JPS62272614A - Automatic optical heterodyne receiver for selecting frequency - Google Patents

Abstract

PURPOSE:To attain the selective reception of whether a signal to its own station is sent among a large number of communication opposites automatically, among a great number of optical frequencies, by switching a switch to a frequency discriminating circuit side when the signal is decided as the one to its own station at a decision circuit. CONSTITUTION:At the output of a demodulator 4, a decision circuit 10 which emits the signal by discriminating whether the signal is the one to its own station, and switching the switch, a saw-tooth wave generation circuit 9 to sweep the optical frequency of a local oscillation light source 5 on the output of the above circuit, and a switch 8 which switches the output of a frequency discriminating circuit 7, and that of the saw-tooth wave generation circuit 9, are provided. Normally, the switch 8 is connected to continuous line side in figure, and sweeps the optical frequency of the local oscillation light source 5 by the output of the saw- tooth wave generation circuit 9 through a driving circuit 6. At the time of deciding the signal as the one to its own station by the decision circuit 10 with a certain optical frequency, the signal is sent to the switch 8, and the switch is switched to dotted line side, in figure thereby, an automatic frequency control loop is constituted. In this way, it is possible to select the frequency to its own station out of the great number of optical frequencies automatically, and to perform the reception stably.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Summary] In a coherent optical communication system in which a large number of subscribers arbitrarily communicate with each other by optical frequency multiplexing, signals addressed to the own station are transmitted from a large number of communication partners. The present invention provides an automatic frequency selection optical heterodyne receiver that automatically selects and receives reception from among a large number of optical frequencies.

[Industrial application field]

The present invention is an optical frequency multiplexing heterodyne communication system that multiplexes a large number of coherent light waves and communicates with each other, which is currently being actively researched. This invention relates to an automatic frequency selection optical heterodyne receiver that enables reception.

To explain one example of the above system, as shown in FIG. 5, n subscriber devices 3 each having a transmitter, a receiver, and a terminal
1 to 3n connect to an nXn optical coupler 3 via an optical fiber.
For example, subscriber equipment 31
When sends out a signal, the nXn optical coupler 30 causes
The signal is transmitted to all the subscriber devices 31 to 3n, and each subscriber device that receives the signal demodulates it into a Hazeband signal, and then, if it is addressed to its own station, transfers the signal to its own terminal. In addition, in order to reduce erroneous reception when all subscriber units transmit at the same time, each subscriber unit is assigned a unique transmission optical frequency.

Therefore, it is desired to provide a receiver that automatically selects an optical frequency sent to its own station from among a large number of optical frequencies transmitted from these subscriber devices.

[Prior art and problems to be solved by the invention] A practical receiver for use in an optical frequency multiplexed heterodyne communication system has not yet been announced, but an optical heterodyne system that receives sub-frequency light waves is proposed. There is a receiver as shown in FIG.

The optical carrier frequency of the input signal and the optical frequency from the local oscillation light source 5 are combined by the optical coupler 1, and converted into an electrical signal by the opto-electric conversion element 2, and the resulting beat signal is an intermediate frequency. The signal is amplified by an intermediate frequency amplifier 3,
The signal is demodulated by a demodulator 4 so that a Haeshand signal can be obtained.

At this time, fluctuations in the intermediate frequency are detected by the frequency discrimination circuit 17, and according to the fluctuations, the optical frequency of the local oscillation light source 5 is changed via the drive circuit 6 to follow the fluctuations in the optical carrier frequency of the input signal. An automatic frequency control loop is provided to keep the intermediate frequency constant.

In addition, in order to increase the detection efficiency by matching the polarization plane of the optical carrier frequency of the input signal and the optical frequency from the local oscillation light source 5, and to keep the peak value of the output of the intermediate frequency amplifier 3 constant, the polarization plane is controlled. A control circuit 11 and a drive circuit 12 are provided that drive the polarization control circuit 11 using the output of a peak detection circuit 13 that obtains a peak value.

However, if this receiver is used in an optical frequency multiplexing heterodyne communication system, when a large number of light waves are input, the frequency discrimination circuit 17 can only discriminate a single frequency, and other frequencies can be freely received. There is a problem that it cannot be done.

[Means for solving problems]

As shown in FIG.
, and converted into an electrical signal by the photoelectric conversion element 2,
The output of the receiving circuit is amplified by the intermediate frequency amplifier 3, demodulated by the demodulator 4, and outputted by the determination circuit 10, which determines whether the signal is addressed to the own station or not and issues a switching signal, and the output of the receiving circuit includes a large number of light waves. A sawtooth wave generation circuit 9 is used to sweep the optical frequency of the local oscillation light source 5 in order to select the optical frequency addressed to the local oscillation light source 5 from among them, and a fluctuation in the intermediate frequency is detected in the output of the intermediate frequency amplifier 3. A frequency discriminator circuit 7 is provided, a switch 8 is provided for switching between the output of the frequency discriminator circuit 7 and the output of the sawtooth wave generating circuit 9, and a drive circuit 6 for driving the local oscillation light source 5 is provided at the output of the switch 8. Normally, the switch 8 is connected to the sawtooth wave generation circuit 9 side, and when the judgment circuit 10 judges that the signal is addressed to the own station, the switch 8 is connected to the frequency discrimination circuit 7 side by the signal from this. The invention is solved by the automatic frequency selection optical heterodyne receiver of the present invention, which switches to form an automatic frequency control loop.

[Operation] According to the present invention, in order to select an optical frequency addressed to the own station from among a large number of light waves, the switch 8 is normally connected to the sawtooth wave generation circuit 9 side, and the sawtooth wave generation circuit 9 The optical frequency of the local oscillation light source 5 is swept, and when the determination circuit 10 determines that the signal is addressed to the local station, the switch 8 is switched to the frequency discrimination circuit 7 side to form an automatic frequency control loop to stabilize the signal. Since the receiver can be used for optical frequency multiplexing heterodyne communication systems, a receiver can be obtained.

〔Example〕

FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 shows that the address of the local station is 1. FIG. 4 is a block diagram showing the configuration of the main part of the determination circuit in the case of O, 1, and 1. FIG. 4 is a frame configuration diagram of an example signal.

In the figure, 8 is a switch, 9 is a sawtooth wave generation circuit, 10 is a determination circuit, 15 is a frame synchronization circuit, 16 is a frame signal generation circuit, 17 to 22 are AND circuits, 23 to 26 are D type flip-flops, and 27 is a A knot circuit is shown, and the same reference numerals indicate the same functions throughout the drawings.

The difference in FIG. 2 from the case in FIG. 6 is that the output of the demodulator 4 is equipped with a determination circuit 10 that determines whether the signal is addressed to the local station or not and issues a switching signal, which will be described in detail later. A sawtooth wave generation circuit 9 for sweeping the optical frequency of the oscillation light source 5 and a switch 8 for switching between the output of the frequency discrimination circuit 7 and the output of the sawtooth wave generation circuit 9 are provided.

Mainly explaining this point, normally the switch 8 is on the solid line side, and the optical frequency of the local oscillation light source 5 is swept by the output of the sawtooth wave generating circuit 9 via the driving circuit 6.

At this time, when the determination circuit 10 determines that the signal is addressed to the own station at a certain optical frequency, the signal is sent to the switch 8 and switched to the dotted line side, forming an automatic frequency control loop. Also, the judgment circuit 10
A reset signal is sent to the sawtooth wave generating circuit 9 to reset it.

When it is determined that the signal addressed to the own station has ended, a signal is sent to the switch 8 to switch to the solid line side, and a start signal is sent to the sawtooth wave generating circuit 9 to start the sweep.

In this way, the one addressed to the local station is automatically selected from among a large number of optical frequencies, and stable reception becomes possible.

The signal in this case is a burst signal, and the frame structure is as shown in Fig. 4: a preamble area a that sends an all-1 signal that has no meaning until a steady state is reached, a frame synchronization signal area b, and a partner station identification number. Area C1 is composed of an own station identification number area d, an information area e, and a stop signal area f indicating the end.

Next, the details of the portion of the determining circuit 10 that determines that the signal is directed to the local station will be explained using FIG. 3, taking as an example the case where the address of the local station is 1, 0, 1.1.

A frame signal is sent from the frame signal generation circuit 16 to the frame synchronization circuit 15, and based on this, frame synchronization of the input data is performed, and the data is input to the AND circuit 17.

In addition, when frame synchronization is achieved, a signal is sent to the AND circuit 17 to open the gate only while the partner station identification number area C is input from the frame signal generation circuit 16, If so, the partner station identification number is 1, O, l.

■ is output.

This signal is connected to D type flip-flops 23, 24, 25
．． 26, and the signals are input to AND circuits 18, 19, 20, and 21 from their respective outputs.

On the other hand, AND circuits 18, 19, 20.21 contain NOT circuit 2 if the address of the own station is 1, 0.1.1 is O.
If they match, the AND circuit 22 outputs a rubel signal to determine that the signal is addressed to the own station. If it is determined that the address is for the own station, this determination signal is used to send a signal for switching to the switch 8 and a reset signal to the sawtooth wave generating circuit 9.

〔Effect of the invention〕

As explained in detail above, according to the present invention, it is possible to detect whether signals addressed to the own station have been transmitted from a large number of communication partners, which is used in a coherent optical communication system in which a large number of subscribers communicate arbitrarily with each other by optical frequency multiplexing. This has the effect of providing an automatic frequency selection optical heterodyne receiver that can automatically selectively receive signals from a large number of optical frequencies.

[Brief explanation of drawings]

Figure 1 is a block diagram of the principle of the present invention, Figure 2 is a block diagram of an embodiment of the present invention, and Figure 3 is the configuration of the main part of the determination circuit when the address of the own station is 1, 0, 1.1. 4 is a block diagram showing an example of a signal frame structure, FIG. 5 is a block diagram of an example of an optical frequency multiplexing heterodyne communication system using an NxN optical coupler, and FIG. 6 is a signal frame structure diagram. It is a figure showing one example. In the figure, ■ is an optical coupler, 2 is a photoelectric conversion element, 3 is an intermediate frequency amplifier, 4 is a demodulator, 5 is a local oscillation light source, 6.12 is a drive circuit, 7 is a frequency discrimination circuit, 8 is a switch, 9 10 represents a sawtooth wave generation circuit, 10 represents a determination circuit, 11 represents a polarization control circuit, and I3 represents a peak detection circuit. Rate 5 Mouth 7 Hete Uzo'ishi Reception 0) 1 case 0 Brotsukuro confectionery Buri

Claims (1)

[Claims] In a coherent optical communication system that multiplexes a large number of light waves and communicates with each other, the optical carrier frequency of an input signal and the optical frequency from a local oscillation light source (5) are connected by an optical coupler (1). The signals are combined, converted into electrical signals by a photoelectric conversion element (2), and then sent to an intermediate frequency amplifier (3).
), the demodulator (4) demodulates and outputs the output of the receiving circuit, and the determination circuit (10) determines whether the signal is addressed to the own station or not and issues a switching signal. A sawtooth wave generation circuit (9) for sweeping the optical frequency of the local oscillation light source (5) in order to select the optical frequency addressed to the local station from among the light waves, and the output of the intermediate frequency amplifier (3). A frequency discrimination circuit (7) for detecting fluctuations in the intermediate frequency is connected to the frequency discrimination circuit (7), and the output of the frequency discrimination circuit (7) and the sawtooth wave generation circuit (9) are connected to each other.
), and a drive circuit (6) for driving the local oscillation light source (5) is provided at the output of this switch (8), and normally the switch (8) is connected to the sawtooth wave generating circuit (9). ) side and repeatedly sweeps the frequency of the local oscillation light source (5), and when the determination circuit (10) determines that the signal is addressed to the local station, the signal from this is used to switch the switch (8). ) is switched to the frequency discrimination circuit (7) side to form an automatic frequency control loop.