JP2624887B2 - Optical input fault detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an optical input fault detection apparatus, and more particularly to an optical input fault which is advantageously applied to an optical node constituting a network such as an optical loop LAN (Local Area Network). It relates to a detection device.

(Prior Art) Conventionally, detection of an optical input failure in an optical loop LAN includes detection of a data bit error due to complete optical input interruption or a decrease in optical input level, and detection of loss of synchronization of a data frame. Each optical node constituting the optical loop LAN is provided with an optical input failure detection device for detecting such an optical input failure. When the optical node receives the optical input failure detection output from the detection device, it automatically switches the system of the optical loop or loops back, and copes with such a failure.

(Problems to be Solved by the Invention) However, in such a conventional technology, an optical loop LAN
When the system switching or loopback of the optical loop for troubleshooting is automatically performed in the case of the input signal failure, there are the following problems.

That is, with respect to a complete input disconnection failure, a failure in the transmission station, a disconnection of the optical fiber, or the like can be considered. in this case,
Since no light is input to the receiving station, the light input detection output from the failure detection device is stable. Therefore, in such a case, the failure handling operation is stable, and communication after the failure handling can be performed normally by the failure handling.

However, when the light input level is reduced due to, for example, deterioration of the light emitting element or the optical fiber on the transmission side, the light input becomes unstable. When the optical input level at this time is a complete abnormal level, the same troubleshooting action as the optical input interruption can be performed, but the optical input level fluctuates near the boundary between the level at which data can be received normally and the abnormal level. In this case, the optical input failure detection output also fluctuates between normal and abnormal, and becomes an unstable output. For this reason, in a node device that automatically performs a failure handling operation based on an optical input failure detection output from the failure detection device, a normal operation and an abnormal operation are alternately repeated, and the operation of the optical loop is unstable. And there is a disadvantage that stable communication cannot be performed.

The present invention solves such disadvantages of the prior art, and accurately determines normal operation and abnormal operation even when the light input level is reduced and fluctuates near the boundary between the normal level and the abnormal level. Accordingly, an object of the present invention is to provide an optical input failure detection device that stabilizes an optical input failure detection output and can stably perform optical communication.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention is provided in an optical node device for constructing an optical network, and detects an input failure of an optical signal received via a transmission line of the optical network. The optical input failure detection device for performing the first and second detections includes a first detection unit for detecting a bit error of a received optical signal, a second detection unit for detecting a synchronization loss of a synchronization signal included in the received optical signal, and a first detection unit. Are connected to the output sides of the detecting means and the second detecting means, and when the second detecting means detects the loss of synchronization,
Control means for controlling the second detection means to output a loss of synchronization until the bit error detection from the first detection means is not continuously detected for a predetermined time.

(Operation) According to the present invention, when a bit error is detected by the first detecting means and the synchronization is detected by the second detecting means, the control means stops detecting the bit error for a predetermined period of time after the bit error is no longer detected. During this time, control is performed such that the second detection means outputs an optical input failure detection output.

(Embodiment) Next, an embodiment of an optical input failure detection device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 shows a system configuration diagram of an optical loop LAN to which an embodiment of the optical input failure detection device according to the present invention is applied. The optical loop LAN system includes a plurality of nodes M (M _{1 to} M _n ) that perform data processing, and these nodes M are connected to adjacent nodes M in a ring shape by a transmission line 300 such as an optical fiber. .

The node M is an optical terminal device that uses light as information transmission means and transmits and receives data to and from each other in synchronization with frame synchronization. The node M is further provided with an optical input failure detection device 1 (FIG. 1) for detecting an optical input failure due to a failure in the node M on the transmitting station side or a transmission line or the like. Node M
When the failure detection device 1 detects an optical input failure, the failure detection device 1 performs a failure recovery process such as separating and turning back a failure section. This prevents the system from going down in the entire network.

Referring to FIG. 1, there is shown a functional block diagram in an embodiment of the optical input fault detection device 1 applied to the optical node M shown in FIG. As shown in FIG. 1, the optical input failure detection device 1 includes an optical / electrical conversion unit 10, a bit error detection unit.
12, a bit error monitoring unit 14, a selector 16, an INH element 18, and an out-of-synchronization detecting unit 20.

The optical / electrical conversion unit 10 is a conversion unit that converts a frame synchronization signal and data input as optical signals from the transmission path 300 (FIG. 3) into electric signals. The conversion unit 10 is connected to one input terminal of the INH element 18 via the signal line 100,
A frame synchronization signal is output to this. The conversion unit 10 also
It is connected to a data processing unit (not shown) and a bit error detection unit 12 of the node M via a signal line 102, and outputs input data converted into an electric signal to these.

The bit error detection unit 12 is a data error detection unit that detects a bit error of input data. When the optical input level of the optical signal decreases, first, data input to the detection unit 12 becomes abnormal, and a bit error occurs.
The detecting unit 12 monitors such a bit error, and when detecting this error, the bit error monitoring unit 1 via the signal line 120.
Error notification is sent to 4.

The bit error monitoring unit 14 is a monitoring unit that monitors the output from the bit error detection unit 12. Bit error monitor 14
Outputs an “H” level OK signal to the input terminal A of the selector 16 via the signal line 140 in a normal state, and outputs an “L” level NG signal to the input terminal A of the selector 16 when an error notification is received.
Output to Once the error monitoring unit 14 receives the error notification, even if the error monitoring unit 14 does not receive the error notification,
No signal is output to the selector 16. That is, the monitoring unit 14
The OK signal is not output to the input terminal A of the selector 16 until the error notification is not received continuously for a predetermined time t.

The selector 16 is a selector that outputs one of the signals input to the two input terminals A and B from the output terminal Y according to the value input to the select terminal SEL. That is, the selector 16 outputs the “H” level signal of the input terminal B from the output terminal Y when receiving the “H” level signal from the out-of-synchronization detection unit 20 via the signal line 200,
When the signal of the "L" level is received from 20, the signal input to the input terminal A is output from the output terminal Y. The output terminal Y is connected to the other input terminal of the INH element 18 via the signal line 160.

The INH element 18 has one input terminal connected to the optical / electrical
The other input terminal is connected to the selector 16 and the selector
It is a suppression element that determines whether or not to output the frame synchronization signal to the out-of-synchronization detection unit 20 according to the value of the output signal from the 16. That is, the INH element 18 outputs “H” from the selector 16.
While receiving the level signal, the frame synchronization signal received from the optical / electrical conversion unit 10 is output to the out-of-synchronization detection unit 20 via the signal line 180. INH element 18 is also connected to selector 1
When the signal of “L” level is received from 6, no frame synchronization signal is output to the detection unit 20.

The out-of-synchronization detection unit 20 is a detection unit that determines whether the input frame synchronization signal is normal. That is, the out-of-synchronization detection unit 20 detects that the frame synchronization signal sent from the INH element 18 is out of synchronization when the optical input level is reduced.
An “L” level NG signal, that is, an optical input failure detection output is output via a signal line 200. If no out-of-synchronization is detected, an “H” level OK signal is output to signal line 200. These OK signals or NG signals are also input to the select terminal SEL of the selector 16. Note that the out-of-synchronization detection unit 20 outputs an NG signal even when the frame synchronization signal is not input from the INH element 18 because the synchronization signal cannot be detected. The out-of-synchronization of the frame synchronization signal usually occurs when the optical input level decreases, data becomes a bit error, and the optical input level further decreases.

FIG. 2 shows a waveform example of the light input level when the light input level is attenuated. In the figure, the light input attenuation level increases with the direction of the arrow. When the optical input level decreases and reaches the bit error reference value 400, a bit error occurs first. Optical communication is still possible when a bit error occurs. However, when the optical input level further decreases and reaches the out-of-synchronization reference value 450, the out-of-synchronization of the data frame occurs. At this point, two failures, that is, out-of-synchronization and a bit error are detected, and optical communication becomes substantially impossible. The failure detection device 1 in this embodiment does not output the optical input failure detection output until the synchronization is lost, and once the synchronization is lost, the optical input failure detection is continued until a bit error does not occur for a predetermined time. Output the output.

Next, the operation of this embodiment will be described in detail with reference to FIG. 1 and FIG. First, when an optical signal is input, this signal is converted into an electrical signal by the optical / electrical conversion unit 10,
The frame synchronization signal and data are extracted. The out-of-synchronization detection unit 20 constantly monitors the input frame synchronization signal for out-of-synchronism, and the input data is constantly monitored for bit errors by a bit error detection unit.

As shown in FIG. 2, when the optical input level decreases and reaches the bit error reference value 400, the bit error detection unit 12 detects the occurrence of a bit error and outputs the detection output to the bit error monitoring unit 14. At this point, since the frame synchronization has not been lost, the out-of-synchronization detection unit 20 does not output the optical input failure detection output. However, when the optical input level further decreases and reaches the out-of-sync reference value 450,
When the frame synchronization signal becomes abnormal, the out-of-synchronization detecting unit 20 detects the out-of-synchronization, and outputs an optical input failure detection output as an NG signal.

Since the optical input failure detection output is an "L" level signal, this output changes the select terminal SEL of the selector 16 to "L" and selects the input terminal A. At this time, since a bit error has occurred, the output of the bit error monitoring unit 14 is at the “L” level of the NG signal. Therefore, an “L” level signal is output from the output terminal Y of the selector 16, and this signal is input to the INH element 18. This allows
The frame synchronization signal is no longer input to the out-of-frame detection unit 20, and the optical input failure detection output is output as long as a bit error occurs. Therefore, even if the optical input level fluctuates near the boundary between the level where synchronization is lost and the level where synchronization is not generated (300 to 310), a stable optical input failure detection output is output.

After that, a failure recovery process is performed by some method, and when the optical input level returns to normal and stabilizes without a bit error for a certain period of time t or more (320 to 330), the output from the bit error monitoring unit 14 becomes " The signal becomes the "H" level OK signal.
As a result, the frame synchronization signal input to the element INH18 is sent to the out-of-synchronization detection unit 20. Since the frame synchronization signal at this time is normal, the out-of-synchronization detection unit 20 does not output the optical input failure detection output, and becomes an “H” level OK signal. Therefore, the select terminal SE of the selector section 16
L changes to the “H” level again, the input terminal B is selected, and the “H” level signal is output to the element INH18. Therefore, even if a bit error occurs again, an optical input failure detection output is not output until an out-of-synchronization failure occurs.

As described above, according to the present embodiment, the bit error monitoring unit 1
4, Loss-of-synchronization detector by selector 16 and element INH18
20 output controls are performed. Therefore, even if the optical input level fluctuates near the boundary between the level at which the synchronization is lost and the level at which the synchronization is not generated, a stable optical input failure detection output can be supplied to the optical node device.

In this embodiment, the optical input fault detecting device in the optical loop LAN to which the present invention is advantageously applied has been described, but the present invention is not particularly limited to this. That is, the present invention is also applicable to, for example, a wide area network (WAN), and the structure of the network may be a bus, a star, or a combination thereof.

(Effects of the Invention) As described above, according to the optical input failure detection device of the present invention, even if the input level fluctuates at the boundary point between the level at which data can be normally received and the abnormal level, that is, the level at which frame synchronization is lost. Thus, stable optical input failure detection output can be performed. Therefore, for example, optical loop LA
When a failure occurs in a network such as N, loopback processing and loop switching processing can be performed stably.
Therefore, even if a failure occurs due to a decrease in the optical input level due to, for example, deterioration of an optical fiber, a light emitting element, or the like, failure processing can be executed reliably, and a highly reliable optical communication system can be constructed.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an embodiment of an optical input failure detection device according to the present invention, FIG. 2 is a waveform diagram showing an example of an optical input level, and FIG. FIG. 1 is a system configuration diagram illustrating an example of a loop LAN system. Description of Signs of Main Part 1 Optical input fault detection device 10 Optical / electrical conversion unit 12 Bit error detection unit 14 Bit error monitoring unit 16 Selector 18 INH element 20 Loss of synchronization Detection unit

Claims (1)

(57) [Claims] 1. An optical input failure detection device provided in an optical node device for constructing an optical network and detecting an input failure of an optical signal received via a transmission line of the optical network. First detecting means for detecting a bit error of the detected optical signal, second detecting means for detecting a loss of synchronization of a synchronization signal included in the received optical signal, first detecting means and second detecting means When the second detecting means detects the loss of synchronization, the first detecting means
And control means for controlling the second detection means to output an out-of-synchronization until the bit error detection from the detection means is not detected continuously for a predetermined period of time.