JPH0314249B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Field of Application of the Invention>> The present invention relates to an improvement in an optical dataway that performs communication between a plurality of stations via optical fibers.

<<Prior Art>> FIG. 1 is an explanatory diagram showing the configuration and operation of a conventional multi-drop optical data way using optical couplers. Although only one direction is shown in the figure, it is actually used bidirectionally. Node ND11
~ND16 is linked with the optical transmission line L1 and exchanges signals with each other. Repeater RP to compensate for signal attenuation due to increase in number of nodes and distance
is inserted into the optical transmission line L1. Figure 2 shows the configuration of each node ND1i (i = 1, 2,...), and the station ST1i is connected to the optical coupler A1i.
The optical transmission line L1 is formed through the optical transmission line L1. In FIG. 1, signals S11 and S12 sent out by stations ST11 and ST12 are both regenerated and relayed by a repeater RP to recover the signal level and then transmitted again to stations ST14, ST15, ST16, etc.

In an optical dataway with such a configuration, the coupler in each station is composed of passive elements, resulting in high reliability and low transmission delay and low error rate. It has the disadvantage of being less attractive.

<<Object of the Invention>> The present invention has been made to solve the above-mentioned problems, and its purpose is to realize an optical dataway with high reliability, low transmission delay, and low error rate.

<<Summary of the invention>> The optical dataway according to the present invention includes an optical transmission line,
In an optical dataway that includes an optical coupler connected to this optical transmission line and a station connected to this optical coupler, electrical control from the station is performed for communication between multiple stations via the optical transmission line. an optical coupler whose coupling ratio of optical signals between the optical transmission line and the station is variable depending on a signal; and an electrical control signal that sets the coupling ratio to 1 when the received optical signal level is below a certain value to the optical coupling ratio. A station for outputting and reproducing and relaying the output.

≪Example≫ The present invention will be explained in detail below using the drawings.

FIG. 3 is an explanatory diagram showing the configuration and operation of an embodiment of the optical dataway according to the present invention using a signal level diagram. Although only one direction is shown in the figure, it is actually used bidirectionally. L2 is an optical transmission line, ND21~ND2
6 is a node linked to this optical transmission line L2. Figure 4 shows each node ND2i (i=1, 2,...)
In this block diagram, A2i is an optical coupler with a variable coupling ratio connected to the optical transmission line L2;
ST2i is a station that is connected to this optical coupler A2i and changes the coupling ratio to an arbitrary value using its control signal Ci.

FIG. 5 is an explanatory diagram showing the input/output relationship of the optical coupler when the light transmittance of the optical coupler is α1. The following relational expression exists between the input optical signals I1, I2 and the output optical signals O1, O2.

O1 O2=1−α1 α1 α1 1−α1 I1 I2 In the optical dataway configured as above,
At the time of transmission, the value of the coupling ratio α1 of the node is set to 1 and the signal is sent out (FIG. 6A). At the time of reception, it is normally set to a predetermined value of 1 or less. (Fig. 6B), when the received signal level of the station falls below a certain value due to signal attenuation due to an increase in the number of nodes or distance, regenerative relay is performed with the coupling ratio α1 set to 1 (Fig. 6B).
Figure A).

The following description will be made based on the signal level diagram shown in FIG. 31 is the receivable signal level range at each station, and 32 is the reproduced signal level range. When the received signal level drops to the reproduced signal level range 32, the coupling ratio switches to 1.
Signal S21 sent from station ST21
reaches the reproduction signal level range at nodes ND23 and D25, and is reproduced and relayed to recover the signal level. Similarly, the signal S22 sent from the station ST22 reaches the reproduction signal level range at the node ND24, and is reproduced and relayed to recover the signal level. In other words, the location where the signal is reproduced and relayed varies depending on the station from which the signal is transmitted.

FIG. 7 is a configuration explanatory diagram showing one embodiment of the optical coupler A2i. The configuration of this optical coupler was disclosed in the patent application filed in 1983.
It is almost the same as the one shown in No. 146652, "High-speed optical switch," and utilizes the electro-optic effect of PLZT. In the figure, 71 and 72 are optical fibers that guide input optical signals I1 and I2, respectively, and 73 and 74
is an optical fiber connector that connects to these optical fibers 71 and 72. The part CP surrounded by double solid lines is an optical coupling part, and the inside thereof is maintained at a constant temperature of 50 to 100°C.
In the optical coupling part CP, 75 and 76 are lenses that condense the input light that enters through the optical fiber connectors 73 and 74, respectively, and 77 is a polarized light constructed by combining a beam splitter 771 and a total reflection prism 772. In the separator, here is lens 7
Input light enters through 5 and 76. 78 and 79 are PLZTs installed so that the two polarized waves emitted from 77 are irradiated, and 80 is this PLZT.
Dry terminal 81 is a polarization combiner configured by combining a beam splitter 811 and a total reflection prism 812, and the light that has passed through each PLZT 78 and 79 is incident here. . 82 and 83 are lenses, respectively.
It is set so that PLZT78 and 79 are in focus. 84 and 85 are optical fiber connectors, through which the output light from the polarization combiner 81 that has passed through lenses 82 and 83 passes, and output optical signals O1 and O.
2 to optical fibers 86 and 87.

The operation of the optical coupler configured in this way will be explained next. In the optical coupling section CP, the light that has passed through the lens 75 and entered the polarization separator 77 is separated into S waves and P waves.
into each. Here, the PLZTs 78 and 79 do not produce an electro-optical effect unless a control voltage is applied. Therefore, in this state, both the P wave that has passed through the PLZT 79 and the S wave that has passed through the PLZT 78 are output to the optical fiber 86 side through the lens 82 and the optical fiber connector 84.
When a control voltage is applied to the PLZTs 78 and 79, an electro-optical effect occurs, and the plane of polarization is rotated by 90 degrees, so that the P wave passing through the PLZTs becomes an S wave, and the S wave becomes a P wave. As a result, the light that passed through PLZT78 and became a P wave, and the light that passed through PLZT79 and became an S wave,
After entering the polarization combiner 81, the lens 83,
It passes through the optical fiber connector 85 and is output to the optical fiber 87 side. The same goes for the light that enters the polarization separator 77 through the lens 76.
If no control voltage is applied to the PLZTs 78 and 79, the output is output to the optical fiber 87, and if a control voltage is applied, the output is output to the optical fiber 86.

According to the device configured in this way, the optical input signals I1 and I2 are changed to the optical output O1 by the control voltage.
Or you can switch to O2. That is, when the control voltage is OV, the optical input I1 becomes the optical output O1, and the optical input I2 becomes the optical output O2. control voltage
As it increases from OV, the optical input I1
gradually shifts to the optical output O2, and the optical input I2 gradually shifts to the optical output O1. FIG. 8 is a characteristic curve diagram showing this situation, and also shows how the light transmittance α11 from I1 to O1 and the light transmittance α12 from I1 to O2 change depending on the control voltage. In this way, the light transmittance can be arbitrarily and continuously controlled by the control voltage.

In this manner, the optical dataway having the above configuration does not use repeaters and uses a passive optical coupler, making it possible to realize economic efficiency and high reliability.

Furthermore, since the coupling ratio during transmission and reception can be switched, loss between transmission and reception can also be reduced.

Furthermore, even if the optical power is attenuated at an unpredictable location due to a failure or accident, a nearby station will restore the optical signal level, making it much more effective than inserting a repeater at a fixed location.

In the above embodiment, a multi-drop type optical data way is shown, but a loop type optical data way can also be realized in the same manner.

Note that in the above example, PLZT is used in the optical coupler.
We used electro-optical elements such as, but are not limited to
A magneto-optical element such as YIG may also be used.

<<Effects of the Invention>> As described above, according to the present invention, it is possible to realize an optical dataway with high reliability, low transmission delay, low error rate, and small attenuation between transmission and reception. It is also economical.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration and operation of a conventional multi-drop optical data way using optical couplers, FIG. 2 is a block diagram showing the configuration of the node part in FIG. 1, and FIG. An explanatory diagram showing the configuration and operation of an embodiment of the related optical dataway using a signal level diagram, Part 4
The figure is a configuration block diagram showing the configuration of the node part in Figure 3, Figure 5 is an explanatory diagram showing the input/output relationship of the optical coupler, and Figure 6 is an explanatory diagram to explain the operation of the device in Figure 4. , FIG. 7 is a configuration explanatory diagram showing one embodiment of the optical coupler shown in FIG. 5, and FIG. 8 is a characteristic curve diagram showing the input/output characteristics of the optical coupler. 77... Polarization separator, 78, 79... Electro-optical element, 81... Polarization combiner, 771, 811...
Beam splitter, 772, 812... Total reflection prism, L2... Optical transmission line, A2i... Optical coupler, Ci... Control signal, α1... Coupling ratio, ST2i
...Station. (i=1, 2,...).

Claims (1)

[Claims] 1. A system comprising an optical transmission line, an optical coupler connected to the optical transmission line, and a station connected to the optical coupler, and capable of communicating between a plurality of stations via the optical transmission line. In the optical dataway, the coupling ratio of the optical signal between the optical transmission line and the station is variable according to an electrical control signal from the station, and the coupling ratio is set to 1 when the level of the received optical signal is below a certain value. and a station that outputs an electrical control signal to the optical coupler to perform regenerative repeating.