JPH0548409B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting a break point in an optical fiber cable.

Recently, data transmission using optical fibers has been increasing. Optical fiber cables have the advantage of being able to transmit large amounts of data even with thin wires, but they are not as strong against external mechanical forces as electric wires, and if bent within a certain bending radius, the internal fibers may crack and transmission may occur. Loss increases, making it unusable as a transmission line. In this case, since no trace remains on the cable sheath, the breakage point cannot be discovered by visual inspection.

For this reason, an optical fault locator is used as a disconnection detector to locate the disconnection point. The optical fault locator is based on the fact that the reflected light level at the light emitting part decreases as the reflection point becomes farther away, as shown in Figure 1, and that if there is a disconnection point, the reflected light level will change to the reflected light level at point A. This takes advantage of the fact that the wire is rising, and it is possible to locate the point of disconnection.

However, such optical fault locators only provide distance data of the break point, and the actual location of the break can be determined by measuring the approximate cable length and assuming that it exists within a certain range. This is just a guess, and repair would require cutting the cable in that area and connecting a new cable in two places. Another problem is that it takes time to arrange cables for repair, and during that time the transmission line cannot be used, or a spare cable must be prepared.

The present invention was made to solve the above problems, and uses a strong electric field generator and an optical fault locator to change the refractive index of the optical fiber to accurately locate the break point. It is an object of the present invention to provide an optical fiber cable breakage point detection method that can be easily detected.

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 2 shows an embodiment of the present invention, in which 1 is an optical fault locator and 2 is a strong electric field generator. The strong electric field generator 2 is installed at the required points of the cable 3,
For example, as a result of the orientation by the locator 1, it is placed near a position that is considered to be a disconnection point.

Therefore, when detecting a disconnection point, the disconnection point is first located using only the optical fault locator 1, and the distance of the disconnection point is determined from the steep rise of the reflected light level in FIG. 1 or 3 (dotted line).

Next, a position corresponding to the above-mentioned distance is estimated from the drawing, and the strong electric field generator 2 is placed in the vicinity thereof and at a known distance from the drawing, for example, at point B.
When a strong electric field is applied to the fiber 3a, which is the core wire of the cable 3, by the strong electric field generator 2, and the optical fault locator 1 is operated again in this state, the refractive index of the optical fiber 3a at that point changes to Kerr.
Because of the change due to the effect, the display of the locator 1 becomes a display in which the level of reflected light is one step lower than the normal level on the light receiving end side from point B, as shown by the solid line in FIG. This sudden drop point is point B, and its distance can be known.

Thereafter, by finding the difference in distance between points A and B and actually measuring from point B, point A, which is the disconnection point, can be accurately determined. For this reason, only a small portion is removed, and it is possible to connect without replenishing new cables.
Moreover, since there is only one connection point, repairs can be made in a short time.

As described above, according to the present invention, a strong electric field is applied to the optical fiber using a strong electric field generator to artificially change the refractive index of the optical fiber at that point, and the optical fault locator performs the locating operation. and
We determined the difference between the distance at that time and the distance when locating using only the locator, and measured this difference from the installation point of the strong electric field generator, so we could accurately locate the disconnection point.
and can be easily detected. Therefore, only a small portion is required to be removed, and the repair can be performed by connecting the cables on both sides of the removed portion, thereby significantly shortening the repair period.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of display of an optical fault locator, FIG. 2 is a schematic diagram showing an embodiment of the optical fiber cable break point detection method according to the present invention, and FIG.
The figure is a diagram showing a display example of the optical fault locator in the same embodiment. 1... Optical fault locator, 2... Strong electric field generator, 3... Optical fiber cable, 3a... Fiber core wire.

Claims (1)

[Claims] 1. An optical fault/optical fiber cable is provided at one end of the optical fiber cable.
Install a locator, send light from this installation point to the optical fiber cable where the break point is to be detected, measure the level of reflected light from the break point or artificial refractive index change point, and set the optical fault locator. The distance from the point of disconnection or artificial refractive index change point is determined, and by this location, the distance is determined near the point where the disconnection point or artificial refractive index change point is considered to be, and from the installation point of the optical fault locator. A strong electric field generator is placed at a position where the actual distance is known, the refractive index of the optical fiber is changed by the strong electric field generator, and the light generated by the strong electric field generator is transmitted from the installation point using the optical fault locator. The distance to the refractive index change point of the fiber is determined, and the determined distance to the break point or artificial refractive index change point by the above two orientations and the determined distance to the refractive index change point by the strong electric field generator are calculated. Find the actual break point of the optical fiber or the artificial refractive index change point from the difference between the actual distance from the installation point of the optical fault locator to the strong electric field generator for which the distance is known and the two reference distances. A method for detecting an optical fiber cable breakage point.