JPH08148763A - External modulation type optical transmitting circuit - Google Patents

Abstract

PURPOSE: To easily control temperature and alleviate power consumption by connecting in series a first electron cooling element and a second electron cooling element and then connecting in parallel a current limiting transistor to the second electron cooling element. CONSTITUTION: A semiconductor module built in an electron cooling element (LD module) 1 comprises a thermistor 2, a laser element 3 and a Peltier element 4. A semiconductor optical modulator module built in an electron cooling element (modulation module) 5 comprises a thermistor 6, an optical modulation element 7 and a Peltier element 8. The Peltier element 4 in the LD module 1 and the Peltier element 8 in the modulation module 8 are connected in series. A transistor 12 is connected in parallel with the Peltier element 8. A current flowing into the Peltier element 4 is higher than the current flowing into the Peltier element 8 and an over-current is shunted into the transistor 12. Only the current supplied to the Peltier element 8 is reduced by controlling a feedback circuit 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an external modulation type optical transmission circuit and, more particularly, to a semiconductor laser device and a temperature control circuit for a semiconductor optical modulation device.

[0002]

2. Description of the Related Art Conventionally, in an external modulation type optical transmission circuit composed of a semiconductor laser (hereinafter referred to as LD) module and a semiconductor optical modulator (hereinafter referred to as modulator) module, a thermoelectric cooler ( The temperature control is performed independently on the LD module and the modulator module using a Peltier element).

[0003]

SUMMARY OF THE INVENTION In the above conventional technique,
Since the temperature control is performed independently on the LD module and the modulator module using the Peltier element, there is a disadvantage that power consumption is increased. If two Peltier elements are connected in series and used, the optimum control temperature is set for one of them depending on the difference in heat capacity between the LD element, which is the object to be cooled, and the light modulation element. There is a problem that the temperature deviates from a proper control temperature.

[0004] In view of the above, an object of the present invention is to provide an external modulation type optical transmission circuit which performs optimal temperature control and reduces power consumption.

[0005]

According to the present invention, there is provided an external modulation type optical transmission circuit comprising: a semiconductor laser module with a built-in electronic cooling element comprising a semiconductor laser element, a first temperature detecting element and a first electronic cooling element; A semiconductor optical modulator module with a built-in electronic cooling element including a light modulation element, a second temperature detection element, and a second electronic cooling element; and temperature information of the first temperature detection element and a first reference voltage are input. A first negative feedback circuit, a driving circuit to which an output voltage of the first negative feedback circuit is input, and a second to which temperature information of the second temperature detecting element and a second reference voltage are input. 2 negative feedback circuit, and a transistor connected in parallel with the second electronic cooling element, wherein the first electronic cooling element and the second electronic cooling element are connected in series. .

In the external modulation type optical transmission circuit of the present invention, the drive circuit drives the first and second electronic cooling elements with current.

The external modulation type optical transmission circuit according to the present invention has a first resistor and a second resistor, and the temperature information of the first temperature detecting element is used for the first temperature detecting element. The temperature information of the second temperature detecting element is determined by a resistance value of the second temperature detecting element and a resistance value of the second resistor. It is determined.

[0008]

According to the present invention, the first electronic cooling element (Peltier element) incorporated in each of the semiconductor laser module (LD module) with a built-in electronic cooling element and the semiconductor optical modulator module (modulator module) with a built-in electronic cooling element. And a second electronic cooling element are connected in series, and a current limiting transistor is connected in parallel to the second electronic cooling element. Therefore, a semiconductor laser module with a built-in electronic cooling element and a semiconductor optical modulator module with a built-in electronic cooling element are provided. It is possible to perform optimum temperature control for both the semiconductor laser element (LD element) and the semiconductor optical modulation element, which are the respective objects to be cooled, and realize a temperature control circuit with reduced power consumption. It becomes possible.

[0009]

Next, the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention.

The configuration of the present embodiment will be described with reference to FIG.
The LD module 1 with a built-in Peltier element is a thermistor 2
, An LD element 3 and a Peltier element 4. The modulator module 5 with a built-in Peltier element is configured to have a thermistor 6, a light modulation element 7, and a Peltier element 8. Peltier device 4 in LD module 1
And the Peltier element 8 in the modulator module 5 are connected in series.

The negative feedback circuit 9 inputs the temperature information voltage obtained from the thermistor 2 and the reference voltage V _ref1 . The negative feedback circuit 10 inputs the temperature information voltage obtained from the thermistor 6 and the reference voltage _Vref2 . The drive circuit 11 receives the output voltage of the negative feedback circuit 9 and current drives the Peltier elements 4 and 8 to control the temperature of the LD element 3. Transistor 12
(In this embodiment, an FET is used) is connected in parallel with the Peltier device 8 and limits the current flowing through the Peltier device 8 to control the temperature of the light modulation device 7. The resistor 13 is connected to the thermistor 2, and the resistance value of the thermistor 2 and the resistor 1
The temperature information voltage to be input to the negative feedback circuit 9 is determined based on the resistance value of “3”. The resistor 14 is connected to the thermistor 6, and determines the temperature information voltage to be input to the negative feedback circuit 10 based on the resistance value of the thermistor 6 and the resistance value of the resistor 14.

The operation of this embodiment will be described with reference to FIG.
The LD module 1 is used as a DC light source, and the output light of the LD module 1 is input to the modulator module 5.
The modulator module 5 modulates the intensity of the output light of the LD module 1 with an output signal from the drive circuit 11 to generate a modulated signal light.

The current flowing through the Peltier element 8 is determined by a negative feedback circuit 9 which is a temperature control circuit of the LD module 1. In this type of optical transmission circuit, it is necessary to supply a considerably large current to the LD element 3 to be cooled. Since the power consumption of the object to be cooled increases as the current flowing through the Peltier element increases, the power consumption of the LD element 3 becomes considerably larger than the power consumption of the optical modulator element 7 which is also the object to be cooled. Therefore, L
The current necessary for controlling the temperature of the D module 1 is too large for the modulator module 5, and excessive temperature control is performed. The excess amount of the current is shunted to the transistor 12 connected in parallel with the Peltier element 8 to perform the optimum temperature control on the modulator module 5 as well.

The resistance value of the thermistor 2 is the LD module 1
When the temperature rises, the voltage input to the negative feedback circuit 9 rises. The negative feedback circuit 9 compares the two input voltages and controls the drive circuit 11 to perform negative feedback for compressing the voltage difference.
Therefore, the drive circuit 11 can increase the current supplied to the Peltier element 4 by increasing the voltage value input to the negative feedback circuit 9. Thereby, the temperature of the LD element 3 can be kept constant.

At this time, the current supplied to the Peltier element 8 of the modulator module 5 also increases, but the current value for keeping the temperature of the light modulation element 7 constant is for keeping the temperature of the LD element 3 constant. Since it is smaller than the current value, the Peltier element 8
It is necessary to limit the current value supplied to the power supply. Thermistor 6
Since the resistance value of 1 becomes smaller as the temperature inside the modulator module 5 rises, the voltage value input to the negative feedback circuit 10 rises when the temperature rises. The negative feedback circuit 10 receives the input 2
The transistors 12 are controlled so that the two voltages are compared and negative feedback for compressing the voltage difference is applied. Therefore, the voltage value input to the negative feedback circuit 10 increases,
A current flows through the transistor 12, and only the current supplied to the Peltier element 8 can be reduced. Thereby, the temperature of the light modulation element 7 can be kept constant.

[0016]

As described above, according to the present invention, the first semiconductor laser module (LD module) having a thermoelectric cooler and the first semiconductor optical modulator module (modulator module) having a thermoelectric cooler are incorporated. By connecting an electronic cooling element (Peltier element) and a second electronic cooling element in series and further connecting a current limiting transistor to the second electronic cooling element in parallel, the electronic cooling element built-in semiconductor laser module and the electronic cooling element are cooled. Optimal temperature control can be performed for both the semiconductor laser element (LD element) and the semiconductor optical modulation element, which are the objects to be cooled, of the semiconductor optical modulator module with a built-in element, and power consumption is reduced. There is an effect that a temperature control circuit that is reduced by about 30 to 40% can be realized.

[Brief description of drawings]

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 LD module 2, 6 Thermistor 3 LD element 4, 8 Peltier element 5 Semiconductor modulator module 7 Modulator element 9, 10 Negative feedback circuit 11 Drive circuit 12 Transistor 13, 14 Resistor _Vref1 , _Vref2 reference voltage

Claims (3)

[Claims] A semiconductor laser module including a semiconductor laser element, a first temperature detection element, and a first electronic cooling element, a semiconductor light modulation element, a second temperature detection element, and a second electron element. A semiconductor optical modulator module with a built-in electronic cooling element including a cooling element; a first negative feedback circuit to which temperature information of the first temperature detection element and a first reference voltage are input; A drive circuit to which an output voltage of the feedback circuit is input, a second negative feedback circuit to which temperature information of the second temperature detection element and a second reference voltage are input, and a second electronic cooling element. An external modulation type optical transmission circuit, comprising: transistors connected in parallel, wherein the first electronic cooling element and the second electronic cooling element are connected in series. 2. The external modulation optical transmission circuit according to claim 1, wherein the drive circuit current-drives the first and second electronic cooling elements. 3. A semiconductor device comprising: a first resistor and a second resistor, wherein the temperature information of the first temperature detecting element includes a resistance value of the first temperature detecting element and a resistance value of the first resistor. The temperature information of the second temperature detection element is determined by a resistance value of the second temperature detection element and the resistance value of the second resistor. The external modulation type optical transmission circuit as described in the above.