JPH09181685A - Communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means substituting an on-land communication channel on the occurrence of a disaster. SOLUTION: Large capacity optical fiber cables 10 are installed on sea bottom so as to circulate the main island, Kyusyu and Shikoku in Japan and each base station provided to each urban and rural prefecture and the optical cable 10 are connected by each branch fiber 12. The circulating length of the optical fiber cable 10s nearly 4,000km and an optical repeater is integrated in the cable at a proper interval. The optical fiber cable 10 is made up of four single mode optical fibers and the two of the fibers are used usually and the remaining two fibers are spare fibers. A specific optical wavelength is assigned to each base station signals of each optical wavelength are sent through the optical fiber cable 10. The signals of each optical wavelength are circulated in the cable 10 by the wavelength division multiplex system. Each base station receives the optical signal of each wavelength to be sent and demodulates the signal depending on each wave length.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system, and more particularly to a communication system which has a high reliability and a large capacity and is excellent in substitutability in an emergency.

[0002]

2. Description of the Related Art Due to the sophistication of society, communication systems have become very important as a basis of life. Public telephone networks, for example, are ubiquitous and their interruptions have a great negative impact on society. For example, if the communication network is temporarily interrupted due to an artificial disaster, not limited to natural disasters such as earthquakes and typhoons, the effect is to disrupt communication within that area and between that area and other areas. Not only that, it causes social activity to stagnate in those areas.

As means for coping with such a disaster, basically, it is considered to duplicate the related devices, specifically the communication path and the communication device. However, simple duplication is not enough. This is because if the duplicated communication paths or communication devices are placed close to each other, they may be temporarily unavailable.

In recent years, the network of computers has advanced, and local area networks or wide networks have become popular.
It is becoming organized as an area network. If such a computer network is temporarily cut off, it may cause significant stagnation not only in Japan but also globally.

[0005]

The conventional communication path is very vulnerable to, for example, an earthquake, except for the satellite lines, since the major equipment is located on land. This has been verified by the earthquake that occurred in Osaka-Kobe in January of this year. Even a mobile phone cannot be used if the wireless station or the exchange station that bundles these becomes unavailable. In the case of satellite communication, the mobile antenna must be carried to the disaster area, and it takes several days to restore communication.

Further, due to the improvement of computer processing capability, the amount of transmission data such as voice data, image data, and moving image data as well as character data has become enormous. An inexpensive transmission means capable of reliable transmission is desired. So also
A large-capacity one is desired as an alternative communication channel in a disaster area.

The present invention aims to present a disaster-resistant communication system.

Another object of the present invention is to provide a highly reliable and high capacity communication system.

The present invention further aims at presenting a communication system which is significantly more economical than existing ones.

[0010]

According to the present invention, in a communication system in which a plurality of base stations are connected to a communication trunk line (for example, a large-capacity optical fiber cable), a wavelength unique to each base station is assigned and the communication is performed. A transmission line (for example, a transmission line by wavelength division multiplexing) for transmitting a signal of a wavelength assigned to each base station is set on the trunk line. As a result, a large capacity communication path can be secured with a simple configuration. By assigning a unique wavelength to the signal source, the receiving side can determine from which base station the signal is sent without providing the identifier of the source in the transmission signal, and the effective transmission capacity can be increased. .

By using a submarine cable as the communication trunk line, it can be used as an alternative to the land communication path. Further, by making the circuit go around, the processing of the transmitted signal becomes easy.

By preparing a bidirectional trunk line, the time delay can be reduced, and even if one trunk line is cut off, the other trunk line can ensure communication.

By connecting an earthquake measuring device such as a seismograph and an earthquake monitoring device to the optical relay branching device on the seabed and transmitting the earthquake information to the base station, the earthquake information can be efficiently collected. .

Further, the branch fiber connecting the line optical fiber cable and at least the base station serving as the landing station can be made non-relayable, and by making it non-relayable, the installation and operation costs can be reduced. , You can build an economical communication system.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the structure of a communication path in an embodiment of the present invention. In this embodiment, a large-capacity optical fiber cable (main line fiber cable) 10 is used in Honshu, Japan.
Laying on the seabed so as to circulate around Kyushu and Shikoku, and between the base stations provided in each prefecture (about 50 stations in total),
The connection is made with a branch fiber 12 made of an optical fiber having a similar capacity. Specifically, coastal base stations (for example,
32) is a landing station, and base stations in inland prefectures are connected to the optical fiber cable 10 via a landing station nearby. The circumference of the optical fiber cable 10 is about 4,
It is 000 km, and optical repeaters are incorporated at appropriate intervals. The fiber optic cable 10 comprises four single mode optical fibers, two of which are commonly used,
The remaining two are spares.

FIG. 2 is a schematic diagram showing a schematic configuration of this embodiment. As described above, the fiber optic cable 1
The optical fiber 10a of 0 is for counterclockwise (counterclockwise) circulation, and the optical fiber 10b is for clockwise (clockwise) circulation. In this embodiment, the base station 14 (14-1, 1)
4-2, ..., 14-n) assumes about 50. Each base station 14 has an optical fiber 10 via a branch fiber 12 and optical multiplexers / demultiplexers 16a and 16b.
Optically coupled to a and 10b. Branch fiber 1
Reference numeral 2 denotes two optical fibers for transmitting / receiving to / from the optical multiplexer / demultiplexer 16a, and two optical fibers for transmitting / receiving to / from the optical multiplexer / demultiplexer 16b, which has a total of four optical fibers. The branch fiber 12 may be non-repeating, even if it is required, and thus it is possible to reduce the installation and operation costs.

In this embodiment, each base station 14-1, ...
.., 14-n are assigned unique wavelengths [lambda] i, and the optical fiber 10 is transmitted by the wavelength multiplexing method. Although details will be described later, each base station 14-1, ..., 14-n outputs the transmission signal to the optical fiber 10 at the assigned optical wavelength λi. By doing so, since the transmission source can be specified by the wavelength, it is not necessary to add a signal for specifying the transmission source of the communication signal, the processing at the receiving place becomes easy, and the transmission capacity can be effectively used. Further, it is easy to communicate the same contents to a plurality of parties, and there is an advantage that signals of different origins can be simultaneously received and processed at the same destination.

As described above, the optical fibers 10a, 1
Optical repeaters 18a, 18 at appropriate one or a plurality of locations of 0b.
b is installed.

FIG. 3 is a block diagram showing a schematic configuration of the base station 14 and a connection form with the optical fibers 10a and 10b. There are two transmission / reception processing systems, one for clockwise and one for counterclockwise. The signal to be transmitted is input to the input terminals 20a and 20b as an electric signal. Modulation circuit 2
2a and 22b modulate the signals from the input terminals 20a and 20b, respectively, and drive the laser diodes 24a and 24b with the modulated outputs. Laser diode 24
a and 24b emit laser light with a central wavelength λi, and the output light thereof is the transmission optical fiber 40a of the branch fiber 12.
It is applied to the optical multiplexer / demultiplexers 16a and 16b via 40b.

The optical multiplexers / demultiplexers 16a and 16b include optical fiber couplers 50a and 50b and an optical filter 5 for removing only the wavelength λi from the wavelength division multiplexed optical signal from the upstream side.
It consists of 2a and 52b. That is, the optical multiplexer / demultiplexers 16a, 16
b, the optical filters 52a and 52b are the optical fibers 1
0a, 10b from the upstream side, the optical signals of wavelength λi are removed from the wavelength division multiplexed optical signals of wavelengths λ1 to λn, and the optical fiber couplers 50a, 50b are replaced by filters 52a, 52b.
The optical signal from the optical fiber is demultiplexed into the receiving optical fibers 42a and 42b of the branch fiber 12. The optical fiber couplers 50a and 50b also include the transmission optical fibers 40a and 40b.
the optical signal of wavelength λi from the optical fiber 10 on the downstream side.
a and 10b are optically added (that is, wavelength division multiplexing) in the optical transmission direction.

By providing optical filters 52a and 52b for removing the signal of the wavelength λi to be newly multiplexed here in advance on the upstream side of the optical fiber couplers 50a and 50b, the wavelengths to be newly multiplexed are added. It is possible to prevent the optical signal of λi and the optical signal of wavelength λi that has already made one round from overlapping on the optical fibers 10a and 10b.

The optical demultiplexers 26a and 26b separate the optical signals from the receiving optical fibers 42a and 42b into respective wavelengths,
The (n-1) light receiving elements 28a and 28b are the optical demultiplexers 26.
The optical signal of each wavelength separated by a and 26b is converted into an electric signal. The demodulation circuits 30a and 30b independently demodulate the (n-1) light receiving elements 28a and 28b. The (n-1) electric signal outputs of the demodulation circuits 30a and 30b are output to the outside from the output terminals 32a and 32b.

Which of the optical fibers 10a and 10b is used generally depends on the destination. That is, the optical fibers 10a and 10b that reach the destination faster are used.
In applications where the transmission delay time does not matter so much, one of the optical fibers 10a and 10b may be mainly used and the other may be used as a standby or a hot standby. That is, basically, the present embodiment can operate with only the optical fiber 10a or the optical fiber 10b.

When outputting the same signal to the optical fibers 10a and 10b, each base station 14 may receive the information of the same contents before and after the time. In this embodiment, the base station 14 on the receiving side uses the time information added to the received information.
Examine the stamp and proceed as follows: In other words, if there are too many transmission errors at the same time stamp that the information received earlier needs to be retransmitted, if the retransmission has not been requested yet, the information received later is fetched and the retransmission has already been requested. Sometimes, the information received later is taken in and the resend request is discarded. If the previously received information with the same time stamp is correctly understood, the later received information is discarded. As a result, it is possible to efficiently avoid the trouble of retransmission and duplication of information.

A frame (packet, cell, etc.) for transmitting the optical fiber cable 10 has a structure as shown in FIG. 4, for example. That is, a start flag is provided at the beginning, and after that, a destination address that identifies the destination base station 14, a time stamp that indicates the transmission time of the transmission source, a frame number that indicates the order of a series of frames, and a fixed length. The header containing the amount of data in the case and the data body are followed, and the stop flag is placed at the end. In the case of fixed length, the stop flag may be omitted. The frame number may be omitted when the data retransmission function for the reception failure due to data loss or transmission error is not required. It is obvious that the data body may include an error detection / correction code.

The optical fiber cable 10 and the branch
The transmission frame structure of the optical signal transmitted through the fiber 12 is
It is not limited to the example shown in FIG. Other common transmission formats are also available, whether for telephone signals or computer data.

In this embodiment, the optical fiber cable 10 is used.
Is a wavelength division multiplexing system of 50 wavelengths and the transmission rate of one wavelength is about 10 Gbps. As a result, a sufficient transmission capacity can be secured. By laying the optical fiber cable 10 in the deep sea above a certain level, there is almost no possibility of an accident such as cutting due to fishing, and at the same time, an earthquake that has a great influence on the land communication network will not occur. The possibility of disconnecting two or more locations of the cable 10 is close to zero, and high reliability as an alternative transmission line in the event of a disaster can be secured. Of course, even in normal times, it can be used as a large-capacity communication path that complements the land-based transmission path.

The wavelength multiplexing method logically corresponds to setting a transmission line for each wavelength. Therefore, assigning a different wavelength to each source in the wavelength multiplexing system eliminates the need to specify each source in the transmitted frame, etc.
There is an advantage that the substantial transmission capacity can be increased.

In the above embodiment, one wavelength unique to each base station is assigned, but two or more wavelengths may be assigned to one or more base stations. The added wavelength can be used, for example, for monitoring the base station and for broadcasting all stations.

Optical multiplexers / demultiplexers 16a and 16b and optical repeater 1
An earthquake measuring device such as a seismograph or an earthquake monitoring device may be connected to either 8a or 18b, and the obtained earthquake information may be transmitted continuously or upon request to a specific base station. By doing so, it is possible to develop a system that constantly monitors deep-sea floor earthquake motions.

[0032]

As can be easily understood from the above description, according to the present invention, it is possible to provide a disaster-resistant, highly reliable and large-capacity communication system. That is, a trunk optical fiber cable is laid on a place that is not affected by disasters that affect existing communication channels, for example, on the deep sea floor, so if an existing communication channel is interrupted during a disaster, it should be replaced immediately. The communication interruption time can be greatly reduced.

Since a unique wavelength is assigned to the transmission source and the wavelength division multiplexing system is used, signals can be efficiently transmitted and the effective transmission capacity can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a laid state of a trunk fiber cable according to an embodiment.

FIG. 2 is a schematic configuration block diagram of the present embodiment.

FIG. 3 is a schematic configuration of a base station 14 and an optical fiber 10a,
It is a block diagram which shows the outline of the connection form with 10b.

FIG. 4 is an example of a transmission frame structure.

[Explanation of symbols]

10: optical fiber cable (main fiber cable) 10a: left-handed optical fiber 10b: right-handed optical fiber 12: branch fiber 14 (14-1, 14-2, ..., 14-n): Base station 16a, 16b: Optical multiplexer / demultiplexer 18a, 18b: Optical repeater 20a. 20b: Input terminal 22a, 22b: Modulation circuit 24a, 24b: Laser diode 26a, 26b: Optical demultiplexer 28a, 28b: Light receiving element 30a, 30b: Demodulation circuit 32a, 32b: Output terminal 40a, 40b: Branch fiber 12 optical transmission fibers 42a and 42b: branch optical fiber 12 reception optical fibers 50a and 50b: optical fiber couplers 52a and 52b: optical filters

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsuguo Kato 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo Kaday Day Submarine Cable System Co., Ltd. (72) Inventor Hitoshi Nishikawa 2-chome Nishishinjuku, Shinjuku-ku, Tokyo No. 3-2 C-Dayd Submarine Cable System Co., Ltd. (72) Inventor Takashi Mizuguchi No. 3-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Inside C-Dayd Submarine Cable System Co., Ltd.

Claims (15)

[Claims] 1. A plurality of base stations are connected to a communication trunk line, a unique wavelength is assigned to each base station, and a transmission line for transmitting a signal of a wavelength assigned to each base station is set to the communication trunk line. A communication system characterized by the above. 2. Each base station transmits a signal to be transmitted to the communication trunk line at a wavelength assigned to itself, and receives signals of wavelengths of all other base stations from the communication trunk line. The communication system according to claim 1, further comprising: 3. The communication system according to claim 1, wherein the communication trunk line is an optical fiber cable, and a signal is transmitted by a wavelength division multiplexing method. 4. The communication trunk line is looped around.
A communication system according to claim 1. 5. The communication system according to claim 4, wherein the communication trunk line comprises two trunk lines, one trunk line in one direction and one trunk line in the other direction. 6. The communication system according to claim 1, wherein the communication trunk line is laid on the seabed. 7. The communication trunk line has a predetermined number of 1
There are multiple branching and branching devices connected to one base station,
The coupling / branching device is a selective removal unit for selectively removing a wavelength component used by a corresponding base station from a signal transmitted through the communication trunk line, and a signal from the corresponding base station on the communication trunk line. The communication system according to any one of claims 4 to 6, further comprising: a combining / branching unit configured to combine and branch the signal from the selective removal unit to the corresponding base station. 8. A plurality of base stations are connected to a trunk optical fiber cable, a unique optical wavelength is allocated to each base station for transmission, and an optical signal from each base station is wavelength-controlled on the trunk optical fiber cable. A communication system characterized in that transmission is performed by a division multiplexing method. 9. Each base station transmits a signal to be transmitted to the trunk optical fiber cable at an optical wavelength assigned to the base station, and all other base station optical wavelength signals from the trunk line. 9. The communication system according to claim 8, further comprising receiving means for receiving from an optical fiber cable. 10. The communication system according to claim 9, wherein the trunk optical fiber cable is looped. 11. The communication system according to claim 10, wherein the trunk optical fiber cable comprises two optical fibers, one in one direction and the other in the other direction. 12. The communication system according to claim 8, wherein the trunk optical fiber cable is laid on the seabed. 13. The communication system according to claim 12, wherein an earthquake measuring device such as a seismograph and an earthquake monitoring device is connected to any of the optical relay branching devices on the seabed, and the earthquake information is transmitted to the base station. 14. The communication system according to claim 7, wherein a branch fiber connecting the trunk optical fiber cable and at least a base station serving as a landing station is non-relay. 15. The trunk optical fiber cable comprises:
A plurality of optical add / drop devices each of which is coupled to one predetermined base station are provided, and the optical add / drop device selectively selects the wavelength component used by the corresponding base station from the signal transmitted through the trunk fiber cable. Selective removing means for removing, and combining means for synthesizing the optical signal from the corresponding base station on the trunk optical fiber cable and for branching the optical signal from the selective removing means to the corresponding base station. The communication system according to any one of claims 7 to 14, further comprising: