JPS61121546A - Loop type optical transmitter - Google Patents

Abstract

PURPOSE:To prevent the effects of a fault of a slave station on the entire system by always branching signals given from the preceding stations through each slave station by means of an optical means. CONSTITUTION:In a normal mode, signals sent from an input terminal 201 are processed by a controller at a slave station and then delivered through an output terminal 203. In case the preceding station stops the signal transmission or transmits random signals, a fault is detected and no synchronizing pulse 302 is delivered. Furthermore, the output of a timer 303 is set at a low level. Then the signal of a gate 210, i.e., the signal given from an input terminal 202 is turned into a reception signal 5 within a switching circuit 205. The signal 5 is branched optically to a by-pass 211 by an optical branching device 206. Thus the signal of the preceding station flows to the bypass 211 to avoid the break of a loop despite the service interruption of an O/E 207 or an E/O 208.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a loop-type optical transmission device, and particularly to a loop-type optical transmission device that takes measures against failures in a part of the loop.

[Background of the invention]

A conventional example of countermeasures against failures in loop-type optical transmission equipment is disclosed in Japanese Patent Application Laid-open No. 1983. There is one described in JP-A-58641. In this conventional example, optical input is once received by an opto-electric converter and transmitted by an electro-optic converter, and when a failure occurs, the converters are switched to be directly connected to create a bypass. However, if the converter itself ceases to operate due to failure of the bypass switching means 9 or a power outage, the loop is broken and control signals cannot be transmitted.

[Purpose of the invention]

The present invention maintains the loop configuration even when the slave station fails and the own station becomes unable to transmit control signals, or when the opto-electric conversion signal or electro-optic converter stops operating.
The present invention provides a loop type optical transmission device that allows other normal slave stations to receive control signals and prevents a failure of one station from affecting the entire system.

[Summary of the invention]

The whole has a double loop configuration, and each slave station has two input terminals and two output terminals. Of the two signals input to each slave station, one is branched by an optical splitter before being photoelectrically converted, bypassed as it is, and output from one output terminal. The other branched signal is converted into electricity and sent to the slave station, where it is used to control the controlled object. Signals such as feedback from the slave station after being captured are outputted from the other output terminal via the electro-optical converter. The other input signal is a signal bypassed by the previous station, that is, a signal from the second previous station, and is normally not used to control the slave station.

When the time is not normal, that is, when there is an abnormality, the other input signal, which is not used, is taken into the slave station. Abnormalities may include disconnection of the line or permanent noise on the line. Receiving random signals is also considered abnormal.

[Embodiments of the invention]

FIG. 1 is a diagram showing an embodiment of the present invention. One master station 1 and 5
An optical transmission system was constructed by connecting two slave stations 2 with a double optical fiber line 4. There is a process controller above the master station 1, and a plant to be controlled is connected below each slave station 2 via a control device 3. The process controller and the plant communicate with each other via the master station 1, transmission line 4, slave station 2, and control device 3 with data, control signals, and response signals. The master station 1 periodically outputs a frame as shown in FIG. 1(a), passes through each control device 3, and performs overall control.

The slave station 2ij has two input terminals 201 and 202, two output terminals 203 and 204, and a switch 205. Furthermore, the slave station 2 has an optical splitter (FIG. 4) that branches the light entering the input terminal 201 into two. One of these optically branched optical signals is directly sent to the output terminal 204 as an optical signal, and the other becomes an input to the optical switch 2050.

The optical switch 205 switches between the input signal from the input terminal 202 and the branched optical signal from the splitter in response to the switching signal 6 from the control device 3 . During normal operation, the switching signal 6 switches to select the branched optical signal from the splitter. When an abnormality is detected, the switching signal 6 is switched to select the optical input signal from the input terminal 202. This selected optical signal is converted into an electrical signal and becomes the input signal 5.

The slave station 2 takes in the feedback signal 7 from the control device 3 and guides it to the output terminal 203.

The control device 3ij is interposed between the slave station 2 and Flint, and sends necessary information to the plant, receives necessary information from the plant, and sends it to the slave station. Moreover, the control device 3 has a normality/abnormality determination function. A switching signal 6 is generated according to this determination result.

The data structure sent from the master station 1 to the optical fiber 4 is shown in FIG. The OF in the first area is the opening frame, and the CF in the last area is the closing frame. Between OF and CF, four data DI, D2 . D3. D4
was set. Data D1 is data for the first slave station as seen from the master station, data D2 is data for the second slave station as seen from the master station, data D3 is data for the third slave station as seen from the master station, data D4 indicates data for the fourth slave station as seen from the master station. In Figure 1, the number of slave stations is 5, so the second
Figure (a) and Figure 1 do not match. The reason may be that the data was not transmitted on the day and evening for the fifth slave station, or that the system was intended for a system with a four-station configuration instead of a five-station configuration as shown in FIG. either will do.

FIG. 2(b) shows an example in which a specific slave station 2A takes in its own data D3. It is assumed that data DI and D2 are taken in by a slave station existing before this slave station, and feedback signals DI' and D2' are added instead. The two slave stations that received the transmission signal from the higher level confirm that the data D3 is addressed to their own stations, and send the data D3 to the control device 3N under normal conditions. The three controllers send data D3' to the plant and take in feedback signals D3' from the plant. This signal D3' is placed at the position of data D3 and sent to the optical fiber 4.

The overall operation will be explained.

The master station 1 simultaneously sends transmission signals as shown in FIG. 2(a) to the dual optical fibers 4. Therefore, it is assumed that all the optical fibers 4 have no abnormality and that all the control devices do not detect any abnormality. Under this condition, each slave station transfers the optical signal from the input terminal 201 to the switch 205.
, and a feedback signal is added as data instead, which is output from the output terminal 203. On the other hand, one optical signal taken in and branched at the input terminal 201 is guided to the output terminal 204 and output. That is, under normal conditions, the output terminal 204 of each slave station 2 outputs the output signal of the preceding slave station.

On the other hand, in the event of an abnormality, the input terminal 2 is
Either the input signal from 02 is sent to the control device 3, or the optical signal branched via the branching section is outputted via the output terminal 204t-. The former occurs when the previous stage of the slave station is interrupted, and the latter occurs when the slave station or control device goes down. Note that the branch signal output from the latter output terminal 204 is one that is output regardless of whether or not the slave station or control device is down.

FIG. 3(b) shows the signal flow in a normal case, and FIG. 3(b) shows the signal flow in the case where one of the control devices fails. In a normal case, a signal from the input terminal 201 is processed by the control device 3 and output from the output terminal 203, resulting in a signal flow as shown by the solid line in FIG. 3(A). FIG. 3 (b) shows the flow of signals in the event of an abnormality, taking as an example a case where the second control device or the slave station 22 has failed. Assume that the second slave station 22 has stopped transmitting signals or is transmitting random signals. The third control device detects that the received signal does not arrive after a certain period of time or that there is an abnormality, and sends a switching signal 6 to the switching unit 205 of the third slave station 23.
issue. As a result, the slave station 22 from the input terminal 202 is bypassed, and the slave station 23 can receive the signal from the slave station 21. This bypass is optically branched and has been in place since normal times. Therefore, even if the power supply to the slave station 22 is stopped, the loop will not be broken. Furthermore, even if the wire is broken at point X in Figure (A), a loop is established along the same route.

At this time, in the signal received by the master station 1, only D2 of the data section 9 is not rewritten, as shown in FIG. 3(C). Here, the first bit of each slot D1 to D4 is set as a flag, and when the data is transmitted from the master station 1, it is set to "0", and when the data is rewritten in the control device 3, it is set to "1". Furthermore, regarding the repair of the failed second control device 32, even if the slave station 22 and the control device 32 are separated, the slave station 22 continues to bypass, which is effective for maintenance.

FIG. 4 shows details of a part of the control device 3 and the slave station 2 for realizing the above-described system. An optical splitter 206 has a function of splitting the input light into two. 207 is an opto-electrical converter (hereinafter referred to as 0/E) 208 is an electro-optical converter (hereinafter referred to as E10). 301 is a synchronization detection circuit that detects an opening frame from an input signal.

302 is a synchronization detection pulse, which is output when the synchronization detection circuit 301 detects a frame. The 303H timer normally outputs a signal at H1gh level, but if there is no pulse input 302 for a certain period of time, it outputs I, ow level. Under normal conditions, a synchronizing pulse 302 is generated periodically, and the output of the timer 303 is at high level, and the signal from the gate 209 of the switching circuit 205, that is, the signal from the input terminal 201, becomes the received signal 5. If the signal from the station is no longer received and a random signal is output, the synchronization detection circuit 301 does not output the synchronization pulse 302i and the timer 3
The output of 03 becomes [, OW level. Then, in the switching circuit 205, the signal of the gate 21o, that is, the input terminal 20
The signal from 2 becomes the received signal 5. Although the above example uses a timer and a gate, other means may be used as long as an abnormality in the received signal can be detected, and the switching unit 205 may also be a relay.

As mentioned above, since the optical splitter 206 is used to bypass the signal, even if the O/E 207 or Elo 208 stops working due to a power outage, the signal from the previous station will still be flowing through the bypass path 211, and the loop will be broken. There's nothing wrong.

Further, even if a parity error or the like is detected in the received data, it is possible to prevent unnecessary control by performing switching.

In addition to the meaning of the status signal from the plant, the feedback signal also includes response signals and various food data.

〔Effect of the invention〕

According to the present invention, each slave station always branches the signal from the previous station by optical means, so even if the slave station fails and the power supply is completely cut off, the transmission line will not be disconnected. It would be effective if it were possible to prevent a failure occurring at a slave station from affecting the entire system.

[Brief explanation of drawings]

Figure 1 is an overall embodiment of the present invention, Figure 2 (b) is an explanatory diagram of the format of the transmission signal, Figure 2 (b) is the slave station intake side, and Figure 3 (a) is the normal state. Transmission route (B) is a diagram showing a transmission path during an abnormality, (C) is an explanatory diagram of a transmission signal during an abnormality, and FIG. 4 is a diagram showing a detailed hardware embodiment of the slave station transmission device of the present invention. DESCRIPTION OF SYMBOLS 1... Master station, 2... Slave station, 20i, 202... Input end, 203.204... Output end, 205... Switching circuit, 206... Optical branching device, 207...・0/E converter, 208... E10 converter, 3... Control device, 4
...Optical fiber transmission line, 5... Received signal, 6...
switching signal, 7... transmission signal, 8... opening frame, 9... data section, 10... switching frame.

Claims (1)

[Claims] A master station having first and second output terminals and first and second input terminals; first and second output terminals and first and second input terminals; The master station and the plurality of slave stations are connected in a loop, and between adjacent stations, the first output terminal of the upper station and the first output terminal of the lower station are connected. 1 input terminal of the upper station, and a second output terminal of the upper station and a second input terminal of the lower station by optical fibers, and A control device serving as a terminal of each slave station, and a branching device for branching an optical signal input to its own first input terminal into the control device side and its own second output terminal side. a switch that switches between the optical compatible signal input to its second input terminal and the branched optical compatible signal for the control device side according to the presence or absence of a failure and sends it to the control device, and feedback from the control device. A loop optical transmission device comprising: a path for guiding a signal (response signal) to a first output terminal of the device. 2. The above-mentioned abnormality includes a disconnection of the optical fiber and an abnormality of the slave station or the control device, and the loop optical transmission according to claim 1, wherein the determination of the abnormality is made by the control device. Device.