JPS6276937A - Optical bus system - Google Patents

Abstract

PURPOSE:To improve the reliability of data transmission while the influence of the phase distortion due to transmission delay or relay of an optical signal is excluded to the utmost by using a signal subjected to optoelectric conversion as a reception signal from other station to its own station thereby decreasing the transmission distance of the optical signal transmitted/received between the stations. CONSTITUTION:No signal appears on a transmission line 25a of a reception station A while a station B has a transmission right. Thus, only transmission data of the station B converted into an electric signal appearing at a transmission line 27a at the optical fiber side is fed to a synthesis circuit 32a via a transmission line 34a. The synthesis circuit 32a uses this signal as the reception data and supplies the signal to a reception data input port of a terminal connected to a station A. Thus, the transmission data sent from the transmission station is sent to the reception station via the shortest transmission path.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical bus system in which a plurality of stations coexist using optical fiber cables to communicate between the stations.

(Prior Art and its Problems) With the increase in the number of terminals and the amount of transmitted data, communication systems such as data communication systems are required to be high-speed and highly reliable.

Figure 1 shows a conventional bus system using a twinaxial cable or coaxial cable 1, with multiple nodes 2 on the cable 1.
a to 2n are connected, and communication is performed between each node. This communication system has a problem in that as the number of nodes increases, transmission quality deteriorates due to impedance mismatch in coupling parts, noise, and the like.

FIG. 2 shows a known communication system using a U-shaped optical fiber cable 3 in place of the cable 1 such as a balanced cable in FIG. It is a vessel.

Each of the nodes 8a to 8C transmits optical signals to the optical fiber cables 3a to 3C via the transmission optical fiber cables 6a to 6C1 and the optical inserters 4a to 4C, respectively, and the transmitted optical signals are transmitted by the optical fiber cable 3d. The signals are turned back and transmitted to the optical fiber cables 3e to 3g, where they are branched by the respective optical splitters 5a to 5C, and received by the respective nodes 8a to 8C via the optical fiber cables 7a to 7C. In this communication system, optical signals are inserted and branched into transmission cables at the optical level, so there is a relatively large loss during this insertion and branching, and generally, if the insertion and branching is repeated several times, the optical signal level attenuates and the optical・Electrical conversion becomes difficult. Therefore, in this type of communication system, a repeater is required every time the number of nodes (for example, three nodes) increases in order to increase the attenuated optical signal level.

FIG. 3 shows a known communication system in which an optical signal is converted from optical to electrical at each station in order to increase the optical signal level, and then the converted signal is converted from electrical to optical again to perform relaying. In the figure, each station is connected to an upstream station via fiber optic cables 12a and 12b, respectively.
, 12c is optically converted into electricity by each optical/electrical converter (0/E) 9a, 9b, 9c to increase its power, and then converted to an electrical/optical converter (Elo) 10a.
, 10b, and 10c perform electrical-to-optical conversion again and transmit it to downstream optical fiber cables 12b, 12c, and 12d. Also, the node lla (llb, 1l
c) transmits the transmission signal to each electrical/optical converter 10a (10b,
10c) performs electrical/optical conversion and transmits it to the downstream optical fiber cable 12b (12c, 12d). On the other hand, the optical signal sent out to the optical fiber cable 12d is sent back to the upstream station, and the optical-to-electrical converters 9d and 9e of each station convert the optical signal into electricity in the same manner as described above. , again the electrical/optical converters 10d, 10
e converts the signal into electricity and transmits it to optical fibers 1, 2e, and 12f on the upstream station side. Each node 11a, 1
lb, 11c are optical/electrical converters 9e, 9d on the return trip side
, 9c, when an electrical signal that has been optically converted into electrical data is input, it is determined whether or not the electrical signal was transmitted toward its own node, and then received. The communication system shown in FIG. 3 includes outbound optical fiber cables 12a, 12b,
The optical signal sent to 12c is returned to optical fiber cable 12d.

12e and 12f and receive them, the transmission path becomes long, resulting in a delay in the transmission of the optical signal.
Furthermore, at each station, optical signals are simply converted into optical/electrical signals.
Since the optical signal is relayed after being converted from electricity to light, phase distortion occurs in the optical signal during relaying, and this phase distortion is superimposed each time it is relayed, adversely affecting the reliability of data transmission.

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to provide an optical bus system that improves the reliability of data transmission by eliminating as much as possible the influence of optical signal transmission delays and phase distortion caused by relaying. purpose.

(Means for Solving the Problem) According to the present invention, in order to achieve the above-mentioned object, in an optical bus system in which a plurality of stations are connected by an optical communication path and each station communicates, the optical communication road first
and a two-core cable consisting of a second optical fiber,
Each station performs optical-to-electrical conversion on the optical signal received from the upstream station via the first optical fiber, equalizes and boosts it, performs electrical-to-optical conversion again, and transmits it in one direction to the downstream station. The optical signal received from the downstream station via the second optical fiber is converted optically to electrically, equalized and boosted, and then converted again electrically and optically to the upstream station for one-way reception, and from the local station to the other station. transmitting a transmission signal via the first optical fiber to a downstream station and simultaneously via the second optical fiber to an upstream station; An optical bus system is provided in which a signal received through one station and subjected to optical-to-electrical conversion is used as a reception signal from another station to the own station.

(Function) The transmission signal from the own station to the other station is
The transmission signal is transmitted to the downstream station via the optical fiber, and at the same time it is transmitted to the upstream station via the second optical fiber. Since the received signal is a signal that is received through one end and converted into light and electricity, the transmission distance of the optical signal transmitted through the optical fiber cable is shortened, and the number of relays is also reduced. The effects of transmission delays and phase distortion due to relaying are eliminated as much as possible.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 shows the configuration of each station of the optical bus system according to the present invention, each station A and B.

A first optical fiber 20a that transmits an optical signal from each upstream station of C (in FIG. 4, the station on the left side of the own station is defined as the upstream station, and the station on the right side is defined as the downstream station);
20b and 20c are optical/electrical converters (0/E) 22a composed of APDs and the like.

22b and 22c, respectively, and each output side of the optical-to-electrical converters 22a, 22b, and 22c is connected to an LED via electrical signal transmission lines 25a, 25b, and 25c.

Electrical/optical converter (Elo) 24a consisting of LD etc.
.

It is connected to each input side of 24b and 24c. and,
Electrical/optical converters 24 a, 24 b, 24 c
The respective output sides of the optical fibers 20b and 20c are the first optical fibers 20b and 20c.

204 are connected to each other.

On the other hand, a second optical fiber 30b transmitting optical signals from the downstream stage ten of each station A, B, and C;
30c and 30d are optical/electrical converters (0/E) 26a, which are also composed of APDs and the like.

The output sides of the optical-to-electrical converters 26a, 26b, and 26c are connected to the input sides of the optical-to-electrical converters 26b and 26c, respectively, and are connected to the electrical-to-optical converters composed of LDs and the like via electrical signal transmission lines 27a, 27b, and 27c. (F, / 0) 28a, 28b, 28
connected to each input side of c. And electric/optical converters 23a, 28b.

Each output side of 28c is connected to the second optical fiber 30a.

30b and 30c are connected to each other.

Electric signal transmission lines 25a and 27a of station A are connected to a transmission data output port of a terminal (not shown) via a transmission line 31a. Moreover, each electric signal transmission line 25a
, 27a are connected via transmission lines 33a and 34a, respectively, to a combining circuit 32a consisting of an OR circuit, an exclusive OR circuit, etc.
The output side of the combining circuit 32a is connected to the received data input port of the terminal. Similarly to station A, station B (C) also has a transmission line 31b (31c) that connects the transmission data output port of a terminal (not shown) to an electric signal transmission line 25b (25c).
and 27b (27c), and each electric signal transmission line 25b, 27b (25c, 27c) is connected to the input side of the combining circuit 32b (32c) via the transmission line 33b (33c), 34b (34c), respectively. The output side of the combining circuit 32b (32c) is connected to the received data input port of the terminal.

Next, stations A and B configured as described above
,C will be explained.

An optical signal transmitted from a station upstream of station A via an optical fiber cable 20a is converted into an electrical signal by an optical-to-electrical converter 22a. During this conversion, the optical signal that has weakened during transmission through the optical fiber 20a is converted into an on-off pulse signal equalized to the same level as the electrical signal level during relay at the upstream station using a known method. The electrical signal thus converted is supplied to the electrical-to-optical converter 24a via the transmission line 25a, where it is again converted into an optical signal having a predetermined signal level and sent to the optical fiber 20b. Thus, the optical signal received from the upstream station is relayed to the downstream station B.
will be transmitted to. Stations B and C, which are configured in the same way as station A, sequentially relay optical signals to downstream stations in the same manner as described above.

Therefore, the first optical fibers 20a, 20b, 20c, 2
0d transmits optical signals only in the direction from the upstream station to the downstream station. On the other hand, the second optical fiber 30
a, 30b, 30c, 30d are the first optical fibers 20a
, 20b, 20c, and 20d, the optical signals are transmitted only in the direction from the downstream station to the upstream station, and the optical signal transmitted from the downstream station via the optical fiber 30d is transmitted to the station A mentioned above. After being converted into an electrical signal having a predetermined signal level by the optical/electrical converter 26c similarly to the optical/electrical converter 22a,
The signal is again converted into an optical signal by the electrical/optical converter 28c and transmitted to station B via the optical fiber 30c. Similarly, at stations B and A, optical signals from downstream stations are relayed and sequentially transmitted to upstream stations.

For example, when station B, which has obtained the transmission right through polling or the like, transmits transmission data to station A, the transmission data output from the transmission data output port of the terminal connected to station B is transmitted via transmission lines 31b and 25b. The light is supplied to the electric-to-optical converter 24b, converted to electric-to-optical as described above, and transmitted to a station downstream from station B via the first optical fibers 20c, 20d, as well as via the transmission lines 31b, 27b. The signal is supplied to an electrical-to-optical converter 28b, where it is converted into electrical signals and transmitted to a station upstream from station B via second optical fibers 30b and 30a. No signal appears on the transmission line 25a of receiving station A while station B has the right to transmit, and therefore, the combining circuit 3
2a, only the transmitted data from station B converted into an electrical signal appearing on the transmission line 27a on the second optical fiber side is supplied via the transmission line 34a, and the combining circuit 32a receives this signal. It is supplied as data to the receive data input port of the terminal connected to station A. As a result, the transmission data transmitted from the transmitting station is transmitted to the receiving station via the shortest transmission path.

On the other hand, the receiving data from station B, which is converted into an electrical signal and appears on the transmission line 25e on the first optical fiber side, is supplied to the combining circuit 32c of station C, which is not a receiving station, via the transmission line 33c, and is combined. The circuit 32c supplies this received data to the received data input port of the terminal connected to station C, but that terminal verifies by a known method that the received data is not intended for its own terminal, and Do not accept received data.

The case where another station obtains the transmission right and transmits the transmission data can also be easily inferred from the above explanation, so the explanation will be omitted below.

(Effects of the Invention) As detailed above, according to the optical bus system of the present invention,
The optical communication path is configured with a two-core cable consisting of first and second optical fibers, and each station connected by the optical communication path receives an optical signal received from an upstream station via the first optical fiber. After performing optical-to-electrical conversion to equalize and increase the power, it performs electrical-to-optical conversion again and transmits it in one direction to the downstream station, while optical-to-electrical converts the optical signal received from the downstream station via the second optical fiber. After equalization and boosting, the signal is converted into electricity and optical again and sent in one direction to the upstream station, and the transmission signal from the own station to the other station is sent to the downstream station via the first optical fiber, and at the same time, the signal is sent to the downstream station via the first optical fiber. While transmitting the signal to the upstream station via the optical fiber, the signal is received via either the first or second optical fiber and converted from optical to electrical, and is used as a reception signal from another station to the own station. As a result, the transmission distance for optical signals sent and received between stations is shortened, and the number of repeats can therefore be reduced to the minimum necessary, thereby eliminating as much as possible the effects of optical signal transmission delays and phase distortion caused by repeating. can improve the reliability of data transmission.

[Brief explanation of drawings]

1 to 3 show conventional data communication systems,
Figure 1 is a configuration diagram of a bus communication system using a balanced cable or coaxial cable, and Figure 2 is a diagram of a U-shaped optical fiber cable, in which an optical signal is inserted with an optical inserter, and an optical branch is used. Fig. 3 is a block diagram of an optical bus system in which the optical signal is converted from optical to electrical at each station, and then converted back to electrical/optical. FIG. 1 is a configuration diagram of an optical bus system according to the present invention, showing one embodiment of the invention. 20a to 20d...first optical fiber, 22a to 22e and 26a to 26c...optical/electrical converter,
24a to 24c and 28a to 28c-electrical/optical converter, 30a to 30d... second optical fiber, 32
a to 32 C-...Synthesis circuit, A, B, C...Station.

Claims (1)

[Claims] In an optical bus system in which a plurality of stations are connected by an optical communication path and communication is performed between each station, the optical communication path is constituted by a two-core cable consisting of a first and second optical fiber, and each station The optical signal received from the upstream station via the first optical fiber is optical-to-electrical converted, equalized and boosted, and then electrical-to-optical converted again for unidirectional transmission to the downstream station, while the second optical fiber is The optical signal received from the downstream station is optical-to-electrical converted, equalized and boosted, and then electrical-to-optical converted again and transmitted in one direction to the upstream station. transmitted to a downstream station via an optical fiber, simultaneously transmitted to an upstream station via said second optical fiber, and received via either one of said first optical fiber and said second optical fiber. , an optical bus system characterized in that a signal that is converted from optical to electrical is used as a reception signal from another station to its own station.