JPH03293827A - Optical space transmitter - Google Patents

Abstract

PURPOSE:To eliminate noise components and jitter components by converting a transmission data signal subjected to CMI coding and FSK modulation to the luminance of light to transmit it and subjecting the electric signal, which has the frequency band limited and is subjected to FSK demodulation, to equalizing amplification, timing extraction, and identification and regenerating it to obtain a reception data signal. CONSTITUTION:An FSK modulating circuit 14 takes CMI encoded data as the input and subjects it to FSK modulation and sends it to an LED driving circuit 15, and this circuit 15 drives an LED part 16 to convert the data to the luminance of light and transmits it as an optical transmission signal (h). This signal is received by a light reception circuit 17 and is photo-electrically converted to an electric signal and has the frequency limited by a resonance circuit 17' and is demodulated by an FSK demodulating circuit 18 and is converted to a CMI encoded data signal, and the CMI encoded data signal removing jitter components is generated by an equalizing amplification circuit 19, a timing extracting circuit 20, and an identifying and reproducing circuit 21. Thus, the reception data signal which has no noise components and no jitter components is obtained to accurately transmit the data.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical space transmission device that transmits information using optical signals transmitted and received in space.

[Prior Art] In general, in areas where it is difficult to install communication lines due to deep valleys in mountainous areas, or areas where the installation of communication lines is regulated for aesthetic reasons, optical paths are generally installed in the space between transmitting and receiving points. form,
A method of transmitting information using optical signals during this period is suitable. However, when obstacles such as fog, raindrops, snow, and smoke exist in the optical path that transmits the optical signal, the energy of the optical signal traveling along the optical path is attenuated, making it impossible to distinguish between external light and the original optical signal. Communication quality deteriorates.

For this reason, conventional optical space transmission devices focus on the fact that the brightness of external light fluctuates randomly in the frequency range from several hertz to several hundred hertz, and use the following first method and second method. This method narrows the frequency band of the transmitted signal and converts it into an alternating current signal, during which information is transmitted.

That is, in the first method, the transmission data signal, which is an electrical signal, is modulated at a frequency higher than the fluctuating period of the external light on the transmission side, thereby converting it into light brightness and transmitting it to the reception side. The received optical signal is converted into an electrical signal, and a resonant circuit distinguishes between a signal due to external light and a signal for information transmission, and demodulation is performed to obtain a received data signal.

The second method is to convert the transmission data signal, which is an electrical signal, into a CMI code (coded mark) on the transmission side.
k Inversion) to convert it into light brightness and send it to the receiving side, and on the receiving side, the received optical signal is converted to an electrical signal, and a resonant circuit is used to distinguish the external light signal from the signal for information transmission. Then, equalization amplification, clock extraction, and identification regeneration are performed to obtain a received data signal.

[Problems to be Solved by the Invention] When transmitting an optical signal using the first method of the conventional optical space transmission device described above, there is a problem that it is difficult to reduce jitter components from the obtained received signal. there were. In addition, when transmitting an optical signal by the second method, the first method
Compared to the above method, the width of the band limit of the resonant circuit must be set wider, and there is a problem that external optical noise components cannot be sufficiently removed from the received signal.

[Means for Solving the Problems] In order to solve such problems, an optical space transmission device according to the present invention includes an encoding means for CMI encoding a transmission data signal, and a coder for CMI encoding a transmission data signal. A modulating means for performing FSK modulation, a transmitting means for converting the modulated transmission data signal into optical brightness and transmitting it, and a transmitting means for converting the optical signal received by the optical receiver into an electrical signal and then limiting the frequency band. demodulation means for performing FSK demodulation on the electric signal of the lever;
The apparatus is equipped with a received signal reproducing means for performing equalization amplification, timing extraction, and identification reproduction on the demodulated electrical signal to obtain a received data signal.

[Operation] The transmission data signal is converted into CMI code data, subjected to FSK modulation, converted into light luminance, and transmitted.

Further, the received optical signal is converted into an electrical signal, frequency-limited, and then FSK demodulated, and further subjected to equalization amplification, clock extraction, and discrimination/regeneration. As a result, a received data signal from which noise components and jitter components have been removed is obtained.

[Example] Next, the present invention will be explained with reference to the drawings.

FIGS. 1 and 2 are block diagrams showing an embodiment of the optical space transmission device of the present invention. FIG. 1 shows a block diagram of the transmitting side, and FIG. 2 shows a block diagram of the receiving side. The optical space transmission apparatus shown in FIGS.
It is used to transmit and receive data signals other than MI codes.

In FIG. 1, 1 is a CMI encoding circuit, and 2 is an FSK used for the purpose of removing noise components caused by external light.
(Frequency 5hift Keying) Modulation circuit, 3 is an LED drive circuit, 4 is an LED that is a light emitter
Department. Further, a is a transmission data signal, b is a transmission clock signal, and C is an optical transmission signal to be transmitted.

Next, in FIG. 2, 5 is a light receiving circuit, 5' is a resonant circuit, 6 is an FSK demodulation circuit, 7 is an equalization amplifier circuit, 8 is a timing extraction circuit, 9 is an identification regeneration circuit, and 10 is a CMI decoding circuit. It is. Further, d is an optical reception signal, e is a reception data signal, and f is a reception clock signal.

The operation of the optical space transmission device configured as above will be explained. First, the operation on the transmitting side shown in FIG. 1 will be explained. As described above, a case will be described here in which a data signal other than a CMI code is transmitted.

The CMI encoding circuit 1 receives the transmission data signal a and the transmission clock signal S sent from outside the optical space transmission apparatus, converts them into CMI codes, and sends them to the FSK modulation circuit 2. This FSK modulation circuit 2 inputs this CMI encoded data, performs FSK modulation on this data in order to remove noise components caused by external light, and transmits this data to an LED.
The signal is sent to the drive circuit 3. That is, the FSK modulation circuit 2 modulates the "rH" level part of the CMI encoded data signal at a high frequency and the "L" level part at a low frequency, and sends the modulated signals to the LED drive circuit 3. It becomes. In this way, this LED drive circuit 3
This FSK modulated transmission data is input, and based on this, the LED section 4 is driven to convert it into light brightness, and the LED
The FSK-modulated transmission data is transmitted from the unit 4 as an optical transmission signal C.

Next, the optical transmission signal C transmitted from the light emitter 0 to explain the operation of the receiving side in FIG. The signal d is received, photoelectrically converted into an electrical signal, and the frequency band is limited by the resonant circuit 5'.
The signal is sent to the SK demodulation circuit 6. The FSK demodulation circuit 6 demodulates this FSK modulated electrical signal, converts it into a CMI encoded data signal, and sends it to the equalization amplifier circuit 7. Thus, this CMI encoded data signal is
This equalization amplifier circuit 7. The timing extraction circuit 8 and the identification and reproduction circuit 9 generate a CMI encoded data signal from which jitter components have been removed, and send it to the CMI decoding circuit 10.

FIG. 5 is a timing chart showing the timing of each signal during this period. In the figure, (a) shows the output signal cto'' of the light receiving circuit 5, (b) shows the output signal cto of the resonant circuit 5', and (C) shows the output signal d1 of the equalization amplifier circuit 7. (d) shows the clock output signal d2 of the timing extraction circuit 8, and (e) shows the clock output signal d2 of the timing extraction circuit 8.
The timing of the output signal d of is shown.

As described above, the electric signal do' photoelectrically converted by the light receiving circuit 5 is affected by external light, such as shot noise 31 and fluctuation, but this is removed by the resonant circuit 5'' and the signal do' is The signal ci is sent to the FSK demodulation circuit 6 and demodulated.
The high frequency part of o is demodulated as an rHJ level signal, and the low frequency part is demodulated as an "L" level signal.

That is, this data signal is converted into a CMI encoded data signal by the FSK demodulation circuit 6 and sent to the equalization amplification circuit 7.The zero equalization base width circuit 7 inputs this data signal and performs equalization amplification. An output signal d4 as shown in FIG. 5C is sent to the timing extraction circuit 8 and the discrimination/reproduction circuit 9, but this output signal d4 still contains a jitter component 30.

Further, the timing extraction circuit 8 extracts a clock output signal d2 shown in FIG. Then, the identification and reproduction circuit 9 inputs the output signal d of the equalization amplifier circuit 7 based on this clock output signal d2, identifies and reproduces it, and
As shown in figure (e), the jitter component 30 is removed,
and generates a CMI encoded output signal dS,
(2) Send it to the decoding circuit 10.

Then, CMI decoding processing is performed in this CMI decoding circuit 10, and the received data signal e and the received clock signal of TTL level are regenerated and sent out to the outside of this optical space transmission apparatus.

Next, FIGS. 3 and 4 are block diagrams showing other embodiments of the optical space transmission apparatus of the present invention. And Figure 3 is
A block diagram of the transmitting side is shown, and FIG. 4 is a block diagram of the receiving side. The optical space transmission apparatus shown in FIGS. 3 and 4 transmits and receives data signals of CMI codes.

In FIG. 3, 11 is an equalization amplifier circuit, 12 is a timing extraction circuit, 13 is an identification regeneration circuit, 144 is a tFsK modulation circuit, 15 is an iLED [111 circuit, and 16 is an LED section. The signal h is the optical transmission signal to be transmitted.

Next, in FIG. 4, 17 is a light receiving circuit, 17' is a resonant circuit, 18 is an FSK demodulation circuit, 19 is an equalization amplifier circuit, 2
0 is a timing extraction circuit, and 21 is an identification reproduction circuit.

Further, j is an optical reception signal, and k is a reception data signal.

The operation of the optical space transmission device configured as above will be explained. First, the operation on the transmitting side shown in FIG. 3 will be explained. As described above, a case will be described here in which a CMI code data signal is directly transmitted.

The transmission data signal g, which is CMI encoded data sent from outside the optical space transmission device, is input to the equalization amplifier circuit 11, and the jitter component is C without
Generated as MI encoded data, FSK modulation circuit 14
will be sent to. This FSK modulation circuit 14
Encoded data is input, FSK modulation is applied to this data, and this data is sent to the LP and D drive circuit 15. The LEDM* circuit 15 inputs this FSK modulated transmission data, drives the LED section 15 based on it and converts it into light brightness, and as a result, the LED section 15 outputs the FSK modulated data.
The modulated transmission data is transmitted as an optical transmission signal.

Next, to explain the operation of the receiving side in FIG.
This FSK signal arrives at the light receiving port #117.
The modulated optical reception signal is received, photoelectrically converted, converted into an electrical signal, the frequency band of which is limited by the resonant circuit 17', and sent to the FSK demodulation circuit 18. And F.S.
The Kaj,@ circuit 18 demodulates this FSK modulated electrical signal, converts it into a CMI encoded data signal, and sends it to the equalization amplifier circuit 19.

In this way, this CMI encoded data signal is transmitted to the equalization amplifier circuit 19. A timing extraction circuit 20 and an identification/reproduction circuit 21 generate a CMI encoded data signal from which jitter components have been removed, and send it out of the optical space transmission apparatus as a received data signal.

As explained above, in this optical space transmission device, on the transmitting side, after converting the transmission data signal into CMI code data, FSK is used to remove noise components caused by external light.
It is modulated and converted into light brightness and transmitted. On the receiving side, the received optical signal is converted into an electrical signal and the frequency band is limited, followed by FSK demodulation, equalization amplification, clock extraction and 8M Since the received data signal from which the jitter component has been removed is obtained by performing the reproduction, it is possible to simultaneously remove the noise component and reduce the jitter component of the received data signal.

Furthermore, if the frequencies of the FSK signals between the upstream and downstream signals of this optical space transmission device are set to be different from each other, interference between the upstream and downstream signals can be avoided and reliable bidirectional optical space transmission can be achieved. can be done.

[Effects of the Invention] As explained above, the optical space transmission device according to the present invention converts a transmission data signal into CMT code data and then converts it into FSK code data.
It modulates and converts it into light brightness and transmits it, and also converts the received optical signal into an electrical signal, limits the frequency band, and transmits it.
Since the received data signal is obtained by performing SK demodulation, equalization amplification, clock extraction, and identification regeneration, the received data signal is obtained from which noise components and jitter components caused by external light are removed, and therefore accurate data can be obtained. This has the effect of enabling transmission.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing one embodiment of the optical space transmission device of the present invention, FIGS. 3 and 4 are block diagrams showing other embodiments of this device, and FIG. 5 is a block diagram showing this device. 3 is a timing chart showing the timing of each part of FIG. 1...CMI encoding circuit, 2,14...FSK
Transformer circuit, 3,15...LED drive circuit, 4.16
...LED section, 5.17... Light receiving circuit, 5'
, 17'...resonant circuit, 6,18...FS
K demodulation circuit, 7, 11.19... Equalization amplifier circuit, 8
, 12.20...timing extraction circuit, 9.13.
21...Identification and regeneration circuit, 10...CMI decoding circuit, a, g...Transmission data signal, b--...Transmission clock signal, c, h... Optical transmission signal, d, j...
... Optical reception signal, e, k... Reception data signal, f.
...Receive clock signal.

Claims (1)

[Scope of Claims] An optical space transmission device that includes a light emitter and a light receiver that transmit and receive optical signals, and that transmits information using optical signals that are transmitted and received in space, comprising: an encoding unit that encodes a transmitted data signal by CMI encoding; , a modulation means that performs FSK modulation on the encoded transmission data signal; a transmission means that converts the modulated transmission data signal into optical luminance and transmits it; A demodulating means performs FSK demodulation on the electrical signal after it has been converted into a signal, and a received signal reproducing means performs equalization amplification, timing extraction, and identification regeneration on the demodulated electrical signal to obtain a received data signal. An optical space transmission device.