JPH02246532A - Optical transmission system - Google Patents

Abstract

PURPOSE:To effectively cope with the disconnection of a transmission line by fetching the bidirectional signal of an optical transmission line to slave stations and outputting signals from the slave stations in the two directions of the optical transmission line while holding the signal level of the optical transmission line almost constant over the entire range. CONSTITUTION:The optical transmission line 10 forms a closed loop and one terminal (start terminal) 10a and the other terminal (end terminal) 10b are connected to a control master station 11. Then while the same signal is simultaneously inputted from the key station 11 in the two directions from the start terminal 10a and end terminal 10b of the optical transmission line 10 to hold the signal level of the optical transmission line 10 nearly constant over the entire area, bidirectional signals of the optical transmission line 10 are inputted and supplied to a slave station 12 and the signal from the slave station 12 is outputted in the two directions of the optical transmission line 10. Consequently, even if the optical transmission line 10 is disconnected, the key station 11 and each slave station 12 can interchange information with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an optical transmission system, and more particularly to an optical transmission system suitable for a system that uses an optical transmission line and performs information control by branching into many branches along the way.

(Prior Art) An example of a system that uses an optical transmission line and controls information by branching into many branches along the way is an abnormality monitoring system for power distribution lines. As shown in Fig. 7, the power distribution lines are connected from the transformer 2 of the distribution substation 1 to the power distribution lines 4.4, . . . via a plurality of circuit breakers 3.3, . , power switches 5 are connected in series to each of these power distribution lines 4 at appropriate intervals. The system for monitoring abnormalities in the power distribution line 4 installs a control master station 7 in the substation 1, and lays an optical transmission line 8 as an information transmission path from the control master station 7 along the electric power wA4. Control slave stations 9 for controlling the opening and closing of the switches 5 are respectively installed and connected to the optical transmission line 8.

The control master station l exchanges information with each control slave station 9 and connects the power line 4.
If an abnormality such as dielectric breakdown or disconnection failure occurs in the power line 4, a control signal (command) is output to the control slave station 9 in the section where the abnormality has occurred, and the power switch 5
The area will be opened and power supply to the area will be cut off. Such an abnormality monitoring system is installed for each power line 4.

(Problem to be Solved by the Invention) By the way, in the conventional abnormality monitoring system described above, the optical transmission line 8 is an open loop, and the control master station 1
In this case, information is supplied to each control slave station 9 only from one end of the optical transmission line 8. Furthermore, since each control slave station 9 is branch-connected from the optical transmission line 8, the signal level of the optical transmission line 8 decreases each time it passes through each brancher due to branching loss.
The farther away from the control master station 1, that is, the longer the transmission distance, the more difficult it becomes to detect the received signal level. Therefore, it is necessary to exchange and confirm information many times or to perform a strict level check, which not only takes time for information control but also makes the circuit configuration of the control slave station 9 complicated and expensive.

Furthermore, if the optical transmission line 8 is disconnected, it becomes impossible to exchange information with the control slave station 9 after the disconnection point, resulting in problems such as information loss and inability to control the power switch 5.

The present invention has been made in view of the above points, and provides an optical transmission system that can compensate for a drop in signal level due to transmission distance and branch loss, and can also effectively deal with disconnections in transmission lines, etc. The purpose is to

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a master station and a plurality of slave stations connected to the master station via an optical transmission line, In an optical transmission system in which information is exchanged between a master station and a slave station, the optical transmission line is formed into a loop, and the same signal is transmitted simultaneously in both directions from the master station to the start and end of the optical transmission line. While the signal level throughout the optical transmission line is kept at a substantially constant level, the bidirectional signals of the optical transmission line are taken in and input to the slave station, and the signals from the slave station are input to the two-way signals of the optical transmission line. This is how it is output.

(Function) By forming the optical transmission line into a loop and simultaneously inputting the same signal in both directions from the master station to the start and end ends of the optical transmission line, the signal level decreases due to the transmission distance of the optical transmission line.
Branch losses at each branch point are compensated. As a result, the signal level (light amount) of the optical transmission line is maintained at a substantially constant level over the entire area. By connecting each slave station so that bidirectional signals of this optical transmission line can be input simultaneously, the level of the manual signal of these slave stations is increased. Further, the signals output from each slave station are transmitted in both directions of the optical transmission line, and even if the optical transmission line is disconnected, information can be exchanged between the master station and each slave station.

(Example) An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an optical transmission system according to the present invention, in which an optical transmission line 10
forms a closed loop, and one end (starting end) 10 a and the other end (am) 10 b are connected to the IJmaJi 521. This optical transmission line 10 is laid, for example, along the above-mentioned power distribution line. A plurality of branch points are provided at predetermined intervals along the optical transmission line 10, for example, four branch points A to D are provided at equal intervals. A control slave station 12 is connected to each of these branch points A to D via a branch 13 and a branch line 14.

As shown in FIG. 2, the branch 13 includes, for example, three Y
Input ports 15a, 1 of the 0 splitter 15.16 constituted by a type splitter 15.16 and a mixer 17
6a and output ports 15b, 16b are connected in series to the optical transmission line 10, and each branch port 15c, 16c is connected to a mixer 17.
is connected to each input port 17a, 17b. The output port 17c of this mixer 17 is connected to the control slave station 12 via the branch line 14.

The splitter 15 branches the signal S from the information signals S transmitted clockwise along the optical transmission line 10 as indicated by the arrow C in FIG. Further, the splitter 16 branches the signal S° from the information signal S° that is transmitted in the counterclockwise direction of the optical transmission line 10 as indicated by the arrow CC in the figure, which is opposite to the splitter 15. and,
The mixer 17 receives these two branched signals s and s'
are mixed to form signal S1.

In the branching device 13, the power ratio between the optical transmission line (main line) 10 and the branching line 14 is set to, for example, about 1O:l, and (1/10) of the signal S input to the branching device 13 is branched. &
1114, and (1/10-α) passes through the main line. Here, the value α represents the structural loss (branching loss) of the branching device 13, and each of the other branching devices 13 is similarly configured.

The optical transmission line 10 receives the same information signal S18'' simultaneously at the starting end 10a and the ending end 10b, and the signal levels (light amounts) P and P' of these information signals s and s'.
are set to be the same (PP').

By the way, as shown in FIG.
The signal S input from a is sequentially attenuated by transmission line loss and power loss by each branch 13 at each branch point A to D connected on the way before reaching the terminal 10b.
The signal level P is from P at the starting end 10a to P4 to P,
It decreases in a stepwise manner as shown by the broken line. In addition, each turnout 1
The loss in No. 3 is within the range of variation and is approximately constant. Similarly, the signal S° input from the terminal end tab of the optical transmission line 10 loses power on its way to the starting end 10a, and the signal level at the terminal end 10b changes from Po to P9° to PI° as indicated by the dotted broken line. decrease as shown. Also, thin line! , ■ indicate power loss only in the optical transmission line 10.

As is clear from FIG. 3, the signal level P of the signal S going from the starting end 10a to the ending end 10b of the optical transmission line IO and the signal S' going from the ending end 10b to the starting end 10a.
, P' change symmetrically. Therefore, when these two signals S and S'' are added, the signal level becomes equal to the optical transmission line l.
At each point of O, a substantially constant level P3 is reached, which is represented by a solid line ■. Note that the reference numeral in the figure indicates the length of the optical transmission line 10.

The levels P and P' of the signals s and s' input to the starting end 10a and the ending end 10b of the optical transmission line IO are basically arbitrary. However, the branch point A-D of the optical transmission line 10 is
If the optical transmission line 10 is disposed at an asymmetric position with respect to the control master station 11, or due to variations in branching loss of each branching device 13, the signal level in the middle of the optical transmission line 10 may become high.
It gets lower. Therefore, even in such a case, it is preferable to adjust the input signal level so that the signal level at any point on the optical transmission line IO is constant or approximately constant within the range of variation. In this embodiment, the branch points A to D are symmetrically arranged at equal intervals on the optical transmission line 10.

Also, the signal levels P, P' (P-P
') is applied to each controlled slave station even if the branched signal 3 or S'' is at the signal level P1 or PI' at the branch point or 8, respectively, and only one of them is input. 12, the signal level is set to a detectable level.

The action will be explained below.

In a normal state where the optical transmission line 10 is not disconnected, the control master station 1 simultaneously inputs the same information signals s and s' from the start end 10a and the end end 10b of the optical transmission line 10. Each splitter 13 at each branch point A to D of the optical transmission line 10 branches the signal S1S° of the optical transmission line 10 and takes it into each branch line 14. For example, to explain the branching device 13 at the branch point A closest to the starting end 10a of the optical transmission line 10, as shown in FIG. 15 branches a part of the signal S from the optical transmission line 10 to obtain a captured signal S. Further, the other branching device 16 branches a part of the signal S° and takes it in to obtain a signal S'. The mixer 17 mixes these signals S and 3° and outputs the mixed signal S l 1 to the branch line 14 to be applied to the control slave station 12 .

By the way, the signal levels of the signals S and S'' transmitted to the optical transmission line 10 decrease as shown in FIG. 3, and at the branch point A, the level of the signal S is P4, and the level of the signal S'' is P
lo, and the branched signals s and s' also have corresponding levels p4 and pI'. Therefore, the signal level of the signal S" output from the mixer 17 is <pa "p+'
>, and the level p3 corresponds to the signal level P3 of the optical transmission line IO. That is, the reduction in signal level and branching loss due to the distance of the optical transmission line 10 are compensated for. As a result,
The level of the signal S' input to the control slave station 12 is
Or in the case of S' alone, that is, the signal S or So is sent to the optical transmission line 10.
This is significantly higher than when only one of the signals is transmitted alone.

Therefore, the control slave station 12 connected to the branch 13 at the branch point A receives the information signal S l whose signal level is sufficiently high.
1 can be received, and information exchange with the control master station 1 becomes easy. The same applies to the other branch points BD as in the case of the branch point A.

Furthermore, if the optical transmission line 10 is disconnected, for example, at a point Q between branch points C and D, each branch 13 at the branch points A to C receives the signal S, and the branch at the branch point 1
3 takes in the signal S. The signal levels at the branch points A, B, and C of the signal S are Pa and Ps as shown in FIG.
, Pg, the signal level P4 at branch point A is the highest, and the signal level P! at branch point C is the highest. However, the signal level Pt at the branch point C is higher than the signal level P of the signal S at the branch point before the optical transmission line 10 is disconnected (Pg > p, ) *On the other hand, the signal level Pt at the branch point C The level at the branch point A is P#', which is at the same high level as the branch point A.

Therefore, even if the optical transmission line 10 is disconnected, the control master station 1
The control slave station 12 which is farthest from the control slave station 1 can input a signal of a higher level than the signal level of the branch point which is further away than the control slave station before the wire is disconnected. Information can be exchanged with the B master station 11. Of course, each of the control slave stations 12 at other branch points A, B, and D can exchange information with the control master station 11. As a result, even if the optical transmission line 10 is disconnected, it is possible to eliminate information loss, uncontrollability, etc. after the disconnection point (hereinafter referred to as a "break point").

By the way, the signals s and s' have a transmission speed V (m/μs
), and even if these signals s and s' are simultaneously transmitted manually from both ends 10a and 10b of the optical transmission line 10, a transmission time is required until they reach the middle of the transmission line 10. Now, as shown in FIG. 4, the transmission time of the signal S18'' required from the starting end 10a of the optical transmission line 10 to the point Q at the distance X is defined as Ll,jx,
If the time difference is Δt, then t+ −X/V, tz −(L
L) /V.

For example, this time difference Δt corresponds to the rise or fall of a signal.
Gives a shifter-like variation. Therefore, this time difference Δt
However, if this can be ignored compared to the base signal (time, amplitude), this transmission method is applicable.

Therefore, if the information transmission speed of the base signal S18'' is W (bit/see), one signal is 1 /
W (sec), and the maximum value axΔt of the time difference Δt is (L/V), so 0<(L/V
) /(1/j1) < (1/2), and (2L/V) < (1/W).

By the way, V=200 (m/Jls), L-10k
-, then W<JOk (bps), the information on the controlled slave station is based on the control contents such as switching control of the power switch etc.
Several hundred (bit/5ec) ~ 10k (bit/5ec)
) is sufficient.

Therefore, if fmΔt/(1/W) is smaller than about 1/2, the control slave station as shown in FIG.
Even if the information signals s and s' are transmitted from the same direction, and the rise or fall time of the signal fluctuates by the time τ to some extent like a shifter, the signal cannot be detected at the control slave station. has almost no effect on the signal, and rectangular wave signals can be identified. Here, the value r is a value obtained by dividing the signal arrival time difference by the signal width, and represents the fluctuation ratio with respect to the signal.

Also, any location on the optical transmission line IO, for example, each branch point A-
By connecting an optical level detector that measures the levels of the signals s and s' on the optical transmission line 10 to D, and measuring the levels P, ~P, , P#' ~P at these points,
It is possible to detect the presence or absence of a break in the optical transmission line 10 and the location of the break (break point).

That is, as shown in FIG. 6, the starting end 10a of the optical transmission line 10
If the wire is broken at a point Q at a distance aX from the branch point C
, D are P2,p,1, and the difference ΔP is ΔP””P#' Pg.

Therefore, by measuring this level difference ΔP, it is possible to know whether or not the optical transmission line 10 is disconnected.

Also, the following formula %formula% From this, the distance #X, that is, the position of the cutting point Q can be known.

Note that in the above case, the breaking point Q can be specified to be between the branching points C and D. Of course, by arranging a large number of light level detectors, it becomes possible to measure the distance lIX more accurately. Note that the value P represents the level when the optical transmission line 10 is not disconnected, that is, when it is normal.

In addition, depending on the case, the starting end 10a and the ending end J of the optical transmission line 10
When the amount of received light is too large on the ob or transmitting/receiving side, an isolator may be placed.

(Effects of the Invention) As explained above, the present invention includes a master station and a plurality of slave stations connected to the master station via an optical transmission line, and between these master stations and slave stations. In an optical transmission method for exchanging information, the optical transmission line is formed into a loop, and the same signal is simultaneously input from the master station in both directions from the start and end of the optical transmission line to transmit information over the entire area of the optical transmission line. By keeping the signal level at a substantially constant level, capturing the bidirectional signals of the optical transmission line and inputting them to the slave station, and outputting the signals from the slave station in both directions of the optical transmission line, It is possible to compensate for the drop in signal level due to the transmission distance of the optical transmission line and the branching loss at each branch point, making it possible to increase the signal reception level at each slave station and making it easier to exchange information with the master station. can do.

Moreover, changing the transmission path, changing the branch point position, etc. poses almost no problem, and therefore, these changes can be made easily. Furthermore,
Even when the transmission line is disconnected, there are excellent effects such as being able to prevent information loss, control failure, etc. after the disconnection point.

4,

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the transmission line of the optical transmission system according to the present invention, Fig. 2 is an enlarged view of the branching device of the transmission line of Fig. 1, and Fig. 3 is the optical transmission of Fig. 1. Figure 4 is a diagram showing signal level changes at each branch point of the path, Figure 4 is a diagram showing signal transmission on the optical transmission line in Figure 1, and Figure 5 is a diagram showing transmission signals on the optical transmission line in Figure 1. , FIG. 6 is a diagram showing a method for detecting disconnections and disconnection locations in the optical transmission line of FIG. 1, and FIG. 7 is a block diagram of a conventional power distribution line abnormality monitoring system. DESCRIPTION OF SYMBOLS 1... Distribution substation, 2... Transformer, 3... Circuit breaker, 4... Power distribution line, 5... Switch, 1o... Optical transmission line, 11... Control Master station, 12... Control slave station, 1
3.15.16... Brancher, 17... Mixer, 14
...branch line, A-D...branch point, Q...break point, s
, s'...signal. Figure 3 Figure 4

Claims (1)

[Claims] In an optical transmission system that has a master station and a plurality of slave stations connected to the master station via an optical transmission line, and in which information is exchanged between the master station and the slave stations, the optical transmission line is looped. The master station simultaneously inputs the same signal in both directions from the start and end of the optical transmission line to maintain a substantially constant signal level throughout the optical transmission line; An optical transmission system characterized by capturing bidirectional signals and inputting them to the slave station, and outputting signals from the slave station in both directions of the optical transmission line.