JPH0373841B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure for retaining an optical fiber unit within an optical submarine cable coupling.

In the long-distance optical submarine cable system that uses optical submarine cables, optical submarine repeaters are connected every few tens of kilometers to reproduce the signal. The optical submarine cable and the optical submarine repeater are mechanically and electrically connected by an optical submarine cable coupling attached to the terminal of the cable. Optical fibers used in optical submarine cables are housed in the center of the optical submarine cable in the form of several or more optical fiber cores twisted around a central tensile strength member (hereinafter referred to as an optical fiber unit). Tension is applied to the optical submarine cable, and when the optical submarine cable stretches, the optical fiber unit housed inside also stretches.

If the elongation of the optical fiber unit is not equal to the elongation of the cable, a shift will occur between the two at the end of the optical submarine cable, and the optical fiber unit will be drawn into the optical submarine cable. The optical submarine repeater enclosure has a feedthrough portion to which the optical fiber is fixed to the end surface of the enclosure, in order to introduce the optical fiber into the enclosure.

Therefore, if the optical fiber unit is pulled in, the coating of nylon or the like has been removed from the optical fiber at the feedthrough portion, and even a slight tension may cause the optical fiber to break near the feedthrough portion.

In order to solve this problem, the present invention has been developed to pass the optical fiber unit from an optical submarine cable through a spiral metal pipe called a tail cable, which has an inner diameter slightly larger than the outer diameter of the unit, without unraveling it. An optical fiber unit retaining structure for an optical submarine repeater that retains the entire optical fiber unit and prevents the optical fiber unit from being drawn into the optical submarine cable by connecting the other end of this tail cable to the feedthrough part. It provides:

The present invention will be explained in detail below using the drawings.

1 and 2 are examples of an optical submarine cable and an optical fiber unit for explaining the present invention. 1
is an optical fiber unit, 2 is a three-part pipe, 3 is a tensile strength member, 4 is a metal tube, 5 is an insulator, 6 is an external jacket, 7 is a central tensile strength member, 8 is an optical fiber core wire, and 9 is a buffer material. . In this cable structure example, after the cable is manufactured, the optical fiber unit 1 receives a very slight uniform side pressure from the surroundings from the three-part pipe 2, and when an attempt is made to pull out the optical fiber unit 1 from the cable, an amount equivalent to a frictional force Requires pulling force. This frictional force is small for a cable unit length, but when it reaches a length of several tens of kilometers like an optical submarine cable, it becomes a considerably large force.
Therefore, cable elongation and optical fiber unit 1
The elongation of is equal at each point. That is, since there is an infinitely long cable on both sides at each cable point, there is no misalignment between the optical submarine cable and the optical fiber unit.

However, in optical submarine cable couplings, the condition that an infinitely long cable exists on the repeater side does not hold true, so a considerable tension acts on the optical fiber in the feedthrough section, which is undesirable.

For this reason, the present invention provides an optical fiber unit, which is located between an optical submarine cable coupling and an optical submarine repeater, and which connects the optical fiber unit continuously led out from the optical submarine cable coupling to a metal having an inner diameter slightly larger than the outer diameter of the optical fiber unit. After penetrating the pipe, it is formed into a spiral shape, and the frictional force between the outer surface of the optical fiber unit within this forming portion and the inner wall of the metal pipe prevents the optical fiber unit from being drawn into the cable in stages.

FIG. 3 is for explaining the present invention.
is an optical submarine cable, 11 is a boot, 12 is an anchor that holds the tensile strength member 3 of the optical submarine cable, 13 is a gimbal that forms a universal joint, and 14 is a straight section of a metal pipe called a tail cable, partially showing the inside in cross section. However, it is actually fixed to the anchor 12. 15 is the spiral part of the tail cable,
16 is the part where the tail cable begins to form into a spiral shape, 17 is the feedthrough part of the optical submarine repeater body, 18 is the insulator, 19 is the anchor housing, 20 is the rubber bellows, and 21 is the optical submarine repeater body. It is a part of.

The creation of the retaining structure for the optical fiber unit of the present invention will be explained. First, the tensile strength member of the optical submarine cable is held in place by the anchor 12, and then the metal pipes 14, 15, and 16 are passed through the optical fiber unit located on the repeater side from the anchor 12, and the cable side of the metal pipe 14 is attached to the anchor 12. This part is then molded with an insulator 18 to insulate it from seawater. Next, after passing the straight part 14 of the tail cable through the gimbal 13, rubber bellows 20, etc.,
By forming the metal pipe 15 into a spiral shape from the part and connecting the tip to the feedthrough part 17, the optical fiber unit is introduced into the interior of the optical submarine repeater enclosure 21 without being separated. The dimensional relationship between the outer diameter of the optical fiber unit and the inner diameter of the pipe is selected so that the optical fiber unit can only be inserted into a straight pipe. The inner diameter of the metal pipes 14, 15, 16 of the tail cable is approximately 20% larger than the outer diameter of the optical fiber unit at most, and it is desirable for the curvature of the forming rising portion 16 to be as large as possible in terms of transmission characteristics.

1 and 2 in Figure 4 are characteristics showing the relationship between the tension applied to the optical fiber unit and the length of the optical fiber unit drawn into the tail cable when the number of turns of the tail cable is set to 1 and 3, respectively. .

Figure 5 shows an outline of the experiment. Tail cable 2
2 is fixed in a vise 23, and tension is applied to the optical fiber unit 1 in the direction of the arrow. According to FIG. 4, it is understood that even if the number of turns of the tail cable is one, the retraction length at a tension of 35 kg is as small as 2 mm, and when there are three turns, there is no retraction at all.

Further, according to the present invention, while holding the optical fiber unit and applying tension to the optical submarine cable,
When we investigated changes in optical loss, we found that there was almost no change in loss even at tensions exceeding 30 kg. That is, the optical fiber unit retaining structure according to the present invention provides an optical fiber unit retaining structure in an optical submarine cable coupling that is simple in structure, economical, and has good characteristics.

Note that the portion 14, 1 described as a metal pipe
The pipes 5 and 16 do not necessarily have to be metal pipes, but may be pipes made of other materials such as composite materials such as reinforced plastics as long as the desired frictional force can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of an optical submarine cable to which the present invention applies, FIG. 2 is a cross-sectional view showing an example of the structure of an optical fiber unit to which the present invention applies, and FIG.
4 is a longitudinal cross-sectional view showing the structure of an optical submarine cable coupling according to an embodiment of the present invention, FIG. 4 is a characteristic diagram for explaining the effects of the present invention, and FIG. 5 is an experimental example for explaining the effects of the present invention. This is a schematic diagram. 1... Optical fiber unit, 2... 3-split pipe, 3... Tensile strength wire, 4... Metal tube, 5...
... Insulator, 6 ... External jacket, 7 ... Central tensile strength member, 8 ... Optical fiber core wire, 9 ... Cushioning material,
10... Optical submarine cable, 11... Boots, 12
...Anchor, 13...Gimbal, 14...Straight metal pipe part of the tail cable, 15...Spiral part of the metal pipe of the tail cable, 16...
Part where the metal pipe of the tail cable begins to form into a spiral shape, 17... Feedthrough portion, 18... Insulator, 19... Anchor housing, 20... Rubber bellows, 21... Optical submarine repeater body, 22 ...Tail cable, 23...
vise.

Claims (1)

[Scope of Claims] 1. An anchor housing part for anchoring an optical submarine cable, and a plurality of optical fibers twisted around a central tensile line inside the optical submarine repeater case and arranged in a cushioning material. In an optical fiber unit retaining structure for an optical submarine repeater, the structure includes a feedthrough part for introducing the fiber unit in the state, and a gimbal part forming a universal joint between the anchor housing part and the optical submarine repeater enclosure. , a tail cable having a structure in which a pipe having an inner diameter slightly larger than an outer diameter of the fiber unit is arranged around the outer periphery of the fiber unit between the anchor housing part and the feedthrough part of the optical submarine repeater body. When the anchor housing part and the feedthrough part of the optical submarine repeater housing are fixed to each other, the tail cable is formed in a spiral shape near the introduction of the feedthrough part, and tension is applied to the anchor housing part. The fiber unit is configured such that the amount by which the fiber unit is drawn into the optical submarine cable is reduced to a negligible extent at the feedthrough portion due to the frictional force acting between the outer surface of the fiber unit and the inner wall of the spiral tail cable. An optical fiber unit anchoring structure for an optical submarine repeater, characterized by the following.