JPH10107742A - Digital transmission network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the transmission network even on the occurrence of a fault in the transmission network and to easily locate a fault position by sending a loopback control signal from a center equipment to all terminal equipments so as to bring all the terminal equipments to a reception state from an optical fiber cable being a standby line. SOLUTION: On the occurrence of a fault such as a broken optical fiber cable between terminal equipments 7N-1 and 7N, a faulty optoelectric converter at the input of the terminal equipment 7N, or a faulty electrooptic converter at the output of the terminal equipment 7N-1, all terminal equipments after the faulty terminal equipment are automatically brought into the reception state from a standby loop using an optical fiber cable 9. Then the terminal equipment close to the center equipment 6 is sequentially restored to the normal operation by a command from the center equipment 6. However, in the case of a broken optical fiber cable between the terminal equipments 7N-1 and 7N, it is confirmed that up to the terminal equipment 7N is sound because a fault is caused when the terminal equipment 7N-1 is restored to the normal operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a monitoring center device installed at one or a plurality of monitoring centers installed at a plurality of monitoring points distributed over a wide area. Video of the surveillance point,
The present invention relates to a digital transmission network that transmits a video signal, an audio signal, and the like in order to monitor by audio and the like.

[0002]

2. Description of the Related Art A conventional digital transmission network is
This will be described with reference to FIG. In FIG. 8, reference numeral 82 denotes a plurality of terminal devices provided with monitoring devices such as a television camera and a microphone for monitoring at a plurality of monitoring points distributed over a wide range, and 81 denotes a video monitor, an audio device, and the like. A center device for monitoring video, audio, and the like transmitted from a plurality of terminal devices 82;
Reference numerals 3 and 84 denote signal transmission cables for connecting between the center device 81 and the terminal device 82 and between the terminal devices 82, for example, optical fiber cables. As shown in FIG. 8, in the transmission network, in order to increase the reliability of the transmission network, the transmission network is formed into a double loop to improve availability. Availability can be increased to 96% by double looping, even if it is 80% alone.

In a digital transmission network, a center device 81 is divided into frame units, has a frame synchronization signal and the like, uses a reference data signal of a predetermined format in which data can be inserted and extracted as an optical signal, and uses an optical fiber cable 83 ( Or optical fiber cable 8
4), a plurality of terminal devices 82 (82-1, 82-
2, 82-3, 82-4...). Each terminal device 82 is provided with a monitoring device such as a television camera and a microphone. The terminal device 82 is provided at a predetermined position of the transmitted data signal of a predetermined format with a video signal obtained by capturing an image of a monitoring point with a television camera or with a microphone. The data signal of the predetermined format into which the data such as the audio signal or the like is inserted or the transmitted data is extracted, and the data such as the video signal or the audio signal is further inserted using the optical fiber cable 83, The data is transmitted to the next terminal device 82. An optical signal from the last terminal device 82 is input to the center device 81 using the optical fiber cable 83,
Data such as a required video signal and audio signal of each terminal device is extracted from the data signal of the predetermined format. The data of the extracted video signal and audio signal is monitored by a video monitor and an audio device.

Here, for example, an optical fiber cable 83
However, if a disconnection occurs between any of the terminal devices 82, no optical signal is transmitted to the next terminal device 82, data cannot be transmitted, and monitoring by the center device 81 becomes impossible. In this case, by continuing data transmission using the optical fiber cable 84 provided as a standby system, monitoring in the center device 81 becomes possible. As described above, in the conventional digital transmission network, the working optical fiber cable 83 and the standby optical fiber cable 84 are provided to form a double loop, thereby preventing the system from going down.

[0005]

In a digital transmission network according to the prior art, an optical fiber cable having a double loop between any one of a plurality of terminals installed in a wide range is used. There is a problem that the digital transmission network becomes unable to transmit a data signal when a disconnection occurs or when any terminal device breaks down. The present invention solves the above-mentioned problems, and can easily maintain a transmission network and specify a location of a failure when a transmission network connected in a loop by an optical fiber cable fails, using a complicated control circuit and advanced software. It is an object of the present invention to provide an inexpensive digital transmission network that does not require sophisticated control and has improved system reliability, availability, and maintainability.

[0006]

In order to achieve the above object, a digital transmission network according to the present invention comprises at least one center device and a plurality of terminal devices which are duplexed by working and protection line optical fiber cables. In a digital transmission network connected to a loop and transmitting a digital data signal such as a video signal and an audio signal as an optical signal, a loopback control signal is transmitted from the center device to all the terminal devices, and all the terminal devices are transmitted. The apparatus is set in an input state from the optical fiber cable of the backup line.

In the digital transmission network of the present invention, a loopback control signal is transmitted from the center device to all the terminal devices, and all the terminal devices are brought into an input state from a protection line optical fiber cable. Next, from the center device, sequentially, from the terminal device near the center device, transmit a control signal for returning to an input state of a working line, and the terminal device near the center device operates normally. Is to check.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a digital transmission network according to the present invention will be described. FIG. 1 is a block diagram of a terminal device used in a digital transmission network according to the present invention. In FIG. 1, reference numeral 1 denotes an optical-electrical converter that receives an optical signal transmitted through an optical fiber cable and converts the optical signal into an electric signal (data signal) (has two working and standby systems). Reference numeral 4 denotes an electric-optical converter for converting an electric signal (data signal) to be transmitted to another device through an optical fiber cable into an optical signal (having two systems, a working system and a standby system). A path switching unit for switching the path of the data signal received and converted by the optical-to-electrical converter 1 and for switching the path of the data signal to be converted and transmitted by the electrical-to-optical converter 4. A multiplexing unit that inserts data from a monitoring device (not shown) such as a television camera and a microphone into the data signal received and converted by the multiplexing unit and extracts data from the data signal.
Are the control by the command from the center device, the optical input level detection signal from the optical-electrical converter 1, and the electrical-optical converter 4.
1 shows a path control circuit for controlling the path switching unit 2 based on an optical output level detection signal from the multiplexing unit 3 and an error detection signal of an input data signal from the multiplexing unit 3.

In the terminal device, an optical signal transmitted by an optical fiber cable is received by the optical-electrical converter 1, converted into a data signal by the optical-electrical converter 1, and output to the path switching unit 2. You. The path switching unit 2 outputs the data signal input from the optical-electrical converter 1 to the multiplexing unit 3, and switches the path of the data signal according to the control signal. The multiplexing unit 3 includes a data signal (for example, a plurality of frames) input from the path switching unit 2, and each frame includes frame synchronization, network control data, video data and audio data divided into a plurality of channels, and terminal data. At a predetermined data position, video data and audio data from a monitoring device (not shown) such as a television camera and a microphone, and other data such as data by a computer are inserted. , Extract required data, insert data,
The extracted data signal is output to the path switching unit 2. The path switching unit 2 outputs the data signal input from the multiplexing unit 3 to the electro-optical converter 4. Electric-optical converter 4
Converts the data signal input from the path switching unit 2 into an optical signal, transmits the optical signal to an optical fiber cable, and transmits the optical signal to another terminal device.

The path control circuit 5 receives a control signal or a detection signal from the optical-to-electrical converter 1, the electric-to-optical converter 4, and the multiplexing unit 3, and switches the path according to the control signal or the detection signal. The control of the section 2 is performed. A signal input from the optical-electrical converter 1 to the path control circuit 5 is a control signal of a loopback command from a center device (not shown, described later) in the transmission network and an input of an optical signal in the optical-electrical converter 1. A signal which is a level detection signal and which is input from the electro-optical converter 4 to the path control circuit 5 is an output level detection signal of an optical signal in the electro-optical converter 4 and is transmitted from the multiplexing unit 3 to the path control circuit 5. The input signal is an error detection signal of the data signal input to the multiplexing unit 3. The path control circuit 5 controls the path switching unit 2 according to the control signal of the loopback command, and also controls the path switching unit according to the input level detection signal of the optical signal, the output level detection signal of the optical signal, and the error detection signal of the data signal. 2 is performed. The power supply (not shown) of the terminal device includes a backup power supply device, and power is normally supplied from the power supply device to all circuits. Power is supplied from the backup power supply to the converter 1, the path switching unit 2, and the electro-optical converter 4, so that a minimum digital transmission network can be maintained.

FIG. 2 is a block diagram of a digital transmission network according to the present invention in which a plurality of terminal devices shown in FIG. 1 are arranged. In FIG. 2, reference numeral 7 denotes a plurality of terminal devices including monitoring devices such as a television camera and a microphone for monitoring at a plurality of monitoring points distributed over a wide range, and 6 denotes
Equipped with a monitoring device consisting of a video monitor, audio device, etc.
A center device that monitors video, audio, and the like transmitted from the plurality of terminal devices 7 and controls the terminal devices 7;
Reference numerals 8 and 9 denote optical fiber cables for transmitting optical signals connected between the center device 6 and the terminal device 7 and between the terminal devices 7. The transmission loop connected by the optical fiber cable 8 forms a working loop, and the transmission loop connected by the optical fiber cable 9 forms a backup loop.

In a digital transmission network, a center device 6 provided with a monitoring device composed of a video monitor, an audio device and the like is divided into frames, has a frame synchronization signal and the like, and has a predetermined format in which data can be inserted and extracted. , And converts the data signal into an optical signal.
Transmit to N-2. The terminal device 7N-2 is provided with a monitoring device such as a television camera and a microphone, and a video signal obtained by imaging the monitoring point at a predetermined position of the data signal of a predetermined format transmitted from the center device 6 with the television camera. Or, a sound signal or the like collected by a microphone is inserted, or data is extracted, and a data signal of a predetermined format into which a video signal, a sound signal, and the like are inserted is further converted to the next signal using the optical fiber cable 8. The data is transmitted to the terminal device 7N-1. The plurality of terminal devices 7 (N-
1, N, N + 1, N + 2...) Are terminal devices 7N-2.
In the same manner as described above, a video signal, an audio signal, and the like are inserted into the data signal, extracted, and the data signal is transmitted to the next terminal device. An optical signal from the terminal device 7 at the end of the transmission network is input to the center device 6 using an optical fiber cable 8, and necessary video signals and audio signals are extracted from a data signal of a predetermined format. Monitoring is performed by a monitor, an audio device, or the like.

When a failure occurs in the digital transmission network according to the present invention in which a plurality of terminal devices are arranged as shown in FIG. 2, what kind of failure handling operation is performed in the terminal device will be described. When a failure occurs, for example, disconnection of the optical fiber cable between the terminal devices 7N-1 and 7N, failure of an optical-electrical converter at the input of the terminal device 7N, or electrical output of the terminal device 7N-1. In the case of a failure of the optical converter, all the terminal devices after the failed terminal device automatically enter the input state from the spare loop using the optical fiber cable 9 (hereinafter, the operation of switching the input to the spare loop: described as an input loop). ), And then, in response to a command from the center device 6, the terminal devices near the center device 6 are sequentially returned to normal operation. However, if the optical fiber cable between the terminal device 7N-1 and the terminal device 7N is broken, the operation becomes abnormal when the terminal device 7N-1 is restored to normal, and the terminal device 7N must be a normal terminal device. Can be confirmed.

Then, the center device 6 then turns the output of the failed terminal device 7N-1 into a spare loop (hereinafter, the operation of switching the output to the spare loop: described as an output loop) by controlling the loopback command. Check switching and operation.
If the terminal device 7N-1 can operate normally, the disconnection of the optical fiber cable between the terminal device 7N-1 and the terminal device 7N can be confirmed, so that the loop shown in FIG. 3 is formed. Here, if the terminal device 7N-1 does not operate normally when the output loop is set, the electric-optical converter of the terminal device 7N-1 is out of order or the optical unit is out of power. Therefore, the terminal device 7N-2 is set as the output loop. . Therefore, the center device 6 specifies the terminal device 7N-1 as the failure position, and then sets the system loopback state, and forms a loop as shown in FIG. Next, in the case of a failure of the optical-to-electrical converter at the input of the terminal device 7N, an abnormality occurs during the operation of the input loop of the terminal device 7N, and the failure of the terminal device 7N can be specified. When the electric system of the terminal device 7N is out of order, the confirmation operation from the center device 6 is performed in the same manner as described above, but when the terminal device 7N + 1 is put into a normal loop by a command from the center device 6, the operation becomes abnormal. , The terminal device 7N or the terminal device 7N + 1 can be specified as a failure. When the terminal device 7N is set as an output loop under the control of the center device 6,
Since an operation abnormality occurs, the terminal device 7N can be specified as a failure. In this way, the fault location is specified, and the loop shown in FIG. 5 is formed.

FIG. 6 shows a specific circuit of the path switching unit 60 provided in the center device 6 for specifying the fault location by the operation corresponding to the fault and realizing a normal operation loop. FIG. 6 shows an optical-electrical converter 6 provided in the center device 6.
5, only the electro-optical converter 66 and the path switching unit 60 are shown. The loop at the time of normal operation is the current system optical-electrical converter 6.
The data signal converted and output at 5A is output to the path switching unit 6
The signal is input to the electric circuit 61 through the ac line of the 0 changeover switch 62. The output of the electric circuit 61 is converted into an optical signal by the working electrical-optical converter 66A and output to the working loop. When a failure occurs in the forward loop, it is determined that the data signal converted and input by the standby optical-to-electrical converter 65B passes through the c-a line of the changeover switch 64 and passes through the bc line of the changeover switch 62. Are input to the electric circuit 61. The output of the electric circuit 61 is converted into an optical signal by the working electrical-optical converter 66A and output to the working loop.

To confirm the failure of the rear loop, the data signal converted and output by the working optical-electrical converter 65A is input to the electric circuit 61 through the ac line of the changeover switch 62. The output of the electric circuit 61 passes through the ac line of the changeover switch 63, is converted into an optical signal by the standby electric-optical converter 66B, and is output to the standby loop. At the time of system loopback, the active system loop and the standby system loop are used.
5A, the converted data signal is input to the electric circuit 61 through the ac line of the changeover switch 62.
The output of the electric circuit 61 is converted into an optical signal by the working electrical-optical converter 66A and output to the working loop. Also,
The data signal converted from the standby loop and input by the standby optical-electrical converter 65B is c-b of the switch 64.
The signal passes through the line, and is output from the standby system electrical-optical converter 66B to the standby system loop via the line bc of the changeover switch 63.

Next, FIG. 7 shows a specific circuit of the path switching unit 2 provided in the terminal device 7 for realizing an operation corresponding to a failure. FIG. 7 shows the optical-electrical converter 1 provided in the terminal device 7,
Only the electro-optical converter 4 and the path switching unit 2 are shown. In the normal operation loop, the data signal converted and input by the working optical-to-electrical converter 1 </ b> A
The signal is input to the electric circuit 71 through the c line. The output of the electric circuit 71 passes through the bc line of the changeover switch 73, is converted into an optical signal by the working electrical-optical converter 4A, and is output to the working loop. During the operation of the input loop, the data signal converted and input by the standby optical-electrical converter 1B is
The electric signal is input to the electric circuit 71 via the bc line of the changeover switch 74 and the bc line of the changeover switch 72. The output of the electric circuit 71 is bc of the changeover switch 73.
The signal passes through the line, is converted into an optical signal by the working electrical-optical converter 4A, and is output to the working loop. During the output loop operation, the data signal converted and input by the working optical-electrical converter 1A is input to the electric circuit 71 through the ac line of the changeover switch 72. The output of the electric circuit 71 passes through the a-c line of the changeover switch 74, is converted into an optical signal by the standby electric-optical converter 4B, and is output to the standby loop. By using the center device and the terminal device having such a function, it is possible to specify a failure point of the digital transmission network and maintain a loop. Although the monitoring system has been described in the above embodiments, it goes without saying that the present invention can be used not only for a video signal transmission system but also for a data transmission system.

[0018]

According to the present invention, it is possible to easily maintain a transmission network and specify a location of a failure when a transmission network connected in a loop by an optical fiber cable fails, and to use a complicated control circuit and advanced software. It is possible to provide a digital transmission network that does not require such control, is inexpensive, and has improved system reliability, availability, and maintainability.

[Brief description of the drawings]

FIG. 1 is a block diagram of a terminal device used in a digital transmission network according to the present invention.

FIG. 2 is a block diagram of a digital transmission network according to the present invention.

FIG. 3 shows an operation loop 1 when a failure occurs in the digital transmission network according to the present invention.

FIG. 4 shows an operation loop 2 when a failure occurs in the digital transmission network according to the present invention.

FIG. 5 shows an operation loop 3 when a failure occurs in the digital transmission network according to the present invention.

FIG. 6 is an explanatory diagram of an operation of a path switching unit provided in the center device of the digital transmission network according to the present invention.

FIG. 7 is an explanatory diagram of an operation of a path switching unit provided in the terminal device of the digital transmission network according to the present invention.

FIG. 8 is a block diagram of a conventional digital transmission network.

[Explanation of symbols]

 1,65 optical-electrical converter, 2,60 path switching unit, 3 multiplexing unit, 4,66 electric-optical converter, 5 path control circuit, 6,81 center unit, 7,82 terminal unit, 8,9 , 83, 84 Optical fiber cable, 10, 18 Working optical-electrical converter, 62, 63, 64, 72, 73, 74 Changeover switch, 61, 71 Electric circuit.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/135 10/13 10/12

Claims (5)

[Claims] At least one center device and a plurality of terminal devices are connected to a double loop by optical fiber cables of a working line and a protection line, and digital data signals such as video signals and audio signals are transmitted as optical signals. In the digital transmission network, a loopback control signal is transmitted from the center device to all the terminal devices, and all the terminal devices are set in an input state from an optical fiber cable of a backup line. Transmission network. 2. At least one center device and a plurality of terminal devices are connected to a double loop by optical fiber cables of a working line and a protection line, and digital data signals such as video signals and audio signals are transmitted as optical signals. In the digital transmission network, a loopback control signal is transmitted from the center device to all of the terminal devices, and all of the terminal devices are set to an input state from an optical fiber cable of a backup line. From, sequentially, from the terminal device near the center device, transmit a control signal to return to the input state of the working line, to confirm the terminal device in normal operation from the terminal device near the center device Digital transmission network characterized. 3. A digital data signal such as a video signal and an audio signal is transmitted as an optical signal by connecting at least one center device and a plurality of terminal devices to a double loop with optical fiber cables of a working line and a protection line. In the digital transmission network, a loopback control signal is transmitted from the center device to all of the terminal devices, and all of the terminal devices are set to an input state from an optical fiber cable of a backup line. From the terminal device near the center device sequentially transmits a control signal for returning to the input state of the working line, and confirms the terminal device operating normally from the terminal device near the center device, If the operation of the terminal device is confirmed, the loop-back from the center device to the abnormally operating terminal device is performed. A control signal is transmitted to set the abnormally operating terminal device to an output state to the spare line optical fiber cable, and if normal operation is confirmed, disconnection of the optical fiber cable connected to the abnormally operating terminal device output A digital transmission network, characterized in that: 4. At least one center device and a plurality of terminal devices are connected to a double loop by optical fiber cables of a working line and a protection line, and digital data signals such as video signals and audio signals are transmitted as optical signals. In the digital transmission network, a loopback control signal is transmitted from the center device to all of the terminal devices, and all of the terminal devices are set in an input state from an optical fiber cable of a backup line. From the terminal device near the center device sequentially transmits a control signal for returning to the input state of the working line, and confirms the terminal device operating normally from the terminal device near the center device, If the operation of the terminal device is confirmed, the loop-back from the center device to the abnormally operating terminal device is performed. Transmitting a control signal, setting the terminal device having an abnormal operation to an output state to an optical fiber cable of a spare line, and confirming the abnormal operation as a failure of the terminal device having an abnormal operation when the abnormal operation is confirmed. Transmission network. 5. At least one center device and a plurality of terminal devices are connected to a double loop by optical fiber cables of a working line and a protection line, and digital data signals such as video signals and audio signals are transmitted as optical signals. In the digital transmission network, the terminal device comprises: two optical-to-electrical converters for converting optical signals received from the working line and protection line optical fiber cables into data signals; and converting the data signals into optical signals and working lines. And two electro-optical converters for transmitting to the optical fiber cable of the backup line, and a path for switching a data signal from the two optical-electric converters and a data signal from the two electro-optical converters by a control signal A switching unit, and inserting digital data such as a video signal and an audio signal into a data signal switched and input by the path switching unit, A multiplexing unit for extracting a Ijitarudeta, and a control signal from the center apparatus, the light - and the light signal level detection signal from the optical transducer, - electrical transducer and an electrical
A path control circuit for controlling the path switching section based on an error detection signal from the multiplexing section.