JPH04137841A - Optical input fault detector - Google Patents

Abstract

PURPOSE:To output an optical input fault detection stably by outputting the optical input fault detection output for a prescribed time when a bit error is not detected. CONSTITUTION:When an optical input level is decreased, a bit error detection section 12 detects the occurrence of a bit error. When the optical input level is decreased more, an out of synchronism detection section 27 detects out of synchronism and an optical input fault detection output is outputted. An input terminal A of a selector 16 is selected by the output, an L level signal is outputted from an output terminal Y and a frame synchronizing signal is not inputted to a frame out of synchronism detection section 27 by an INH element 18. Then the optical input level is restored to the normal level and no bit error takes place consecutively for a prescribed time or over stably, then an output from a monitor section 14 goes to an H level. Thus, even when the input level is fluctuated at a level at which frame out of synchronism takes place, the stable optical input fault detection output is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is an optical input failure detection device, particularly an optical input failure detection device that is advantageously applied to optical nodes constituting a network such as an optical loop LAN (Local Area Nettyork). Regarding a detection device.

(Prior Art) Conventionally, optical input failures in optical loop LANs have been detected by detecting bit errors in data due to complete interruption of optical input or reduction in optical input level, and detecting out-of-synchronization of data frames. Each optical notebook making up the optical loop LAN is provided with an optical input failure detection device that detects such optical input failures. When the optical node receives the optical input failure detection output from the inspection device, it automatically switches or loops back the optical loop system to deal with such failures.

(Problem to be solved by the invention) However, in such conventional technology, optical loop LAN
In the event of an input signal failure, there are the following problems when automatically performing system switching or loopback of optical loops to deal with the failure.

That is, a complete input disconnection failure may be due to a failure in the transmitting station or a disconnection in the optical fiber.

In this case, since no light is input to the receiving station, the optical input failure detection output from the failure detection device is stable.

Therefore, in such a case, the troubleshooting operation is stable, and communication after troubleshooting can be performed normally by troubleshooting.

However, if the optical input level decreases due to deterioration of the light emitting element or optical fiber on the transmitting side, for example, the optical input becomes unstable. If the optical input level at this time is completely abnormal, it is possible to perform the same troubleshooting action as when optical input is cut off, but the optical input level will fluctuate near the boundary between the level at which data can be received normally and the abnormal level. If so, the optical input failure detection output will also fluctuate between normal and abnormal, resulting in an unstable output. For this reason, in node equipment that automatically performs troubleshooting operations based on the optical input fault detection output from the fault detection device, normal operation and abnormal operation are repeated alternately, resulting in an unstable optical loop operation. Therefore, there was a drawback that stable communication was not possible.

The present invention eliminates these drawbacks of the prior art and makes it possible to accurately determine normal operation and abnormal operation even when the optical input level decreases and fluctuates near the boundary between normal and abnormal levels. It is an object of the present invention to provide an optical input failure detection device that can stabilize the optical input failure detection output and 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 that constructs an optical network, and detects an input failure of an optical signal received via a transmission path of the optical network. The optical input failure detection device includes: a first detection means for detecting a bit error in a received optical signal; a second detection means for detecting an out-of-synchronization of a synchronization signal included in the received optical signal;
It is connected to the output sides of the first detection means and the second detection means, and when the second detection means detects an out-of-synchronization.

and control means for controlling the second detection means to output an out-of-synchronization signal until the bit error detection from the first detection means continues for a predetermined period of time and is no longer detected.

(Function) According to the present invention, when the first detection means detects a bit error and the second detection means detects an out-of-synchronization, the control means detects a bit error for a predetermined period of time after no longer detecting a bit error. During this period, the second detection means is controlled to output an optical input failure detection output.

(Example) Next, an example of the 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 is composed of a plurality of nodes M (M1 to Mfi) that perform data processing, and these nodes M are connected to adjacent nodes M in a ring shape by a transmission path 300 such as an optical fiber.

The nodes M are optical terminal devices that use light as a means of transmitting information and mutually transmit and receive data in accordance with frame synchronization. The node M is also provided with an optical input failure detection device 1 (FIG. 1) that detects an optical input failure due to a failure in the node M on the transmitting station side or a transmission line. When the failure detection device 1 detects an optical input failure, the notebook M performs failure recovery processing such as, for example, separating the failed section and turning back. This prevents the entire network from going down.

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

The optical/electrical converter 10 is a converter that converts a frame synchronization signal and data input as optical signals from the transmission path 300 (FIG. 3) into electrical signals.

The conversion unit 10 is connected to one input terminal of the INH element 18 via a signal line 100, and outputs a frame synchronization signal thereto. The conversion unit 10 is also 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 electrical signal to these.

The bit error detection unit 12 is a data error detection unit that detects bit errors in input data.

When the optical input level of the optical signal decreases, the data input to this detection section 12 first becomes abnormal and a bit error occurs. The detection section 12 monitors such bit errors, and when detecting this error, notifies the bit error monitoring section 14 of the error via the signal line 120.

The bit error monitoring unit 14 is a monitoring unit that monitors the output from the bit error detection unit 12. The bit error monitoring unit 14 outputs an OK signal line 1 which is at “H” level during normal operation.
40 to the input terminal A of the selector 16, and when an error notification is received, the NG signal of "L" level is output to the selector 1.
Output to input terminal A of 6. The error monitoring unit 14 also
- Once an error notification is received, the signal is not immediately output to the OK double signal selector 16 even if the error notification is no longer received.

That is, the monitoring unit 14 does not output the OK signal to the input terminal A of the selector 16 until it no longer receives an error notification for a predetermined period of 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 a value manually input to the select terminal SEL. That is, when the selector 16 is receiving an "H" level signal from the out-of-synchronization detection section 20 via the signal line 200, it outputs an "H" level signal from the input terminal B from the output terminal Y, and the detection section 20 outputs the "H" level signal from the detection section 20. When a level signal is being received, the signal input to input terminal A is output from output terminal Y. The output terminal Y is connected to the INH element 1 via the signal line 160.
It is connected to the other input terminal of 8.

The INH element 18 has one input terminal connected to the optical/electrical converter 1
0 and the other input terminal are connected to the selector 16, and is a suppressing element that determines whether or not to output a frame synchronization signal to the out-of-synchronization detection section 20, depending on the value of the output signal from the selector 16. That is, while the INH element 18 is receiving a signal of the "■1" level from the selector 16, the INH element 18 does not perform optical/
The frame synchronization signal received from the electrical conversion section 10 is output to the desynchronization detection section 20 via the signal line 180. IN
The H element 18 also outputs a frame synchronization signal to the detection unit 20 when receiving an "L" level signal from the selector 16 9).

The out-of-synchronization detection unit 2o is a detection unit that determines whether the input frame synchronization signal is normal. In other words, the out-of-synchronization detection unit 20 detects that the INH element 1
When the frame synchronization signal sent from 8 becomes out of synchronization, an NG signal at the rlJ level, that is, an optical input failure detection output is outputted via the signal line 200. Furthermore, if no synchronization is detected, an "H" level OK signal is output to the signal line 200. These OK double signals or NG
The signal is also input to the select terminal SEL of the selector 16. Note that the out-of-synchronization detection section 20
Even when no frame synchronization signal is input, the NG signal is output because the synchronization signal cannot be detected. The out-of-synchronization of the frame synchronization signal usually occurs when the optical input level decreases and bit errors occur in data, and the optical input level further decreases.

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

When an out-of-synchronization occurs, an optical input failure detection output is output continuously for a predetermined period of time until no bit errors occur.

Next, details of the operation in this embodiment will be explained using FIG. 1 and FIG. 2. First, when an optical signal is input, this signal is converted into an electrical signal by the optical/electrical converter 10,
Frame synchronization signals and data are extracted. The input frame synchronization signal is constantly monitored for out-of-synchronization by the out-of-synchronization detection section 20, and the input data is always monitored for bit errors by the bit error detection section.

As shown in FIG. 2, when the optical input level decreases and reaches the bit error reference value 400, the bit error detection section 12
The occurrence of a bit error is detected and the detection output is output to the bit error monitoring section 14. Please note that frame synchronization has not been lost at this point.

The out-of-synchronization detection unit 20 does not output an optical input failure detection output. However, when the optical input level further decreases and reaches the out-of-synchronization reference value 450, the frame synchronization signal becomes abnormal, the out-of-synchronization detection section 20 detects the out-of-synchronization, and an optical input failure detection output that is an NG signal is output. Ru.

Since the optical input failure detection output is an "L" level signal,
Due to this output, the select terminal SEL of the selector 16 becomes "L" and the input terminal A is selected. At this time, since a bit error has occurred, the bit error monitoring unit 14
The output is 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. As a result, the frame synchronization signal is no longer input to the frame synchronization detection section 20, and as long as a bit error occurs, an optical input failure detection output is output. Therefore, even if the optical input level fluctuates near the boundary between the level that causes synchronization and the level that does not occur (300 to 31
0), a stable optical input failure detection output is output.

After that, the failure recovery process is performed by some method, and when the optical input level returns to normal and stabilizes without any bit errors for a certain period of time (320 to 330), the output from the bit error monitoring unit 14 becomes " This is an OK double signal of "H" level. As a result, the frame synchronization signal input to the element lNHI3 is sent to the out-of-synchronization detection section 20. Since the frame synchronization signal at this time is normal, the out-of-synchronization detection unit 20 does not output an optical input failure detection output.
This is an OK double signal of "H" level. Therefore, the select terminal SEL of the selector section 16 becomes "H" level again,
Input terminal B is selected and an "H" level signal is output to element IN818. Therefore, even if a bit error occurs again, the optical input failure detection output will not be output until an out-of-synchronization failure occurs.

As described above, according to this embodiment, the bit error monitoring unit 14
, selector 16 and element INH18 control the output of the out-of-synchronization detector 20. Therefore, even if the optical input level fluctuates near the boundary between the level that causes synchronization and the level that does not occur, it is possible to supply a stable optical input failure detection output to the optical node device.

Although this embodiment describes an optical input failure detection device in an optical loop LAN to which the present invention is advantageously applied, the present invention is not particularly limited to this. That is, the present invention is applicable to, for example, a wide area network (VAN), and the network structure may be bus-like, star-like, 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 received normally and the abnormal level, that is, at the level at which frame synchronization occurs, , stable optical input failure detection output can be performed.

Therefore, in the event of a failure in a network such as an optical loop LAN, loop bank 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 deterioration of an optical fiber or a light emitting element, for example, the failure can be reliably handled and a highly reliable optical communication system can be constructed.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing an embodiment of the 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. 3 is a system configuration diagram showing an example of an optical loop LAN system to which this embodiment is applied. Main part No. 4-11 Optical input failure detection device Optical/electric conversion section Bit error detection section Bit error monitoring section Selector INH element out-of-synchronization detection section

Claims (1)

[Scope of Claims] An optical input failure detection device that is disposed in an optical node device that constructs an optical network and detects an input failure of an optical signal received via a transmission path of the optical network, the device comprising: a first detection means for detecting a bit error in a received optical signal; a second detection means for detecting an out-of-synchronization of a synchronization signal included in the received optical signal; a first detection means and a second detection means; is connected to the output side of the means, and when the second detecting means detects an out-of-synchronization, the first
and a control means for controlling the second detection means to output an out-of-synchronization signal until the bit error detection from the second detection means is not detected continuously for a predetermined period of time.