JPH07162838A - Catv system with fault restoration function - Google Patents

Abstract

PURPOSE:To speedily restore a line so as not to propagate the effect of the fault over a wide range at the time of line fault by providing a linkage point between branching transmission lines, controlling the flow of a signal at this linkage point and switching the transmission direction of a relay amplifier or the like. CONSTITUTION:When the accident of disconnection is generated at a part shown by F1 in a transmission line 3, no signal is transmitted to relay amplifiers 44-47 and 49, distribution relay amplifier 52 and relay amplifier 61 for branching line. A pilot signal usually transmitted from a head end 1 is not transmitted to these equipments. Since the pilot signal of a transmission line 7 is not detected on a pilot signal detection circuit 19 even at a repeater 8 for linkage, the repeater 8 for linkage detects pilot abnormality. The repeater 8 answers state contents including the pilot abnormality on the side of the transmission line 7 to a master station 10. The master station 10 detects the generation of fault on the transmission line 7. The master station 10 judges the block of fault generation and the form of that fault and automatically starts fault restoration control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CATV system in which a transmission path is formed in a dendritic manner, and in particular, in the case of a line failure, the CATV system can be quickly restored so that the effect of the failure does not reach a wide range. It is about.

[0002]

2. Description of the Related Art A conventional CATV system will be described with reference to FIG. As shown in FIG. 5, information (signal)
The head end 1 which is a sending end of the device and an information collecting end of each device on the transmission path, and the terminal device 9 are connected via a dendritic transmission path formed by a coaxial cable. Here, a relay amplifier 60 for compensating the signal attenuation characteristic of the coaxial cable is inserted in the transmission line at an appropriate interval.
The network configuration will be described in detail for the main line system and the branch line system. In the main line system, main line transmission lines (main lines) are radially laid, and the relay amplifiers 60 are cascade-connected on the main line. . In the branch line system, the branch wiring is branched from the relay amplifier 60 installed on the main line, and the branch line relay amplifier 6 is further provided.
The distribution wiring is branched by 1 and installed up to the terminal device 9 by the tap-off 62.

As a signal transmission system, a frequency division multiplexing system (FDM) is mainly adopted, and further, a transmission band is divided into two, and each is allocated as a downstream signal transmission band and an upstream signal transmission band and both are allocated. Data transmission is possible. Here, a high frequency band is assigned as the downlink signal transmission band, and a low frequency band is assigned as the uplink signal transmission band.

In order to monitor the status of the transmission path and the inside of the equipment, each relay amplifier 60 may be equipped with a status detection unit and a function of sending the detected status to the center apparatus by a signal. In this case, the center device includes each relay amplifier 60.
Detected from the content of the status signal sent from
Notify the driver by buzzer etc. The driver presumes the cause of the abnormality from the notified abnormality and performs recovery work on site according to this cause.

Here, the structure of the relay amplifier will be described with reference to FIG.

The filter unit 71 separates a transmission signal into an upstream signal and a downstream signal, and receives the input / output of the amplifier 72.
It is provided in the output section. The upstream signal and the downstream signal separated by the filter unit 71 are respectively amplified by different amplifiers 72. In this way, the amplifiers 72 that amplify the signals are independent for the upstream signal and the downstream signal. Therefore, the transmission directions of the upstream signal and the downstream signal in the relay amplifier 60 are uniquely determined by the installation direction of the device.

[0007]

In the CATV system described above, a dendritic network is formed in which a large number of relay amplifiers are connected for compensating the transmission loss of the transmission path of the coaxial cable. This has the following drawbacks.

A line failure may occur in the transmission line due to a disconnection or short circuit accident, a failure of a relay amplifier, or the like. When a line failure occurs, no signal is transmitted to the transmission path beyond the location where the failure occurs as seen from the headend. Since the transmission line is formed in a dendritic form, a single line failure has a great influence on the system. The closer the location of the failure is to the head end, the greater the effect, and the problem is that the area in which the failure occurs becomes wider.

Further, since it takes a long time to restore a faulty part such as a coaxial cable, a relay amplifier or parts thereof by replacing the faulty part, it is necessary to recover from the faulty part even after finding the faulty part. The outage continues. Therefore, when a line failure occurs, there is a problem that the communication is interrupted over a wide area and it takes a long time to recover.

Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a CATV system which can quickly recover from the influence of the failure when the line fails.

[0011]

In order to achieve the above object, the present invention is to connect relay amplifiers in cascade to a trunk line, connect a distribution relay amplifier in the middle of the trunk line, and connect a distribution line to the distribution relay amplifier. The main line is then distributed, and this distribution line and the distribution lines from other trunk lines are connected by a linking repeater, and when there is no failure in the transmission line and the equipment on the transmission line, this distribution line is used to divide each distribution line. When a failure occurs in the transmission line or a device on the transmission line, the bifurcating wiring is connected by this coordinating repeater so that one trunk line and the other trunk line are linked, and it is close to the above-mentioned linking repeater. The transmission direction of the relay amplifier and the distribution relay amplifier is sequentially switched from the side to the fault location, and the transmission signal is detoured and relayed from the trunk line without fault to the fault location via the linking relay to restore the transmission path.

A master station may be connected to the headend, and the failure recovery operation may be performed by remote control of each device on the transmission path by data transmission from the master station.

In the remote operation of the failure recovery operation, each device on the transmission path detects a pilot signal or another specific frequency sent from the headend, and the master station obtains the detection result and determines the device Data transmission may be performed, and the master station may detect the occurrence of a failure from the presence or absence of a response from each device and the detection result obtained from the response.

Before performing the failure recovery operation, the transmission path may be separated by first terminating the output terminal of the device on the master station side at the failure point, and then the failure recovery operation may be performed.

The distribution repeater amplifier has three terminals for connecting to a transmission line, and these three terminals serve as input terminals and can be switched to one input and two outputs, and two outputs are provided. The output level of the terminal may be the trunk output level.

The relay amplifier may have a configuration capable of switching between input and output.

The link repeater may have a switch mechanism for switching between connection and disconnection of the transmission line based on a control command from the master station.

The link repeater may have an amplification function similar to that of the repeater amplifier, and may have pseudo line circuits on both transmission line sides.

[0019]

The gist of the present invention is to provide a linking point between the dendritic transmission lines and control the flow of signals at this linking point, and to switch the transmission direction of the relay amplifier or the like for normal transmission. By linking the signal from the path to the sound transmission path ahead of the failure occurrence point, it is possible to avoid or minimize the failure.

That is, according to the above configuration, when a failure occurs in the transmission line or a device on the transmission line, the distribution lines are connected from the one trunk line to the other trunk line by connecting the distribution lines with the linking repeater. The transmission direction of the repeater amplifier and the distribution repeater amplifier in the section in which the trouble is spread is switched. As a result, a transmission line from the trunk line without faults to the fault spread section is formed via the link repeater. Since the transmission signal from the headend is relayed by way of a trunk line without fault, restoration of the section where the fault has spread is achieved.

As a result, the reliability of the system is greatly improved and the recovery time is shortened.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a configuration example of a CATV system for implementing the present invention. This CATV system includes a master station 10, a headend 1, transmission lines 2, 3, 6, and 7,
Relay amplifiers 40 to 49 and distribution relay amplifiers 51 and 52
And a repeater 8 for cooperation and a terminal device 9.

The master station 10 is connected to the headend 1,
Transmission lines 2 and 3 which are main lines are laid radially from the head end 1. On the transmission line 2, a relay amplifier 40-
43 are connected in cascade. A distribution relay amplifier 51 is connected in the middle of the transmission line 2, and the transmission line 6 is distributed from this distribution relay amplifier 51. Repeater amplifier 4 also on transmission line 6
8 is connected, and the end of the transmission line 6 is connected to the linking repeater 8. On the other hand, the relay amplifiers 44 to
47 are connected in cascade. A distribution relay amplifier 52 is connected in the middle of the transmission line 3, and the transmission line 7 is distributed from this distribution relay amplifier 52. Repeater amplifier 4 also on transmission line 7
9 is connected, and the end of the transmission line 7 is connected to the linking repeater 8. A branch line is drawn from the relay amplifier 45,
A branch line relay amplifier 61 is connected to this branch line, and a tap-off 62 is further provided at the end of the branch line amplifier 61, and the terminal device 9 is connected to the tap-off 62.

Here, since it is necessary to stabilize the signal level of the transmission line to a constant value for the normal operation of the CATV system, the reference level to the automatic gain control circuit built in each of the relay amplifiers 40-49. A pilot signal is sent from the head end 1 side to the high frequency side of the transmission signal band so that a signal can be given. Each auto gain control circuit is controlled by this pilot signal. Although there is a method of substituting the carrier wave of the television signal depending on the system, the pilot signal is generally used. This pilot signal is constantly transmitted.

The master station 10 transmits various commands to devices on the transmission path, such as the relay amplifiers 40 to 49, the distribution relay amplifiers 51 and 52, and the link relay 8 and receives responses from the devices. is there. The master station 10 can determine a failure occurrence, a failure spread section, and the like based on the response from each device, and can determine a bypass relay of the transmission path. Communication between the master station 10 and each device is performed by frequency division multiplexing (FDM) using transmission lines 2, 3, 6, and 7.

The linking repeater 8 separates the transmission path 6 and the transmission path 7 when the CATV system is operating normally, and when the failure occurs in the transmission path 2 or 3, the transmission path 6 is separated. 6 has a function of linking the transmission path 7 with each other, and has a function of performing amplification when the linking is performed. It also has a function of receiving a downstream signal in the high frequency band input from the transmission path 6 and the transmission path 7 and transmitting an upstream signal in the low frequency band.

As shown in FIG. 2, the linking repeater 8
Has two terminals a and b, and these terminals a and b are connected to the transmission lines 6 and 7, respectively. Power separation filter (hereinafter referred to as PSF) 12 connected to terminals a and b
Separates the power frequency component superimposed on the signal transmitted by the transmission lines 6 and 7,
The electric power is supplied to 3. The power supply unit 13
Electric power is supplied to each element that constitutes each part of the linking repeater 8. A plurality of directional couplers 15 are provided between the two PSFs 12, two switches 14, and an amplification circuit 16 and a terminating resistor 17 sandwiched between the switches 14 for loss compensation.
And are provided. Both switches 14 can connect (separate and connect) the transmission lines, connect the terminating resistor 17 and switch the transmission direction.

Modem 18 connected to directional coupler 15
Has a function of receiving a downlink band signal and transmitting an uplink band signal. This modem 18 has a microcomputer 1
1 is connected, and the microcomputer 11 performs data transmission using the modem 18. The microcomputer 11 reads the data of the downlink band signal from the master station 10 via the modem 18, and follows the instruction of the data content if the destination of the data matches its own address. For example, if it is a state content transmission command, the modem 18 sends a signal indicating the pilot level, the internal state of the device, etc.
The signal is transmitted using the upstream band, and if it is a control command, control is performed according to the content thereof, and then a signal indicating the device state is transmitted. If the transmission line is normal here, both modems 1
Although the data from the master station 10 is received from No. 8, only one modem 18 is used to reply. When the line fails, one modem 18 receives the data from the master station 10. Therefore, the received modem 18 is used to reply.

The two pilot signal detection circuits 19 connected to the directional coupler 15 detect the levels of the pilot signals superimposed on the signals transmitted by the transmission lines 6 and 7, respectively. When the pilot signals on the transmission lines 6 and 7 disappear or become smaller than a preset value, the output of the pilot signal detection circuit 19 allows the microcomputer 11 to recognize this.

The relay amplifiers 40 to 49 shown in FIG. 1 have a function of inverting the signal transmission direction by switching the signal input / output terminals, and when the failure occurs, the relay amplifiers 40 to 49 transmit the signals based on the control signal transmitted from the master station 10. It has a function of performing a direction inversion operation. An example of the configuration is shown in FIG.

As shown in FIG. 3, the relay amplifier 40
(All 40 to 49 are the same) has two terminals c and d, and these terminals c and d are respectively connected to the transmission line. Each PSF 12 connected to the terminals c and d separates the power frequency component superimposed on the signal transmitted through the transmission line and supplies power to each element via the power supply unit 13. A pseudo line circuit 20, two directional couplers 15 sandwiched between the two switches 14, and a loss compensating amplifier circuit 16 sandwiched between the directional couplers 15 are provided between the PSFs 12. The pseudo line circuit 20 is an attenuator for correcting a surplus of the gain of the relay amplifier 40 by quasi-realizing the loss in the coaxial cable by a circuit network.

Modem 18 connected to directional coupler 15
Has a function of receiving in the downlink band and a function of transmitting in the uplink band. These modems 18 are connected to the transmission line in a configuration in which the signals from the directional couplers 15 provided on both transmission line sides are combined by a two-way divider 21 (or a directional coupler). It is installed so that it can receive a data signal from a transmission line and can transmit a data signal to both transmission lines. The microcomputer 11 is connected to the modem 18, and the microcomputer 11 reads the data from the master station 10 through the modem 18 and follows the data content if the destination of the data matches its own address. For example, if it is a state content transmission command, signals such as the pilot level and device internal state are transmitted to the master station 10 by the modem 18 using the upstream band, and if it is a transmission direction reversal command, the switch 14 is controlled. To reverse the transmission direction. Here, as shown in FIG.
Alternatively, one modem may be installed on each of the transmission lines.

The distribution relay amplifiers 51 and 52 of FIG. 1 have a function of transmitting signals to the transmission lines 6 and 7 at the same signal level as the transmission lines 2 and 3, and based on the control signal transmitted when a failure occurs. , And has a function of switching the signal transmission direction by switching between the input terminal and the output terminal. An example of the configuration is shown in FIG.

As shown in FIG. 4, the distribution relay amplifier 5
1, 52 have three terminals e, f, g, and these terminals e, f, g are respectively connected to the transmission line. Terminal e,
The PSF 12 connected to f and g separates the power frequency component superimposed on the signal transmitted by each transmission line and supplies power to each element via the power supply unit 13. A directional coupler 15 and a switch 14 are connected to each PSF 12, and an amplifier circuit 16 for loss compensation is provided between the switches 14. By changing the connection state of each switch 14, the terminal e,
The connection relationship between f and g and the amplifier circuit 16 is configured to change in any combination in the form of one input and two outputs.

Modem 18 connected to directional coupler 15
Has a function of receiving a downlink band and a function of transmitting an uplink band. The modem 18 is a directional coupler 15 installed on the side of three transmission lines.
Is connected to the transmission line in a configuration that multiplexes the signals from the three dividers 22 and is installed so that the data signals from all the transmission lines and the data signals to all the transmission lines can be received. There is.

The microcomputer 11 is connected to the modem 18, and the microcomputer 11 uses the modem 18 to perform data transmission. The microcomputer 11 receives a command having an address addressed to itself from the master station 10, controls the switching of the switch 14 according to the command, and sends a signal of the control result and the status content to the master station 1.
Send to 0.

Here, as shown in FIG.
Although 2 may be used as one modem, one modem may be installed in each transmission line.

The operation when a failure occurs will be described below. Here, a case where a disconnection accident occurs in the portion indicated by F1 of the transmission line 3 in FIG. 1 will be described.

If a disconnection accident occurs in F1, F
Equipment installed after 1 (relay amplifiers 44, 45, 4
No signals are transmitted to 6, 47, 49, the distribution relay amplifier 52, and the branch relay amplifier 61). Head end 1
The pilot signal that is constantly transmitted is also not transmitted to these devices. Since the pilot signal on the transmission path 7 is not detected by the pilot signal detection circuit 19 even in the link relay 8, the link relay 8 detects a pilot abnormality. Here, the master station 10 sequentially polls all trunk line devices for monitoring in order to monitor the state of the transmission path. The link repeater 8 receives the status content transmission command from the master station 10 transmitted through the transmission paths 2 and 6 which is a healthy section, and transmits the status content including the pilot abnormality on the transmission path 7 side by the received modem. Respond to the master station 10 via paths 6 and 2. The master station 10 receives the response result from the link repeater 8 and the relay amplifiers 44, 4 and 4.
5, 46, 47, 49 and the non-response of the distribution relay amplifier 52 detect that a failure has occurred on the transmission path. The master station 10 determines the fault occurrence section and the fault form, and automatically starts the fault recovery control. Alternatively, the operation is performed so that the driver is notified of the occurrence of the failure, the driver determines the failure status, individually controls the transmission path devices, and recovers the failure. That is, the processing unit of the master station 10 may perform automatic recovery, or the driver may perform manual recovery through the man-machine interface based on the information detected by the master station 10.

When a disconnection accident occurs in F1, the response results of each device received by the master station 10 are relay amplifiers 44, 45, 46, 47, 49 and a distribution relay amplifier 52.
As a result, there is no response and there is a pilot error on the transmission line 7 side from the linking repeater 8, and disconnection at F1 can be determined.

The master station 10 which has judged the disconnection at F1 performs the link operation of the signals. That is, the master station 10 first transmits a control command including a transmission direction command and a line link command to the link repeater 8 via the transmission path 2 using the downlink band. In accordance with the content of this control command, the link repeater 8 connects the lines with the transmission direction of the downlink signal from the transmission line 6 to the transmission line 7 (the transmission direction of the upstream signal is opposite). As a result, the downlink signal of the master station 10 sent from the transmission path 7 reaches the relay amplifier 49. Then, the relay amplifier 49 can receive the downlink signal of the master station 10 by the modem 18.

The master station 10 knows from the control response of the above-mentioned linking repeater 8 that the linking repeater 8 has normally performed the connection operation of the transmission path. Therefore, an inversion command in the signal transmission direction is sent to the relay amplifier 49. The relay amplifier 49 is
The transmission direction is reversed according to this command, and a control response indicating this is transmitted to the master station 10.

The master station 10 knows from the control response of the relay amplifier 49 that the relay amplifier 49 has performed the inverting operation and that the connection relay 8 and the relay amplifier 49 are not disconnected. With such a procedure, the master station 10 sequentially
The inversion of the signal transmission directions of the distribution relay amplifier 52 and the relay amplifiers 46, 45, 44 is instructed. At the same time, master station 10
Confirm that the transmission line is not broken.

As a result of the above, signals from the linking repeater 8 to the relay amplifier 44 are transmitted in the opposite direction from before, and signals in the downlink band from the master station 10 and the headend 1 are transmitted. The signal is transmitted to the relay amplifier 44 via the detours of the paths 2, 6, 7, and 3, and the restoration is achieved.

The recovery in the case of the disconnection at F1 has been described above. For example, if there is a disconnection between the relay amplifiers 44 and 45, the relay amplifier 44 is first determined after determining the disconnection point. The output of is disconnected. That is, the termination control of the relay amplifier 44 is performed, and after the transmission path is completely disconnected, the restoration control is performed. this is,
This is to prevent the signals from the master station 10 from colliding with each other when the disconnection is not complete.

[0047]

The present invention exhibits the following excellent effects. (1) Since a signal link operation can be performed even when a failure occurs, it is possible to recover in a section where a signal could not be transmitted conventionally, and the reliability of the entire system is improved. Even if there is an obstacle, the spillover area will be greatly reduced. Especially 1
In case of disconnection, etc., the entire system can be restored. (2) Since it is possible to recover only by remote control, the time affected by the failure is the time required for remote control to recover, which is significantly shorter than the time required for conventional on-site recovery work. It is possible to speed up.

[Brief description of drawings]

FIG. 1 is a block diagram of a CATV system showing an embodiment of the present invention.

FIG. 2 is an internal configuration diagram of the linking repeater of the present invention.

FIG. 3 is an internal configuration diagram of a relay amplifier of the present invention.

FIG. 4 is an internal configuration diagram of a distribution relay amplifier of the present invention.

FIG. 5 is a block diagram of a conventional CATV system.

FIG. 6 is an internal configuration diagram of a conventional relay amplifier.

[Explanation of symbols]

 1 Headend 2, 3, 6, 7 Transmission Line (Main Line, Distribution Line) 8 Link Repeater 10 Master Station 40-49 Repeater Amplifier 51, 52 Distribution Repeater Amplifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Sato 5-1-1 Hidaka-cho, Hitachi City, Hitachi, Ibaraki Prefecture Power Systems Laboratory, Hitachi Cable, Ltd. (72) Kenichi Murakami 5 Hidaka-cho, Hitachi City, Ibaraki Prefecture 1-1-1, Hitachi Cable Co., Ltd. Power System Laboratory (72) Inventor Kenichiro Soma 5-1-1, Hidakacho, Hitachi City, Ibaraki Hitachi Cable Company, Power System Laboratory

Claims (8)

[Claims] 1. In a CATV system in which main line transmission lines are laid radially from a headend, and branch lines are formed in these main lines to form a transmission line in a tree-like form, a relay amplifier is cascade-connected to the main line, and a midway of the main line. The distribution relay amplifier is connected to the distribution relay amplifier and the distribution line is connected to the distribution line to distribute the trunk line, and the distribution line and the distribution line from another trunk line are connected to each other by the linking repeater, and the transmission line and the transmission line are connected. When there is no fault in the equipment of, the separation wiring is used to separate each distribution line, and when a failure occurs in the transmission line or equipment on the transmission line, both distribution lines are connected using this connection repeater. The trunk line and the other trunk line are linked to each other, and the transmission directions of the relay amplifier and the distribution relay amplifier are sequentially switched from the side closer to the link repeater to the failure point, and the faulty trunk line is switched to the failed point via the link repeater. C with a fault recovery function, which is characterized in that the transmission signal is detoured to the location to restore the transmission path
ATV system. 2. The fault according to claim 1, wherein a master station is connected to the headend, and the failure recovery operation is performed by remotely operating each device on the transmission path by data transmission from the master station. CATV system with recovery function. 3. In the remote operation of the failure recovery operation, each device on the transmission line detects a pilot signal or another specific frequency transmitted from the headend, and the master station obtains the detection result to obtain each detection result. 3. The fault recovery function according to claim 2, wherein data transmission with a device is performed, and the master station detects occurrence of a fault from the presence or absence of a response from each device and a detection result obtained from the response. CATV system with. 4. The failure recovery operation is performed before the failure recovery operation is performed by first disconnecting the transmission line by terminating the output terminal of the master station side device at the failure point. C with a failure recovery function according to any of items 2 to 3
ATV system. 5. The distribution relay amplifier has three terminals for connecting to a transmission line, and any of these three terminals can be switched to be an input terminal or one input and two outputs. The output level of the two output terminals is a trunk line output level.
4. A CATV system with a failure recovery function according to any one of 4. 6. The relay amplifier has a configuration capable of switching between input and output.
A CATV system with a failure recovery function according to any one of the above. 7. The linking repeater has a switch mechanism for switching between connection and disconnection of a transmission line based on a control command from the master station.
A CATV system with a failure recovery function according to any one of the above. 8. The CATV with a fault recovery function according to claim 1, wherein the linkage repeater has an amplification function similar to that of the relay amplifier and has pseudo line circuits on both transmission path sides. system.