JPH07336303A - Optical spatial duplex communication equipment - Google Patents

Abstract

PURPOSE:To eliminate influence by interference waves from the projector of a present equipment by detecting the level of an interference wave component which sneaks in from the projector of the present equipment provided in output demodulated in a reception part, generating the electric signals of a phase opposite to the interference wave component in a transmission part and adding it to the demodulated output of the reception part. CONSTITUTION:The transmission modulation waves of f1bps outputted from a driver 3 are transmitted through an E/O conversion circuit 2 by the projector 1 and inputted to an opposite phase circuit 20 and the frequency component of the phase opposite to the transmission modulation waves is prepared. Then, delay for which the sneak time of the interference waves is considered is performed in a phase correction circuit 21 and input to a level control circuit 22 is performed. In the meantime, the demodulation signals of a light receiver 5 amplified in a buffer amplifier circuit 7 are inputted to a level detection circuit 24 and the level of the interference waves which sneak in from the projector 1 is detected and inputted to the circuit 22. The circuit 22 makes the level of the frequency component of the opposite. phase coincide with the level of the interference waves, performs output to an addition circuit 23 and eliminates the interference waves in reception signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical space duplex communication device for performing simultaneous transmission and reception by using light as a communication medium.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a schematic structure of an optical space duplex communication apparatus of this type. In the figure, 1 is a projector, 2 is an electric / optical conversion circuit, 3 is a driver, and 4 is a driver. A light receiving lens, 5 is a light receiver, 6 is an optical / electrical conversion circuit, 7 is a buffer amplifier, 8 is a BPF, 9 is a main amplification circuit, and 10 is an optical mask. In a conventional optical space duplex communication device, two devices as shown in FIG. 2 are installed in a communication distance and bidirectionally convert a signal modulated with a data signal into an optical signal for simultaneous transmission and reception.

That is, f ₁ b input to the driver 3
A digital modulation input such as Manchester code of ps is amplified and waveform-shaped by the driver 3, converted into an optical signal by the electric / optical conversion circuit 2, and the projector 1 is turned ON / OFF according to the modulation input of f ₁ bps. It is transmitted as an optical signal to the counterpart communication device (not shown). An optical signal from the other party's communication device is received by the light receiver 5 via the light receiving lens 4, converted into an electric signal by the optical / electrical conversion circuit 6, and the buffer amplifier 7
After being amplified by, the pass band is limited by BPF8, and a digital signal of f ₂ bps as a demodulation signal is taken out,
It is amplified by the main amplifier circuit and output.

In such an optical space duplex communication device, an optical signal of f ₁ bps projected from the projector 1 to the other party communication device due to its structure and external factors causes an interference wave component (which is Δf Directly wrap around as ₁ ), S / N
The phenomenon of degrading the ratio occurs. Therefore, in order to prevent the deterioration of the reception performance due to the interference wave component Δf ₁ ,
In the conventional optical space duplex communication device, an optical mask 10 is provided between the light projector 1 and the light receiver 5 to block an interference wave from the light projector 1, and a BPF 8 is provided to improve reception performance by the interference wave. It has a structure that prevents deterioration.

[0005]

In the conventional optical space duplex communication device, an optical mask is provided to prevent the interference wave from the projector from reaching the receiver of the device and deteriorating the receiving performance. Although it has a structure for blocking the interference wave and a structure for providing a band limiting filter, the structure becomes complicated when the optical mask is provided because the device becomes large in size. In addition, it is difficult to stably extract only the signal with the band-limiting filter, and when high attenuation characteristics are required, it is difficult to secure stable performance even if the number of filters is increased.

The present invention has been made to solve the above problems, and it is possible to eliminate the influence of the interference wave from the projector of the own device without the need to provide an optical mask or a high-performance band limiting filter. It is intended to provide a communication device.

[0007]

In the optical space duplex communication apparatus according to the present invention, an interference wave component (which is referred to as Δf ₁₎ which is included in the output demodulated into an electric signal by the receiving unit and which wraps around from the projector of the own apparatus. ) Means for detecting the level, the transmitter,
An electric signal having a phase opposite to that of the modulation frequency f ₁ is generated, the phase thereof is exactly opposite to the phase of the above Δf ₁ , and the frequency component −Δf ₁ adjusted so that the level thereof is also the same as the electric signal at the above receiving unit. And a means for adding the demodulated output to the.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 2 designate the same or corresponding parts, 20 is an anti-phase circuit, 21 is a phase correction circuit, and 22 is a level control circuit. , 23 is an adding circuit, 24 is an interference wave level detecting circuit, and 25 is a voltage amplifying circuit.

Next, the operation will be described. The transmission modulated wave of f ₁ bps output from the driver 3 is the antiphase circuit 20.
Is also input to the transmission modulation wave, and a frequency component having a phase opposite to that of the transmission modulation wave is generated (this is referred to as −f ₁ ), and delay is performed in the next phase correction circuit 21 in consideration of the wraparound time of the interference wave, and its antiphase Is input to the level control circuit 22. On the other hand, the demodulated signal amplified by the buffer amplifier circuit 7 contains the signal f ₂ bp from the receiver of the other party as described above.
In addition to s, the interference wave component Δf ₁ which is the interference wave from the projector 1 of the own device is also included. Therefore, the buffer amplifier circuit 7
Is inputted to the interference wave level detection circuit 24, only Δf ₁ is taken out and its level is detected, and it is inputted to the level control circuit 22 via the AMP 25. f ₁
The frequency component −Δf ₁ matched with this level is output to the adder circuit 23.

That is, the interference wave level detection circuit 24, AM
The level of the interference wave component Δf ₁ included in the output from the buffer amplifier circuit 7 is detected by P25, this level information is input to the level control circuit 22, and the signal f ₁ from the anti-phase circuit 20 and the phase correction circuit 21 is detected. The output level of the frequency component −f _{1 having} a phase opposite to that of
This frequency component −Δf ₁ is output to 3. Adder circuit 2
In 3, the calculation of (Δf ₁ + f ₂ ) + (− Δf ₁ ) = f ₂ is performed to cancel the interference wave Δf ₁ from the projector 1.
The main amplifier circuit 9 amplifies and outputs a demodulated signal of f ₂ bps.

As described above, the optical space duplex communication apparatus of the present invention eliminates the interference wave from the projector 1. Even when the level of the interference wave component Δf ₁ included in the output from the buffer amplifier circuit 7 fluctuates, the level is monitored by the interference wave level detection circuit 24 and the AMP 25, and the information is input to the level control circuit 22. Since the output level of the frequency component −Δf ₁ to the adding circuit 23 is adjusted, the levels of Δf ₁ and −Δf ₁ can always be made to coincide with each other, and the interference wave Δf ₁ can be dynamically removed. Therefore, by appropriately selecting the transmission frequency f ₁ and the reception frequency f ₂ , the interference wave Δf ₁ can be removed and the deterioration of the reception sensitivity due to the interference wave can be minimized.

[0012]

As described above, the optical space duplex communication device of the present invention eliminates the wraparound of the interference wave from its own device without the need of providing a blocking structure provided with an optical mask or the like or providing a high-performance BPF. As a result, a high performance device can be obtained. Also in terms of structure, an optical mask (hood) between the light projecting section and the light receiving section is not required, so that the degree of freedom in design is increased and the size can be reduced. Further, even if the level of the interference wave included in the received signal fluctuates, it can be canceled while automatically adjusting the level, and fine adjustment becomes unnecessary.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing an example of a configuration of a conventional optical space duplex communication device of this type.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Emitter 2 Electric / optical conversion circuit 3 Driver 4 Light receiving lens 5 Optical receiver 6 Optical / electrical conversion circuit 7 Buffer amplifier 8 BPF 9 Main amplification circuit 10 Optical mask 20 Anti-phase circuit 21 Phase correction circuit 22 Level control circuit 23 Addition circuit 24 Interference wave level detection circuit 25 Voltage amplification circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04B 10/02 10/18

Claims (2)

[Claims] 1. A transmitter controls an optical transmitter with an electric signal having a modulation frequency f ₁ to project light to a partner communication device, and a receiver receives an optical signal controlled at a modulation frequency f ₂ from the partner communication device. In an optical space duplex communication device that receives light by a receiver and demodulates it into an electrical signal and performs simultaneous transmission and reception between communication devices, an interference wave that is included in the output demodulated into an electrical signal by the receiving unit and that wraps around from the projector of the device itself Component (this is Δf ₁
(Referred to as the above), the transmitting section generates an electric signal having a phase opposite to that of the modulation frequency f ₁ and the phase thereof is exactly opposite to the phase of Δf ₁ and the level is also the same. An optical space duplex communication apparatus comprising means for adding the frequency component -Δf ₁ adjusted as described above to an output demodulated into an electric signal by the receiving section. 2. The level control circuit adjusts the level of the frequency component −Δf ₁ by using a level control circuit at the current interference wave component Δf.
An optical space duplex communication device characterized in that level information of ₁ is sequentially input and is controlled by feedback.