JP2002344066A - Temperature control module of laser diode and drive method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature control module of laser diode that has high control temperature performance, and a drive method with enhanced control performance of temperature that is suitable for temperature control module. SOLUTION: A thermally conductive insulation board 1-6 of a main Peltier element 1, in contact thermally with a laser diode 4, is thermally connected with another thermally conductive insulation board 1-7a of an auxiliary Peltier element 1a which is different from the main Peltier element, through a thermally conductive cylinder 6 having superior thermal conductivity, and the thermally conductive insulation board of the main Peltier element which is in thermal contact with the laser diode is made to thermally have the same property as the thermally conductive insulation board of the auxiliary Peltier element in thermal contact with the thermally conductive cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diode temperature control module and a driving method thereof, and more particularly to a laser diode temperature control module having a high temperature control capability and a temperature control module having a high temperature control capability. Regarding a suitable driving method. In Japan, the digital transmission method using optical signals began to be used around the same time that the digital transmission method using electric signals established itself as the main transmission method. It has taken the place of the transmission system.

[0002] Since optical fiber cables are originally broadband, the optical digital transmission system has a large capacity in combination with the speeding up of a laser diode as an electric / optical conversion element and a photo diode as an optical / electrical conversion element. Although it has grown as a method suitable for transmission systems, the increase in capacity by single wavelength transmission is approaching its limit. On the other hand, with the advent of the multimedia age, especially with the recent rapid spread of the Internet, the realization of a much larger capacity optical digital transmission system is urgently required.

[0003] A single-wavelength transmission system for transmitting a single-wavelength optical signal modulated by an electric signal over a single optical fiber cable, and a different optical signal over a single optical fiber cable. A wavelength division multiplexing transmission system for multiplexing and transmitting modulated optical signals of a plurality of wavelengths (generally referred to as "WDM system". "WDM" is an abbreviation for "Wavelength Division Multplexing"). Have been developed in parallel,
Under the above background, the weight has been shifted to the development of the wavelength division multiplexing transmission system in order to cope with the rapid growth of the transmission demand. In addition, the number of wavelengths to be multiplexed increases to cope with a sudden increase in required transmission capacity, and the wavelength interval is becoming narrower.

[0004] Generally, the oscillation wavelength of a laser diode has a characteristic that it essentially varies with temperature. Therefore, it is necessary to accurately control the temperature of the laser diode so that stable communication can be performed even when the wavelength interval becomes narrow. In addition, regardless of the wavelength multiplex transmission method and the single wavelength transmission method, optical fiber amplifiers have been widely used, and as the gain and output power required for optical fiber amplifiers have increased, The output power of a pump laser diode that supplies pump light to a rare earth-doped optical fiber constituting an optical fiber amplifier is also increasing. In order to output high power pumping light, it is necessary to increase the drive current supplied to the pumping laser diode, and the power consumption of the pumping laser diode increases.
As a result, the pump laser diode operates at a high temperature, and not only the fluctuation of the output wavelength becomes large, but also the power consumption becomes larger and the reliability is reduced for a long time.

[0005] Therefore, it is necessary to appropriately control the temperature of the pump laser diode to suppress fluctuations in the output wavelength, and to ensure long-term reliability.

[0006]

2. Description of the Related Art In order to control the temperature of a laser diode, a temperature control module to which a Peltier element is applied is formed, and a laser diode is mounted on a heat conductive insulating plate in contact with a thermoelectric semiconductor electrode constituting the Peltier element. Usually, the temperature of the laser diode is controlled by the direction and the value of the current flowing through the Peltier element by die bonding the chip.

FIG. 14 is a diagram showing the principle of cooling / heating by a Peltier element, and shows a Peltier element composed of a pair of P-type thermoelectric semiconductors and N-type thermoelectric semiconductors. FIG.
In 4, 1 is a Peltier element, and is a P-type thermoelectric semiconductor 1.
-1, N-type thermoelectric semiconductor 1-2, P-type thermoelectric semiconductor 1-
1 and one terminal of the N-type thermoelectric semiconductor 1-2 are connected to the metal electrode 1-3 and the N-type thermoelectric semiconductor 1-2.
A metal electrode 1-5 formed on the other terminal of the P-type thermoelectric semiconductor 1-1, a metal electrode 1-4 formed on the other terminal of the P-type thermoelectric semiconductor 1-1, and a P-type thermoelectric semiconductor 1-1 and the N-type Heat conductive insulating plate 1-6 arranged on the side to which thermoelectric semiconductor 1-2 is connected
And P-type thermoelectric semiconductor 1-1 and N-type thermoelectric semiconductor 1-2
Is constituted by a heat conductive insulating plate 1-7 arranged on the side not connected.

Incidentally, the P-type thermoelectric semiconductor 1-1 and the N-type thermoelectric semiconductor 1-2 are thermoelectric semiconductors usually made of bismuth tellurium as a basic material, and the P-type thermoelectric semiconductor 1-1 and the N-type thermoelectric semiconductor are used. The thermal resistance between the semiconductor 1-2 and the heat conductive insulating plates 1-6 and 1-7 is configured to be very small. 2
Reference numeral 3 denotes a battery, and the positive electrode is replaced with a metal electrode 1-5 as shown in FIG.
The negative electrode is connected to the metal electrodes 1-4.

Accordingly, the current flows in the direction of the arrow in FIG. That is, on the metal electrode 1-3 side, electrons move from the P-type thermoelectric semiconductor to the N-type thermoelectric semiconductor, and
And on the side 1-4, electrons move from the N-type thermoelectric semiconductor to the P-type thermoelectric semiconductor. The fact that electrons move from the P-type thermoelectric semiconductor to the N-type thermoelectric semiconductor on the metal electrode 1-3 side means that electrons move from a low energy state to a high energy state. On the -3 side, the vibration energy of the crystal lattice of the surrounding material is absorbed.
That is, the heat conductive insulating plate 1-6 is cooled.

On the other hand, the fact that electrons move from the N-type thermoelectric semiconductor to the P-type thermoelectric semiconductor on the side of the metal electrodes 1-5 and 1-4 means that the electrons move from a high energy state to a low energy state. The metal electrodes 1-5
And 1-4 provide the energy to be released to the surrounding material. That is, the heat conductive insulating plate 1-7 is heated. When the polarity of the battery is reversed from that in FIG. 14, the heat conductive insulating plate 1-6 is heated, and the heat conductive insulating plate 1-7 is cooled.

That is, since the heating and cooling of the Peltier element differ depending on the direction of the current, the laser diode chip is die-bonded to one of the heat conductive insulating plates, and the current is switched according to the detected temperature of the laser diode. Then, the temperature of the laser diode chip can be controlled in any direction. The heating or cooling effect depends on the magnitude of the current.

A one-stage element in which a plurality of pairs of P-type and N-type thermoelectric semiconductors as shown in FIG. 14 are electrically connected in parallel, and a pair of P-type and N-type thermoelectric semiconductors as shown in FIG. There are a plurality of multistage elements which are serially connected in series, but the multistage elements can increase the temperature difference between the cooling side and the heating side. FIG. 12 shows a conventional basic temperature control module, and FIG.
FIG. 12B is a top view of the temperature control module, and FIG.

In FIG. 12, reference numeral 1 denotes a Peltier element, which includes a heat conductive insulating plate 1-6, a heat conductive insulating plate 1-7, and a thermoelectric semiconductor portion 1-8. Here, the heat conductive insulating plate 1
The -6 and the heat conductive insulating plate 1-7 have a metal layer formed on the surface, and a laser diode, a thermistor and the like are bonded on the metal layer. Therefore, ceramic is usually used.

The thermoelectric semiconductor section 1-8 is constituted by a P-type thermoelectric semiconductor 1-1, an N-type thermoelectric semiconductor 1-2, a metal electrode 1-3, a metal electrode 1-4 and a metal electrode 1-5 in FIG. It is composed. Reference numeral 2 denotes a heat radiating plate which is in contact with one of the heat conducting insulating plates 1-7 of the Peltier element 1 and conducts the heat generated by the Peltier element 1 to the outside and transmits the heat absorbed by the Peltier element 1 from the outside. Here, when the Peltier element absorbs heat, the "radiator plate" has a somewhat unnatural feeling, but is named "radiator plate" because it interprets that a negative amount of heat is released. The heat radiating plate 2 is usually a metal plate, but does not prevent the heat radiating plate 2 from being made of ceramic. The radiator plate 2 is usually fixed to the bottom of a metal case on which the temperature control module of FIG. 12 is mounted.

Reference numeral 3 denotes one of the heat conductive insulating plates 1 of the Peltier device.
-6, a Kovar plate bonded to -4, a laser diode bonded to the Kovar plate 3, and 5 a Kovar plate 3.
Is a thermistor that outputs the temperature information of the laser diode 4 by bonding to the thermistor. Here, the Peltier element 1
Bonding the Kovar plate 3 to the heat conductive insulating plate 1-6 and bonding the laser diode 4 and the thermistor 5 on the Kovar plate 3 is based on the small thermal expansion coefficient of the Kovar plate 3. In order to prevent stress from being applied to the laser diode 4 and the thermistor 5 due to expansion or contraction of the heat conductive insulating plate 1-6 due to temperature fluctuation, the laser diode 4 and other optical elements not shown are omitted. This is to prevent the relative position from changing.

Here, in FIG. 12, the laser diode 4
Is shown as directly adhered to the Kovar plate 3, but the base is adhered to the Kovar plate 3 in order to align the optical axis of the output light of the laser diode 4 with the optical axis of the external optical fiber. In some cases, the laser diode 4 is bonded. Normally, a photodiode that supplies a signal obtained by electrically converting the back light of the laser diode 3 to an automatic power control circuit or a lens holder for coupling the output light of the laser diode 4 to an optical fiber. The illustrated lens is also mounted on the Kovar plate 3, but is not illustrated because it is not the essence of the present invention and it is desired to avoid complication of the drawing.

Further, a driving circuit and a wiring for supplying a driving current to the Peltier element are not shown in the drawing to avoid complication of the drawing. When the temperature of the laser diode 4 is high and needs to be cooled, the heat conduction insulating plate 1-6 side of the Peltier element 1 absorbs heat and lowers the temperature of the laser diode 4. At this time, since the heat conductive insulating plate 1-7 generates heat, the heat radiating plate 2 radiates the generated heat to the outside to enhance the cooling effect.

On the other hand, when the temperature of the laser diode 4 is low and it is necessary to increase the temperature, the Peltier element 1
Generates heat on the side of the heat conductive insulating plate 1-6. At this time, since the heat conductive insulating plate 1-7 absorbs heat, the heat radiating plate 2 conducts heat from the outside to the heat conductive insulating plate 1-7 to enhance the heat generating effect. As described above, the temperature of the laser diode 4 is controlled to be constant.

[0019]

The amount of heat absorbed on the low-temperature side of the Peltier element increases in proportion to the drive current flowing through the thermoelectric semiconductor, but Joule heat due to the internal resistance of the thermoelectric semiconductor increases in proportion to the square of the drive current. When the temperature difference between the low-temperature side and the high-temperature side is constant, there is a current value at which the amount of heat absorption is maximized, and the amount of heat absorption decreases when a drive current larger than that is applied.

FIG. 13 is a diagram showing a limit of cooling by the Peltier device. In FIG. 13, the vertical axis represents the temperature of the laser diode (in the figure, “laser diode” is
It is represented by the abbreviation "LD" which stands for r Diode. ), The horizontal axis is the drive current, and the vertical and horizontal axes are logarithmic. Since the heat absorption on the low temperature side in the Peltier element increases in proportion to the drive current flowing through the thermoelectric semiconductor, the temperature of the laser diode decreases at a slope of -1 with the increase in the drive current, but the heat absorption becomes maximum. When a drive current higher than the current is passed, the amount of heat absorbed decreases rather,
The temperature of the laser diode increases in ramp 2 with increasing drive current. Therefore, it is meaningless to flow a current exceeding the maximum current I _M.

In order to overcome the cooling limit, it is necessary to use a Peltier element having a large logarithm of the thermoelectric semiconductor or to reduce the heat resistance from the heat conductive insulating plate on the high temperature side to the outside. However, if a Peltier element having a large logarithm of a thermoelectric semiconductor is used, the area of the Peltier element must be increased, and in order to reduce the thermal resistance from the heat conductive insulating plate on the high-temperature side to the outside, at least the heat sink is required. It is necessary to increase the surface area, and in any case, there is a problem that the temperature control module becomes large. In the latter case, there is also a problem that the weight of the temperature control module increases.

Further, when cooling the laser diode 4 in the temperature control module having the structure shown in FIG. 12, the heat of the laser diode 4 is transmitted to the Peltier element 1 via the Kovar plate 3 and the laser diode 4 is also cooled.・ Diode 4
Is radiated into the upper space. Since the headspace of the laser diode 4 is closed by a metal case for mounting the temperature control module of FIG. 12, the amount of heat radiated by the laser diode 4 is accumulated in the metal case. In addition, the metal case itself is heated by heat generated by elements and circuits existing outside. For this reason, there is a problem that the cooling effect of the laser diode 4 is lost and the control of the temperature of the laser diode 4 becomes inaccurate.

The present invention has been made in view of the above problems, and has as its object to provide a temperature control module for a laser diode having a high temperature control capability and a drive system suitable for a temperature control module having a high temperature control capability.

[0024]

Means for Solving the Problems The first invention is directed to a laser device.
The heat conductive insulating plate of the main Peltier element with which the diode is in thermal contact with one of the auxiliary Peltier elements different from the main Peltier element is thermally connected by a heat conductive cylinder having good thermal conductivity. And the heat conducting insulating plate of the main Peltier device, which is in thermal contact with the laser diode, and the heat conducting insulating plate of the auxiliary Peltier device, which is in thermal contact with the heat conducting tube. It is a temperature control module for a laser diode that has the same thermal properties.

According to the first aspect, the heat conductive insulating plate of the main Peltier element with which the laser diode is in thermal contact with one of the auxiliary Peltier elements has good thermal conductivity. Because it is thermally connected by a heat transfer cylinder,
The temperature difference between the thermally conductive insulating plate of the main Peltier element that is in thermal contact with the laser diode and the thermally conductive insulating plate of the auxiliary Peltier element that is in thermal contact with the thermal conductive tube is reduced.

In addition, the heat conducting insulating plate of the main Peltier element, which is in thermal contact with the laser diode, and the heat conducting insulating plate of the auxiliary Peltier element, which is in thermal contact with the heat conducting tube. Since the same thermal properties are provided, the laser diode is in thermal contact with the heat conducting cylinder when the heat conducting insulating plate of the main Peltier element is in thermal contact with the heat conducting cylinder. The heat conducting insulating plate of the auxiliary Peltier element is also on the low temperature side, and when the heat conducting insulating plate of the main Peltier element with which the laser diode is in thermal contact is on the high temperature side, heat is applied to the heat conducting cylinder. The thermally conductive insulating plate of the auxiliary Peltier element that is in contact with the substrate is also on the high temperature side.

Therefore, when the laser diode needs to be cooled, the cooling capacity is high, and when it is necessary to raise the temperature of the laser diode, the temperature raising capacity is high, so that the temperature control of the laser diode can be accurately performed. It is possible to do. According to a second aspect, in the temperature control module for a laser diode according to the first aspect, a plurality of Peltier elements are stacked to constitute the auxiliary Peltier element, and the main Peltier is thermally connected by the heat conducting tube. A laser diode for making the thermal properties of the heat conductive insulating plate of the element and that of the auxiliary Peltier element the same, and reversing the thermal properties of the heat conductive insulating plates in contact with each other of the stacked Peltier elements. Temperature control module.

According to a second aspect, in the laser diode temperature control module according to the first aspect, the auxiliary Peltier element is formed by stacking a plurality of Peltier elements.
Since the thermal properties of the heat conductive insulating plate of the main Peltier element and the heat conductive insulating plate of the auxiliary Peltier element which are thermally connected by the heat conductive cylinder are the same, the auxiliary Peltier element is different from the main Peltier element. Temperature control in the same direction is performed.

Moreover, since the thermal properties of the heat conducting insulating plates in contact with the stacked Peltier devices are reversed, the temperature of the two heat conducting insulating plates of the stacked Peltier devices is in the same direction. become. Therefore, the plurality of stacked Peltier elements enhance the temperature control ability of each other, so that the temperature control ability of the auxiliary Peltier element is increased. As a result, the laser constituted by the main Peltier element, the heat conducting tube, and the auxiliary Peltier element The temperature control capability of the diode temperature control module itself is increased, so that the temperature control of the laser diode can be performed more accurately.

A third invention is a driving method of the laser diode temperature control module according to the first invention or the second invention, wherein the auxiliary Peltier is used when the measured temperature of the laser diode exceeds a set temperature. A specified drive current is supplied to the element, and when the temperature of the laser diode is within a set temperature, no drive current is supplied to the auxiliary Peltier element, and in any case, the measurement is applied to the main Peltier element. This is a driving method of a laser diode temperature control module that supplies a driving current set according to the temperature.

According to the third aspect, when the measured temperature of the laser diode exceeds the set temperature, a specified drive current is supplied to the auxiliary Peltier element, and the main Peltier element is set according to the measured temperature. Since the driving current is supplied, the temperature control capability of the temperature control module of the laser diode is enhanced, and the temperature of the laser diode can be accurately controlled.

On the other hand, when the temperature of the laser diode is below the set temperature, no driving current is supplied to the auxiliary Peltier element, and the driving current set corresponding to the measured temperature is supplied to the main Peltier element. Is supplied, it is possible to control the temperature of the laser diode while reducing the driving power of the temperature control module for the laser diode.

A fourth aspect of the present invention is a driving method of the laser diode temperature control module according to the first or second aspect, wherein the measured temperature of the laser diode exceeds a set temperature, or When the drive current of the main Peltier element exceeds the maximum current, a specified drive current is supplied to the auxiliary Peltier element, and the measured temperature of the laser diode is lower than the set temperature and the drive current of the main Peltier element is lower than the maximum current. A temperature control module for a laser diode that does not supply a driving current to the auxiliary Peltier element in any case, and supplies a driving current set in accordance with the measured temperature to the main Peltier element in any case. Is the driving method.

According to the fourth aspect, when the measured temperature of the laser diode exceeds the set temperature or when the drive current of the main Peltier element exceeds the maximum current, the prescribed drive current is supplied to the auxiliary Peltier element. The main Peltier element is supplied with a drive current that is set according to the measured temperature, so that the temperature control capability of the laser diode temperature control module is increased and the temperature of the laser diode is accurately controlled. can do.

On the other hand, when the measured temperature of the laser diode is lower than the set temperature and the driving current of the main Peltier element is lower than the maximum current, no driving current is supplied to the auxiliary Peltier element, and the main Peltier element is not supplied. Since the drive current set in accordance with the measured temperature is supplied, the laser diode temperature control can be performed while reducing the drive power of the laser diode temperature control module.

Further, since the above determination is made based on both the measured drive current and the measured temperature, it is possible to avoid the danger that the auxiliary Peltier element will not be driven when it should be driven. A fifth invention is a driving method of the temperature control module of the laser diode according to any one of the first invention and the second invention, wherein a voltage corresponding to the detected temperature of the laser diode and a reference voltage are provided. An automatic temperature control circuit for controlling a drive current of the main Peltier element by a difference, and supplying a specified drive current to the auxiliary Peltier element at least when detecting that the temperature of the laser diode exceeds a specified temperature And a detection circuit for outputting a control signal for driving the temperature control module of the laser diode.

According to the fifth invention, an automatic temperature control circuit for controlling the drive current of the main Peltier element based on the difference between the voltage corresponding to the detected temperature of the laser diode and the reference voltage, and at least the detected laser diode It has a detection circuit that outputs a control signal to supply a specified drive current to the auxiliary Peltier element when it detects that the temperature of the diode exceeds the specified temperature.
When the measured temperature of the diode exceeds the set temperature, a specified drive current is supplied to the auxiliary Peltier element, and a drive current set according to the measured temperature is supplied to the main Peltier element. The temperature control capability of the temperature control module of the present invention is enhanced, and the temperature of the laser diode can be controlled accurately.

On the other hand, if at least the temperature of the laser diode is within the set temperature, no drive current is supplied to the auxiliary Peltier element, and the drive set to the main Peltier element corresponding to the measured temperature is not supplied. Since the current is supplied, the temperature of the laser diode can be controlled while reducing the driving power of the laser diode temperature control module.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The technology of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a temperature control module according to a first embodiment of the present invention, taken along a plane including an optical axis of output light of a laser diode. FIG. FIG. 3 is a perspective view of the temperature control module in the embodiment.

In FIGS. 1 and 2, reference numeral 1 denotes a Peltier element, which includes a heat conductive insulating plate 1-6, a heat conductive insulating plate 1-7, and a thermoelectric semiconductor unit 1-8. Note that the Peltier element 1 is referred to as a main Peltier element. Here, the heat conductive insulating plate 1-6 and the heat conductive insulating plate 1-7 have a metal layer formed on the surface thereof, and a laser diode, a thermistor, etc. are bonded on the metal layer. You.

The thermoelectric semiconductor section 1-8 is constituted by the P-type thermoelectric semiconductor 1-1, N-type thermoelectric semiconductor 1-2, metal electrodes 1-3, metal electrodes 1-4 and metal electrodes 1-5 in FIG. It is composed. Reference numeral 2 denotes a heat radiating plate which is in contact with one of the heat conducting insulating plates 1-7 of the Peltier element 1 and conducts the heat generated by the Peltier element 1 to the outside and transmits the heat absorbed by the Peltier element 1 from the outside. Note that the heat radiating plate 2 is usually a metal plate, but this does not preclude the use of ceramic. Then, the radiator plate 2 is usually fixed to the bottom of the metal case on which the temperature control module of FIG. 1 or 2 is mounted. In this case, in order to improve the contact between the heat radiating plate 2 and the bottom of the metal case, the heat radiating plate 2 is brought into contact with the bottom of the metal case via a layer of silicone having good thermal conductivity.
It is preferable to fix with a screw or the like.

Reference numeral 3 denotes one of the heat conductive insulating plates 1 of the Peltier device.
-6, a Kovar plate bonded to -4, a laser diode bonded to the Kovar plate 3, and 5 a Kovar plate 3.
Is a thermistor that outputs the temperature information of the laser diode 4 by bonding to the thermistor. Normally, a photodiode that supplies a signal obtained by electrically converting the back light of the laser diode 3 to an automatic power control circuit or a lens holder for coupling the output light of the laser diode 4 to an optical fiber. The attached lens is also adhered on the Kovar plate 3, but is not shown because it is not the essence of the present invention and it is desired to avoid complication of the drawing. Also, wiring for supplying a drive current to the Peltier element and the like are not shown in order to avoid complication of the drawing.

Here, the Kovar plate 3 is adhered to the heat conductive insulating plate 1-6 constituting the Peltier element 1, and the Kovar plate 3 is bonded.
The laser diode 4 and the thermistor 5 are bonded on the substrate by utilizing the small thermal expansion coefficient of the Kovar plate 3 and expanding or contracting the heat conductive insulating plate 1-6 due to temperature fluctuation. This is to prevent stress from being applied to the thermistor 5 and to prevent a change in the relative position between the laser diode 4 and another optical element (not shown).

Although FIG. 1 shows that the laser diode 4 is directly bonded on the Kovar plate 3, the optical axis of the output light of the laser diode 4 and the optical axis of the external optical fiber are aligned. In some cases, a laser diode 4 is bonded to the Kovar plate 3 after the base is adhered thereto. Reference numeral 6 denotes a heat conducting tube, and a laser diode 4
A hole 6-1 is provided at the position corresponding to the optical axis of the output light. The heat conduction cylinder 6 will be described later in detail.

Reference numeral 1a denotes a Peltier device, which is composed of a heat conductive insulating plate 1-6a, a heat conductive insulating plate 1-7a, and a thermoelectric semiconductor portion 1-8a, like the Peltier device 1. Note that the Peltier element 1a is referred to as an auxiliary Peltier element. 2
Reference symbol a denotes a heat radiating plate which contacts one of the heat conducting insulating plates 1-7a of the Peltier element 1a, conducts heat generated by the Peltier element 1a to the outside, and conducts heat absorbed by the Peltier element 1 from the outside. The heat radiating plate 2a is usually a metal plate.
It does not prevent the use of ceramic. Heat sink 2
It is preferable that a can be in thermal contact with a top plate of a metal case mounting the temperature control module of FIG. 1 or 2 when the top plate is mounted. However, since it is difficult to bring the metal or ceramic radiator plate 2a into surface contact with the metal top plate over a wide area, the heat radiator plate 2a has relatively good thermal conductivity, such as silicone, on the upper surface thereof. It is preferable to form a layer of a substance which is easily deformed.

In FIGS. 1 and 2, wirings for supplying a drive current to the Peltier element and the like are omitted for simplification of the drawing. FIG. 3 shows an example of the structure of the heat conduction cylinder. In FIG. 3, reference numeral 6 denotes a heat conducting tube,
A hole 6-1 is provided at a position corresponding to the optical axis of the output light of the diode.

In order to enhance the temperature control capability of the temperature control module of the present invention, the heat conduction tube 6 is provided with a heat conduction insulating plate of the main Peltier element in thermal contact with the laser diode shown in FIG. 1 or FIG. It is necessary to have a high thermal conductivity because the thermal conduction tube 1-6 and the thermal conduction insulating plate 1-6a of the auxiliary Peltier element which are in thermal contact with each other are thermally connected. It is.

Therefore, the material forming the heat conducting tube 6 is preferably a metal or a ceramic. In the case of metal, it can be processed into the shape shown in FIG. 3 by cutting. Further, in the case of ceramic, even if a hole is formed in a predetermined position of a ceramic green sheet and then sintered into a cylindrical shape as shown in FIG. Alternatively, three sintered ceramic plates may be bonded.

FIG. 3 shows an example of a tube having a rectangular cross section, but the cross sectional shape is not particularly limited. However, considering the ease of processing of the heat conducting cylinder 6 itself, the fact that the shape of the heat conducting insulating plate of the Peltier element is usually rectangular, and the fact that a laser diode or the like is mounted on the heat conducting insulating plate, the heat conduction is considered. A rectangular cross section is preferred because it is not desired to reduce the effective area of the conductive insulating plate.

Further, when the ceramic green sheet is processed into the shape shown in FIG. 3, it is somewhat difficult to accurately form the shape of the heat conducting cylinder 6 including the distortion due to heating. It is preferable to improve the flatness of the upper and lower surfaces by polishing the upper and lower surfaces of the heat conducting tube 6 by a normal method, and to make both surfaces parallel. Next, a procedure for assembling the temperature control module shown in FIG. 1 or 2 will be described.

1. Thermal conductive insulating plate 1-6 of main Peltier element
The Kovar plate 3 is bonded by a usual method. 2. A laser diode 4, a thermistor 5, and the like are bonded on the Kovar plate 3 by an ordinary method. 3. Thermal conduction cylinder 6 and thermal conduction insulating plate 1 of auxiliary Peltier element
6a. When the heat conductive cylinder 6 is made of ceramic, it may be bonded using an adhesive. When it is made of metal, the metal layer may be formed on the heat conductive insulating plate 1-6a, so that silver brazing may be used.

4. An object in which the heat conducting cylinder 6 and the auxiliary Peltier element are fixed is fixed to the heat conducting insulating plate 1-6 of the main Peltier element. The fixing method is the same as above. 5. The main peltier element, the heat conducting tube 6 and the auxiliary peltier element are integrated and fixed to the radiator plate 2 and the radiator plate 2a by an ordinary method. Then, the temperature control module assembled as described above is used by being fixed to the bottom of the metal case.

The thermal properties of the heat conducting insulating plates of the main Peltier element and the auxiliary Peltier element are as follows. if,
When the heat conducting insulating plate 1-6 of the main Peltier element is on the low temperature side, the heat conducting insulating plate 1 of the auxiliary Peltier element thermally connected to the heat conducting insulating plate 1-6 via the heat conducting tube 6 -6a
Is also on the low temperature side. When the heat conducting insulating plate 1-6 is on the low temperature side, it is time to cool the laser diode 4. However, since the heat conducting insulating plate 1-6a is also on the low temperature side, the temperature is controlled by the temperature control module of FIG. 1 or FIG. The control capability is increased, so that the laser diode 4 can be cooled quickly and the temperature of the laser diode 4 can be accurately controlled.

Conversely, when it is necessary to raise the temperature of the laser diode 4, the heat conduction insulating plate 1-6 is brought to a higher temperature side by controlling the drive circuit of the main Peltier element, but the heat conduction insulation of the auxiliary Peltier element is increased. Since the temperature of the plate 1-6a is also increased by the control of the drive circuit, the temperature control capability of the temperature control module of FIG. 1 or 2 is increased, so that the laser diode 4 can be heated quickly and the temperature of the laser diode 4 can be controlled. Can be performed accurately.

That is, the heat conductive insulating plate 1-6 of the main Peltier device and the heat conductive insulating plate 1-6a of the auxiliary Peltier device, which are in thermal contact with the laser diode 4, are connected to the heat conductive plate having good thermal conductivity. The thermally conductive insulating plate 1-6a of the main Peltier element thermally connected to the laser diode 4 and the auxiliary Peltier element thermally in contact with the thermally conductive cylinder 6 Making the heat conductive insulating plate 1-6a thermally the same in nature is the basis of the technique of the configuration of FIG.

According to the above configuration, the heat conduction insulating plate of the main Peltier element with which the laser diode is in thermal contact and one of the auxiliary Peltier elements have good thermal conductivity. The thermal conduction of the main Peltier element in thermal contact with the laser diode and the thermal conduction of the auxiliary Peltier element in contact with the thermal conduction cylinder. The temperature difference with the insulating plate becomes smaller.

In addition, the heat conducting insulating plate of the main Peltier element, which is in thermal contact with the laser diode, and the heat conducting insulating plate of the auxiliary Peltier element, which is in thermal contact with the heat conducting tube. Since the same thermal properties are provided, the laser diode is in thermal contact with the heat conducting cylinder when the heat conducting insulating plate of the main Peltier element is in thermal contact with the heat conducting cylinder. The heat conducting insulating plate of the auxiliary Peltier element is also on the low temperature side, and when the heat conducting insulating plate of the main Peltier element with which the laser diode is in thermal contact is on the high temperature side, heat is applied to the heat conducting cylinder. The thermally conductive insulating plate of the auxiliary Peltier element that is in contact with the substrate is also on the high temperature side.

Therefore, when the laser diode needs to be cooled, the cooling capacity becomes high, and when it is necessary to raise the temperature of the laser diode, the temperature raising capacity becomes high, so that the temperature control of the laser diode can be performed accurately. It is possible to do. FIG. 4 is a sectional view of a temperature control module according to a second embodiment of the present invention, taken along a plane including an optical axis of output light of a laser diode.

In FIG. 4, reference numeral 1 denotes a Peltier element, which includes a heat conductive insulating plate 1-6, a heat conductive insulating plate 1-7, and a thermoelectric semiconductor portion 1-8. Note that the Peltier element 1 is referred to as a main Peltier element. Here, the heat conductive insulating plate 1
The -6 and the heat conductive insulating plate 1-7 have a metal layer formed on the surface, and a laser diode, a thermistor and the like are bonded on the metal layer. Therefore, ceramic is usually used.

The thermoelectric semiconductor section 1-8 is constituted by the P-type thermoelectric semiconductor 1-1, N-type thermoelectric semiconductor 1-2, metal electrodes 1-3, metal electrodes 1-4 and metal electrodes 1-5 in FIG. It is composed. Reference numeral 2 denotes a heat radiating plate which is in contact with one of the heat conducting insulating plates 1-7 of the Peltier element 1 and conducts the heat generated by the Peltier element 1 to the outside and transmits the heat absorbed by the Peltier element 1 from the outside. Note that the heat radiating plate 2 is usually a metal plate, but this does not preclude the use of ceramic. Then, the radiator plate 2 is usually fixed to the bottom of the metal case on which the temperature control module of FIG. 1 or 2 is mounted. In this case, in order to improve the contact between the heat radiating plate 2 and the bottom of the metal case, the heat radiating plate 2 is brought into contact with the bottom of the metal case via a layer of silicone having good thermal conductivity.
It is preferable to fix with a screw or the like.

Reference numeral 3 denotes a Kovar plate bonded to one of the heat conducting insulating plates 1-6 of the Peltier element 1, 4 denotes a laser diode bonded to the Kovar plate 3, and 5 denotes a laser diode bonded to the Kovar plate 3. 4 is a thermistor that outputs temperature information. Normally, a photodiode that supplies a signal obtained by converting the back light of the laser diode 4 to an electric power control circuit or a lens holder for coupling the output light of the laser diode 4 to an optical fiber. The attached lens is also adhered on the Kovar plate 3, but is not shown because it is not the essence of the present invention and it is desired to avoid complication of the drawing. Also, wiring for supplying a drive current to the Peltier element and the like are not shown in order to avoid complication of the drawing.

Here, the Kovar plate 3 is adhered to the heat conductive insulating plate 1-6 constituting the Peltier element 1, and the Kovar plate 3
The laser diode 4 and the thermistor 5 are bonded on the substrate by utilizing the small thermal expansion coefficient of the Kovar plate 3 and expanding or contracting the heat conductive insulating plate 1-6 due to temperature fluctuation. This is to prevent stress from being applied to the thermistor 5 and to prevent a change in the relative position between the laser diode 4 and an optical element (not shown).

FIG. 4 shows that the laser diode 4 is directly bonded on the Kovar plate 3, but the optical axis of the output light of the laser diode 4 and the optical axis of the external optical fiber are aligned. In some cases, a laser diode 4 is bonded to the Kovar plate 3 after the base is adhered thereto. Reference numeral 6 denotes a heat conducting tube, and a laser diode 4
A hole 6-1 is provided at the position corresponding to the optical axis of the output light. The heat conduction cylinder 6 has already been described in detail.

Reference numeral 1a denotes a Peltier device, which is composed of a heat conductive insulating plate 1-6a, a heat conductive insulating plate 1-7a, and a thermoelectric semiconductor portion 1-8a, like the Peltier device 1. Also, 1b
Denotes a Peltier device, and similarly to the Peltier device 1, a heat conductive insulating plate 1-6b, a heat conductive insulating plate 1-7b, and a thermoelectric semiconductor unit 1
-8b. A stack of the Peltier element 1a and the Peltier element 1b is called an auxiliary Peltier element.

Reference numeral 2a denotes a heat radiating plate which is in contact with one of the heat conducting insulating plates 1-7b of the Peltier element 1b, conducts the heat generated by the Peltier element 1b to the outside, and conducts the heat absorbed by the Peltier element 1b from the outside. is there. The heat radiating plate 2a is usually a metal plate, but this does not prevent the heat radiating plate 2a from being made of ceramic. It is preferable that the heat radiating plate 2a can be in thermal contact with the top plate of the metal case on which the temperature control module of FIG. 4 is mounted. However, since it is difficult to bring the metal or ceramic heat radiating plate 2b into contact with the metal top plate in a wide area, it is relatively good in thermal conductivity such as silicone on the upper surface of the heat radiating plate 2b. It is preferable to form a layer of a substance which is easily deformed by the above method.

In FIG. 4, wirings for supplying a drive current to each Peltier element are not shown for simplification of the drawing. The assembling procedure of the temperature control module shown in FIG. 4 includes a Peltier device 1a and a Peltier device 1b.
Are merely different from the temperature control module shown in FIG. 1 or FIG.

The thermal properties of the heat conducting insulating plates of the main Peltier element and the auxiliary Peltier element are as follows. First, the Peltier element 1 constituting the auxiliary Peltier element and the heat conductive insulating plate 1-6 of the Peltier element 1 as the main Peltier element
It is the same as the temperature control module of FIG. 1 or FIG. 2 that the thermal properties of the heat conductive insulating plates 1-6a need to be the same. Therefore, what should be considered here is what to do with the thermal properties of the heat conducting insulating plates of the Peltier elements 1a and 1b constituting the auxiliary Peltier elements.

If the heat conduction insulating plate 1 of the Peltier element 1a
If -6a is on the low temperature side, the heat conduction insulating plate 1-7a of the Peltier element 1a is naturally on the high temperature side and is trying to radiate the heat generated by the Peltier element 1a. Therefore, if the heat conduction insulating plate 1-6b of the Peltier element 1b is controlled to the low temperature side,
The heat conductive insulating plate 1-7a of the Peltier element 1a can be cooled. Since the heat conductive insulating plate 1-7b of the Peltier element 1b is in thermal contact with the heat sink 2a, the heat generated by the Peltier element 1b can be transmitted to the heat sink 2a.

That is, in an auxiliary Peltier element in which a plurality of Peltier elements are stacked, it is necessary to reverse the thermal properties of the heat conducting insulating plates in which the stacked Peltier elements are in contact with each other. It is the root of the temperature control module having the configuration in FIG. 4 that the auxiliary Peltier element thermally connected by the heat conduction tube 6 and the main Peltier element have the same thermal properties.

According to the above configuration, in the laser diode temperature control module having the configuration shown in FIG. 1, a plurality of Peltier elements are stacked to form the auxiliary Peltier element, and the Peltier element is thermally connected by the heat conducting tube. Since the thermal properties of the heat conducting insulating plate of the main Peltier element and the heat conducting insulating plate of the auxiliary Peltier element are made the same, the auxiliary Peltier element performs temperature control in the same direction as the main Peltier element.

Further, since the thermal properties of the heat conducting insulating plates in contact with the stacked Peltier devices are reversed, the temperature of the two heat conducting insulating plates of the stacked Peltier devices is in the same direction. become. Therefore, the plurality of stacked Peltier elements enhance the temperature control ability of each other, so that the temperature control ability of the auxiliary Peltier element is increased. As a result, the laser constituted by the main Peltier element, the heat conducting tube, and the auxiliary Peltier element The temperature control capability of the diode temperature control module itself is increased, so that the temperature control of the laser diode can be performed more accurately.

The description of the structure and the temperature control capability of the laser diode temperature control module according to the present invention has been completed. The driving method of the laser diode temperature control module according to the present invention will be described below. FIG. 5 shows a drive circuit (No. 1) for the main Peltier element and the auxiliary Peltier element, which corresponds to a method of determining the operation of the auxiliary Peltier element with reference to the temperature of the laser diode, and controls the temperature control module by software. It is supposed to be performed in the following.

In FIG. 5, reference numeral 7 denotes a main Peltier element (in the figure, the Peltier element is represented by an abbreviation "TEC" with an acronym of "Thermal Electric Controller". Hereinafter, the same applies in the figure), and reference numeral 7a denotes an auxiliary Peltier element. The main Peltier element 7 and the auxiliary Peltier element 7a are thermally connected. Here, it does not matter whether the auxiliary Peltier element 7a is constituted by a single Peltier element or a plurality of Peltier elements laminated.

Reference numeral 8 denotes a driver for driving the main Peltier element 7 (in the figure, "TEC DRV".
In the figure, they are similarly described. ), 8a are auxiliary Peltier elements 7
a, a thermistor 5 which is in thermal contact with the main Peltier element 7 and outputs the temperature information of the laser diode as an analog quantity; and 10, a digital quantity which converts the analog temperature information output by the thermistor 5 into a digital quantity. The analog / digital converter to be converted (Analog Digital Converter in the figure)
"A / D" is abbreviated using a part of initials. Hereinafter, the same description is used in the drawings. ) And 11 are a central processing unit (abbreviated as “CPU” in the figure.
l Abbreviation for Processing Unit. ), 1
2 is a bus of the central processing unit 11, and 13 is a random access memory for temporarily storing programs and data.
A memory (abbreviation “RAM” with an acronym of Random Access Memory is described in the figure. Hereinafter, the same is described in the figure), a read-only memory (ROM in the figure) for storing programs and setting data This is an abbreviation using an acronym for Read Only Memory. Hereinafter, the description is similarly given in the figures.) And 15 are input / output interfaces (in the figure, a partial abbreviation of Input Output Interface is used). This is abbreviated as “I / O.” Hereinafter, the description is similarly given in the figure.) 9 is a digital-analog converter (“D / A” in the figure) that supplies a control amount corresponding to the drive current to the driver 8. This is Digital An
This is an abbreviation of alog Converter with some initials. Hereinafter, the same description is used in the drawings. ) And 9a are digital / analog converters for supplying a control amount corresponding to the drive current to the driver 8a.

In the configuration shown in FIG. 5, the thermistor 5 is in thermal contact with the main Peltier element 7 and outputs the temperature information of the laser diode in an analog amount. The analog-to-digital converter 10 converts the analog output of the thermistor 5 into a digital quantity and supplies the digital quantity via the input / output interface 15 to the central processing unit. The central processing unit 11 stores the temperature information in the random access memory 13, refers to the temperature information, and reads the current to be supplied to the main Peltier element 7 and the auxiliary Peltier element 7a corresponding to the temperature in a read-only memory. 14, and supplies the digital / analog converter 9 and the digital / analog converter 9 a via the input / output interface 15. The driver 8 supplies a driving current to the main Peltier element 7 in accordance with the output of the digital / analog converter 9, and the driver 8a supplies a driving current to the auxiliary Peltier element 7a in accordance with the output of the digital / analog converter 9a. Supply.

FIG. 6 shows a driving method (part 1) of the main Peltier element and the auxiliary Peltier element, and shows a driving method corresponding to the configuration of FIG. Hereinafter, description will be made along the reference numerals in FIG. M1. The designer or the operator of the optical communication system inputs in advance the initial current initially supplied to the main Peltier element, the specified temperature for operating the auxiliary Peltier element, and the constant current supplied when operating the auxiliary Peltier element. _{Let the} prescribed temperature be T _S.

M2. In addition, the designer or the operator of the optical communication system inputs a current value to be supplied to the main Peltier element corresponding to the temperature of the laser diode. The following is the processing operation by the configuration of FIG. S1. The central processing unit turns on the main Peltier device. At this time, the initial current set in step M1 is supplied.

This is because the central processing unit reads the initial current from the read-only memory, supplies the initial current to the digital-to-analog converter via the input / output interface, and responds to the output of the digital-to-analog converter to drive the main Peltier element driver. Is executed by driving the main Peltier element. S2. Measure the temperature of the laser diode. Let the measured temperature be T _L.

This corresponds to the laser output from the thermistor 5.
This is performed by the analog-to-digital converter converting the temperature information corresponding to the temperature of the diode into a digital signal and supplying the digital signal to the central processing unit. S4. It determines whether the measured temperature T _L exceeds the prescribed temperature T _S. S5. In step S4, in a case where the measured temperature T _L is determined to exceed the predetermined temperature T _S (Yes), to turn on the auxiliary Peltier element.

S6. A constant current is supplied to the auxiliary Peltier device. This is performed by a process similar to the driving of the main Peltier element in step S1. S7. In step S4, if the measured temperature T _L is determined not to exceed the specified temperature T _S (No) turns off the auxiliary Peltier element.

Actually, since the auxiliary Peltier element is off at the beginning when the drive circuit of the temperature control module is driven, the off state may be continued. On the other hand, when the auxiliary Peltier element can be stopped after the auxiliary Peltier element is once turned on, the auxiliary Peltier element is turned off in this step. S8. The current corresponding to the temperature _TL measured in step S2 is read from the read-only memory, and S9. Update the current of the main Peltier device.

Thereafter, the laser beam of step S2 is periodically
The temperature of the diode is measured, and the processing of steps S4 to S9 is repeated according to the measured temperature. FIG.
7A and 7B are diagrams for explaining a driving method of a main Peltier element and an auxiliary Peltier element (part 1). FIG. 7A shows a temperature change of a laser diode, FIG. 7B shows a driving current of an auxiliary Peltier element, and FIG. (C) shows the drive current of the main Peltier element. In each case, the horizontal axis is time.

In FIG. 7A, it is assumed that the temperature of the laser diode is T ₁ at time 0, and exceeds the temperature T ₂ at which the auxiliary Peltier element is to be operated in the cooling mode. Then, at the temperature T _1, the main Peltier device shall operate at a maximum current of cooling mode. Thus, a constant current I _A is supplied to the time 0 in the auxiliary Peltier element as shown in FIG. 7 (b). The main Peltier element is operated with a maximum current I _1.

The temperature of the laser diode drops because both the main Peltier element and the auxiliary Peltier element operate to cool the laser diode. However, here, the temperature of the laser diode keeps T ₁ until time t ₁ , Indeed the temperature of the laser diode is lowered from time t _1, it is assumed that a constant temperature T ₃ at time t _3, and which pass the specified temperature T _S at time t _2.

Therefore, as shown in FIG. 7C, the main Peltier element operates at the maximum current I ₁ until time t _1, and the drive current of the main Peltier element decreases after time t ₁ . On the other hand, the temperature of the laser diode at time t ₂ since below a specified temperature T _S, as shown in FIG. 7 (b), the auxiliary Peltier element at time t ₂ is turned off. Therefore, the time t ₂ subsequent to cool the laser diode only main Peltier element. Incidentally, the driving current of the main Peltier element at time t ₂ and I _2.

Since the temperature of the laser diode becomes constant after time t ₃ , the drive current of the main Peltier element also maintains a constant current I ₃ . FIG. 8 is a diagram (part 2) for explaining a driving method of the main Peltier element and the auxiliary Peltier element.
FIG. 3 illustrates the relationship between the drive currents of the main Peltier element and the auxiliary Peltier element and the temperature of the laser diode. Therefore, the vertical axis represents current, and the horizontal axis represents temperature.

Actually, this figure can be created from FIGS. 7 (a), 7 (b) and 7 (c). That is, current of the main Peltier element when the temperatures T ₁ is the maximum current I _1, the current of the auxiliary Peltier element is constant current I _A. When the temperature reaches the specified temperature T _S , the auxiliary Peltier element is turned off, so that the current becomes 0. When the temperature is T _S , the current of the main Peltier element is I ₂ . And the temperature is T
Current of the main Peltier element when it is ₂ is I _3. Therefore, current to the temperature of the main Peltier element is constant at the maximum current is at a temperature above T _1, the change in current of the main Peltier device is less than temperature T ₁ of the obtained if connecting the points mentioned above. Then, if it is extrapolated, it will eventually become a negative current. This means that the temperature of the laser diode will decrease and will need to be warmed up. And
The direction of the current of the main Peltier element can be reversed in order to warm the element. This means is well known and will not be described in detail here.

That is, by the above processing, when the measured temperature of the laser diode exceeds the set temperature, a specified drive current is supplied to the auxiliary Peltier element, and the main Peltier element is set in accordance with the measured temperature. Since a certain drive current is supplied, the temperature control capability of the temperature control module of the laser diode is enhanced, and the temperature of the laser diode can be accurately controlled.

On the other hand, when the temperature of the laser diode is within the set temperature, no driving current is supplied to the auxiliary Peltier element, and the driving current set corresponding to the measured temperature is supplied to the main Peltier element. Is supplied, the laser diode temperature control can be performed while reducing the drive power of the laser diode temperature control module. FIG. 9 shows a drive circuit (part 2) for the main Peltier element and the auxiliary Peltier element, which corresponds to a method for determining the operation of the auxiliary Peltier element by measuring the drive current of the main Peltier element in addition to the temperature of the laser diode. It is assumed that the control of the temperature control module is performed by software.

In FIG. 9, 7 is a main Peltier element, 7a
Is an auxiliary Peltier element, and the main Peltier element 7 and the auxiliary Peltier element 7a are thermally connected. 8 is a driver for driving the main Peltier element 7; 8a is a driver for driving the auxiliary Peltier element 7a; 5 is a thermistor which is in thermal contact with the main Peltier element 7 and outputs temperature information of the laser diode in an analog amount; An analog-to-digital converter 10 converts an analog amount of temperature information output from the thermistor 5 into a digital amount, and an analog-to-digital converter 10a converts an analog amount of current information of the main Peltier element output from the driver 8 into a digital amount. 12 is a bus of the central processing unit 11, 13 is a random access memory for temporarily storing programs and data, 14 is a read-only memory for storing programs and setting data, 15 is an input / output interface, 9 is a driver 8 -To-analog converter that supplies a control amount corresponding to the drive current to the 9a is a digital-to-analog converter for supplying a control amount corresponding to the driving current to the driver 8a.

Also in the configuration of FIG. 9, the thermistor 5 is in thermal contact with the main Peltier element 7 and outputs the temperature information of the laser diode in an analog amount. The analog-to-digital converter 10 converts the analog output of the thermistor 5 into a digital quantity and supplies the digital quantity via the input / output interface 15 to the central processing unit. On the other hand, the driver 8 outputs drive current information of the main Peltier element in an analog amount. The analog output of the driver 8 is converted to an analog / digital converter 10a.
Are converted into digital quantities and supplied to the central processing unit via the input / output interface 15. Central processing unit 1
1 stores the temperature information and the current information in the random access memory 13, refers to the temperature information and the current information, and supplies the information to the main Peltier element 7 and the auxiliary Peltier element 7a according to the temperature. The current is read from the read-only memory 14 and supplied to the digital / analog converter 9 and the digital / analog converter 9a via the input / output interface 15. The driver 8 is connected to the main Peltier device 7 in accordance with the output of the digital / analog converter 9.
And a driver 8a supplies a driving current to the auxiliary Peltier element 7a in accordance with the output of the digital / analog converter 9a.

FIG. 10 shows a driving method (part 2) of the main Peltier element and the auxiliary Peltier element, which corresponds to the configuration of FIG. Hereinafter, description will be made along the reference numerals in FIG. still,
Actually, the processing in FIG. 10 is similar to the processing in FIG. 6, but it is considered difficult to understand only the changed parts in FIG.

M1. In advance, the designer or the operator of the optical communication system operates an initial current initially supplied to the main Peltier element, a specified temperature for operating the auxiliary Peltier element, a specified current of the main Peltier element for operating the auxiliary Peltier element, and operating the auxiliary Peltier element. Input a constant current to be supplied when making it. The specified temperature is T _S and the specified current is I _S. M2. In addition, the designer or the operator of the optical communication system inputs a current value to be supplied to the main Peltier element corresponding to the temperature of the laser diode.

The following is the processing operation by the configuration of FIG. S1. The central processing unit turns on the main Peltier device. At this time, an initial current is supplied. This is because the central processing unit reads the initial current from the read-only memory, supplies it to the digital-to-analog converter via the input / output interface, and the driver of the main Peltier element corresponds to the output of the digital-to-analog converter. This is performed by driving the element.

S2. Measure the temperature of the laser diode. Let the measured temperature be T _L. This is performed by the analog-to-digital converter converting the temperature information corresponding to the temperature of the laser diode output by the thermistor 5 into digital data and supplying the digital data to the central processing unit. S3. The drive current of the main Peltier device is measured. The measured current and I _T.

This is performed by the analog-to-digital converter converting the current information corresponding to the current of the main Peltier element output from the driver 8 into a digital signal and supplying it to the central processing unit. S4. Whether the measured temperature T _L exceeds the prescribed temperature T _S, it is determined whether the measured current I _T exceeds the specified current I _S, determines whether at least one of which is true.

S5. In step S4, when it is determined that either the measured temperature _TL exceeds the specified temperature T _S or the measured current exceeds the specified current is true (Ye
In s), the auxiliary Peltier device is turned on. S6. A constant current is supplied to the auxiliary Peltier device. This is performed by a process similar to the driving of the main Peltier element in step S1.

S7. In step S4, if the measured temperature T _L exceeds the prescribed temperature T _S, or none of the measured current exceeds a specified current is determined not to be true (N
In o), the auxiliary Peltier device is turned off. actually,
Since the auxiliary Peltier element is off at the beginning when the drive circuit of the temperature control module is driven, the off state may be continued. On the other hand, when the auxiliary Peltier element can be stopped after the auxiliary Peltier element is once turned on, the auxiliary Peltier element is turned off in this step.

S8. The current corresponding to the temperature _TL measured in step S2 is read from the read-only memory, and S9. Update the current of the main Peltier device. Thereafter, the temperature of the laser diode is periodically measured in step S2, and steps S4 to S4 are performed in accordance with the measured temperature.
Step 9 is repeated.

According to the above processing, when the measured temperature of the laser diode exceeds the set temperature or when the drive current of the main Peltier element exceeds the maximum current, the specified drive current is supplied to the auxiliary Peltier element. Since the main Peltier element is supplied with a drive current set according to the measured temperature, the temperature control capability of the laser diode temperature control module is increased, and the temperature of the laser diode can be accurately controlled. Can be.

On the other hand, when the measured temperature of the laser diode is lower than the set temperature and the driving current of the main Peltier element is lower than the maximum current, no driving current is supplied to the auxiliary Peltier element and the main Peltier element is not supplied. Since the drive current set according to the measured temperature is supplied, the temperature of the laser diode can be controlled while reducing the drive power of the temperature control module for the laser diode.

Further, since the above determination is made based on both the measured drive current and the measured temperature, it is possible to avoid the danger that the auxiliary Peltier element will not be driven when it should be driven due to an error in the measured temperature, for example. The above is a description of a driving method for driving the temperature control module of the laser diode in a software manner. However, a driving method for driving the temperature control module of the laser diode with hardware is also possible.

FIG. 11 shows a drive circuit (part 3) for the main Peltier element and the auxiliary Peltier element, and also shows an automatic power control circuit for keeping the output power of the laser diode constant. In FIG. 11, reference numeral 5 denotes a thermistor (abbreviated as "TH" in the figure) for detecting the temperature of the laser diode and outputting a voltage, and reference numeral 16 denotes a first reference for a voltage corresponding to the reference temperature of the laser diode. A voltage source 17 is an automatic temperature control circuit that outputs a control voltage for controlling the temperature of the laser diode with a voltage that is the difference between the voltage output by the thermistor 5 and the voltage of the reference voltage source 16. A driver for supplying a drive current corresponding to the output control voltage to the main Peltier element, a main Peltier element for controlling the temperature of the laser diode driven by a current supplied from the driver, and a voltage for outputting a voltage outputted from the thermistor; The detection circuit 8a outputs a signal of a specified logic level when the voltage exceeds a specified voltage. 8a indicates that the detection circuit 18 outputs a signal of a specified logic level. Auxiliary Peltier elements to the provision of current supplied driver when the symptoms, laser and 7a is driven by the current driver 8a is supplied
An auxiliary Peltier element for controlling the temperature of the diode. The driving circuit of the temperature control module for the laser diode is constituted by the above components. The main Peltier element 7
The auxiliary Peltier element 7a is thermally connected.

4 is a temperature controlled laser diode. Reference numeral 19 denotes a photo diode for electrically converting the back light of the laser diode 4, reference numeral 20 denotes a second reference voltage source of a voltage corresponding to the reference level of the output of the laser diode 4, and reference numeral 21 denotes an output voltage of the photo diode 19 and An automatic power control circuit for outputting a control voltage for power control of the laser diode with a voltage difference between the voltages of the reference voltage source 20. A drive current 22 corresponding to the control voltage output from the automatic power control circuit 21 is supplied to the laser diode. 4 controls the output power of the laser diode by a negative feedback loop constituted by the above components.

In the configuration shown in FIG. 11, the automatic power control circuit is not operated when the power is turned on, but the automatic temperature control circuit 17 and the detection circuit 18 are enabled to keep the temperature of the laser diode 4 constant. This is because, when the temperature of the laser diode 4 is abnormally high at the beginning of the power supply, when the output power is controlled to a predetermined value by the automatic power control, an excessive drive current is supplied to the laser diode 4, and
This is to avoid a possibility that the diode 4 may be broken or damaged.

Thereafter, while the automatic temperature control circuit 17 and the detection circuit 18 continue to control the temperature of the laser diode 4, the automatic power control circuit 21
Is continuously controlled to a predetermined power. here,
The laser performed by the automatic temperature control circuit 17 and the detection circuit 18
The temperature control of the diode 4 is as follows. That is, the automatic temperature control circuit 1 detects the difference between the voltage corresponding to the temperature of the laser diode detected by the thermistor 5 and the reference voltage.
7 controls the drive current of the main Peltier element.

On the other hand, when the voltage corresponding to the temperature of the laser diode detected by the thermistor 5 exceeds the voltage corresponding to the specified temperature, the detection circuit 18 drives the driver 8a, and the driver 8a supplies the specified current to the auxiliary Peltier. Element 7
When the voltage corresponding to the temperature of the laser diode detected by the thermistor 5 does not exceed the voltage corresponding to the specified temperature, the detection circuit 18 does not drive the driver 8a.

In this case, the detection circuit 18 compares the output voltage of the thermistor 5 with the reference voltage, and
May be configured by a comparator that outputs a signal of a prescribed logic level when the output voltage of the second comparator exceeds the reference voltage. The above operation is performed both when the automatic power control circuit 21 is operating and when the operation is stopped.

By this operation, when the measured temperature of the laser diode exceeds the set temperature, a prescribed drive current is supplied to the auxiliary Peltier element, and the drive set to the main Peltier element corresponding to the measured temperature is supplied. Since the current is supplied, the temperature control capability of the laser diode temperature control module is increased, and the temperature of the laser diode can be accurately controlled.

On the other hand, when the temperature of the laser diode is lower than the set temperature, no driving current is supplied to the auxiliary Peltier element, and the driving current set corresponding to the measured temperature is supplied to the main Peltier element. Is supplied, it is possible to control the temperature of the laser diode while reducing the driving power of the temperature control module for the laser diode. The configuration in FIG. 11 is an example in which the detection circuit 18 is operated only with the temperature information of the laser diode detected by the thermistor 5. It is also effective to drive the auxiliary Peltier element including whether or not the current exceeds a specified current.

In this case, the driver 8 is added to the configuration of FIG.
Analog drive that detects the drive current of the
A digital converter is provided, and the detection circuit 18 includes a thermistor 5
And a first comparator that outputs a signal of a specified logic level when the output voltage of the thermistor 5 exceeds the reference voltage, and the output voltage of the analog-to-digital converter determines the reference voltage. What is necessary is just to comprise the 2nd comparator which outputs the signal of the predetermined | prescribed logic level when exceeding, and the OR circuit which performs the OR operation of the output of this 1st comparator, and the output of this 2nd comparator.

Thus, when the temperature of the laser diode exceeds the specified temperature or when the driving current of the main Peltier element exceeds the maximum current, the specified driving current is supplied to the auxiliary Peltier element, and the main Peltier element is supplied. Since a drive current corresponding to the measured temperature is supplied to the element, the temperature control capability of the laser diode temperature control module is increased,
The temperature of the laser diode can be accurately controlled.

On the other hand, when the temperature of the laser diode is lower than the specified temperature and the driving current of the main Peltier element is lower than the maximum current, no driving current is supplied to the auxiliary Peltier element.
Since a drive current corresponding to the temperature of the laser diode 4 is supplied to the main Peltier element, the drive power of the laser diode temperature control module is reduced while the laser power is reduced.
The temperature of the diode can be controlled.

Further, since the above determination is made based on both the driving current of the main Peltier element and the temperature of the laser diode, it is possible to avoid the danger that the auxiliary Peltier element will not be driven when it should be driven.

[0115]

As described above in detail, according to the present invention, it is possible to realize a temperature control module for a laser diode having a high temperature control capability and a drive system suitable for a temperature control module having a high temperature control capability. That is, according to the first aspect, the heat conductive insulating plate of the main Peltier element with which the laser diode is in thermal contact with one of the auxiliary Peltier elements has good thermal conductivity. Thermally connected by the heat conducting tube, the heat conducting insulating plate of the main Peltier device in thermal contact with the laser diode and the heat conducting insulating plate of the auxiliary Peltier device in contact with the heat conducting tube The temperature difference with the plate becomes smaller.

In addition, the heat conducting insulating plate of the main Peltier element that is in thermal contact with the laser diode and the heat conducting insulating plate of the auxiliary Peltier element that is in thermal contact with the heat conducting cylinder Since the same thermal properties are provided, the laser diode is in thermal contact with the heat conducting cylinder when the heat conducting insulating plate of the main Peltier element is in thermal contact with the heat conducting cylinder. The heat conducting insulating plate of the auxiliary Peltier element is also on the low temperature side, and when the heat conducting insulating plate of the main Peltier element with which the laser diode is in thermal contact is on the high temperature side, heat is applied to the heat conducting cylinder. The thermally conductive insulating plate of the auxiliary Peltier element that is in contact with the substrate is also on the high temperature side.

Therefore, when the laser diode needs to be cooled, the cooling capacity is increased, and when it is necessary to increase the temperature of the laser diode, the temperature increasing ability is increased, so that the temperature control of the laser diode can be accurately performed. It is possible to do. Further, according to the second invention, in the laser diode temperature control module of the first invention, a plurality of Peltier elements are stacked to constitute the auxiliary Peltier element, which is thermally connected by the heat conducting tube. Since the thermal conductivity of the heat conducting insulating plate of the main Peltier element and the heat conducting insulating plate of the auxiliary Peltier element are made the same, the auxiliary Peltier element performs temperature control in the same direction as the main Peltier element.

In addition, since the thermal properties of the heat conducting insulating plates in which the stacked Peltier devices are in contact with each other are reversed, the temperature of the two heat conducting insulating plates of the stacked Peltier devices is in the same direction. become. Therefore, the plurality of stacked Peltier elements enhance the temperature control ability of each other, so that the temperature control ability of the auxiliary Peltier element is increased. As a result, the laser constituted by the main Peltier element, the heat conducting tube, and the auxiliary Peltier element The temperature control capability of the diode temperature control module itself is increased, so that the temperature control of the laser diode can be performed more accurately.

According to the third aspect of the present invention, when the measured temperature of the laser diode exceeds the set temperature, a specified drive current is supplied to the auxiliary Peltier element, and the main Peltier element is adapted to the measured temperature. Since the preset drive current is supplied, the temperature control capability of the laser diode temperature control module is enhanced, and the temperature of the laser diode can be accurately controlled.

On the other hand, when the temperature of the laser diode is within the set temperature, no drive current is supplied to the auxiliary Peltier element, and the drive current set in accordance with the measured temperature is supplied to the main Peltier element. Is supplied, it is possible to control the temperature of the laser diode while reducing the driving power of the temperature control module for the laser diode.

According to the fourth invention, when the measured temperature of the laser diode exceeds the set temperature or when the drive current of the main Peltier element exceeds the maximum current, the drive specified in the auxiliary Peltier element is performed. Since the current is supplied and the main Peltier element is supplied with a drive current set in accordance with the measured temperature, the temperature control capability of the laser diode temperature control module is increased, and the temperature of the laser diode can be accurately measured. Can be controlled.

On the other hand, when the measured temperature of the laser diode is lower than the set temperature and the driving current of the main Peltier element is lower than the maximum current, no driving current is supplied to the auxiliary Peltier element, and the main Peltier element is not supplied. Since the drive current set in accordance with the measured temperature is supplied, the laser diode temperature control can be performed while reducing the drive power of the laser diode temperature control module.

Further, since the above determination is made based on both the measured drive current and the measured temperature, it is possible to avoid the danger that the auxiliary Peltier element will not be driven when it should be driven. Further, according to the fifth invention, an automatic temperature control circuit for controlling the drive current of the main Peltier element based on the difference between the voltage corresponding to the detected temperature of the laser diode and the reference voltage, and at least the detected laser diode A detection circuit that outputs a control signal to supply a specified drive current to the auxiliary Peltier element when the temperature of the laser diode exceeds the specified temperature is provided. In the case of exceeding, the specified driving current is supplied to the auxiliary Peltier element, and the driving current corresponding to the temperature of the laser diode is supplied to the main Peltier element, so that the temperature control capability of the laser diode temperature control module is increased, The temperature of the laser diode can be accurately controlled.

On the other hand, when at least the temperature of the laser diode is within a specified temperature, no driving current is supplied to the auxiliary Peltier element, and a driving current corresponding to the temperature of the laser diode is supplied to the main Peltier element. Therefore, it is possible to control the temperature of the laser diode while reducing the driving power of the temperature control module for the laser diode.

[Brief description of the drawings]

FIG. 1 is a first embodiment (cross-sectional view) of a temperature control module according to the present invention.

FIG. 2 is a first embodiment (perspective view) of the temperature control module of the present invention.

FIG. 3 is a structural example of a heat conduction cylinder.

FIG. 4 is a second embodiment (sectional view) of the temperature control module of the present invention.

FIG. 5 is a diagram illustrating a drive circuit (part 1) of a main Peltier element and an auxiliary Peltier element.

FIG. 6 shows a method of driving a main Peltier element and an auxiliary Peltier element (part 1).

FIG. 7 is a view for explaining a driving method of a main Peltier element and an auxiliary Peltier element (part 1).

FIG. 8 is a diagram (part 2) illustrating a driving method of the main Peltier element and the auxiliary Peltier element.

FIG. 9 shows a drive circuit (part 2) for the main Peltier element and the auxiliary Peltier element.

FIG. 10 shows a method of driving a main Peltier element and an auxiliary Peltier element (part 2).

FIG. 11 shows a drive circuit (part 3) for the main Peltier element and the auxiliary Peltier element.

FIG. 12 shows a conventional basic temperature control module.

FIG. 13 is a diagram showing a limit of cooling by a Peltier element.

FIG. 14 shows the principle of cooling / heating by a Peltier element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Peltier element 1-1 P-type thermoelectric semiconductor 1-2 N-type thermoelectric semiconductor 1-3, 1-4, 1-5 Metal electrode 1-6, 1-7 Heat conductive insulating plate 1-8 Thermoelectric semiconductor part 1a Peltier element 1-1a P-type thermoelectric semiconductor 1-2a N-type thermoelectric semiconductor 1-3a, 1-4a, 1-5a Metal electrode 1-6a, 1-7a Heat conductive insulating plate 1-8a Thermoelectric semiconductor part 1b Peltier element 1-1b P-type thermoelectric semiconductor 1-2b N-type thermoelectric semiconductor 1-3b, 1-4b, 1-5b Metal electrode 1-6b, 1-7b Heat conductive insulating plate 1-8b Thermoelectric semiconductor unit 2, 2a Heat sink 3 Kovar plate 4 Laser diode 5 Thermistor 6 Heat conduction cylinder 6-1 Hole 7 Main Peltier element 7a Auxiliary Peltier element 8, 8a Driver 9, 9a Digital / analog converter 10, 10a Analog / digital converter 11 Central processing Unit 12 Bus 13 Random access memory 14 Read only memory 15 Input / output interface 16 First reference voltage source 17 Automatic temperature control circuit 18 Detection circuit 19 Photodiode 20 Second reference voltage source 21 Automatic power control circuit 22 Driver 23 batteries

Claims (5)

[Claims] A heat conductive insulating plate of a main Peltier element, which is in thermal contact with a laser diode, and one heat conductive insulating plate of an auxiliary Peltier element different from the main Peltier element have good thermal conductivity. Thermally connected by a heat conducting tube, the heat conducting insulating plate of the main Peltier device being in thermal contact with the laser diode, and the heat conducting insulating plate of the auxiliary Peltier device being in thermal contact with the heat conducting tube. A temperature control module for a laser diode, characterized in that the heat conducting insulating plate has the same thermal properties. 2. The laser diode temperature control module according to claim 1, wherein the auxiliary Peltier element is formed by laminating a plurality of Peltier elements, and the main Peltier element is thermally connected by the heat conducting tube. The thermal characteristics of the heat conductive insulating plate and the thermal conductive insulating plate of the auxiliary Peltier device are made the same, and the thermal characteristics of the heat conductive insulating plates in contact with each other of the stacked Peltier devices are reversed. Laser diode temperature control module. 3. The driving method of a temperature control module for a laser diode according to claim 1, wherein the auxiliary Peltier element is provided when a measured temperature of the laser diode exceeds a set temperature. A driving current is supplied to the auxiliary Peltier element when the temperature of the laser diode is within a set temperature, and in any case, the measured temperature is supplied to the main Peltier element. A drive method for a laser diode temperature control module, characterized in that a drive current set in accordance with (1) is supplied. 4. The driving method of a laser diode temperature control module according to claim 1, wherein the measured temperature of the laser diode exceeds a set temperature, or When the drive current of the Peltier element exceeds the maximum current, a specified drive current is supplied to the auxiliary Peltier element. When the measured temperature of the laser diode is lower than the set temperature and the drive current of the main Peltier element is lower than the maximum current. Supplying a driving current to the auxiliary Peltier element in any case, and supplying a driving current set in accordance with the measured temperature to the main Peltier element in any case. Driving method of temperature control module. 5. A method for driving a temperature control module for a laser diode according to claim 1, wherein a difference between a voltage corresponding to the detected temperature of the laser diode and a reference voltage. An automatic temperature control circuit for controlling the drive current of the main Peltier element, and supplying a specified drive current to the auxiliary Peltier element at least when detecting that the temperature of the laser diode exceeds a specified temperature. And a detection circuit for outputting a control signal for the temperature control module of the laser diode.