JPS628982B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an optical communication system using a passive branch type optical data bus.

Passive branch type optical data buses do not include active devices in series with the bus, so they provide highly reliable optical data busses.
Although a bus has the advantage of being easy to implement, optical signal loss occurs at branch points (couplers), so the level of the received signal changes depending on the number of couplers existing between the receiving point and the transmitting point. Therefore, in an optical communication system in which a plurality of stations are connected by this type of optical data bus, the level of a received signal varies greatly depending on which station the signal comes from. Changes in transmission level are dealt with by automatically adjusting reception sensitivity, but communication speed is limited by the response speed of sensitivity adjustment, making high-speed communication difficult.

To allow optical signals to flow bidirectionally on an optical data bus, either two unidirectional optical couplers with opposite directions must be used, or a bidirectional optical coupler with a special structure must be used. However, if two unidirectional optical couplers are used, two transmitter/receiver sets are required, increasing the number of parts, and bidirectional optical couplers require strict optical precision and generally suffer from optical loss. is large.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical communication system in which the level of the received signal is the same regardless of the transmitting station, and the number of parts is small.

In the present invention, a reflector is provided at one end of the optical transmission line to turn back the signal to form a round trip line, and each transmitter of a plurality of stations is connected in the forward direction of this transmission line via a unidirectional coupler. In the return direction, each receiver of each station is connected via a unidirectional coupler, and the transmission output level of each station is determined so that the level of the signal transmitted from each station is equal at the turning point of the transmission line. It is something that

Hereinafter, the present invention will be explained in detail with reference to the drawings.
FIG. 1 is a conceptual block diagram of an embodiment of the present invention.
In FIG. 1, 1 is an optical transmission line, 2 ₁ , 2 ₂ ,
......2n is the communication station 3 ₁ , 3 ₂ , ...3n is the transmitter in each communication station, 4 ₁ , 4 ₂ , ......4n
is the receiver at the communication station.

The optical transmission line 1 is made into a round trip line by returning communication at a reflector A provided at one end, and transmitters 3i of each communication station 2i (i=1 to n) are connected to each other in the outward direction. They are connected via a coupler consisting of a unidirectional passive branch, and in the return direction, the receivers 4i of each communication station 2i are connected via similar couplers. Absorption at the other end of the optical transmission line 1
A container B is provided. The coupling of each transmitter 3i is
They are all oriented in the same direction, and accordingly, the couplers of the receiver 4i are all oriented in the same direction. That is, the structure is such that all output signals from each transmitter 3i are reflected by the reflector A of the optical transmission line 1 and transmitted to each receiver 4i. Note that the transmitter 3i and the receiver 4i may be connected to a common coupler as shown in FIG.

Here, in reflector A, which transmitter 3i
The signal transmission level of each transmitter 3i is set so that the signals from the transmitter 3i have the same level.
By doing this, the level of the signal transmitted from the reflector A to each receiver 4i varies depending on the distance from the reflector A to each receiver 4i and the number of branches interposed between them. There is no difference due to the transmitter 3i. Therefore, the sensitivity of the receiver 4i may be uniform for any transmitter 3i, and even if automatic sensitivity adjustment is required, it is sufficient to compensate for slight level variations, so high-speed communication is possible. suitable for

Since the optical transmission line 1 becomes a bidirectional transmission line through the use of the reflector A, all communication stations can transmit their transmission outputs to both the right-hand station and the left-hand station. Therefore, bidirectional communication is possible even if only one pair of unidirectional couplers is used between the transmitter and the receiver. In other words, a bidirectional optical data bus with a small number of parts can be realized.

As described above, the present invention provides a reflector at one end of an optical transmission line to return the signal to form a round trip line, and transmits each transmitter of a plurality of stations in a unidirectional direction in the forward direction of the transmission line. Each receiver of each station is connected via a unidirectional coupler in the return direction, and each station is connected so that the level of the signal transmitted from each station is equal at the turning point of the transmission line. The transmission output level is determined.

Therefore, according to the present invention, it is possible to realize a communication system in which the level of the received signal is the same regardless of the transmitting station, and the number of parts is small.

[Brief explanation of the drawing]

Fig. 1 is a conceptual configuration diagram of an embodiment of the present invention;
The figure is a partial modification of FIG. 1. 1... Optical transmission line, 2 ₁ to 2n... Communication station, 3
₁ to 3n...transmitter, 4 ₁ to 4n...receiver, A
...Reflector, B...Absorber. 〓〓〓〓

Claims (1)

[Claims] 1 An optical transmission line in which an optical signal is folded back by reflection at one end, and connected through a passive branch connected with the direction in which the folded part of this line exists, and the level of the signal at the folded part is connected to multiple communication lines. An optical signal transmitter whose output level is set to a constant value that is common between stations, and an optical signal receiver connected through a passive branch that is oriented in the direction in which the line turn section exists. An optical communication system that has multiple communication stations with