JPS6121646A - Optical data communication system - Google Patents

Abstract

PURPOSE:To simplify each terminal equipment and to quicken the deciding operation by providing a circuit detecting the presence of a transmission signal from each terminal equipment and the presence of generation of collision in an optical star coupler, and a transmission gate to be turned off only when the absence of collision of transmission signals in detected. CONSTITUTION:A transmission signal presence detecting circuit 10 generates an ON signal when a transmission signal exists and the ON signal is inputted to a transmission section 11 and a collision presence detecting circuit E. An output signal from transmission signal presence detecting circuits 10... in all channel sections C1, C2... are inputted to the collision detection detecting circuit E. When plural ON signals are inputted at the same time as the input signals and a collision between the transmission signals from plural terminal equipments occurs, it is detected and a collision generation detecting signal is generated. Only when the presence of the signal is decided by the transmission signal presence detecting circuit 10, and decided that no collision occurs by the collision presence detecting circuit E, a transmission gate of an amplifier 11c is closed and no output is generated.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an optical data communication system, and more specifically, the present invention relates to an optical data communication system, and more specifically, the present invention relates to an optical data communication system. The present invention relates to an optical data communication system configured to distribute and transmit data to terminal devices via respective receiving optical fibers.

<Prior Art> Recently, optical data communication systems have been developed that use optical fibers as data transmission paths, as described above, instead of conventional coaxial cables and the like.

FIG. 2 shows the basic configuration of a conventional optical data communication system. That is, a plurality of terminal devices PI.

P2. Optical fiber M1 for transmission from P3 and Pn, respectively.
M2. The signal transmitted via M3...M, n is sent to the receiving optical/electrical converter a, the receiving amplifier R1, and the transmitting amplifier S.
, an optical star coupler A consisting of a transmitting electric/optical converter,
centrally relayed to each terminal device PL.

P2. Optical fiber Nl for reception to P3...Pn, respectively.

N2. It is arranged to distribute and transmit via N3...Nn. In other words, the transmission signals between the terminal devices are always configured to pass through the central optical star coupler A.

By the way, in such an optical communication system, each terminal device must be able to detect a collision state between transmission signals that occurs when a plurality of terminal devices perform transmission operations simultaneously. Otherwise, a communication error will occur. Conventionally, in order to detect the above-mentioned collision state for each terminal device, the collision state is detected by software countermeasures such as a microcomputer in the device, and processing such as stopping the transmission operation or discarding the received data is executed. That's what I was doing. However, in a system having such a configuration, each terminal device requires a collision detection means, which causes problems such as a reduction in effective communication speed and an increase in system complexity and cost.

An improved technique for solving such problems is known from Japanese Patent Publication No. 59-16453, for example. As shown in FIG. 3, a collision detection device Q is provided in the optical star coupler A to detect that multiple terminal devices are transmitting at the same time based on the level of the input transmission signal. At the same time, the collision detection signal from the collision detection device Q is sent out via the gate G and the transmission amplifier S.

However, even with such improved prior art means, the following drawbacks still remain.

That is, as stated in the claims of the publication, the collision signal may be a signal with an optical level higher than that of a normal transmission signal, or a signal with an optical wavelength higher than that of a normal transmission signal. Either the method of using signals of different optical wavelengths was adopted, or if the former method was used, aging problems would be a problem and it would be difficult to set the judgment level.
If the latter method is used, not only will the determination circuit in each terminal device be extremely complicated, but it will also take a long time to make the determination.

<Purpose> The present invention has been made in view of the above-mentioned conventional situation, and its purpose is to transmit collision information sent from the optical star coupler side to each terminal device in a reliable and quick timing manner using a simple circuit. If you make it possible to judge by , it will be 7.

<Embodiment> Hereinafter, a specific embodiment of the optical data communication system according to the present invention will be described based on FIG.

In the figure, PL, P2... are multiple terminal devices,
They are connected to a central optical star coupler A via transmitting optical fibers Ml, M2, . . . and receiving optical fibers Nl, N2, . In the optical star coupler A, there are transmitting/receiving channel sections C1, C2, . A collision presence/absence detection circuit E is used to determine whether or not a state of collision has occurred, and a transmission signal transmitted from any terminal device is distributed to each terminal device PL, P2, etc. It is equipped with a transmission signal splitter F for

Next, the detailed configurations of the terminal devices PL, P2..., the respective transmitting/receiving channel units CI, C2..., the collision detection circuit E, and the transmitting signal distributor F in the optical star coupler A, and their connections will be explained. The configuration and operation will be described in detail, but each terminal device PL, P2... and each transmission/reception channel c1. C2, . . . have the same configuration, so here, a set of one terminal device P1 and its corresponding transmitting/receiving channel section CI will be explained.

In the terminal device P1, the transmission signal drives the electric/optical converter (light-emitting element) 2 by the amplifier 1, and the generated optical signal is transmitted to the optical star coupler A through the transmission/reception channel 1llc10 light via the transmission optical fiber M1. / is sent to the electric converter (light receiving element) 8. In addition, the transmission signal is sent to the reception OR circuit 3 so that it can be monitored as a reception signal at the own station if necessary.
It is also input to the AND circuit 4 for collision signal detection. 5 in the figure is a transmitting/receiving channel section C in the optical star coupler A.
An optical/optical converter (light emitting element) 1 for receiving a signal transmitted from the electrical/optical converter (light emitting element) 14 of 1 via the receiving optical fiber Nl.
It is an electric converter (light receiving element), and the received signal is
The signal is input to the reception OR circuit 3 and the collision signal detection AND circuit 4 via the amplifier 6.

In the optical star coupler A, the transmission signal from the terminal device P1 that enters the optical/electrical converter 8 of the transmitting/receiving channel section C1 is amplified by the amplifier 9, input to the transmitting signal distributor F, and then transmitted to the other channel section C2. . . are mixed with transmission signals from other terminal devices P2 . . . and sent back to each channel unit CI.

The signal is distributed to the transmitter 11 of the C2 . This transmission signal presence/absence detection circuit 10 detects the presence of a transmission signal.
An N signal is generated, and the ON signal is input to the transmitter 11 and the collision detection circuit E.

The collision detection circuit E includes all channel sections C1.
, C2..., the output signals from the transmission signal presence/absence detection circuit 10... are inputted, and when a plurality of ON signals are simultaneously input as those input signals, the output signals from the plurality of terminal devices are inputted. It is determined that a collision has occurred between the transmitted signals, and a collision occurrence detection signal is issued. The collision occurrence detection signal is input to the transmitting sections 11 of all the channel sections C1, C2, .

The transmitter 11 drives the light emitting element 14 with its output, and includes an inversion circuit 11a that receives an output signal from the collision detection circuit E, and an output signal from the inversion circuit 11a and the transmission signal detection circuit 10. The transmission signal presence/absence detection circuit 10 comprises an AND circuit 11b that receives an output signal from the AND circuit 11b, and a transmission gated amplifier 11C that receives an output signal from the AND circuit 111) and a transmission signal from the transmission signal distributor F. Only when it is determined that there is a signal and the collision detection circuit EK determines that no collision has occurred, the transmission gate of the amplifier 11C is closed (turned OFF) so that no output is output. It is composed of In other words, to explain this operation in detail: ■ When there is only a received signal from its own terminal device P1 (no collision), the transmitter 11 does not output an output, so the transmitted signal does not return to its own terminal device P1. do not have.

■ When there is no received signal from its own terminal device P1, the transmitter 11 outputs an output unconditionally. Sorry, other terminal device P
All transmission signals from 2... are sent out.

■ If there is a received signal from own terminal device P1 and there is a collision with a transmitted signal from another terminal device, the transmitted sound 1
sII outputs an output.

Looking at this from the terminal device P1, if the received signal from the optical star coupler A appears during the transmission operation, it can be unconditionally determined that a collision with the transmitted signal of another terminal device has occurred. Therefore, the circuit for collision determination in each terminal device P1, P2, . . . In this case, 41 AND circuits are sufficient,
The configuration is extremely simple, and the collision determination operation is performed extremely quickly.

<Effects> In summary, the optical data communication/system according to the present invention has the following effects:
An optical star coupler that centrally relays signals sent from multiple terminal devices via respective transmission optical fibers, and distributes and transmits the signals to each terminal device via respective receiving optical fibers. In the optical star coupler, a circuit detects the presence or absence of a transmission signal from each terminal device.

A circuit for detecting the occurrence of collision between two or more transmission signals based on the detection results output from the transmission signal presence/absence detection circuit is provided, and the transmission signal presence/absence detection circuit detects the transmission from the own terminal device. The device is characterized in that it is provided with a transmission gate that is turned OFF only when the presence of a signal is detected and the collision detection circuit detects that there is no collision between transmitted signals. Therefore, the collision determination circuit provided in each terminal device can have an extremely simple configuration, and the determination operation thereby can be performed reliably and quickly.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of an optical data communication system according to the present invention. Further, FIGS. 2 and 3 each show a circuit configuration diagram of a conventional system. PL, P2...terminal device, Ml, M2...optical fiber for transmission, A...optical star coupler, Nl, N2...optical fiber for reception, 10...transmission signal presence/absence detection circuit, E...
Collision detection circuit, 11C...Amplifier with transmission gate. Applicant: Dainichi Nippon Electric Cable Co., Ltd. Agent: Kazuhide Okada, patent attorney

Claims (1)

[Claims] An optical system configured to centrally relay signals transmitted from multiple terminal devices via respective transmission optical fibers using an optical star coupler, and distribute and transmit the signals to each terminal device via respective receiving optical fibers. In the data communication system, the optical star coupler includes a circuit that detects the presence or absence of a transmission signal from each terminal device, and a circuit that detects the presence or absence of a transmission signal from each terminal device, and a circuit that detects the presence or absence of transmission signals from at least two transmission signals based on the detection results output from the transmission signal presence detection circuit. A circuit for detecting the occurrence of a collision is provided, and the presence of a transmission signal from the own terminal device is detected by the transmission signal presence/absence detection circuit in the drive circuit of the light emitting element for outputting an optical signal, and the An optical data communication system comprising a transmission gate that is turned off only when a collision detection circuit detects that there is no collision between transmission signals.