JPH02260836A - Optical bus - Google Patents

Abstract

PURPOSE:To simplify the extension or the removal of nodes in an optical bus by constituting a branch coupling rate between anode and an optical bus so as to be controlled and setting the branching coupling rate of a branching coupler with no node connecting thereto to be smaller than the branching coupling rate of the branching coupler with a node connecting thereto. CONSTITUTION:The branching coupling rate of branching couplers 8a-8d is changed by a control voltage applied to external control terminals 11a-11h and set to a prescribed value. Then a control voltage from the branch coupling rate control means sets the branching coupling rate between the node and the optical bus of the branching coupler 8b where nodes 13a-13c (13) are not connected so as to be smaller than that of branching couplers 8a, 8c, 8d where a node 13 is connected. Thus, the transmission loss of the branching coupler 8b where nodes 13a-13c (13) are not connected is very small. Thus, lots of the branching couplers 8a-8d are inserted in the optical bus and the node 13 is connected as necessary to simplify the extension and the removal of the node 13 in the optical bus.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is used in optical communication systems, and particularly relates to an optical bus that facilitates the addition and removal of nodes on the optical bus.

[Conventional technology]

FIG. 3 is a block diagram showing a conventional example, showing a bidirectional optical bus. In FIG. 3, 1a to IC are branching couplers (SC) with a fixed branching/coupling ratio for inserting and extracting optical signals into and from the optical bus, and 3g to 3J are branching couplers 1a to I.
The optical fibers 2a to 2C connecting the nodes 3 and 3
a to 3f are optical fibers that connect the optical bus composed of optical fibers 3g to 3 and the nodes 2a to 2C, and 7
a-7c, 76-7f, 7g-71 and 7J-71
are ports ■, ■, ■, and ■ of branch couplers 1a to IC.

The nodes 2a to 2C are optical transmitters (T) 4a to 2C.
4c, and optical receivers (R) 5a to 5c, which are branching couplers (SC) 6a to 6C with a branching and coupling ratio of 0.5.
and optical fibers 3g to 3g via optical fibers 3a to 3f.
It is connected to an optical bus consisting of 3J.

Next, the operation of this conventional optical bus will be explained.

When the nodes 2a to 2C receive signals flowing on the bus, the optical signals are taken out from the optical path by the branching couplers 1a to IC. For example, the inside of the optical fiber 3h is connected to the optical fiber 31.
A part of the optical signal traveling in the direction is branched by the branching coupler 1b, passes through the optical fiber 3e and the branching coupler 6b, and reaches the optical receiver 5b. The remaining optical signal passes through the branching coupler 1b and enters the optical fiber 31. In this way, an optical signal transmitted from one node is distributed to all nodes.

On the other hand, when transmitting an optical signal, for example, the optical transmitter 4
The optical signal output from the optical fiber 6b is split into two by the branching coupler 6b, and enters the optical fibers 3b and 3e.

Further, in the branching coupler 1b, the optical signals from the optical fibers 3b right and 3e are transmitted to the optical fibers 31 and 3e, respectively.
incident on h.

[Problem that the invention seeks to solve]

In addition to such a configuration, for example, when installing a new node between nodes 2a and 2b, the optical fiber 3h
It is necessary to disconnect the branch and install a new branch coupler. For this reason, there was a problem that not only was it difficult to add more nodes, but also that other nodes could not communicate during the installation work. Furthermore, when removing a node, it is necessary to remove the branch coupler in order to reduce the loss caused by the unnecessary branch coupler, which causes the same problem as when adding a node.

This kind of problem can be solved if a large number of branch couplers that exceed the number of nodes can be installed in advance, but
A branch coupler that does not connect nodes also has branch loss, so
This was difficult to implement because the number of branch couplers that could be installed was small.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical bus that solves the above-mentioned problems, allows a large number of branch couplers to be installed on the bus in advance, and facilitates the addition and removal of nodes on the optical bus.

[Means for solving problems]

The present invention provides an optical bus including an optical fiber and a branching coupler for branching and coupling signals between the optical fiber and a node, wherein the branching coupler is a branching coupler for branching and coupling signals between the node and the optical bus. The coupling rate is configured to be controllable, and the branch coupling rate between the optical bus and the node of the branch coupler to which no node is connected is controlled to be the branch coupling rate between the node of the branch coupler to which the node is connected and the optical bus. The present invention is characterized by comprising a branching/coupling rate control means for setting the branching/coupling rate to be smaller than the branching/coupling rate.

[Effect]

As a branch coupler, for example, L using the Pockels effect
Using an N optical switch, the branching/coupling ratio changes depending on the control voltage applied to the external control terminal, and can be set to a predetermined value. The control voltage from the branching/coupling rate control means is used to control the branching/coupling rate between the optical bus and the node of the branching/coupler to which no node is connected, and the optical bus to the node of the branching/coupling to which the node is connected. It is set to be smaller than the branching/coupling ratio with the bus, for example, 0.

Therefore, the transmission loss caused by a branch coupler to which no nodes are connected is extremely small, and many branch couplers can be inserted into the optical bus in advance and used by connecting nodes as needed. This makes it possible to easily add and remove nodes.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention, and shows a bidirectional optical bus. In FIG. 1, 8a to 8d are branching couplers (SC) whose branching and coupling ratios can be externally controlled;
la~llb are control terminals for the branching and coupling ratio, 108~1
0f is a control line for branching and coupling ratio, and 3g to 3 are branching and coupling ratio control lines.
Optical fiber connecting bus between a to 8d, 13a to 13
c is a node; 3a to 3f are optical fibers 9a to 9d that connect the optical buses constituted by optical fibers 3g to 3 and the nodes 13a to 13c;

9e to 9h, 9i to 91 and 9m to 9p are ports ①, ②, ② and ② of branch couplers 8a to 8d.

On the right side of the branching couplers 8a to 8d, if the branching/coupling rate from the optical bus to the node, that is, the branching/coupling rate from port ■ to ■ and from port ■ to ■, is α, then the branching from port ■ to ■ and from port ■ to ■ The coupling rate is 1-α.

The nodes 13a-13C have transmitters (T) 4a-4c and receivers (R) 5a-5C, which are branch-couplers (SC) 6a-6c with a branch-coupling ratio of 0.5.

It is connected to an optical bus composed of optical fibers 3g to 3 via optical fibers 3a to 3f. Furthermore, node 13
a-13C has control power supplies 12a to 12C, and control power supplies 12a to 12C are connected to control terminals 1 of branch couplers 8a, 8c, and 8d by control lines 10a to 10f, respectively.
1a s lie % llc , l1g ,, l
Connected to id and llh.

FIG. 2 shows an example of the characteristics of the branch couplers 8a to 9d. When the applied voltage vr is applied to the control terminals 11a-lie, the port ■
The branch-coupling ratio from ■ and from ■ becomes α0, and when the applied voltage is set to 0, the branch-coupling ratio from port ■ to ■ and from ■ to ■ becomes 0, and the branch-coupling ratio from port ■ to ■ and from port ■ to ■ becomes 1. becomes. As an example of a branching coupler having such characteristics, an LN optical switch using the Pockels effect is known (Reference: 1988 Institute of Electronics, Information and Communication Engineers, Semiconductor and Materials Division National Conference 353).

The feature of the present invention is that in FIG.
Branch couplers 8a to 8d made of, for example, LN optical switches, whose branching/coupling ratio between the node and the optical fiber can be controlled by a control voltage applied to lb, and control lines 10a to 10a as branching/coupling ratio control means. 10f and control power supply 12
The reason is that a to 12C are provided.

Next, the operation of this embodiment will be explained.

The transmission and reception operations of this embodiment are the same as those of the conventional example shown in FIG.

When installing a node, assuming that an unused branch coupler, for example, a branch coupler 8a, is not used, the branch coupler 8a and the node 13a are connected to the optical fibers 3a and 3d and the control line 10a and Connect with 10d. Then, the control power supply 1 is connected between the control terminals 11a and 116 of the branch coupler 8a via the control lines 10a and 10d.
α of the optical signal to which the control voltage vr from 2a is applied and passes through the optical buses 3g and 3h. minute is branched to node 13a,
Optical buses 3g and 3h are coupled to node 13a.

Here, α. is the branching/coupling ratio between the node and the optical bus that maximizes the number of branching/coupling devices installed on the optical bus, and it is assumed that the optical attenuation due to the optical fiber and the excess loss of the branching/coupling devices are 0, and the maximum allowable loss between nodes is LCdB] is a value that satisfies the following formula (1). For example, if L is 15, then α.

is approximately 0.39.

On the other hand, when removing a node, the control line and optical fiber are disconnected from the branch coupler. Then, the voltage at the branch-coupler control terminal becomes 0, and the optical signal passing through the optical bus is not branched to ports (2) and (2), eliminating loss.

In this way, the voltage at the control terminal of the unused branch coupler is set to 0.
By doing so, the loss due to unused branch couplers can be suppressed to a small level, and a large number of branch couplers can be installed in advance. Therefore, according to the present invention, a node can be installed and removed simply by attaching and removing an optical fiber and a control line, so that it is easy to install and remove a node, and it is possible to easily install and remove a node. No impact.

In this example, a method of controlling the branching/coupling ratio from a node using an LN optical switch as a branching/coupling device with a variable branching/coupling ratio was shown. The present invention can be applied to any device whose branching and coupling rate can be controlled from the outside, such as the 1986 Institute of Electronics, Information and Communication Engineers Semiconductor/Materials Division National Conference 370).

Also, similar effects can be obtained by using other control methods. For example, the same effect can be obtained by setting the branching and coupling ratio by installing a switch in the branching coupler to change the branching and coupling ratio and manually switching this switch when installing and removing nodes.

Although the embodiment of FIG. 1 describes a bidirectional optical bus that transmits light in both directions, other configurations such as a double unidirectional bus that transmits light in one direction, a folded bus, and a double folded bus may be used. A similar effect can be obtained by applying the present invention to an optical bus.

〔Effect of the invention〕

As explained above, the present invention improves the branch coupling rate between the optical bus and the node of the branch coupler that is not connected to the node, and the branch coupling rate between the node and the optical bus of the branch coupler that is connected to the node. By making the branching/coupling ratio smaller than , it is possible to install a large number of branching/coupling devices on the optical bus in advance, which has the effect of simplifying the addition and removal of nodes on the optical bus.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. Figure 2 is a characteristic diagram of the branch coupler. FIG. 3 is a block diagram showing a conventional example. la ~ lc, 5a ~ 6c, 8a ~ 8d
... Branch coupler (SC), 2a to 2c, 13
a to 13c... Node, 3a to 3k... Optical fiber, 4a to 4C... Transmitter (T), 5a to 5C...
・Receiver (R), 7a to 71.9a to 9p-... Port, 10a to 10f-... Control line, lla to 11h.
...Control terminal, 128~12C...Control power supply. Control XI ÷ Voltage actual circuit example (circuit connection base existence) Fan 2 times

Claims (1)

[Claims] 1. An optical bus comprising an optical fiber and a branching coupler that branches and couples signals between the optical fiber and a node, wherein the branching coupler connects the node and the optical bus. The branching/coupling rate between the optical bus and the node of the branching coupler to which the node is not connected is controlled, and the branching/coupling rate between the node of the branching coupler and the optical bus to which the node is connected is configured to be controllable. What is claimed is: 1. An optical bus characterized by comprising a branching/coupling rate control means for setting the branching/coupling rate to be smaller than the branching/coupling rate between the optical bus and the optical bus.