JPH05336139A - Ring optical transmission system - Google Patents

Abstract

PURPOSE:To quickly selects a path switch on the occurrence of a line fault by selecting the path switch on the detection of alarm information and inserting the alarm information again to an overhead part and sending the result from an opposite line. CONSTITUTION:When an optical fiber fault (1) takes place in an active line W, an ADM-C station being a through-station detects an alarm (2). Then alarm information is inserted to an overhead part (3) through the alarm detection (2) and the resulting signal is sent to a standby line P. An ADM-A station receiving the optical signal including the alarm information from the standby line P detects the overhead part in the reception signal (4). Then the path switch PSW is selected from the active line W to the standby line P, and the alarm information is inserted to an overhead part (5) attending overhead detection (4) and the alarm information is transferred to a succeeding ADM-B station through the standby line P.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring type optical transmission system, and more particularly to a plurality of repeater stations each having a path switch, which are preset as branching / inserting stations or through stations. The present invention relates to a ring type optical transmission system in which a working line and a protection line in opposite directions are connected in a ring shape.

SONET (Synchrono) of recent optical transmission equipment
us Optical Network) or SDH (Synchronous Digital)
Along with the demand for synchronous network by Hierarchy) and improvement of network rescue capability, a ring type optical transmission system as shown in FIG. 3 is provided as one of the systems.

In this ring type optical transmission system, a plurality of repeater stations (Add / Drop Multiplexer: hereinafter sometimes abbreviated as ADM) are provided with a counterclockwise working line W and a clockwise protection line P as shown in the figure. Each relay station ADM has a path switch PSW and is preset by a central station (not shown) as a branch / insert station or a through station. In the example, the ADM-A station and the ADM-B station are branch / insert stations, and the other relay stations ADM-C to ADM-E are through stations and ADM-
The A station and the ADM-B station communicate with each other.

[0004]

2. Description of the Related Art In such a ring type optical transmission system, the number of stations is larger than that of ADM stations as shown in FIG.
In the system of FIG. 4 in which DM-A station to ADM-K station intervene, when the working line W causes an optical fiber failure as shown in the figure, the ADM-C station detects the optical fiber failure and detects a path alarm signal PAIS ( Path Alarm Indica
signal) is transmitted and this path alarm signal PA
IS sends ADM-B via ADM-D station to ADM-K station
When the path alarm signal PAIS is detected in the ADM-B station set as the branching / inserting station when given to the station, the path switch PSW receives the protection line P from the current working line W until now. The signal is switched so as to be branched, and thereafter, the ADM-A station and the ADM-B station communicate with each other using the working line W and the protection line P.

FIG. 5 specifically shows the ADM-C station, the ADM-A station, and the ADM-B station in the ring type optical transmission system shown in FIG. 4, respectively, and the configuration of each ADM is the same. Therefore, the configuration will be described first using the ADM-C station as an example.

In the ADM-C station, first, on the side of the working line W, an overhead branching unit (OH) for branching an overhead part in the optical signal from this working line W
DROP) 11, an alarm signal generator 12 that generates a path alarm signal PAIS, an alarm detector 13 that detects a line disconnection state of the working line W, and an overhead brancher 11 that is controlled by the alarm detector 13 or A selector (SEL) 14 for selecting one of the output signals of the alarm signal generator 12 and either the output signal of the selector 14 or the insert signal ADD of its own station is a control signal of a central monitoring unit (not shown). It includes a selector (SEL) 15 that is selected by the above, and an overhead insertion unit (OH.INS) 16 that inserts an overhead unit OH from its own station into the output signal of this selector 15.

In the configuration for the working line W, the overhead branching unit 21, the alarm signal generating unit 22, the alarm detecting unit 23, the selector 24, the selector 25, and the overhead inserting unit 26 are similarly arranged for the protection line P. It is provided.

The payload portion extracted by the overhead branching unit 11 is sent to the path switch PSW via the gate G2 controlled by the central control unit, and similarly from the overhead branching unit 21. The gate section G1 is also controlled by the central controller.
And is sent to the path switch PSW via. The path switch PSW is the working line W.
A branch signal from the working line W or the protection line P, which is controlled by an alarm detection unit 31 that detects an alarm signal PAIS in the main signal from the main circuit and an alarm detection unit 32 that detects an alarm signal PAIS in the main signal in the protection line P. D
I try to get ROP.

In such a conventional configuration, the selectors 15 and 25 are set to be through in the ADM-C station, and are set to the branch / insertion state in the ADM-A station and the B station. Further, the gates G1 and G2 are also controlled by the central control unit, and the ADM-C station is gated.
The G1 and G2 are closed to cut off the signal, and the ADM-A station and the B station are opened.

When no line failure occurs in such a state, for example, the insertion signal ADD from the ADM-A station is transmitted through the selectors 15 and 25 and the overhead insertion units 16 and 26 to the working line W and the protection line. It is sent to both the lines P, and on the working line W, ADM
A through station such as the -C station branches the overhead section OH at the overhead branch section 11 and selects the selectors 14 and 15 from each other.
The overhead section OH is added again by the overhead insertion section 16 and sent out, and substantially only the payload section is allowed to pass therethrough, and the path switch PSW is closed because the gate G1 is closed. It will not be sent to.

In the protection line P, the overhead section OH is similarly branched in the overhead branch section 21 in the ADM-B station, the payload section is taken out and sent to the selector 25 via the selector 24. At this time, Since the selector 25 is set to select the insertion signal ADD of the ADM-B station from the central control unit, it is cut off by the selector 25.

The optical signal on the working line W sent through the ADM-C station and the subsequent ADM station is AD.
After the overhead section OH is taken out by the overhead branch section 11 of the MB station, the payload section is sent to the path switch PSW via the gate G1.
It is adapted to be received as a branch signal DROP at the DM-B station. At this time, the selector 15 is
Since it is switched to select the insertion signal ADD of the -B station, the output signal of the selector 14 is not transmitted.

In such a state, for example, when an optical fiber failure occurs between the ADM-A station and the C station in the working line W as shown in the figure, the alarm detecting section 1 of the ADM-C station
Since 3 detects this line disconnection state, the path / alarm signal PAIS from the alarm signal generating section 12 is selected and output by switching the selector 14, and the same is performed through the selector 15 and the overhead inserting section 16. For example, it will be sent to the ADM-B station.

In this ADM-B station, when the payload section is sent to the path switch PSW via the overhead branching section 11 and the gate G in the same manner as described above, the alarm detection section 31 causes the path alarm in this payload section. Since the signal PAIS is detected and the path switch PSW is switched from the dotted line position to the solid line position as shown by the arrow in the figure, the ADM-A station operates as described above.
Similarly, an optical signal sent from the station from the protection line P is passed through the overhead branching unit 21 to the path switch PSW.
Can be obtained as a branch signal DROP, and the fault condition as shown in FIG. 4 is recovered.

[0015]

As described above, in the conventional ring type optical transmission system, switching is performed when an optical fiber failure occurs. However, as shown in FIG. 4, many ADM stations form a ring. When it exists, it passes through many ADM stations from the C station to the B station, so that it takes a long time to switch the path switch PSW in the B station, which causes the switching time standard to be exceeded. was there.

Therefore, according to the present invention, a plurality of relay stations, each of which has a path switch and is preset as a branching / inserting station or a through station, are ring-shaped by working and protection lines in opposite directions. In the ring type optical transmission system connected to, the purpose is to quickly switch the path switch when a line failure occurs.

[0017]

FIG. 1 schematically shows a ring type optical transmission system according to the present invention.
The present invention will be described below with reference to this figure.

First, in the case of FIG. 1 as well, the ADM
-C station is used as a through station and ADM-A and B stations are branched.
When the insertion station is set, the insertion signal from the ADM-A station is sent to the working line W and the protection line P, and normally, via the working line W, the ADM-B station as a communication partner passes through the path switch PSW. Although it is received as a branch signal, when an optical fiber failure occurs in the working line W as shown in the figure, the ADM as a through station is used.
-The alarm detection is performed in the station C, and upon reception of this alarm detection, the overhead line is inserted, and the optical signal including the alarm information is transmitted from the protection line P to the protection line P which is the reverse line.

The ADM-A station which has received the optical signal containing the alarm information from the protection line P detects the overhead part of the received signal, and thereby shifts the path switch PSW from the working line W to the protection line P. At the same time as switching, the alarm state is transferred to the next ADM-B station via the protection line P by the overhead insertion due to the above overhead detection.

Therefore, overhead detection is similarly performed in the ADM-B station, whereby the path switch PSW can be switched from the working line W to the protection line P, so that the path switch of the ADM-B station is switched. PSW switching is performed quickly without passing through many ADM stations, and the insertion signal from the ADM-A station is overhead-inserted and then the ADM from the protection line P is used.
-It is transferred to the B station and becomes a reception signal of the ADM-B station as a branch signal via the path switch PSW.

[0021]

FIG. 2 shows an embodiment of a ring type optical transmission system according to the present invention. Also in this embodiment, FIG.
The ADM-C station is set as a through station and the ADM-A station and B station are set as branch / insert stations in accordance with the conventional example shown in FIG.

Further, since the configuration of each ADM station is the same also in this embodiment, a configuration different from the conventional example shown in FIG. 5 will be described by taking the ADM-C station as an example.
When the alarm is detected, the alarm information is sent to the overhead inserting section 26, where the alarm information is inserted in the overhead section OH of the own station and sent to the protection line P. When an optical signal including the section OH is received, the overhead branch section 21 branches the overhead section OH as shown in the ADM-A station and the B station (not shown in the ADM-C station for simplifying the drawing). At the same time, the alarm information is sent to the path switch PSW and the overhead inserting section 26. The path switch PSW switches the branch of the branch signal DROP, and the overhead inserting section 26 inserts the alarm information into the overhead section OH and transfers it. I am trying.

In the embodiment of FIG. 2, the signal line from the overhead branching unit 21 to the path / PSW / overhead inserting unit 26 and the alarm detecting unit 13 are provided only on the protection line P side in order to simplify the drawing. Although only the signal line to the overhead inserting unit 26 is shown, the signal line from the alarm detecting unit 23 to the overhead inserting unit 16 and the signal from the overhead branching unit 11 to the path switch PSW and the overhead inserting unit 16 are shown in exactly the same manner. Needless to say, lines are also provided.

In this embodiment of the present invention, when an optical fiber failure occurs in the working line W as shown in the figure, the alarm detection unit 13 detects this line disconnection state and sends alarm information to the overhead insertion unit 26. Then, the overhead inserting section 26 inserts the alarm information into the overhead section OH of the optical signal sent via the protection line P, and also sends the alarm information to the adjacent ADM-A station via the protection line P.

Then, in the ADM-A station, the overhead branching unit 21 branches this alarm information.
In response to this, the path switch PSW is controlled to switch from the dotted line position to the solid line position as shown in the figure, and the payload section output from the overhead branching section 21 is received as the branch signal DROP via the path switch PSW. become.

The alarm information branched by the overhead branching unit 21 is sent to the overhead inserting unit 26,
At this time, since the ADM-A station is set as the branching / inserting station and the insertion signal ADD is sent to the overhead inserting section 26 via the selector 25, the overhead inserting section 26 adds alarm information. It is sent from the protection line P to the adjacent ADM-B station.

Similarly, in the ADM-B station, the path switch PSW is switched from the dotted line position to the solid line position as shown in the figure by the alarm information branched by the overhead branching unit 21 to obtain the branch signal DROP.
Similarly, the alarm information branched by the overhead branching section 21 is inserted into the overhead section OH of the insertion signal ADD of the ADM-B station and sent out from the protection line P.

Therefore, the insertion signal ADD of the ADM-A station is sent to the ADM-B station from the protection line P via the selector 25 and the overhead insertion section 26, and is branched from the overhead branch section 21 via the path switch PSW to the branch signal DR.
It will be received as OP.

When an optical fiber failure occurs in this way, the path of all ADM stations on the normal reverse line
The switch PSW is switched from the line in the fault state to the normal line side to receive the branch signal DROP, but in reality, the overhead section OH branched by the overhead branch section 21 is the ADM of the partner. Since the station is specified, the branch signal DR from the path switch PSW
Even if the OP is branched, only the ADM station designated by the overhead section OH receives the payload section.

Although each ADM station has an alarm generator 12 as in the conventional case, this is not particularly used in the present invention, but actually, this path alarm signal PAIS is used. It is provided as it is because the subsequent ADM station can perform, for example, link monitoring.

[0031]

As described above, according to the ring type optical transmission system of the present invention, each relay station (ADM) inserts alarm information into the overhead portion of the transmission signal when detecting a line failure. It is configured to send from the reverse line, switch the path switch so that the data is branched from the reverse line side when the alarm information is detected, insert the alarm information into the overhead part again and transmit from the reverse line. Therefore, even if the number of relay stations increases, the switching of path switches can be performed in a short time, and the failure relief capability of the optical transmission system can be greatly improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing in principle a ring type optical transmission system according to the present invention.

FIG. 2 is a block diagram showing an embodiment of each relay station (ADM) in the ring type optical transmission system according to the present invention.

FIG. 3 is a block diagram showing a general ring type optical transmission system.

FIG. 4 is a block diagram for schematically explaining a conventional method.

FIG. 5 is a block diagram more specifically showing a configuration of each relay station (ADM) in the conventional system.

[Explanation of symbols]

 PSW path switch ADM relay station W working line P protection line 11,21 overhead branching unit 13,23 alarm detection unit 16,26 overhead insertion unit In the drawings, the same reference numerals indicate the same or corresponding parts.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 8426-5K H04B 9/00 H

Claims (1)

[Claims] 1. A plurality of relay stations (ADM), each having a path switch (PSW) and preset as a branch / insert station or a through station, are used in the opposite directions. In a ring type optical transmission system connected in a ring by lines (W, P), when each repeater station (ADM) detects a reception line fault, alarm information is inserted into the overhead part of the transmission signal and the reverse line is used. The path switch so that the data is branched from the reverse line side when the alarm information is detected.
A ring type optical transmission system characterized by switching (PSW) and inserting the alarm information into the overhead section again and transmitting from the reverse line.