JPH0215144B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a novel data transmission system that applies optical communication to a multi-drop transmission system and performs data transmission between stations using optical communication.

[Technical background of the invention and its problems]

Conventionally, when transmitting data between stations using optical communication, a ring path method is often used. FIG. 1 is a diagram showing an example of the configuration of a ring bus type data transmission system. In this data transmission system, stations S1 to S4 are connected in a ring shape by an optical fiber transmission line L to transmit data, as shown in FIG. However, in such a ring bus type data transmission system, for example, as in a data highway for an instrumentation system, a failure in one station may stop the data transmission function of other stations. For this reason, when such a transmission outage has a large impact on others, a multi-drop data transmission system is often used. FIG. 2 is a diagram showing an example of the configuration of a multi-drop type data transmission system. This data transmission system consists of stations S5 to Sn as shown in Figure 2.
are connected by an electrical transmission line E. If optical communication technology is adopted for this multi-drop data transmission system due to its advantages, it is necessary to use advanced technologies such as optical splitters or star couplers, and these optical communication devices are As the number of installations increases, the number of such devices increases, which increases the cost and also increases the amount of attenuation of optical communication signals. Also,
Essentially, the drawback is that electrical signals and optical signals cannot be transmitted together.

[Purpose of the invention]

In order to eliminate the above-mentioned drawbacks, the present invention performs data transmission on the required lines between stations by optical communication without changing the hardware and software of the stations of a multi-drop data transmission system, and also connects the electrical system and optical system. An object of the present invention is to provide a data transmission system that can perform mixed data transmission.

[Summary of the invention]

The present invention provides electrical-to-optical mutual conversion means in required lines between stations in a multi-drop transmission system, and uses this electrical-to-optical mutual conversion means to convert an electric signal from the station and an optical signal from a station other than the station. A first-arrival determination circuit determines which of the converted electric signals was input first, and based on the first-arrival signal from the first-arrival determination circuit, if the electric signal arrives first, the electric signal is divided into branching means. If an electrical signal converted from an optical signal arrives first, this electrical signal is sent to the electrical transceiver via a branch circuit, thereby converting the received electrical signal and optical signal into optical signals. Furthermore, when the electric signal is transmitted from the electric transmitter/receiver, even if the signal flows backward from the electric transmitter/receiver to the first-come-first-served determination circuit due to the electrical induction, the first-come-first-served signal will not be sent. This is a data transmission system that has the function of preventing reverse flow of signals.

[Embodiments of the invention]

The first embodiment of the present invention will be explained below with reference to FIGS.
This will be explained with reference to FIGS. 5a and 5b. Note that the same parts as in FIG. 2 are given the same reference numerals and detailed explanations will be omitted. FIG. 3 is a configuration diagram of a data transmission system according to the present invention. This data transmission system is constructed by providing an electrical-to-optical mutual converter ELT and an optical fiber transmission line L on the electrical transmission line E of the multi-drop type data transmission system shown in FIG.

FIG. 4 is a block diagram of the electric-optical mutual converter ELT. This electrical-optical mutual converter ELT is
It is composed of an electrical transmitting/receiving section 10, an optical transmitting/receiving section 20, a first-come-first-served determination circuit 30, a branch circuit 40, a waveform shaper 50, and an oscillator 60. The electrical transmitter/receiver 10 transmits electrical signals from, for example, a coaxial cable to the electrical receiver 1 via a pulse transformer 11.
2 and first-come-first-served judgment circuit 30 and branch circuit 4
The optical signal is converted into an electrical signal by the optical system transmitting/receiving section 20 and is output from the electrical system driver 13 via the pulse transformer 11. The optical system transmitter/receiver 20 transmits the optical signal from the optical fiber transmission line L to the optical receiver 21.
first-come-first-served judgment circuit 30 and branch circuit 40
The electrical signal received by the electrical transmitter/receiver 10 is waveform-shaped by the waveform shaper 50, converted into an optical signal by the optical transemitter 22, and sent to the optical fiber transmission line L. The first arrival determination circuit 30 includes electrical system and optical system transmitting and receiving sections 10 and 2.
It is constructed from a flip-flop and a logic circuit to determine which of the signals from 0 is input first, and outputs the electrical system and optical system first arrival based on the signal input first. As shown in FIG. 4, when the electrical system first-arrival signal A2 is input, the branch circuit 40 sends the signal from the electrical system transmitting/receiving section 10 to the optical system transmitting/receiving section 20 via the waveform shaper 50, and also receives the electrical system first-arriving signal B2. It is composed of AND gates 41 to 44 and an OR gate 45 so as to send a signal from the optical system transmitting/receiving section 20 to the electrical system transmitting/receiving section 10 via the waveform shaper 50 when input. The waveform shaper 50 is composed of a flip-flop and a gate circuit, and shapes the signals from the electrical and optical system transmitting/receiving sections 10 and 20 into distortion-free signals based on the signal from the oscillator 60. The oscillator 60 sends a constant frequency signal to the first-come-first-served determination circuit 30 and the waveform shaper 50 to stabilize the operation.

Next, the operation of the system configured as above will be explained. First, the case of converting an electrical signal into an optical signal and outputting it will be explained. The electrical signal from the coaxial cable is received by the electrical receiver 12 via the pulse transformer 11, and is converted into a required logic level by the electrical receiver 12, resulting in a signal A1 as shown in FIG.
and sent to branch circuit 40. At this time, no optical signal is input to the optical system transmitting/receiving section 20 because of half-duplex transmission of electrical signals and optical signals. Therefore, the first-arrival determination circuit 30 outputs the electrical first-arrival signal A2 of "1" shown in FIG. 5a to the AND gates 41 and 42.
In this way, the AND gate 41 is turned on, and the signal A1 from the electrical transmitter/receiver 10 is output to the OR gate 4.
5 to the waveform shaper 50. This waveform shaper 50 shapes the pulse to a regular pulse width, and this shaped signal passes through the AND gate 42 to become the signal A3 shown in FIG. 5a, which is sent to the optical transemitter 22 and converted into an optical signal. An optical signal corresponding to the electrical signal is output to the optical fiber transmission line L.

Next, the operation of converting an optical signal into an electrical signal will be explained. The optical signal from the optical fiber transmission line L is received by the optical receiver 21, converted by the optical receiver 21 into a logical signal B1 corresponding to the optical signal, and sent to the first-come-first-served determination circuit 30 and the AND gate 43. At this point, no electrical signal is input for half-duplexing, similar to the case where the electrical signal described above is received. As a result, the first-arrival determination circuit 30 outputs the electrical first-arrival signal B2 to the AND gates 43 and 44. Therefore, the AND gate 43 becomes ON and the logic signal B1 from the optical receiver 21 becomes OR.
After being sent to the waveform shaper 50 through the gate 45 and subjected to waveform shaping, the fifth
The signal B3 as shown in FIG. b is sent to the electrical driver 13. As a result, pulse transformer 1
1, a signal converted into an electrical signal is output.

The above electrical-optical conversion is performed, and for example, an electrical signal from the station S5 shown in FIG. The electric-to-optical mutual converter ELT2 converts the optical signal into an electric signal, thereby sending the data from the station S5 to the station S6. By the way, when transmitting an electrical signal from the electrical system transmitter/receiver 10, the signal output from the electrical system driver 13 is input to the pulse transformer 11, and a part of the signal is transmitted to the electrical system receiver 12 due to the induction effect of the pulse transformer 11. may appear and be sent to the first-come-first-served determination circuit 30. At this time, since the signal input from the electrical receiver 12 to the first-arrival determination circuit 30 is input later than the signal from the optical receiver 21, the electrical first-arrival signal B2 is never output. Therefore, backflow of signals when transmitting electrical signals from the electrical transmitting/receiving section 10 is prevented.

Note that data transmission in the multi-drop data transmission system is performed by providing a predetermined period of no signal between one transmission frame and the next transmission frame.

According to the system configured in this way, an electric-optical mutual converter ELT is provided between the stations S5 to Sn of the multi-drop data transmission system,
Since this converter ELT converts electrical signals into optical signals and optical signals into electrical signals and transmits data, data can be transmitted without changing the hardware or liftware of stations S5 to Sn in a multi-drop data transmission system. can be transmitted.

Furthermore, this system can be easily implemented without using advanced technology such as an optical splitter or star coupler, and without being expensive.

Furthermore, since the first arrival determination circuit 30 is provided, it is possible to prevent backflow of signals when transmitting electrical signals from the electrical transmitting/receiving section 10.

Next, second and third embodiments of the present invention will be described. FIGS. 6 and 7 are configuration diagrams of second and third embodiments of this system. This system shown in FIG.
6 are provided with electrical-optical mutual converters ELT5 and ELT6, and data is partially transmitted by optical communication.This system, shown in Fig. 7, is a branch line from electrical transmission line E to station SO. G is provided with electric-optical mutual converters ELT7 and ELT8 for data transmission.

In this way, in the second and third embodiments, data can be transmitted by optical communication without changing the hardware and software of the stations S5 to Sn, as in the first embodiment. In addition, optical communication is resistant to electrical and electrical noise, so optical fiber transmission lines L can be used for transmission lines installed outdoors to prevent the effects of lightning and electrical noise.
It can prevent effects from devices that use high voltage, such as CRTs, and improve their safety.

〔Effect of the invention〕

According to the present invention, it is possible to perform data transmission on the required lines between stations by optical communication without changing the hardware and software of the stations, and it is also possible to perform duplex data transmission using signals from the electrical system and the optical system. Accordingly, it is possible to provide a data transmission system that can perform a data transfer and prevent backflow of data when transmitting electrical signals from an electrical transmitter/receiver.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a data transmission system using a ring bus method, Figure 2 is a configuration diagram of a conventional multi-drop data transmission system, and Figure 3 is a diagram of a data transmission system using a conventional multi-drop method.
The figure is a block diagram showing the first embodiment of the data transmission system according to the present invention, Figure 4 is a block diagram of an electric-to-optical mutual converter in this system, and Figures 5a and b are electric-to-optical mutual converters in this system. Waveform diagrams for explaining the operation of the mutual converter, and FIGS. 6 and 7 are configuration diagrams showing second and third embodiments of this system. DESCRIPTION OF SYMBOLS 10... Electrical system transmitting/receiving section, 11... Pulse transformer, 12... Electrical system receiver, 13... Electrical system driver, 20... Optical system transmitting/receiving section, 21... Optical receiver, 22... Optical transceiver, 30...
...First-come-first-served judgment circuit, 40... Branch circuit, 41 to 44
...AND gate, 45...OR gate, 50...
Waveform shaper, 60...oscillator.

Claims (1)

[Claims] 1. In a data transmission system in which data is transmitted between a plurality of stations using a multi-drop transmission system, an electric signal is provided between a plurality of stations for converting an electrical signal into an optical signal and converting an optical signal into an electrical signal.
A pair of optical mutual conversion means is provided via an optical fiber transmission line, and the electric-optical mutual conversion means is connected to at least an electrical transmission/reception section for the electrical signal, an optical transmission/reception section for the optical signal, and the electrical transmission/reception section. a first-come-first-served determination circuit that compares and determines arrival times of the electrical signal and the optical signal received by an optical system transmitting/receiving unit and outputs a first-arrival signal corresponding to the electrical signal and the optical signal that arrive first; and this first-come-first-served determination. and branching means for branching the signal from the electrical system transmitting/receiving section to the optical system transmitting/receiving section based on the first arrival signal from the circuit, and branching the signal from the optical system transmitting/receiving section to the electrical system transmitting/receiving section. A data transmission system featuring: