JPH02299340A - Looped optical data transmitter and its branching repeater - Google Patents

Abstract

PURPOSE:To attain automatic changeover while ensuring proper data transmission state by detecting the decrease in a photodetection quantity level from a branched transmission line and selecting a switch while the transmission signal is not sent when the branched transmission line is parted. CONSTITUTION:The parting of a slave station or a branch transmission line is started, the photodetection level of a photoelectric converter 17 starts decreasing. Before a level reaches the photodetection level causing a transmission error, the decrease in the photodetection level is detected by a photodetection level-down detection circuit 23 and its detection signal (j) is outputted to an AND gate 27. Then untransmission of an output signal (c) from a delay circuit 13 equivalent to the branch line is awaited, and when the detection signal (k) is outputted to the AND gate 27, a changeover switch 14 is selected to a terminal (1) at a main transmission line with a switching signal (g). Thus, a slave station or a branched transmission line causing a transmission error to any transmission signal is parted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a loop-shaped optical data transmission device and a branch repeater thereof, which transmit data using a loop-shaped optical transmission path in a LAN, various types of equipment, etc. be.

BACKGROUND OF THE INVENTION For example, in recent years, automated machines have become more sophisticated through the use of microprocessors, and as a result, machines with hundreds to thousands of sensors and actuators are no longer uncommon. As a result, the amount of wiring required to transmit signals to and from the controller has increased, resulting in problems such as difficulty in responding to troubles, decreased reliability, and increased wiring man-hours.

In order to solve such problems, the applicant has filed a patent application filed in 1983.
-165830, as shown in Figure 8, the controller is the master station, input/output units for sensors and actuators are the slave stations, and the master station and multiple slave stations are connected to a transmission line using a loop-shaped optical fiber, etc. We proposed a loop-shaped data transmission device connected by

In this loop data transmission device, from the master station to the 9th
Send a transmission signal in the transmission format shown in the figure,
With the slave station configuration shown in Figure 10, when the address preset for the slave station matches the address information, the data information of the transmission signal is converted into parallel data and taken out as output data, and the input data is converted into serial data. and replace it with the data information of the transmission signal being received and send it.
If the addresses do not match, the data is sent as is, so that data can be transmitted at high speed.

Problems to be Solved by the Invention However, in the above-described loop optical transmission device in which a master station and a slave station are directly connected through a single optical transmission line, when the power of one of the slave stations is turned off, the optical There is a problem that the entire transmission line stops functioning, and another problem is that it is not possible to add or delete slave stations while keeping the optical transmission line alive.

In view of the above-mentioned conventional problems, the present invention provides a loop-shaped optical data transmission device that maintains the function of the main transmission line even when the power of the slave station is turned off, and that allows addition and deletion of slave stations while keeping the main transmission line alive. and its branch repeater.

Means for Solving the Problems In order to achieve the above object, the loop-shaped optical data transmission device of the present invention is a loop-shaped optical data transmission device in which a master station and a plurality of slave stations are connected in a loop through an optical transmission path. In the main transmission line connected in a loop to the master station, an input end from the main transmission line, a relay means, an output end for the main transmission line, and an output end from the relay means to a branch transmission line and a branch transmission line. A branch repeater equipped with an input end from the main transmission line and a switching means for the main transmission line and the branch transmission line is installed, and a single slave station or a plurality of slave stations connected by the branch transmission line are connected to the branch repeater. It is characterized by

Further, the branch repeater of the present invention is characterized in that it is provided with a received light level detection means at the input end from the branch transmission line, and the switching means is switched based on the detection signal.

Further, when connecting a branch transmission line, it is preferable to provide continuous transmission error detection means for input signals from the branch transmission line, and to switch the switching means based on the detected signal.

In addition, if the delay time due to the branch transmission line is known, an equivalent delay circuit of the branch transmission line is interposed between the relay means and the switching means, and if it is not known, the transmission signal from the relay means and It is preferable to provide frame completion detection means for detecting the end of each frame of the transmission signal inputted from the branch transmission line, and to switch the switching means based on these detection signals.

Furthermore, when leaving the branch transmission line, there is also a light reception amount down detection means that detects when the light reception level at the input end from the branch transmission line becomes below a certain value, and a transmission signal is not output from the relay means. It is preferable to provide non-transmission detecting means for detecting non-transmission, and to switch the switching means based on these detection signals.

According to the present invention, a slave station or a branch transmission line connected to a slave station is connected to a branch repeater provided on a main transmission line, and the switching means of the branch repeater is set to an appropriate transmission state. By switching to the branch transmission line side after , the main transmission line can maintain its function even if the power to the slave station is turned off, and addition and deletion of slave stations can be performed while keeping the main transmission line alive.

In addition, when connecting a branch transmission line, switching is performed when the level of light received from the branch transmission line exceeds a certain level and there are no continuous transmission errors associated with the connection operation, thereby ensuring proper data transmission status and automatic switching. can be switched.

In addition, if the delay time due to connection of a branch transmission line is known and fixed, an equivalent delay circuit of the branch transmission line may be inserted between the relay means and the switching means, and the delay time may be unknown. By detecting the end of each frame of the transmission signal from the main transmission line and the branch transmission line and switching the switching means when the transmission signal changes, it is possible to prevent transmission errors from occurring even once in data transmission on the main transmission line. A branch transmission line can be connected.

Furthermore, when a branch transmission line is disconnected, it detects that the level of light received from the branch transmission line decreases before a transmission error occurs, and switches the transmission signal while the transmission signal is not being transmitted, thereby maintaining an appropriate data transmission state. It is possible to switch automatically while ensuring the

Embodiments Hereinafter, embodiments of the present invention will be explained based on FIGS. 1 to 7.

First, the overall configuration of a loop-shaped optical data transmission device will be explained with reference to FIG. In FIG. 1, ``■'' is a master station, to which a main transmission line 2 made of a quartz optical fiber capable of long-distance transmission is connected in a loop. A plurality of branch repeaters 3 are interposed in this main transmission line 2, and branch transmission is performed in which a slave station 4 or a plurality of slave stations 4 are similarly connected to each branch repeater 3 via the branch repeater 3. 5. For this branch transmission line 5, an inexpensive plastic optical fiber for short distance transmission can also be used.

In order to transmit output data to each slave station 4 and receive input data from each slave station 4, the master station 1 transmits an asynchronous transmission signal in a transmission format as shown in FIG. 9 described in the conventional example. is converted into an optical signal and output to the main transmission line 2. The transmission signal is sequentially transmitted to each slave station 4 via each branch repeater 3.

Each slave station 4 has the configuration shown in FIG. 10 explained in the conventional example, or has any other arbitrary configuration. When the address set in advance for the slave station 4 matches the address information, the transmission signal is transmitted. Convert the data information into parallel data and take it out as output data, convert the input data into serial data, replace it with the data information of the transmission signal being received and send it, and if the addresses do not match, send it as is. It is configured.

As shown in FIG. 2, the branch repeater 3 includes a photoelectric converter 11 at the input end from the main transmission line 2, a waveform shaping circuit 12, a branch line equivalent delay circuit 13, a changeover switch 14, and the main transmission line 2. The electro-optic converters 15 at the output ends of are connected in series. Further, the output of the waveform shaping circuit 12 is branched, and the electro-optical converter 16 at the output end to the branch transmission line 5 is connected, and the opto-electric converter 17 at the input end from the branch transmission line 5 is connected to the changeover switch 14. has been done. Further, a reception light level detection circuit 1 detects the light level of the optical signal received by the optoelectric converter 17, and a continuous transmission error state detects the output signal of the optoelectric converter I7 to detect the continuous transmission error state. A detection circuit 19 is provided, and their output signals are input to a circuit switching control circuit 20 that controls switching of the changeover switch 14 between the ■ terminal on the main transmission line 2 side and the ■ terminal on the branch transmission line 5 side. There is.

Note that the waveform shaping circuit 12 is composed of a carrier generation circuit and a D-type flip-flop. In addition, the branch line equivalent delay circuit 13 similarly delays the transmission signal that simply passes through the branch repeater 3 in accordance with the delay time when the transmission signal passes through the branch transmission line 5. I try to keep the delay time the same.

Next, the operation of this branch repeater 3 will be explained with reference to the signal waveform diagram in FIG. The received signal a converted into an electrical signal by the opto-electrical converter 11 is delayed by half a clock in the waveform shaping circuit 12 and its waveform is shaped. If a slave station 4 or a branch transmission line 5 is connected to this branch repeater 3, and the selector switch 14 is connected to the ■ terminal on the main transmission line 2 side,
The output signal of the waveform shaping circuit 12 is delayed by a branch line equivalent delay circuit 13 for a predetermined period of time as an output signal C, input to an electro-optical converter 15, and transmitted to the main transmission line 2 as an optical signal.

On the other hand, when the slave station 4 or the branch transmission line 5 is connected, the output signal is converted into an optical signal by the electro-optical converter 16 and transmitted to the connected slave station 4 or branch transmission line 5. The optical signals transmitted from these are input to the opto-electrical converter 17. The received signal d output from the opto-electrical converter 17 becomes a defective transmission signal for a certain period at the beginning of the connection, and the amount of received light itself is not stable immediately after the connection is started. Therefore, the continuous transmission error detection circuit 19 and the reception light amount level detection circuit 18 detect these continuous transmission error states and unstable periods of the received light amount.
, and inputs the transmission error signal e and received light level signal f to the circuit switching control circuit 20, and outputs the switching signal g to the changeover switch I4 when a proper transmission signal can be obtained. , the appropriate transmission signals X, Y, .

In this way, transmission signals such as ASB, C, X, Y, Z, etc., which have no transmission errors before or after connection, are transmitted to the main transmission path 2 as optical signals.

In this way, by providing the continuous transmission error detection circuit 19 and the received light level detection circuit 18 together, it is possible to prevent malfunctions due to errors in detection of transmission errors, as would be the case when the continuous transmission error detection device 19 is provided alone. I can do it.

In the branch repeater 3 of the above embodiment, the delay time due to the slave station 4 or the branch transmission line 5 connected to the branch repeater 3 is known and fixed, but the delay time is unknown. In the case of a change in the structure, a configuration as shown in FIG. 4 is used. Note that the same reference numerals are given to the same components as those explained in FIG. 2, and the explanation will be omitted.

In this embodiment, instead of the branch line equivalent delay circuit 13, a frame completion detection circuit 21 for the output signal of the waveform shaping circuit 12 and a received signal d output from the opto-electrical converter 17 are used.
A frame completion detection circuit 22 is provided, and their detection signals are input to the circuit switching control circuit 20. Further, the changeover switch 14 is configured to be able to switch between the ■terminal connected to the main transmission line 2, the neutral ■terminal, and the ■terminal connected to the branch transmission line 5.

Next, the operation of this embodiment will be explained with reference to the signal waveform diagram of FIG. The received signal a is delayed by half a clock in the waveform shaping circuit 12 and its waveform is shaped. When the slave station 4 or the branch transmission line 5 is connected to this branch repeater 3 and the changeover switch 14 is connected to the ■ terminal on the main transmission line 2 side, the output signal of the waveform shaping circuit 12 is is input to the electro-optical converter 15 and transmitted to the main transmission line 2 as an optical signal.

On the other hand, when the slave station 4 or branch transmission line 5 is connected, the output signal is also transmitted to the connected slave station 4 or branch transmission line 5,
Optical signals transmitted from these are input to the opto-electrical converter 17. The received signal d output from this opto-electrical converter 17
The continuous transmission error state and the unstable period of the received light amount at the initial stage of the connection are detected by the continuous transmission error detection circuit 19 and the received light amount level detection circuit 18, and the transmission error signal e is detected.
and the received light amount level signal f to the circuit switching control circuit 20, and wait until a state where a proper transmission signal can be obtained;
Thereafter, the end of the frame of the output signal d is detected by the frame completion detection circuit 21, a switching signal g is output, the changeover switch 14 is switched to the ■ terminal, and the frame of the received signal d, which has become a proper transmission signal, is By detecting the end with the frame completion detection circuit 22, the switching signal g
is output and the selector switch 14 is switched to the ■ terminal.Then, after the transmission signal passing through the main transmission line 2 is properly transmitted, the proper transmission signals Y, Z, etc. passing through the branch transmission line 5 are output. * is input to the electro-optical converter 15 and transmitted as an optical signal. In this way, a transmission signal without any transmission error before or after connection is transmitted to the main transmission line 2 as an optical signal.

Here, if the master station l is configured to transmit the next transmission signal after the previously transmitted transmission signal returns, and the signal does not return even after a certain period of time has passed after transmitting the transmission signal, is configured to retransmit the same transmission signal.

In the embodiment described above, a configuration was shown in which the slave station 4 or the branch transmission line 5 is connected. Next, a configuration in which the slave station 4 or the branch transmission line 5 is disconnected without causing a transmission error will be explained with reference to FIG. Note that the same reference numerals are given to the same components as those explained in FIG. 2, and the explanation will be omitted.

In this embodiment, if the level of the amount of light received by the opto-electrical converter 17 decreases, a light reception amount down detection circuit 23 is provided which detects this at a stage before a transmission error occurs. The received light amount down detection circuit 23 includes a comparator 24b to which the received light amount level signal from the opto-electrical converter 17 and the level signal from the detection level setter 24a are input, and a peak hold circuit 25. In addition, a non-transmission detection circuit 26 is provided to detect a period in which the output signal C from the branch line equivalent delay circuit 13 is not being transmitted. The detection signal k from the circuit 26 is inputted to the AND gate 27, and the output signal is used as the switching signal g to be applied to the changeover switch 14.
is switched from the ■ terminal to the ■ terminal.

The operation of this embodiment will be explained with reference to the signal waveform diagram in FIG. When the slave station 4 or the branch transmission line 5 starts to disconnect, the level of the amount of light received by the opto-electrical converter 17 begins to decrease. Before the received light amount level reaches a level at which a transmission error occurs, this decrease in the received light amount level is detected by the received light amount level down detection circuit 23.
The detection signal j is output to the AND gate 27. Thereafter, wait until the output signal C from the branch line equivalent delay circuit 13 is not being transmitted, and when the detection signal k is output to the AND gate 27, the changeover switch 14 is switched to the main transmission path 2 side by the switching signal g. It can be switched to the ■ terminal.

(Thus, the slave station 4 or the branch transmission line 5 can be disconnected without causing a transmission error in any transmission signal.

The embodiment shown in Fig. 6 corresponds to the embodiment shown in Fig. 2 in which the delay time due to the slave station 4 or the branch transmission line 5 is known and fixed, but if these are unknown or change. In this case, a frame completion detection circuit similar to the embodiment shown in FIG. 4 may be used in place of the non-transmission detection circuit 26, and a similar structure may be used.

In the above embodiments, the case where the slave station 4 or the branch transmission line 5 is connected as shown in FIG. 2 or FIG. 4, and the case where it is separated as shown in FIG. 6 have been explained separately. If there are both possibilities, it goes without saying that both configurations may be implemented in combination.

In addition, in the example shown in FIG. 1, only the branch repeater 3 is interposed on the main transmission line, but in some cases, the slave station 4 may be directly interposed on the main transmission line 2 as in the conventional case. Branch repeaters 3 may be installed only in parts where there is a possibility of additional connections or disconnections. In this case, the power supply of the slave stations 4 directly connected to the main transmission line 2 If it breaks, the main transmission line 2
Although data transmission by the substation 4 is interrupted, it is possible to add or delete slave stations 4 as desired.

Furthermore, the configuration of the slave station 4 is not limited to that shown in FIG.
Any configuration can be applied. The same applies to the configuration of the master station 1.

Further, in this embodiment, the main transmission path is a quartz optical fiber, but an inexpensive plastic fiber may also be used.

Effects of the Invention According to the loop-shaped optical data transmission device of the present invention, as is clear from the above description, it is possible to connect a slave station or a branch transmission line connected to a slave station to a branch repeater provided on the main transmission line. At the same time, the switching means of the branch repeater is switched to the branch transmission line side after proper transmission conditions are obtained, so that the main transmission line maintains its function even when the power to the slave station is turned off. , and it is possible to add and delete slave stations while keeping the main transmission path alive.

Further, according to the branch repeater of the present invention, when the branch transmission line is connected, the level of light received from the branch transmission line exceeds a certain level,
Furthermore, by performing the switching at the time when there are no continuous transmission errors associated with the connection operation, it is possible to automatically switch while ensuring a proper data transmission state.

In addition, if the delay time due to connection of a branch transmission line is known and fixed, an equivalent delay circuit of the branch transmission line may be inserted between the relay means and the switching means, and the delay time may be unknown. By detecting the end of each frame of the transmission signal from the main transmission line and the branch transmission line and switching the switching means when the transmission signal changes, it is possible to prevent transmission errors from occurring even once in data transmission on the main transmission line. Branch transmission lines can be connected without any trouble.

Furthermore, when a branch transmission line is disconnected, it detects that the level of light received from the branch transmission line decreases before a transmission error occurs, and switches the transmission signal while the transmission signal is not being transmitted, thereby maintaining an appropriate data transmission state. It has great effects, such as being able to switch automatically while ensuring the same.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the loop-shaped optical data transmission device of the present invention, FIG. 2 is a configuration diagram of a branch repeater when the delay time due to the connected branch transmission line is known, and FIG. Figure 4 is a configuration diagram of the branch repeater when the delay time due to the connecting branch transmission line is unknown, Figure 5 is the signal waveform diagram, and Figure 6 is the signal waveform diagram when leaving the branch transmission line. 7 is a diagram of the corresponding signal waveform, FIG. 8 is an overall diagram of the conventional loop-shaped optical data transmission device, and FIG. 9 is an explanatory diagram showing the same transmission format. The figure is a schematic configuration diagram of the slave station. 1... Master station, 2... Main transmission line, 3...
...Branch repeater, 4...Slave station, 5...
...branch transmission line, 11...optoelectric converter C main transmission line input end), 12...waveform shaper, engineering 3...
... Branch line equivalent delay circuit, 14 ... Changeover switch, 15 ... Electro-optical converter (main transmission line output end), 16 ... Electro-optical converter (branch transmission line output end), 17... electro-optical converter (branch transmission line input end), 18... received light level detection circuit, 1
9... Continuous transmission error detection circuit, 20...
... Circuit switching control circuit, 21.22 ... Frame completion detection circuit, 23 ... Light reception amount down detection circuit, 26 ... Non-transmission detection circuit. Agent Patent attorney Shigetaka Awano 1 idiot Figure 1 Figure 8

Claims (6)

[Claims] (1) In a loop optical data transmission device in which a master station and multiple slave stations are connected in a loop through an optical transmission line, an input terminal from the main transmission line is connected to the main transmission line connected in a loop to the master station. and a branch repeater comprising a relay means, an output end for the main transmission line, an output end from the repeater means to the branch transmission line, an input end from the branch transmission line, and switching means for the main transmission line and the branch transmission line. 1. A loop-shaped optical data transmission device characterized in that a plurality of slave stations connected to a branch repeater via a single or branch transmission line are connected to the branch repeater. (2) The input end from the main transmission line, the relay means, the output end for the main transmission line, the output end from the relay means to the branch transmission line, the input end from the branch transmission line, the main transmission line and the branch transmission line. A branch repeater for a loop-shaped optical data transmission device, comprising a switching means, a receiving light level detection means at an input end from a branch transmission line, and switching the switching means based on a detection signal of the detection signal. . (3) Branching of the loop-shaped optical data transmission device according to claim 2, characterized in that continuous transmission error detection means for the input signal from the branch transmission line is provided, and the switching means is switched based on the detected signal. Repeater. (4) A branching repeater for a loop-shaped optical data transmission apparatus according to claim 2 or 3, characterized in that an equivalent delay circuit of a branching transmission line is interposed between the repeating means and the switching means. (5) Frame completion detection means is provided to detect the end of each frame of the transmission signal from the relay means and the transmission signal input from the branch transmission line, and the switching means is switched based on these detection signals. Claim 2 characterized by
or a branching repeater of the loop-shaped optical data transmission device according to 3. (6) Received light amount down detection means for detecting when the received light amount level at the input end from the branch transmission line becomes below a certain value;
A branch of a loop-shaped optical data transmission device, characterized in that a non-transmission detection means is provided for detecting that a transmission signal is not output from the relay means, and the switching means is switched based on these detection signals. Repeater.