JPH05227092A - Optical communication equipment - Google Patents

Abstract

PURPOSE:To accurately restore the binary original signal by setting the light intensity of intermittently emitting light emitting element at the constant interval in the constant cycle to the value proportional to the interval of the next intermittent emission of the element. CONSTITUTION:A light signal setting the light intensity of the intermittently emitting light emitting element LD at the constant interval in the constant cycle to the value proportional to the interval to the next intermittent omission of the LD is emitted from a light signal transmission section 11. In a light signal reception section 2, the receiving light element FD receives the light signal to be converted into an electric signal at its output to an integrated circuit 6 and a comparator 7 through an amplifier 3 and BPF 5. The integrated signal outputted from the circuit 6 is kept almost constant, inputted as the reference signal of the comparator 7, keeping the operational point of the comparator 7 almost constant. The output signal of the comparator 7 is integrated by a capacitor 8, and outputted from an output terminal 0. The output signal becomes of the waveform of the pulse width corresponding to the transmission data, accurately recovering the binary original signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication device used for an optical remote control device, an optical fiber cable transmission device, an optical space transmission device or the like.

[0002]

2. Description of the Related Art For example, in an optical remote controller, light is modulated by a pulse position modulation method to perform data transmission, and its configuration is generally as shown in FIG.
That is, in the optical signal transmitter (1), an oscillation signal having a predetermined frequency as shown in FIG. 5A is input to one input end (A) of the AND gate circuit (A1) and the other input end is input. In FIG. 5B, a pulse train signal in which the pulse width is t as shown in FIG. 5B and the time interval is a combination of t and 3t to binarize the data is inputted. The oscillation signal and the pulse train signal are input. The switching transistor (Q1) is turned on / off by a logical product signal of and a light emitting element (L
D) is driven to blink, and the light emitting device (LD) emits light as shown in FIG.
An optical signal as shown in (c) is transmitted.

The oscillation signal has a constant period of 1 / f as shown in FIG. 5 (d) which is an enlarged optical signal, and the pulse train signal has data "0" as shown in FIG. 5 (b). "" Is a combination of a pulse with a pulse width of t and a time interval of t, and data "1" is a combination of information of a pulse with a pulse width of t and a time interval of 3t.
Therefore, the light emitting element (LD) emits light intermittently for a fixed time of t at a constant light intensity of i at a period of 1 / f based on the logical product signal of the oscillation signal and the pulse train signal. The intermittent light emission is continuously repeated at a time interval of either t or 3t, and an optical signal as shown in FIG. 5C is output.

On the other hand, in the optical signal receiving section (2) shown in FIG. 1, the light receiving element (FD) composed of a photodiode or the like receives the optical signal from the optical signal transmitting section (1) and the result is shown in FIG. The electric signal is converted into an electric signal as shown in the figure, the electric signal is amplified by the amplifier (3), the direct current component is removed from the electric signal through the capacitor (4), and the optical signal transmitter (1) is further processed by the band pass filter (5). ), Only the component of the frequency f is passed, and the noise component due to ambient light or the like is removed. Subsequently, an electric signal having a waveform as shown in FIG. 6B output from the bandpass filter (5) is branched into two systems, one of which is directly input to the non-inverting input terminal (+) of the comparator (7). And the other is supplied to an integrating circuit (6) consisting of a resistor (R) and a capacitor (C),
Since the time constant of the integrating circuit (6) is set to be larger than the time t, the integrated signal has a waveform of the average value of the received electric signal as shown in FIG. It is input to the inverting input terminal (-) of (7). In this comparator (7), the electric signal input to the non-inverting input terminal (+) is input to the inverting input terminal (-).
The electric signal is detected by comparing the average value signal input to the reference signal as a reference signal, and the electric signal is further integrated by the capacitor (8) to remove the component of the frequency f as shown in FIG. Converted to a signal. This integrated signal
The waveform is shaped by a hysteresis comparator (9) having a threshold of V _TH at a high level and a threshold at V _TL at a low level shown by a broken line in FIG. 6 (d), and thereafter, by a transistor (Q2) and a pull-up resistor (10). The signal is inverted and a signal having a waveform as shown in FIG. 6E is output from the output terminal (O).

[0005]

However, in the above-mentioned optical communication device, the time constant of the integrating circuit (6) is set to the time t in order to prevent malfunction due to noise due to ambient light or the like.
Since the voltage as the reference signal input to the inverting input terminal (−) of the comparator (7) is set to increase gradually, the data “1” is continuously output in the optical signal. The potential of the integrated signal from the integrator circuit (6) decreases as indicated by E in FIG. 6 (c),
On the contrary, when the data “0” continues, the integration circuit (6)
The electric potential of the integrated signal from is rising as indicated by D in FIG. 6 (c). Therefore, the operating point of the comparator (7) fluctuates according to the arrangement of the data "1" and "0", and the output waveform of the capacitor (8) is affected by the fluctuation.
When the input potential of the inverting input terminal (-) of the comparator (7) is low, it rises quickly and the output waveform of the hysteresis comparator (9) also rises quickly, but the input potential of the inverting input terminal (-) of the comparator (7) is high. Occasionally, the rise is delayed and the inconvenience that the high level V _TH is not reached occurs as shown by F in FIG.
A signal having a waveform with a large pulse width as shown by G in (e) is output. As described above, the pulse width of the output waveform of the optical signal receiving section (2) is likely to change due to the arrangement of the data "1" and "0", so that it becomes impossible to determine the transmission data.

Therefore, according to the present invention, regardless of the arrangement of data "1" and "0", the potential of the reference signal of the detection comparator of the optical signal receiving section is always kept constant and is accurately restored to the binary original signal. It is a technical object to provide such an optical communication device.

[0007]

According to the present invention, as a technical means for achieving the above-mentioned object, an optical communication device is constructed as follows. That is, in the optical signal transmitting unit, two kinds of time intervals are provided, in which the light emitting element is made to intermittently emit light at a predetermined intensity with a predetermined light intensity for a certain time, and then the light emitting element is made to intermittently emit light. Data is transmitted as an optical signal of a binary signal by pulse position modulation, the optical signal is converted into an electric signal in the optical signal receiving unit, and the electric signal is compared with a reference signal obtained by integrating the electric signal with a comparator. In the optical communication device for performing the waveform shaping of a signal obtained by integrating the detected signal and restoring the binary original signal, the optical signal transmitting unit intermittently controls the light emitting element at a constant period for a constant time. It is characterized in that the intensity of the light to be emitted is set to a value proportional to the time interval until the light emitting element emits light intermittently next.

[0008]

From the optical signal transmitter, for example, when the data "0" is set to the light intensity i and the duration time when the light intensity is zero is set to t, the data "1" is set to the light intensity 3i. In addition, since the optical signal in which the duration of the light intensity is zero is set to 3t is transmitted, the signal obtained by integrating the electrical signal obtained by photoelectrically converting the optical signal in the optical signal receiving unit has the light intensity of zero. In the case of the data “0” whose duration is t as short as the light intensity, i is correspondingly small and does not rise above a certain value. On the other hand, the data “0” where the light intensity is zero has a long duration of 3t. In the case of 1 ″, the light intensity is accordingly large as 3i, and therefore does not fall below a certain value. That is, since the integrated signal of the electric signal, that is, the reference signal of the detection comparator is held substantially constant, the operating point of the comparator becomes substantially constant, and the pulse width of the output waveform corresponds to the transmission data, and is transmitted. It is possible to accurately restore the original binary signal.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a block configuration of an embodiment of the present invention. In the figure, the same or equivalent parts to those in FIG. 4 are designated by the same reference numerals, except that the optical signal transmitter (11) is different. , An AND gate circuit (A) which connects another switching transistor (Q3) in parallel to the existing switching transistor (Q1) and controls switching of this switching transistor (Q3).
3) is provided, and the output signal of the existing AND gate circuit (A1) is input to one input end of this AND gate circuit (A3), and data is input to the other input end as shown in FIG. 2 (d). Corresponding to "0" and "1", it is a low level of "0" when the data is "0" and "1" when the data is "1".
It is only that a structure for inputting the high level signal of is attached.

Next, the operation of the above embodiment will be described with reference to the optical signal transmitter (1
It will be described in detail with reference to FIG. 2 showing a timing chart of 1) and FIG. 3 showing a timing chart of the optical signal receiving section (2). 2 (a) and 2 (b) are waveforms of input signals at both input terminals (A) and (B) of the AND gate circuit (A1), respectively. FIG. 2 (c) is the AND gate circuit (A1).
The respective waveforms of the output signals of the above are shown, and FIG. 6D shows the other input terminal (C) of the AND gate circuit (A2) as described above.
The waveform of the input signal to is shown. Therefore, the switching transistor (Q1) is switching-controlled by the output signal of the AND gate circuit (A1) shown in FIG.
Switching control is performed by a signal obtained by taking the logical product of the signal of (c) and the signal of (d) in the figure in the angel gate circuit (A2). Therefore, from the light emitting element (LD),
As shown in (e), when the data is "0", an optical signal in which the light intensity repeats "0" and "i" at a constant period 1 / f corresponding to the switching operation of the switching transistor (Q1) is time. When the data is "1", the light intensity is "0" and "3i" corresponding to each switching operation of the switching transistor (Q1) and the switching transistor (Q2) when the data is "1". An optical signal that repeats at / f is output for the time t. That is, from the optical signal transmitter (11), the intensity of light that causes the light emitting element (LD) to intermittently emit light at a constant period (1 / f) for a constant time (t) is changed to the light emitting element (LD). An optical signal set to a value i or 3i proportional to the time interval (t) or (3t) until intermittent light emission is output.

Then, in the optical signal receiving section (2), the light receiving element (FD) receives the optical signal and converts it into an electric signal as shown in FIG. 3 (a), and the electric signal is amplified by the amplifier (3). After amplification, the DC component was removed by the capacitor (4), and the signal that passed through the bandpass filter (5) is shown in FIG.
The waveform is as shown in (b), and this electric signal is input to the non-inverting input terminal (+) of the comparator (7). On the other hand, the signal obtained by integrating this electric signal by the integrating circuit (6) is
In the case of data "0" where the duration of time when the light intensity is zero is as short as t, the light intensity does not rise above a certain value because the light intensity is correspondingly small as i, while the duration time when the light intensity is zero. When the data is 3t, which is as long as 3t, the light intensity is also 3 accordingly.
Since i is large, it does not fall below a certain value. That is, the integrated signal output from the integrator circuit (6) is held at a substantially constant value as shown in FIG. 3 (c), and this integrated signal is applied to the inverting input terminal (-) as the reference signal of the comparator (7). Since it is input, the operating point of the comparator (7) becomes substantially constant, and the signal obtained by integrating the output signal of the comparator (7) with the capacitor (8) has a waveform as shown in FIG. The output signal from (O) is
As shown in, the waveform has a pulse width corresponding to the transmission data and can be accurately restored to the binary original signal.

[0012]

As described above, according to the optical communication device of the present invention, the intensity of the light that causes the optical signal transmitting section to intermittently emit the light emitting element for a certain period of time is changed to the light emitting element. Since it is configured to be set to a value that is proportional to the time interval until the light is emitted, the optical signal receiving unit can hold the integrated signal of the received light electric signal, that is, the reference signal of the detection comparator, substantially constant regardless of the received data. Therefore, the operating point of the comparator becomes almost constant, the pulse width of the output waveform corresponds to the transmission data, and the binary original signal can be accurately restored.

[Brief description of drawings]

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

FIG. 2 is a timing chart of signals of respective parts of the optical signal transmitting section.

FIG. 3 is a timing chart of signals of respective parts of the optical signal receiving section.

FIG. 4 is a block diagram of a conventional optical communication device.

FIG. 5 is a timing chart of signals of the respective units of the optical signal transmission unit.

FIG. 6 is a timing chart of signals of each unit of the optical signal receiving unit.

[Explanation of symbols]

 2 Optical signal receiver 6 Integration circuit 7 Detection comparator LD Light emitting element 11 Optical signal transmitter

Claims (1)

[Claims] 1. An optical signal transmitter, wherein a light emitting element is made to intermittently emit light at a predetermined period and a predetermined light intensity for a certain time, and then a time interval until the light emitting element is made to intermittently emit light is set. By providing two types of data, data is transmitted as an optical signal of a binary signal by pulse position modulation, the optical signal receiving unit converts the optical signal into an electric signal, and the electric signal is integrated with a reference signal and a comparator. The waveform is shaped by integrating the detected signal and detected.
In the optical communication device that restores the original signal of the value, the optical signal transmitting unit causes the light emitting element to emit light intermittently for a certain period of time and then causes the light emitting element to emit light intermittently. An optical communication device having a configuration that is set to a value proportional to the time interval up to.