JPH09153863A - Optical communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a reception signal inputted to a transmission system and to evade oscillation by providing a limitter in a reception system so as to use an amplitude comparing circuit in the transmission system. SOLUTION: Light inputted to a photodiode 30 is optic/electric-converted and inputted to a reception signal processing part 40. It is amplified by an amplifier 41 and amplitude-limited by the limitter in a reception signal processing part 40. On the other hand, a signal inputted from a synthesizing part 50 is compared in the comparing circuit 22 and outputted to a driving circuit 21 when amplitude is more than a set value and LED 10 is driven. The unrequired reception signal which is inputted to a transmission signal processing part 20 by way of the synthesizing part 50 is removed by providing the limitter 42 and the amplitude comparing circuit 22 so that the relative interference of the reception system with the transmission system is reduced. Thus, transmission-reception signal is transmitted with one line but oscillation is not executed and favorable transmission-reception is executed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical communication system such as an optical space transmission system.

[0002]

2. Description of the Related Art For example, as shown in FIG. 5 of Japanese Patent Publication No. 6-66282, an optical communication system has been proposed in which signal transmission paths of a transmission system and a reception system are separated.

[0003]

In a system in which a transmission system and a reception system are separated when a portion for transmitting and receiving light and a portion for generating a transmission signal and a reception signal are separated from each other, a line for transmitting a transmission signal and a reception signal are used. Since it is necessary to prepare separate lines for transmission, there have been problems such as complicated wiring and increased cost.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems of each of the prior arts and to provide an inexpensive optical communication device in which wiring is facilitated.

[0005]

In order to achieve the above object, the present invention uses only one line for transmitting a transmission signal and a reception signal, limits the amplitude of the reception signal, and transmits it by an amplitude comparison circuit. An amplitude comparison circuit that outputs a transmission signal when the signal has an amplitude equal to or larger than a set value is added to the transmission system. Alternatively, the phase of the input signal for outputting the light to the transmission signal processing unit and the phase of the reception signal that has passed through the optical-electrical conversion unit, the reception signal processing unit, and the combining unit at the time of receiving the light do not have the same phase. The phase relationship is as follows.

By the above means, it is possible to transmit the transmission signal and the reception signal by one line, suppress the influence of the reception system on the transmission system, and avoid the oscillation due to the loop of the transmission system and the reception system.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of an optical communication device according to the present invention.

Reference numeral 10 is an LED, 20 is a transmission signal processing section, 2
1 is a drive circuit, 22 is an amplitude comparison circuit, 30 is a photodiode, 40 is a received signal processing unit, 41 is an amplifier, 42 is a limiter (amplitude limiter), and 50 is a combining unit.

The light input to the photodiode 30 is light-
It is electrically converted and input to the reception signal processing unit 40. In the reception signal processing unit 40, the limiter 4 is amplified by the amplifier 41.
Amplitude is limited by 2.

On the other hand, the signal input from the synthesizing section 50 is compared by the comparison circuit 22 and is output to the drive circuit 21 only when the amplitude is equal to or larger than the set value, and the LED 10 is driven.

By providing the limiter 42 and the amplitude comparison circuit 22, unnecessary reception signals input to the transmission signal processing unit 20 via the synthesizing unit 50 can be removed, and the reception system and the transmission system can be removed. Mutual interference can be reduced.

FIG. 2 is a block diagram showing a second embodiment of the optical communication apparatus according to the present invention.

Reference numeral 43 is a phase shifter. The same reference numerals as those in FIG. 1 have the same functions.

The transmission signal from the transmission / reception signal processing section is input to the combining section 50. The output of the synthesizing unit 50 is input to the transmission signal processing unit 20 and subjected to waveform shaping and the like to drive the LED 10.

The received signal received by the photodiode 30 and photoelectrically converted is input to the received signal processing section 40, amplified by the amplifier 41, phase-shifted by the phase shifter 43, and output to the synthesizing section 50.

The combining unit 50 outputs the received signal to the transmission / reception signal processing unit and outputs the transmission signal from the transmission / reception signal processing unit to the transmission signal processing unit.

In the system as shown in FIG. 2, it is necessary to prevent interference between transmission and reception. For example, turn optical communication on / off
A description will be given of a system that is performed in the OFF state.

A transmission signal for turning on the LED 10 is input from the synthesizing unit 50, and the photodiode 30 emits light of O.
When N is received, the reception signal processing unit 40 and the combining unit 5
If a signal for turning on the LED is input to the transmission signal processing unit 20 after passing 0, the LED 10
When is turned ON, oscillation occurs and ON / OFF is repeated.

In order to prevent such interference between transmission and reception,
It is advisable to change the frequency band of the transmission signal and the reception signal and provide a separation circuit such as a filter in the transmission signal processing unit 20 or the reception signal processing unit 40 to separate the transmission and reception signals. Separation by filters is difficult.

In such a case where the separation circuit such as the filter is provided and the transmission / reception signals cannot be separated, the LED is used.
When a transmission signal that turns ON 10 is input from the combining unit 50, the photodiode 30 passes the reception signal processing unit 40 and the combining unit 50 when the light ON is received and the LED is turned OFF to the transmission signal processing unit 20. By inputting such a signal, it is possible to prevent oscillation when the LED 10 is turned on. For example, when a transmission signal that turns on the LED 10 is input from the combining unit 50,
When the photodiode 30 receives the light ON, it passes through the reception signal processing unit 40 and the combining unit 50 and the transmission signal processing unit 20.
In the case where a signal for turning on the LED is input to, the signal can be realized by providing the phase shifter 43 in the reception signal processing unit 40 or the transmission signal processing unit 20 and changing the phase of the reception signal. . It can also be realized by providing an inverting amplifier or the like as the phase shifter.

According to these methods, even if the transmission / reception signal is transmitted by one line, it is possible to perform excellent transmission / reception without oscillation.

In the above description, the case where the digital communication is performed by turning on / off the light has been described, but it is clear that the same effect can be obtained by the analog communication using the linear portion of the light.

In this embodiment, the transmission signal processing section 40
Although the phase shifter 43 is provided as a means for shifting the phase of the signal in the inside, the phase shifter may be provided in the transmission signal processing unit 20 to change the phase of the transmission signal. Even if the polarity is changed, the light of the photodiode 30
It is obvious that the same effect as this embodiment can be obtained even if the polarity of electric conversion is changed.

[0025]

As described in detail above, according to the present invention, a transmission / reception signal is transmitted by one line, an optical signal is transmitted based on the transmission signal, and an optical signal input from the outside is transmitted. In an optical communication system that outputs a received signal to the above-mentioned line, a limiter (amplitude limiter) is provided in the receiving system when a signal transmitted by itself is received and returns to the transmitting system to affect oscillation. Amplitude comparison circuit 22 in the transmission system
By using, it is possible to avoid oscillation by removing the received signal input to the transmission system.

Oscillation can also be avoided by changing the phase of transmission or reception so that they are not in phase.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

[Explanation of symbols]

 10 ... LED, 20 ... Transmission signal processing part, 21 ... Driving circuit, 22 ... Amplitude comparison circuit, 30 ... Photodiode, 40 ... Received signal processing part, 41 ... Amplifier, 42 ... Limiter (amplitude limiter), 43 ... Phase shift Container, 50 ... Synthesizing part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Nagashima 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd. Hitachi, Ltd. multimedia system development headquarters (72) Inventor Hiroshi Araki Hitachinaka City, Ibaraki Prefecture Kashima Yatsu 2477 Address 3 Hitachi Car Engineering Co., Ltd.

Claims (2)

[Claims] 1. In an optical communication system for transmitting and receiving information by using light, a received signal is input and a transmitted signal is output so that the transmitted and received signals are transmitted through one line, and these signals are combined to form one line. A synthesis unit for transmission, a transmission signal processing unit that receives signals from the synthesis unit and performs processing such as amplification and shaping, and an amplitude comparison that allows only signals having a predetermined amplitude or more in the transmission signal processing unit to pass therethrough. A circuit, an electro-optical converter such as an LED whose output is controlled based on an electric signal from the transmission signal processing unit, and a light such as a photodiode that outputs a strong and weak electric signal based on the strength of received light. An electrical converter, a received signal processing unit that receives the converted electrical signal as an input, performs processing such as amplification and shaping, and outputs the processed signal to the combining unit; and an amplitude limiting circuit in the received signal processing unit. And an optical communication device. 2. In an optical communication system for transmitting and receiving information by using light, in order to transmit a transmission / reception signal on one line, a reception signal is input, a transmission signal is output and these signals are combined to form one line. A synthesizing unit for transmission, a transmission signal processing unit that receives a signal from the synthesizing unit as an input and performs processing such as amplification and shaping, an LED whose output is controlled based on an electric signal from the transmission signal processing unit, and the like. , An optical-electrical converter such as a photodiode that outputs a strong and weak electric signal based on the strength of the received light, and processing such as amplification and shaping using the converted electric signal as an input. A reception signal processing unit for performing output to the synthesizing unit, a phase of an input signal for outputting light to the transmission signal processing unit, and the optical-electrical conversion unit when receiving light, the reception signal The processing unit, the combining unit And it derived the received signal phase, characterized in that a phase relationship that does not cause the in-phase, the optical communication apparatus.