JPS6249739A - Star-coupler device - Google Patents

Abstract

PURPOSE:To easily and surely detect a collision, by providing a detecting circuit which detects that optical signals are almost simultaneously inputted >=2 photoelectric conversion circuits and a selection circuit which selects either the coupling signal of the output signal of each photoelectric conversion circuit or a prescribed collision informing signal in accordance with the detecting results of the detecting circuit. CONSTITUTION:When transmitting signals are simultaneously sent from plural stations including a station 50-n, plural photoelectric conversion circuits including a photoelectric conversion circuit 11-n perform photoelectric conversion at a star-coupler device 10. If plural converting circuits of the photoelectricity conversion circuits 11-1-11-n perform the photoelectric conversion upon receiving the optical signals, a collision detecting circuit 14 regards the case as that a transmission collision occurs and outputs a detecting signal having a logic '1'. When the detecting signal of the circuit 14 is of logic '1', a selection circuit 15 selects B-input out of A- and B-inputs. The content of the B-input selected by the circuit 15 is transmitted to optical transceivers 30-1-30-n through optical fiber cables 22-1-22-n.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a star coupler device for optically coupling a plurality of stations.

[Technical background of the invention and its problems] In recent years, C8MA/CD (carrier sense multiple access/collision detection) local area networks (LANs) have been widely used. This type of C3MA/CD type LAN generally uses coaxial cables as its transmission medium, but various optical CSMA/CD type LANs using optical fiber cables have also been proposed.

Now, in an optical C3MA/CD type star connection type LAN, a star coupler device is required along with a plurality of optical fiber cables in order to connect a plurality of stations. Star coupler devices are divided into two types, passive type and active type, depending on the method of branching optical signals. A passive star coupler device branches an optical signal as it is, and is composed only of passive elements. On the other hand, an active star coupler device converts an optical signal into an electrical signal and then branches the optical signal, and has an active circuit.

In an optical C3MA/CD type LAN using this type of star coupler device, it is necessary to detect collisions between transmission signals from each transceiver (optical transceiver) forming the station interface. This collision detection has conventionally been performed in each transceiver. That is, each transceiver converts the optical signal branched by the star coupler device into an electrical signal, and then uses the electrical signal to detect whether or not a collision has occurred. For this reason, the conventional optical C8MA/CD method LA
In N, it is necessary to prepare a collision detection circuit for each transceiver, which poses a problem that increases the cost of the transceiver and therefore the system. Furthermore, in the above-mentioned method, in order to improve the collision detection rate of the collision detection circuit, it is necessary to perform complicated encoding on the transmission data before transmission, and a complicated encoding circuit is required. Furthermore, even if this type of encoding circuit is used, it is difficult to achieve a collision detection rate of 100%.

[Object of the Invention] The present invention has been made in view of the above circumstances, and its object is to provide a star coupler device that can easily and reliably detect a collision.

[Summary of the Invention] In the present invention, an optical/electrical conversion circuit is provided for each input port. The optical/electrical conversion circuit converts an optical signal input to a corresponding input port into an electrical signal. The output signal of each electrical/optical conversion circuit is respectively guided to a detection circuit. This detection circuit monitors the output of each optical/electrical conversion circuit to detect whether optical signals are input to two or more optical/electrical conversion circuits at substantially the same time, that is, whether there is a transmission collision.

The output signals of each electrical/optical conversion circuit are combined and guided to a selection circuit. A predetermined collision signal is also led to this selection circuit. The selection circuit selects either the combined signal of the output signals of each optical/electrical conversion circuit or a predetermined collision notification signal according to the detection result of the detection circuit. The output signals of the selection circuits are commonly guided to an electrical/optical conversion circuit provided for each output port.

Each electrical/optical conversion circuit converts the output signal of the selection circuit into an optical signal and supplies the optical signal to a corresponding output port. Therefore, an optical transceiver receiving an optical signal from an output port can determine whether a collision has occurred simply by checking whether the electrical signal corresponding to the optical signal is the above-mentioned collision signal.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a star coupler device 1 according to an embodiment of the present invention.
FIG. 2 shows the configuration of an optical C3MA/CD type LAN (Local Area Network) to which the same star coupler device IO is applied.

In FIG. 2, the star coupler device 10 is connected to optical transceivers 30-1 to 30-n by optical fiber cables 21-1 to 21-n and 22-1 to 22-n. The optical transceivers 30-1 to 30-n are connected to the station 5 by transceiver cables 40-1 to 40-n.
It is connected to 0-1 to 50-n.

In FIG. 1, 11-1 to 11-n are optical/electric conversion circuits (0/E). - Optical/electrical conversion circuit 11-1 to 1
The inputs of 1-n are connected to optical fiber cables 21-1 to 21-n via input ports 12-1 to 12-n.

The output of the optical/electric conversion circuit 11-1-11-n is connected to the inputs of the waveform shaping circuits 13-1 to 13-n in a one-to-one correspondence, and is also connected to the input of the collision detection circuit 14. .

The collision detection circuit 14 includes optical/electrical conversion circuits 11-1 to 11
-n detects that two or more circuits receive optical signals substantially simultaneously, and its output is connected to the selection control terminal S of the selection circuit 15 with two inputs and one output. Waveform shaping circuits 13-1 to 13- are connected to one input A of the selection circuit 15.
The outputs of 〇 are connected in common, and the other input B of the selection circuit 15 receives a code rule violation (Code R
atto V 1oration) code (hereinafter referred to as CR
The output of a code rule violation code generation circuit (hereinafter referred to as a CRV code generation circuit) 1B that generates a code d (referred to as a V code) is connected thereto. The output of the selection circuit 15 is connected to each input of the electrical/optical conversion circuits (E/, 0) 17-1 to 17-n, respectively.
The output is connected to the cable via output ports 18-1 to 18-0.
It is connected to pulls 22-1 to 22-n.

FIG. 3 shows the configuration of an optical transceiver 30-n. In addition,
The basic configuration of other optical transceivers such as optical transceivers 30-1 and 30-2 is the same as that shown in FIG. In FIG. 3, 31 is a receiver circuit, the input of which is the transmission signal line 4 which is one component of the transceiver cable 40-n.
1-n. The output of the receiver circuit 31 is connected to the input of an electrical/optical conversion circuit (Elo) 32, and the output of the electrical/optical conversion circuit 32 is connected to the optical fiber cable 21-
connected to n. In addition, 33 is an optical/electrical conversion circuit (0
/E). The input of the optical/electric conversion circuit 33 is connected to the cable 22-n, and the output thereof is connected to the input of a waveform shaping circuit 34 having two outputs (output ports). One output of the waveform shaping circuit 34 is connected to the input of the received signal driver circuit 35, and the other output is connected to the CRV code (
Code violation code detection circuit (hereinafter referred to as CRV code detection circuit) that detects a code violation code (code violation code) and outputs a collision signal
It is connected to 36 inputs. The output of driver circuit 35 is connected to receive signal line 42-n, which is one component of transceiver cable 40-ro.

The output of the CRV code detection circuit 36 is connected to the input of a collision signal driver circuit 37, and the output of the driver circuit 37 is connected to a collision indication line 43-n, which is one component of the transceiver cable 40-n. There is.

Next, the operation of the above configuration will be described with reference to FIG. 4 in the case of data transmission from station 50-n.

When station 50-n intends to transmit data, it uses receive signal line 42 of transceiver cable 40-n.
Check whether a received signal (received data) is being transmitted from -n. And if the received signal is not transmitted,
Station 50-n transmits a transmission signal a (transmission data) to optical transceiver 30-n via transmission signal line 41-n of cable 40-n. This transmission signal a is composed of a Manchester code, for example, as shown in FIG. In addition, the Manchester code of all "1" and all '02 is
The signals are shown in FIG. 4 as signals S and C.

Station 50 transmitted to optical transceiver 30-n
The transmission signal a from the transceiver 30-n is supplied to the electrical/optical conversion circuit 32 via the receiver circuit 31 in the transceiver 30-n, and is converted into an optical signal by the electrical/optical conversion circuit 32. The optical signal output by the electrical/optical conversion circuit 32 is
It is supplied to the star coupler device 10 via an optical fiber cable 21-n.

The optical/electrical conversion circuit 11-n in the star coupler device 10 converts the optical signal from the optical fiber cable 21-n into an electrical signal. The electrical signal output from the optical/electrical conversion circuit 11-n is supplied to the waveform shaping circuit 13-n and the collision detection circuit 14. The waveform shaping circuit 13-n shapes the waveform of the electrical signal output from the optical/electrical conversion circuit 11-n. The electrical signal waveform-shaped by the waveform shaping circuit 13-n is supplied to the A input of the selection circuit 15. Selection circuit 15
The CRV code d generated by the CRV code generation circuit 16 is always supplied to the B input of the CRV code generating circuit 16. As shown in FIG. 4, this CRV code d deviates from the Manchester code code rule.

Now, the collision detection circuit 14 is the optical/electrical conversion circuit ti-t.
-11-n are monitored. Collision detection circuit 14
As in this embodiment, the optical/electric conversion circuit 11-1-
11-n, if there are no multiple optical/electrical conversion circuits that receive optical signals and perform optical/electrical conversion, that is, optical/electrical conversion circuits that output effective electrical signals (optical/electrical conversion circuits with output), , a detection signal of logic "0" is output, for example, assuming that no transmission collision occurs.

A detection signal from the collision detection circuit 14 is supplied to a selection control terminal S of a selection circuit 15. When the detection signal supplied to the selection control terminal S is "θ", the selection circuit 15 selects the A input from both the A and 8 inputs. The output signal of the waveform shaping circuit 13-n corresponding to the A input content selected by the selection circuit 15, that is, the transmission signal a from the station 50-n, is transmitted to all of the optical/electrical conversion circuits 17-1 to 17-n. supplied to The electrical/optical conversion circuits 17-1 to 17-n convert the output signal of the selection port 15 into an optical signal. Optical signals output from the electrical/optical conversion circuits 17-1-17-n are transmitted to optical transceivers 30-1 to 30-n via corresponding optical fiber cables 22-1 to 22-n.

Optical transceiver 3O-1s, e.g. optical transceiver 30-
In n, the optical/electrical conversion circuit 33 converts the optical signal transmitted via the optical fiber cable 22-n into an electrical signal. This electrical signal is sent to the waveform shaping circuit 3 as a received signal.
After being waveform-shaped by the same circuit 34, it is supplied to the station 50-n via the driver circuit 35 and the reception signal line 42-n of the transceiver cable 40-n, and also to the CRV code detection circuit 36. supplied to CR
The V code detection circuit 36 detects whether or not the received signal whose waveform has been shaped by the waveform shaping circuit 34 emits a CRV code.

As in this embodiment, when only one station (stations 5O-n) is transmitting data, the above-mentioned received signals are converted into Manchester code codes like signals a-C shown in FIG. Since the signal follows the rule, C
RV code code light is not emitted. When the CRV code light is not emitted, the CRV code detection circuit 3B determines that there is no transmission collision and refrains from outputting a collision signal. In this case, no active collision signal is transmitted to station 50-n (from CRV code detection circuit 36 to driver circuit 37 via collision indication line 43-n of interface cable 40-n).

In the data transmission state, if no active collision signal is transmitted from the optical transceiver 30-n as in this embodiment, the station 50-n continues transmission as if no transmission signal collision has occurred.

Next, a case where transmission signals are simultaneously sent out from a plurality of stations including station 50-n will be described. In this case, in the star coupler device 10, a plurality of optical/electrical conversion circuits including the optical/electrical conversion circuit 11-n,
It receives the optical signal of the transmission signal from the corresponding transmission station and performs optical/electrical conversion. As in this embodiment, the collision detection circuit 14 includes optical/7S air conversion circuits 11-1 to 11-1.
If there are multiple optical/electrical conversion circuits (optical/electrical conversion circuits with output) that receive optical signals and perform optical/electrical conversion among 11-n, a logic "1" is set as a transmission collision has occurred.
outputs a detection signal. The selection circuit 15 selects the B input from the A and 8 inputs when the detection signal from the collision detection circuit 14 is logic "1". The B input content selected by the selection circuit 15, that is, the CRV code from the CRV code generation circuit 16 and the photoelectric/optical conversion circuit 17-1-17-
n is converted into an optical signal by the optical fiber cable 22-
Optical transceivers 3o-1 to 30- through 1 to 22-n
o.

Optical transceiver 30-i, for example optical transceiver 30-
The CRV code optical signal transmitted to N is converted into an electrical signal by the optical/electrical conversion circuit 33. This electrical signal is waveform-shaped by a waveform shaping circuit 34 as a received signal, and then sent to a driver circuit 35 and a transceiver cable 40-n.
The signal is supplied to the station 50-n via the receiving signal line 42-n, and is also supplied to the CRV code detection circuit 3G. The CRV code detection circuit 3G detects whether or not the received signal emits a CRV code. When a plurality of stations (a plurality of stations including station 50-n) are transmitting data as in this embodiment, since the above received signal is illuminated with a CRV code,
The RV code detection circuit 36 emits the CRV code and outputs an active collision signal. This active collision signal is transmitted to station 50-n via driver circuit 37 of optical transceiver 30-n and collision indication line 43-n of interface cable 40-n.

In the data transmission state, when an active collision signal is transmitted from the optical transceiver 30-n as in this embodiment, the station 50-n assumes that a transmission signal collision has occurred and stops transmitting, for example, by a random number. Wait for a determined appropriate time and retransmit.

[Effects of the Invention] As detailed above, according to the present invention, collision detection can be performed inside the star coupler device, so there is no need to provide a collision detection circuit for each optical transceiver as described above. Furthermore, since transmission collisions can be detected simply by monitoring the presence or absence of the output of the optical/electrical conversion circuit corresponding to each station, collisions can be easily and reliably detected without using crudely encoded transmission signals. It becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram of a star coupler device according to an embodiment of the present invention, FIG. 2 is a system configuration diagram of an optical CSMA/CD type LAN (local area network) to which the star coupler device is applied, and FIG. This figure is a block diagram of the optical transceiver shown in FIG. 2, and FIG. 4 is a signal waveform diagram for explaining the operation. IO... star coupler device, 11-1 to 11-n,
33... Optical/electric conversion circuit, 14... Collision detection circuit, 15... Selection circuit, IG-CRV code generation circuit, 1
7-1 to 17-n, 32=-electrical/optical conversion circuit, 21
-1 to 21-n, 22-1 to 22-n-... optical fiber cable, 30-1 to 30-n... optical transceiver, 36... CRV code detection circuit, 50-1 to 50-n
...Station 0 Applicant's agent Patent attorney Takehiko Suzue 1S Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In an optical network system that connects a plurality of stations with a plurality of optical fiber cables and a star coupler device, an optical/electrical conversion circuit is provided for each input port and converts optical signals input to the corresponding input port from optical to electrical; A detection circuit that monitors each output of these optical/electrical conversion circuits to detect that optical signals are input almost simultaneously to two or more optical/electrical conversion circuits, and a detection circuit that detects that optical signals are input almost simultaneously to two or more optical/electrical conversion circuits; /a selection circuit that selects either the combined signal of the output signals of the electrical conversion circuit or a predetermined collision notification signal, and a selection circuit provided for each output port and converts the output signal of the selection circuit into electricity/optical to the corresponding output port. 1. A star coupler device comprising: an electric/optical conversion circuit that supplies electricity to the light source;