JPH0927785A - Optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the influence of crosstalk in bidirectional communication by using the carrier waves of frequencies mutually different responding to the direction of transmission when converting the carrier wave modulated by an electric signal to an optical signal and transmitting it. SOLUTION: The optical signal from an optical high burr 3 is converted to the electric signal by an optic/electric converter 12 and extracted from an output terminal 2' after any desired frequency is extracted by a frequency selection filter 13. The transformed frequency of a frequency transformer 10 at a transmitter/receiver 2 is set to be equal with the selected frequency of the filter 13 at a transmitter/receiver 1. Besides, the transformed frequency of a frequency transformer 4 at the transmitter/receiver 1 is set to be different from the selected frequency of the filter 13. Otherwise, the transformed frequency of the transformer 10 at the transmitter/receiver 2 is set to be different from the selected frequency of a frequency selection filter 9 at the transmitter/ receiver 1. Thus, power leaked from an input terminal 1 to the output terminal 2' and from an input terminal 2 to an output terminal 1' can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a communication system in which an optical signal is converted into an optical signal and transmitted through an optical transmission line, and in particular, an optical communication system capable of reducing the influence of crosstalk when performing bidirectional communication on the same optical transmission line. Pertain to.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing an example of the configuration of a conventional optical communication system, in which numeral symbols 1 and 2 are transceivers, 48 and 49 are optical fibers, 50 and 53 are electric / optical converters, 51,52
Represents an optical / electrical converter.

In the figure, an electric signal input to the input terminal 1 on the transmission side of the transceiver 1 is converted into an optical signal by an electric / optical converter (λ1 band or λ2 band) 50, and the optical fiber 48 transmits / receives the signal. 2 to the receiving side. Transceiver 2
At the receiving side of the optical signal, the transmitted optical signal is transmitted to the optical / electrical converter 5
The signal is reconverted into an electric signal at 2 and is output from the output terminal 1 ′ on the receiving side of the transceiver 2.

Similarly, the input terminal 2 on the transmission side of the transceiver 2
The electrical signal input to the optical fiber 4 is converted into an optical signal by the electrical / optical converter (λ1 band or λ2 band) 53.
At 9, the signal is transmitted to the receiving side of the transceiver 1. On the receiving side of the transceiver 1, the transmitted optical signal is transmitted by the optical / electrical converter 51.
Then, it is converted back into an electric signal and outputted from the output terminal 2 '.

FIG. 6 is a diagram showing another example of the configuration of a conventional optical communication system. Numbers 1 and 2 are transceivers, 3 is an optical fiber, 54 and 59 are electric / optical converters, 56 and 57 is light /
Electrical converters 55 and 58 represent optical multiplexers / demultiplexers.

In the figure, on the transmitter side of the transceiver 1, an electric signal input to the input terminal 1 is converted into an optical signal by an electric / optical converter (λ1 band) 54, and an optical multiplexer / demultiplexer 55 is used. Entered in. Since the optical multiplexer / demultiplexer 55 connects the transmission side of the transceiver 1 and the optical fiber 3, the optical signal output from the transmission side of the transceiver 1 is coupled to the optical fiber 3 and transmitted to the transceiver 2. It

In the transceiver 2, the optical multiplexer / demultiplexer 58 connects the optical fiber 3 and the receiving side of the transceiver 2, so that the optical signal from the optical fiber 3 is coupled to the receiving side of the transceiver 2.
It is input to the optical / electrical converter 57, converted again into an electric signal, and output from the output terminal 1 '.

Similarly, on the transmission side of the transceiver 2, the electric signal input to the input terminal 2 is converted into an electric / optical converter (λ2 band).
It is converted into an optical signal by 59 and input to the optical multiplexer / demultiplexer 58. Since the optical multiplexer / demultiplexer 58 connects the transmission side of the transceiver 2 and the optical fiber 3, the optical signal output from the transmission side of the transceiver 2 is coupled to the optical fiber 3 and transmitted to the transceiver 1. .

In the transceiver 1, the optical multiplexer / demultiplexer 55 connects the optical fiber 3 and the receiving side of the transceiver 1, so that the optical signal from the optical fiber 3 is coupled to the receiving side of the transceiver 1.
It is input to the optical / electrical converter 56, re-converted into an electric signal, and output from the output terminal 2 '.

As described above, conventionally, when an electric signal is converted into an optical signal by an electric / optical converter, transmitted through an optical transmission line, and converted into an electric signal by the optical / electrical converter, 1
The wavelength bands of the respective optical / electrical converters were set to be different when transmitting through the optical transmission line of the book. Further, when transmitting using two optical transmission lines, one optical transmission line is set independently in one direction of transmission and reception.

[0011]

In the conventional optical communication system as described above, when bidirectional communication is performed by one fiber by using electric / optical converters of different wavelength bands, the optical multiplexer / demultiplexer crosses. There is a problem that talk occurs and the transmission characteristics deteriorate. In addition, the method of bidirectional communication using two optical fibers has a problem in terms of economical efficiency.

An object of the present invention is to realize bidirectional communication which is hardly affected by crosstalk with one optical transmission line. According to the present invention, the above problems can be solved by the means described in the claims.

That is, according to the invention of claim 1, in an optical communication system in which two transceivers are coupled by a single optical fiber to perform bidirectional communication, modulation is performed by an electric signal on the transmission side of one transceiver. Convert a carrier wave or a frequency-converted signal to an optical signal and send it to the optical fiber transmission line,
The optical signal is optically / electrically converted on the receiving side of the other transceiver to obtain a carrier wave or a frequency-converted signal of the carrier wave, and the carrier wave used on the transmitting side of one transceiver and that of the other transceiver This is an optical communication system in which the carrier wave used on the transmitting side has a different frequency.

According to a second aspect of the invention, in an optical communication system in which two transceivers are coupled by a single optical fiber to perform bidirectional communication, transmission and reception is performed based on a control signal given to each transceiver. An optical switch for switching between reception and the level of a carrier wave to be transmitted or a frequency-converted signal of the carrier wave is checked, and when a signal of a predetermined level or higher is detected, an optical fiber transmission line is connected to the optical switch. And a means for connecting to the transmitter side of the transceiver and sending a control signal to be connected to the receiver side when a signal of a predetermined level or higher is not detected,

A carrier wave modulated by an electric signal on the transmitter side of one transceiver or a signal obtained by frequency-converting the carrier wave is converted into an optical signal and transmitted to an optical fiber transmission line, and the optical signal is received on the receiver side of the other transceiver. Is configured to perform optical / electrical conversion to obtain a carrier wave or a frequency-converted signal thereof,
This is an optical communication system in which the carrier wave used on the transmission side of one transceiver and the carrier wave used on the transmission side of the other transceiver have different frequencies.

According to a third aspect of the present invention, in an optical communication system in which two transceivers are connected by a single optical fiber to perform bidirectional communication, transmission and reception is performed based on a control signal given to each transceiver. Check the optical switch that switches between reception and reception, and the level of the carrier wave to be transmitted or the frequency-converted signal level, and when a signal above a predetermined level is detected,

With respect to the optical switch, means for connecting an optical fiber transmission line to the transmitting side of the transmitter / receiver and sending out a control signal to be connected to the receiving side when a signal of a predetermined level or higher is not detected. The transmitter side of one transceiver converts the carrier wave modulated by an electric signal into an optical signal and sends it out to the optical fiber transmission line, and the receiver side of the other transceiver performs optical / electrical conversion of the optical signal. It is an optical communication system configured to obtain a carrier wave.

According to a fourth aspect of the invention, in the invention according to any one of the first to third aspects of the invention, the light used has the same wavelength band regardless of the transmission direction between the two transceivers. It is a communication method.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a first example of an embodiment for carrying out the present invention, in which numeral symbols 1 and 2 are a transceiver, 3 is an optical fiber, and 4 and 10 are frequency conversion devices. vessel,
5 is an electric / optical converter (λ1 band), 6 and 7 are optical multiplexer / demultiplexers,
Reference numerals 8 and 12 represent optical / electrical converters, 9 and 13 represent frequency selection filters, and 11 represents an electric / optical converter (λ2 band).

This example shows a configuration in the case where signal transmission between the transceiver 1 and the transceiver 2 in the optical communication system is bidirectionally communicated by the optical fiber 3. On the transmission side of the transceiver 1, the electric signal input to the input terminal 1 is converted to a desired frequency by the frequency converter 4 and input to the electric / optical converter (λ1 band) 5.

The inputted electric signal is converted into an optical signal by the electric / optical converter (λ1 band) 5 and inputted to the optical multiplexer / demultiplexer 6. Since the optical multiplexer / demultiplexer 6 connects the transmission side of the transceiver 1 and the optical fiber 3, the optical signal from the transmission side of the transceiver 1 is transmitted to the transceiver 2 via the optical fiber 3.

Since the optical multiplexer / demultiplexer 7 of the transceiver 2 connects the optical fiber 3 and the receiving side of the transceiver 2, the optical fiber 3
The optical signal from is input to the optical / electrical converter 8 on the receiving side of the transceiver 2 and re-converted into an electrical signal, and the electrical signal of the desired frequency is extracted by the frequency selection filter 9 and output terminal 1 '. Taken from.

The conversion frequency of the frequency converter 4 on the transmission side of the transceiver 1 and the selection frequency of the frequency selection filter 9 on the reception side of the transceiver 2 are set to be the same. On the transmission side of the transceiver 2, the electric signal input to the input terminal 2 is converted to a desired frequency by the frequency converter 10 and input to the electric / optical converter (λ2 band) 11.

The inputted electric signal is converted into an optical signal by the electric / optical converter (λ2 band) 11 and inputted to the optical multiplexer / demultiplexer 7. Since the optical multiplexer / demultiplexer 7 connects the transmission side of the transceiver 2 and the optical fiber 3, the optical signal of the transmission side of the transceiver 2 is transmitted to the transceiver 1 through the optical fiber 3.

In the transceiver 1, since the optical fiber 3 and the receiving side of the transceiver 1 are connected by the optical multiplexer / demultiplexer 6, the optical signal from the optical fiber 3 is reconverted into an electrical signal by the optical / electrical converter 12. Then, a desired frequency is extracted by the frequency selection filter 13 and taken out from the output terminal 2 '.
The conversion frequency of the frequency converter 10 on the transmission side of the transceiver 2 and the selection frequency of the frequency selection filter 13 on the reception side of the transceiver 1 are set to be the same.

Further, the conversion frequency of the frequency converter 4 on the transmission side of the transceiver 1 and the selection frequency of the frequency selection filter 13 on the receiver side of the transceiver 1 are set differently, or the transceiver 2 by setting the conversion frequency of the frequency converter 10 on the transmission side and the selection frequency of the frequency selection filter 9 on the reception side of the transceiver 1 to be different from each other, from the input terminal 1 to the output terminal 2'and the input terminal 2 It is possible to reduce the leakage power from the output terminal 1'to the output terminal 1 '.

FIG. 2 is a diagram showing a second example of the embodiment of the present invention, in which reference numeral 21 denotes an electro-optical converter (λ1 band), and the others are the same as those in the case of FIG. is there. In the figure, on the transmission side of the transceiver 1, the electric signal input to the input terminal 1 is converted to a desired frequency by the frequency converter 4 and input to the electric / optical converter (λ1 band) 5. It The input electrical signal is an electrical / optical converter (λ1 band)
It is converted into an optical signal at 5 and input to the optical multiplexer / demultiplexer 6.

Since the optical multiplexer / demultiplexer 6 connects the transmission side of the transceiver 1 and the optical fiber 3, the optical signal from the transmission side of the transceiver 1 is transmitted to the transceiver 2 through the optical fiber 3. In the transceiver 2, since the optical fiber 3 and the receiving side of the transceiver 2 are connected by the optical multiplexer / demultiplexer 7, the optical signal from the optical fiber 3 is input to the optical / electrical converter 8.

Then, it is re-converted into an electric signal, extracted by the frequency selection filter 9 with an electric signal of a desired frequency, and taken out from the output terminal 1 '. The conversion frequency of the frequency converter 4 on the transmitting side of the transceiver 1 and the selection frequency of the receiving side of the transceiver 2 are set to be the same.

On the transmission side of the transceiver 2, the electric signal input to the input terminal 2 is converted to a desired frequency by the frequency converter 10 and is the same as the electric / optical converter 5 on the transmission side of the transceiver 1. The signal is input to the wavelength-band electric / optical converter (λ1 band) 21. The input electric signal is converted into an electric / optical converter (λ
It is converted into an optical signal by the 1st band 21 and is input to the optical multiplexer / demultiplexer 7.

Since the optical multiplexer / demultiplexer 7 connects the transmission side of the transceiver 2 and the optical fiber 3, the optical signal from the transmission side of the transceiver 2 is transmitted to the transceiver 1 through the optical fiber 3. In the transceiver 1, the optical fiber 3 and the receiving side of the transceiver 1 are connected by the optical multiplexer / demultiplexer 6, so that the optical signal from the optical fiber 3 is reconverted into an electrical signal by the optical / electrical converter 12. .

Then, by the frequency selection filter 13,
The desired frequency is extracted and taken out from the output terminal 2 '. The conversion frequency of the frequency converter 10 on the transmission side of the transceiver 2 and the selection frequency of the frequency selection filter 13 on the reception side of the transceiver 1 are set to be the same.

A frequency selection filter 13 of the transceiver 1;
Select the frequency band selected by the frequency selection filter 9 of the transceiver 2.
By making different settings, the wavelength bands of the optical signals of the electric / optical converter (λ1 band) 5 and the electric / optical converter (λ1 band) 21 are the same, and the optical multiplexer / demultiplexer 6 and the optical multiplexer / demultiplexer are used. Even when the isolation of 7 is not sufficient, the electric signal from the input terminal 1 does not leak to the output terminal 2'and the electric signal from the input terminal 1'does not leak to the input terminal 2.

FIG. 3 is a diagram showing a third example of the embodiment of the present invention, in which numeral symbols 14 and 19 are distributors, and 15,
Reference numeral 20 is a level detector, and 16 and 22 are optical switches. Others are the same as in the case of FIG.

In the figure, on the transmission side of the transmitter / receiver 1, the electric signal input to the input terminal 1 is branched by the distributor 14, and the level detector 15 and the electric / optical converter (λ1 band) 5
Is input to The electrical signal input to the electrical / optical converter (λ1 band) 5 is converted into an optical signal and input to the optical switch 16.

The level of the electric signal input to the level detector 15 is detected, and when the detected level is equal to or higher than the set value, the optical switch 16 causes the electric / optical converter (λ1 band) 5
And the optical fiber 3 are connected to each other, and when the value is less than the set value, the optical switch 16 connects the optical fiber 3 and the optical signal on the receiving side of the transceiver 1
The electric converter 12 is connected.

Therefore, when an electric signal having a certain level or higher is input to the input terminal 1, the optical signal converted by the electric / optical converter (λ1 band) 5 is converted into the optical fiber 3
Is transmitted to the transceiver 2. In the transceiver 2, the received signal is connected to the optical / electrical converter 8 by the optical switch 22, reconverted into an electric signal, and output to the output terminal 1 '.

Similarly, on the transmission side of the transceiver 2, the electric signal inputted to the input terminal 2 is branched by the distributor 19 and inputted to the level detector 20 and the electric / optical converter (λ1 band) 21. The electrical signal input to the electrical / optical converter (λ1 band) 21 is converted into an optical signal and input to the optical switch 22.

The level of the electric signal input to the level detector 20 is detected, and when the detected level is equal to or higher than the set value, the optical switch 22 causes the electric / optical converter (λ1 band) 21 to operate.
And the optical switch 3 are connected to each other, and when the value is less than the set value, the optical switch 22 causes the optical fiber 3 and the optical signal on the receiving side of the transceiver 2
The electrical converter 8 is connected.

Therefore, when an electric signal above a certain set value level is input to the input terminal 2, the optical signal converted by the electric / optical converter (λ1 band) 21 is transmitted by the optical fiber 3 to the transceiver 1 Be transmitted to. In the transceiver 1, it is connected to the optical / electrical converter 12 by the optical switch 16, reconverted into an electric signal and output to the output terminal 2 '.

Here, if the electric signal to the input terminal 1 of the transceiver 1 and the electric signal to the input terminal 2 of the transceiver 2 are alternately input with respect to time, the transceiver 1 and the transceiver 2 are connected to the optical fiber. Two-way communication is possible via

FIG. 4 is a diagram showing a fourth example of the embodiment of the present invention, in which each numeral symbol is the same as in FIG. 2 or FIG. In the figure, on the transmission side of the transceiver 1, the electric signal inputted to the input terminal 1 is branched by the distributor 14 and inputted to the level detector 15 and the frequency converter 4.

The electric signal input to the frequency converter 4 is
The frequency is converted and input to the electric / optical converter (λ1 band) 5. In the electric / optical converter (λ1 band) 5, the frequency-converted electric signal is converted into an optical signal, and the optical switch 16
Is input to

The level detector 15 detects the level of the input electric signal. When the detected level is equal to or higher than the set value, the electric switch 16 is connected to the electric / optical converter (λ1).
Output a control signal for connecting the optical fiber 3 to the optical band 3, and if it is less than a set value,
Optical fiber 3 and optical / electrical converter 1 on the receiving side of transceiver 1
The control signal for connecting 2 is output.

Therefore, when an electric signal above a certain set value level is input to the input terminal 1, the optical signal converted by the electric / optical converter (λ1 band) 5 is transmitted by the optical fiber 3 to the transceiver 2 Be transmitted to. In the transceiver 2, it is connected to the optical / electrical converter 8 by the optical switch 22, re-converted into an electric signal, the desired frequency is selected by the frequency selection filter 9, and output to the output terminal 1 '.

Similarly, on the transmission side of the transceiver 2, the electric signal inputted to the input terminal 2 is branched by the distributor 19 and inputted to the level detector 20 and the frequency converter 10. The electric signal input to the frequency converter 10 is frequency-converted and input to the electric / optical converter (λ1 band) 21.

In the electric / optical converter (λ1 band) 21, the frequency-converted electric signal is converted into an optical signal and input to the optical switch 22. The level detector 20 detects the level of the input electric signal, and when the detected level is equal to or higher than the set value, the electric / optical converter (λ1 band) 21 and the optical fiber 3 are connected to the optical switch 22. And outputs a control signal for connecting the optical fiber 3 and the optical / electrical converter 8 on the receiving side of the transceiver 2 to the optical switch 22 when the value is less than the set value. Output.

Therefore, when an electric signal above a certain set value level is input to the input terminal 2, the optical signal converted by the electric / optical converter (λ1 band) 21 is converted into the optical fiber 3
Is transmitted to the transceiver 1. In the transceiver 1, the optical switch 16 is connected to the optical / electrical converter 12, reconverted into an electric signal, a desired frequency is selected by the frequency selection filter 13 and output to the output terminal 2 '.

Here, it is assumed that the electric signal to the input terminal 1 of the transceiver 1 and the electric signal to the input terminal 2 of the transceiver 2 are alternately input in time, and the frequency converter on the transmission side of the transceiver 1 is used. 4, the selection frequency of the reception side frequency selection filter 9 of the transceiver 2, the conversion frequency of the transmission side frequency converter 10 of the transceiver 2, and the selection of the reception side frequency selection filter 13 of the transceiver 1. By setting the frequencies to be the same, bidirectional communication via the optical fiber 3 becomes possible.

Further, by setting the frequencies of the transmitting side and the receiving side in the transceiver 1 and the transceiver 2 to be different from each other, even if the isolation of the optical switches 16 and 22 is not sufficient, the input terminal 1 to the output terminal 2 It is possible to reduce the leakage power from ′ or the input terminal 2 to the output terminal 1 ′.

[0051]

As described above, according to the present invention, 1
There is an advantage that bidirectional communication that is hardly affected by crosstalk can be realized in the optical transmission line of the book.

That is, according to the first aspect of the invention, in the optical communication system in which two transceivers are coupled by a single optical fiber to perform bidirectional communication, a carrier wave modulated by an electric signal is converted into an optical signal. In this case, the influence of crosstalk is reduced by using carrier waves having different frequencies depending on the transmission directions.

According to a second aspect of the present invention, in the optical communication system according to the first aspect, transmission / reception switching of the transceiver is performed using an optical switch, and when an electric signal is input, the transmitter side of the transceiver is When the optical signal is connected and the electric signal is not input, the receiving side of the transceiver is connected to the optical fiber to reduce the influence of crosstalk.

According to the third aspect of the invention, in an optical communication system in which two transceivers are connected by a single optical fiber to perform bidirectional communication, transmission / reception switching of the transceivers is performed by using an optical switch. When a signal is input, the transmission side of the transceiver is connected to an optical fiber, and when the electrical signal is not input, the reception side of the transceiver is connected to an optical fiber, and the electrical signal is The effect of crosstalk is reduced by controlling the optical switch in synchronization with the input of.

In the invention of claim 5, in each of the inventions of claims 1 to 3, the wavelength band of light used for signal transmission between two transceivers is the same regardless of the signal transmission direction. To do. In the present invention, as described above, even if the light of the same wavelength band is used in one transmission path regardless of the transmission direction,
It is possible to realize bidirectional communication that is not easily affected by crosstalk.

[Brief description of drawings]

FIG. 1 is a diagram showing a first example of an embodiment of the present invention.

FIG. 2 is a diagram showing a second example of an embodiment of the present invention.

FIG. 3 is a diagram showing a third example of an embodiment for carrying out the present invention.

FIG. 4 is a diagram showing a fourth example of an embodiment for carrying out the present invention.

FIG. 5 is a diagram showing an example of a configuration of a conventional optical communication system.

FIG. 6 is a diagram showing another example of the configuration of a conventional optical communication system.

[Explanation of symbols]

 1, 2 Transceiver 3 Optical fiber 4,10 Frequency converter 5,21 Electric / optical converter (λ1 band) 6,7 Optical multiplexer / demultiplexer 8,12 Optical / electrical converter 9,13 Frequency selection filter 11 Electric / Optical converter (λ2 band) 14,19 Distributor 15,20 Level detector 16,22 Optical switch

Claims (4)

[Claims] 1. In an optical communication system in which two transceivers are coupled by a single optical fiber for bidirectional communication, a carrier wave modulated by an electric signal or a frequency conversion of the carrier wave is performed on the transmission side of one transceiver. The optical signal is converted into an optical signal and sent out to the optical fiber transmission line, and the optical signal is converted into an optical signal on the receiving side of the other transceiver to obtain a carrier wave or a frequency-converted signal of the carrier wave. However, an optical communication system characterized in that the carrier wave used on the transmission side of one transceiver and the carrier wave used on the transmission side of the other transceiver have different frequencies. 2. An optical communication system in which two transceivers are coupled by a single optical fiber for bidirectional communication, and an optical switch for switching between transmission and reception based on a control signal given to each transceiver. When the level of a switch and a carrier wave to be transmitted or a signal obtained by frequency-converting the carrier wave is checked, and a signal of a predetermined level or higher is detected, an optical fiber transmission line is connected to the transmitter side of the transceiver with respect to the optical switch And a means for transmitting a control signal to be connected to the receiving side when a signal of a predetermined level or higher is not detected, and the transmitting side of one of the transceivers modulates the carrier wave with an electric signal or this The frequency-converted signal is converted into an optical signal and sent out to the optical fiber transmission line, and the optical signal is converted into an optical signal at the receiving side of the other transceiver, and the carrier wave or this is frequency-converted. Signal configured to obtain the optical communication system, characterized in that the different frequencies and carriers used in the transmission side of the carrier and the other transceiver for use in transmitting side of one of the transceivers. 3. An optical communication system in which two transceivers are coupled by a single optical fiber to perform bidirectional communication, and an optical transmission / reception switching operation for each transceiver is performed based on a control signal. When the level of a switch and a carrier wave to be transmitted or a signal obtained by frequency-converting the carrier wave is checked, and a signal of a predetermined level or higher is detected, an optical fiber transmission line is connected to the transmitter side of the transceiver with respect to the optical switch. And a means for sending a control signal to be connected to the receiving side when a signal of a predetermined level or higher is not detected. The optical communication system is characterized in that the optical signal is converted into the optical fiber transmission line and transmitted to the optical fiber transmission line, and the optical signal is converted into an optical signal on the receiving side of the other transceiver to obtain a carrier wave. 4. The scope of claims 1 to 3 in which the wavelength bands of light used are the same regardless of the transmission direction between the two transceivers.
The optical communication system according to any one of 1.