JPH0454738A - Receiving end switching transmission system - Google Patents

Abstract

PURPOSE:To send a same signal from each sending end by providing a means sending the same signal to plural transmission lines to a sender side, a means compensating a relative delay in the plural signals and a monitor means monitoring the transmission lines to a receiver side. CONSTITUTION:A signal received by reception sections 22, 32 are stored once in memories 24, 34. The stored signals are read synchronously with each other and fed to a changeover circuit 60. Suppose that the circuit 60 is set to select a signal sent from the sending end through a transmission line L1, and when a line fault that a signal interrupt takes place or a code error rate is deteriorated to be a prescribed value or over in the transmission line L1, a monitor circuit 23 detects it and its alarm signal is sent to a changeover control circuit 70. The circuit 70 receives the alarm signal to check the operating state of a transmission line L2 as to whether or not an alarm is raised from a monitor circuit 33. When no fault exists in the signal sent through the transmission line L2, a switching control signal is sent to the changeover circuit 60 to select the circuit 60 to the position of the transmission line L2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a large-capacity transmission system that is excellent in maintainability and can ensure high reliability.

The present invention transmits the same signal through multiple transmission paths including those with different routes, compensates for the relative delay of the signal on the receiving side, and monitors the state of the transmission path to switch and select the transmission signal. , which realizes a highly reliable transmission method.

[Conventional technology]

With the reduction in the cost of optical fibers and advances in optical transmission technology, it has become possible to economically provide a variety of sophisticated information services. The information being transmitted is diverse, and
The amount of information is also becoming much larger than with traditional telephone services. The transmission speed of the future B-ISDN, the backbone line for image leased line services, etc. is 600 Mb/s, 2.4
Speeds are steadily increasing to Gb/s or higher. Among these trends in information and communication, the reliability of communication is becoming socially important.

In order to ensure communication reliability, in conventional transmission systems, a backup system is prepared for one or N systems on the same route, or a backup circuit is prepared for the line.
, Redundant system configurations have been adopted to ensure communication by manually or automatically switching to a standby system when the current system fails or during maintenance operations.

[Problem to be solved by the invention]

However, when switching from the active system to the backup system, complicated processes such as notification of failure information from the receiving side to the transmitting side, checking the availability and normal function of the spare channel, switching operation, synchronization recovery operation, and switchback are necessary. I need. This has made maintenance of the redundant system complicated.

Furthermore, since there are many steps from failure to normal operation, it takes time and the amount of information that is lost during the process increases. Particularly in ultrahigh-speed transmission systems with transmission speeds as high as 10 Gb/s, even the slightest momentary interruption causes the loss of an extremely large amount of data.

On the other hand, in the case of a failure that cannot be handled by using the same transmission path, such as line disconnection, a method is used to ensure communication by disconnecting the cross-connect and searching for a free route for each information channel. If we assume that a line disconnection occurs in a large-capacity backbone line, the number of channels that must be switched would be enormous, and it would take an enormous amount of time just to find a free route. In some cases, it may become difficult to secure a vacant route, and furthermore, this failure may become a trigger and threaten the reliability of transmission lines on other routes.

The present invention improves the conventional redundant system described above.
The purpose of the present invention is to provide a highly reliable transmission system in which procedures such as system switching and route switching required in the event of a failure are simple, and the probability of system interruption is extremely low in principle.

[Means to solve the problem]

The present invention provides a transmission system comprising a transmitting side, a receiving side, and a plurality of optical fiber transmission lines including different routes connecting the transmitting side and the receiving side, wherein the transmitting side includes the plurality of transmission lines. the receiving side includes means for compensating for relative delays of the plurality of signals transmitted through the plurality of transmission paths, and monitoring means for monitoring the transmission paths; The present invention is characterized by comprising a switching means for selecting a signal from a normally operating transmission line based on the monitoring information from the monitoring means.

Further, it is preferable that the transmitting side includes means for weighting signals to be transmitted depending on their importance, and for transmitting signals with high importance to many transmission paths.

[Effect]

In the transmission system of the present invention, the same signal is transmitted from each transmission end through a plurality of optical fiber transmission lines, including those with different routes.

At each receiving end, the multiple signals that have passed through each transmission path are temporarily stored in a memory device to compensate for the relative delay between the signals, and the signals are sent from the monitoring circuit in synchronization with each other. Based on the information, the switching circuit selects the signal of the normally operating transmission line as the received information.

In the transmission system of the present invention, signals on each transmission path are monitored at the receiving end, and failures in the transmission path are detected at the receiving end, and transmission path selection is performed at the receiving end without exchanging information with the transmitting end. Ru. In principle, as long as multiple transmission lines do not fail at the same time, it is possible to immediately detect a failure as soon as it occurs.
This is equivalent to switching signals without interruption, the switching procedure is simple, and maintainability is good.

The redundant system in the conventional system is only a backup system.
Basically, the backup system is activated only after a failure occurs, and the switching procedure is performed after repeating information transmission between the transmitting end and the receiving end, so it is possible to avoid the need for a certain amount of time from the occurrence of a failure to recovery. do not have. There were also problems with maintainability, such as the need for complicated procedures for selecting backup routes, which could lead to serious failures that would have a social impact.However, the transmission system of the present invention solves these problems. ing.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing a transmission system according to a first embodiment of the present invention.

Reference numeral 10 indicates a cross-connect device on the transmitting side.

The code IL 12 indicates a transmitting section of the transmitting side terminal device. The transmitting units 11.12 of this terminal equipment are connected to the receiving end equipment 21.31 by transmission paths L+ and L2, respectively.
is coupled to the receiving section 22.32 of. This transmission path,
, L2 are large-capacity transmission lines, such as optical fiber transmission lines, and the transmission lines L+ and L2 lead to the receiving side via different routes.

In addition, in this embodiment, the terminal equipment is shown only in one direction between the transmitting end and the receiving end to simplify the explanation, but it is clear that bidirectional transmission is possible; Both side end station devices are constructed as multiplex/separate end station lids.

The signal outputs of the receiving sections 22.32 of the receiving side terminal equipment 21.31 are respectively input to the memories 24.34. This memory 24.34 is composed of elastic memory, and may be of any type. For example, semiconductor memory, analog memory consisting of delay lines such as fiber,
A combination of these may also be used. The memories 24 and 34 temporarily store signals, and store and absorb information on the delay time difference between signals transmitted on L2 and jitter or wander on the transmission path, and This allows them to be synchronized with each other so that they can be switched at a later stage.

These signals synchronized by Memo 'J24.34 are input to the switching circuit 60, which selects the signal of either transmission path and outputs it to the cross-connect device 80 on the receiving side. This switching circuit 60 has two
:1 switching device, which has the function of simultaneously switching demultiplexed multi-channel signals using a switching control signal.

Reference numerals 23 and 33 denote monitoring circuits provided in each terminal equipment 21 and 31, which detect abnormal conditions such as signal interruption in the transmission path, L2, and detect errors in received signals by means such as parity check. This monitoring information is output to the switching control circuit 70. The switching control circuit 70 connects the transmission line L from this monitoring circuit 23.33.
+, the switching operation is determined based on monitoring information such as L2 transmission quality and failure status, and a switching selection control signal indicating which transmission path to select a signal from is output to the switching circuit 60.

Next, the operation of this embodiment will be explained.

The signal from the cross-connect device IO is sent to the terminal device 1 at the same time.
1.12 is sent to the transmitting unit 12 and subjected to multiplexing processing adapted to the transmission path, such as time division multiplexing and frequency multiplexing, along with other signals, and then sent to the receiving end terminal equipment 21 via the transmission paths L+ and Lz. .31.

This transmission signal is transmitted to the receiving section 22.32 of the terminal device at the receiving end.
received by.

The signal received by the receiving section 22.32 is stored in the memory 24.34.
is temporarily accumulated. The signals stored in the memories 24 and 34 are read out in synchronization with each other and sent to the switching circuit 60.

Assume that the switching circuit 60 is set to select the signal transmitted from the transmitting end through the transmission path L1. In this state, if a line abnormality occurs in the transmission line L1 such as a signal disconnection or a deterioration of the code error rate to a predetermined value or more, the monitoring circuit 23 detects this and sends an alarm signal to the switching control circuit 70. Ru. Upon receiving this alarm signal, the switching control circuit 70 checks the operating state of the transmission line L2 to see if the monitoring circuit 33 has issued an alarm.

If there is no abnormality in the signal transmitted through the transmission line L2, a switching control signal is sent to the switching circuit 60 to control switching to the transmission line L2 side.

On the other hand, if the transmission line L2 is also abnormal, the cross-connect device 10 searches for a detour. However, in this embodiment, it is extremely rare that the transmission line L2 also becomes abnormal at the same time. In other words, if the active system and backup system are installed on the same route as in conventional equipment, if a cable is cut due to an accident, there is a high possibility that both the active system and the backup system will go into an abnormal state. Assuming that backup lines are secured on two transmission lines with different routes as in the embodiment of the invention, it is extremely rare for the active system and backup system to be in an abnormal state at the same time, so the cost is extremely high compared to conventional systems. A reliable transmission system can be provided.

Since the plurality of transmission paths in this embodiment include transmission paths with different routes, the difference in delay time between the devices of the signal becomes larger compared to system switching within the same path. In the past, there was no appropriate hardware to compensate for this difference in delay time, which became a bottleneck in making equipment more compact and economical, and the same signal was not transmitted over transmission lines with different routes. However, with the integration and economicalization of semiconductor memory technology, it has become almost no problem to provide elastic memory in terms of cost and volume. For example, the relationship between delay time difference and memory capacity is the value obtained by dividing the delay time difference by the bit rate. If a memory of 1 is obtained, the difference in delay time can be absorbed.

In addition, the cross-connect device IO and the terminal device 11.12
are not fixed to each other. For example, a signal from another cross-connect device (not shown) may be transmitted to the terminal device 21.
．． 31, and signals from this cross-connect device may be connected to other terminal devices (not shown).

In the first embodiment described above, there are two transmission lines, and the system is switched between two sending and receiving end systems.

However, reliability can be further improved if the number of transmission lines is three or more.

FIG. 2 shows a second embodiment in which the number of transmission lines is three or more.

In this embodiment, the same signal is transmitted from the cross-connect device 10 to four transmitting terminal devices 11.12, 3.1 and 3.1.
4 to the receiving side terminal device 21.31.41.51 through four transmission paths L1, L2, L3, and L4. This transmission line -L uses a large capacity optical fiber transmission line. Here, the transmission lines L1 and L2 are the same route, and the transmission line L3 is the same route.

It is assumed that the transmission line L1 and are the same route, and the transmission line L1 and are different routes.

The outputs of the receiving side terminal devices 21 and 31 are connected to the switching circuit 61
is input to and selected by the receiving side terminal equipment 41 and 51.
The output of is input to the switching circuit 62, selected, and input to the switching circuit 63. This switching circuit 61~
63 is a 2:1 switching device, and the switching control circuit 7
Switching from 0 to 0 is controlled simultaneously by a switching control signal. Further, the switching circuits 61 to 63 have a function of simultaneously switching multi-channel signals after demultiplexing. In addition, each receiving side terminal device 21, 31, 41, 51 is provided with a monitoring circuit 23, 33, 43, 53 that monitors signal disconnection of the transmission path, code error rate measurement, etc. The output is input to a switching control circuit 70.

Next, the operation of the second embodiment of the present invention will be explained.

The signals from the cross-connect device 10 are simultaneously sent to the transmitting side terminal devices 11 to 14, multiplexed with other information, and transmitted on the transmission lines L1 to L4, and this signal is transmitted at the receiving end of each transmission line. End office bag Wt21.31.41.5
1 is received.

Assume that the switching circuits 61 and 63 are set so that information is transmitted from the transmitting end to the receiving end via the transmission path. In this state, if a signal disconnection or a line abnormality such as deterioration of the error rate exceeding a predetermined value occurs in the transmission path L1, an alarm signal is sent from the monitoring circuit 23 of the terminal device 21 to the switching control circuit 70. Upon receiving this alarm signal, the switching control circuit 70 checks the operating state of the transmission line L2, and if there is no abnormality in the transmission line L2, sends a switching control signal to the switching circuit 61 to switch to the transmission line L2 side. . At this time, signals can be switched without momentary interruption, except when the signal synchronization state is disrupted, such as when a line is disconnected.

On the other hand, if transmission line L2 also has a line abnormality at the same time,
The status of the transmission lines L3 and L4 is checked, and if there is a normal line, the switching circuit 63 is switched to ensure normal communication. The switching circuit 62, which selects the transmission lines Ls and L4, performs a switching control operation so as to always connect a normal line to the switching circuit 63 even when it is in a standby state. That is, the switching circuit 63
If the transmission quality deteriorates in the transmission line L3 while the transmission line L3 is selected, and the transmission line is operating normally, the switching circuit 62 switches to the transmission line L4,
The transmission line is kept on standby as a backup line.

In the first and second embodiments described above, a redundant configuration was adopted for all transmitted signals, but in this case, line utilization efficiency was sacrificed in order to ensure reliability. For this reason, this redundancy is changed depending on the importance of the information to be transmitted, and important information is transmitted over many transmission paths.
By transmitting unimportant information through a small number of transmission channels,
The utilization efficiency of the entire transmission path can be improved. In this way, the third embodiment changes the redundancy of transmission depending on the importance of the transmitted information.

FIG. 3 is a diagram showing the configuration of this third embodiment.

This third embodiment is an example of a transmission system in which information is transmitted through three transmission lines L1, L2, and L3 having different routes.

In this embodiment, three redundancies are set for the information transmitted from the cross-connect device 10. Information a is the redundancy level of triplex transmission using three transmission lines, information A is redundancy level of duplex transmission using two transmission lines, and information C is redundancy level 3 with no redundancy level.
The weighting of the stages is set. That is, information a is sent to the terminal equipment 21.31 corresponding to the three transmission paths L1 to L3.
．． 41 receiving sections 22, 32, and 42 at the same time.

The information is simultaneously transmitted to the receiving sections 22 and 32 via two transmission paths. Information C is transmitted to the receiver 842 of the single terminal device 41.

These pieces of information are demultiplexed to take out the original signals, which are separated into units of weighting.In the terminal equipment 21, information a is stored in the memory 24 and output to the switching circuit 61, and all of the information is is stored in the memory 25 and transferred to the switching circuit 6.
Output to 2. In the terminal device 31 , information a is stored in the memory 34 and output to the switching circuit 61 , and information a is stored in the memory 35 and output to the switching circuit 62 . In the terminal station bag [41], information a is stored in the memory 44 and outputted to the switching circuit 61, and information C is outputted as is to the cross-connect device 80 on the receiving side.

The switching control circuit 70 detects alarm outputs from the monitoring circuits 23, 33, and 43 of each terminal equipment, grasps the status of each transmission path, and switches the switching circuits 61, 6 to each switching circuit 61, 6 as in the above-described embodiment.
2 switching control is performed. The switching circuit 61 selects information a from among the three transmission paths, and the switching circuit 6
Step 2 selects two transmission paths for information.

In this way, by changing the redundancy depending on the importance of the information to be transmitted, the utilization efficiency of the transmission path can be increased, and high reliability can be obtained for signals with high redundancy.

Next, a fourth embodiment will be described.

The first and second embodiments described above are described for the case where one-to-one communication is performed between two terminal stations.
The present invention is not limited to such communication systems. The present invention is also applicable to networks with multiple nodes. In this case as well, it is possible to increase redundancy by transmitting the same signal to important points via many routes, and to reduce redundancy by transmitting the same signal to less important points via fewer routes. It is possible.

Even in one-to-one communication between nodes, if the communication system includes other nodes on transmission paths with different routes to the target node, the nodes that pass along the way are simply relay devices. As a result, it is possible to create a configuration in which the redundancy of the transmission path is increased.

In other words, by providing the terminal device of a node passing along the way with the function of demultiplexing the received signal and immediately multiplexing it as a transmission signal and sending it out to the next transmission path, it is possible to treat the node in the middle as a relay device. be. This fourth embodiment is shown in FIG.

In this fourth embodiment, to simplify the explanation, the redundancy is 2.
, that is, transmission paths with mutually different routes, and L
2, an example will be described in which a signal a with this terminal device as the receiving end is multiplexed with other signals and transmitted.

The signal on the transmission path L1 is input to a multiplexing/demultiplexing circuit (DMUX) 26, and is separated into a signal a whose receiving end is this node and a signal a whose receiving end is another node. The separated signal a is temporarily stored in the memory 24. In addition, the signal on the transmission line L2, which is on a different route from the transmission line, is input to the demultiplexing circuit 36, and is separated into a signal a whose receiving end is this node and a signal C whose receiving end is another node. Signal a is stored in -H memory 34. The signals stored in the memories 24 and 34 are read out in synchronization, and the switching circuit 60 manually performs the receiving end switching by the same switching as in the first and second embodiments.

Further, the alarm outputs of the monitoring circuits 23 and 33 are input to the switching control circuit 70 to control the switching selection of the switching circuit 60.

On the other hand, the signal that has been multiplexed with the signal a and transmitted through the transmission line L1 and whose receiving end is the other 7-mode signal is demultiplexed by the demultiplexing circuit 26.
After demultiplexing, the signal is multiplexed with the signal d to be transmitted from this node in the multiplexing circuit (MUX) 27 without any termination processing, and is transmitted to another node via the transmission path L3. Further, the signal C, which is multiplexed with the signal a and transmitted through the transmission line L2 and is sent to another node as the receiving end, is demultiplexed by the demultiplexing circuit 36, and the signal C is transmitted from this node by the multiplexing circuit 37. Multiplexed with signal e and sent to transmission line L
4.

Note that when the transmission end and the reception end are not 1:1 but n:n, the communication system may be configured such that different routes are assigned for upstream and downstream signals.

Although the signal path is shown by one line in FIG. 4, it can also be seen as corresponding to a plurality of channels rather than one channel of a multiplexed signal.

Furthermore, in the above-mentioned Embodiments 1 to 4, the switching circuit is located at the position of the electrical circuit that processes the optical signal using the electrical signal after photoelectric conversion, but the switching circuit may also switch the optical signal on the optical fiber as it is. .

〔Effect of the invention〕

As described above, the present invention employs a redundancy method in which the receiving end always receives the same signal that has passed through multiple transmission paths including different routes, and the receiving end determines and executes failure detection line switching. , it is possible to realize an extremely reliable transmission system.

This redundant transmission system allows normal communication as long as two or more transmission systems do not fail at the same time, and does not require the complicated procedure of searching for a detour when one route fails, unlike conventional methods. .

In other words, all decisions can be made on the receiving side and executed immediately, so the switching procedure can be extremely simplified and maintainability can be greatly improved.

Furthermore, in principle, it is possible to immediately detect a failure as soon as it occurs and switch over without interruption, making it possible to improve the reliability of the transmission path.

Completion diagram.

10.80... Cross-connect device, 11-14...
- Terminal device (transmission section), 21.31.4151... Terminal device, 22.32.42.52... Receiving section, 23.
33.43.53...Monitoring circuit, 24.25.34.
35.44.54...Memory, 60.61.6'2.
63... Switching circuit, 70... Switching control circuit, 26.36... Multiplexing/demultiplexing circuit, 27.37... Multiplexing circuit.

Patent applicant: Nippon Telegraph and Telephone Corporation Agent: Patent Attorney Naotaka Ide

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention. FIG. 2 is a configuration diagram of a second embodiment of the present invention. FIG. 3 is a configuration diagram of a third embodiment of the present invention.

Claims (1)

[Claims] 1. In a transmission system comprising a transmitting side, a receiving side, and a plurality of optical fiber transmission lines including different paths connecting the transmitting side and the receiving side, the transmitting side has the above-mentioned A means for transmitting the same signal to a plurality of transmission paths is provided, and the receiving side includes a means for compensating for relative delays of a plurality of signals transmitted through the plurality of transmission paths, and a means for monitoring the transmission path. A receiving end switching transmission system comprising a monitoring means and a switching means for selecting a signal from a normally operating transmission line based on monitoring information from the monitoring means. 2. The receiving end switching transmission system according to claim 1, wherein the transmitting side includes means for weighting signals to be transmitted according to their importance and transmitting signals with high importance to many transmission paths.