JP3091336B2 - Transmission line control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line control system for a local area network (LAN) in which nodes are connected by a double optical loop, and more particularly, to a method for preventing loop-back control from increasing unnecessarily. It is composed.

[0002]

2. Description of the Related Art A conventional duplex optical loop LAN in which nodes are connected by an optical fiber is, as shown in FIG.
Central node device (MN; having an AN loop control function)
A right system loop 2 and a left system loop which include a master node 1 and a remote node device (SN; slave node) 10 to which a user terminal is connected, and transmit information between the node devices in mutually opposite directions. 3 and a double optical loop.

Each of the node devices includes an optical receiver RX13 for converting a received optical signal into an electric signal and an optical fiber for converting an electric signal into an optical signal for each of the right system loop 2 and the left system loop 3. And an optical transmission unit TX12 for transmitting the
Further, a monitoring control device 11 for monitoring and controlling the operation state of each of these units is provided.

As shown in FIG. 5, the optical transmitter TX12 includes a laser 20 for emitting an optical signal, a laser drive circuit 21 for supplying a drive current to the laser 20, and a laser for monitoring the emission of the laser 20. An automatic optical output power control unit 22 that controls the drive circuit 21 and a monitoring control device interface unit 23 that exchanges signals with the monitoring control device 11 are provided.

[0005] In a normal state, the dual optical loop LAN uses one of the left optical loops 3 of the dual optical loop as an operating system and the right optical loop 2 as a standby system in preparation for a failure. Therefore, the node device 10 at this time
Receives a signal from the optical receiver RX13 connected to the left loop 3 and transmits a signal from the optical transmitter TX12 connected to the left loop 3.

When a failure occurs in the laser 20 of the LAN node device 10 and the light emission output is reduced, one loop is used as a bypass for the other loop in order to secure a transmission line that bypasses the failure location. Transmission path control called loop back is performed in the following procedure.

Now, it is assumed that the laser 20 of the optical transmitter TX12 connected to the left loop 3 of the node device a becomes abnormal and the light emission output decreases. The automatic optical output power control unit 22 monitoring the laser emission detects this abnormality, and outputs alarm information via the monitoring control device interface unit 23 to the monitoring control device 11.
Output to

[0008] The supervisory control device 11 of the node device a receiving the alarm information notifies the center node 1 of the laser failure information using the right system loop 2. The center node 1 having received the notification determines the node device (ie, the node device a and the node device b) to execute the loop back, and sends the loop back instruction information to the node device. .

In the node device a receiving the loop back instruction, the supervisory control device 11 controls the reception of the signal by the left loop 3
The optical receiving unit RX12 and the optical transmitting unit TX13 are controlled so that signal transmission is performed to the right loop 2.

On the other hand, in the node device b, the monitoring control device 11
However, the optical receiver RX12 receives the signal from the right loop 2 and transmits the signal to the left loop 3.
And the optical transmitter TX13.

As a result, the optical transmission unit TX12 in which a failure has occurred
A loop-shaped transmission path that does not pass through is formed.

[0012]

However, the conventional loop-back control method has the following problems.

The automatic optical output power control unit 22 of each node device 10
Then, the light emission state of the laser 20 of the optical transmission unit TX12 is
Detected by a diode or the like, and when the detection value falls below the alarm threshold, the warning information is output as that the laser 20 has deteriorated, and based on this warning information, loop-back in the corresponding node device starts. Is done. However, the characteristics of the laser vary, and the optical output of the laser tends to decrease as the temperature rises. Therefore, it is difficult to uniformly set the standard for the state of deterioration of the laser.

In the conventional loop-back control method, the threshold value at which alarm information is issued is set higher in consideration of safety. Therefore, although the transmission and reception of optical signals are not particularly hindered, the laser is deteriorated. In many cases, a loop back is started, and the number of loop backs is increased, and there is a problem that the frequency of maintenance and parts replacement is increased.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. By improving the reliability of the determination of deterioration of an optical transmitter with respect to a laser, the efficiency of use of optical components such as a laser is increased, and the number of maintenance steps is reduced. It is an object of the present invention to provide a transmission path control method for a duplex optical loop LAN that can be reduced.

[0016]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a transmission path control system for a duplicated optical loop LAN in which a plurality of node devices are connected in a ring by two optical fibers transmitting signals in mutually opposite directions. When the deterioration of the light emitting element in the optical transmission unit of the node device is detected, the control of the transmission path is executed only when the code error of the signal transmitted from the light emitting element is also detected.

The signal transmission between the node devices is performed by SDH.
(Synchronous Digital Hierarchy) This is performed by a frame of a transmission system, a code error of the signal is detected by using a code of an overhead part of the frame, and information of a detection result is incorporated in the overhead part to transmit a signal from the node device. I'm trying to tell.

[0018]

Therefore, even if a decrease in the light emission output of the light emitting element of the light transmitting unit is detected, if the adjacent node device that has received the signal transmitted by this light emitting element does not detect a code error of the received signal, the signal is output. The loop-back control is not performed assuming that there is no problem in transmission / reception.

When the adjacent node device detects a code error in the received signal, the detected information is transmitted to the signal source node device, and a procedure for transition to loop back control is adopted.

When an SDH frame is used for signal transmission, it is possible to detect a code error in a received signal and transmit a detection result to a signal transmission source by using an overhead portion of the frame. .

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) As shown in FIG.
And an optical transmitter TX12 for converting an electric signal into an optical signal and transmitting the same, and an optical receiver RX13 for converting a received optical signal into an electric signal. A detection unit 14 for detecting a code error, further comprising an interface unit 15 for transmitting and receiving data to and from a terminal connected to the node device, and a monitoring control unit 11 for monitoring and controlling the operation state of each unit. .

The optical transmitter TX12 has the same configuration (FIG. 5) as the conventional one and operates in the same manner.

Under the control of the supervisory control device 11, the interface unit 15 transmits data to the same loop as the signal receiving loop, or transmits data to a different loop from the signal receiving loop. Execute

In the optical transmitter TX12, the laser used
When the light emission output of 20 falls below the threshold value, the automatic light output power control unit 22 detects this, and outputs alarm information (LD state signal) to the monitoring control device 11 via the monitoring control device interface unit 23.

Further, the code error detecting section 14 is provided with an optical receiving section RX.
When detecting an error in the signal received by 13, it transmits code error information to the supervisory control device 11. Supervisory control device receiving this
11 is for the adjacent node device 10 that has output the signal,
Transmit far end block error alert information (FEBE).

Now, it is assumed that the monitoring control device 11 of the node device 10 has received alarm information indicating a laser abnormality from the optical transmission unit TX12 connected to the left system loop 3. At this time, the monitoring controller 11 checks whether FEBE is sent from an adjacent node device located downstream of the left loop 3. If this FEBE is not sent, it is determined that the laser abnormality is in a state where the output is reduced so as not to affect the receiving side, and no request for loop back control is made.

When the FEBE is sent from the adjacent node device, it is determined that the laser is in a fatally degraded state, and the monitoring control device 11 uses the right loop 2 to send the FEBE to the center node. Outputs information requesting loop-back control. The center node receiving this information determines the node device to execute the loop back, and sends the loop back instruction information to the node device.

In the node device that has received the loop back instruction, the supervisory control device 11 controls the interface 15 and
Perform loop back.

As described above, in the transmission line control system of the embodiment,
Based on an alarm indicating a laser emission abnormality and a FEBE indicating a code error of an optical signal output by the laser,
20 states are determined, and whether or not to perform loop control is determined. FIG. 3A shows the relationship between these two signals and the execution of the loop control, and FIG.
It is described in (b).

As shown in FIG. 3, when both (1) a laser abnormality alarm and FEBE are output, loop back is executed, and (2) a laser abnormality alarm is output. , When the FEBE warning is not output,
Although the output of the laser is low, the loop back is not performed because it is a minor failure. (3) When the laser abnormality alarm is not output and only FEBE is output, transmission between the node devices is performed. Is normal, so loop back is not performed. (4) Laser abnormal alarm and FEBE
When both are not output, it is a normal state,
Does not loop back.

As described above, according to the transmission path control method of the present invention, a fatal fault or a minor fault is classified according to the manner in which alarm information is output, and only when a fatal fault occurs. Loop back control is executed to prevent the number of loop back times from increasing unnecessarily.

(Second Embodiment) In the second embodiment, when the transmission path control system of the first embodiment is executed, optical transmission between node devices is performed by applying the SDH (synchronous digital hierarchy) transmission system. I do.

As shown in FIG. 4, the SDH frame is
VC (virtual container) frame (a) is STM
(Synchronous transport module) It is multiplexed on the frame (b). The SDH frame structure is defined by international standards, and the overhead information included in the VC POH (path overhead) and the STM SOH (section overhead) is also standardized, but is partially undefined. Area or an area that can be used according to the original specifications (POH B3 or SOH B2
Etc.) are left.

In the transmission line control system of the second embodiment, the SOH
Using such a part (B2), information on a code error detected from a received signal is transmitted to an adjacent node device, and if necessary, failure occurrence information is transmitted to another node through a loop in which no failure has occurred. Tell

As shown in FIG. 2, a node device that implements this transmission path control system includes an optical transmitting unit TX12 and an optical receiving unit R12.
X13 and a monitoring control device 11, and the optical transmission unit TX12
An SOH generating circuit 16 for generating section overhead information, and an electro-optical converter 18 for converting an electric signal into an optical signal
The optical receiver RX13 includes an opto-electrical converter 19 for converting an optical signal into an electric signal, and an SOH termination circuit 17 for extracting section overhead information (in FIG. 4, , Half of a node device and half of an adjacent node device connected to the node device via an optical fiber).

Now, the left system loop 3 is used as an operation system transmission line,
It is assumed that a signal is transmitted by an SDH frame. When an abnormality occurs in the laser emission of the optical transmitter TX12 that is outputting an optical signal to the left loop 3, information on abnormality detection is transmitted from the electro-optical converter 18 to the monitoring and control device 11.

On the other hand, the optical signal output from the optical transmitting unit TX12 is received by the optical receiving unit RX13 of the adjacent node device, and is converted by the photoelectric converter 19 into an electric signal. The SOH terminating circuit 17 extracts section overhead information from this signal and sends it to the supervisory control device 11.

The supervisory control device 11 detects a code error using BIP (Bit Interleaved Parity) for monitoring a transmission line error included in the section overhead information. The code error detection information is sent to the SOH generation circuit 16 of the optical transmission unit TX12 that outputs an optical signal to the system loop 2.

The SOH generating circuit 16 converts this information into a predetermined byte signal, takes it into the section overhead information of the SDH frame, and outputs it to the electro-optical converter 18 together with the transmission data. The converter 18 converts this signal into an optical signal and transmits it to the adjacent node device through the right system loop 2.

The code error detection information sent to the optical receiver RX13 of the adjacent node device is taken out by the SOH termination circuit 17 and sent to the supervisory control device 11. As a result, the supervisory control device 11 recognizes that the signal output from the left loop 3 indicates an abnormal reception on the adjacent node side.

As described above, the SOH termination circuit 17 realizes the function of the code error detector 14 in FIG.

The subsequent operation of the monitoring control device 11 having received the laser abnormality detection information and the code error detection information is as follows.
There is no difference from the case of the embodiment. Also, when only one of the information is received, according to the description of FIG.
No transition to loop back is performed.

In the transmission line control system of the second embodiment, S
Since the DH transmission method is applied to the duplex optical loop LAN, a miniaturized peripheral circuit developed for SDH can be used for this LAN.

In each of the embodiments, the description has been given of the case where the loop back control of the transmission line is performed in response to the fault. However, the transmission line control is not limited to this, and the transmission line of the operation system is set to the left. It is also possible to cope with this by switching the loop from the system loop to the right system loop.

Further, the transmission path control method of the present invention is not limited to a network in which a center node apparatus issues a transmission path control instruction in a centralized manner. The present invention can also be applied to a network configured to switch.

[0046]

As is apparent from the above description of the embodiment, in the transmission path control system of the present invention, when the light emission amount of the laser of the optical transmission unit is reduced, the signal transmitted from the optical transmission unit is encoded. The level of the failure in the optical transmission unit is determined based on whether or not there is an error, and the transition to the loop-back control is performed only when the failure is severe. Therefore, the degree of transition to loop-back is reduced as compared with the conventional transmission path control method, and accordingly, maintenance work is reduced and the utilization rate of parts is increased.

When the SDH transmission method is applied to a duplex optical loop LAN, a small circuit or an LSI developed for SDH can be used as a circuit incorporated in the node device. And cost reduction.

[Brief description of the drawings]

FIG. 1 is a block diagram of a node device that implements a transmission line control method according to a first embodiment of the present invention;

FIG. 2 is a block diagram of a node device that implements a transmission path control method according to a second embodiment of the present invention;

FIG. 3 is a diagram showing a relationship between an alarm and a transmission line control (a) and a relationship between an alarm and a failure category (b) in the transmission line control system of the present invention.
Figure showing

FIG. 4 is a structural diagram of an SDH frame used in the transmission path control system according to the second embodiment;

FIG. 5 is a block diagram illustrating a configuration of an optical transmission unit of a conventional node device.

FIG. 6 is a block diagram showing a configuration of a conventional duplex optical loop LAN.

[Explanation of symbols]

 Reference Signs List 1 center node device 10 node device 2 right system loop 3 left system loop 11 supervisory control device 12 optical transmission unit 13 optical reception unit 14 code error detection unit 15 transmission / reception data interface unit 16 SOH generation circuit 17 SOH termination circuit 18 electric light Converter 19 Opto-electric converter 20 Laser 21 Laser drive circuit 22 Automatic optical output power control unit 23 Monitoring and control device interface unit

Continuation of front page (72) Inventor Hiroyuki Nishi 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture Inside Matsushita Communication Industrial Co., Ltd. (72) Inventor Akira Sakai 4-chome, Tsunashima Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture No. 1 Matsushita Communication Industrial Co., Ltd. (56) References JP-A-56-93443 (JP, A) JP-A-62-237821 (JP, A) JP-A-2-155323 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) H04L 12/437 H04B 10/20

Claims (2)

(57) [Claims] 1. A transmission path control method for a duplicated optical loop LAN in which a plurality of node devices are connected in a ring by two optical fibers for transmitting signals in mutually opposite directions, wherein a light emitting element in an optical transmission unit of the node device is provided. A transmission path control method that executes control of the transmission path only when a code error of a signal transmitted from the light emitting element is detected when deterioration of the transmission path is detected. 2. The signal transmission between the node devices is performed by SDH.
(Synchronous Digital Hierarchy) Transmission is performed using a frame of a transmission system, a code error of the signal is detected by using a code of an overhead part of the frame, information of a detection result is incorporated in the overhead part, and a signal transmission source node is used. The transmission path control method according to claim 1, wherein the transmission is performed to a device.