JPH05206949A - Signal transmission system for optical communication system - Google Patents

Abstract

PURPOSE:To normally transmit a signal even if there are reflection and sneak path. CONSTITUTION:Terminal units 2 are provided for respective data terminals. A satellite unit 3 is provided on the construction surface of the ceiling or the like. The signal between the terminal units 2 is transmitted by optical communication through the satellite unit 3. The optical signal from the terminal units 2 is received and the optical signal the same as the optical signal from the satellite unit 3 to the terminal units 2 is transmitted to the terminal units 2. A rise detection circuit 35 and a pulse signal generation circuit 36 are provided for the satellite unit 3. The circuits control the transmission period of the optical signal from the satellite unit 3 so that signal conversion output based on the optical signal transmitted from the satellite unit 3 to the terminal unit 2 coincides with an original pulse width modulation signal which is transmitted from the terminal unit 2. Thus, abnormality in the optical signal transmitted from the satellite unit owing to reflection and sneak path is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal transmission system of an optical space transmission system for transmitting data by optical signals between a plurality of data terminals set in an indoor space such as an office or a home.

[0002]

2. Description of the Related Art Conventional data transmission between data terminals (for example, personal computers) in a room is generally performed by a wire transmission method using a communication cable. However, a transmission method using an optical space transmission technology is considered due to an increasing demand for wiring saving and construction saving.

FIG. 3 shows an optical space transmission system using this type of optical space transmission technology. In this free-space optical transmission system, as shown in FIG. 3, each data terminal 1 installed in the same space is provided with a plurality of terminal units 2 for transmitting and receiving data by optical signals, and the above-mentioned construction surface such as a ceiling is provided on the above-mentioned construction. A plurality of satellite units 3 for transmitting and receiving optical signals to and from the terminal unit 2 are provided. It should be noted that each terminal unit 2 is connected to each data terminal 1 by a transmission line L ₁ , and each satellite unit 3 is connected to each other by a transmission line L ₀ .

In the case of this optical space transmission system, the terminal unit 2 performs data transmission by optical space transmission via the satellite unit 3 installed on the ceiling, and performs data transmission between a plurality of data terminals 1. More specifically, the data from the data terminal 1 is transferred to the terminal unit 2
From the satellite unit 3 to the satellite unit 3, the satellite unit 3 transmits data to the other satellite unit 3 via the transmission line L ₀ , and the data is transmitted from each satellite unit 3 to the terminal unit 2 by spatial transmission. By performing the transmission, the data transmission between the data terminals 1 is performed.

By the way, it is preferable that the satellite unit 3 is capable of transmitting and receiving at a wide angle so that the installation place of the data terminal 1 is not restricted. Therefore, the satellite unit 3 has a plurality of light receiving elements and light emitting elements. The light receiving element and the light emitting element are arranged in, for example, a fan shape so that transmission and reception can be performed at a wide angle.

[0006]

In this type of optical space transmission system, when the satellite unit 3 receives the optical signal from the terminal unit 2 as described above, data is transmitted to the other satellite unit 3 as described above. At the same time as the transmission, it is necessary to transmit the same optical signal to the terminal unit 2 in the area covered by itself. In other words, this is to enable data transmission between the terminal units 2 within the area covered by one satellite unit 3.

At this time, the optical signal transmitted from the satellite unit 3 to the terminal unit 2 is the terminal unit 2 which has transmitted the optical signal to the satellite unit 3 and whether the satellite unit 3 has correctly received the optical signal. It is also used to confirm whether or not. by the way,
Thus, when the satellite unit 3 receives the optical signal from the terminal unit 2 and at the same time transmits the same optical signal to its own area, as shown in FIG. 4, the light emitting element group 31 and the light receiving element of the satellite unit 3 are received. Element group 3
2 (only one light emitting element 31 and one light receiving element 32 are shown in the figure, but there are actually a plurality), a part of the optical signal is reflected back by the filter cover 3a. come. In addition, it may be reflected by the construction surface such as the wall surface or the floor surface and may return, and further, the filter cover 3
There is a case where a wraparound phenomenon occurs due to a and returns.

If such a signal is present, the satellite unit 3 cannot discriminate the signal from the signal transmitted from the terminal unit 2, so that the signal is also transmitted at the same time. Therefore, although the same optical signal as originally transmitted from the terminal unit 2 is supposed to be transmitted to the terminal unit 2, the pulse width of the optical signal changes, or the optical signal shown in FIG. As shown in), there is a problem that the satellite unit 3 causes a so-called oscillation state in which the transmission state of the optical signal is continued even after the original transmission period of the optical signal has passed, and normal signal transmission cannot be performed. Note that FIG. 5A shows a transmission signal from the terminal unit 2, and FIGS. 5B and 5C show the reflected wave even after the original optical signal transmission period, when the light receiving element group 32 of the satellite unit 3 is used. It is shown that the operation of receiving light and emitting light by the light emitting element group 31 of the satellite unit 3 is repeated by the received output.

The present invention has been made in view of the above points, and an object of the present invention is to provide an optical signal transmission system of an optical space transmission system capable of performing normal signal transmission even if there is reflection or wraparound. To provide.

[0010]

According to the present invention, in order to achieve the above object, an optical signal having the same pulse width as the optical signal transmitted from the terminal unit is transmitted to the terminal unit by the satellite unit. Gate means for regulating the pulse width of the satellite unit is provided in the satellite unit.

In order to achieve the above object more efficiently, the data from the data terminal is converted into a pulse train signal having high and low level change points as pulses, and the pulse train signal is used as data for the data terminal. It is preferable that the terminal unit is provided with a signal conversion function for reverse conversion into the optical pulse signal based on the pulse train signal for transmission of the optical signal between the terminal unit and the satellite unit.

[0012]

According to the present invention, by providing the above-described structure, the gate means prevents the transmission section of the satellite unit from transmitting an optical signal having a pulse width larger than the pulse width of the optical signal transmitted from the terminal unit. That is, even if there is reflection or wraparound, an optical signal due to the reflection is prevented from being transmitted from the satellite unit, and normal signal transmission can be performed.

[0013]

1 and 2 show an embodiment of the present invention. The system configuration of this embodiment is the same as that described in FIG. 3, and the terminal unit 2 performs data transmission by optical space transmission via the satellite unit 3 installed on the ceiling.
Data transmission between a plurality of data terminals 1 is performed.
However, in the case of this embodiment, the signal transmission system of the optical signal is different from the conventional one, but this point will be described later.

As shown in FIG. 1A, the terminal unit 2 includes a light emitting element 24 and a light receiving element 25 for transmitting and receiving optical signals to and from the satellite unit 3, and the data terminal 1.
An interface unit 21 for transmitting data to and from
A pulse train signal conversion circuit 22 for converting a high-level to low-level or low-level to high-level change point of data received by the interface unit 21 into a pulse train signal represented by a pulse; A drive circuit 23 for driving the light emitting element 24 with an output, a receiving circuit 26 for filtering and amplifying the received light output by the light receiving element 25, and further waveform shaping, and a pulse train signal output from the receiving circuit 26 Signal format of data of the data terminal 1 (generally, FIG. 2A is shown between the data terminal 1 and the terminal unit 2).
The base band signal conversion circuit 27 converts the data into a base band signal shown in FIG.

The satellite unit 3 performs a filtering process on the outputs of the light emitting element group 31 and the light receiving element group 32 for transmitting and receiving optical signals to and from the terminal unit 2, and the output of the light receiving element group 32, and further amplifies the waveform. A receiving circuit 33 and an interface unit 34 for transmitting the output of the receiving circuit 33 to another satellite unit 3 and receiving a transmission signal from the other satellite unit 3.
And the output of the receiving circuit 33 or the interface unit 3
4 of the output signal of FIG. 4, a pulse signal generation circuit 36 for generating a pulse signal of a constant width which rises when a rise is detected by the rise detection circuit 35, and the pulse signal generation circuit 36. And a drive circuit 37 for driving the light emitting element group 31 based on the output.

The operation of the optical space transmission system of this embodiment will be described below. Now, if there is a request from the data terminal 1 to transmit data to the terminal unit 2, the data from the data terminal 1 is input to the pulse train signal conversion circuit 22 via the interface section 21,
As shown in FIG. 2B, the data is converted into a pulse train signal in which pulses are output at the rising and falling points of data. Then, the drive circuit 23 drives the light emitting element 24 based on the pulse train signal, so that the optical pulse signal shown in FIG. 3C is transmitted to the satellite unit 3.

In the satellite unit 3, when the light pulse signal is received by the light receiving element group 32, the received light output is filtered by the receiving circuit 33, amplified and waveform-shaped, and transmitted from the interface section 34 to the transmission line L.
_It is sent to another satellite unit 3 via ₀ . At this time, the rising edge of the output of the receiving circuit 33 is determined by the rising edge detection circuit 3
The pulse signal having a constant pulse width is output from the pulse signal generation circuit 36 at the output of the detection circuit 35.

Here, the pulse width of the pulse signal output from the pulse signal generating circuit 36 is set to be substantially equal to the pulse width generated by the pulse train signal conversion circuit 22 of the terminal unit 2. When the rising edge detection circuit 35 detects the rising edge, the rising edge is ignored even if the rising edge is continuously detected in a short period of time. That is, since the bit width indicating "1" or "0" of the data of the data terminal 1 including the microcomputer of this optical space transmission system is constant, once the rising edge is detected by the rising edge detection circuit 35,
Until the period corresponding to the bit width elapses, the receiving circuit 33
The rising edge of the output of is ignored.

Therefore, even if there is a reflected signal from the filter cover as in the conventional case, the signal is not further transmitted based on the reflected signal, and the pulse width of the optical signal transmitted from the satellite unit 3 changes. And does not cause oscillation. That is, the rising edge detection circuit 35 and the pulse signal generation circuit 36 cause the satellite unit 3 to transmit to the terminal unit 2 an optical signal having the same pulse width as the optical signal transmitted from the terminal unit 2. Acts as a gate means to regulate.

The optical signals transmitted from the satellite unit 3 and other satellite units 3 are received by the light receiving element 25 of the terminal unit 2, filtered by the receiving circuit 26, amplified, and shaped in waveform.
The output of the receiving circuit 26 becomes a pulse train signal. This pulse train signal is converted into a baseband signal by the baseband signal conversion circuit 27 and sent to each data terminal 1 via the interface section 21. Here, since the address for identifying the transmission partner is set in the data transmitted between the data terminals 1, the data terminals 1 with which the addresses match
Only performs a predetermined process based on the data.

The optical signal transmitted from the satellite unit 3 is also received by the terminal unit 2 which has transmitted the optical signal, is sent to the data terminal 1 corresponding to the terminal unit 2, and the correct data is received by the data terminal 1. Is determined. If there is an error, the data terminal 1 newly retransmits the same data as the previous one.

[0022]

As described above, the present invention controls the pulse width of the optical signal so that the satellite unit transmits the optical signal having the same pulse width as the optical signal transmitted from the terminal unit to the terminal unit. Since it is provided in the satellite unit, it is possible to prevent the optical signal with a pulse width greater than the pulse width of the optical signal transmitted from the terminal unit from being transmitted from the transmitting unit of the satellite unit by the gate means, and therefore reflection and sneaking Even if there is such a situation, a normal signal can be transmitted without transmitting an optical signal due to the reflection from the satellite unit.

Further, the terminal unit is provided with a signal conversion function of converting data from the data terminal into a pulse train signal in which high and low level change points are represented by pulses, and inversely converting the pulse train signal into data for the data terminal. When the transmission of the optical signal between the terminal unit and the satellite unit is performed by the optical pulse signal based on the pulse train signal, the pulse width of the optical signal transmitted from the terminal unit from the transmitting unit of the satellite unit of the gate means The function of preventing the transmission of the optical signal having the pulse width as described above can be satisfactorily performed, and therefore, more normal signal transmission can be performed.

[Brief description of drawings]

1A and 1B are block diagrams showing circuit configurations of a terminal unit and a satellite unit.

FIG. 2 is an operation explanatory diagram of the above.

FIG. 3 is a system configuration diagram of a conventional optical space transmission system.

FIG. 4 is an explanatory diagram of a reason why a problem occurs in the above.

FIG. 5 is an explanatory diagram of an example of the above-mentioned problematic phenomenon.

[Explanation of symbols]

 1 Data Terminal 2 Terminal Unit 3 Satellite Unit 22 Pulse Train Signal Conversion Circuit 27 Baseband Signal Conversion Circuit 35 Rise Detection Circuit 36 Pulse Signal Creation Circuit

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[Procedure amendment]

[Submission date] December 28, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

In this type of optical space transmission system, when the satellite unit 3 receives the optical signal from the terminal unit 2 as described above, data is transmitted to the other satellite unit 3 as described above. At the same time as the transmission, it is necessary to transmit the same optical signal to the terminal unit 2 in the area covered by itself. This optical signal is sent from the terminal unit 2
It is exactly the same as the optical signal sent to the light unit 3.
No need, same as data transmitted from data terminal 1
If you can get the contents of the terminal unit 2
Yes. In other words, this is to enable data transmission between the terminal units 2 within the area covered by one satellite unit 3.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

[0010]

According to the present invention, in order to achieve the above object, each data terminal installed in the same space.
In addition, a terminal unit that sends and receives data with optical signals
Satellite units are installed on the construction surface such as the ceiling.
For the pulse width modulation signal transmitted from the data terminal.
Optical signal from one of the terminal units based on
If the satellite unit receives it, the satellite unit
From the light unit to the terminal unit,
Same content as pulse width modulated signal transmitted from data terminal
The optical signal of the
Optical space transmission system for data transmission between data terminals
Sent from the satellite unit to the terminal unit
The signal conversion output based on the generated optical signal is
Match the original pulse width modulated signal transmitted by the
Control the transmission period of the optical signal from the satellite unit.
I am controlling.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

In order to achieve the above object more efficiently, a pulse width modulation signal transmitted from a data terminal is used.
The terminal unit has a signal conversion function of converting the high and low level change points of the pulse train into a pulse train signal indicated by a pulse, and inversely converting the pulse train signal into a pulse width modulation signal .
It is preferable that the optical signal is transmitted between the terminal unit and the satellite unit by an optical pulse signal based on the pulse train signal.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

[0012]

The present invention is not limited to the satellite unit as described above .
Signal based on the optical signal transmitted to the terminal unit from
The conversion output is the original pattern sent from the terminal unit.
Satellite unit to match the pulse width modulation signal
By controlling the transmission period of the optical signal from the satellite unit, even if there is reflection or wraparound, it is possible to prevent the optical signal due to the reflection from being transmitted from the satellite unit and to enable normal signal transmission. is there.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

As shown in FIG. 1A, the terminal unit 2 includes a light emitting element 24 and a light receiving element 25 for transmitting and receiving optical signals to and from the satellite unit 3, and the data terminal 1.
An interface unit 21 for transmitting data to and from
A pulse train signal conversion circuit 22 for converting a high-level to low-level or low-level to high-level change point of data received by the interface unit 21 into a pulse train signal represented by a pulse; A drive circuit 23 for driving the light emitting element 24 with an output, a receiving circuit 26 for filtering and amplifying the received light output by the light receiving element 25, and further waveform shaping, and a pulse train signal output from the receiving circuit 26 Signal format of data of the data terminal 1 (generally, FIG. 2A is shown between the data terminal 1 and the terminal unit 2).
Baseband signals (“1”, “0”) shown in pulse width
And a baseband signal conversion circuit 27 for converting the pulse width modulated signal (shown in the figure ) to perform data transmission).

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

In the satellite unit 3, when the light pulse signal is received by the light receiving element group 32, the received light output is filtered by the receiving circuit 33, amplified and waveform- shaped , and transmitted from the interface section 34 to the transmission line L.
_It is sent to another satellite unit 3 via ₀ . At this time, the rising edge of the output of the receiving circuit 33 is determined by the rising edge detection circuit 3
The pulse signal having a constant pulse width is output from the pulse signal generation circuit 36 at the output of the detection circuit 35.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Name of item to be corrected] 0019

[Correction method] Change

[Correction content]

Therefore, even if there is a reflected signal from the filter cover as in the conventional case, the signal is not further transmitted based on the reflected signal, and the pulse width of the optical signal transmitted from the satellite unit 3 changes. And does not cause oscillation. That is, the rising edge detection circuit 35 and a pulse signal generation circuit 36, satay
Light transmitted from the light unit to the terminal unit
Signal conversion output based on signal from terminal unit
To match the original transmitted pulse width modulated signal,
It controls the transmission period of the optical signal from the tellite unit.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

Optical signals transmitted from the satellite unit 3 and other satellite units 3 are received by the light receiving element 25 of the terminal unit 2, filtered by the receiving circuit 26, amplified, and shaped in waveform.
The output of the receiving circuit 26 becomes a pulse train signal. This pulse train signal is converted into a baseband signal by the baseband signal conversion circuit 27 and sent to each data terminal 1 via the interface section 21. Here, since the address for identifying the transmission partner is set in the data transmitted between the data terminals 1, the data terminals 1 with which the addresses match
Only performs a predetermined process based on the data.

[Procedure Amendment 10]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

[0022]

As described above, the present invention provides a satellite unit.
Based on the optical signal transmitted from the
The signal conversion output was sent from the terminal unit.
To match the original pulse width modulated signal, the satellite unit
By controlling the transmission period of the optical signal from the unit, even if there is reflection or wraparound, the optical signal due to the reflection is not transmitted from the satellite unit, and normal signal transmission can be performed.

[Procedure Amendment 11]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

Also, the pulse width transmitted from the data terminal
Converts high- and low-level change points of the modulation signal into pulse train signals indicated by pulses, and pulse train signals are pulse width modulated
When the terminal unit is provided with a signal conversion function for inversely converting into a signal and the optical signal transmission between the terminal unit and the satellite unit is performed by the optical pulse signal based on the above pulse train signal, the satellite unit outputs a signal.
Signal conversion based on the optical signal transmitted to the terminal unit
The output is the original pulse transmitted from the terminal unit
From the satellite unit to match the width modulated signal
The function of controlling the transmission period of the optical signal can be satisfactorily performed, and therefore, more normal signal transmission can be performed.

[Procedure Amendment 12]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

[Procedure Amendment 13]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location H04L 12/28 8948-5K H04L 11/00 310 B

Claims (2)

[Claims] 1. Each data terminal installed in the same space is provided with a terminal unit for transmitting and receiving data by an optical signal, and a satellite unit is provided on a construction surface such as a ceiling, and an optical signal from any one of the terminal units is provided. In the optical space transmission system for transmitting data between a plurality of data terminals by transmitting the same optical signal as the above optical signal from the satellite unit to the terminal unit at the same time when the satellite unit receives The satellite unit is provided with gate means for regulating the pulse width of the optical signal so that the satellite unit transmits the optical signal having the same pulse width as the optical signal transmitted from the terminal unit to the terminal unit. Optical space transmission system signal transmission method. 2. The terminal unit is provided with a signal conversion function of converting data from the data terminal into a pulse train signal in which high and low level change points are represented by pulses, and converting the pulse train signal back into data for the data terminal. , A signal transmission system for an optical space transmission system, wherein an optical signal is transmitted between the terminal unit and the satellite unit by an optical pulse signal based on the pulse train signal.