JP2819601B2 - Failure diagnosis method for communication systems - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a failure diagnosis method for a communication system, and particularly to a communication system using an optical fiber, in a communication system using an optical fiber, not only a failure in a transceiver but also a failure in a network. The present invention relates to a failure diagnosis method for a communication system capable of diagnosing a failure of a communication system.

(Prior art) As is well known, IEEE802.3 / Ethernet
A terminal connected to the network with a transceiver interface according to the standard is configured to transmit and receive packet data to and from the network via the transceiver.

In a conventional communication system using a coaxial cable as a transmission medium of a network, when packet data is transmitted from a terminal, the packet data is transmitted to a transceiver through the cable and transmitted to another terminal via the network. Sent. In parallel with this, the packet data is transmitted from the transceiver to the network and, at the same time, sent back to the terminal that transmitted the packet data, and the terminal confirms this, so that the packet data is transmitted to the network normally. Confirm that it was sent to.

That is, the terminal determines the processing time in the terminal, the terminal,
The transmission packet data is returned during a time T (hereinafter, referred to as a carrier sense signal detection time) obtained by adding a predetermined margin time to the sum of the round trip propagation delay time between the transceivers and the processing time in the transceiver. If not, in other words, if the carrier sense signal is not detected, it is determined that there is an abnormality in the transmission of the packet data.

Now, a communication system using an optical fiber as a transmission medium in a network to which the transceiver is connected has been proposed. However, in the communication system, since the network is composed of optical fibers, when packet data is transmitted from the transceiver to the network, the packet data is not sent back to the terminal side. There is a problem that the packet data cannot be detected within the detection time T, and it cannot be determined whether or not the packet data has been transmitted normally.

Therefore, the present applicant has made an invention to solve this, and
Filed as 63-80037.

According to the present invention, a coaxial cable is used as a transmission medium by providing a switch for returning packet data in a transceiver to perform loopback in the transceiver and not to perform loopback in a network side device. The packet data is looped back in the same time as in the case, and the above problem is solved.

(Problem to be Solved by the Invention) In the communication system using the optical fiber, the terminal can detect the carrier sense signal within the carrier sense signal detection time T because loopback can be performed in the transceiver. It is possible to detect whether the packet data has been transmitted normally or not. That is, a fault in the transceiver can be detected.

However, there is a problem that no consideration is given to the detection of the failure of the network side device.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned problems and to provide a fault diagnosis system for a communication system capable of detecting faults in a network as well as faults in a transceiver.

(Means and Actions for Solving the Problems) According to the present invention, in order to achieve the above object, in a communication system using an optical fiber as a transmission medium, a first method for looping back data to a terminal side in a transceiver in a transceiver. Loop back means, mask means for masking data transmitted from the network side device via the optical fiber, and control means for controlling validity / invalidity of the first loop back means and the mask means. It is characterized in that a second loopback means for looping back data transmitted from the terminal is provided in the network side device.

According to the present invention, in the above configuration, the first loop-back means is effective at the time of data communication, the mask means is enabled at least at the time of returning the data, and the loop-back means is invalid at the time of fault diagnosis, and the mask means is effective. Disabled.

As a result, data communication between the terminals can be performed by a conventional method, and at the time of failure diagnosis, whether or not a failure has occurred in the network-side device can be detected by an operation from the terminal.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a block diagram of one embodiment of the present invention.

In the figure, reference numeral 1 denotes a terminal, which transmits packet data and receives data from another terminal. 2 is a transmission line, 3 is a reception line, 4 is the transmission line 2 and the reception line 3
Is connected via the transceiver. Reference numerals 5 and 6 denote optical fibers, and reference numeral 7 denotes a network device. The transceiver 4 is connected to the network device 7 via the optical fibers 5 and 6. As is well known, in the communication system having the above-described configuration, when performing long-distance transmission, the optical fibers 5 and 6 are extended to a length necessary for the long-distance transmission.

The transceiver 4 includes a transmission line receiver 11, a data detection unit 12, an idle signal generation unit 13, a transmission signal selection unit
14, an optical transmission unit 15, an optical reception unit 16, and a reception line driver 17
, An optical power detection unit 18, a return switch 19, an OR gate 20, a loopback changeover switch 21, and a reception data mask unit 22.

Further, the network-side device 7 includes an optical receiving unit 31, a data detecting unit 32, a transmission signal selecting unit 33, an optical transmitting unit 34, an idle signal generating unit 35, an optical power detecting unit 36, a signal cutting unit 37, a folding line 38.

Here, the transmission signal selection unit 14 of the transceiver 4
When packet data is not transmitted from the terminal 1 according to a signal from the data detection unit 12, the idle signal generation unit
The idle signal output from 13 is selected, and when there is the transmission packet data, the packet data is selected and sent to the optical transmission unit 15. Transmission signal selection unit 33 of network-side device 7
The same operation as that of the transmission signal selector 14 is performed.

The features of this embodiment are that a loopback changeover switch 21 and a reception data masking unit 22 are provided in the transceiver 4, and a return line 38 is provided in the network device 7. The loopback changeover switch 21 takes on two states, ON or OFF, based on a control signal sent from the terminal 1 via the control line 23.

The terminal 1 outputs a control signal for turning off the loop-back switch 21 when sending packet data to another terminal, that is, during a normal communication operation. As a result, the loop-back switch 21 is turned off, and for example, the H-level signal
19 and the received data masking unit 22. For this reason,
The return switch 19 is turned on, and the received data masking unit 22 masks the signal from the optical receiving unit 16 only while the signal c from the data detecting unit 12 is at the H level.

Conversely, when the terminal 1 performs a fault diagnosis of the communication system, the terminal 1 outputs a control signal for turning on the loopback switch 21. As a result, the loop-back switch 21 is turned on, for example, L
The level signal is output to the folding switch 19 and the reception data mask unit 22. Therefore, the folding switch 19
Is turned off, and the reception data masking unit 22
Is passed without masking.

In the communication system using the optical fiber having the above configuration, when the packet data a is output from the terminal 1, the packet data a is input to the transceiver 4 through the transmission line 2. In the transceiver 4, the transmission line receiver 11 first receives the packet data, and then the packet data b
Is sent to the transmission signal selection unit 14.

The transmission signal selection unit 14 selects the packet data b when the data detection unit 12 detects the packet data output from the terminal 1, and selects the idle signal p when no packet data is output. The folding switch 19 is turned on when the optical power detection unit 18 detects a signal, and turned off when no signal is detected.

The signal cut unit 37 in the network device 7
When the optical power detection unit 36 is detecting a signal, the signal is turned on and the input signal is passed, and when the signal is not detected, the signal is turned off and the input signal is cut off.

Next, the operation of the present embodiment will be described with reference to the waveform diagram of FIG. The reference numerals in FIG. 2 show the waveform diagrams of the signals having the same reference numerals in FIG. Further, this waveform diagram shows only an example, and the present invention is not limited to this.

First, an operation of the present embodiment when the terminal 1 transmits packet data to another terminal, that is, an ordinary communication operation, will be described. At this time, as described above, the return switch 19 is on, and the reception data masking section 22 is in the mask state when the output signal c of the data detection section 12 is at the H level, and is in the non-mask state when the output signal c is at the L level.

As shown in FIG. 2, the idle signal generator 13 in the transceiver 4 and the idle signal generator 35 in the network-side device 7 always output an idle signal d composed of a pulse train having a constant period. .

Until the time t1 when the packet data a is output from the terminal 1, the data detection unit 12 does not detect the packet data, so the output signal c of the data detection unit 12 is at the L level.
Therefore, the transmission signal selection unit 14 selects the idle signal d. Therefore, the output signal e from the transmission signal selector 14 becomes the idle signal d.

From time t1 to time t2, the terminal 1 sends out the packet data a, so that the data detection unit 12 detects the packet data. Therefore, the output signal c of the data detection unit 12 becomes H level, and the transmission signal selection unit 14 selects the packet data b. Therefore, the output signal e from the transmission signal selector 14 becomes the packet data b.

After the time t2, the transmission of the packet data a from the terminal 1 is stopped, so that it becomes the same as before the time t1. The data detector 12 is configured to output an H level signal for a predetermined time even after the detection of the packet data b is completed.

The signal e selected by the transmission signal selector 14 is an optical transmitter
The optical signal is converted into an optical signal and received by the optical receiver 31 through the optical fiber 5. The optical receiving unit 31 converts the optical signal into an electric signal, and then transmits the waveform-shaped signal f to another terminal.

The packet data b or the idle signal d
The time difference shown in the waveform between the signal and the signal e indicates the delay time. Hereinafter, the same applies to other waveforms.

The optical receiver 31 outputs, for example, a signal obtained by integrating the input signal to the optical power detector 36. Therefore,
When the optical fiber 5 is normal without disconnection or the like, since an idle signal or packet data is always input to the optical receiving unit 31, the signal g output from the optical receiving unit 31 is output.
Exceeds the reference level, and the output h of the optical power detector 36
Are always at the H level. For this reason, the signal cut section
37 is in the ON state.

Further, the signal f passes through the return line 38 and is sent to the data detecting section.
32 and a transmission signal selection unit 33. The data detector
32 detects the packet data from the terminal 1 or the packet data sent from another terminal, the transmission signal selection unit 33 selects the signal on the return line 38,
Otherwise, it operates to select the idle signal output from the idle signal generation unit 35.

Now, assuming that the packet data output from the terminal 1 is on the return line 38, the transmission signal selector 33 selects the packet data on the return line 38. The packet data passes through the signal cut section 37, becomes a signal j, and is converted into an optical signal by the optical transmission section.

On the other hand, if no packet data is input from the terminal 1 or another terminal to the network-side device 7, the transmission signal selection unit 33 selects and outputs the idle signal i output from the idle signal generation unit 35. The transmission signal selection unit 33
The idle signal output from is passed through the signal cut section 37,
The light is sent to the optical transmitter.

The optical signal of the packet data or the idle signal sent from the optical transmitting unit 34 enters the optical receiving unit 16 through the optical fiber 6 and is converted into an electric signal. The optical receiving unit 16 outputs an electric signal q of packet data or an idle signal to the reception data masking unit 22, and outputs a signal obtained by integrating the packet data or the idle signal to the optical power detecting unit 18. Output.

The optical power detector 18 compares the level of the signal from the optical receiver 16 with a reference level. When the optical fiber 6 is normal and the packet data or the idle signal is returned, the input signal level of the optical power detector 18 is higher than the reference level. The level of p becomes H level, and the return switch 19 is turned on.

Therefore, the packet data b output from the transmission line receiver 11 passes through the return switch 19, and the signal r passing through the return switch 19 is input to one input terminal of the OR gate 20. On the other hand, since the reception data masking section 22 masks the input signal, the output thereof is at the L level while the signal c is at the H level.

For this reason, the output signal s of the OR gate 20 is a signal obtained by performing an OR operation on the packet data r input through the folding switch 19 and the output signal q 'of the reception data masking unit 22, that is, the L level signal. Becomes

The signal s enters the reception line 3 via the reception line driver 17 and is further sent to the terminal 1. When the terminal 1 confirms that the received signal e includes the packet data transmitted by itself, the terminal 1 recognizes that the transmission of the packet data is successful.

As described above, according to the present embodiment, the packet data transmitted from the terminal 1 is turned back in the transceiver 4 without passing through the optical fibers 5 and 6, and is returned to the terminal 1 again. 4 can be detected.

Further, the carrier sense signal detection time T is independent of the lengths of the optical fibers 5 and 6. Therefore, a terminal similar to that used in a conventional communication system using a coaxial cable can be used for a communication system using an optical fiber as a transmission medium.

Next, an operation when the terminal 1 performs a failure diagnosis of the communication system will be described. At this time, as described above, the folding switch 19 is off, and the reception data masking unit 22 cancels the masking operation.

For this reason, as shown in FIG. 2 (b), the signal q output from the optical
It appears at its output as signal q 'through
It is sent to the reception line driver 17 through 20. The reception line driver 17 sends the signal q 'to the terminal 1 via the reception line 3. Upon receiving the signal q 'representing the packet data, the terminal 1 determines that the network side device of the communication system is normal. On the other hand, if the terminal 1 does not receive the signal q 'representing the packet data, it determines that the network side device of the communication system is abnormal.

As described above, according to the present embodiment, the packet data transmitted by the terminal 1 can be looped back by the network-side device, so that an abnormality of the network-side device can be detected.

According to the present embodiment, the optical power detecting unit 36 and the signal cutting unit 37 are provided in the
Since the optical power detector 18 is provided inside the optical fiber 5
If there is a failure or abnormality in the optical link unit composed of the optical transmitting unit 15 and the optical receiving unit 31 connected to both ends of the optical link, the signal cut unit 37 is turned off. As a result, the output signal i of the signal cut section 37 becomes no signal, the level of the output p of the optical power detection section 18 of the transceiver 4 becomes L level, and the return switch 19 is turned off. As a result, the packet data b cannot pass through the switch 19, and the terminal 1 cannot recognize the packet data within the carrier sense signal detection time T, and determines that the transmission has failed. When any abnormality occurs in the optical link section including the optical fiber 6, the return switch 19 is turned off by the same operation as described above, and it is determined that transmission has failed.

Next, a specific example of the circuit of the transceiver 4 is shown in FIG. The same reference numerals as those in FIG. 1 indicate the same or equivalent components.

In FIG. 3, the data detecting unit 12 includes a buffer 12a
And a capacitor 12b and a resistor 12c for smoothing the packet data output from the buffer 12a, and a comparator 12d. A reference level voltage is applied to one input terminal of the comparator 12d.

The idle signal generation unit 13 includes a crystal oscillator 13a, a delay circuit 13b, an inverter 13c, and an AND gate 1 that receives an output of the crystal oscillator 13a and an output of the inverter 13c.
3d.

The transmission signal selection unit 14 includes an inverter 14a and first and second
The AND gates 14b and 14c and the OR gate 14d are provided. When the output signal c from the data detector 12 is at the H level, the packet data b is selected, and when the output signal c is at the L level, the idle signal d is selected.

The optical transmission unit 15 includes a buffer 15a, a photodiode 15b,
It is composed of a driving transistor 15c and a resistor 15d, and the input signal is converted into an optical signal by the photodiode 15b.

The light receiving unit 16 is a diode 16a that converts light into an electric signal.
ATC (Auto Threshol) including an amplifier including a resistor 16b and an operational amplifier 16c, and an amplifier including an operational amplifier 16d and a capacitor 16e.
d Contror)) circuit and a comparison 16f.
The output of the ATC circuit has a magnitude proportional to the received optical power.

The optical power detection unit 18 is composed of a comparator. A voltage of a reference level is applied to one input terminal, and the output of the ATC circuit is input to the other input terminal. The folding switch 19 is formed of an AND gate.

Further, the reception data mask unit 22 includes an AND gate 22a and a gate 22b.

Next, a specific example of the network side device 7 is shown in FIG. The same reference numerals as those in FIG. 1 indicate the same or equivalent components.

The light receiving unit 31 has the same configuration as the light receiving unit 16 in FIG.
The power detector 36 is composed of a comparator similarly to the power detector 18 of FIG.

The data detection unit 32 has the same configuration as the data detection unit 12 of FIG. 3, and the transmission signal selection unit 33, the idle signal generation unit 35, and the optical transmission unit 34 are respectively configured by the transmission signal selection unit 1 of FIG.
4. It is formed by the same configuration as the idle signal generation unit 13 and the optical transmission unit 15. The signal cut section 37 is constituted by an AND gate.

It should be noted that the above specific configuration is merely an example, and it goes without saying that various changes can be made without departing from the spirit of the present invention, and it is clear that these are included in the scope of the present invention.

(Effect of the Invention) According to the present invention, a means for returning packet data is provided in the transceiver and the network side device, and a means for selecting the returned packet data is provided in the transceiver. Various effects can be expected.

(1) When a communication system is laid or a failure occurs, the network of the communication system can be diagnosed from the terminal side.

(2) Further, when a failure is found at the time of the diagnosis, it is possible to easily determine whether the failure has occurred in the transceiver or the network device.

(3) The network-side device is usually installed at a long distance from the terminal, but according to the present invention, even if the worker does not bother to go to the installation location of the network-side device, the diagnosis can be made. It can be performed.

(4) The terminal can detect the folded packet data, that is, the carrier sense signal, within the carrier sense signal detection time when a conventional coaxial cable is used, so that the terminal can be used in a communication system using an optical fiber as a transmission medium. A terminal used in a communication system using a coaxial cable as a transmission medium can be used as it is.

(5) It can be realized by using a simple circuit configuration and inexpensive means.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a timing chart of signals of main parts of FIG. 1, FIG. 3 is a circuit diagram showing a specific example of the transceiver of FIG. FIG. 4 is a circuit diagram showing a specific example of the network-side device of FIG. 1 ... Terminal 2 ... Transmission line 3 ... Reception line 4 ... Transceiver 5,6 ... Optical fiber 7 ... Network device 19 ... Folding switch 20 ... Or gate 21 ...
Loopback changeover switch, 22 ... Reception data mask section, 23 ... Control line, 36 ... Optical power detection section, 37 ... Signal cut section, 38 ... Return line

Claims (3)

(57) [Claims] In a fault diagnosis system for a communication system in which a transceiver and a network-side device are connected using an optical fiber and data transmitted from a terminal is transmitted to another terminal, the transceiver includes: First loopback means for looping back data transmitted from the terminal to the terminal, and masking means for masking the data provided on a path for transmitting data sent from the network side device to the terminal; During data communication, the loopback means is enabled to loop back data,
The masking means is enabled at least at the time of returning the data to mask the data, and at the time of fault diagnosis, the loopback means is disabled to prevent the loopback of the data, and the masking means is disabled so that the data is not masked. And a control means for controlling the failure, and at least a second loopback means is provided in the network device. 2. The on / off control of the first loop-back means in the transceiver according to a power level of an optical signal input to the transceiver via the optical fiber from the network side device. 2. A fault diagnosis system for a communication system according to claim 1, further comprising means for controlling. 3. A means for detecting the power level of an optical signal input from the transceiver to the network-side device, and when the power level of the optical signal is equal to or lower than a predetermined level, a signal from the second loopback means is provided. 2. A fault diagnosis system for a communication system according to claim 1, further comprising means for cutting a signal including data transmitted from said network side device to said transceiver.