JPH0440684B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a water-shielding optical fiber cable using a filling for preventing water running. [Prior Art] A water-shielding optical fiber cable having a structure in which the space between a water-shielding layer and a large number of optical fibers present inside the water-shielding layer is filled with a filler for preventing water running is conventionally known. . Conventionally used fillers to prevent water running are melted at high temperatures, solidified when brought to room temperature, and cracks occur due to volumetric shrinkage as the filler cools, resulting in water running. In fiber optic cables, the shrinkage may result in microbends in the fiber, or where a high degree of precision is required due to the difficulty of removing the solidified filler from the cable. There are problems such as various inconveniences that occur during terminal processing. [Summary of the Invention] The present invention proposes a novel water-shielded optical fiber cable that does not have the above-mentioned problems. The space between the two is filled with grease to prevent water running, and the grease has a miscibility of 200 to 400 at room temperature as measured by ASTM D-217. be. [More detailed description of the present invention based on embodiments] The attached figure is a cross-sectional view of an embodiment of the present invention, in which a tension member 11 made of organic polymer fibers such as Kevlar, FRP, or metal wire is inserted into the middle. The 8 units of the 6-core optical fiber unit 1, which is made by collecting 6 optical fibers 12 and further winding the tape 13 on top of the 6 optical fibers 12, are made of rubber, plastic or fiber-reinforced rubber, plastic rods, metal wires, or organic fibers. Tension member 2 made of polymer fiber etc.
A water-blocking layer 3 is formed by vertically attaching a laminated tape made of metal such as aluminum or lead on top of the water-blocking layer 3, and a layer of polyethylene, polyethylene, etc. An extruded protective sheath layer 4 made of a sheath material such as vinyl chloride is applied, and the inner space of the water-shielding longitudinal splint layer 3 is filled with grease 5 for preventing running of water. The water-shielding longitudinal splint layer 3 may be omitted and the extruded protective sheath layer 4 may also serve as a water-shielding layer. In the present invention, as grease 5, ASTM
The degree of miscibility at room temperature measured with D-217 is 200
~475 are used. Those with a miscibility of less than 200 are too hard and must be heated to high temperatures to increase fluidity for efficient filling of cables, and such heating necessarily This is accompanied by cooling that causes a large and disgusting volumetric contraction. On the other hand, if the miscibility is too high, if the cable is installed vertically or at an angle due to excessive fluidity, the water head pressure may flow down within the cable and cause damage to the sheath inside the lower cable section. Otherwise, it may cause air gaps in the upper cable section, which may cause problems in preventing water running. Therefore, as the grease 5, one having a miscibility degree of 200 to 400 at room temperature is used. Regardless of the chemical composition or structure, as long as it has the above-mentioned miscibility and anti-hydrotactic effect,
Various greases are used. However, the term "grease" as used in the present invention refers to lubricating oil in which a thickening agent is dispersed to make it semi-solid or solid. The present invention does not apply to the mixture obtained by mixing, which looks like grease. Examples of grease include the following greases having the above-mentioned consistency. These include calcium stone grease, aluminum stone grease, lithium stone grease, composite calcium stone grease, composite aluminum stone grease, benton grease, and polyurea grease. An optical fiber cable (outer diameter 22 mm) with an aluminum laminate water-shielding layer was manufactured, having the structure shown in the attached diagram and having 48 optical fibers made of GI-type optical fibers with a core diameter of 50 μm and a cladding diameter of 125 μm, each coated with a nylon jacket. Among these, the cable of the example was filled with calcium soap grease manufactured by Nippon Grease Co., Ltd. having a miscibility degree of 320 at room temperature as a water running prevention grease at room temperature. On the other hand, in the cable of the comparative example, 5B manufactured by Utsutco, Inc., which has been used in the past, was used as a filler for preventing water running.
Since the filler is solid at room temperature, it was melted by heating to 105°C, press-fitted between the wires, and allowed to cool at room temperature. The performance of both of the above cables is shown in the table below.
Regarding the water-shielding properties of the cable, the space between the longitudinal water-shielding layer and the outermost surface of the optical fiber unit bundle at both ends of a 2 m long cable test piece was sufficiently waterproofed using waterproof putty, and the area approximately in the center of the cable test piece was treated with waterproof putty. Strip off 25mm of the sheath and vertical waterproof layer,
A polyethylene pipe filled with water was installed at a height of 1000 mm, and after 14 days, water permeation from the center was 850 mm.
I checked to see if it was larger than mm.

[Effects of the present invention]

The water running prevention grease used in the present invention can be filled at room temperature or by heating at a lower temperature than conventionally used fillings, so there is no volumetric contraction of the grease after filling, or Since it is mild, there are fewer micro-bends in the cable and no grease cracks occur. Therefore, the cable has excellent optical transmission characteristics and water shielding properties. Not only this, but also when processing the end of the cable, since the grease is not solidified, it is easy to remove, and therefore the end processing work can be done efficiently and precisely. Furthermore, in the cable of the present invention, there is grease between the optical fibers that flows and deforms when an external force is applied, so when the cable is bent, the grease acts as a lubricant to ensure smooth bending of each optical fiber. It also has the effect of making it work.

[Brief explanation of the drawing]

The attached figure is a sectional view of an embodiment of the present invention, and shows 1
2 is an optical fiber, 3 is a water-blocking layer formed by vertically applying aluminum laminate tape, and 5 is grease for preventing water running.

Claims (1)

[Claims] 1 The space between the water-blocking layer and the large number of optical fibers present inside the water-blocking layer is filled with grease to prevent water running, and the grease is ASTM D
The mixing consistency at room temperature measured at -217 is 200~
A water-shielded optical fiber cable characterized by using 400.