JPH09205400A - Optical signal transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical signal transmitter which is capable of transmitting the signal of a frequency band exceeding an upper limit frequency by performing frequency conversion for an input signal at the time of transmission. SOLUTION: As to an optical signal transmitter modulating the optical intensity by an electric signal and performing transmission, the electric signal inputted in an input terminal 1 is converted into the signal of a low frequency band which is possible to perform an intensity modulation for a light emitting diode by a local oscillation circuit 12, a multiplication circuit 13 and a band amplifier circuit 14 on a transmission side, optical intensity is modulated by an electric/ optic conversion circuit 3, the signal is transmitted as an optical signal, the optical signal received by an optic/electric conversion circuit L1 is demodulated into the electric signal on a reception side, and the signal is converted into a frequency band to be outputted to an output terminal 6 by a local oscillation circuit 16, a multiplication circuit 17 and a band amplifier circuit 18.

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 device using a light emitting diode, and more particularly to an optical signal transmission device capable of transmitting a signal in a frequency band exceeding an upper limit frequency capable of intensity-modulating the light emitting diode. Regarding

[0002]

2. Description of the Related Art A conventional optical signal transmission device will be described with reference to FIG. FIG. 2 is a configuration block diagram of a conventional optical signal transmission device. An optical signal transmission device generally modulates the intensity of light with an electric signal such as a video signal, an audio signal, a digital signal, or a high frequency signal modulated with these signals, and transmits the light through space or an optical fiber. In addition, a transmitter and a receiver are used as a pair.

As shown in FIG. 2, a transmitter of a conventional optical signal transmission apparatus is composed of an input terminal 1, a band amplification section 2 and an electro-optical conversion circuit 3, and a receiver is , An optical-electrical conversion circuit 4, a band amplification unit 5, and an output terminal 6.

Next, each part of the conventional optical signal transmission device will be described. The band amplification units 2 and 5 selectively amplify signals in a specific frequency band. The band amplification units 2 and 5 are
It is composed of a tuning amplifier circuit or a circuit combining a bandpass filter and an amplifier circuit for amplifying a wider frequency band than the bandpass filter. The input of the band amplification unit 2 is an input terminal 1 and the output is an electro-optical conversion. The band amplification unit 5 has its input connected to the opto-electric conversion circuit 4 and its output connected to the output terminal 6, respectively.

The electric-optical conversion circuit 3 is composed of a light emitting diode and a drive unit for the light emitting diode. The drive unit changes the current of the light emitting diode by an electric signal to modulate the intensity of light emitted by the light emitting diode. Then
It is output as an optical signal.

The photoelectric conversion circuit 4 is composed of a photodiode and a transimpedance amplifier which amplifies a current signal output from the photodiode and converts it into a voltage signal. The photodiode receives (receives) light. The intensity of an optical signal is converted into an electrical signal and output.

Next, the operation of the conventional optical signal transmission device is shown in FIG.
It will be explained in detail using. First, the operation of the transmitter of the conventional optical signal transmission device will be described. An electric signal such as a video signal, an audio signal, a digital signal, or a high-frequency signal modulated by these signals is passed through the input terminal 1 to the band amplification unit 2
Input to the band amplification unit 2, the band amplification unit 2 selectively amplifies a signal in a frequency band for transmission and outputs the signal to the electro-optical conversion circuit 3.
The electro-optical conversion circuit 3 modulates the intensity of the light emitted by the light emitting diode with the signal output from the band amplification unit 2 and outputs it as an optical signal, which is transmitted to the receiver side via space or an optical fiber.

Next, the operation of the receiver of the conventional optical signal transmission device will be described. The opto-electric conversion circuit 4 receives the optical signal output by the electro-optical conversion circuit 3 via space or an optical fiber and demodulates it into an electric signal. The band amplification unit 5 is
Of the electric signals demodulated by the electric conversion circuit 4, the band amplification unit 2
A signal in the same frequency band as is selectively amplified and output to the output terminal 6.

[0009]

However, in the above-mentioned conventional optical signal transmission device, there is an upper limit to the frequency at which the light emitted by the light emitting diode can be intensity-modulated by the electric signal in the electric-optical conversion circuit 3. Therefore, there is a problem in that it is not possible to modulate and transmit a signal having a frequency higher than the upper limit frequency, and the transmittable frequency band is limited.

The present invention has been made in view of the above circumstances. At the time of transmission, the electric signal in the frequency band for transmission is converted into a frequency band in which the intensity of the light emitting diode can be modulated, so that the upper limit frequency is exceeded. An object of the present invention is to provide an optical signal transmission device capable of transmitting a signal in a high frequency band.

Another object of the present invention is to use another device by changing the frequency of the reference oscillation signal of the local oscillation circuit on the reception side and the frequency band of the band amplification section on the output side of the multiplication circuit. Another object of the present invention is to provide an optical signal transmission device capable of changing the frequency band of a signal input to a transmitter for transmission and the frequency band of a signal output by a receiver.

[0012]

The invention according to claim 1 for solving the above-mentioned problems of the prior art is an electric signal for modulating the intensity of light emitted from a light emitting diode by an electric signal and transmitting the electric signal as an optical signal. In an optical signal transmission device comprising a transmitter having an optical conversion circuit and a receiver having an optical-electrical conversion circuit for receiving the optical signal and demodulating it into an electric signal, the transmitter has a specific frequency of an input signal. A first band amplification unit that selects and amplifies a band signal, a transmission side local oscillation circuit that generates a reference oscillation signal, an output signal from the first band amplification unit, and a transmission side local oscillation circuit. A transmission side multiplication circuit that multiplies a reference oscillation signal, and a signal of a difference component between the output signal from the first band amplification unit and the reference oscillation signal among frequency components of the signal output from the transmission side multiplication circuit. To amplify A second band amplification unit is provided, and a third band signal which selects the signal of the same frequency band as the second band amplification unit from the signals output from the opto-electric conversion circuit and amplifies the signal to the receiver is provided. A band amplification unit, a reception side local oscillation circuit that generates a reference oscillation signal, and a reception side multiplication circuit that multiplies the signal output from the third band amplification unit by the reference oscillation signal from the reception side local oscillation circuit. And a fourth band amplification unit for selecting and amplifying a signal in a specific frequency band among the frequency components of the signal output from the reception side multiplication circuit, wherein the input signal is an electrical signal. Even a signal in a frequency band exceeding the upper limit frequency capable of intensity-modulating the light emitting diode of the optical conversion circuit is converted into a signal in a low frequency band by the transmission side multiplication circuit, and amplified by the second band amplification unit. Input to the electrical-optical conversion circuit Because, it is possible to enable transmission.

[0013]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration block diagram of an optical signal transmission device (this device) according to an embodiment of the present invention. The optical signal transmission device (present device) according to the embodiment of the present invention is
As with conventional optical signal transmission equipment, video and audio signals,
The digital signal or an electric signal such as a high frequency signal modulated by these signals is transmitted through space or an optical fiber.

As shown in FIG. 1, the present apparatus performs frequency conversion by the local oscillation circuits 12 and 16 and the multiplication circuits 13 and 17 to change the intensity of light emitted by the light emitting diode in the electro-optical conversion circuit 3. It is a device that can transmit even an electric signal in a frequency band exceeding the upper limit frequency that can be modulated.

As shown in FIG. 1, the transmitter of this apparatus includes an input terminal 1, band pass filters 21 and 23,
The amplifying circuits 22 and 24, the local oscillating circuit 12, the multiplying circuit 13, and the electro-optical converting circuit 3 are included, and the receiver includes an opto-electric converting circuit 4 and a bandpass filter 2.
5, 27, amplifier circuits 26 and 28, and local oscillator circuit 16
And a multiplication circuit 17 and an output terminal 6.

Here, the combination of the bandpass filter 21 and the amplification circuit 22 (band amplification section 11) is the first band amplification section of claim 1 in which the bandpass filter 23 and the amplification circuit 24 are combined. Things (band amplification unit 14)
Is a combination of the band pass filter 25 and the amplification circuit 26 in the second band amplification section (band amplification section 15) is a combination of the band pass filter 27 and the amplification circuit 28 in the third band amplification section The (band amplification unit 18) corresponds to the fourth band amplification unit, respectively.

Next, each part of the transmitter of the optical signal transmission device shown in FIG. 1 will be described. The band pass filter 21 selects and outputs a signal in a specific frequency band from the input signals from the input terminal 1, and reduces signals in other frequency bands. The amplifier 22 amplifies the signal output by the bandpass filter 21. Local oscillator 12
Outputs a reference oscillation signal of a specific frequency used for frequency conversion of the signal output by the amplifier 22.

The multiplication circuit 13 mixes the reference oscillation signal output from the local oscillation circuit 12 and the output signal of the amplification circuit 22 and includes frequency components such as a sum component and a difference component of both signals in addition to the input signal. It outputs a signal.

The bandpass filter 23 is a multiplier circuit 13.
Among the output signals from, it is possible to modulate the intensity of the light emitted by the light emitting diode, select and output the signal in the frequency band corresponding to the above difference component, and reduce the signal in other frequency bands. is there.

The amplifier circuit 24 is a bandpass filter 23.
The output signal of is amplified. Electric-optical conversion circuit 3
Is an output signal of the amplifier circuit 24, which modulates the intensity of the light emitted from the light emitting diode and transmits it as an optical signal to the receiver via space or an optical fiber.

Next, each part of the receiver of the optical signal transmission device shown in FIG. 1 will be described. The optical-electrical conversion circuit 4 receives the optical signal transmitted from the transmission side, demodulates it, and outputs an electrical signal. The bandpass filter 25 selects and outputs a signal in the same frequency band as the bandpass filter 23, and reduces other signals.

The amplifier circuit 26 includes a bandpass filter 25.
The output signal of is amplified. Local oscillator 16
Is to output a reference oscillation signal of a specific frequency for conversion into the frequency band output to the output terminal 6.

The multiplication circuit 17 mixes the signal output from the amplifier circuit 26 with the signal output from the local oscillation circuit 16,
In addition to the input signal, a signal including frequency components such as a sum component and a difference component of both signals is output.

The bandpass filter 27 includes a multiplication circuit 17
The signal of the frequency band to be output to the output terminal 6 is selected from the output signals of the above and output, and the signals of the other frequency bands are reduced. The amplifier circuit 28 amplifies the output signal of the multiplication circuit 17 so as to have a signal level suitable for the input of the device connected to the output terminal 6.

Next, regarding the transmission / reception operation of the optical signal transmission device shown in FIG.
Video carrier frequency fv = 205.25 MHz, audio carrier frequency fa = 209.75 MHz, frequency band 204
~ 210 MHz signal, 12 channels of terrestrial television broadcasting, video carrier frequency fv = 217.25 MHz,
A specific description will be given by taking as an example the case of transmitting a signal having an audio carrier frequency fa = 221.75 MHz and a frequency band of 216 to 222 MHz.

First, the operation of the transmitter of the optical signal transmission device of FIG. 1 will be described. The bandpass filter 21 has an input terminal 1
A signal in the frequency band to be transmitted, for example, a signal in the frequency band of f1 = 204 to 222 MHz is selected from the signals input via the and is output to the amplifier circuit 22. Amplifier circuit 2
2 amplifies the signal output from the bandpass filter 21 and inputs it to the multiplication circuit 13.

The multiplication circuit 13 mixes the reference oscillation signal output from the local oscillation circuit 12, for example f2 = 244 MHz, with the output signal from the amplification circuit 22, and in addition to f1 and f2, the sum component f1 + f2 = 448- A signal including a frequency component such as 466 MHz or a difference component f2-f1 = 22 to 40 MHz is output to the bandpass filter 23.

The bandpass filter 23 includes a multiplication circuit 13
Difference signal f2-f1 = a signal in a frequency band in which the intensity of light emitted from the light emitting diode can be modulated from the output signal of
A signal in the frequency band of 22 to 40 MHz is selected and output to the amplifier circuit 24. The amplifier circuit 24 amplifies the output signal of the bandpass filter 23 and inputs it to the electro-optical conversion circuit 3. The electro-optical conversion circuit 3 modulates the intensity of the light emitted from the light emitting diode with the output signal of the amplifier circuit 24 and transmits it as an optical signal to the receiver via space or an optical fiber.

Next, the operation of the receiver of the optical signal transmission device of FIG. 1 will be described. The optical-electrical conversion circuit 4 receives the optical signal transmitted from the transmission side, and inputs the demodulated electrical signal to the bandpass filter 25. The bandpass filter 25 is
The frequency band selected by the bandpass filter 23, f3 =
The signal of 22 to 40 MHz is selected and output to the amplifier circuit 26. The amplification circuit 26 amplifies the output of the bandpass filter 25 and inputs it to the multiplication circuit 17.

The multiplication circuit 17 outputs the signal output from the amplification circuit 26 and the local oscillation circuit 16 outputs, for example, f4 = 2.
A reference oscillation signal of 44 MHz is mixed, and in addition to f3 and f4, the sum component is f3 + f4 = 266 to 284 MHz.
Alternatively, a signal including a frequency component such as f4−f3 = 204 to 222 MHz which is a difference component is output to the bandpass filter 27.

The bandpass filter 27 includes a multiplication circuit 17
A signal in the frequency band of the difference component 204 to 222 MHz, which is a signal in the frequency band to be output to the output terminal 6, is selected from the signals output from the output terminal 6 and output to the amplifier circuit 28. Amplifier circuit 2
8 outputs the output signal of the bandpass filter 27 to the output terminal 6
Is amplified to a signal level suitable for the input of a device connected to, for example, a television receiver, and output to the output terminal 6. Thus, among the signals input to the transmitter, 204 to 222
The signal of the frequency band of MHz is the same as the output terminal 6 204
It can be output as a signal in the frequency band of up to 222 MHz.

According to the optical signal transmission device of the embodiment of the present invention, when the intensity of light is modulated by the transmitter, frequency conversion is performed, so that the electrical signal to be transmitted can be modulated with low intensity. Since the signal is converted into the signal in the frequency band, there is an effect that the signal input to the input terminal 1 can be transmitted even if the signal is in the frequency band exceeding the upper limit frequency at which the light emitting diode can be intensity-modulated.

Further, since the electric signal received by the receiver is demodulated and the frequency of the electric signal obtained by demodulation is converted again, the signal input to the transmitter and transmitted without attaching another device to the outside. There is an effect that the frequency band of and the frequency band of the signal output by the receiver can be changed.

[0034]

According to the first aspect of the present invention, the output signal obtained by selectively amplifying the signal in the specific frequency band of the input signal in the first band amplification section and the reference oscillation signal from the transmission side local oscillation circuit are provided. The output side signal is multiplied by the transmission side multiplication circuit, and the output signal of the difference component is selectively amplified by the second band amplification section and transmitted by the electro-optical conversion circuit. Among them, the signal of the same frequency band as the second band amplification unit is selectively amplified by the third band amplification unit, and the output signal thereof and the reference oscillation signal from the reception side local oscillation circuit are multiplied by the reception side multiplication circuit, Since the output signal is an optical signal transmission device that selectively amplifies and outputs it in the fourth band amplifying unit, a frequency band in which the input signal exceeds the upper limit frequency capable of intensity-modulating the light emitting diode of the electro-optical conversion circuit. Even if it is a signal of Into a lower frequency band of the signal,
Since it is amplified by the second band amplification unit and input to the electro-optical conversion circuit, there is an effect that transmission is possible.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an optical signal transmission device according to an embodiment of the present invention.

FIG. 2 is a configuration block diagram of a conventional optical signal transmission device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Input terminal, 2,5,11,14,15,18 ... Band amplification part, 3 ... Electric-optical conversion circuit, 4 ... Optical-electric conversion circuit, 6 ... Output terminal, 12,16 ... Local oscillation circuit, 13, 17 ... Multiplication circuit, 21, 23, 25, 2
7 ... band pass filter, 22, 24, 26, 28 ...
Amplifier circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04B 10/28 10/26 10/14

Claims (1)

[Claims] 1. An electric device for modulating the intensity of light emitted from a light emitting diode by an electric signal and transmitting the light as an optical signal.
In an optical signal transmission device comprising a transmitter having an optical conversion circuit and a receiver having an optical-electrical conversion circuit for receiving the optical signal and demodulating it into an electric signal, the transmitter has a specific frequency of an input signal. A first band amplification unit that selects and amplifies a band signal, a transmission side local oscillation circuit that generates a reference oscillation signal, an output from the first band amplification unit, and a reference from the transmission side local oscillation circuit A transmission side multiplication circuit that multiplies an oscillation signal, and a frequency component of a signal output from the transmission side multiplication circuit, that is, a difference component signal between the output signal from the first band amplification unit and the reference oscillation signal. A second band amplification unit that selects and amplifies is provided, and a signal in the same frequency band as the second band amplification unit is selected from among the signals output from the opto-electric conversion circuit to the receiver. A third band amplification section that amplifies A reception side local oscillation circuit for generating a signal, a reception side multiplication circuit for multiplying the signal output from the third band amplification section and a reference oscillation signal from the reception side local oscillation circuit, and the reception side multiplication circuit An optical signal transmission device comprising: a fourth band amplification unit that selects and amplifies a signal in a specific frequency band from the frequency components of the signal output from the device.