JPH04328930A - Duplex type optical transmission system - Google Patents

Abstract

PURPOSE:To provide a fault avoidance function to the system by using 2 systems of optical fiber transmission lines especially so as to make the transmission lines in duplicate with respect to the transmission system having loop optical fiber transmission lines. CONSTITUTION:Captions 10A, 10B, 10C and 10D are slave nodes and connected to optical transmission lines 1, 2 of duplex loop while a master node 9 is placed as the center. The master node 9 outputs as optical signal to the optical transmission lines 1, 2 propagated in the opposite direction. The slave nodes 10A, 10B, 10C and 10D receive the optical signal fed through the optical transmission lines 1, 2 with an optical transmitter-receiver pair 23 connected by an optical coupler and an optical transmitter-receiver pair 24 with a relay amplifier function and output the optical signal propagated in the reverse direction to the optical transmission lines 1, 2.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a transmission system having a loop-shaped optical fiber transmission line, and in particular, a transmission system having a failure avoidance function by duplicating the transmission line using two optical fiber transmission lines. Regarding optical fiber transmission systems.

0002

[Prior Art] In a multi-drop transmission system using an optical coupler, transmission loss, branching loss, loss in the transmission path, etc. in the optical coupler cause the connection to occur within the permissible limit of the difference in optical transmission and reception levels. There was a limit to the number of nodes that could be used.

[0003] For example, as a conventional technology, there is an "optical fiber transmission system" (Patent Application No. 238103 of 1988).
There is. This technology is a transmission system having a loop-shaped optical fiber transmission line, and in particular, it is an optical fiber transmission system that has a failure avoidance function by duplicating the transmission line using two optical fiber transmission lines. In this technology, optical signals sent from the E/O (electrical/optical) converter of the master node must be received by the O/E converter of each slave node connected to the farthest position. . Therefore, the number of nodes that can be connected to the transmission path and the transmission distance (loop length) are determined within the range of optical transmission loss allowed therebetween.

0004

[Problems to be Solved by the Invention] By the way, in conventional optical transmission systems, when expanding the system by increasing the distance of a duplex transmission line or increasing the number of slave nodes connected to a transmission line, it is necessary to Therefore, a relay amplifier was required.

However, when a relay amplifier is provided, a problem arises in that a failure avoidance function must be added in the event of a failure of the relay amplifier, which complicates communication control. In addition, when trying to increase the transmission speed, the level between the transmitter and the receiver tends to decrease, causing problems such as a decrease in the number of nodes that can be connected to the transmission path and a shortening of the transmission distance (loop length). .

The present invention was made in view of the above-mentioned circumstances, and is a double loop system having a failure avoidance function that can increase the transmission speed and furthermore allow system expansion without the need for repeater amplifiers. The purpose is to provide a type optical transmission system.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention has a duplex optical transmission line using two loop-shaped optical fibers and a function for transmitting and receiving two optical signals. a first node that transmits the same signal in the opposite direction to each of the two optical transmission lines and always receives the optical signals of the two systems independently; a first optical transceiver pair that constantly receives an optical signal supplied through one of the two optical transmission lines, relays and amplifies it, and then selectively outputs it to the optical transmission line of the same system; and the other of the two optical transmission lines. The optical branching means is provided with an optical branching means for branching the optical signal supplied through the optical branching means into two, and a branching means for always receiving one of the optical signals branched by the optical branching means and outputting the other to the optical transmission line of the same system. and a plurality of second nodes inserted in the optical transmission path, and the first and second optical transceiver pairs in the plurality of second nodes. are connected to each of the two optical transmission lines so as to be arranged alternately.

[0008]

[Operation] Signals transmitted by a first node are sequentially supplied to a plurality of second nodes through two independent optical transmission lines in mutually opposite directions. At this time, the above-mentioned signal is relayed and amplified by the first optical transceiver pair at every other stage in both of the two optical transmission lines, and the optical branching means of the second optical transceiver pair at every other stage. bypassed by

[0009]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. 1 and 2 are diagrams showing the configuration of an embodiment of the present invention. FIG. 1 is a block diagram showing the overall configuration of the same embodiment. In the figure, 9 is a master node, and 10A, 10B, 10C and 10D are slave nodes. Each slave node 10A, 10B, 10
C and 10D are connected to double loop optical transmission lines 1 and 2 centered on the master node 9.

[0010] Master node 9 and slave node 10A
, 10B, 10C, and 10D is controlled by a communication processing circuit 7, and is connected to an upper level transmission device or computer (not shown) by an interface circuit 8. FIG. 2 is a block diagram showing the configuration of slave nodes 10A, 10B, 10C and 10D. In the figure, 11, 12, 13, and 14 are optical input/output ports, which are connected to the optical transmission line 1 or 2 with an optical connector or the like.

Input/output ports 11, 12 and E/O converter 1
6. The O/E converter 17 is connected to the four-terminal optical branch/coupler 15 to form an optical transmitter/receiver pair 23. Also,
The input/output ports 13 and 14 are connected to an E/O converter 18 and an O/E converter 19, and an optical transceiver pair 24 is formed by an electric circuit including an OR circuit 20. Next, the optical transceiver pairs 23 and 24 are controlled by a communication processing circuit 21 and connected to various sensors and terminal devices (not shown) via an interface circuit 22.

The optical transceiver pair 23 branches the optical signal OS1 input from the input/output port 11 into two signals by the optical coupler 15, outputs one signal OS2 from the port 12, and outputs the other signal OS3. Output to O/E converter 17. In addition, the electric signal ES1 output from the communication processing circuit 21
is supplied to the E/O converter 16, and the E/O converter 16
After being converted into an optical signal by , it is supplied as an optical signal OS4. The optical signal OS4 is output from the input/output port 12 via the optical coupler 15.

The optical transceiver pair 24 receives the optical signal OS5 input from the input/output port 14 through the O/E converter 19. The O/E converter 19 converts the optical signal OS5 into an electrical signal ES.
2, and the electrical signal ES2 is sent to the communication processing circuit 21 and O
They are output to the R circuit 20, respectively. The OR circuit 20 is O/
The electric signal ES2 supplied from the E converter 19 and the electric signal ES1 supplied from the communication processing circuit 21 are logically summed, and this result is used as an electric signal ES3 to be sent to the E/O converter 18.
Output to. The electrical signal ES3 is converted into an optical signal OS6 by the E/O converter 18, and then outputted via the input/output port 13.

The above-described master node 9 and each slave node 10A, 10B, 10C and 10D each have a pair of slave node transceivers 23 and 24 in one optical transmission line 1 or 2, as shown in FIG. connected so that they are arranged alternately. In FIG. 1, to explain the flow of optical signals from master node 9 to slave node 10C, master node 9 uses E/O converters 3 and 5 to transmit the same signal to transmission lines 1 and 2 in opposite directions. Send at the same time. That is, the optical signal transmitted through the transmission line 1 is input from the port 11 of the slave node 10C via the optical transceiver pair 23 of the slave node 10A and the optical transceiver pair 24 of the slave node 10B, and is inputted from the port 11 of the slave node 10C. It is received by the E converter 17. Further, the optical signal transmitted through the transmission path 2 is input from the port 14 of the slave node 10C via the optical transceiver pair 23 of the slave node 10D, and is received by the O/E converter 19.

Next, to explain the flow of the optical signal from the slave node 10C to the master node 9, the slave node 10C uses the E/O converters 16 and 18 to
, 2 simultaneously transmit the same signal in opposite directions. That is, the optical signal transmitted through the transmission line 1 is received by the O/E converter 4 of the master node 9 via the transceiver pair 24 of the slave node 10D. Further, the optical signal transmitted through the transmission path 2 is transmitted between the transceiver pair 23 of the slave node 10B and the transceiver pair 2 of the slave node 10A.
4 and is received by the O/E converter 6 of the master node 9.

Next, the operation of this embodiment will be explained. (1) Normal operation In the above configuration, the signal flow between the master node 9 and the slave node 10C has been explained, but the signal flow between the master node 9 and the slave nodes 10A and 10B is also the same, and each slave node A signal transmitted from master node 9 is received through transmission paths 1 and 2. The communication processing circuit 21 determines whether the two received signals are correct or not by a method such as a parity check or a CRC check.

Next, the communication processing circuit 21 receives the received 2
If both signals are normal, one of the signals (for example, the main signal is the signal received from transmission line 1) is adopted as a normal signal and is supplied to the interface circuit 22. The adopted signals are then transmitted to various terminal devices and various sensors by the interface circuit 22.

Furthermore, the master node 9 receives signals transmitted from each slave node through the transmission lines 1 and 2. The two received signals are sent to the communication processing circuit 7 to determine whether the signals are correct or not by a method such as a parity check or a CRC check. Next, if both of the received signals are normal, the communication processing circuit 7 adopts one of the signals (for example, the main signal is the signal received from the transmission path 1) as the normal signal. Supplied to the interface circuit 8. The adopted signal is then transmitted by the interface circuit 8 to a higher-level transmission device or computer.

(2) Operation in case of disconnection FIG. 3 shows the communication method between master node 9 and slave node 10C when both transmission lines 1 and 2 are disconnected at point 40 (between slave nodes 10B and 10C). be. In the situation shown in FIG.
The optical signal transmitted from the O converter 3 through the transmission line 1 is
Although blocked by the disconnection at point 40, the optical signal transmitted from E/O converter 5 through transmission line 2 is transmitted to optical transceiver pair 2.
Received by 4.

On the other hand, the optical signal transmitted from the optical transmitter/receiver pair 24 of the slave node 10C through the transmission line 2 is transmitted at point 4.
However, the optical signal transmitted from the optical transceiver pair 23 through the transmission line 1 is blocked by the disconnection of the master node 9.
is received by the O/E converter 4 of. That is, point 4
0, even if the wire is disconnected, the function of transmitting and receiving signals between the master node 9 and slave node 10C is maintained. Similarly, mutual transmission and reception functions between the master node 9 and each slave node are also maintained. The above applies even if the disconnection occurs in other sections.

(3) Operation at the time of node failure Figure 4 shows the master node 9 and slave node 10 when the slave node 10B's transmitting and receiving functions stop working due to a power cut, etc.
This shows a method of communicating with C. In the situation shown in FIG. 4, from the E/O converter 3 of the master node 9 to the transmission line 1
The optical signal transmitted through the E/O converter 5 is blocked by the transceiver pair 24 of the slave node 10B.
The optical signal transmitted from the slave node 10C through the transmission line 2 is received by the transceiver pair 24 of the slave node 10C.

On the other hand, the optical signal transmitted from the transceiver pair 24 of the slave node 10C passes through the transceiver pair 23 of the slave node 10B and is received by the O/E converter 6 of the master node 9. Further, the optical signal transmitted from the transceiver pair 23 of the slave node 10C through the transmission path 2 is received by the transceiver pair 4 of the master node 9. That is, even if the slave node 10B goes down, the function of transmitting and receiving signals between the master node 9 and the slave node 10C is maintained. Similarly, master node 9
Mutual transmission and reception functions are also maintained between the slave nodes 10A and 10D. The above is the slave node 10A,
The same applies when any one of 10D goes down.

[0023]

[Effects of the Invention] As explained above, according to the present invention, the signals transmitted by the first node are transmitted in two directions in opposite directions.
When sequentially supplying to multiple second nodes through two independent optical transmission lines, one
Since relay amplification is performed by the first pair of optical transceivers at every other stage and selective bypass is performed by the optical branching means of the second pair of optical transmitters and receivers at every other stage, the following effects can be obtained. (1) There is no limit to the number of slave nodes that can be connected on a transmission path, and long-distance transmission can be achieved. (2) Since each node does not need to use an optical link with a large difference in optical signal transmission and reception levels (dynamic range), the transmission speed can be increased.

(3) The communication control system is simple, compact, and cost-reduced, and can also have a failure avoidance function. (4) Since each slave node can be manufactured with the same specifications, system construction is efficient.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention.

[Figure 2] Slave nodes 10 (10A, 10B, 10C)
, 10D).

FIG. 3 is a diagram illustrating the flow of optical signals when a disconnection occurs.

FIG. 4 is a diagram for explaining the flow of optical signals when a node abnormality occurs.

[Explanation of symbols]

1, 2 optical transmission line 3, 5, 16, 18 E/O (electrical/optical) converter 4,
6, 17, 19 O/E (optical/electrical) converter 7, 21
Communication processing circuit 8, 22 Interface circuit 9 Master node (first node) 10A, 10B
, 10C, 10D Slave node (second node) 11, 12, 13, 14 Optical input/output port 15 Four-terminal optical fiber coupler (optical branching means) 20 OR circuit 23, 24 Optical transceiver pair (first or first 2 optical transceiver pairs)

Claims (1)

[Claims] Claim 1: A duplex optical transmission line made of two loop-shaped optical fibers, and a transmission/reception function for two optical signals, wherein each of the two optical transmission lines transmits the same signal in the opposite direction. a first node that always receives the optical signals of the two systems independently, and a first node that constantly receives the optical signals supplied through either one of the two optical transmission lines and relays and amplifies the optical signals. Later, a first optical transceiver pair that selectively outputs to the optical transmission line of the same system, and an optical branching means that branches the optical signal supplied through the other of the two optical transmission lines into two. and a second optical transmission receiver pair which always receives one of the optical signals branched by the optical branching means and outputs the other to an optical transmission line of the same system, and is inserted into the optical transmission line. a plurality of second nodes, and the first and second optical transceiver pairs in the plurality of second nodes are arranged alternately in each of the two optical transmission lines. A double-loop optical transmission system characterized in that the system is connected to