JPS58215622A - Optical bus branching and inserting circuit - Google Patents

Abstract

PURPOSE:To obtain an optical bus branching and inserting circuit for plural parallel optical loops by coupling other-side input/output terminals of N units of optical directional couplers with N units of input/output optical waveguides, and performing timedivision control over the optical directional couplers. CONSTITUTION:Four optical directional couplers are formed on an optical IC substrate and one-side input/output optical paths of the couplers are coupled. One optical coupler, e.g. the 2nd coupler is applied with voltages between electrodes A2 and B3, and A'2 and B'2, and then the branching and insertion of a optical signal with and from the 2nd optical path I2-O2 are carried out. Then, when the voltages V applied to the optical coupling part electrodes are varied on time-division basis to obtain the functions of a time-divided multiplex optical switch element, permitting the optical branching and inserting circuit to perform time-division multiplex operation. Thus, the optical bus branching and inserting circuit for plural parallel optical loop systems is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of the Invention The present invention relates to an optical bus communication system, and more particularly to an optical bus add/drop circuit for accessing an optical bus.

(2) Prior Art and Problems It can be said that optical communication systems have now fully entered the commercialization phase against the backdrop of significant advances in light sources, photodetectors, optical fibers, and other related technologies. Furthermore, the application of this technology is being expanded not only to long-distance interoffice transmission systems but also to in-plant optical loop networks. The current in-house optical loop network mainly accommodates data terminals, computer terminals, etc., and if one optical loop is installed, it has sufficient transmission capacity (aside from backup for failures). . However, in the future, it is thought that there will be a growing demand for multiplexing voice communications, ultra-high-speed data communications, image communications, etc. onto the optical loop networks that mainly handle data, as described above.
The required transmission capacity is expected to increase rapidly, and the demand for installing multiple optical loop transmission lines will also increase.

On the other hand, conventionally, in multiple nodes on an optical loop transmission path, 0/E (optical/electrical) conversion is performed within the hind node that brings the optical loop of the adjacent node into its own node, and once it is converted back to an electrical signal, the After branching or adding the necessary signals at the node, a method is adopted in which the Elo (electrical/optical) conversion is performed again and the optical signal is sent to the optical loop to the next node. That is, active elements are required to add and drop signals in the form of electrical signals at each node, and to perform 0/E and E10 conversion, and the failure rate of the node is high, and the failure can affect the entire loop. This had the disadvantage of causing a communication breakdown.

(3) Purpose of the Invention The purpose of the present invention is to realize a drop-and-drop method in a multiple parallel optical loop system, and to provide an optical bus insertion and drop-in system in which a failure of a specific node does not affect the entire optical loop transmission system. The purpose is to provide circuits.

(4) Summary of the invention According to the present invention, KN optical directional couplers are formed on a light-year integrated circuit board, and the output of the first (I=1 to N-1) optical directional coupler is One of the inputs of the (i+1)th optical directional coupler, one of the inputs of the first optical directional coupler is connected to the optical insertion waveguide, and one of the outputs of the Nth optical directional coupler is connected to one of the inputs of the (i+1)th optical directional coupler. The other inputs and outputs of the N optical directional couplers are coupled to the optical branching waveguides, and the other inputs and outputs of the N optical directional couplers are connected to the N input optical waveguides, N
By having an optical circuit configuration coupled to a main output optical waveguide and controlling the time-division period of the optical directional coupler, a time-division optical bus drop/add circuit that achieves the above-mentioned object can be obtained.

(5) Examples of the invention Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram showing the principle of an optical directional coupler necessary for detailed explanation of the present invention. Conventionally, two three-dimensional optical waveguides PR and Q8 formed on an optical IC board have a thickness of several μm as shown in the figure.
It is known that when two optical waveguides are brought close to each other, a light distribution coupling phenomenon occurs in which light propagating in one optical waveguide migrates into the other optical waveguide as it progresses. Furthermore, such a close optical waveguide is formed on a material substrate such as LiNbO3, and as shown in FIG.
It is known that the mutual coupling between two waveguides can be controlled by forming waveguides B, A', and B' and applying or not applying a voltage thereto. That is, P in the figure.

For example, when no voltage is applied to the light incident from Q, each S
, R, and when a voltage is applied, they can be emitted from JS. This is an embodiment of the invention. In the example shown in FIG. 2, four optical directional couplers as explained in FIG. 1 are formed on an optical IC board,
In addition, one of the input and output optical paths of each optical directional coupler is coupled to each other as shown in the figure.

As a result, when no voltage is applied to any of the four optical directional couplers, the four input optical waveguides II, 1 shown in the figure
2. The light incident from IS, 14 is transmitted to four output optical waveguides 01, 02 . When it is emitted from Og and 04, it becomes K.

Then any one of the four optical directional couplers, for example the electrodes A2, B2 and A of the second optical directional coupler.
'2. Assume that a voltage is applied to B'2 as shown in FIG. In this case, the light that entered through the input optical waveguides 11.1B and 14 exits from the output waveguides 01, 03, and 04, respectively, but the light that entered from ■2 does not exit to 02 and leaves the coupling part of the waveguide as it is. Go straight to the optical branching waveguide D shown in the figure.
Emit from B and P. On the other hand, at this time, when an optical signal is input from the optical insertion waveguide INS shown in the figure, this optical signal reaches the second optical directional coupling part and then goes straight through the coupling part,
As a result, the light is emitted from the output optical waveguide 02. In other words, the optical signal has been branched and added to the second optical path I2-02.

FIG. 3 is an example of an optical loop transmission system using this. As shown in the figure, N optical paths are connected in a loop,
This is an example in which m communication nodes are accommodated. Since each communication node communicates with other communication nodes via a dazzling loop, it accesses any one of the N optical paths, branches and takes out the optical signal from the other node, and at the same time sends it to the other node. Insert the optical signal. In the figure, INS indicates an optical signal insertion waveguide to the optical bus at each node, DRP indicates an optical signal branching waveguide from the optical bus, and each communication node has the same configuration as shown in the embodiment of FIG. 2. (except that the number of buses has been generalized from 4 to N).

As can be seen from the above 49, according to the present invention, each communication node is composed of an optical directional coupler, that is, a passive element as shown in FIG. Although it is not shown in the diagram of each node, there is a failure in the power supply section that supplies the optical drop/add waveguide DRP and other circuits (mostly electronic circuits and power lines) that interface with the INS. It can be seen that the optical bus system will not be disrupted even if

In the configuration shown in FIG. 1, if the voltage V applied to the optical coupler electrode is changed periodically in a time-division manner, the optical directional coupler becomes a time-division multiplex optical switch element. Therefore, it is also possible to cause the optical branching and adding circuit shown in FIG. 2 to perform time division multiplexing operations. As a result, each of the N optical buses in FIG.・・・
...11k, the voltage applied to the optical directional coupler group is applied to the time slot T1...11k. T2.・・・・・・Tk
If it were possible to change the optical signal for each time slot, each communication node could drop an optical signal related to an arbitrary time slot of an arbitrary bus, and conversely insert it into the optical signal.

(6) Effects of the Invention As described above, the present invention has the advantage that a highly reliable optical signal drop/add circuit for a plurality of parallel optical buses can be effectively formed on a single optical IC board.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of an optical directional coupler, Fig. 2 is a diagram showing an optical bus drop/add circuit according to an embodiment of the present invention, and Fig. 3 is an optical loop transmission applying the present invention. FIG. 1 is a diagram showing an example of a system. Third flash

Claims (1)

[Claims] N optical directional couplers are formed on an optical integrated circuit board, and i
One of the outputs of the (i=1 to N-1) optical directional coupler is connected to one of the inputs of the (Ci+1)-th optical directional coupler, and one of the inputs of the first optical directional coupler is to the optical branching waveguide, one of the outputs of the N-th optical directional coupler to the optical branching waveguide 2, and the other inputs and outputs of the N optical directional couplers to each of the N inputs. 1-1. A time-division optical bus drop/add circuit comprising an optical circuit configuration coupled to an optical waveguide and N output optical waveguides, and controlling the optical directional coupler in a time-division period.