JPS58124340A - Transmission module circuit - Google Patents

Abstract

PURPOSE:To enable a plastic system optical fiber to be applied, by providing a TTL gate circuit receiving an input and a transistor (TR) to which the output of the gate circuit is connected, in a transmission module of a visual digital link. CONSTITUTION:In the transmission module of the visual light digital link having DC 1p Mb/s of transmission speed and a TTL level of the input signal level, the TTL gate circuit 12 and the TR13 to the base of which the output of the circuit 12 is given are provided, a current limiting resistor 14 and a visual light emitting diode are connected in series between the collector of the TR13 and a power supply VCC and the emitter is grounded. Thus, the driving current of the diode 11 is taken larger and the selection of the current value is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmitting module circuit, and more particularly to a transmitting module circuit for visible light digital link using plastic optical fiber.

There is something to be seen in the development of so-called optical communication technology, which is used as a carrier wave for optical sound communication. In particular, the success of low-14 transmission of glass-based optical fiber as an optical transmission line;
The fact that continuous room-temperature operation of semiconductor lasers as a light source for optical communications has become possible has accelerated the overall development of semiconductor lasers.

The Hikari 1iT7, which was made entirely of glass-based optical fibers, has lower loss compared to conventional electrical type JIN communications, which allows for longer relay intervals, and because it has a wide band, the transmission speed is high and a large amount of information can be transmitted. It has all the features of.

In addition, compared to coaxial cables, it is lighter, has a smaller sandalwood diameter, is completely immune to the effects of electromagnetic induction, and has a small amount of noise.
<It has many advantages, such as being highly confidential.

Because of these advantages, optical communications based entirely on glass-based optical fibers are expected to be effective mainly in the field of long-distance transmission.

However, optical communications, which are all based on conventional glass-based optical fibers, are not without problems. For example, glass optical fibers themselves are expensive, and glass optical fibers are generally extremely thin with a core diameter of about 150 microns, and high precision is required for fiber-to-fiber connections or fiber-to-module connections. When connecting, a special centering machine is usually required.

Furthermore, in the case of applications for short-distance information transmission, glass-based optical fibers have low bending resistance, making short-distance wiring construction difficult. Furthermore, in optical communication using glass-based optical fibers, the low-loss wavelength range is mainly in the infrared range (usually 0.85 to 1.6 micron wavelength range) and is invisible to the naked eye, so the light during construction on site There is also the problem that a special optical axis alignment machine that uses visible light and sound must be used for axis alignment and the like.

As a result of intensive research in order to solve all the problems mentioned above in conventional glass-based optical fiber communications, the inventors of the present invention have developed a transmitter/receiver module A/all that is compatible with plastic fiber optic fibers, and have developed visible light The data link for the cow was completed and the ``visible light data link'' (patent application 1986) was
-68954). In the L application, proposals were made for both a digital transmission method and an analog transmission method, but the gist of the visible light data link using the digital transmission method, which is directly related to the present invention, is the [Transmission module] , plastic optical fiber.

A visible light data link consisting of a connector and a receiving module, which uses a plastic optical fiber transmitting module with a manual power level of -26 to -12 aBm, a receiving module with a minimum receiving level of -4-QdBm or more, and a transmitting/receiving module. The transmission speed is Do~
A data link for visible light using a digital transmission method, which is fully characterized as lQMb/S. "It is in.

The entire object of the present invention is to provide a transmitter module circuit suitable for use in a visible light data link using the digital transmission method described above.

The gist of the present invention is that in a transmission module for a visible light digital link in which the transmission speed is DO to IQMb/s and the input signal level is TTL level, a TTL gate circuit that receives the input and an output of the TTL gate circuit are provided. A transistor is connected to the base terminal, and a current limiting resistor and a visible light emitting diode are connected in series from a power source to one collector terminal of the transistor, and one emitter terminal of the transistor is grounded. This is achieved by a transmitter module circuit that

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 shows a complete outline of a visible light data link 7 of a digital transmission system on which the present invention is based. In the figure, 1 is an input electrical signal, 2 is a transmission module, 3, 3 is a connector, 1 is a plastin-based optical fiber (hereinafter simply referred to as "optical 7I, 8"), b is a reception module, and 6 is a This is an output electrical signal.The input electrical signal 1 is normally input through a coaxial cable.The transmitting module 2 converts the input electrical signal into an optical pulse code and sends it out to the optical fiber key connected through the connector 3. The optical signal transmitted through the optical fiber 4 is converted into an electrical signal by the receiving module 5 connected through the connector 3 and output.

It should be noted that the light emitting diode to be included in the transmitting module 2 is selected to have a center wavelength in the visible range, that is, 380 to 780 nm. This is mainly because the optical fiber used has excellent transparency in the visible range, and also because it allows direct confirmation of the presence or absence of signals during transmission wiring work, which improves work efficiency. However, at present, the external efficiency of light emitting diodes in the visible region is often inferior to that in the infrared region, so care must be taken when selecting elements. A light-emitting diode with good external efficiency in the visible region has a center wavelength of 660 nm and a spectral half-width of 3.
All gallium-aluminum-arsenic light emitting diodes having a wavelength of 5 nm and a response speed of 5 nS can be used, but are not limited thereto.

FIG. 2 shows the entire transmitting module circuit according to an embodiment of the present invention. In the figure, 11 is a light emitting diode;
2 is a TTL gate circuit, 13 is a transistor, and 14 is a lightning current limiting resistor. Further, vaa is the power supply, and +5■ is usually selected, but it is not limited to this.

In the circuit of this embodiment, all of the light emitting diodes 11 are turned on and off using a TTL level electric signal and converted into an optical pulse signal. However, with a simple TTL gate circuit, there is a limit to the current capacity that can flow and sufficient optical power cannot be obtained. Therefore, by connecting the output of the T'I' L gate circuit 12 to the base terminal of the transistor 13, light emission The drive current of the diode 11 is designed to be large (20 mA to IA at a large value). In addition, in order to make the circuit compact, the TTL gate circuit 1
2 and transistor 13 are preferably configured in the same IC.

When the light emitting diode 11 is fully emitted, the current value to be passed through the light emitting diode is such that the light emitting time is 10.0 to maintain a luminous efficiency of 90% or more when the light emitting diode is fully emitted.
It is desirable to select a current value that is 00 hours or more. Typically, this current value is between 20 and 100 mA. In order to obtain the current value selected in this way, the current limiting resistor (
R) Determine the value of l4.

The degree of response in the circuit configured as described above is 2°n8
It was below. Note that it is important to efficiently input the power converted into an optical signal into the optical fiber 4.
To achieve this, it is necessary to bring the end faces of the light emitting diode 11 and the optical fiber 4 as close as possible, or to consider lens effects so that the light emission intensity of the light emitting diode 11 has full directivity, and to sufficiently process the end face of the optical fiber. Being present is effective. If these are implemented,
The input optical power level to an optical fiber with a diameter of 1 is -2
0 to -5 dBm was achieved.

In addition, in the above embodiment circuit, all the light emitting diodes are
Although only one light emitting diode is used in the example shown above, it is also possible to combine a plurality of light emitting diodes and transmit the same signal to several locations.

The optical fiber is made of high-purity methacrylic resin (
A so-called total reflection type optical fiber having a double structure in which a core of poly(methyl methacrylate) is surrounded by a thin sheath of transparent fluorine-based resin is suitable, but it is not limited thereto.

As described below, according to the present invention, the transmission speed is
l OMb/S, and in a visible light digital link transmission module whose input signal level is TTL level, it is connected to the TTL'r'-to circuit that receives all the inputs and all the output base terminals of the TTL gate circuit. A current limiting resistor and a visible light emitting diode are connected in series from a power source to one terminal of the collector of the transistor, and one terminal of the emitter of the transistor is all grounded. This has the remarkable effect of realizing a transmitter module circuit suitable for use in optical digital links.

[Brief explanation of the drawing]

Figure 1 shows an overview of the visible light data link on which the present invention is based.
FIG. 2 is a diagram showing a transmitting module circuit according to an embodiment of the present invention. 1: Input electrical signal, 2: Transmission module, 3゜3': Connector, 4: Optical fiber, 5: Receiving module, 6
: Output signal, 7: Visible light data link, 11: Light emitting diode, 12: 'I'TL gate circuit, 13 Nidoran sister, 14: Current limiting resistor. Patent applicant Mitsubishi Rayon Co., Ltd. Representative Patent attorney Masatoshi Isomura

Claims (1)

[Claims] Transmission module, plastic optical fiber. A visible light digital link transmitting module consisting of a connector and a receiving module, and having a transmission rate of D O-10 Mb/S% and an input signal level of TTL level, includes a TTL gate circuit that receives all the inputs, and a TTL gate circuit that receives the output of the TTL gate circuit. A transistor connected to the base terminal is provided, and one collector terminal of the transistor is connected in series with a current limiting resistor and a visible light emitting diode from a power source, and one emitter terminal of the transistor is grounded. Transmission module circuit.