JPH0514285A - Optical communication network - Google Patents

Abstract

PURPOSE:To minimize the increase of the number of star couplers in a multi channel optical communication network. CONSTITUTION:This network is provided with a first optical multiplexer/ demultiplexer 19 to derive a pair of optical fibers 5-6, 7-8 and 9-10 from plural respective nodes 1, 2 and 3, connect a pair of the optical fibers to both tips of a star coupler 4, provide two systems of a transmitting channel and a receiving channel at a node l, further, supply a signal from the transmitting channel of one side system to one side 5 of the pair of the optical fibers, and supply the receiving signal from one side optical fiber 5 to the receiving channel to other side system, and a second multiplexer/ demultiplexer 20 to supply the signal from the transmitting channel of other side system to other side of the pair of the optical fibers and supply the receiving signal from other side optical fiber 6 to the receiving channel to one side system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an optical LA using optical communication.
The present invention relates to an optical communication network such as N (local area network).

[0002]

2. Description of the Related Art In a communication network, optical fibers derived from a plurality of terminal devices are coupled via respective couplers, and communication is performed between the respective terminals via the optical fibers and the couplers.

There are various types of couplers, one of which is called a star coupler, and an optical LAN using this star coupler is described in E. G. Rawso
n, “Fibernet: Multimode Opt
ical Fibers for Local Com
putter Networks ”, IEEE Tran
actions on Communication
s, Vol. COM-26, NO. 7, JULY 19
78.

FIG. 8 shows an optical L using this star coupler.
The structural example of AN is shown. The signal from each node 51 is converted into an optical signal by each light emitting element 52a and supplied to the star coupler 54 via each input optical fiber 53a. These optical signals are mixed once by the star coupler 54, then distributed to the respective light receiving elements 52b through the respective output optical fibers 53b and converted into electric signals again, and these electric signals are supplied to the respective nodes 51. To be done. As a result, the signal transmitted from one node can be transmitted to all nodes (multi-destination), and a normal LAN using a coaxial cable can be provided.
A communication network similar to can be constructed.

On the other hand, it has also been proposed to connect each node with two or more communication paths to form a so-called multi-channel LAN. For example, in Japanese Unexamined Patent Publication No. 2-0069999 filed by the present applicant, in order to transmit a voice signal and an image signal requiring real-time property in a LAN, a CSMA / CD (carrier sense multi) is used.
In addition to contention-based buses such as ple access / collision detection), TDMA (time division multiple acces
s) and other time-division type buses are provided, and the bus to be used is selected according to the nature of the data to be sent.

[0006]

In order to realize this multi-channel LAN using optical communication, for example,
As shown in FIG. 9, a bus (first channel) of the contention system and a bus (second channel) of the time division system from the bus control device 55.
There is a method of detecting a channel by connecting it to each node 58 via two star couplers 56 and 57.

In each channel, as shown in FIG.
It is necessary to provide light emitting elements 59a and 59b for transmission and light receiving elements 60a and 60b for reception for each channel.

The number of star couplers required in this multi-channel LAN increases as the number of buses, that is, the number of channels, increases. Therefore, there is a problem that the LAN configuration becomes complicated and the LAN construction cost increases.

The present invention aims to minimize the increase in the number of star couplers in a multi-channel optical communication network.

[0010]

In order to achieve the above object, the optical communication network of the present invention derives a pair of optical fibers from each of a plurality of nodes and connects the pair of optical fibers to both ends of a star coupler. Each node of the plurality of nodes is provided with a transmission path and a reception path for two systems, and further, a signal from the transmission path of one system is supplied to one of the pair of optical fibers and the one of the optical fibers is supplied. A first optical multiplexer / demultiplexer that supplies the reception signal from the optical path to the reception path to the other system, and a signal from the transmission path of the other system to the other of the pair of optical fibers and the other And a second optical multiplexer / demultiplexer for supplying a reception signal from the optical fiber to the reception path to the one system.

[0011]

In the optical communication network of the present invention, the signal from the transmission path of one system is supplied to one end of the star coupler via the first optical multiplexer / demultiplexer and the optical fiber. The output from the other end of the star coupler is supplied to the receiving path of one system via the optical fiber and the second optical multiplexer / demultiplexer. This enables simultaneous transmission to all the nodes connected to the star coupler.
Also, when transmitting from the other system, the same as in the case of transmission of one system, except that the star coupler is transmitted in the opposite direction to the case of transmission of one system, the reception path of the other system. Is supplied to. In this way, by making the directions of the lights passing through the star couplers in the respective systems opposite to each other, it becomes possible to independently transmit the signals of the two systems while using the common star coupler.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The features of the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 shows the configuration of an embodiment of the optical communication network of the present invention.

A plurality of nodes 1 to 3 are connected to each other via a star coupler 4. The star coupler 4 is a general passive star coupler having the same configuration as the star coupler shown in FIG. 8 described in the section of the conventional example. Regarding the structure of the star coupler itself, the reference E. G. Ra
wson, “Fibernet: MultimodeO
optical Fibers for Local C
computer Networks ”, IEEE Tr
transactions on Communicati
ons, Vol. COM-26, NO. 7, JULY
Since it is described in 1978, detailed description is omitted here.

A pair of optical fibers 5-6, 7-8, 9-10 are led out from the respective nodes 1 to 3, and one optical fiber 5, 7, 9 is connected to one splicing terminal 4a of the star coupler 4. The other optical fibers 6, 8 and 10 are connected to the other joint terminal 4b of the star coupler 4.

Next, the configuration of each node will be described.
Since the nodes 1 to 3 have the same configuration, the node 1 will be described as an example.

The node 1 includes a node body 13 having output signal paths 11a and 11b and input signal paths 12a and 12b for the first and second channels, respectively.
The node main body 13 and the star coupler 4 are configured by a unidirectional / bidirectional interface (hereinafter, simply referred to as an interface) 14.

In the interface 14, the transmitting device 15a and the light emitting device 16a are connected to the output signal path 11a of the first channel of the node body 13, and the receiving device 17a and the light receiving device 18 are connected to the input signal path 12a of the first channel.
a is provided with a transmitting device 15b and a light emitting device 16b for the output signal path 11b of the second channel, and a receiving device 17b and a light receiving device 18b for the input signal path 12b of the second channel.

The output end of the light emitting device 16a for the first channel and the input end of the light receiving device 18b for the second channel are
The first optical multiplexer / demultiplexer 19 is connected to each branch end, and the common end of the optical multiplexer / demultiplexer 19 is connected to one of the junction terminals 4a of the star coupler 4. Similarly, the output end of the light emitting device 16b for the second channel and the input end of the light receiving device 18a for the first channel are connected to the second optical multiplexing /
It is connected to each branch end of the demultiplexer 20, and the common end of the optical multiplexer / demultiplexer 20 is the other junction terminal 4 of the star coupler 4.
connected to either b.

Next, the operation of the above optical communication network will be described.

Now, considering the case where the node 1 transmits the first channel, the output signal path 1 of the node body 13
The output signal from 1a is supplied to the transmitter 15a, and the signal light is output from the light emitting device 16a. This output signal light is supplied to one of the junction terminals 4 a of the star coupler 4 via the first optical demultiplexer / multiplexer 19 and the optical fiber 5.
Therefore, the output signal light from the node 1 is distributed and appears at each of the other junction terminals 4b of the star coupler 4. The distributed signal light is supplied to the nodes 1 to 3 via the optical fibers 6, 8 and 10.

Next, considering the receiving operation at the node 1, the signal light from the optical fiber 6 is branched by the second optical multiplexer / demultiplexer 20 and received by the light receiving device 18a and the receiving device 17a.
And is converted into an electric signal. This electric signal is supplied to the input end of the first channel of the node body 13 via the input signal path 12a. It should be noted that, for convenience of explanation, it is described here that the node 1 transmits and the node 1 receives the same, but the other nodes 2 and 3 perform the same receiving operation. That is, the signal of the first channel transmitted from one node is transmitted to the first channel in all other nodes.
It will be received as a signal of the channel signal.
That is, broadcastability is secured.

Next, consider the case where the node 1 transmits the second channel. In this case, the transmitter 15b for the second channel and the light emitting device 16b are in the operating state, and the light from the light emitting device 16b is transmitted through the second optical demultiplexer / multiplexer 20 and the optical fiber 6 to the star coupler 4 Is supplied to the other joining terminal 4b. The signal light passing through the star coupler 4 and obtained from one of the splicing terminals 4a passes through the optical fiber 5, is branched by the first optical multiplexer / demultiplexer 19, and is supplied to the light receiving device 18b and the receiving device 17b. Then, the signal light is converted into an electric signal. This electric signal is supplied to the input end of the second channel of the node body 13 via the input signal path 12b.

As described above, in this embodiment, when transmitting the first channel from the node 1, the optical fiber 5 serves as the transmission line and the optical fiber 6 serves as the reception line.
When transmitting the second channel from the node 1, conversely, the optical fiber 6 serves as a transmission line and the optical fiber 5 serves as a reception line.

As described above, when transmitting the first channel, the signal light is input from one of the junction terminals 4a of the star coupler 4, and when transmitting the second channel, the signal light is input from the other junction terminal 4b. By utilizing the bidirectionality of light, the same star coupler 4 can be used to separate the signal light of the first channel and the signal light of the second channel.

Next, an example of performing communication between nodes based on different protocols using the above-mentioned multi-channel optical communication network will be described.

For example, the first channel is a channel according to the contention system protocol, and the second channel is a channel according to the time division system protocol.
In addition, one of the nodes functions as a bus control device called a slot generator and has a function of time division control of the second channel.

From the node functioning as the bus controller, one time slot T, as shown in FIG.
The individual bus control signals S1 and node signals S2 are output. The bus control signal S1 includes a message designating a specific node. All nodes receive this bus control signal S1 and only the node specified in the message is allowed to transmit within its time slot T. The signal transmitted from the node based on this permission is the node signal S2.

The procedure for starting time division communication will be described below.

When a node wants to transmit using a time division bus, that is, the second channel, it sends the request to the bus controller using the contention bus, that is, the first channel. The bus control device which has received the transmission request generates the bus control signal S1 including a message permitting the transmission of the requested node. As a result, the node that has requested the transmission can use the second channel to transmit the node signal S2 in a predetermined short cycle. Therefore, the real-time property when transmitting the audio signal, the moving image signal, and the like is ensured.

In the above embodiment, one star coupler is used to form two communication paths.
If three star couplers are used, four channels can be formed, and if three star couplers are used, six channels can be formed. That is, by adding the star coupler, the number of transmission paths can be increased by two channels per one star coupler.

Further, in the above-described embodiment, the case of using different protocols was described as an example of multi-channel, but the present invention is not limited to this, and a plurality of communication channels are used. The present invention can be applied to any optical communication network.

Further, in the above optical communication network, it should be connected to the same node as described in Japanese Patent Application No. 2-98370 filed by the applicant of the present invention instead of the ordinary star coupler. It is also possible to use a passive star coupler (hereinafter referred to as a mutually connectable star coupler) in which the transmission coefficient of the signal between the paired input terminal and output terminal is zero.

When the above-mentioned interconnectable star couplers are used, even if the number of nodes increases, the star couplers can be connected to each other to expand the network. Further, as described in the above-mentioned Japanese Patent Application No. 2-98370, a network configured by connecting mutually connectable star couplers has bidirectionality, and this property is utilized for communication. Confidentiality can be maintained and communication capacity can be increased.

An example of the structure of a passive star coupler that can be used instead of the star coupler 4 of the optical communication network shown in FIG. 1 is shown in FIGS. 3 and 5.

FIG. 3 is a structural example of a passive star coupler having three terminals that can be connected to each other. Here, a passive star coupler that can be interconnected is configured by using six 1 × 2 optical branch paths 21. 1 × 2 optical branch 21
4, there is one optical path 21a on one side and two optical paths 21b and 21c on the other end side, and optical input / output signals to each terminal are u _a1 , u _2a , u _3a and v _{a1 respectively.} , V _a2 , v
_{Assuming a3} , the transfer characteristic of the 1 × 2 optical branch path 21 is expressed by the following equation.

[0037]

[Equation 1]

The transfer characteristic of this star coupler is expressed by the following equation.

[0039]

[Equation 2]

FIG. 5 shows an example of the structure of a passive star coupler having five terminals which can be connected to each other. Here, 10 1 × 2 optical branch paths 21 and 5 2 × 2 optical branch paths 22 are combined. The 2 × 2 optical branch path 22 has two optical paths 22a and 22b on one side and two optical paths 22c and 22d on the other end side as shown in FIG. 6, and outputs optical input / output signals to each terminal respectively. u _b1 , u _b2 , u _b3 , u _b4 , v _b1 , v _b2 , v _b3 ,
_Assuming that v _b4 , the transfer characteristic of the 2 × 2 optical branch path 22 is expressed by the following equation.

[0041]

[Equation 3]

The transfer characteristic of the star coupler 23 is expressed by the following equation.

[0043]

[Equation 4]

FIG. 7 shows an example of the configuration of an optical communication network which is constructed by combining a passive star coupler capable of interconnecting the five terminals shown in FIG. 5 and a bidirectional optical amplifier. Figure 7
5, reference numeral 23 is a 5-terminal interconnectable passive star coupler of FIG. 5, 24 is a bidirectional optical amplifier, and 25 is a node equipped with the interface 14 shown in FIG. The bidirectional optical amplifier 24 is specifically a semiconductor laser amplifier, but it may be a rare earth-doped fiber amplifier. Regarding semiconductor laser amplifiers, see Shimada and Nakagawa “Research Status of Semiconductor Laser Amplifiers Used in Optical Communication Systems”, O plus E, August 1989, p106 to p111. For the rare earth-doped fiber amplifier, see Horiguchi "Optical Fiber Amplifier", Optics, Vol. 19, No. 5, P276 to P282.

According to the configuration of FIG. 7, two independent bidirectional communication channels can be configured with one star coupler, and a new interconnectable passive channel can be used in response to an increase in the number of nodes. A type star coupler can be added to expand the network.

[0046]

As described above, according to the present invention,
Two independent communication paths can be formed with one star coupler. Therefore, it is possible to suppress an increase in the number of star couplers required in the multi-channel optical communication network, simplify the configuration of the communication network, and reduce the construction cost of the communication network.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an optical communication network of the present invention using a star coupler.

FIG. 2 is a diagram for explaining a time slot in the time division method.

3 is a schematic diagram showing a circuit configuration of a three-terminal mutually connectable passive star coupler applicable to the optical communication network shown in FIG.

4 is a schematic diagram of a 1 × 2 optical branch used in the star coupler shown in FIG. 3. FIG.

5 is a schematic diagram showing a circuit configuration of a passive terminal star coupler having five terminals, which is applicable to the optical communication network shown in FIG. .

FIG. 6 is a schematic diagram of a 2 × 2 optical branch used in the star coupler shown in FIG.

FIG. 7 is a schematic diagram showing a configuration of an optical communication network configured by combining a passive star coupler capable of interconnecting 5 terminals and a bidirectional optical amplifier.

FIG. 8 is a configuration diagram showing an example of a conventional optical LAN using a star coupler.

FIG. 9 is a diagram showing a configuration example of a conventional multi-channel optical LAN using a star coupler.

FIG. 10 is an explanatory diagram showing a transmitting and receiving unit of each channel in a conventional multi-channel optical LAN.

[Explanation of symbols]

1-3 nodes, 4 star coupler, 4a, 4b splicing terminal, 5-10 optical fiber, 11a, 11b output signal path, 12a, 12b input signal path, 13 node body, 14 interface, 15a, 15b transmitter, 16a, 16b light emitting device, 17a, 17b receiving device, 18a, 18b light receiving device, 19, 20 optical demultiplexing device
Multiplexer, 21 1 × 2 optical branch path, 22 2 × 2 optical branch path, 23 5 terminal interconnectable passive star coupler, 24 bidirectional optical amplifier, node with 25 interface, 51 node, 52a light emitting element, 52
b light receiving element, 53a input optical fiber, 53b output optical fiber, 54 star coupler, 55 bus controller, 56, 57 star coupler, 58 node, 59
a, 59b light emitting element, 60a, 60b light receiving element

Claims (1)

Claim: What is claimed is: 1. A pair of optical fibers is derived from each of a plurality of nodes, the pair of optical fibers is connected to both ends of a star coupler, and a transmission path is provided to each node of the plurality of nodes. And two receiving paths are provided, and a signal from the transmitting path of one system is supplied to one of the pair of optical fibers and a received signal from the one optical fiber is sent to the receiving path of the other system. A first optical multiplexer / demultiplexer to be supplied and a signal from the transmission path of the other system is supplied to the other of the pair of optical fibers, and a reception signal from the other optical fiber is supplied to the one system. Second to supply to the receiving path of
An optical communication network, which is provided with the optical multiplexer / demultiplexer.