JPS59181735A - Star repeater collision detecting method for optical communication - Google Patents

Abstract

PURPOSE:To detect a collision irrespective of contents of transmitting data, a modulating method, a transmission rate, etc. by superposing an optical bias on an optical signal transmitted from each terminal, and detecting a collision of a signal when a star repeater receives two or more optical biases at the same time. CONSTITUTION:An optical bias (a) is superposed on an optical signal transmitted from each terminal 1i so that a collision is detected when a collision detecting part 7 of an optical star repeater 2 receives two or more optical biases at the same time. In case when the collision is detected, relaying is halted by a gate 8, and also a collision signal is sent out to a terminal. In this way, even if a transmitting signal is logical L, the collision can be detected exactly. Also, this device is used for detecting the bias (a) superposed on the signal, therefore, the collision is detected irrespective of a transmission rate of the signal, a frequency characteristic, etc.

Description

[Detailed Description of the Invention] The present invention detects when optical signals are transmitted between terminals using an optical star repeater, and that optical signals are simultaneously transmitted to the optical star repeater from terminals on the same duplex. The present invention relates to a star repeater collision detection method for optical communications that enables reliable detection.

In optical communication systems, in which optical signals transmitted from multiple terminals are relayed by an optical star repeater and transmitted to each terminal, if an optical signal is transmitted from a terminal double above the optical peak at the same time, a communication error occurs. occurs.

Therefore, in the past, collisions were detected by adding a collision detection signal to an optical star repeater. This collision detection function is based on the assumption that the A word signal transmitted from each terminal is modulated with Manchester code, and if the "Shimadai" or "seed" is missing (the frequency V characteristic is present in the output circuit, etc.). Otherwise, if signals are simultaneously transmitted from terminals on the duplex, the optical power is amplified by 3 dB and a signal is generated.

Therefore, in the conventional collision detection method, it is good if the transmission signal is Manchester coded, but if the data is modified by interview brightness, the logical signal is long < li as shown in Figure 2. There is an error between [, < and the fact that the collision cannot be detected even though a collision actually occurs.

Furthermore, when the data rate is high, the f-characteristic of the optical star repeater circuit element cannot be ignored.

The present invention solves the Zhao problem, and the content of the transmitted data,
Collisions can be detected regardless of the modulation method, transmission speed, etc. The present invention will be described in detail below based on all the drawings.

In Fig. 1, m1tt+2... is a terminal, (2) is an optical star repeater, +31, +312... are transmitting optical fibers, (411+412... are receiving optical fibers, and (5) is an optical-to-electrical converter. part, (6) is the receiving part, (7)
is a collision detection section, (8) is a gate, (9) is a transmission section, (1
0) is an electrical-optical converter.

The present invention superimposes an optical bias ai on the optical signal transmitted from each terminal fil, fi+2, etc. as shown in FIG. Collision is detected when optical biases are received at the same time.If a collision is detected, the gate (8) is controlled to interrupt the relay and send a collision signal to the terminal, just as before. to avoid communication errors.

As described above, the present invention superimposes the optical bias a on the transmission signal, and when two or more of them are detected at the same time, the total collision volume increases to 1.
Therefore, it is possible to detect a collision even if the transmitted signal has a logical logic. Therefore, unlike the conventional method, it is possible to detect a collision even though the d signal is actually colliding. Collisions can be detected reliably.

Furthermore, since the system does not detect the signal itself, but rather detects the bias superimposed on the signal, collisions can be detected regardless of the signal transmission speed, frequency, characteristics, etc.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a device that implements the method of outputting and outputting signals according to the present invention; FIG. 21 is an explanatory diagram of a conventional optical signal; and FIG. '(- is an explanatory diagram of a superior optical signal. fil 11II 2... is the end of ψ11, (2) is an optical star repeater, (7) is a collision detection circuit, and a is an optical bias.

Claims (1)

[Claims] In an optical communication system that transmits optical signals between terminals by relaying optical signals from multiple terminals using a star repeater and transmitting them to each terminal, optical bias is fully superimposed on the optical signal transmitted from each terminal. A star repeater collision detection method for optical communications is characterized in that a collision of signals is detected when the star repeater simultaneously receives two or more optical biases.