JPS608483B2 - Optical submarine cable - Google Patents

Description

[Detailed description of the invention] The present invention relates to an optical submarine cable.

In recent years, optical fiber transmission has come to be used instead of conventional signal transmission using conductors.

Optical fiber cables, which are made up of optical fibers, have features such as lower loss, smaller diameter, and lighter weight than conventional cables made of steel wires or cables made of coaxial conductors. It is very advantageous when used for long/rectangular distance transmission, and has many advantages especially when used for submarine cables. Since submarine cables are required to withstand pressure and tensile strength, optical submarine cables of various structures are currently used, the typical one of which is the structure shown in FIG. That is, a polyethylene sheath 1 is provided as the outermost layer to protect the cable from external mechanical forces, and inside it, tensile strength wires 2 are installed along the length or twisted together to withstand the tension applied to the cable during cable installation. by 1
~2 layers are provided.

Further, a pressure-resistant pipe 3, usually made of copper wire, is provided inside the pipe 3 to withstand the enormous water pressure in the deep seabed, and optical fibers and the like are housed and protected inside the pressure-resistant pipe 3.
Inside the pressure-resistant pipe 3, as shown in FIG. 2, a plurality of optical fibers 4 are arranged and assembled around a central tensile wire 5, either longitudinally or by being twisted.

In order to ensure good adhesion between the optical fiber strand 4 and the tensile strength wire 5 and the pressure-resistant pipe 3, the outer diameter of the pressure-resistant pipe 3 is slightly reduced to appropriately compress the optical fiber strand 4. It is formed. Some pressure-resistant pipes 3 are of a split type, but in this case, the pipe is formed in a shape and size that appropriately compresses the inner fiber east line when water pressure is applied. However, as shown in FIG. 3, the conventional fiber wire 4 is
It has a layered structure in which a buffer layer 7 made of silicone rubber or the like is provided around the outer periphery of the optical fiber core 6 at the center, and a plastic coating 8 made of nylon or the like having a uniform thickness is provided around the outer periphery.

That is, the outer diameter is uniform along the axial direction. For this reason, the optical fiber strands 4 gathered around the tensile strength line 5 on the east side are almost uniform, and when inserted into the pressure-resistant pipe 3, as shown in FIG. In addition, a portion 9 of the optical fiber Qin line east having a slightly larger outer diameter is in contact with the inner surface of the pressure-resistant pipe.

As a result, in order to maintain the adhesion between the inner surface of the pressure-resistant pipe 3 and the optical fiber strand 4 over the entire length of the cable, the inner diameter of the pressure-resistant pipe 3 must be made considerably thinner and the optical fiber strand 4 must be compressed. No. When the optical fiber wire 4 is subjected to excessive pressure, there is a drawback that optical transmission loss increases and, in severe cases, there is a risk of wire breakage. In addition, if the above-mentioned pressure is insufficient, the adhesion between the pressure-resistant pipe and the optical fiber wire becomes insufficient, and when the optical submarine cable is held vertically in the sea, the optical fiber wire 4 and the tensile strength wire 5 The disadvantage is that the tension generated by the weight becomes greater than the frictional force with the pressure-resistant pipe, causing the east end of the optical fiber wire to "slip" within the pipe, which may cause the optical fiber trunk wire to break. In this way, the pressure between the pressure-resistant pipe and the optical fiber bundle is neither too high nor too low, and with conventional cables, it is extremely difficult to obtain good adhesion over the entire length of the cable.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide an optical submarine cable in which the pressure-resistant pipe and the optical fiber east are in good contact over the entire length of the cable. The cable of the present invention includes an optical fiber strand east in which a plurality of optical fiber strands each having a plastic coating whose thickness is not uniform along the direction of the bag are combined, and a pressure resistant cable for accommodating the strand east. pipe, and is configured such that the contact pressure between the large outer diameter portion of the east strand and the pressure-resistant pipe becomes the main frictional force.

Next, the present invention will be explained in detail with reference to the drawings.

First, as in the past, a buffer layer 7 made of silicone rubber or the like is provided on the outer periphery of the optical fiber core 6, and then a plastic coating with uneven thickness in the direction of the circumference is provided on the outer periphery to form the optical fiber element. Form line 4. That is, the plastic coating is thickened periodically or randomly along the axial direction. It is desirable that each of the plurality of optical fiber strands be coated with thick coating parts at different intervals or randomly, but when there are many optical fiber strands 4, the thickness distribution of each fiber is the same. It's okay. FIG. 5 shows a state in which a required number of the optical fibers 4 are gathered together around the tensile strength wire 5 and inserted into the pressure-resistant pipe 3.

In other words, the outer diameter of the east optical fiber is divided into thick and thin parts along the axial direction, and the thick parts are randomly distributed along the axial direction, and the thick parts are distributed randomly along the axial direction. It contacts the inner surface of the pressure-resistant pipe 3 at a contact point 9 . By squeezing the pressure-resistant pipe 3, the contact point 9 is compressed, and good adhesion between the pressure-resistant pipe 3 and the optical fiber 4 inside can be obtained. The contact points 9 are randomly scattered along the axial direction, and the frictional force generated at these contact points is used as the main frictional force to maintain the adhesion between the pipe 3 and the optical fiber assembly. This greatly improves the tensile strength of the optical fiber as a whole. Furthermore, by assembling the tensile strength wires 2 on the outside of the pipe 3 as in the conventional case and providing the polyethylene coating 1 on the outermost layer, an optical submarine cable having the same outer diameter as the conventional cable is formed. The tensile strength of the cable is maintained primarily by the tensile strength wires 2 and protected from mechanical damage by the polyethylene jacket 1. With the above-described structure, the pressure-resistant pipe 3
Since the optical fiber does not shift inside the
Unlike the conventional method, there is no risk that only the optical fiber wire will be cut before the entire cable is cut. Further, the stress applied to the contact point 9 is not a single point concentrated stress, and the contact point 9 is a thick part of the plastic coating and has high elasticity, so the stress applied to the optical fiber core 6 is relatively small. There is no risk of breakage of the optical fiber core wire 6 or increase of optical loss due to stress. As described above, in the present invention, the thick parts of the optical fiber plastic coating are scattered in the axial direction to ensure sufficient contact pressure with the pressure-resistant pipe. Adhesion with the pressure-resistant pipe is good, and there is no risk of wire breakage or increase in transmission loss. Brief explanation of the drawings Figure 1 is a cross-sectional view of a conventional deep-sea optical submarine cable, Figure 2 is a cross-sectional view of the inside of the pressure-resistant pipe shown in Figure 1, and Figure 3 is a cross-sectional view of a conventional optical fiber wire. FIG. 4 is a cross-sectional view of the inside of a conventional pressure-resistant pipe along the bag direction, and FIG. 5 is a cross-sectional view of the inside of the pressure-resistant pipe along the axial direction showing an embodiment of the present invention.

In the figure, 1... polyethylene coating, 2... tensile strength wire, 3... pressure resistant pipe, 4 optical fiber Qin wire, 5...
・Central tensile strength wire, 6 optical fiber core wire, 7...buffer wire, 8
...Plastic coating, 9...Contact point. Tsutomu' Zutsumu 2
Figure 4 Figure 4 Tsutomata

Claims (1)

[Claims] 1. An optical fiber bundle consisting of a plurality of optical fibers each having a plastic coating with a non-uniform thickness along the axial direction, and a pressure-resistant pipe for accommodating the fiber bundle; An optical submarine cable characterized in that the optical submarine cable is configured such that a contact pressure between a portion of the wire bundle having a large outer diameter and the pressure-resistant pipe serves as a main frictional force.