JPS58209241A - Multichannel optical transmitter - Google Patents

Abstract

PURPOSE:To reduce a flow-in current, by bypassing a current flowing in common with light emitting diodes connected in series to a bypass circuit in response to a data at each light emitting diode so as to switch on and off the optical output. CONSTITUTION:Lots of light emitting diodes 5-8 are connected in series and connected to a constant current power supply 9 outputting a constant current I0 at all times. The light emitting diodes 5-8 are connected in parallel with bypass current switching circuits 10-13, respectively. These bypass current switching circuits 10-13 are driven with switch driving circuit 14-17 outputting each drive signal corresponding to data input signals 1-4, respectively. Thus, since the current flows to all the light emitting diodes 5-8 in common, the required current value is less and the miniaturization of the power supply is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an improvement in an optical transmitter for transmitting multi-channel optical data signals.

[Description of prior art]

Conventionally, this type of device has been constructed as a multi-channel optical transmitter by connecting optical transmitters for single channel transmission in parallel to create multiple channels. An example of the configuration of this conventional basic optical transmitter for single channel transmission is shown in FIG. transistor 3. When the transistor 3 is turned on, a current flows through the light emitting diode 2, so that an optical signal is output. A resistor 4 is used to limit the drive current to a predetermined value.

Since the conventional multi-channel optical transmitter is constructed by connecting optical transmitters for skew-channel transmission in parallel as shown in FIG. 1, it has the following drawbacks.

ψ Normally 50mA to 100mA for light emitting tie auto
, the current flows and turns off, but if the saw is made into a multi-channel saw, a current equal to this current multiplied by the number of channels will be required, so it is necessary to provide a commensurately large power supply, and The power consumed in the circuit increases and heat generation increases.

■ The inflow current changes greatly between when the logic value of the input signal is 01 for all channels and when the logic value of the input signal is 1-1 for all channels.As a result, the output voltage of the power supply It often fluctuates and does not adversely affect other circuits through the power supply circuit.

[Object 1 of the invention] The present invention solves the above-mentioned drawbacks, (gradient inflow current is small, its fluctuation is small, (bi) has low dissipation force, (cl, r6 crystal analogy) The purpose is to provide a multi-channel system capable of data transmission.

[Key points of the invention]

The present invention is characterized in that the light output is turned on and off by connecting light emitting diodes in series and bypassing the common current flowing therein to a bypass circuit according to data for each light emitting diode. shall be.

[Explanation based on examples]

A detailed explanation will be given below using the drawings of the embodiment.

FIG. 2 is a circuit diagram of a device according to an embodiment of the present invention. Second
In the figure, a large number (four in this example) of light emitting diodes 5 to 8 are connected in series and connected to a constant current power source 9 that always outputs a constant current fi+o. In addition, bypass current switching circuits 10 to 1 are connected to the light emitting diodes 5 to 8, respectively.
3 are connected in parallel. These bypass current switching circuits 10 to 13 receive a data input signal (
They are driven by switch drive circuits 14 to 17 that respectively output drive signals corresponding to 1) to (4).

FIGS. 3 to 5 show examples of the structure of the bypass current switching circuit. Figure 3 shows an example of a configuration using relays.
'J, data signal is contact signal or open-IL
In the case of the lid signal, the current flowing to the L relay 18 is turned on and off in the state of the signal, and the current flowing through the L relay 18 is turned on and off, and
Relay switch 19 is also off. This circuit is suitable for low-speed data signal transmission.

FIG. 1 shows the third and first bypass current switching circuits iM
Lkoda・fauto2 (This is the addition of l.This τ
1. A light emitting diode with a voltage of about 1.5 to 2.0 volts.
bad f' t■ This is included to prevent IjJj from changing greatly between the on state and the off state. In FIG. 3, when the relay switch I9 is on, the voltage across the light emitting diode 5 and 6 is O volts, but in FIG. 4, it is about 0.7 volts H. It has been improved so that

When the terminal voltage of each light emitting diode A fluctuates, the current output from the constant current power supply 9 shown in FIG. Because it may affect the end Y
・Reducing voltage fluctuations is effective.

Note that the same effect can be obtained by inserting a resistor with an appropriate value in place of DA(;t-)20.

FIG. 5 shows an example in which a field effect transistor (FET) 21 is used in the bypass current switching circuit.

The data signal is converted into an FET control signal by the FET control circuit 22 and applied to the gate electrode of the FET 21. FE
T21 switches the bypass current by turning on or off depending on the magnitude of the goo-to voltage. While the embodiment of FIG. 3 is for low-speed data signal transmission, the embodiment of FIG. 5 can also be applied to high-speed data signal transmission.

Next, the operation of the apparatus of this embodiment having such a configuration will be explained with reference to FIG. First, when the data input signals (11 to (4)) are all "0", the switch drive circuits 14 to 17 output a signal that turns on all the bypass current switching circuits 10 to 13. Therefore, all of the current 1° from the constant current power supply 9 flows through the bypass current switching circuits 10 to 13 and does not flow to the light emitting diodes 5 to 8, and all of the light emitting diodes 5 to 8 output light 4g. do not.

If all 454 (1+ to (4)) are "1", in 1/1, the bypass current switching circuits 17810 to 13 are all in the OFF state, contrary to the state described above. As a result, the current IO of these light emitting diodes 5 to 8 is the same as the flow rate, and all channel power and
Therefore, light (+4"j will be output).

Ma) This data human power 11.8 is all "0", all "
In the case of a combination other than 1 [, the bypass current switching circuit of the "0" chitoniru is turned off, so no current flows to the light-emitting auto corresponding to that channel, and the "1" Only the light emitting diodes of the channels output optical signals. .

In the example, only the light emitting diode 1 was described as the semiconductor light source, but the semiconductor light source may also be a semiconductor diode.

In addition, the number of Nayanru is not limited to four, and this number can increase or decrease.
'(Moyoi.

〔Effect of the invention〕

Because of this configuration and operation, the present invention has the following advantages.

Since a common current flows through all the light-emitting diodes, the required current is small, allowing for a smaller power supply and a more compact design as less heat is generated. If we specifically consider 4-channel signal transmission, the current will decrease from 400mA to 100mA (100mA).
It can be seen that the voltage consumption is reduced to about 2 even considering the increase in power supply voltage for serially driving the light emitting diodes.

■ Since a constant current is always supplied to the light emitting diode drive circuit from the constant current power supply, the value of the total circuit current does not vary depending on the state of the data input signal. Therefore, there is little leakage to other circuits through the power supply circuit. This is incorporated together with a receiver that handles minute signals.
It is highly effective when applied as an optical transceiver, and enables high-quality data transmission.

・1. Easy drawing II! Ic explanation 1st M is a single channel forwarding of the conventional example (+4 configuration of R device).

FIG. 2 (Three studies - circuit configuration diagram of the embodiment device.

3 and 5 are detailed configuration diagrams of the bypass current switching circuit.

1 - logic circuit, 3 - switching transistor, 4 resistor 1iL, 2.5 to 8 - light emitting diode, 9 constant current diode,
10~13-Bypass current switch circuit, 14~
I7-Switch drive circuit, 12 (lishi-'il), 19
- Relay switch, 20 dio-1, 2 If field effect transistor (F1 de I'), 22 FET control circuit.

Patent applicant 1] Hondenki Co., Ltd. representative Patent attorney Naotaka Ide■＋

Claims (1)

[Claims] (1) Multi-channel optical transmission 1iii' in which digital data signals of multiple channels are replaced with optical signals by multiple semiconductor light sources provided for each channel and transmitted.
Terminals of the plurality of semiconductor light sources are connected in series to a power supply, and terminals of the plurality of semiconductor light sources are respectively connected in parallel and correspond to logical values of the digital data signal.
1. A multi-channel optical transmitter, comprising: a switching circuit that is opened and closed; and wherein the battery is constituted by a constant current 'fli source.