JPH10126432A - Passing double star communication system having crossing duplicate configuration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To distinguish the case of occurrence of a fault in a transmission line of all subscriber equipments with respect to a star coupler from the case of occurrence of a fault in transmission lines between the star coupler and a station side-equipment in the PDS(passive double star) communication system of crossing duplicate configuration. SOLUTION: A star coupler 30 is provided with a loopback transmission line 32 looping back part of an optical signal from a station side equipment 12. When a transmission line fault detection section 34 detects interruption of a signal from all subscriber equipments and the loopback signal is normally received, it is discriminated that the fault is resident in a B block and when the transmission line fault detection section 34 detects interruption of a signal from all subscriber equipments and the loopback signal is not received, it is discriminated that the fault is resident in an A block.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PDS (Passive Double Star) in which an optical line terminal and a plurality of subscriber units are connected by a star coupler which is an optical passive component.
The present invention relates to a communication system, and more particularly to a PDS communication system adopting a cross-type duplex configuration in which transmission lines for an active system and a standby system for duplex are cross-coupled by a star coupler.

[0002]

2. Description of the Related Art As shown in FIG. 1, a PDS communication system has a configuration in which an optical line terminal 12 and a plurality of subscriber units 14 are connected by a star coupler 10, which is an optical passive component. In the system shown in FIG. 1, the uplink signal from the subscriber unit 14 and the downlink signal from the optical line terminal 12 are multiplexed, so that the signal between the optical line terminal 12 and the star coupler 10 and between the optical line coupler 10 and each Two-way communication between the user devices 14 is realized by one optical fiber. In order to multiplex an uplink signal and a downlink signal, WDM (Wavelength) in which the wavelength of light differs between the uplink signal and the downlink signal.
Division Multiplexing (TCM) or Time Compression (TCM) that compresses the time axis and transmits them alternately
press multiplexing). Also, the transmission time between the optical line terminal 12 and each of the subscriber devices 14 is measured in advance, and the TDM / TDM that instructs and controls the transmission timing from the optical line device 12 so that the uplink signals from the individual subscriber devices 14 do not overlap. TDMA (Time Div
issue Multiplex / Time Divi
A session multiple access) system is adopted.

When the PDS communication system shown in FIG. 1 is duplexed to improve reliability, as shown in FIG. 2, two optical transmission lines, one of which is to be an active system and the other of which is a standby system, are also connected to a star coupler. A cross-type duplexing configuration that combines at 10 has been proposed in JP-A-7-250028. According to this configuration, as described below,
The operation / standby switching can be performed independently between the star coupler 10 and the optical line terminal 12 and between the star coupler 10 and each of the subscriber units 14.

FIG. 3 is a diagram for explaining switching between operation and standby in the system of FIG. In FIG. 3, a transmission line that is a standby system is indicated by a broken line. That is, in the example of FIG. 3, the transmission line of system 0 and the transmission / reception unit of system 0 are all used as the active system, and the transmission line of system 1 and the transmission / reception unit of system 1 are all set as the standby system. In the transmission / reception unit that was set as the standby system,
For transmission, the light emission is stopped so as not to collide with the optical signal from the active system, or the output timing is controlled so as not to collide with the optical signal from the active system. Is ignored.

[0005] Next, a description will be given of failure evaluation and switching control in a PDS system having a cross-type duplex configuration. It is assumed that a failure has occurred in the transmission path 20 in FIG. Then, the transmission path failure detection unit 24 through the transmission / reception unit 0 22 of the optical line terminal 12
Detects that the input of the signal from the subscriber unit # 1 has been interrupted. In response to this, the optical line terminal 12 issues a switching command to the subscriber device # 1, and switches the operating system from the 0 system to the 1 system.
The first system is put into the operation state. At this time, switching between the optical line terminal 12 and the other subscriber devices # 2 to #n is not performed, and the 0-system operation state is maintained.

When a failure occurs in the transmission line 26 in FIG. 3, the transmission line failure detecting unit 24 causes all the subscriber units # 1
Input disconnection of signals from #n to #n is detected. In this case, in the optical line terminal 12, the active system is switched from the 0 system to the 1 system, and the 1 system is in the operating state. At this time, switching is not performed for each of the subscriber units, and the system remains in the 0-system operation state.

As described above, in the cross-type redundant configuration system, a failure in a portion common to each subscriber device (a failure occurring in the section A of the transmission line in FIG. 3) and a failure in an individual portion of each subscriber device (see FIG. 3). 3), and switching control corresponding to the failed section can be performed.

[0008]

In the cross-type redundant configuration system, as described above, a fault can be evaluated and switching can be restored in accordance with the section of the transmission line, but the problem remains in the following cases. The point is that it is impossible for the optical line terminal to distinguish between the case where the failure occurs in the active transmission line in section B and the case where the failure occurs in the active transmission line in section A for all the subscriber units.

A failure occurs simultaneously in all of the active transmission lines connected to the subscriber units # 1 to #n (or
If only one subscriber unit is connected and a failure occurs), the transmission line failure detection unit 24 determines that all the subscriber units # 1 to #n are in the same manner as when a failure occurs in the transmission line 26. Is detected. Therefore,
The optical line terminal determines that the transmission line 26 has a failure based on the alarm, and switches the operating system of the optical line terminal from the 0 system to the 1 system to put the 1 system into the operating state. At this time, each subscriber device is not switched and remains in the 0-system operation state. In this state, the fault remains unrecovered. In order to recover the failure, it is only necessary to issue a switching command from the optical line terminal to each of the subscriber units to perform the switching control. Disadvantage occurs. That is, there is a problem in a method of determining a failure section of the transmission path.

Accordingly, it is an object of the present invention to provide a communication system in which a failure occurs in all of the transmission lines connected to a subscriber unit, or when only one subscriber unit is connected and a transmission line connected thereto has a fault. Another object of the present invention is to make it possible to identify when a failure has occurred in a transmission line connected to a side device.

[0011]

According to the present invention, there is provided a station apparatus having two transmitting / receiving units, one of which is to be assigned to an active system and the other to a standby system. And a plurality of second transmission lines connectable to each of the transmission / reception units of at least one subscriber apparatus having two transmission / reception units, one of which is to be assigned to the active system and the other of which is to be assigned to the standby system. A star coupler that couples a transmission line and all of the first transmission line and branches to all of the second transmission line, and transmits a part of an optical signal from the first transmission line to the first transmission line. In a star coupler having a folded transmission path that is turned back to a path and an optical line terminal connected to the first transmission path, an input disconnection is detected for all optical signals from the subscriber units connected to the second transmission path. When the star coupler returns Means for specifying whether a failure has occurred in the first transmission line or in the second transmission line depending on whether or not an input disconnection is detected for an optical signal folded back in the path. A passive double-star communication system having a configuration is provided.

According to the present invention, a plurality of first transmission paths connectable to each of the transmission / reception units of a station side apparatus having two transmission / reception units to be allocated to the active system and the standby system to the other system. A plurality of second transmission paths connectable to each of the transmission / reception units of at least one subscriber apparatus, one of which has two transmission / reception units to be allocated to the active system and the other to the standby system; All of the 1 transmission lines,
An optical signal from a transmission / reception unit assigned to an active system from a transmission / reception unit assigned to a standby system of a subscriber device connected to the second transmission line, and a star coupler branched to all of the second transmission line. Means for transmitting a failure-determining optical signal to the second transmission line, which is identifiable with the first transmission line, and an operation system of the subscriber unit connected to the second transmission line in the station-side device connected to the first transmission line. When the input disconnection is detected for all of the optical signals from the transmitting / receiving units assigned to the first, the first failure occurs depending on whether the input disconnection is detected for the failure determination optical signal.
Means for identifying whether the transmission has occurred on one of the transmission paths or on the second transmission path.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 shows a passive double star (P) having a cross-type duplex configuration according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a DS) communication system. In FIG.
As in the case of the star coupler 10 in the system of FIG.
A PDS system having a cross-type duplex configuration is realized between the PDS system. The star coupler 30 further has a return transmission line 32 for returning a part of the optical signal from the optical line terminal 12 to the optical line terminal 12. The return transmission line 32 is realized by connecting two of a large number of branches on the subscriber device side of the star coupler 30 as shown in FIG. 4, for example. The transmission path failure detection unit 34 detects an optical signal that is turned back on the return transmission path 32 of the star coupler 30 in addition to the failure detection similar to the transmission path failure detection unit 24 in FIG. An optical signal detector may be provided in addition to the transmission line failure detector 24 in FIG.

Referring to FIG. 5, a failure evaluation according to the first embodiment of the present invention will be described. In the example shown in FIG.
The transmission line of the system 0 and the transmission / reception unit of the system 0 are all used as the active system, and the transmission line of the system 1 and the transmission / reception unit of the system 1 are all set as the standby system (the transmission line is indicated by a broken line). At this time,
When a failure occurs in the transmission line 20, similarly to the system shown in FIG. 2, the transmission line failure detection unit 34 detects the disconnection of the signal from the subscriber unit # 1 and recognizes that the transmission line 20 has failed. Is done. In response, the active system of subscriber device # 1 is switched from system 0 to system 1.

When a failure occurs in the transmission line 26, the transmission line failure detecting section 34 sets all the subscriber units # 1 to #
n is detected, and the star coupler 30 transmitted from the transmission / reception unit 0 system 22 of the optical line terminal 12
The signal returned in the return transmission path 32 cannot be received. Therefore, the transmission line failure detection unit 34
It is possible to recognize that a fault has occurred in the section, that is, the transmission line 26, and the station side device 12 switches the active system from the 0 system to the 1 system.

When a failure has occurred in all of the active transmission lines connected to the subscriber units # 1 to #n, input interruptions of signals from all the subscriber units # 1 to #n are detected. The return signal is normally received because it is not related to the failure in the section B. Therefore, in this case, the transmission line failure detection unit 34 can recognize that a failure has occurred in the section B, and the active system is switched from the 0 system to the 1 system for all the subscriber units # 1 to #n.

The signals returned in the return transmission line 32 are received at different timings from the signals from the subscriber units # 1 to #n, so that they can be recognized. The station side device 12
A method of multiplexing an optical signal having a different wavelength or a time slot with both the downstream signal from the mobile station and the upstream signal from the subscriber unit 14 in the transmission / reception unit 22 of the optical line terminal 12 and detecting the presence or absence of a loopback signal based on this signal is more preferable. good. The detection of this return signal is performed by the transmitting / receiving section of the active system (FIG. 5).
In this case, the transmission can be performed through the transmission / reception unit 0 (system 22), but the method is preferably performed through the backup transmission / reception unit (system 1 in FIG. 5).

FIG. 6 shows a second embodiment of the present invention. A second feature of the cross-type duplex configuration is that it can accommodate a subscriber unit having only one transmission / reception unit like the subscriber unit 15 of FIG. Also in this case, by providing the folded transmission path 32 in the star coupler 30, it is possible to isolate a faulty section as in the first embodiment. However, the switching operation is not performed for the subscriber device # 2 having no duplex configuration even if a failure occurs in the section B.

FIG. 7 shows a PDS communication system having a cross-type duplex configuration according to a third embodiment of the present invention. In the system of FIG. 7, a subscriber optical signal transmission unit 40 is provided corresponding to each transmission / reception unit of each subscriber device 14, and the optical line terminal 12 includes:
An optical signal receiver for subscriber 42 for detecting the presence or absence of an optical signal from the optical signal transmitter for subscriber 40 is provided. The optical signal transmitting unit for subscriber 40 outputs an optical signal for failure determination when the corresponding transmitting / receiving unit is set as the standby system. This optical signal has a different wavelength or time slot from the optical signal emitted from the active transmission / reception unit of the subscriber unit and the optical line terminal so as not to collide with the optical signal.

Referring to FIG. 8, a description will be given of a failure evaluation according to a third embodiment of the present invention. In the example shown in FIG.
The transmission line of the system 0 and the transmission / reception unit of the system 0 are all used as the active system, and the transmission line of the system 1 and the transmission / reception unit of the system 1 are all set as the standby system (the transmission line is indicated by a broken line). At this time,
When a failure occurs in the transmission line 20, similarly to the system shown in FIG. 2, the transmission line failure detecting unit 24 detects that the input of the signal from the subscriber unit # 1 has been interrupted, and recognizes that the transmission line 20 has failed. Is done. In response, the active system of subscriber device # 1 is switched from system 0 to system 1.

When a failure occurs in the transmission line 26, the transmission line failure detection unit 24 detects that signals from all the subscriber units # 1 to #n have been disconnected, and the subscriber optical signal receiving unit 42 The received optical signal from the optical signal transmitter for subscriber 40 cannot be received. Therefore, the optical line terminal 12 can recognize that a failure has occurred in the section A, that is, the transmission line 26, and the operating side is switched from the 0 system to the 1 system in the optical line terminal 12.

When a failure occurs in all of the active transmission lines connected to the subscriber units # 1 to #n, the interruption of signal input from all the subscriber units # 1 to #n is detected. If the standby system is normal, the optical signal from the optical signal transmitter for subscriber 40 is normally received. Therefore, in this case, the optical line terminal 12 can recognize that a failure has occurred in section B, and the active system is switched from system 0 to system 1 for all the subscriber units # 1 to #n.

FIG. 9 shows a fourth embodiment of the present invention. In the present embodiment, a subscriber device having only one transmission / reception unit like the subscriber device 15 is accommodated. Also in this case, by providing the optical signal transmitting unit for subscriber 40 on the subscriber unit side and the optical signal receiving unit for subscriber unit 42 on the optical line terminal, the third
In the same manner as in the embodiment, the fault section can be separated. However, the switching operation is not performed for the subscriber device # 2 having no duplex configuration even if a failure occurs in the section B.

[0024]

As described above, according to the present invention, in a PDS communication system having a cross-type duplex configuration, all the subscriber units (or only one subscriber unit when connected) are connected. Regarding) It is possible to distinguish between a case where a failure has occurred in the transmission line between the subscriber unit and the star coupler and a case where a failure has occurred in the transmission line between the star coupler and the optical line terminal.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a PDS communication system.

FIG. 2 is a block diagram showing a conventional PDS communication system having a cross-type duplex configuration.

FIG. 3 is a diagram for explaining the operation of the system in FIG. 2;

FIG. 4 is a block diagram showing a first embodiment of the present invention.

FIG. 5 is a diagram for explaining the operation of the system in FIG. 4;

FIG. 6 is a block diagram showing a second embodiment of the present invention.

FIG. 7 is a block diagram showing a third embodiment of the present invention.

FIG. 8 is a diagram for explaining the operation of the system in FIG. 7;

FIG. 9 is a block diagram showing a fourth embodiment of the present invention.

[Explanation of symbols]

 10, 30 ... star coupler 20, 26 ... transmission line 32 ... return transmission line

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Nario Amemiya 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Yuki Fujii 4-chome, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa No. 1 Fujitsu Limited (72) Inventor Takafumi Nakajo 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Koji Tezuka 4 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture 1-1-1, Fujitsu Limited (72) Inventor Yoshiro Takigawa 3-2-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A plurality of first transmission lines connectable to each of the transmitting and receiving units of an optical line terminal having two transmitting and receiving units to be assigned to an active system and the other to a standby system. 2 to be assigned to the working system and the other to the standby system
A plurality of second transmission paths connectable to each of the transmission / reception sections of at least one subscriber apparatus having a transmission / reception section of a system; and all of the first transmission paths are coupled to each other. A star coupler having a folded transmission path for returning a part of the optical signal from the first transmission path to the first transmission path; and a station connected to the first transmission path. In the device, when the input disconnection is detected for all of the optical signals from the subscriber units connected to the second transmission path, whether the input disconnection is detected for the optical signal returned in the return transmission path of the star coupler. Means for identifying whether a failure has occurred on the first transmission line or on the second transmission line depending on whether the failure has occurred or not. 2. A plurality of first transmission paths connectable to each of the transmitting and receiving units of the station-side apparatus having two transmitting and receiving units to be assigned to the active system and the other to the standby system, respectively. 2 to be assigned to the working system and the other to the standby system
A plurality of second transmission paths connectable to each of the transmission / reception sections of at least one subscriber apparatus having a transmission / reception section of a system; and all of the first transmission paths are coupled to each other. A star coupler that branches to all, a transmission / reception unit assigned to the standby system of the subscriber unit connected to the second transmission line, and a failure determination that can be distinguished from an optical signal from the transmission / reception unit assigned to the operation system. Means for transmitting an optical signal to the second transmission line; and a transmitting / receiving unit assigned to the operation system of the subscriber unit connected to the second transmission line in the station-side device connected to the first transmission line. When the input disconnection is detected with respect to all of the optical signals, a failure has occurred in the first transmission line depending on whether or not the input disconnection has been detected in the failure determination optical signal. Means for identifying whether or not a crossover has occurred Passive Double Star communication system having a reduction configuration.