JP2577469B2 - Control method of optical star network - Google Patents

Description

The present invention relates to a method for controlling an optical star network using an optical star coupler as a transmission path.

(Prior Art) FIG. 4 shows an example of an optical star network using an optical star coupler for combining / distributing optical signals.

In the optical star coupler OC, n input optical fibers IF1 to IFn each having one end connected to the input port, and n output optical fibers OF1 to O having one end connected to the output port.
A mixer unit MX is configured to combine / distribute optical signals by fusing the other end of Fn.

The transmission optical signals from the plurality of stations ST1 to STn are output from the respective optical transmission circuits OT1 to OTn, and are applied to the input ports of the star coupler OC via the transmission optical fibers TF1 to TFn. The optical signals output from the output ports are input to the optical receiving circuits OR1 to ORn of the stations ST1 to STn via the receiving optical fibers RF1 to RFn.

The connectors CT1 to CTn are connected to the transmission optical fibers TF1 to TFn.
Are connected to the optical transmission circuits OT1 to OTn.
CI1 to CIn are optical star couplers for transmitting optical fibers TF1 to TFn.
Connects to the input port of OC, and connectors CO1-C
On is for connecting the receiving optical fibers RF1 to RFn to the output port of the optical star coupler CO, and the connectors CR1 to C
Rn is for connecting the receiving optical fibers RF1 to RFn to the optical receiving circuits OR1 to ORn.

For example, a transmission optical signal output from the optical transmission circuit OT1 of the station ST1 is input to the optical star coupler OC via the transmission optical fiber TF1, and is input to the mixer unit MX via the input optical fiber IF1.

Then, the mixer unit MX outputs n output optical fibers OF1 to OFn.
Are distributed evenly, output from the output port, and receive the respective stations ST through the receiving optical fibers RF1 to RFn.
The signals are input to the optical receiving circuits OR1 to ORn of 1 to STn.

In this way, signals transmitted from one station are simultaneously received by all stations in the network, and an optical network having the characteristics of a bus-type network can be formed.

The bus-type network is characterized in that when each station fails in the inoperative direction, it does not affect the communication of other stations in the network, and has a great advantage particularly when applied to the control field.

(Problems to be Solved by the Invention) However, such an optical star network has the following disadvantages.

That is, as shown in FIG. 5, for example, when three stations ST1, ST2, and ST3 are connected to the optical star network, the transmission optical signal output from the optical transmission circuit OT1 of the station ST1 is transmitted to each station ST1. , ST2,
Considering the path up to reception at the optical receiving circuits OR1, OR2, and OR3 of ST3, input to the optical star coupler OC via the connector OT1, the transmission optical fiber TF1, and the connector CI1, and the mixer via the input optical fiber IF1. Up to the point where the information is input to the unit MX, the process is the same for each route.

After that, on the path received by the optical receiving circuit OR1 of the station ST1, the output optical fiber OF1, the connector CO1,
The signal is input to the optical receiving circuit OR1 via the receiving optical fiber RF1 and the connector CR1.

In the path received by the optical receiving circuit OR2 of the station ST2, the light is input to the optical receiving circuit OR2 via the output optical fiber OF2, the connector CO2, the receiving optical fiber RF2, and the connector CR2.

In the path received by the optical receiving circuit OR3 of the station ST3, the light is input to the optical receiving circuit OR3 via the output optical fiber OF3, the connector CO3, the receiving optical fiber RF3, and the connector CR3.

Now, since the components of these paths are different from each other, the loss value associated with the optical transmission of each path is also different.

Here, the stations ST1, ST2, ST3
When the loss values in the receiving path up to La and Lb and Lc are respectively set, when the conditions of La ≧ Lb and La ≧ Lc are satisfied,
When the level of the optical signal output from the station ST1 decreases, the first signal that can be received is the station ST1.
No problem to be yourself.

However, when the condition of La ≦ Lb or La ≦ Lc is satisfied, when the level of the optical signal output from the station ST1 decreases, the first reception abnormality occurs in the station ST2 or the station ST3. In this case, an abnormality appears in a station other than the station ST1 in which the malfunction originally occurs.

When such a situation occurs, the station ST1 is inconvenient if the functions of the entire optical star network do not operate properly in order to continue transmitting the transmission signal despite the fact that there is a station having a reception error. Is generated.

The present invention has been made in view of such circumstances,
It is an object of the present invention to provide a control method for an optical star network, which can remove as much as possible the effect of a decrease in the level of an optical signal output from a station.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a receiving level of a signal transmitted from the terminal itself.
A level abnormality judging means for judging with an abnormality judgment level larger than a reception level judgment level of a signal transmitted from another terminal is provided, and when a level abnormality is judged by the level abnormality judging means, transmission of a transmission signal is prohibited. It is like that.

(Operation) Therefore, a terminal in which the output level of the transmission optical signal is lowered can detect an abnormality in the output level of its own terminal before other terminals, so that the operation of the entire optical star network is hindered. Can be avoided in advance.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an optical signal transmitting / receiving circuit according to an embodiment of the present invention. The optical signal transmitting and receiving circuit constitutes, for example, an optical transmitting circuit and an optical receiving circuit of each station of the optical star network shown in FIG.

In FIG. 1, a modulated transmission signal SD output from a station is transmitted to a light emitting diode 2 via a driver 1.
And to the transmission carrier detection circuit 3.

The light emitting diode 2 converts a transmission signal input via the driver 1 into a corresponding optical signal SL. The optical signal SL forms an optical star network via a connector and a transmission optical fiber (not shown). Is input to an optical star coupler (not shown).

The transmission carrier detection circuit 3 smoothes a clock component included in the transmission signal SD, and outputs a detection signal SI at a logical H level while the transmission signal SD is being output. It is applied to a negative logic preset input terminal P of the D flip-flop 4.

The photodiode 5 receives the optical signal RL output from the optical star coupler and outputs a corresponding electric signal. The signal is transmitted via the amplifier 6 to the comparator 7 and the comparator 8 as a reception signal SR. Is added to the + input terminal.

The comparator 7 is for detecting that the level of the reception signal SR obtained when the transmission signal SL output from the own terminal is received is higher than a certain value,
A reference value VT1 for defining transmission sensitivity is added to the minus input terminal, and the output signal is output to the reception carrier detection circuit 9.

The comparator 8 is for detecting that the level of the received signal SR is equal to or higher than a predetermined value, and defines a minimum receiving level having a value smaller than the reference value VT1 at its negative input terminal. A reference value VT2 for performing the
0 and one input terminal of the AND circuit 11 are output.

The reception carrier detection circuit 9 smoothes the clock component included in the output signal of the comparator 7 and outputs a detection signal S2 of a logic H level while the reception signal SR is being received. Is applied to the clock input terminal of the D flip-flop 4.

The reception carrier detection circuit 10 smoothes a clock component included in the output signal of the comparator 8 and outputs a logic H level detection signal S3 while the reception signal SR is being received. Is applied to the clear input terminal CL of the negative logic of the D flip-flop 4.

D flip-flop 4 has data "1" applied to its data input terminal D and changes its state to a logical H level when preset input terminal P is at a logical L level and at the rising edge of a signal at a clock input terminal. When the clear input terminal CL goes to a logic low level, that state goes to a logic low level. The output terminal Q of this D flip-flop 4
The output signal S4 is applied to the other input terminal of the AND circuit 11.

In the above configuration, when no transmission signal is output from any station to the optical star network to which the station connected to this optical transmission / reception circuit belongs, the reception signal SR cannot be obtained. And the output signal of comparator 8 attains a logic L level.

As a result, at this time, since the detection signal S3 of the reception carrier detection circuit 10 is at the logic L level, the clear input terminal CL of the D flip-flop 4 is enabled, and the state of the D flip-flop 4 becomes the logic L level. Becomes

As a result, when the received signal SR cannot be obtained, D
The output signal S4 of the output terminal Q of the flip-flop 4 goes to the logical L level, the AND circuit 11 becomes inoperable, and the receiving signal RD is not output from the AND circuit 11.

From this state, when a signal is output from another station connected to the optical star network, and when the received signal SR obtained by receiving the signal is larger than the reference value VT2 added to the comparator 8, , Received signal S
A signal of a level obtained by subtracting the level of the reference value VT2 from the level of R is output from the comparator 8.

As a result, the detection signal S3 of the received carrier detection signal 10 goes to the logic H level, so that the clear input terminal CL of the D flip-flop 4 is disabled.

On the other hand, at this time, since the detection signal S1 from the transmission carrier detection circuit 3 is at the logical L level, the preset input terminal P of the D flip-flop 4 is enabled.

As a result, the state of the D flip-flop 4 becomes the logic H level, and the output signal S4 of the output terminal Q becomes the logic H level, so that the AND circuit 11 becomes operable. As a result, the output signal from the comparator 8 becomes , And is output to the station as a reception signal SD via the AND circuit 11.

In this way, when a signal output from another station is received and the reception level is higher than the reference value VT2, the reception signal SD
And output to the station.

When transmitting a signal from the own station, when a transmission signal SD is input, an optical signal SL corresponding to the transmission signal SD is output to the optical star network, and the detection signal S1 ( 2 (a) goes to a logic H level, whereby the preset input terminal P of the D flip-flop 4 is disabled.

At this time, since the reception signal has not been obtained, the detection signal S3 of the reception carrier detection circuit 10 is at the logical L level (see FIG. 2 (c)), whereby the output signal of the D flip-flop 4 is obtained. S4 (see FIG. 2 (e)) is logic L
Level, and the AND circuit 11 is in an inoperative state.

Then, when the optical signal SL is received via the optical star network, a received signal SR is thereby obtained.

At this time, when the level of the optical signal SL is sufficient and the reception level becomes higher than the reference value VT1 (see FIG. 2B), the detection signal S2 of the reception carrier detection circuit 9 rises to the logic H level. (See FIG. 2 (d)).

As a result, the clock input terminal of the D flip-flop 4 rises to the logic H level, so that the state of the D flip-flop 4 changes to the logic H level, and the output signal S4 rises to the logic H level.

As a result, the AND circuit 11 becomes operable, and the output signal from the comparator 8 passes through the AND circuit 11,
It is output to the own station as a reception signal SD.

On the other hand, when the attenuation of the optical signal SL is large and the reception level is smaller than the reference value VT1 (see FIG. 3B),
The detection signal S2 of the reception carrier detection circuit 9 does not rise to the logic H level (see FIG. 3D).

As a result, the state of the clock input terminal of the D flip-flop 4 does not change, so that the D flip-flop 4 holds the logic L level and the output signal S4 thereof holds the logic L level (see FIG. 3E). ).

As a result, since the AND circuit 11 continues to be in an inoperable state, the AND circuit 11 does not output the reception signal SD.

In this way, when the optical signal SL is transmitted from the own station and the level is sufficient, the received signal SD is transmitted.
On the other hand, if the level of the optical signal SL is not sufficient, the received signal SD cannot be obtained.

Therefore, when the reception signal SD cannot be obtained, the level of the optical signal SL starts to decrease, and it can be determined that the transmission operation of the own station is changing in the immobile direction.

Thereby, when it is determined that the transmission operation of the own station is changing in the non-operation direction, for example, the output of the optical signal SL is stopped at that time, and the own station is disconnected from the optical star network, and Is displayed and notified to an operator or the like.

In this manner, in the present embodiment, it is possible to detect in advance that the state of the own station has changed to a non-operational direction, so that the transmission signal from the own station has become unstable. Can be prevented from occurring, and the optical star network can be appropriately operated.

This embodiment is particularly suitable for an apparatus in which the optical transmission / reception unit and the transmission control unit are separated.

By the way, in the embodiment described above, the level of the transmission signal and the level of the reception signal are monitored by using two comparators. The two monitoring operations can be realized by one comparator by using the values even when the values are switched.

In that case, for example, when the output of the transmission carrier detection circuit is obtained, a reference value for monitoring the level of the transmission signal is used, and otherwise, the reference value for monitoring the level of the reception signal is used. can do.

[Effects of the Invention] As described above, according to the present invention, the reception level of a signal transmitted from the own terminal is determined based on the abnormality determination level larger than the determination level of the reception level of a signal transmitted from another terminal. The terminal whose output level of the transmission optical signal has decreased because it has detected the level abnormality of the transmission signal can detect the output level abnormality of its own terminal before other terminals, and as a result, the entire optical star network can be detected. This has the effect of avoiding in advance the occurrence of an abnormality that would hinder the operation of.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an optical transmission / reception circuit according to one embodiment of the present invention, FIG. 2 is a waveform diagram showing an operation example when the level of a transmission optical signal is normal, and FIG. 3 is the level of the transmission optical signal. FIG. 4 is a schematic diagram showing an example of the operation of an optical star network when FIG. 5 is abnormal, and FIG. 5 is a schematic diagram for explaining a conventional inconvenience. 3 ... Transmission carrier detection circuit, 4 ... D flip-flop, 7,8 ... Comparator, 9,10 ... Reception carrier detection circuit, 11 ... And circuit.

Claims (1)

(57) [Claims] An optical network control method using an optical star coupler for equally distributing an optical signal input from a plurality of input ports to a plurality of output ports as a transmission path, comprising the steps of: A level abnormality determining means for determining the level of the signal transmitted from the other terminal based on an abnormality determination level larger than the determination level is provided. When the level abnormality determining means determines that the level is abnormal, transmission of the transmission signal is prohibited. A method for controlling an optical star network.