JP2002026947A - Network transmission method and its system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a network transmission system that maintains optical communication without giving effect on other node even on the occurrence of a fault. SOLUTION: Nodes 10-14 detect an optical signal level received by an O/E section and conduct optical transmission by reducing the optical signal level oscillated in each E/O section when the detection indicates a faulty signal level, inform the node 10 about a notice attended with the signal level revision, sets a port of the fault occurrence side to be in a disconnected state, and when the node 10 receives the notice, the node 10 connects the port of the disconnected node 14 to an optical transmission line 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network transmission method in which a network is constructed in a loop and a system therefor.

[0002]

2. Description of the Related Art Conventionally, in this type of system, for example, a plurality of LAN switches are connected in a loop via a transmission line, and a spanning switch is connected to the LAN switch so that a loop ring cannot be formed in the entire network. In some cases, a tree function is provided to limit the number of routes actually used to one. In the above system, when a failure occurs in a line, the path is switched to perform frame transmission.

[0003]

However, in the above system, when a failure occurs, each LAN switch is connected to another LAN switch.
Since the addresses assigned to the AN switches are sequentially designated and packets for monitoring the link status are transmitted, and each LAN switch detects a failure point, it takes a long time to detect the failure.

The present invention has been made in view of the above problems, and has as its object to provide a network transmission method and system capable of maintaining optical communication without affecting other nodes even when a failure occurs. And

[0005]

In order to achieve the above object, according to the present invention, a first node and a second node are connected in a loop via a transmission line, and the first and second nodes are connected. Switch means comprising a switching hub having a plurality of physical ports for signal input / output; and control means comprising a control unit for controlling the switch means to output an electric signal of an IP packet configuration to a corresponding port. A transmitting unit connected to the port for optically converting the electric signal to transmit the electric signal to the transmission line; and converting an optical signal received and connected to the transmission line to the electric signal. Receiving means comprising an O / E section for outputting to the port, wherein the control means of the first node sets one of the ports to which the transmission path is connected to a disconnected state to disconnect the signal transmission path. In a network transmission system which sets one and transmits an optical signal between the nodes, the first and second nodes detect an optical signal level of the light received by the receiving means. Light level detection means comprising a portion, according to the detected signal level,
There is provided a network transmission system comprising: an output level control unit including an output level control unit configured to change and control a signal level of light oscillated from the transmission unit.

That is, the first and second nodes detect the signal level of the received light, and if the detected signal level is abnormal, reduce the signal level of the oscillating light to perform optical transmission. Or off, and notifies another node of the change in the signal level, sets the port on the abnormal side to a disconnected state,
When the node receives the notification, it connects the disconnected port to the transmission line, thereby maintaining optical communication without affecting other nodes even when a failure occurs.

Further, in the present invention, the control means periodically makes a response request for testing a connection state with an adjacent node, and if a response to the request is not made continuously a predetermined number of times, an abnormality is generated. By detecting and controlling the switch means to notify the other node of the occurrence of the abnormality, and setting the port on the side where the abnormality has occurred to the disconnected state, the influence on the other nodes even in the event of a failure can be obtained. Maintain optical communication without giving.

Further, according to the present invention, there is provided a bypass circuit comprising a bypass circuit and an optical attenuator for bypassing light from the transmission line, and the first and second nodes are provided with:
The controller has an operation check unit comprising an operation check unit for checking its own operation, and the operation check unit controls the bypass unit to emit light from the transmission line when the occurrence of an abnormality in the operation is checked. When the signal level of the oscillating light is reduced by controlling the transmitting means to reduce the signal level of the oscillating light or the power supply of the abnormal part is turned off, and the operation is restored to the normal state, the signal level of the oscillating light is set to the normal state The optical communication is maintained without affecting other nodes even when a failure occurs, by changing the power to the power supply or turning on the power of the portion where the abnormality has been recovered, and stopping the bypass of light from the transmission line.

Further, according to the present invention, there is provided a bypass unit for bypassing light from the transmission line,
And a second node having a detection unit including a voltage detection unit for detecting a power supply voltage of a power supply, wherein the detection unit controls the bypass unit when the abnormal occurrence of the power supply voltage is detected to perform the transmission. When the power from the path is bypassed, and the signal level of the oscillating light is reduced by controlling the transmitting means or the power of the abnormal part is controlled to be turned off, and the power supply voltage is restored to normal, the oscillating light is By changing the signal level to the normal state or turning on the power of the part where the abnormality has been recovered, and by stopping the light bypass from the transmission line, the light is not affected to other nodes even when a failure occurs. Maintain communication.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a network transmission method and system according to the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram showing a schematic configuration of a network transmission system according to the present invention. In the figure, a first node 10 and a plurality of second nodes 11 to
14 are connected in a loop via an optical transmission line 15. The node 10 is connected to a higher-level network via an optical transmission line 16, and the nodes 11 to 14
7, each of the nodes 10 to 14 is connected to an Ethernet (registered trademark).
An IP (Internet Protocol) packet signal having a packet configuration having an (Ethernet (registered trademark)) header is transmitted to the terminal device 20 connected to the branch line 17 which is a signal line. In the present embodiment, the optical transmission lines 15 and 16
Are two-line optical transmission lines 15a, 15b and 16a, respectively.
16b, the optical transmission path 15a is a path for transmitting the IP packet signal from the node 10 to the node 14 and the optical transmission path 15b is a path for transmitting the IP packet signal from the node 14 to the node 10; 16a is the node 10
The optical transmission path 16b is a path for transmitting the IP packet signal from the upper network to the node 10.

As shown in the block diagram of FIG. 2, the node 10 is connected to a switching hub 10a in which addresses are assigned to input / output ports, and is connected between the optical transmission line 15a and the ports to perform optical / electrical conversion. O / E unit 10b and E / O unit 10c for performing electrical / optical conversion, and optical transmission line 15
b / O / E unit 10d and E / O unit 10e connected between the port and the port to perform optical / electrical conversion and electrical / optical conversion, and connected between the optical transmission line 16a and the port to perform the electrical / optical conversion. An O / E unit 10f for performing optical / electrical conversion by being connected between the optical transmission line 16b and the port;
The optical level detectors 10h and 10i detect the level of light received by the / E units 10b and 10d, and control the output level of light transmitted from the E / O units 10c and 10e according to the detected light levels. Output level control units 10j and 10k
And a control unit 10m that determines a failure based on the detection results of the light level detection units 10h and 10i. Although the nodes 10 and 14 are physically connected, when the system is in a normal state, the control unit 10m
Disconnects the port of the switching hub 10a on the node 14 side, and the optical IP packet signal transmitted from the upper network is transmitted from the node 11 to the nodes 12, 13, 14 via the optical transmission line 15a. And transferred
The IP packet signal from the node 14 is transmitted to the optical transmission path 15b
Are transferred to the nodes 13, 12, 11, and 10 via. When a failure occurs, the control unit 10m connects the port of the switching hub 10a on the node 14 side to the optical transmission line 15a.
a and 15b, and the optical IP packet signal transmitted from the upper network via the optical transmission line 16a is transferred from the node 11 side and the node 14 side, respectively.

The nodes 11 to 14 have the same configuration. Here, the configuration of the node 11 will be described with reference to FIG. 3 as a representative. In the figure, a node 11 is a switching hub 11a in which addresses are assigned to input / output ports, and an O / E that is connected between the optical transmission line 15a and the ports to perform optical / electrical conversion and electrical / optical conversion. Part 11
b / E / O unit 11c, and O / O that is connected between the optical transmission line 15b and the port and performs optical / electrical conversion and electrical / optical conversion.
E section 11d and E / O section 11e, and O / E section 11b, 1
1d, light level detectors 11f and 11g for detecting the level of light received, and E / O according to the detected light level.
Output level control units 10h and 10i for controlling output levels of light transmitted from the units 11c and 11e, a control unit 10j for determining a failure based on detection results of the light level detection units 10f and 10g, And an input / output unit 11k for connecting to the branch line 20. Optical transmission line 15
a, 15b, the IP packet signal
Switching hub 11a via E sections 11b and 11d
, And refers to the destination address of the packet, and determines whether to transfer the packet to the adjacent node or to the terminal device 20 connected to the input / output unit 11k of the own node.

In such a state, the optical transmission line, the E / O unit,
A first embodiment of a failure processing operation and a recovery processing operation when a failure occurs in the O / E unit will be described with reference to the flowcharts of FIGS. In the following embodiment, for example, a case where a failure occurs due to disconnection of the optical transmission line 15a between the nodes 12 and 13 will be described. First, in FIG.
Detects the reception level of the light received by the O / E section 13b on the node 12 side by the optical level detection section 13f, and when the reception level is abnormal, the output level control section 13i causes the E / E section on the node 12 side to It controls the transmission level of the light transmitted from the O unit 13e to be lower than the normal state, and notifies the partner node 12 of the abnormal state. Therefore, in the present embodiment, for example, when the light reception level drops from −30 dBm to −40 dBm or less in the normal state, the light transmission level is set to −20 dBm from −10 dBm in the normal state and transmitted to the node 12. The set value of the light level is determined in advance between the nodes when the system is constructed.

The abnormality of the reception level is also transmitted from the light level detection unit 13f to the control unit 13j.
3j notifies the occurrence of a failure from the E / O unit 13c on the node 14 side to the node 10 via the switching hub 13a. The notification may be performed by designating the address of the node 10 as a destination by an optical IP packet signal, or may be performed by lowering the optical level as described above.

In the node 12, the optical level detection unit 12g on the node 13 side detects that the reception level of light has dropped,
When recognizing the abnormality, the control unit 12j notifies the occurrence of a failure by transmitting an IP packet signal specifying a destination address from the E / O unit 12e on the node 11 side to the node 10 via the switching hub 12a. . However, in the failure mode in which both the optical transmission lines 15a and 15b between the nodes 12 and 13 are disconnected, the O / O
Since no light is transmitted to the portion E, a failure can be detected by detecting a light level of −40 dBm or less.

The node 10 that has received the notification of the failure occurrence
Connects the port on the node 14 side to the optical transmission line 15,
The upper network is notified using an IP packet signal. After notifying the node 10 of the occurrence of the failure, the control units 12j and 13j of the nodes 12 and 13 set the abnormal ports of the switching hubs 12a and 13a to the disconnected state,
A test for testing the open state of the node 10;
For example, an opening test using a ping is performed, and if the test passes without any abnormality, the abnormality processing ends.

Next, the operation of the recovery process will be described.
In FIG. 5, when recovery from a failure such as disconnection of the optical transmission line is performed, the reception level of the O / E unit 13b on the node 12 side of the node 13 which has been abnormal returns to normal.
This is detected by the optical level detector 13f, the output level controller 13i returns the E / O unit 12e on the node 12 side to normal, and the controller 13j notifies the node 10 of normal recovery.

In the node 12, when the light reception level detected by the light level detection unit 12g on the node 13 returns to normal, the control unit 12j notifies the node 10 of normal recovery. When receiving the notification of the normal recovery from both the nodes 12 and 13, the node 10 waits for an instruction as to whether the recovery processing can be started. This instruction is performed, for example, by a notification from a console (not shown) connected to the node 10 or an upper network. Upon receiving the instruction notification, the node 10 notifies the nodes 12 and 13 to start recovery, disconnects the port on the node 14 side, and performs ping for testing the open state with the node 13. The opening test used is performed, and if the test passes without any abnormality, the abnormality processing is terminated.

When the nodes 12 and 13 receive the instruction notification, the nodes 12 and 13 connect the disconnected port to the optical transmission line, and the node 13 returns an ACK for responding to the opening test to perform the recovery processing. To end. In addition, even if a failure occurs in the E / O unit or the O / E unit in each node, the light level decreases similarly to the above-described disconnection of the optical transmission line, so that the failure processing and the recovery processing can be performed by the above method. is there.

As described above, in the present embodiment, the node that has detected a failure in the loop-like connection path changes the connection path by performing the failure processing and the recovery processing, so that other nodes are affected even when a failure occurs. Without this, optical communication can be maintained. Further, in this embodiment, since only a predetermined node performs the failure processing and the recovery processing in real time, the time required for the failure processing and the recovery processing can be reduced, and the processing can be performed quickly.

Next, a second embodiment of the failure processing operation and the recovery processing operation of the network transmission system according to the present invention will be described with reference to the flowcharts of FIGS. First, in FIG. 6, when the optical level detection unit 13f detects an abnormality in the reception level, the output level control unit 13i controls the transmission level of the light transmitted from the E / O unit 13e on the node 12 side to the off state. Then, it notifies the partner node 12 of the abnormal state. The control unit 13j notifies the node 10 of the occurrence of a failure from the E / O unit 13c on the node 14 side via the switching hub 13a.

In the node 12, the optical level detector 12g detects that the light reception level is off, and when the controller 12j recognizes the abnormality, the controller 12j sends the node from the E / O unit 12e on the node 11 side via the switching hub 12a. 10 is notified that a failure has occurred. Upon receiving the failure notification, the node 10 connects the port on the node 14 side to the optical transmission line 15,
The upper network is notified using an IP packet signal.

After notifying the occurrence of the failure, the node 1
The control units 12j and 13j of the switching hubs 2 and 13 set the abnormal ports of the switching hubs 12a and 13a to a disconnected state, perform a test on the node 10 to recognize the open state, and pass the test without any abnormality. The abnormal processing ends. Next, the operation of the recovery process will be described. In FIG.
A signal for detecting the reception level OFF from the optical level detector 13f is output to, for example, a switch element provided on a signal line connecting the optical level detector 13f to the output level controller 13i and the optical level detector 13f to the controller 13j ( (Not shown), the output level control unit 13i
The E / O unit 12e on the side is returned to normal, and the control unit 13j notifies the node 10 of normal recovery.

When the node 12 detects that the optical reception level from the node 13 is normal, the node 12 returns the optical transmission level of the node 12 to normal, and the control unit 12j restores the normal state.
Notify. Upon receiving the notification of the normal recovery from both the nodes 12 and 13 and receiving the instruction notification of the start of the recovery processing, the node 10 notifies the nodes 12 and 13 to start the recovery and changes the port on the node 14 side. Into a disconnected state,
Further, an opening test is performed with the node 13, and if the test passes without any abnormality, the abnormal processing is terminated.

When the nodes 12 and 13 receive the instruction notification, the nodes 12 and 13 connect the disconnected port to the optical transmission line, and
The node 13 returns an ACK for a response to the opening test and ends the restoration processing. Thus, in the present embodiment,
By turning off the light transmission level when a failure occurs,
The same effect as in the first embodiment can be obtained.

Next, a third embodiment of the failure processing operation and the recovery processing operation of the network transmission system according to the present invention will be described with reference to the flowcharts of FIGS. In this embodiment, the failure processing is not performed based on the detection of the light level, but is performed by performing a periodic connection test. First, in FIG. 8, a connection test (for example, a confirmation operation by ping) is periodically performed between the adjacent nodes 12 and 13, and if an error occurs consecutively a predetermined number of times (timeout in the case of ping), a failure occurs. And notifies the node 10. When all the optical transmission lines between the nodes 12 and 13 are disconnected, the above notification from the node 13 to the node 10 does not arrive but the notification from the node 12 arrives.

When receiving the above notification, the node 10 connects the port on the node 14 side to the optical transmission line, and ends the above operation. After notification of the occurrence of shogi, the nodes 12 and 13 set the abnormal port to the disconnected state, perform an opening test from the port on the opposite side to the port on the other side, and end the above processing if the test passes.

Next, as shown in FIG. 9, when the recovery from the failure is performed, a notification of the recovery is sent to the node 10 from, for example, a console or an upper network. Node 10
Upon receiving the above notification, it recognizes that the failure has been recovered and
The port on the fourth side is set in the disconnected state, the nodes 12 and 13 are notified, and the above processing is terminated. The nodes 12 and 13 respectively connect the disconnected ports of the other party to the optical transmission lines, perform an opening test on each other, and terminate the above processing if the tests pass.

As described above, in the present embodiment, the occurrence of a failure is detected by performing a periodic connection test between nodes adjacent to each other, and the detected node performs failure processing and recovery processing to change the connection path. Therefore, the same effect as in the first embodiment can be obtained. In the third embodiment,
By performing a periodic connection test between the control unit of the node 12 and the switching hub of the node 13, and between the control unit of the node 12 and the control unit of the node 13, the optical transmission line, the E / O unit, and the O It is possible to distinguish between a fault in the / E section and the switching hub and a fault in the control section and the power supply section by a periodic connection test. However, when a part of the control software or hardware in the control section of the node 12 fails, the fault is detected. May not be possible.

Therefore, a method for coping with the occurrence of a failure in the control unit and the power supply unit in the own node will be described below. FIG.
FIG. 9 is a configuration diagram showing another example of the configuration of the node 11 shown as a representative of the second node. In the figure, the difference from the configuration of FIG. 2 is that the splitters 11m and 11n are provided on the optical transmission line 15a instead of the optical level detector and the output level controller.
The splitters 11o and 11p are connected to the optical transmission line 15b, and the bypass optical transmission lines 11q and 11r are provided between the splitters 11m and 11n and between the splitters 11o and 11p.
The optical switches 11s and 11t are connected to 1r, the optical switches 11s and 11t and the E / O units 11c and 11e are connected to a control unit operation check unit 11u that checks the operation of the control unit, and a power supply unit (not shown) in the node. Voltage detector 1 for detecting voltage
1v. Note that the splitter 11
m to 11p, optical transmission lines 11q and 11r, and optical switch 1
1s and 11t constitute a bypass unit of the present invention, and the control unit operation check unit 11u and the voltage detection unit 11v constitute an operation check unit and a voltage detection unit of the present invention, respectively.

A fourth embodiment of a failure processing operation and a recovery processing operation when a failure occurs in the control unit and the power supply voltage in such a configuration will be described. First, the control unit operation check unit 11u determines that the control unit 11j is operating normally by accessing it periodically. Control unit operation check unit 11
u provides a timer internally, determines that a failure has occurred if there is no access for a certain period of time or more,
1s and 11t are turned on and the optical transmission lines 11q and 11r are turned on.
To establish a bypass path and E / O
The optical transmission levels of the units 11c and 11e are reduced or the power of the E / O units 11c and 11e is turned off. Also,
The voltage detection unit 11v detects the voltage of the power supply unit, and when a failure occurs in the voltage, similarly to the above, turns on the optical switches 11s and 11t to establish a bypass path, and also sets the E / O unit. The optical transmission levels of 11c and 11e are reduced or the power of the E / O units 11c and 11e is turned off.

Thus, in the present embodiment, the optical signal from the adjacent node is transferred to the other adjacent node, bypassing the failed node. And
When these faults are recovered, the control unit operation check unit 11
u or the voltage detection unit 11v includes the optical switches 11s and 11t.
Is turned off, the optical transmission lines 11q and 11r are disconnected, and the optical transmission levels of the E / O units 11c and 11e are set to a normal state, or power is turned on to the E / O units 11c and 11e. Next, an opening test is performed with an adjacent node, and if the test passes, the above-described processing operation is terminated and an optical signal is transferred via the node that has recovered from the failure.

As described above, in the present embodiment, when a failure occurs, the optical signal can be transferred by bypassing the node in which the failure has occurred, so that the same effect as in the first embodiment can be obtained. In the present embodiment, the optical switch 11s is connected to the optical transmission line 11q as shown in FIG. 11, but the present invention is not limited to this. For example, as shown in FIG. Part 11b and one end of the optical transmission line 11q,
The other end of the E / O unit 11c and the optical transmission line 11q is connected to the optical switch 1
It is also possible to configure so as to switch and connect each of 1s1 and 11s2. Furthermore, the optical transmission line 1
The optical attenuator 11s3 is connected to 1q, the optical attenuator 11s3 is operated in a normal state, the optical transmission line 11q is apparently cut off, and when a failure occurs, the operation is stopped and the optical transmission line 11q is connected. It is also possible to configure the state.

The present invention is not limited to these embodiments, and various modifications can be made without departing from the gist of the present invention. For example, the methods of the first to fourth embodiments according to the present invention can be appropriately combined and used. Further, the present invention is also applicable to a multi-drop system that performs bidirectional optical transmission over a single-core optical transmission line.

[0035]

As described above, according to the present invention, the first
And the second node detects a signal level of the light received by the receiving means with an optical level detecting means, detects a failure according to the detected signal level, and oscillates from the transmitting means when the failure occurs. Is controlled by the output level control unit, so that optical communication can be maintained without affecting other nodes even when a failure occurs.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a schematic configuration of a network transmission system according to the present invention.

FIG. 2 is a configuration diagram illustrating an example of a configuration of a first node illustrated in FIG. 1;

FIG. 3 is a configuration diagram illustrating an example of a configuration of a second node.

FIG. 4 is a flowchart for explaining a first embodiment of an abnormality processing operation of each node in the network transmission method according to the present invention.

FIG. 5 is a flowchart for explaining a first embodiment of a recovery processing operation of each node.

FIG. 6 is a flowchart for explaining a second embodiment of the abnormality processing operation of each node.

FIG. 7 is a flowchart for explaining a second embodiment of the recovery processing operation of each node.

FIG. 8 is a flowchart for explaining a third embodiment of the abnormality processing operation of each node.

FIG. 9 is a flowchart for explaining a third embodiment of the recovery processing operation of each node.

FIG. 10 is a configuration diagram illustrating another example of the configuration of the second node illustrated in FIG. 1;

FIG. 11 is a configuration diagram illustrating a schematic configuration of a first embodiment of the bypass unit illustrated in FIG. 10;

FIG. 12 is a configuration diagram showing a schematic configuration of a second embodiment of the bypass unit.

FIG. 13 is a configuration diagram showing a schematic configuration of a third embodiment of the bypass unit.

[Explanation of symbols]

10 to 14 nodes 10a, 11a Switching hubs 10b, 10d, 10g, 11b, 11d O / E units 10c, 10e, 10f, 11c, 11e E / O units 10h, 10i, 11f, 11g Optical level detection units 10j, 10k, 11h, 11i Output level control unit 10m, 11j Control unit 11k Input / output unit 11m to 11p Splitter 11q, 11r, 15, 15a, 15b, 16, 16
a, 16b Optical transmission line 11s, 11s1, 11s2, 11t Optical switch 11s3 Optical attenuator 11u Control unit operation confirmation unit 11v Voltage detection unit 17 Signal line 20 Terminal device

Continued on the front page (72) Inventor Tomohiro Arasawa 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. F-term (reference) 5K002 AA05 BA06 CA09 DA11 EA05 EA33 FA01 5K014 AA01 CA07 FA01 5K031 AA08 CB06 CB12 DA02 DA12 DA19 EA03 EB10 5K035 BB02 CC08 EE04 HH04 KK05 LL17

Claims (23)

[Claims] A first node having a plurality of signal input / output physical ports and a second node connected in a loop via a transmission line; A network transmission method for transmitting an optical signal between the nodes by setting one of the connected ports to a disconnected state and setting a single signal transmission path, wherein the first and the second The node detects the signal level of the received light, changes the signal level of the oscillating light according to the signal level, and notifies other nodes of the signal accompanying the signal level change. A network transmission method, wherein the first node, upon receiving the notification, connects the disconnected port to the transmission path. 2. When the detected signal level is abnormal, the first and second nodes perform optical transmission by lowering the signal level of oscillating light, and The node that has received the signal with the signal level change, sets the port on the abnormality occurrence side to the disconnected state, and receives the light with the changed signal level with respect to another node. 2. The network transmission method according to claim 1, wherein the notification is performed, and the port on the abnormality occurrence side is set to a disconnected state. 3. The node that has changed the signal level changes the signal level of the oscillating light to a signal level of a normal state when the signal level of the detected light returns to a normal state. And, to another node, performs a notification associated with the signal level change, the node that receives the light whose signal level has been changed, to another node, performs a notification associated with the signal level change, and The first node connects the disconnected port to the transmission line, and upon receiving the notification, the first node performs a confirmation of the abnormality recovery process, and then performs a notification accompanying the confirmation to another node. And setting the one port connected to the transmission path to a disconnected state, wherein the node that has changed the signal level and the node that has received the light with the changed signal level are the first node Previous The network transmission method according to claim 1, wherein upon receiving a notification accompanying the confirmation, the disconnected port is connected to the transmission path. 4. When the detected signal level is abnormal, the first and second nodes change the signal level of the oscillating light to an off state, and output the signal level to another node. The node that has performed the notification according to the level change, sets the port on the abnormality occurrence side to the disconnection state, and detects the abnormality of the optical signal level due to the off state, notifies another node of the abnormality detection. 2. The network transmission method according to claim 1, further comprising: changing a signal level of the oscillating light to an off state, and setting a port on the abnormality occurrence side to a disconnected state. 5. The node that has changed the signal level changes the signal level of the oscillating light to a normal signal level when the detection of the signal level of the light is stopped, and For the node, a notification accompanying the signal level change is performed, and the node that receives the light whose signal level has been changed to the normal state changes the signal level of the oscillating light to the signal level of the normal state, and The first node notifies the other nodes of a notification associated with the signal level change. Upon receiving the notification, the first node confirms the abnormality recovery processing, and then performs the confirmation to the other nodes. Performing the notification according to, and setting the one port connected to the transmission path to a disconnected state, the node that has changed the signal level and the node that has received the light with the changed signal level are the No. 5. The network transmission method according to claim 1, wherein upon receiving a notification accompanying the confirmation from one node, the disconnected port is connected to the transmission path. 6. 6. A node that is adjacent to each other and that has changed the signal level and a node that has received the light whose signal level has been changed, tests an open state through a port connected to the transmission line. 6. The network transmission method according to claim 3, wherein a response request is made. 7. A first node having a plurality of physical ports for inputting and outputting signals and a second node are connected in a loop via a transmission line, and the first node is connected to the transmission line by a transmission line. A network transmission method for transmitting an optical signal between the nodes by setting one of the connected ports to a disconnected state and setting a single signal transmission path, wherein the first and the second The node periodically makes a response request for testing a connection state with an adjacent node, and when a response to the request is not continuously made a predetermined number of times, detects an occurrence of an abnormality and, for another node, Notifying the occurrence of an abnormality, setting the port on the abnormality occurrence side to a disconnected state, and upon receiving the notification, the first node connects the disconnected port to the transmission line. network Method Carriage. 8. The first node, after confirming the abnormality recovery processing, sets the one port connected to the transmission line to a disconnected state, and sets the one port to another node. 8. The communication device according to claim 7, wherein a notification accompanying the confirmation is performed, and the node that has detected the occurrence of the abnormality connects the disconnected port to the transmission path when receiving the notification accompanying the confirmation from the first node.
2. The network transmission method according to item 1. 9. A first node having a plurality of physical ports for inputting and outputting signals and a second node are connected in a loop via a transmission line, and the first node is connected to the transmission line. A network transmission method for transmitting an optical signal between the nodes by setting one of the connected ports to a disconnected state and setting a single signal transmission path, wherein the first and the second The node performs at least one of its own operation check and power supply voltage detection, and when detecting an abnormality in the operation or detecting an abnormality in the power supply voltage, bypasses the light from the transmission line. And reducing the signal level of the oscillating light or turning off the power of the abnormal part. 10. The node that detects the occurrence of the abnormality, changes the signal level of the oscillating light to a normal state when the operation is restored to normal or the power supply voltage is restored to normal. 10. The network transmission method according to claim 9, wherein power is supplied to a portion where the abnormality has been recovered, and the bypass of light from the transmission path is stopped. 11. The network transmission method according to claim 8, wherein the node that has detected the occurrence of the abnormality makes a response request for testing an open state to an adjacent node. 12. A network transmission method using a combination of at least two of the network transmission methods according to claim 1, 7, or 9. 13. A first node and a second node are connected in a loop via a transmission line, and the first and second nodes have a plurality of physical ports for signal input / output. Switch means, control means for controlling the switch means to output an electric signal of an IP packet configuration to a corresponding port, and transmission means connected to the port for optically converting the electric signal and transmitting the electric signal to the transmission line Receiving means for converting an optical signal received by being connected to the transmission line into the electric signal and outputting the electric signal to the port,
The control means of the node transmits the optical signal between the nodes by setting one of the ports to which the transmission path is connected to a disconnected state and setting one signal transmission path. In the system, the first and second nodes oscillate from the transmitting unit according to the detected signal level, and an optical level detecting unit that detects a signal level of the light received by the receiving unit. A network transmission system comprising: output level control means for changing and controlling a light signal level. 14. The output level control means, when the signal level detected by the light level detection means is abnormal, lowers the signal level of the oscillating light from a normal state and transmits the light to the transmission line. 14. The network transmission system according to claim 13, wherein: 15. The control unit, when the signal level detected by the optical level detection unit is abnormal, notifies another node of the change in the signal level to change the port on the abnormal side. After setting the disconnected state and restoring the detected signal level, the other nodes are notified of the change in the signal level, and the disconnected port is connected to the transmission line. Upon receiving the post-restoration notification, the control means of the node, after confirming the restoration process, performs a notification associated with the confirmation to another node, and connects the one node connected to the transmission path. 14. The network transmission system according to claim 13, wherein the port is set to a disconnected state. 16. The apparatus according to claim 13, wherein the output level control means controls to change the signal level of the oscillating light to an off state when the signal level detected by the light level detection means is abnormal. 2. The network transmission system according to item 1. 17. A node adjacent to each other and detecting a change in the signal level, wherein the control unit issues a response request for testing an open state through a port connected to the transmission line. 14. The network transmission system according to claim 13, wherein: 18. A first node and a second node are connected in a loop via a transmission line, and the first and second nodes have a plurality of physical ports for signal input / output. Switch means, control means for controlling the switch means to output an electric signal of an IP packet configuration to a corresponding port, and transmission means connected to the port for optically converting the electric signal and transmitting the electric signal to the transmission line Receiving means for converting an optical signal received by being connected to the transmission line into the electric signal and outputting the electric signal to the port,
The control means of the node transmits the optical signal between the nodes by setting one of the ports to which the transmission path is connected to a disconnected state and setting one signal transmission path. In the system, the control unit periodically performs a response request for testing a connection state with an adjacent node, and when a response to the request is not continuously made a predetermined number of times, detects an abnormality occurrence, By controlling the switch means for other nodes,
Notifying the occurrence of an abnormality, setting the port on the side where the abnormality has occurred to a disconnected state, and the control means of the first node, upon receiving the notification, connects the disconnected port to the transmission path. Characterized network transmission system. 19. The control means of the first node sets the one port connected to the transmission line to a disconnected state after confirming the recovery processing of the abnormality, and sets the switch means to And performs a notification accompanying the confirmation to another node, and the control unit of the node that has detected the occurrence of the abnormality performs the first
19. The network transmission system according to claim 18, wherein upon receipt of the notification accompanying the confirmation from the node, the disconnected port is connected to the transmission path. 20. A first node and a second node are connected in a loop via a transmission line, and the first and second nodes have a plurality of physical ports for signal input / output. Switch means, control means for controlling the switch means to output an electric signal of an IP packet configuration to a corresponding port, and transmission means connected to the port for optically converting the electric signal and transmitting the electric signal to the transmission line Receiving means for converting an optical signal received by being connected to the transmission line into the electric signal and outputting the electric signal to the port,
The control means of the node transmits the optical signal between the nodes by setting one of the ports to which the transmission path is connected to a disconnected state and setting one signal transmission path. In the system, a bypass unit that bypasses light from the transmission line is provided, and the first and second nodes have an operation confirmation unit that confirms an operation of the node. When the occurrence of an abnormality is confirmed, the bypass unit is controlled to bypass the light from the transmission line, and the transmission unit is controlled to reduce the signal level of the oscillating light or to turn off the power of the abnormal part. When the operation is restored to normal, the signal level of the oscillating light is changed to a normal state, or the power of the portion where the abnormality is restored is turned on, and the bypass of light from the transmission line is turned off. Network transmission system, which comprises causing locked. 21. A first node and a second node are connected in a loop via a transmission line, and the first and second nodes have a plurality of physical ports for signal input / output. Switch means, control means for controlling the switch means to output an electric signal of an IP packet configuration to a corresponding port, and transmission means connected to the port for optically converting the electric signal and transmitting the electric signal to the transmission line Receiving means for converting an optical signal received by being connected to the transmission line into the electric signal and outputting the electric signal to the port,
The control means of the node transmits the optical signal between the nodes by setting one of the ports to which the transmission path is connected to a disconnected state and setting one signal transmission path. In the system, a bypass unit that bypasses light from the transmission line is provided, and the first and second nodes include a voltage detection unit that detects a power supply voltage of a power supply. When the occurrence of an abnormality in the power supply voltage is detected, the control unit controls the bypass unit to bypass the light from the transmission line, and controls the transmission unit to reduce the signal level of the oscillating light or reduce the power supply of the abnormal part. Control to a disconnected state, when the power supply voltage is restored to normal, the signal level of the oscillating light is changed to a normal state, or the power of the part where the abnormality is restored is turned on,
And a network transmission system that stops bypassing light from the transmission path. 22. A node detecting the occurrence of the abnormality,
22. The network transmission system according to claim 18, wherein the control unit issues a response request for testing an open state to an adjacent node. 23. The light level detection means and output level control means according to claim 13, the control means according to claim 18, the bypass means and operation confirmation means according to claim 20, and the bypass means and voltage detection means according to claim 21. A network transmission system comprising a combination of at least two means as claimed in the claims.