JP3147150B2 - Overhead loopback test method and 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 synchronous digital hierarchy (SDH) signal transmission network and a North American SONET hierarchy (SONET) signal transmission network, which use surplus bits of their respective overhead portions to interrupt service of a communication line. This relates to the execution of a test by remote loopback without occurrence.

[0002]

2. Description of the Related Art Each of FIGS.
FIG. 3 is a diagram for explaining signal formats of a T hierarchy signal and an SDH signal.

In the SONET hierarchy signal format, as shown in FIG. 4A, a section overhead (SOH), a line overhead (LOH), and a path overhead (POH) are included as overhead portions added to a data payload portion. . FIG. 4B shows a specific configuration of the section overhead and the line overhead, and FIG.
Shows a specific configuration of the path overhead.

The section overhead is terminated and added or separated at the section layer, the line overhead is terminated and added or separated at the line layer, and the path overhead is terminated and added or separated at the path layer.

The definition of each byte shown in FIG. 4 is based on Bellcore GR-253-CORE i
ssue2, here, the following By
The bit of te is assigned as a remote loopback test data insertion byte.

SOH: RS Byte (GR-253)
LOH: RL Byte (defined as unused in GR-253-CORE) POH: Z3, Z4 Byte (defined as GR-253-CO)
In the SDH signal format, a regenerator section overhead (RSOH), a multiplex section, and an overhead section added to the data payload portion are defined as undefined user free use bits in the RE as shown in FIG. Overhead (MSOH) and path overhead (POH)
There is. Each of these is a section overhead in the SONET hierarchy signal format,
Similar to line overhead and path overhead. FIG. 5B shows a specific configuration of the regenerator section overhead, FIG. 5C shows a specific configuration of the multiplex section line overhead, and FIG. 5D shows a specific configuration of the path overhead. The configuration is shown.

[0007] The regenerator section overhead is added or separated at the relay section layer, the multiplex section overhead is added or separated at the multiplex section layer, and the path overhead is added or separated at the path layer.

The definition of each Byte shown in FIG. 5 is defined in ITU-TG. 708, G.R. 709 (03/9
This is specified in 3). Here, the following Byte bits are assigned as remote loopback test data insertion Byte.

RSOH: RS Byte (ITU-T
G. FIG. 708, G.R. MSOH: RL Byte (ITU-T G.70
8, G. POH: Z4 Byte (ITU-T G.708,
G. FIG. 709 is defined as an undefined user free use bit) The remote loopback method for the SDH signal and the SONET hierarchy signal has not been established yet. In the digital multiplexing apparatus that handles the above signals, it is stated that the loopback is related to the terminal loopback method of returning the signal from the higher-order group in the own station and the signal from the lower-order group in the own station. This is a facility loopback method. However, these do not specify a loopback execution request to the remote side, but define an execution function in the own station.

Therefore, a method of executing the remote loopback to confirm the line quality using the terminal loopback and the facility loopback actually described above will now be described.

In an apparatus for multiplexing an SDH signal and a SONET hierarchy signal, a remote login to a remote side is performed as a line confirmation method at the time of maintenance, and a terminal loopback or a facility loop is performed on a signal input from the central side. Back up and turn the signal back.

Further, after the service is stopped, the cable is physically unplugged, an error generation measuring device and an error detecting measuring device are connected to the digital device on the central side, and test data is sent from the central side to the remote side to transmit the test data on the remote side. A method has been used in which a signal is turned back and the quality of the transmission line between the central station and the remote station is confirmed by detecting the returned signal.

FIG. 3 shows OC- of SONET hierarchy.
FIG. 11 is a block diagram showing a configuration of a conventional example in which maintenance is performed by a loopback method in a communication network that multiplexes three signals into an OC-12 signal and transmits the multiplexed signal. In addition, OC-3
Regarding the signal and the OC-12 signal, they have the same format but different transmission speeds.
The OC-12 signal is transmitted at four times the transmission rate of the OC-3 signal.

In this conventional example, signal transmission is performed by a central OC-3 signal terminator 101 and a remote OC-3 signal terminator.
-3 between the signal termination device 108 and
C-3 signal termination device 101 and OC-3 signal termination device 10
8, which is used for transmission from the central side to the remote side and multiplexes four OC-3 signals 102 output from the OC-3 signal terminating device 101 into one OC-12 signal 110. 3 / OC-12 multiplexer (sending unit) 104 and OC-12 signal 110
Remote OC-3 /
The OC-12 separator (reception unit) 105 and the four OC-3 signals 111 used for transmission from the remote side to the central side and output from the OC-3 signal terminator 108 are converted into one OC-12 signal 110. Multiplexed remote OC-3
/ OC-12 multiplexer (sending unit) 114 and O
A central OC-3 / OC-12 separating device (receiving unit) 113 for separating the C-12 signal 110 into four OC-3 signals 112 is provided.

The OC-3 signal terminator 101, the central OC-3 / OC-12 multiplexer 104, and the central OC-3 / OC-12 demultiplexer 113 constitute a central station. Remote OC
-3 / OC-12 multiplexer 114 and remote OC
-3 / OC-12 separating device 105 constitutes a remote station. In addition, in order to confirm the transmission quality between the central station and the remote station, the central station has an OC-3 error occurrence measuring instrument 103 and an OC-3. -3 Error detection measuring instrument 109
And a remote OC-3 /
OC-12 multiplexer 114 and remote OC-3 / OC
An OC-3 signal terminal loopback transmission line 106 for short-circuiting a part of the -12 separation device 105 is provided.

Confirming the transmission quality between the central station and the remote station has been performed by the method described below.

First, a control unit (not shown) for controlling the operation of the central station performs a remote login to the remote station, and loops back an OC-3 signal terminal loop back to a line for checking the line quality. Transmission line 106
Make a request to form That is, a path for terminal loopback is formed at the remote station.

Next, the OC-3 error generator 103 is connected to the central OC-3 / OC-12 multiplexer 104, and the error detector 109 is connected to the central OC-3 / OC-12 multiplexer 104.
-3 / OC-12 Connected to the separation device 113. here,
By comparing the test data sent from the error occurrence measuring device 103 with the test data looped back by the remote station and detected by the error detecting measuring device 109, the error status of the signal is confirmed and the transmission quality is confirmed.

[0019]

The above-mentioned prior art has the following problems.

In the central station, it is necessary to connect a measuring device to both the transmitting side and the receiving side. In the line for checking the quality, the line between the OC-3 signal terminator and each multiplexer or demultiplexer must be disconnected. Therefore, there is a problem that the service is shut down during the quality check.

In order to check the quality of a line, an error detection measuring device and an error generating measuring device are required for one line, respectively. A number of measuring instruments are required. It takes time to maintain a plurality of lines by using a single set of measuring instruments, and it is expensive to maintain a plurality of lines by preparing a plurality of sets of measuring instruments. However, there is a problem that the cost for the operation increases.

The present invention has been made in view of the above-mentioned problems of the prior art, and can perform maintenance without interrupting a line service, and can measure an error detection and an error. The quality can be checked without the need for maintenance equipment, such as, and the overhead can be increased independently because maintenance can be performed independently for multiple lines by not using a measuring instrument. It is an object to implement a loopback method and method.

[0023]

SUMMARY OF THE INVENTION An overhead loopback test method according to the present invention uses an international standard synchronous hierarchy (SDH) signal for performing digital communication transmission or a hierarchy signal having an overhead section such as the North American SONET format. This is a loopback test method in a system in which transmission is performed between a synchronous digital device on a central side and a remote side, and a signal inserted into a surplus bit of an overhead portion of a transmission signal on a remote side is a signal overhead portion. And transmits the test signal to the remote side by inserting the test signal into the surplus bits of the overhead part of the transmission signal and transmitting the test signal to the remote side. Surplus of signal overhead The signal content of Tsu bets, characterized in that to check the transmission quality of the transmission path by comparing with the inserted test signal.

The overhead loopback test system of the present invention uses an international standard synchronous hierarchy (SDH) signal for digital communication transmission or a North American sonnet (SON).
ET) A loopback test system in which transmission between a central side and a remote side synchronous digital device is performed by a hierarchy signal having an overhead portion such as a format, and the central side synchronous digital device is used for testing. A test data generation circuit for generating a signal, an insertion circuit for inserting a test signal generated by the test data generation circuit into an extra bit of an overhead portion of a transmission signal and transmitting the signal to a remote station, A test data error detection circuit for confirming the transmission quality of the transmission path by comparing the signal content of the surplus bits of the overhead part of the transmission signal with the test signal generated by the test data generation circuit, Synchronous digital devices overhead transmission signals transmitted from the central side. The inserted signal to the redundancy bits portion, characterized in that it comprises a test data return means for varying placed on surplus bit overhead portion of the transmission signal to be transmitted to the central side.

[Operation] In the North American SONET hierarchy, sections, lines, paths, and layers are divided, and each layer has an overhead portion, so that loopback can be executed for each layer.
As for the SDH signal, since the layer is divided into the regenerator section, the multiplex section, and the path, loopback can be executed for each layer.

In the present invention configured as described above, if remote loopback is performed using the surplus bits of the overhead portion of the North American SONET signal and SDH signal, the central station changes the remote station, and the remote station changes the central station. Line quality on the transmission path to the server can be confirmed. In addition, the overhead of the signal used in the present invention exists for each layer, and the remote loopback test can be executed independently for each layer. That is, it is possible to simultaneously check the quality of each transmission line layer and a plurality of transmission lines.

[0027]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a North American SONE to which the present invention is applied.
1 is a block diagram illustrating a configuration of an embodiment of a T hierarchy network.

The structure and operation of this embodiment are described above with reference to FIG. 4 showing the signal format used in the North American SONET hierarchy network and the position of the surplus bits used in the overhead, and the SDH network. The signal format used in the above and the position of the surplus bits used in the overhead will be described with reference to FIG.

In the embodiment shown in FIG. 1, an OC-3 signal terminating (multiplexing / demultiplexing) device 201 and OC-12 signal terminating (multiplexing / demultiplexing) device 202 constituting a central station, and an OC-12 signal terminating (multiplexing / demultiplexing) device 202 constituting a remote station. Signal termination (multiplexing / demultiplexing) device 204 and OC-3 signal termination (multiplexing / demultiplexing) device 20
5. OC provided between central station and remote station
It comprises a -12 optical signal reproducing device 203.

In this embodiment, the OC-12 signal is transmitted optically through an optical fiber transmission line.
The -12 signal terminator 202 is an OC-3 signal terminator 2
01 multiplexed OC-3 signal 210 output from OC-
OC-12 optical signal reproducing device 20 as 12 optical signals 212
Output to 3. In the OC-12 optical signal reproducing device 203,
By appropriately amplifying the OC-12 optical signal 212, the OC-12
The OC-12 signal termination device 20 as the -12 optical signal 214
4 The OC-12 signal terminator 204
The -12 optical signal 214 is separated and sent to the OC-3 signal termination device 205 as an OC-3 signal 216. The return route, which is the transmission from the remote station to the central station, also follows the reverse route to the above-described forward route.
17, OC-12 optical signal 215, OC-12 optical signal 21
3. The signal is converted into an OC-3 signal 211 and transmitted.

Next, a description will be given of the operation when the maintenance person at the central office checks the quality of the signal output from the central office in the North American SONET hierarchy network shown in FIG. The OC-12 signal termination device 202 in the central station adds a section overhead and a line overhead to the higher-order group side in addition to the multiplexing operation described above. The OC-12 optical signal 212 output from the OC-12 signal termination device 202 is
Before being terminated by the two-signal terminator 204, the section overhead data generated by the central station is terminated by the OC-12 optical signal reproducing device (regenerator) 203. In addition, the OC-12 signal termination device 20 of the central office
The line overhead data generated in 2 is terminated by the opposite OC-12 signal termination device 204.

When confirming the signal quality, the OC-1
OC-12 optical signal 21 output from two-signal terminator 202
The test data is received by the OC-12 optical signal regenerating device 203 which inserts the test data into the extra bits of the section overhead of section 2 and terminates the section overhead inserted by the OC-12 signal terminating device 202, and outputs the extra bits as it is. The test data inserted in the
OC-12 optical signal 215 from the 12 signal terminator 204
And outputs the OC-12 optical signal 213 to the OC-12 signal terminating device 202. O-input to the OC-12 signal termination device 202
By checking the surplus bits of the section overhead of the C-12 optical signal 213 by the OC-12 signal terminating device 202, it is possible to confirm the line quality of the transmission lines transmitted by the OC-12 optical signals 212 and 213.

Further, the OC-12 signal terminating device 2O2 in the central office is connected to the opposite O-terminal where the line layer is terminated.
When confirming the transmission quality between the C-12 signal terminating devices 2O4, it is assumed that the test data is inserted into the extra bits of the line overhead of the signal output by the OC-12 signal terminating device 202, and the opposite OC-12 Signal termination device 2
In step 04, the line overhead of the input OC-12 optical signal 214 is detected, and upon confirming the reception of the test data, the test data is transferred as it is to the OC-12 signal termination device 202 and the OC-12 optical signal to be output is output. 215
Is inserted into the extra bits of the line overhead. The test data transferred by the OC-12 signal termination device 202 that terminates the line layer of this signal is detected, and an error is confirmed, whereby the OC-12 optical signals 212 and 214,
It is possible to confirm the line quality of the transmission path through which the transmission paths 213 and 215 are transmitted.

An OC-3 signal terminating device 201 for terminating the OC-3 of the SONET hierarchy network shown in FIG.
At 205, when it is confirmed that the surplus bits of the path overhead are not used, the OC-
The 12-signal terminating device 202 inserts test data into the extra bits of the path overhead of the OC-12 optical signal 212 to be output and outputs the test data to the OC-3 device signal termination device 205 on the opposite side. The OC-3 signal terminating device 205 detects the path overhead of the input OC-3 signal 216 and confirms the reception of the test data, and then transmits the test data to the OC-12 signal terminating device 202.
It is inserted into the extra bits of the path overhead of No. 17 and output. OC-12 in the middle route of the OC-12 signal termination device 202
The OC-3 signal 217 multiplexed on the −12 signal is
The test data of the surplus bits of the path overhead is confirmed by the 12-signal terminator 202, and the OC-3 signal 216,
It is possible to confirm the line quality of the transmission path that the 217 and the OC-12 optical signals 212 to 215 transmit.

Central station OC-3 signals 210, 21
1 is also transmitted in the OC-3 signal terminating device 201, the OC-3 signal 210 in which the test data is inserted into each of the section overhead, the line overhead, and the path overhead, and the SONET that terminates each layer. It is assumed that the loopback test data is inserted by the hierarchy device, and the OC-3 signal terminating device 201 confirms the overhead of each layer of the input OC-3 signal 211, thereby confirming the OC-signal.
The transmission quality of the transmission path through which the three signals 210 and 211 are transmitted can be confirmed.

FIG. 2 shows a transmitting section and a receiving section of a central station, a remote station or a regenerator (for example, a transmitting station and a regenerator) for inserting test data into the section overhead by the above-described test method and checking the line quality in the section layer. The OC-12 optical signal reproducing device 21 in FIG.
FIG. 2 is a block diagram showing a specific configuration of circuits provided in a sending unit and a receiving unit in 2).

The circuit shown in FIG. 2 includes an OC-3 signal termination circuit 501, an OC-3 multiplexing circuit 503, an OC-12 section overhead circuit 504, a test data generation circuit 505, and a remote Return means is provided together with the remote station OC-12 separation circuit 507 and test data detection circuit 509 provided in the reception section of the station, and the OC-12 section overhead generation circuit 510 and test data detection circuit 509 provided in the transmission section of the remote station. It comprises an OC-12 section overhead adding circuit 511, a remote station OC-12 separating circuit 512 and a test data error detecting circuit 513 provided in the receiving section of the central station.

OC-3 for receiving OC-3 signal 502
A plurality of signal termination circuits 501 are provided, and these signals are multiplexed by an OC-3 multiplex circuit 503,
It is sent to the OC-12 section overhead adding circuit 504 as a -12 payload signal 514. OC-
The 12-section overhead adding circuit 504 includes O
The remote loopback test signal 5 output from the test data generation circuit 505 in addition to the C-12 payload signal 514
17 is input and the OC-12 section overhead adding circuit 504 outputs the OC-12 payload signal 5
OC-12 signal 5 in which a test signal 517 for remote loopback is added to surplus bits of the path overhead of No. 14
06 to the remote station (or regenerator).

The remote station OC-12 separation circuit 507 provided in the remote station (or regenerator) separates the received OC-12 signal 506 into an OC-12 payload signal 508 and test data 519, and then separates the OC-12 signal 506 into test data 519.
The 12 payload signal 508 is output to a general processing circuit (not shown) other than the quality check, and the test data 51 is output.
9 is output to the test data detection circuit 509.

When the test data detection circuit 509 confirms the test data 519, the test data 520 indicating the contents thereof is displayed.
To the OC-12 section overhead adding circuit 511
Send to In addition to the test data 520, the OC-12 section overhead adding circuit 511 also includes an OC-12 payload signal 516 from the general processing circuit described above.
And an OC-12 section overhead generation circuit 51
0 is input, the section overhead is added to the OC-12 payload signal 516, and the test data 520 is added to the extra bits of the path overhead.
06 to the central office.

Central office OC-12 separation circuit 512
Separates the received OC-12 signal 506 into an OC-12 payload signal 515 and test data 518,
The OC-12 payload signal 515 is output to a general processing circuit (not shown) other than the quality check, and the test data 518 is output to a test data error detection circuit 513. The test data error detection circuit 513 checks the quality of the transmission path through which the OC-12 signal 506 is transmitted from the contents of the test data.

[0043]

Since the present invention is configured as described above, it has the following effects.

The test data is inserted into the overhead part, and the payload data (communication data) of a medium which is actually communicating with a telephone, a computer, or the like.
Since the configuration does not involve any part, it is possible to check the transmission quality at the time of maintenance without stopping the line service, and since the signal overhead exists for each layer, it is used. The effect is that a test can be performed for each line layer.

Furthermore, since no measuring instrument is used, the cost can be reduced accordingly. In addition, a plurality of remote loopbacks can be set independently for each layer or for each channel, and the transmission quality can be confirmed.

[Brief description of the drawings]

FIG. 1 is an example of a digital network to which the present invention is applied;
FIG. 2 is a block diagram illustrating a configuration of an ONET hierarchy network.

FIG. 2 is a block diagram showing a circuit configuration when implementing the present invention.

FIG. 3 is a diagram for explaining a transmission quality checking method at the time of maintenance in a conventional SONET hierarchy network.

FIG. 4 is a diagram showing a SONET hierarchy signal format.

FIG. 5 is a diagram showing an SDH signal format.

[Explanation of symbols]

Reference Signs List 201 OC-3 signal termination (multiplexing / demultiplexing) device 202 OC-12 signal termination (multiplexing / demultiplexing) device 203 OC-12 optical signal reproducing device 204 OC-12 signal termination (multiplexing / demultiplexing) device 205 OC-3 signal termination (Multiplexing / demultiplexing) device 210 OC-3 signal 211 OC-3 signal 212 OC-12 signal 213 OC-12 signal 214 OC-12 signal 215 OC-12 signal 216 OC-3 signal 217 OC-3 signal 501 Central station OC-3 signal termination circuit 502 OC-3 signal 503 OC-3 multiplexing circuit 504 OC-12 section overhead addition circuit 505 Test data generation circuit 506 OC-12 signal 507 Remote station OC-12 separation circuit 508 OC-12 payload signal 509 Test data detection circuit 510 OC-12 section Bar head generation circuit 511 OC-12 section overhead addition circuit 512 Remote station OC-12 separation circuit 513 Test data error detection circuit 514 OC-12 payload signal 515 OC-12 payload signal 516 OC-12 payload signal 517 Test for remote loopback Signal 518 Test data taken out by central station 519 Test data taken out by remote station 520 Test data taken out by remote station

Claims (2)

(57) [Claims] An international standard synchronous hierarchy (SDH) signal for performing digital communication transmission or a hierarchy signal having an overhead portion such as a North American SONET (SONET) format allows transmission between a central-side and remote-side synchronous digital device. A loopback test method in a system to be performed, in which a signal inserted into a surplus bit of an overhead part of a transmission signal is replaced on a surplus bit of a signal overhead part on a remote side and transmitted to a central side. On the central side, the test signal is inserted into the extra bits of the overhead portion of the transmission signal and transmitted to the remote side, and the signal content of the extra bits of the overhead portion of the signal sent from the remote side at this time is inserted. By comparing with the test signal Overhead loopback testing method characterized by confirming the transmission quality of the sending passage. 2. Transmission between the central and remote side synchronous digital devices by an international standard synchronous hierarchy (SDH) signal for performing digital communication transmission or a hierarchy signal having an overhead section such as a North American SONET (SONET) format. A synchronous digital device on the central side includes a test data generation circuit for generating a test signal, and a test signal generated by the test data generation circuit. An insertion circuit that inserts into the surplus bits of the overhead part and sends it to the remote station; and a test signal generated by the test data generation circuit, the signal content of the surplus bits of the overhead part of the transmission signal transmitted from the remote side. Test data that confirms the transmission quality of the transmission line by comparing The synchronous digital device on the remote side is provided with an extra bit of the overhead part of the transmission signal transmitted to the central side for the signal inserted into the extra bit of the overhead part of the transmission signal transmitted from the central side. An overhead loopback test method, comprising a test data returning means for changing the test data.