JPH11275008A - Optical transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmitter that is not affected by the reliability of an optical switch. SOLUTION: An output of optical amplifiers 2-1 to 2-7 of an active system connects to an input terminal of optical splitters 3-1 to 3-7 and an output of an optical amplifier 2-8 of a standby system connects to the other input terminal, via an optical selection switch 4. At the occurrence of a fault in any of the optical amplifiers 2-1 to 2-7 of the active system, the faulty optical amplifier is stopped, and the optical selections witch 4 causes an output of the standby system making pairs with the output of the faulty amplifier to be selected. Thus, the output of optical amplifier 2-8 of the standby system connects to the post-stage optical splitters via the optical selection switch 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission apparatus for distributing an optical signal to a plurality of optical lines, and more particularly to an optical transmission apparatus having a duplex system including a normal system and a standby system. .

[0002]

2. Description of the Related Art In an optical communication system or the like, a duplex configuration of an optical signal processing device and an optical / electrical conversion device is an essential function for ensuring the reliability of the system. Switching of the electrical circuit device to the standby system can be easily performed with an electrical switch, but the optical signal cannot be switched unless the optical path is physically changed, so extra light loss is allowed. Then, two optical signals called an optical coupler are
It is common practice to connect standby systems in parallel by using optical components that multiplex with these lines. FIG. 3 shows a conventional optical transmission device having a duplex configuration. This optical transmission device is an example of a configuration in which a spare transmission device is relatively inexpensive, and a standby (standby) transmission device is compared to a normal (working) transmission device 20-1 to 20-8. A double configuration in which 23-1 to 23-8 are prepared one by one is adopted. The optical couplers 21-1 to 21-8 used at this time are of the type of two inputs and one output (hereinafter referred to as 2 × 1). The transmission devices 20-1 to 20- are connected via the optical couplers 21-1 to 21-8.
8 or 23-1 to 23-8 are output from the terminal transmission device 2
2-1 to 22-8.

FIG. 4 shows another example of an optical transmission device having a duplex configuration. This optical transmission device is a configuration example in a case where a spare transmission device is expensive, and includes a plurality of normal transmission devices 20-1 to 20-2.
One backup transmission device 23 is prepared for 0-8,
The transmission device 23 is shared. In this case, 2 × 1 optical switches 25-1 to 25-8 are used for switching between the normal transmission devices 20-1 to 20-8 and the backup transmission device 23. No 2x1 optical coupler is used as in the full duplex configuration of FIG. This is because the loss due to the optical coupler is high, and the 1 × 8 optical selection switch 24 is necessary for the configuration, so that it is easier to configure using an optical switch having the same mechanism. Each 2 × 1 optical switch 25-1 to 2
The input of the spare device 5-8 is selectively connected to the common spare device 23 via the optical selection switch 24. In the configuration in which the standby device 23 is shared as shown in FIG. 4, it is not possible to cope with a case where a plurality of normal devices 20-1 to 20-8 fail simultaneously. However, if the probability of failure per unit is sufficiently low, (r ² is a single failure rate in two When r) the probability of two devices fail simultaneously is made very low, so there is no practical problem .

In general, an optical splitter is a passive optical component and does not require a driving circuit unlike an active optical element such as an optical switch. On the other hand, since the optical power is distributed to the unused output ports, there is a drawback that the loss of light is inevitable in principle. For example,
In a Y-shaped 2 × 1 optical coupler, when used as two inputs and one output, if it is configured symmetrically with respect to two inputs, 50% of each input is output to the output port. That is, a loss of 3 dB cannot be avoided in principle. Therefore, in a system configuration in which light loss is to be avoided, 2 × 1 optical couplers 21-1 to 21-21 as shown in FIG.
8, 2 × 1 optical switches 25-1 to 25-2 as shown in FIG.
5-8 are used.

[0005] An optical transmission device having a duplex configuration actually used is found in, for example, an optical amplifier module shown in FIG.
This optical amplifier module is used in a video signal distribution system for CATV services and the like, and amplifies optical signals obtained by multiplexing video signals with optical amplifiers 27-1 to 27-8.
The signals are distributed by the optical splitters 28-1 to 28-7 and transmitted to each terminal. The optical amplifiers 27-1 to 27-8 are used to compensate for optical signal branch loss caused by the optical splitters 28-1 to 28-7. The optical amplifiers 27-1 to 27-8 are, for example, erbium-doped optical fiber amplifiers and use laser diodes as pumping light sources, so that the probability of failure is relatively high. Also, since the amplifier itself is expensive, FIG.
Is adopted.

In the configuration shown in FIG. 5, an input signal is first divided into eight signals by a 1 × 8 optical splitter 26,
6 are amplified by the optical amplifiers 27-1 to 27-8, respectively. The amplified signal is a 2 × 1 optical switch 25−
Optical splitters 28-1 to 28- through 1 to 25-7
7 and distributed to each receiving terminal. The optical amplifier 27-8 is a standby device, and its output is connected to 2 × 1 optical switches 25-1 to 25-7 in parallel with the outputs of the optical amplifiers 27-1 to 27-7 via the 1 × 8 optical selection switch 24. It is connected. Normally, the output of the optical amplifier 27-8 is 1 × 8
Although connected to the non-reflection optical terminal 29 by the optical selection switch 24, the seven normal optical amplifiers 27-1 to 27-7 are used.
For example, when a failure occurs in the optical amplifier 27-1, the 1 × 8 optical selection switch 24 and the 2 × 1 optical switch 25
The output from the normal system optical amplifier 27-1 is switched to the standby system optical amplifier 27-8 in conjunction with -1.

In the configuration shown in FIG. 5, the 2 × 1 optical switch 2 is used for switching between the normal system and the standby system instead of using the 2 × 1 optical coupler.
5-1 to 25-7 are used because it is necessary to avoid light loss. 2 × 1 as optical switch
Although seven optical switches and one 1 × 8 optical selection switch are used, the 1 × 8 optical selection switch 24 is actually a 1 × 8 optical selection switch.
It is configured by cascading two optical switches in three stages, and a total of 14 1 × 2 optical switches are used. The 1 × 2 optical switch and the 2 × 1 optical switch basically mean the same element.

The optical transmission device for video distribution shown in FIG. 5 is a one-way signal transmission to a terminal transmission device. However, an optical splitter is used to transmit a signal between one main transmission device and a plurality of terminal transmission devices. There are also systems that send and receive signals in different directions. Also in this case, there may be a duplex configuration in which one normal transmission device is shared by a plurality of normal transmission devices. FIG. 6 shows an example in which the subscriber circuit is duplicated in the digital optical subscriber transmission system. Each transmission device (subscriber circuit) 20-1 of the normal system
Up to 32 terminal transmission devices 22 are connected to .about.20-8 via optical splitters 30-1 to 30-8. The transmission and reception of signals are performed one-to-one with each terminal transmission device 22 with a time interval. In the meantime, signals transmitted from the main transmission devices 20-1 to 20-8 are related to transmission and reception of signals connected to the same optical splitters 30-1 to 30-8 as the terminal transmission device 22 which transmits and receives signals. Other terminal transmission device 2 without
2, but it does not pose a problem because it is designed so that only specific terminals can receive it after encryption. FIG.
In this example, a standby transmission device (subscriber circuit) 23 is connected to an eight-channel optical selection switch 24, and each output of the eight channels of the optical selection switch 24 is combined with the output of each normal-system subscriber circuit in 2 × 1 light. The switches 25-1 to 25-8 are connected to two inputs, and the output thereof is connected to the optical splitter 3.
0-1 to 30-8.

[0009]

As described above,
In a conventional optical transmission device having a duplex configuration, 2 × 1 optical switches 25-1 to 25-8 are used for switching and connection between a backup transmission device and a normal transmission device. This is because the configuration of the switch is changed by using the technology of the optical waveguide switch.
The same applies to a switch in which an h selection switch and a 2 × 1 optical switch are integrated. The same configuration is always taken internally. The normal transmission devices 20-1 to 20-8 are connected to the optical splitters 30-1 to 30-8 via the 2 × 1 optical switches 25-1 to 25-8. 1 to 25-8 are usually devices 20-1 to 20-
8 must be incorporated in the system in advance. In other words, the normal transmission device 20-1
20-8, the failure of the backup transmission device 23 is 2
It can be replaced using the functions of the × 1 optical switches 25-1 to 25-8, but the 2 × 1 optical switches 25-1 to 25-8 can be replaced.
25-8 itself cannot be replaced while the communication service is continued.

If the optical switch is composed of individual components and each can be removed one by one, the number of terminals that lose service during replacement is limited to the terminals connected to the switch. Optical switches are integrated and mounted so that about ten transmission devices can be switched at a time. Therefore, if a failure occurs in the optical switch and the optical switch must be replaced, all the terminals connected to the transmission device sharing the backup device will be affected. In reality, it is not permissible to interrupt communication services for such a large number of terminal transmission devices, so that extremely high reliability is required for the optical switch. However, it is extremely difficult to guarantee the reliability of an active element such as an optical switch for, for example, about 20 years as long as the service life of a transmission device. As described above, in the conventional optical transmission device having the duplex configuration, when the 2 × 1 optical switch is used for switching between the standby system and the normal system, there is a problem that the 2 × 1 optical switch cannot be replaced. The present invention has been made to solve the above-described problem, and has as its object to provide an optical transmission device that is not affected by the reliability of a 2 × 1 optical switch.

[0011]

According to a first aspect of the present invention, there is provided an ordinary transmission device, a standby transmission device, and an optical splitter, and a plurality of optical signals are transmitted using the optical splitter. The optical splitter has two input terminals, one of the input terminals is connected to the output of the normal transmission device, and the other input terminal is connected to the output of the standby transmission device. Are connected. Since the optical splitter always has at least two input terminals, the output of the normal transmission device is connected to one input terminal, and the output of the standby transmission device is connected to the other input terminal. With such a configuration, no optical components are inserted between the normal transmission device and the optical splitter connected to the transmission device. In addition, as described in claim 2, a plurality of the normal transmission devices and a plurality of the optical splitters corresponding thereto are provided, and between the output of the backup transmission device and the plurality of optical splitters. , An optical selection switch for selecting any of the remaining input terminals of each optical splitter. As described above, when a plurality of normal transmission apparatuses share a standby transmission apparatus, an optical selection switch is provided between the output of the standby transmission apparatus and the plurality of optical splitters.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] Next, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1A is a block diagram of an optical transmission device according to a first embodiment of the present invention. The optical transmission device of the present embodiment
This is an optical amplifier module for an optical video distribution system, which distributes one system of optical input into seven, amplifies and outputs the same with an optical amplifier, and replaces the conventional configuration shown in FIG. 5 with the configuration according to the present invention. .

The input section of this optical amplifier module is composed of an optical splitter 1 having two inputs and eight outputs (hereinafter referred to as 2.times.8). One input terminal of the optical splitter 1 is provided with a normal transmission system (not shown). An optical output of a device (such as an optical transmission device or an optical amplifier) is input. The other input terminal receives an optical output of an unillustrated backup transmission device (such as an optical transmission device or an optical amplifier).

Each output of the 2 × 8 optical splitter 1 is amplified by each of the optical amplifiers 2-1 to 2-8, and the output of the standby optical amplifier 2-8 is connected to the input of the 1 × 8 optical selection switch 4. Is done. The 1 × 8 light selection switch 4 selects one of the eight outputs and connects the selected output to the input. One of the eight outputs of the light selection switch 4 is connected to the non-reflection light terminal 5.

The output of the optical amplifier module shown in FIG. 1A has seven systems, each system being a normal system optical amplifier 2-1 to 2-7.
And each output excluding the non-reflection optical terminal output of the light selection switch 4. Each output of these seven systems is a 2 × 8 optical splitter 3-1 similar to the splitter 1.
The signal is output to a subsequent transmission device (terminal optical receiving device, optical amplifier, or the like) via 3-7 (3-2 to 3-6 are not shown).

The operations of the optical amplifiers 2-1 to 2-8 and the 1 × 8 optical selection switch 4 are managed by a management system (not shown) (upper computer). Optical amplifier 2-1
A part of the output of 2-8 is branched by an optical coupler or the like (not shown), monitored by a photodetector or the like, and reported to the management system. Therefore, the optical amplifiers 2-1 to 2-8
Is automatically identified by the management system, and the stop of the apparatus and the switching of the selection switch 4 are automatically and promptly performed.

FIG. 1B is a block diagram of the 2 × 8 optical splitter 1. The 2 × 8 optical splitters 3-1 to 3-1
The configuration is the same for 3-7. In principle, the 2 × 8 optical splitter 1 has two inputs and two outputs (hereinafter, 2 × 2
) Are cascaded and combined in multiple stages, and there are always two inputs. Even in a configuration in which one system of optical input is distributed in a Y-shape at the first stage as in the related art, this configuration basically uses one of the two inputs of the 2 × 2 optical coupler. It is equivalent to the exclusion.

As described above, the 2 × 8 optical splitters 1, 3
Since -1 to 3-7 always have two inputs, one of them is connected to the output of the normal transmission device and the other is connected to the output of the backup transmission device. This is the configuration method of the optical transmission device of the duplex configuration provided by the present invention.

Next, the operation of the above-described optical transmission device will be described. Normally, the 1 × 8 optical selection switch 4 selects an output connected to the non-reflection optical terminal 5 under the control of the management system. Therefore, the optical output of the standby optical amplifier 2-8 is transmitted to the non-reflection optical terminal 5 via the 1 × 8 optical selection switch 4.
Are output to the 2 × 8 optical splitters 3-1 to 3-7 as outputs of the standby system. Thus, each output of the normal optical amplifiers 2-1 to 2-7 is transmitted to the subsequent stage.

Next, when a failure occurs in one of the normal-system optical amplifiers 2-1 to 2-7, for example, the optical amplifier 2-1, the management system determines that the failed optical amplifier 2-1 has failed. Is stopped, and the 1 × 8 optical selection switch 4 selects the standby system output paired with the output of the optical amplifier 2-1. Thus, the optical output of the standby optical amplifier 2-8 is output to the subsequent 2 × 8 optical splitter 3-1 via the 1 × 8 optical selection switch 4.

The 2 × 8 optical splitter 3-1 divides the optical input into eight in the same manner as when the normal system optical amplifier 2-1 was operating. As described above, after switching the output to the standby system, the failed normal optical amplifier 2-1 is repaired or replaced with a normal one. After the repair, the 1 × 8 optical selection switch 4 is made to again select the output to the non-reflection optical terminal 5, and the repaired optical amplifier 2-1 is operated. Thereby, the processing at the time of failure ends.

In the optical transmission device of the duplex configuration according to the present invention, a device between the normal system (optical amplifiers 2-1 to 2-7) and the optical splitters 3-1 to 3-7 connected to the device are connected.
No optical components are inserted. The output of the 1 × 8 light selection switch 4 for switching between the standby system device (optical amplifier 2-8) and the normal system device is connected to the other inputs of the optical splitters 3-1 to 3-7. Have been.

Therefore, even if a failure occurs in the standby system device or the optical selection switch 4, while the normal system device is operating normally, the failure does not affect the transmission service by the normal system at all. The spare device or the optical selection switch 4 can be replaced and updated. In addition, the optical selection switch 4 is updated to a higher-performance one, or the spare optical amplifier 2-8 is changed according to a change in the setting of the failure rate.
It is also possible to increase the optical selection switch 4 to n × 8 by increasing the number of devices from one to n, without interrupting the communication service. Thereby, it is possible to cope with a case where a plurality of normal devices break down.

Further, since the 2 × 1 optical switch is not inserted in the normal system, there is no need to consider the reliability of the optical switch, and the optical selection switch 4 used in the standby system has a direct effect on the normal system. Therefore, there is no need to require the optical selection switch 4 to have high reliability.

Further, because of the above-mentioned configuration, the standby system and the optical selection switch 4 can be added later without providing the transmission service at the beginning of the transmission service. A laser diode having a relatively short life as a component of an optical transmission device usually increases the probability of failure according to the accumulated operation time. Therefore, the probability of failure is low in the beginning, and there is a case where it is not necessary to prepare a standby system depending on the setting of the failure probability of the system. In such a case, after a certain number of years, by adding a spare system for the first time when the failure rate of the system exceeds the specified value, unnecessary investment in equipment can be prevented and the price of the transmission system can be reduced. Can be suppressed.

Further, the optical splitters 1,3-1 to 3-
The second stage 2 × 2 optical coupler 6 functions as a 2 × 1 optical coupler for connecting the optical output of the normal system and the optical output of the standby system, and also distributes the optical input to two outputs.
Since it functions as a × 2 optical splitter, there is no difference in optical loss as compared with the conventional case in which the standby system and the normal system are switched by a 2 × 1 optical switch and connected to the optical splitter.

As described above, in the connection between the standby system and the normal system using the optical coupler, a branch loss of 3 dB is generated as compared with the case where an optical switch is used, and the insertion loss is increased in principle. In an optical transmission device having a redundant configuration, 2 × 1 optical couplers used for connection between the standby system and the normal system are provided in two.
Since it is shared with the first stage of the × 8 optical splitters 1,3-1 to 3-7, unnecessary branch loss does not occur.

[Embodiment 2] FIG. 2 is a block diagram of an optical transmission apparatus showing a second embodiment of the present invention. The optical transmission device of the present embodiment constitutes a part of a digital optical subscriber transmission system, and is obtained by replacing the conventional configuration shown in FIG. 6 with the configuration according to the present invention.

In the present embodiment, the normal transmission device 10
-1 to 10-8 are provided, and eight 2 × 8 optical splitters 11-1 to 11-8 (11
-2 to 11-7 are not shown). The output of the backup transmission device 13 is connected to the input of the 1 × 8 optical selection switch 14.

Each output of the normal transmission devices 10-1 to 10-8 and each output of the optical selection switch 14 form a pair and are connected to the corresponding 2 × 8 optical splitters 11-1 to 11-8. The configuration of the 2 × 8 optical splitters 11-1 to 11-8 is the same as that of the first embodiment, and the output of the corresponding transmission device 10-1 to 10-8 is connected to one input terminal. A corresponding output of the light selection switch 14 is connected to one input terminal. And each of the optical splitters 11-1 to 11-1
Each output of 11-8 is connected to each terminal transmission device 12.

Next, the operation of the above-described optical transmission device will be described. Normally, the standby transmission device 13 stops operating under the control of a management system (not shown). Accordingly, each output of the normal transmission devices 10-1 to 10-8 is transmitted to the 2 × 8 optical splitters 11-1 to 11-8,
The signals are distributed to the terminal transmission devices 12 by the optical splitters 11-1 to 11-8.

Next, the normal transmission devices 10-1 to 10-
8, for example, when a failure occurs in the transmission device 10-1, the management system determines that the transmission device 1 in which the failure has occurred.
0-1 is stopped to operate the standby transmission apparatus 13 and to cause the 1 × 8 optical selection switch 14 to select the standby output paired with the output of the transmission apparatus 10-1. In this way, the optical output of the backup transmission device 10-1 is transmitted via the 1 × 8 optical selection switch 14 to the subsequent 2 × 8 optical splitter 11.
-1 is output. In this way, a failure can be dealt with.

In the optical transmission device having a duplex configuration according to the present invention, the transmission devices 10-1 to 10-8 of the normal system and the optical splitters 11-1 to 11-8 connected to the transmission devices 10-1 to 10-8 connected behind the transmission devices 10-1 to 10-8 are connected.
No optical components are inserted. 1 × 8 for switching between the standby transmission device 13 and the normal transmission device.
The output of the optical selection switch 14 is the optical splitter 11-1.
11-8 are connected to the other inputs.

Therefore, even if a failure occurs in the standby transmission device 13 or the optical selection switch 14, while the normal transmission devices 10-1 to 10-8 are operating normally,
It is possible to replace and replace the faulty standby transmission device 13 or optical selection switch 14 without affecting the transmission service of the normal system at all. In addition, the optical selection switch 14 is updated to a higher performance one, or the number of backup transmission devices 13 is increased from one to two in accordance with a change in the setting of the failure rate, and the optical selection switch 14 is changed to 2 × 8. The scale can be increased without interrupting the communication service.

[0035]

According to the present invention, the output of the normal transmission device is connected to one input terminal of the optical splitter, and the protection transmission device is connected to the other input terminal. By connecting the output, no optical components are inserted between the normal transmission device and the optical splitter connected behind it. Therefore, it is not necessary to consider the reliability of the 2 × 1 optical switch.

Further, since the optical selection switch is provided between the output of the standby transmission device and the optical splitter as described in claim 2, it is assumed that a failure occurs in the standby transmission device or the optical selection switch. In addition, while the normal transmission device is operating normally, the faulty standby transmission device or the optical selection switch can be replaced and updated without any influence on the transmission service of the normal system. Also, updating the optical selection switch to a higher performance one,
It is also possible to increase the number of spare transmission devices to a plurality of transmission devices along with the change in the setting of the failure rate and to expand the scale of the optical selection switch accordingly, without interrupting the communication service.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical transmission device having a duplex configuration and a block diagram of a 2 × 8 optical splitter according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an optical transmission device having a duplex configuration according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a conventional optical transmission device having a duplex configuration.

FIG. 4 is a block diagram of a conventional optical transmission device having a duplex configuration.

FIG. 5 is a block diagram of an optical amplifier module for an optical image distribution system, which is an example of a conventional optical transmission device having a duplex configuration.

FIG. 6 is a block diagram of a digital optical subscriber transmission system that is an example of a conventional optical transmission device having a duplex configuration.

[Explanation of symbols]

1, 3-1 to 3-7, 11-1 to 11-8... 2 × 8 optical splitter, 2-1 to 2-8... Optical amplifier, 4, 14.
× 8 light selection switch, 5: non-reflection termination, 6: 2 × 2 optical coupler, 10-1 to 10-8: normal transmission device, 1
2 ... terminal transmission device, 13 ... stand-by transmission device.

Claims (2)

[Claims] 1. An optical transmission device comprising a normal transmission device, a backup transmission device, and an optical splitter, and distributing an optical signal to a plurality of optical lines using the optical splitter, wherein the optical splitter has two An optical transmission device comprising an input terminal, wherein one output terminal is connected to an output of a normal transmission device, and the other input terminal is connected to an output of a standby transmission device. 2. The optical transmission device according to claim 1, further comprising a plurality of said normal transmission devices and a plurality of said optical splitters corresponding thereto, wherein an output of said backup transmission device and a plurality of optical splitters are provided. An optical selection switch for selecting any one of the remaining input terminals of each optical splitter.