JPS62271531A - Pulsification fm signal optical transmission equipment - Google Patents

Abstract

PURPOSE:To perform multiplex transmission to a pulsification FM signal and a low speed signal by using the pulsizing FM signal so as to turn on/off a current flowing to a lighting source. CONSTITUTION:A video signal base band signal inputted to an input terminal 101 is converted into the pulsizing FM signal by a modulator 102 to turn on/off a switch 103. A light emitting diode 106 is driven by a switched current. On the other hand, the current flowing to the switch 103 is modulated by a transistor (TR) 105 according to a data signal inputted from a terminal 104. Then an optical signal from the light emitting diode 106 is sent through an optical fiber and photoelectric-transformed by a photodetector 107. The signal is demultiplexed into a high frequency signal and a low frequency signal by a BPF 109 and an LPF 112 and the high frequency FM signal is demodulated into a video signal by a demodulator 110. Thus, the pulsification FM signal and a low speed signal is subjected to multiplex transmission.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to a transmission device that multiplexes and transmits signals such as low-speed data on a pulsed FM signal.

2. Description of the Related Art Recently, consideration has been given to introducing optical fiber transmission into the subscriber system of 0ATV, which provides video signals to each home. Conventional 0ATVs that use coaxial transmission media transmit several dozen channels of video signals in the VHF band, and each home selects the video signal it wants.

However, it is difficult to directly transmit VHF signals using optical fiber transmission. Therefore, normally a video switcher 203 is placed in the center 201 as shown in FIG.
The image source 2 is transmitted by the channel selection signal 206 from each home 207.
02 and transmitting the selected ICH baseband video signal 206'i to each home is being considered.

However, this system has the disadvantage that when there are many subscribers, the video analog switcher becomes large and expensive, making the system expensive as a whole. Therefore, the method shown in FIG. 9 has been proposed as a method for making the video switcher cheaper. Fourth
Components in the figure that are the same as those in FIG. 3 are numbered the same. A baseband signal 202 from a video source is converted into a pulsed FM signal (for example, 1985 IEICE General Conference 2574) from a video source by a modulator 301. By using a pulse signal digital switcher 303, the cost is reduced.

This system requires an FM modulator 301 to pulse the video signal and a demodulator 307 in each home, but the video switcher can be changed from an analog system to a digital system, and the overall cost can be reduced. In addition, pulsed FM transmission is superior to baseband transmission in terms of transmission characteristics of video signals through optical fibers, such as being less affected by distortion of light emitting elements and having better S/N characteristics. The effects of using FM transmission are significant.

However, this method also has drawbacks. If data (for example, a response to a channel selection signal) is to be sent from the center side, it can be transmitted using a fiber different from the video signal transmission fiber, or by an optical demultiplexer/multiplexer 304 as shown in FIG. Data signal light with wavelength λ input from terminal 305 and wavelength λ
ρ pulsed FM modulated video signal light is transmitted by wavelength multiplexing, and at the home terminal 207, the signal light is separated by an optical demultiplexer 306. Therefore, this system requires a separate fiber for data signal transmission or an optical multiplexer/demultiplexer.

Problems to be Solved by the Invention As explained above, in the conventional optical fiber transmission of pulsed FM signals, when trying to simultaneously transmit low-speed data,
Transmit using another optical fiber with another transmission device, or
Alternatively, it is necessary to transmit by wavelength multiplexing, which has the drawback of making the entire system expensive.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention turns on and off the current flowing through the light emitting source using a pulsed FM signal, and further changes the current flowing through the switch using low-speed data.

Operation The present invention enables multiplex transmission of pulsed FM signals and low-speed signals using the above-described configuration.

Embodiment Next, an embodiment of the present invention will be described with reference to FIG. Input terminal 10
The video baseband signal input to 1 is converted into a pulsed FM signal by the modulator 102, and the switch 103 is turned ON-O.
FF. The light emitting diode 106 is driven by the switched current. On the other hand, the current flowing through this switch is modulated by transistor 105 according to the data signal input from terminal 104. Note that C is the drive current waveform of the light emitting diode. Returning to Figure 1, the explanation will continue. The light is converted into an optical signal by a light emitting diode 106, transmitted through an optical fiber, and then photoelectrically converted by a light receiving element 107.

This signal is amplified at 108 and bandpass filtered at 109
, a low-pass filter 112 separates the signal into a high-pass signal and a low-pass signal. The high frequency FM signal is demodulated into a video signal by a demodulator 110 and output from a terminal 111. On the other hand, the low frequency signal is identified and reproduced at 113 and output from a terminal 114.

In this embodiment, data is used as the low frequency signal, but it is obvious that analog signals such as audio signals can also be used.

As described in detail, according to the present invention, it is possible to multiplex transmit a pulsed FM modulated video signal and a low-speed signal at the same time, and in particular, by combining it with a video signal exchanger, it is possible to transmit an inexpensive 0ATV. It is possible to construct an optical subscriber transmission network.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a pulsed FM signal optical transmission device according to an embodiment of the present invention, FIG. 2 is a diagram showing an embodiment for explaining the operation of the device, and FIGS. 3 and 4 are conventional examples. FIG. 2 is a block diagram of an optical transmission device of FIG. 102...Pulsed FM modulator, 103...
...Switch, 105...Transistor for changing the switching current, 109, 112...
. . . Spectral separation circuit, 110 . . . Pulsed FM demodulation circuit.

Claims (1)

[Claims] a circuit that modulates a video signal into a pulsed FM signal; a switch that turns on and off a current according to the output from the modulator; An optical transmitter is configured with a circuit that drives a light emitting element with a current that is changed by a signal and multiplexes the pulsed FM signal and the low frequency signal,
A pulsed FM signal optical transmission device, characterized in that an optical receiver is constituted by a circuit that separates the multiplexed signal into a low frequency band and a high frequency band, and a circuit that demodulates the pulsed FM signal to the original video signal. .