factors.

On the other hand, as an optical cable having a relatively small number of cores and a small cable outer dimension, there is an optical cable having a shape known as a drop cable or an indoor cable (see, for example, Patent Document 1). In this type of optical cable, tension members are usually arranged on both sides of one to several optical fiber cores, and the whole is integrated with a cable jacket made of a thermoplastic resin. Moreover, in the said patent document 1, it arrange | positions the fibrous interposition around the optical fiber core wire so that it may have an impact resistance characteristic and a lateral pressure resistance characteristic.
JP 2004-144821 A

  As an optical cable for LAN and inter-device wiring, it is assumed that a small work tool such as a nipper is dropped at a place where there is a convex portion under the cable. Must withstand impact. However, if the outer dimension of the optical cable is small, the thickness of the cable jacket that protects the cable also becomes thin, so that the impact resistance is weak. In addition, non-halogen flame retardants added to increase flame retardancy become less elastic as the amount added increases, and after an impact is applied, crush marks on the cable jacket remain like clay, and light The fiber core wire is also easily damaged.

  Further, when a resin having a low Young's modulus is used for the coating layer of the optical fiber core wire, the transmission characteristics of the optical fiber are improved, but the acrylate resin layer having a low Young's modulus is easily crushed when subjected to an impact from the outside. Along with this, a large distortion also occurs in the colored layer in the outermost layer of the coating layer of the optical fiber core wire. Since the colored layer is difficult to transmit ultraviolet rays due to the addition of a colorant, a large amount of a crosslinking component having a low breaking elongation is added to accelerate curing. As a result, the elongation at break is as low as about 2%, so that damage occurs beyond the limit of the elongation at break.

  For this reason, in the above-described optical cable having a small number of cores and a small size, when an impact is applied, the cable jacket tends to be crushed, and the coating of the optical fiber core wire is likely to be damaged. When the cable jacket is crushed, the location tends to be the starting point of bending, and there is a risk of bending at an allowable bending diameter or less. Further, regarding the damage of the optical fiber core, there is a fear that the fiber glass may be broken under an environment where a temperature change or vibration is applied for a long period of time, and there is anxiety from the viewpoint of long-term reliability.

  On the other hand, as disclosed in Patent Document 1, it is possible to improve the impact resistance by covering the periphery of the optical fiber with a fibrous inclusion. However, optical cables such as LAN and inter-device wiring are usually used with an optical connector attached thereto, and if there is a fibrous interposer, there is a problem that the connector attachment property that is a field work is lowered. Although the impact resistance can be improved by increasing the thickness of the cable jacket, it increases the outer dimensions of the optical cable, increases the wiring space, and increases the cable bending rigidity. There is a problem that the handleability deteriorates.

  The present invention has been made in view of the above-described circumstances. By selecting an appropriate material for the cable jacket and selecting and combining an appropriate material for the coating layer of the optical fiber core wire, the impact characteristics are improved. The purpose is to provide an optical cable.

Optical cable according to the invention, a colored layer having a Young's modulus directly above the optical fibers of quartz glass composed primarily coats the above ultraviolet curing resin 200 MPa, elongation at break immediately above the consists of 2% or more of the ultraviolet curable resin On the optical fiber core coated with, a thermoplastic resin having flame retardancy of V2 or higher according to UL standards and Young's modulus of 200 MPa or more is coated to form a jacket.
In addition, it is preferable that said jacket does not contain halogen and the cross-sectional external shape of a jacket is a rectangle or an ellipse.

  According to the present invention, by ensuring the elasticity of the cable jacket, it is possible to suppress the crush of the cable jacket to a predetermined value or less, and to reduce the possibility that the impacted portion is easily bent. In addition, by selecting the resin material for the coating layer of the optical fiber core wire as described above, damage to the colored layer having a small elongation at break can be reduced, the glass fiber can be prevented from breaking, and long-term reliability can be improved. be able to.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining the outline of an optical cable according to the present invention. FIG. 1 (A) shows an example of an optical cable having a rectangular cross section, and FIG. 1 (B) shows a test method for specifying the cable jacket of the optical cable. It is. In the figure, 10 is an optical cable, 11 is an optical fiber core wire, 12 is a glass fiber, 13a and 13b are core wire coating layers, 14 is a colored layer, 16 is a cable jacket, 17 is a tension member, 18 is a metal piece, 19 Indicates a weight.

  An optical cable 10 according to the present invention is an optical cable that optically connects a plurality of information devices installed indoors or in a vehicle, and is used for LAN construction with optical wiring of a relatively short distance (for example, about 1 m to 20 m). The main object is an optical cable (LAN optical cable) suitable for use. For example, as shown in FIG. 1 (A), this type of optical cable 10 has two or more optical fiber cores 11 arranged in a line, and tension members 17 are not arranged on both sides of the cable. The outer cover 16 is integrally formed.

  For the optical fiber core 11, a multimode glass fiber 12 made of quartz glass, having a core diameter of 50 μm and a cladding diameter of 125 μm can be used. In addition, the optical fiber mainly made of quartz glass may be one in which both the core and the clad are made of quartz glass, or only the core is made of quartz glass and the clad is made of hard plastic. There may be.

  The optical fiber core 11 is formed by covering the glass fiber 12 with coating layers 13a and 13b made of an ultraviolet curable acrylate resin and having an outer diameter of about 245 μm, and applying a colored layer 14 to the coating surface. In addition, you may make it form a coating layer by two layers, the primary coating layer 13a and the secondary coating layer 13b. In this case, the Young's modulus of the inner primary coating 13a is made smaller than the Young's modulus of the outer secondary coating 13b so as to provide a buffering action against the side pressure so as to suppress the generation of microbends and maintain good optical transmission characteristics. can do.

  Two or more optical fiber core wires 11 are arranged side by side in a row, and are integrated with a cable jacket 16 with or without tension members 17 disposed on both ends thereof. Note that the tension member 17 may not be particularly required in a usage mode in which a large tension is not always applied, such as LAN wiring, as long as the tensile tension of the entire optical cable can be secured to a predetermined value or more. However, the tension member 17 may be provided to reduce the tension applied to the optical fiber core wire 11 during laying work or the like. The tension member 17 can be a high-strength polymer fiber bundle such as a metal wire or an aramid fiber. The high-strength polymer fiber bundle may be used in the form of a rod-shaped wire solidified with a matrix resin.

  The cable jacket 16 is formed of a thermoplastic resin such as nylon resin or polyethylene so that the cross section with the long side in the direction in which the optical fiber cores are arranged side by side is rectangular or elliptical, and the short side (optical fiber The covering thickness in the direction perpendicular to the side-by-side of the core wires is 0.7 mm or more. Note that the maximum dimension on the long side in the cross section of the cable jacket 16 is desirably 4 mm or less. Moreover, as a kind of thermoplastic resin, the thing which does not contain the halogen which has the flame retardance of V2 by UL specification is used. In addition, the cable jacket 16 may be made of various resins such as styrene, olefin, polyester, and urethane. The cable jacket 16 is formed by full extrusion.

  Solid extrusion is a method of performing extrusion while applying pressure to an optical fiber core or the like so as to compress the extruded resin inside the die of the resin extruder. The extruded resin is in a compressed state in the die, and the thermoplastic resin extruded on the outer periphery of the optical fiber core wire 11 can have high adhesion to the optical fiber core wire 11 as the cable jacket 16. it can. Since the cable jacket 16 is in close contact with the optical fiber core 11, it is possible to prevent the optical fiber core 11 from meandering in the cable when the cable jacket 16 contracts.

  In the present invention, in order to give impact resistance to the optical fiber, the cable jacket 16 uses a thermoplastic resin having elasticity with a Young's modulus of 200 MPa or more. Furthermore, it is desirable that the cable jacket 16 be formed of a resin material whose crushing rate by a predetermined test method is 25% or less.

  FIG. 1B is a diagram showing the above test method, and the multi-mode glass fiber 12 composed of the core portion and the clad portion described in FIG. 1A is covered with the covering layers 13a and 13b and the colored layer 14. An optical cable 10 is formed by molding a cable jacket 16 of a thermoplastic resin with a rectangular cross section of 2 mm × 3 mm along the longitudinal direction so as to cover the optical fiber core wire 11. The long side (surface with a width of 3 mm) of the optical cable 10 is placed horizontally, and a 2 mm square metal rod 20 is placed on the lower surface thereof. A thermoplastic resin in which a weight 21 having a diameter of 30 mm and a mass of 1 kg is dropped from a height position of 50 mm above the optical cable 10, and the crushing rate of the cable jacket 16 caused by the dropping is 25% or less. A cable jacket 16 is formed.

  With the above-described configuration, when an impact caused by external force is applied to the installed optical cable, the deformation due to the crushing of the cable jacket is minimized, and the impacted portion is less likely to be bent. Can do. Further, damage to the coating layer and the colored layer of the optical fiber core wire can be reduced.

( Example)
FIG. 2 shows a cross section of an optical fiber core wire used in the optical cable shown in FIG. 1 of the present invention . This embodiment, the optical fiber 11a as shown in FIG. 2, arranged in rows of two as shown in FIG. 1, both sides by arranging the tension member 17, 2 mm × rectangular cross section of the cable outside of 3mm The optical cable has a shape integrated with the cover 16. The cable jacket 16 has a coating thickness in the direction perpendicular to the horizontal direction of the optical fiber core wires 11 of 0.9 mm, Young's modulus of 1200 MPa, elongation at break of 100%, UL standard V2 flame retardant polyamide containing no halogen The tension member 17 was made of a high-strength polymer fiber integrated with a polyester resin.

A multimode fiber having a core diameter of 50 μm and a cladding diameter of 125 μm was used for the glass fiber 12 of the optical fiber core wire 11a. In this example , from the viewpoint of optimizing the Young's modulus of the coating layer 13 ( example in which the secondary coating 13b in FIG. 1 is omitted) , the elongation at break at a Young's modulus of 800 MPa up to an outer diameter of 170 μm is formed on the glass fiber 12. The coating layer 13 was formed of 56% ultraviolet curable acrylate resin. On the coating layer 13, an ultraviolet curable acrylate resin having a Young's modulus of 1200 MPa and an elongation at break of 2% was applied as the colored layer 14 to an outer diameter of 180 μm. In addition, from the viewpoint of increasing the breaking elongation of the colored layer 14, a colorant may be added so that the breaking elongation is 10% or more. Further, when the density of the colorant is reduced in order to increase the elongation at break, it can be compensated by increasing the thickness.

As a result of testing the optical cable formed as described above by the method shown in FIG. 1B, the crushing rate of the cable jacket was 15%. Further, the coating layer 13 and the colored layer 14 of the optical fiber core wire were not damaged, and as a result of a temperature test of (−40 ° C. to 125 ° C.) × 3 cycles, an increase ΔΔα in transmission loss was 0.30 dB / It was 20 m.
In this example , a thermoplastic resin having a Young's modulus of 1200 MPa was used for the cable jacket, but by using a resin having a Young's modulus of 200 MPa or more, the crushing rate was 25% or less by the test method shown in FIG. And was able to. Moreover, in the flame-retardant test as a cable (ISO 6722 45 ° inclination test), the fire was extinguished in 30 seconds against the standard of extinguishing in 70 seconds or less.

  Moreover, regarding the coating damage of the optical fiber core wire 11a, significant damage can be prevented if the Young's modulus of the coating layer of the ultraviolet curable resin on the glass fiber is 200 MPa or more. However, when the Young's modulus of the jacket is too high, the bending rigidity increases and the flexibility of the cable deteriorates. Moreover, it is preferable that Young's modulus shall be 1500 Mpa or less also from a viewpoint of preventing that the elongation at break becomes lower and it is easy to crack when the Young's modulus becomes higher. Furthermore, if the Young's modulus of the jacket is high, the elongation at break is also low. Therefore, the Young's modulus is desirably 1200 MPa or less from the viewpoint of long-term reliability.

(Comparative Example 1)
The structure of the optical cable is the same as that of the embodiment shown in FIG. 1, but the thermoplastic resin of the cable jacket 16 is made of V0, which has a Young's modulus of 100 MPa and has a break elongation of 200%, which is more flame retardant than V2 in UL standard. A flammable halogen-free polyolefin resin was used. The optical fiber core wire 11 is a two-layer coating shown in FIG. 1A, and is an ultraviolet curable acrylate resin having a Young's modulus of 1 MPa and an elongation at break of 100% up to an outer diameter of 200 μm. Then, the secondary coating layer 13b was formed with an ultraviolet curable acrylate resin having a Young's modulus of 800 MPa and an elongation at break of 56% up to an outer diameter of 245 μm. Then, on the secondary coating layer 13b, a colored layer 14, overturned the Young's modulus 1200MPa in breaking elongation of 2% UV curable acrylate resin to an outer diameter 255Myuemu.

  As a result of testing the optical cable formed as described above by the method shown in FIG. 1B, the crushing rate of the cable jacket was 50%. Moreover, peeling of the ultraviolet curable resin coating was observed at the interface of the optical fiber core wire with the glass, and the colored layer 14 was also damaged. As a result of performing a temperature test of (−40 ° C. to 125 ° C.) × 3 cycles, an increase Δα in transmission loss was 0.02 dB / 20 m. Moreover, in the flame-retardant test as a cable (ISO 6722 45 ° inclination test), the fire was extinguished in 25 seconds against the standard of extinguishing in 70 seconds or less.

(Comparative Example 2)
The structure of the optical cable is the same as that of the embodiment shown in FIG. 1, and the thermoplastic resin of the cable jacket 16 does not contain the halogen having the flame retardancy of V2 in the UL standard with the same Young's modulus of 1200 MPa and the elongation at break of 100%. A polyamide-based nylon resin was used (different from Comparative Example 1). The coating layer of the optical fiber core 11 is the two-layer coating of FIG. 1A, and the primary coating layer 13a is formed with an ultraviolet curable acrylate resin having a Young's modulus of 1 MPa and a breaking elongation of 100% up to an outer diameter of 200 μm. Further, the secondary coating layer 13b was formed with an ultraviolet curable acrylate resin having a Young's modulus of 800 MPa and an elongation at break of 56% up to an outer diameter of 245 μm. Then, on the secondary coating layer 13b, a colored layer 14, an outer diameter of 255μm overturned be in breaking elongation of 2% UV curable acrylate resin with a Young's modulus 1200MPa up (Comparative Example 1 and the same).

  As a result of testing the optical cable formed as described above by the method shown in FIG. 1B, the crushing rate of the cable jacket was 15%. However, the UV curable resin coating was peeled off at the interface of the optical fiber core wire with the glass, and the colored layer 14 was also damaged. As a result of performing a temperature test of (−40 ° C. to 125 ° C.) × 3 cycles, an increase Δα in transmission loss was 0.02 dB / 20 m. Moreover, in the flame-retardant test as a cable (ISO 6722 45 ° inclination test), the fire was extinguished in 35 seconds against the standard of extinguishing in 70 seconds or less.

Table 1 shown below is an optical cable implementation Rei及 beauty Comparative Examples 1 and 2 described above, the cable jacket of the collapse rate, (confirmed by tentacles or visual) damage of the presence or absence of light Faiaba core, transmission by the thermal cycle test This shows the result of comprehensively judging the amount of increase in loss. In the example , a nylon resin having a Young's modulus of 1200 MPa and a breaking elongation of 100% is used for the cable jacket, and the shape and material of the coating layer of the optical fiber core wire are different from those of the comparative example . Further, Comparative Example 1 and 2, the optical fiber and the same, are made different cable jacket.

From the results shown in Table 1, in any case, a temperature test of (−40 ° C. to 125 ° C.) × 3 cycles gave practically no problem. In the embodiment , the transmission loss is increased to 0.3 dB / 20 m as compared with the comparative example, but it is within an allowable range for optical LAN communication and inter-device wiring used within a range of about 20 m. is there. As for the impact test, in the examples, the crushing rate of the outer sheath is cleared to 25% or less, and neither the core layer of the optical fiber core wire nor the colored layer is found to be damaged. The judgment was (good). In Comparative Example 2, the crush rate of the outer cover was cleared to 25% or less, but the colored layer of the optical fiber core wire was damaged, and the overall judgment was (bad).

It is a figure explaining an example of the optical cable by this invention. It is a figure explaining the Example of the optical cable by this invention .

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Optical cable 11, 11a, 11b, 11c ... Optical fiber core wire, 12 ... Glass fiber, 13, 13a, 13b ... Covering layer, 14 ... Colored layer, 15 ... Protective layer, 16 ... Cable jacket, 17 ... Tension Member, 18 ... metal rod, 19 ... weight.

Claims (2)

Young's modulus of quartz glass directly above the optical fibers composed primarily coats the above ultraviolet curing resin 200 MPa, the optical fiber center with a colored layer coated elongation at break immediately above the consists of 2% or more of the ultraviolet curable resin An optical cable characterized in that a jacket is formed by coating a thermoplastic resin having a flame retardancy of V2 or more according to UL standards and a Young's modulus of 200 MPa or more on a wire.   The optical cable according to claim 1, wherein the outer sheath does not contain halogen and has a rectangular or elliptical cross-sectional outer shape.

Images