JPS62105058A - Fault point detection system for optical submarine cable - Google Patents

Abstract

PURPOSE:To detect the fault point of a system by constituting a current transformer between conductors and finding the fracture point (fault point) on a conductor by a probe. CONSTITUTION:A magnetic bodies 11a or 11b obtained by dividing an ring- shaped magnetic body into two semicylindrical parts is wound with a coil 12 or 13 for transmission or reception. The magnetic bodies 11 and 11b are coupled in a ring shape so that an optical submarine cable penetrates their center, thus forming the current transformer 11. A pulse generator 16 is connected to the coil 12 through a power amplifier 15. Then, pulse currents are flowed through the coils 12 and 13 to generate an impulsive progressive wave in the conductors in an optical submarine cable, a pulse wave which is reflected at the fault point 21 to return is detected by the same or different coil as or from the coils 12 and 13 wound around the transformer 11, and the time that the pulse current requires to travels forth and back between the transformer 11 and fault point 21 is measured by a pulse interval counter 20, thus measuring the cable length up to the fault point 21.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a measurement method for detecting the location of a fault in an optical submarine cable.

(Prior Art) When repairing an optical submarine cable that has been cut for some reason, it is first necessary to know the point of failure. In the case of a non-repeater optical submarine cable system, the length of the cable from the terminal station on land to the point of failure can be determined using the optical backscatter method.

This optical backscattering method extracts the optical signal component reflected by the cross section of the optical fiber at the end station, and detects the location of the fault from its propagation time. However, in a system including a repeater, the repeater performs a regenerative repeating operation, so the optical signal is transmitted in only one direction.

Therefore, for submarine cables that include repeaters, the range that can be measured by this method is limited to between the end station and the repeater closest to the end station. Therefore, if a fault occurs in any other section, it is necessary to cut the cable once at the center of the relay section and detect the point of failure, as described below.

1) Monitor each repeater from the terminal station and find out in which relay section a failure has occurred.

2) Cut the optical submarine cable approximately in the center of the relay section where the failure occurred, and lift the cut point onto the repair ship.

3) Measure the cable length from the cut point to the fault point using the optical backscatter method.

(Problem to be Solved by the Invention) Therefore, in this method, the normal portion of the optical submarine cable is cut and reconnected, which increases the length of the split cable required for repair and increases the number of optical fiber connection points. Problems arise, such as an increase in the time and expense required for repair, and in the case of buried sections, an increase in the non-buried sections that remain after repairs.

The present application was made in order to solve these problems, and provides an optical submarine cable fault detection method that makes it possible to detect the fault location of the system without cutting the optical submarine cable. .

(Means for Solving the Problems) The features of the present invention for solving the above problems are as follows.

■ Using a probe with a coil wound around one or both of the two ring-shaped magnetic bodies, ■ Connect the two halves of the magnetic body in a ring shape so that the optical submarine cable passes through the probe. □ to form a current transformer '1, () between the coil and the optical submarine cable;
A traveling wave in the form of a mother locus is emitted to the conductor in the optical submarine cable,
*a-ti.

i □ ■ The 7 waves reflected at the failure point are detected by the same coil as the coil wound around the current transformer, or by another coil.

, 1. ■ Measuring the time required for the pulse to travel back and forth ・Measuring the cable length to the point of failure by: ・1 . 1 and, ■ A sinusoidal zero current is passed through the above °I'';■
Find the input impedance to the coil from the current and voltage flowing through the coil, ■ Measure the input impedance to the coil by changing the frequency of the sine wave, and ■ Determine the cable path to the fault point from the relationship between the input impedance to the coil and frequency. To measure length.

(Function) Optical submarine cables are equipped with conductor wires such as attendant communication lines or high-tension wires, and therefore the breaking point of the cable is equal to the breaking point of the conductor wire. In the present invention, a current transformer is constructed between the probe and the conductor wire, and the break point of the optical cable is determined by determining the break point of the conductor wire.

(Example) FIG. 1 is a sectional view showing an example of an optical submarine cable. Six optical fibers 1 and a central piano wire 2 are embedded in silicone rubber 3. The outside is protected by a three-part aluminum pressure-resistant layer 4, a tensile strength member (piano wire) 5, a copper tube 6, an insulator (low-density polyethylene) 7, and a jacket (carbon black high-density polyethylene) 8. The conductor such as the copper tube 6 is also used as a secondary conductor for feeding power to the repeater. Thus, conductors are included within the optical submarine cable and can be utilized for fault point detection according to the present invention.

FIG. 2 shows an embodiment of the present invention, in which lla and llb are ring-shaped magnetic bodies divided into two semicircular parts. This magnetic body 11a or llb has a wave transmitting and receiving coil 1.
2.13 is wound.

The magnetic bodies 11a and llb are connected in a ring shape so that an optical submarine cable passes through the center thereof, forming a current transformer 11. The work of connecting the magnetic bodies 11a and llb in this manner can be performed using a manned or unmanned submersible.

An ie pulse generator 16 is connected to the coil 12 via a power amplifier 15. At this time, the number of turns of the wave transmitting coil 12 is n2, the pulsed current flowing through the wave transmitting coil 12 is i2(t), and the magnetic body 11a.

If a material with extremely high magnetic permeability is used for 11b, the conductor (not shown) in the optical submarine cable 14a will have n2
A gust-like current represented by +2(t) is generated.

In this case, the optical submarine cable uses the inner conductor as the center conductor,
It can be regarded as a coaxial transmission line (hereinafter simply referred to as a cable) with seawater as the outer conductor. Further, the ground impedance Zr1 of the conductor in the optical submarine cable at the failure point (break point) 21 is different from the characteristic impedance Zc of the normal cable. Therefore, the pulsed current generated in the conductor within the optical submarine cable propagates along the cable, and then is partially reflected at the fault point 21. The reflection coefficient Sr1 at this time is expressed by equation (1).

r1-Zc Sr1= (1) Zr1+Zc The pulsed current that is reflected and returns in the opposite direction is detected by the receiving coil 13 of the current transformer 11. 17
is a switching circuit that prevents the signal induced by the wave transmitting coil 12 from being input directly to the 5T018 before traveling back and forth through the cable. That is, while the pulsed current 12(t) is flowing through the wave transmitting coil 12, the connection between the wave receiving coil 13 and the 5TC18 is cut off, and immediately after the current i2(t) disappears, the wave receiving coil is closed. Connect 13 and 5TC18.

The STC 18 is an amplifier whose gain increases over time to compensate for attenuation caused by pulsed current propagating through the cable.

The reflected wave detected by the receiving coil 13 is shaped by a waveform shaper 19 via a switching circuit 17 and a 5TC 18. Furthermore, the iR interval counter 20
The time τ required for the pulsed current to travel back and forth between the current transformer 11 and the fault point 21 is measured. If the propagation speed in the cable is V, then the cable length t to the failure point 21 is
1 is represented by .

Since a repeater is usually connected to the end of the optical submarine cable on the left side of the current transformer 11, reflected waves from this repeater also return to the current transformer 11. but,
If the current transformer 11 is installed in the center between the repeaters, the cable length t1 between the current transformer 11 and the fault point 21 becomes shorter than the cable length t2 between the current transformer 11 and the repeater. Therefore, the reflected wave from the repeater returns later than the reflected wave from the failure point 21, so it does not affect the measurement.

In FIG. 2, 14b represents the other end of the cut cable. Further, in this embodiment, the wave transmitting coil 12 and the wave receiving coil 13 are different, but the same coil may be used for both purposes. Alternatively, two current transformers may be prepared, one for transmitting waves and the other for receiving waves. Furthermore, it is also possible to increase the transmitting sensitivity and receiving sensitivity by using multiple current transformers in series or in parallel.

In this embodiment, the measurement is still performed using pulsed current, but i'? ) A pseudorandom signal and a correlator can also be used instead of a response. That is, in FIG.
i'? The pulse generator 16 is replaced with a pseudo-random signal generator, the waveform shaper 19 and the pulse interval counter 20 are replaced with a correlator, and the output of the pseudo-random signal generator and the reflected wave detected by the receiving coil 13 are The correlation function is determined, and the cable length t to the failure point 21 is determined from the delay time τ at which the value becomes maximum and equation (2). Note that in this case, the switching circuit 17 is unnecessary.

Furthermore, in the above method, although the cable length t between the current transformer 11 and the fault point 210 is known, the fault point 21
It is not possible to determine on which side of the current transformer 11 the current transformer 11 is located. In order to make this determination, for example, the position of the current transformer 11 may be moved to either direction along the optical submarine cable, and the cable length 1.7 between the current transformer 11 and the failure point 21 may be measured again. At this time, if t, )1.7, the fault point 21 is in the direction in which the current transformer 11 was moved, and if t,<11', the fault point 21 is in the opposite direction. I understand.

In addition, by attaching two current transformers to a cable at appropriate intervals and comparing the cable lengths between each current transformer and the fault point, it is also possible to know the direction of the fault point.

FIG. 3 shows another embodiment of the invention.

An oscillator 37 whose frequency f is variable is connected to the coil 38 via a power amplifier 36. A current 12(t) flowing through the coil 38 is converted into a voltage by a transformer 31 and a current-voltage converter 32. The voltage V 2 (t) across coil 380 is amplified by amplifier 34 . V
Z(t) and 12(t) are subjected to multiple processing by a phase comparator 33 and an amplitude comparator 35, and the input impedance to the coil 38 is determined. Input impedance Zi to coil 38
The principle of determining the cable length t from the frequency characteristic to the failure point 21 will be explained with reference to an equivalent circuit diagram 4.

In FIG. 4, Zj is the impedance when looking into the cable on the left side from the current transformer 11, and Zr is the impedance when looking into the right side from the current transformer 11. current transformer 1
On the left side of 1, there is a repeater at cable length t2, and in the repeater, the conductor in the optical submarine cable has impedance Z
Assume that it is grounded to seawater via r2. Further, as described above, the optical submarine cable in this case can be considered to be a coaxial cable with the inner conductor as the center conductor and the seawater as the outer conductor. Therefore, 21 can be expressed by the following equation.

In the above equation, Zc is the characteristic impedance of the cable, and r is the propagation constant.

Next, when the grounding impedance of the conductor in the optical submarine cable at the cutting point 21 is zrl, zr is expressed as follows.

From FIG. 4 and the above equation, the input impedance Zi to the coil 38 is as follows.

Zi = n 2 (Zr + ZL) By the way, the propagation constant γ is generally expressed by the following equation.

Ro, Lo are series resistance and inductance, Go,
C.

are parallel conductance and canosocitance.

That is, the propagation constant γ is a function of the frequency f (=-) and is 2π. Furthermore, considering that n21 Zc r Zr2 +γ is known, if the input impedance Zi to the coil 38 is measured for a plurality of frequencies f, the impedance up to the fault point 21 can be determined by the method described below. The distance L1 can be determined.

That is, for example, a representative t1+ -12+ Zr
A plurality of combinations of 1 are selected, and the frequency characteristics of the input impedance Zi for each case are calculated in advance. Next, compare the frequency characteristics of the measured input impedance with the frequency characteristics calculated in advance,
For example, by the method of least squares, a combination of t+ + A2 + zr1 (this is referred to as 111. t2', Zr11) that gives a frequency characteristic closest to the measured value is determined. Furthermore, L 1 ' r A2 ' + Z r1'
11. with a value close to . Select multiple combinations of A2 and Zrt, and use the least squares method from among them to find the combination of A1.12 and Zr+ that gives the frequency characteristic of the input impedance closest to the measured value (this is
゜122, Zr1). Hereinafter, by sequentially finding (/, +5.12', Zr13)- in this way, it is possible to gradually approach the true values L1.12 and Zr1.

Although the above description has been made for optical submarine cables, the present invention can also be used for conventional coaxial submarine cables. Moreover, the electronic circuit necessary for the measurement can be housed in the manned or unmanned underwater vehicle used when attaching the current transformer 11 to the optical submarine cable. The measurement results can also be transmitted to the mother ship via a signal transmission device between the submersible and the mother ship (for example, a TED cable connecting the mother ship and the submersible).

(Effects of the Invention) As described above, according to the present invention, it is possible to know the length of the cable to the point of failure without cutting the optical submarine cable, thereby reducing the time required to repair the failure of the optical submarine cable.
It becomes possible to reduce expenses.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an example of an optical submarine cable, FIG. 2 and FIG. 3 show an embodiment of the present invention, and FIG. Shows the circuit. DESCRIPTION OF SYMBOLS 11... Current transformer, 12... Wave transmitting coil, 13... Wave receiving coil, 14a, 14b... Optical submarine cable, 21... Fault point.

Claims (4)

[Claims] (1) By setting a closed ring-shaped magnetic body that can be divided and equipped with a coil so that the optical submarine cable passes through the probe made of the magnetic body, the magnetic body and the optical submarine cable are connected. A current transformer is formed between the current transformer, a signal current is passed through the conductor in the optical submarine cable through the current transformer, the signal current component reflected from the fault point is extracted, and the signal current component is extracted from the current transformer and the above-mentioned signal current component. A fault point detection method for optical submarine cables that is characterized by measuring the length of the cable between the fault point and the fault point. (2) The signal current is a pulsed current, and the time required for the pulsed current to travel back and forth between the current transformer and the fault point is measured, and from this time the time required for the pulsed current to travel back and forth between the current transformer and the fault point is measured. 2. A method for detecting a fault point in an optical submarine cable according to claim 1, characterized in that the cable length is measured. (3) The signal current is a pseudo-random signal, the correlation function between the pseudo-random signal and the pseudo-random signal component reflected from the fault point is determined, and the current transformer and the fault are determined from the delay time that gives the maximum correlation function. 2. A method for detecting a fault point in an optical submarine cable according to claim 1, characterized in that the cable length between the points is determined. (4) By setting a ring-shaped magnetic body that can be divided and equipped with a coil so that the optical submarine cable passes through the center of the magnetic body, a current is generated between the magnetic body and the optical submarine cable. forming a transformer, passing a sinusoidal current through the coil of the current transformer, measuring the input impedance of the coil from the relationship between the current flowing through the coil and the voltage, and changing the frequency of the sinusoidal current; 2. The optical submarine cable failure point detection method according to claim 1, wherein the cable length between the current transformer and the failure point is determined from the relationship between the current transformer and the input impedance.