JPH05252548A - Stand-by system switching method in optical subscriber's transmission system - Google Patents

Abstract

PURPOSE:To reduce the number of the stand-by systems of an in-station transmitter, and reduce a construction cost without damaging a reliability by providing a switching function at a switchboard and an optical fiber main wiring rack. CONSTITUTION:Signal interruption information from an in-station transmitter 3 is received by a switching controller 10, and a switching operation command is transmitted to both the optical fiber main wiring rack 9 and the switchboard 1. And also, a subscriber's side transmitter 4 is automatically switched based on the interruption of a transmission signal. The switchboard 1 is equipped with a switching function, so that the operation of the switchboard 1 can be attained only by changing a program. Then, at the time of operating a failure transfer, a stand-by optical fiber 5' is connected through the optical fiber main wiring rack 9 with a stand-by optical transmitting and reception unit 3-1' and a high speed switching is operated by the switchboard 1. And also, the subscriber's side transmitter 4 is automatically switched to the stand-by system by the signal interruption of a present system side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a standby system switching system applied to a subscriber transmission system using an optical cable as a transmission medium when a failure occurs, when an optical cable trouble is relocated, or when a transmission device is updated.

[0002]

2. Description of the Related Art An optical cable is a cable in which an optical fiber is mounted and is also called an optical fiber cable. With the progress of optical communication technology, introduction of optical fibers into subscriber systems including general households as well as relay systems between stations has been studied. In this case, in addition to the method of directly wiring the optical fiber to ordinary households, there is a method of using the optical fiber up to the middle and separating the signal and wiring to multiple subscribers with a metal wire in a star shape. Is being considered. Thereafter, the former is the FTTH (Fiber To The Home) method, and the latter is the CT-RT (Central Terminal Remot).
e Terminal) method. In the transmission system, the backup system is useful when a failure occurs and when the trouble of the optical cable is transferred. First, from the viewpoint of failure recovery, a backup system switching method that has been studied conventionally will be described.

A failure in the optical fiber transmission system can occur in both the transmission device and the transmission path. In addition to an electronic circuit, a light emitting element and a light receiving element such as a semiconductor laser exist in the transmission device, and damage to these elements causes a failure. Since the light emitting element and the light receiving element have shorter lives than general electronic components, the reliability of the transmission system is likely to be impaired. Further, in the transmission line, a failure occurs due to breakage of the optical fiber or deterioration of the connector connection part. Since the optical fiber itself does not suffer from deterioration such as corrosion unlike the conventional metal cable, it has an advantage that it is generally highly reliable. However, optical fiber connection and wiring work is more time-consuming than when using metal wires, so if the optical cable is accidentally damaged due to road construction, it will take a long time to recover. There's a problem. Furthermore, in the current maintenance system, there is a problem that it takes time to search for a failure point itself. From such a thing,
In a communication system that requires reliability, it is necessary to take measures for prompt recovery when a failure occurs.

The existing optical fiber transmission system has the above-mentioned problems. Therefore, in order to shorten the recovery time, a transmission system in which a transmission device and a transmission line are duplicated is being studied. FIG. 3 shows a form of the duplex system. Figure 3 (A) is F
The TH system, and FIG. 3B is the CT-RT system. Figure 3
In (A), the optical fiber is directly drawn to the subscriber. The subscriber-side transmission device 4 is located in the subscriber's house. The exchange 1 and the intra-station transmission device 3 are in the exchange station building, and the subscriber-side transmission device 4 and the intra-station transmission device 3 are connected by optical fibers 5 and 5 '. The intra-station transmission device 3 is equipped with a large number of optical transmission / reception units for a large number of subscribers, but in this figure, only an optical transmission / reception unit for one subscriber is drawn. The signal goes back and forth through different optical fibers, but in order to cope with the failure of the optical fiber 5, two spare optical fibers 5'are used, for a total of four, and a transmission system for one subscriber is secured. Will be. . In addition, it is also considered that the same optical fiber is used for round trip communication by changing the round trip communication wavelength. In that case, a total of two working optical fibers and one spare optical fiber are used for the transmission system of one subscriber. In the following description, this case will not be mentioned, but the present invention can be applied to this case as well.

The arrows in the figure represent the signal transmission direction. Further, the two round-trip optical fibers are connected to the optical transmission / reception units 3-1 and 4-1 in the intra-station transmission device 3 and the subscriber-side transmission device 4. The optical transmitter / receiver unit has one semiconductor laser and one light receiving element, and has a function of converting an electric signal into an optical signal and a function of converting an optical signal into an electric signal. The electric signal from the exchange 1 goes into two optical transmission / reception units 3-1 and 3-1 'in the intra-station transmission device 3 and sends out signal light to different optical fibers 5 and 5', respectively. In the subscriber side transmission device,
These two signals are transmitted to the two optical transceiver units 4-1 and 4
Light is received at -1 'and converted to an electrical signal. Only one of the electric signals is selected by the electric switch 4-2 and the subscriber terminal 2 is selected.
Lead to. The signal sent from the subscriber terminal 2 follows the opposite direction.

In principle, the spare optical transceiver unit 3,
1 ′ and 4-1 ′ need not always be operating. The operation may be automatically started by detecting the failure, and the electric switch 4-2 may be switched. Since an electric signal received at the time of a failure is interrupted, both the subscriber-side transmission device 4 and the intra-station transmission device 3 can detect it, so that it is possible to automatically switch to this standby system. Further, a configuration without the electric switch 4-2 is also possible. In that case, the optical transceiver unit 4-
1, 4-1 'are connected in parallel and connected to the subscriber terminal 2. Switching to the backup system is performed by switching the power supply to the backup system device.

In FIG. 3 (A), for the sake of omission, only one subscriber terminal 2 is shown for one transmission system, but generally there are a plurality of subscriber terminals 2. Therefore, the signals passing through one optical fiber are multiplexed. The method is I
SDN (Integrated Serve Digital Network)
Time-division multiplexing, which is being considered as part of the vices Digital Network) is influential. At this time, the subscriber side terminal device 4 is required to have a function of distributing data from the multiplexed received signals and a function of multiplexing data from a plurality of terminals and sending the data to the station side, but they are omitted in the figure. .. Similarly,
The station side also multiplexes and demultiplexes signals, which is performed in the exchange 1.

In FIG. 3B, the remote transmission device 7 is located outdoors or inside a building and is wired from there to a subscriber's house with a metal cable. This remote transmission device 7 is shown in FIG.
Like the subscriber-side transmission device 4, the transmission device is placed on the opposite side of the intra-station transmission device 3 across the optical fiber transmission line. Therefore, in the description of the present application, it is regarded as the transmission device on the subscriber side. Similar to FIG. 3A, the intra-station transmission device 6 and the remote transmission device 7 are connected by four optical fibers. Exchange 1
The electrical signals addressed to the plurality of subscribers from the multiplexer 6-2
The optical transmission / reception unit 6-1 converts the optical signal into an optical signal and outputs the optical signal to the optical fiber 5. This optical signal is converted into an electric signal by the optical transmission / reception unit 7-1 in the remote transmission device 7, and the multiplexed signal is further separated by the multiplexer 7-2, and the electric signal is sent to the subscribers there. Is sent.
The signal from the subscriber terminal 2 is transmitted in the reverse order of the exchange 1
Be transmitted to. That is, the signal is multiplexed by the multiplexing device 7-2 in the remote transmission device 7, the signal is separated by the multiplexing device 6-2 in the intra-station transmission device 6 through the optical fiber 5, and reaches the exchange 1. Both multiplexers 6-2, 7-2
Has two units, a working unit and a spare unit.
Detects signal interruption and switches from active to standby. As a result, both the optical transceiver unit and the optical fiber are switched to the standby system. Even in this case, as in the case of FIG. 3A, there is a case where a signal addressed to one subscriber is multiplexed (for example, NTT INS 64).

[0009]

As described above, FIG. 3 (A)
The standby system switching method described in (B) is a reliable method because all the transmission devices and transmission paths are duplicated, but there is a problem that equipment costs are required.

Next, the standby system switching at the time of trouble transfer of the optical cable will be described. Obstacle relocation is to change the laying route for the cable in service due to road construction or other reasons. When replacing the cable, it is necessary to disconnect the optical fiber transmission line once, which inconveniences the subscriber. However, if the signal disconnection time due to this switching is about 10 milliseconds or less, loss of information can be avoided by the retransmission function of the transmission device. Therefore, a method for performing high-speed synchronous switching at two optical fibers was developed. Has been done. This technique is described in the following paper. (Hideo Kobayashi et al .: "Design and characteristics of core switching system using optical multi-core connector", IEICE Transactions BI, vol. J74-BI, No8, pp. 6
28-638 (1991) However, this technique has a problem of inefficiency because the worker needs to go to the site to perform the construction. Therefore, a method of installing a high-speed switch in the transmission line in advance and switching to the standby system when necessary is being studied. However, in this method, switches are installed in all optical fiber lines. There is a drawback that the construction cost is higher than the method described in.

On the other hand, even in the conventional method shown in FIGS. 3 (A) and 3 (B), if the spare system of the optical fiber is made to pass through the optical cable of another route in advance, the switching to the spare system including the transmission device is performed. It is possible to deal with trouble transfer by performing at high speed. Also, when updating the transmission device, it can be dealt with by switching to the standby system. However, as described above, the transmission device also requires the same number of spare systems as the active system, which causes a problem of increased equipment cost.

The present invention provides a standby system switching method in a subscriber transmission system which can solve this cost problem by reducing the backup system of the transmission device.

[0013]

In order to solve this problem, according to the present invention, a controllable optical fiber main wiring rack by a computer is provided between an intra-station transmission device and an optical fiber transmission line, and a switching function of an exchange is provided. And the switching function of the optical fiber main wiring rack can be used together to switch to the standby system in the intra-station transmission device, and the switching function of the optical fiber main wiring rack and the switching function of the transmission device side on the subscriber side can be used to switch the optical fiber transmission line. It is configured to enable switching to the standby system.

[0014]

By adopting such means, the number of standby systems in the intra-station transmission device can be made much smaller than that of the active system without impairing the function of switching to the standby system. If the system outside the office (that is, the optical fiber transmission line and the transmission device on the subscriber side) is not provided with a spare, only the switching to the spare system in the intra-station transmission device is performed. When the backup system is prepared only for the transmission line in the system outside the station, the preliminary switching operation can be performed simultaneously for the intra-station transmission device and the transmission line.
Further, when the backup system is also prepared in the transmission device on the subscriber side, the standby switching operation can be simultaneously performed for all systems of the intra-station transmission device and the transmission path, and the transmission device on the subscriber side. .. Specific contents will be described below based on the embodiments.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A is an explanatory view of the first embodiment of the present invention. This is a case where the form of the transmission path is the same as that shown in FIG. 3A as a conventional example. In FIG. 3A, it was necessary to install the standby system in the intra-station transmission device in pairs with the active system, but in this embodiment, one standby system is provided for a plurality of active systems. In the figure, only the transmission line (optical fiber) for one subscriber is drawn. In the figure, the optical fiber main wiring rack 9
Has a role of connecting the optical cable and the transmission device, and connects the optical fibers 5 and 5'in the optical cable with the optical fibers from the optical transmitting and receiving modules by a connector. Conventionally, the connection change in the optical fiber main wiring rack is manually performed, but in the present invention, it is an automated device controlled by a computer. This device is, so to speak, a large-scale matrix optical switch and can take various forms. An example is described in the following literature. [T. Katagiri et al:
"Non-blocking 100 × 100 Optomechanical M
atrix Switch for Subscriber Networks ", Pro
ceedings of the40th lnternational Wire and Cabl
e Symposium, November 18-21, 1991, Ne
w Jersey, USA, pp. 285-290. The switching control device 10 in the figure is a device for implementing the standby system switching method of the present invention, and also manages the data of the transmission system necessary for this operation. The control signal line 11 shown by a thick broken line in the figure is a signal line for enabling the switching operation. If a failure occurs, the switch 1 and the optical fiber main wiring rack 9 are interlocked and switched to the standby system without specifying the failure position. Further, the subscriber side transmission device 4 is also switched to the standby system. In the figure, the broken line shown in the exchange 1 and the optical fiber main wiring rack 9 represents the switching state to the standby system. In order to automatically perform the switching within the station, the signal interruption detected by the intra-station transmission device 3 is transmitted to the switching control device 10 of the optical fiber main wiring rack 9 and the exchange 1, and each operates based on this. To do it. In this embodiment, the intra-station transmission device 3
The switching control device 10 receives the signal interruption information from the optical fiber main wiring rack 9 and the exchange 1 and sends a switching operation command. Further, the subscriber side transmission device 4 is also automatically switched based on the interruption of the transmission signal. Since the exchange 1 is originally provided with a switching function, only changing the program is required to enable the operation of this exchange. When the trouble transfer is performed in this embodiment, first, the spare optical fiber 5'and the spare optical transmission / reception unit 3-1 are connected by the optical fiber main wiring rack 9, and then the switching equipment 1 switches at high speed. The subscriber transmission device 4 also automatically switches to the standby system due to a signal interruption on the side of the active system.

In this embodiment, the CT- of FIG.
It can also be applied to the RT system. FIG. 1B is an example.
In this case, in the intra-station transmission device 6, the optical transmission / reception unit 3
It is possible to reduce the number of spare systems by sharing the spare system for the multiplexer 6-2 as well as -1. Further, in the figure, the remote transmission device 7 is similar to the conventional method of FIG. 3 (B). Also in this case, when the remote transmission device 7 is installed in a building, a plurality of remote transmission devices 7 can be provided. Therefore, similarly to the intra-station transmission device 6, a method in which a plurality of active systems share a standby system can be adopted. In that case, a device having the same function as that of the optical fiber main wiring rack 9 in the station is provided in the preceding stage of the optical transmission / reception unit 7-1 of the remote transmission device 7, or the optical transmission / reception unit 7-1 and the multiplexing device 7-. An electric switch may be inserted between the two.

FIG. 2A shows another embodiment, which is different from FIG. 1A only in the subscriber side transmission device 4. Figure 1
By the same procedure as in the embodiment of (A), it is possible to deal with failure recovery and trouble transfer. Instead of duplicating the optical transmission / reception unit 4-1, two optical couplers 12 are inserted so that a single optical transmission / reception unit 4-1 can receive light from two paths at the same time and can simultaneously transmit light. I have to.
The light from the station does not arrive from the two paths at the same time, but the light to the station is sent to the two paths at the same time. However, the station receives only the light of one path. In this example,
Since the intensity of the received light is reduced by half, the restriction on the transmission distance becomes large, and the optical transceiver unit 4-1 on the subscriber side.
Although there is a drawback that it is not possible to deal with the standby system switching at the time of failure, there is an advantage that it is inexpensive and an electronic circuit for detecting the signal interruption and the standby system switching is unnecessary.

In principle, application to the CT-RT system is also possible, and FIG. 2B shows an embodiment thereof. In this case, it is premised that the failure rate of the multiplexing device 7-2 in the remote transmission device 7 is sufficiently small.

In the above description of the present invention,
The optical fiber transmission line has been premised on the fact that the working and spare are 1: 1. However, if the optical matrix switch is inserted in the middle of the optical fiber transmission line, the number of spares may be reduced. In addition, there may be a mode in which more optical switches are inserted in order to increase the degree of freedom in changing the route.
In that case, since a spare transmission line is not formed at the moment of failure occurrence, the inserted switch is switched to form a spare transmission line other than the working line that leads from the station to the subscriber side transmission device. Thus, the present invention can be implemented.

[0020]

As described above, according to the present invention, since the switching function is provided in the switchboard and the optical fiber main wiring rack, the number of standby systems of the intra-station transmission device can be reduced without impairing the reliability. The construction cost of the subscriber optical transmission system can be reduced. In the current optical transmission system for subscribers, a large proportion of leased lines do not require operation in a switch, but if broadband ISDN becomes widespread in the future,
Since almost all services including moving image services will be performed through the exchanges, the applicability of the present invention will spread greatly in the future, and can greatly contribute to the introduction of large-scale optical transmission systems in the future.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention when (A) is applied to an FTTH system and (B) is applied to a CT-RT system.

FIG. 2 is a block diagram of the second embodiment of the present invention when (A) is applied to the FTTH system and (B) is applied to the CT-RT system.

FIG. 3 is a principle diagram of a preliminary switching system that has been studied conventionally, (A) is a block diagram when applied to an FTTH system, and (B) is a block diagram when applied to a CT-RT system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 exchange 2 subscriber terminal 3 intra-station transmission device 3-1 transmission / reception unit 3-1 'spare optical transmission / reception unit 4 subscriber side transmission device 4-1 optical transmission / reception unit 4-1' spare optical transmission / reception unit 4-2 electric switch 5 Optical fiber 5'Spare optical fiber 6 Intra-station transmission device 6-1 Optical transmission / reception unit 6-1 'Spare optical transmission / reception unit 6-2 Multiplexing device 7 Remote transmission device 7-1 Optical transmission / reception unit 7-1' Spare Optical transmission / reception unit 7-2 Multiplexing device 8 Metal cable 9 Optical fiber main wiring frame 10 Switching control device 11 Control signal line 12 Optical coupler

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryoichi Yamamoto 1-1-6, Saiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (3)

[Claims] 1. An exchange, an intra-station transmission device which is connected to the exchange by an electric communication cable and which mutually exchanges an electric signal and an optical signal by an optical transmission / reception unit, and an optical signal side of the intra-station transmission device, which is a station side. Optical subscription having an optical fiber cable transmission line to which one end is connected and a subscriber side transmission device to which the other end of the optical fiber cable transmission line on the subscriber side is connected to perform mutual conversion between an optical signal and an electrical signal In the personal transmission system, a small number of spares are provided for the plurality of optical transmission / reception units of the intra-station transmission device, and a spare system is provided for each of the optical fiber transmission line and the subscriber-side transmission device. A plurality of optical transceiver units and the spare are configured to be selected by an optical fiber main wiring rack and connected to the optical fiber transmission line, and the optical fiber main wiring rack is used as a switching command. When the spare of the optical transmission / reception unit is selected, it is possible to switch to the spare system in the intra-station transmission device by using the switching function of the exchange together, and the switching function to the spare on the subscriber side transmission device side enables By enabling the switching of the optical fiber transmission line to the standby system, it is possible to automatically perform switching between the switch and the optical fiber main wiring rack, and switching at the subscriber side transmission device. A standby system switching method in an optical subscriber transmission system characterized by being configured. 2. The switching command is configured to be issued based on signal interruption information in the intra-station transmission device when a failure occurs in the intra-station transmission device or the optical fiber transmission line. A standby system switching system in the optical subscriber transmission system according to item 1. 3. A standby system switching system in an optical subscriber transmission system according to claim 1, wherein the standby system of the subscriber side transmission device is connected in parallel with the working system on the electric signal side. ..