JP2003066293A - Optical fiber cable containing water infiltration detecting line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber cable containing water infiltration detecting lines rapidly detecting water infiltration while securing the number of communication optical fiber lines. SOLUTION: Grooves 3 for communication lines to contain the communication optical fibers 4 and grooves 7 for detecting lines to contain the water infiltration detecting optical fibers 8 are formed on an outer circumference of a spacer 2 to be used as a cable core 11 and a swelling member 9 to be swollen with water is contained in the groove 7 for the detecting line in addition to the water infiltration detecting optical fiber 8. All the communication optical fibers 4 in the groove 3 for the communication lines are secured for the communication and, at the same time, the water infiltration is rapidly detected with the water infiltration detecting optical fibers 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber cable with a water immersion detection line for detecting the intrusion of water into a cable, and more particularly to a water immersion detection that secures the number of optical fibers for communication and speeds up the detection. The present invention relates to an optical fiber cable containing a wire.

[0002]

2. Description of the Related Art As shown in FIG. 4, in a conventional optical fiber cable with a water leak detection line, a tension member 1 for supporting the structure in the longitudinal direction of the cable is arranged in the central portion of the cable cross section, and the tension member is also provided. 1, a spacer 2 for supporting the radial structure of the cable is arranged, a groove 3 is formed on the outer periphery of the spacer 2, and a plurality of communication optical fibers 4 are housed in the groove 3 2 is an optical fiber cable in which a swelling tape 5 that swells with water is wrapped around the outer periphery of the cable core to form a cable core, and a sheath 6 is applied to the outer periphery of the cable core. The grooves 3 of the spacer 2 are formed at appropriate intervals at a plurality of positions in the circumferential direction.
As the communication optical fiber 4, a tape fiber core wire in which a plurality of optical fiber core wires are arranged in parallel and collected in a tape shape is used. Then, one or a plurality of the tape fiber core wires are housed in the groove.

Usually, among the plurality of tape fiber cores in the groove 3, one or several optical fiber cores of the tape fiber cores located in the outermost layer are used as an optical fiber for detecting water immersion.

When the sheath 6 of the optical fiber cable with such a water leak detection line is punctured or damaged and water enters the inside of the sheath, the swelling tape 5 in the cable absorbs the water. It can be seen that the swelling causes lateral pressure to be applied to the optical fiber for water detection, and the transmission loss increases, so that water enters the inside of the cable.

[0005]

By the way, in the above-mentioned conventional optical fiber cable with water intrusion detection line, the optical fiber for detecting intrusion is allocated by diverting a part of the optical fiber for communication. As the number of communication optical fibers required increases, the number of optical fibers allocated for water immersion detection decreases.

If the optical fiber for detecting water immersion is assigned to only one groove, and if water enters due to a hole or external damage in the sheath in the vicinity of this optical fiber for water immersion detection, water for detecting water infiltration is detected. It is immediately apparent that water has infiltrated into the cable due to the fact that the water absorption swelling tape in the vicinity of the optical fiber swells and lateral pressure is applied to the optical fiber for water detection, increasing transmission loss. However, when water enters the portion on the side opposite to the groove into which the water detection optical fiber is inserted, it takes time until the transmission loss of the water detection optical fiber increases.

On the contrary, if the optical fibers for water immersion detection are assigned to all the grooves, the number of optical fibers that can be used for communication is limited accordingly.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and to provide an optical fiber cable with a water-immersion detection line, which enables rapid detection while securing the number of communication optical fibers.

[0009]

In order to achieve the above object, the present invention provides a communication line groove for accommodating a communication optical fiber and a detection line for accommodating a water immersion detection optical fiber on the outer periphery of a spacer which is a cable core. And a swelling member that swells with water along with the optical fiber for detecting water immersion is housed in the groove for detection line.

A convex portion may be provided in the detection line groove to press the water immersion detection optical fiber against the swelling member.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in FIG. 1, in the optical fiber cable with a water immersion detection line according to the present invention, a tension member 1 for supporting the structure of the cable in the longitudinal direction is arranged in the central portion of the cable cross section, and the tension member is also provided. 1
A cable core is formed by arranging a spacer 2 supporting the structure in the radial direction of the cable around the periphery of the cable, and a communication wire groove 3 and a detection wire groove 7 are formed on the outer periphery of the spacer 2 to form a communication wire groove. A plurality of optical fibers 4 for communication are housed in 3 and one or a plurality of optical fibers 8 for detecting water and a swelling member (also referred to as swelling interposition) 9 are superposed in a groove 7 for a detection line. The cable core 11 is housed and wound around the outer periphery of the spacer 2 with a pressure winding tape 10 made of plastic or the like to form a cable core 11.
Further, the outer circumference of the cable core 11 is provided with a sheath 6. The communication line groove 3 is formed at a plurality of positions in the circumferential direction at appropriate intervals, and the detection line groove 7 is formed in the middle of each communication line groove 3. In the illustrated example, the detection line groove 7 is arranged in the center between the communication line grooves 3, but it may be arranged on one side. Further, although the number of the communication line grooves 3 and the number of the detection line grooves 7 are the same, they may be different. In the communication optical fiber 4,
A tape fiber core wire in which a plurality of optical fiber core wires are arranged in parallel and collected in a tape shape is used. Then, one or a plurality of the tape fiber core wires are housed in the groove. The water immersion detection optical fiber 8 may be a single-core optical fiber core wire.

When water enters the inside of the cable 6 due to puncture or external damage due to aging or corrosion, the sheath 6 of the optical fiber cable containing the water detection line is in the groove 7 for the detection line. Since the swelling member 9 accommodated in the swelling absorbs water and swells, lateral pressure is applied to the optical fiber 8 for detecting water immersion sandwiched between the swelling member 9 and the bottom surface of the groove 7 for detection line, and transmission loss increases. It can be seen that water has penetrated inside the cable.

Compared with the conventional optical fiber cable with a water immersion detection line, the optical fiber cable with a water immersion detection line of the present invention has the optical fiber 8 for water detection provided at a location different from the optical fiber 4 for communication. All communication optical fibers 4
Can be used for communication without restriction, and moreover, since a plurality of optical fibers 8 for detecting water immersion are secured and distributed in the circumferential direction of the cable, it is possible to detect water infiltration quickly regardless of the location of water immersion.

Further, in the optical fiber cable with a water immersion detection line of the present invention, as shown in FIG. 2, a projection may be provided on the bottom surface of the detection line groove 7. In the example of FIG. 2, as the convex portion,
Wavefront-shaped irregularities 12 that repeat at regular intervals are formed in the longitudinal direction of the detection line groove 7. When the swelling member 9 swells, the irregularities 12 oppose the swelling member 9 and press the optical fiber 8 for water detection. For this reason, the transmission loss is significantly increased as compared with the case where the bottom surface of the detection wire groove 7 is flat, and the water immersion can be detected more swiftly and reliably.

The optical fiber cable with a water immersion detection line shown in FIG. 3 has a metal wire 13 embedded in the bottom surface of the detection wire groove 7. This metal wire 13 also forms a convex portion on the bottom surface of the detection wire groove 7. That is, when the swelling member 9 swells, the metal wire 13 presses the water immersion detection optical fiber 8 against the swelling member 9, so that the transmission loss remarkably increases.

[0017]

The present invention exhibits the following excellent effects.

(1) Since the detection line groove is provided separately from the communication line groove and the water immersion detection optical fiber is arranged, it is not necessary to allocate the communication optical fiber in the communication line groove for water detection. It is possible to secure a large number of communication optical fibers.

(2) Since a plurality of detection wire grooves are provided and the optical fibers for water detection are distributed in the circumferential direction of the cable, the water can be detected quickly.

(3) Since the projections and depressions formed on the bottom surface of the groove for the detection wire and the projections (projections (wires)) press against the swelling member and press the optical fiber for detecting water, the transmission loss increases remarkably. It is possible to reliably detect inundation.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an optical fiber cable with a water immersion detection line showing an embodiment of the present invention.

FIG. 2 is a side sectional view of a detection wire groove showing another embodiment of the present invention.

FIG. 3 is a cross-sectional view of an optical fiber cable with a water immersion detection line showing another embodiment of the present invention.

FIG. 4 is a cross-sectional view of a conventional optical fiber cable with a water immersion detection line.

[Explanation of symbols]

1 tension member 2 spacer Groove for 3 communication lines 4 Optical fiber for communication 7 Detection line groove 8 Optical fiber for water immersion detection 9 Swelling member 11 cable core 12 unevenness (convex part) 13 Metal wire (projection)

Claims (2)

[Claims] 1. A communication line groove for accommodating a communication optical fiber and a detection wire groove for accommodating a water immersion detection optical fiber are formed on the outer periphery of a spacer that serves as a cable core, and the groove is formed in the detection line groove. An optical fiber cable with a water immersion detection line, characterized in that a swelling member that swells with water is stored along with the optical fiber for water immersion detection. 2. The optical fiber cable with a water immersion detection line according to claim 1, wherein a convex portion for pressing the optical fiber for water detection against the swelling member is provided in the groove for the detection wire.