JPS628625A - Optical transmitter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical transmission device that can be used as a trace source and can be used even under adverse conditions including humidity and dust.

Prior Art A conventional example is shown in FIG. In the conventional example, there is no means for heating or cooling the semiconductor laser 1, and therefore, the usable temperature range of the optical transmission device is determined by the semiconductor laser 1. Since the optical transmission device includes a heating element 2 such as an amplifier, the temperature of the casing of the optical transmission device and its interior becomes higher than the outside temperature. Therefore, in order to widen the usable temperature range of the optical transmission device, in the conventional example, the semiconductor laser 1 is mounted in the position with the highest heat dissipation efficiency in the housing 3, that is, on the bottom surface of the housing 3. The temperature difference between the casing 3 or the difference between the temperature of the semiconductor laser 1 and the outside air temperature is made as small as possible to bring the outside air temperature at which the optical transmission device can be used as close to the allowable operating temperature of the semiconductor laser 1 as possible.

In such a conventional example, since the operating temperature of the semiconductor laser 1 changes depending on the outside temperature, its operating characteristics also change, and therefore the characteristics as an optical transmission device also change, but as long as digital transmission is performed, the temperature range is within a predetermined temperature range. Sufficient transmission characteristics have been obtained within the range.

Note that in the conventional example shown in FIG. Communication Society National Conference 2212.

2213.2214).

Problems to be Solved by the Invention In such conventional techniques, since the operating temperature of the semiconductor laser changes depending on the outside temperature, its operating characteristics also change. As long as digital transmission is performed, the influence of such changes in operating characteristics is small, but when analog transmission is performed, the influence is large, and therefore stable and high-quality transmission cannot be achieved. Furthermore, in the conventional technology, the allowable operating temperature of the semiconductor laser determines the outside temperature at which the optical transmission device can be used, but it is impossible to use it under severe conditions, for example outdoors.

Furthermore, depending on the outside temperature, even if the semiconductor laser is below its allowable operating temperature, it may be operated at a relatively high temperature, which poses a risk of shortening its lifespan.

Means for Solving the Problems In order to solve these problems, the present invention provides a temperature sensor that detects the temperature of a semiconductor laser, and a first signal generator that generates a signal for setting the temperature of the semiconductor laser. The vessel and
An amplifier that outputs a signal according to the difference between the signal from the temperature sensor and the signal from the first signal generator, an electrothermal conversion element that heats or cools the semiconductor laser according to the signal from this amplifier, and operates a fan. a second signal generator that generates a signal for specifying a state to be set, a comparator that changes the output signal based on the difference between the signal from the amplifier and the signal from the second signal generator, and this comparator It is equipped with a fan whose operation is controlled by signals from the electrothermal conversion element and which sends air to the heat dissipation section of the electrothermal conversion element.

Function: As configured above, the present invention detects the temperature of the semiconductor laser with a temperature sensor, and sends a signal to the electrothermal conversion element, that is, a current, so that the temperature becomes the value set by the first signal generator. Since the size is controlled, the temperature of the semiconductor laser can be kept constant even if the outside temperature changes somewhat. Therefore,
By setting the temperature at which the semiconductor laser has low noise and low distortion, stable and high-quality analog transmission can be achieved within that temperature range.

Embodiment FIG. 1 shows a configuration for bringing a semiconductor laser to a set temperature in an outdoor optical transmission device of the present invention. The temperature of semiconductor laser 8 is detected by temperature sensor 9 . A signal corresponding to the difference between the signal from temperature sensor 9 and the signal from temperature setting circuit 1o is output from amplifier circuit 11. The drive circuit 12 outputs a current corresponding to the signal from the amplifier circuit 11 to drive the electrothermal conversion element 13. The electrothermal conversion element 13 is 2
It has surfaces, and when an electric current is applied, one side is cooled and the other side is heated, and when the direction of the current is reversed, the cooled side and the heated side alternate. This electrothermal conversion element 13 is connected to the drive circuit 7
The temperature of the semiconductor laser 8, which cools or heats the cooling plate 14 first, follows the temperature of the cooling plate 14 by the current from the 0-wavelength current. Further, in order to efficiently heat or cool the semiconductor laser 8, the semiconductor laser 8. Cooling plate 1
The electrothermal conversion element 13 is surrounded by 4°. Furthermore, when the electrothermal conversion element 13 is used to cool the surface on the semiconductor laser 8 side, for example, the surface on the housing 16 side is heated, but in order to efficiently cool the surface on the semiconductor laser 8 side, the housing 16 Although it is necessary to sufficiently dissipate heat from the side surfaces, this is done directly by the casing 16.

In this way, the temperature of the semiconductor laser 8 is set to a temperature corresponding to the signal from the temperature setting circuit 1o.

Furthermore, even if the temperature of the housing 16 increases due to an increase in outside temperature or irradiation with sunlight, in order to maintain the semiconductor laser 8 at the set temperature, a large current is applied to the electrothermal conversion element 13, that is, the drive circuit It is necessary to add a large signal to 12. However, if the outside air temperature becomes too high and the temperature of the housing 16 becomes too high, the semiconductor laser 8 may not be able to reach the set temperature even if a large signal is output from the amplifier circuit 11.

This is because the electrothermal conversion element 13 creates a temperature difference between its two surfaces by passing an electric current through it.
It does not mean that the temperature difference will become any larger just because a large amount of current is passed.The more current that is passed, the more Joule heat generated in the electrothermal conversion element 13 increases, and the larger the temperature difference, the more the electrothermal conversion element 13 increases. As more heat flows in or out through 13, there is a limit to the temperature difference. Therefore, if the temperature of the housing 16 becomes high and the difference from the set temperature of the semiconductor laser 8 exceeds the above-mentioned limit,
The temperature of the semiconductor laser 8 changes depending on the temperature of the housing 1e or the outside temperature.

To prevent this, it is possible to detect that the signal from the amplifier circuit 11 approaches the limit signal for achieving the above-mentioned limit temperature, and operate the fan to lower the temperature of the casing. In the embodiment of the present invention, the reference signal generating circuit 18 outputs a signal that is somewhat smaller than the limit signal from the amplifier circuit 11.
This signal and the signal from the amplifier circuit 11 are input to the comparison circuit 19, and it is determined whether the signal from the amplifier circuit 11 is close to the limit signal. 17 to lower the temperature of the housing 16. By providing such a fan 20 or the like, the semiconductor laser 8 can be kept at a preset temperature over a wider range of outside temperatures, etc., than in the case without the fan 20 or the like.

In the above example, the output of the amplifier circuit 11 was used to determine whether to operate the fan, but any signal corresponding to the output signal of the amplifier circuit 11 may be used, and the output current of the drive circuit 12, that is, the electrothermal conversion element It is also possible to use a current of 13, and if this current becomes larger than a certain value, the fan 2o may be activated.

The electrothermal conversion element can heat or cool the semiconductor laser by its input current, and as a result, there is a difference between the temperature of the semiconductor laser and the ambient temperature as 0 ambient source temperature.
The temperature of the casing in which the semiconductor laser is mounted and the outside air temperature are considered, but since the casing also includes a heating element such as an amplifier, the casing temperature is always higher than the outside air temperature. Therefore, the difference between the temperature of the semiconductor laser and the outside temperature is smaller than the difference between the temperature of the semiconductor laser and the housing. These temperature differences can be increased by increasing the input current, but there is a limit due to the Joule heat generated by the electrothermal conversion element itself or the inflow and outflow of heat through the electrothermal conversion element. If the difference between the set temperature of the semiconductor laser and the outside temperature is within the above temperature range, by controlling the current to the electrothermal conversion element, the temperature of the semiconductor laser can be set to the set value regardless of the outside temperature. can.

However, if the outside temperature changes significantly and the difference between the set temperature of the semiconductor laser and the outside temperature exceeds the above temperature range, it is not possible to keep the temperature of the semiconductor laser constant simply by controlling the current to the electrothermal conversion element. .

In the present invention, when this temperature range is about to be exceeded, this is detected by comparing the signal from the amplifier with the signal from the second signal generator using a comparator, and the fan is operated to remove the casing. Air is applied to the body surface to reduce the difference between the temperature of the casing and the outside temperature, bringing the temperature of the casing closer to the outside temperature. As a result, the difference between the temperature of the semiconductor laser and the temperature of the housing becomes smaller, so that the temperature of the housing can be raised to the above temperature range, and the range of usable outside temperatures is expanded. thus,
By operating the fan as in the present invention, the temperature of the semiconductor laser can be kept constant over a wider temperature range.

The structure of the outdoor optical transmission device of the present invention is shown in FIG. A semiconductor laser module 24 that integrates a semiconductor laser, a temperature sensor, an electrothermal conversion element, etc. is attached to the bottom surface of the housing 21, and the housing 21 radiates heat. The housing 21 also includes heating elements 22 and 23 such as amplifiers, and the heat dissipation from these elements is also performed by the housing 21.
temperature will be higher than the outside temperature. Furthermore, when the device of the present invention is used outdoors, the casing 21 may be damaged by irradiation with sunlight 27.
The natural wind 26 causes a temperature drop in the housing 21 and the like. Of course, the temperature of the housing 21 also depends on the outside temperature. Therefore, if the semiconductor laser is directly attached to the housing 21, the temperature of the semiconductor laser will change drastically. However, in the present invention, as described above, a temperature sensor, an electrothermal conversion element, etc. are used to prevent the temperature of the semiconductor laser from changing from the set temperature even if the outside temperature etc. changes somewhat.

Semiconductor lasers easily change their optical output and the amount of noise and distortion generated depending on their operating temperature, but by setting the temperature to a level that provides low noise and low distortion using the present invention, stable and high-quality analog transmission can be achieved. It is possible.

If the outside temperature or the like changes significantly, the temperature of the semiconductor laser will deviate from the set temperature. In the present invention, as described above, in such a case, the fan 26 is operated to send the wind 28 to the surface of the casing 21 on which the semiconductor laser module 24 is attached, thereby eliminating the difference between the temperature of this surface and the outside temperature. Since the temperature is small, it is possible to bring the semiconductor laser to a set temperature using a temperature sensor, an electrothermal conversion element, etc. as described above. With this configuration, the semiconductor laser can be kept at a set temperature over a range wider than the range of the outside temperature, etc., so it can be used even under severe temperature conditions, such as outdoors.

Furthermore, in the present invention, instead of constantly rotating the 71-in 26 to send air to the housing 21, the outside temperature etc. change significantly, making it difficult to control the temperature of the semiconductor laser using the temperature sensor, electrothermal conversion element, etc. Turn on the fan only when necessary. The casing 21 must be completely sealed to prevent moisture, dust, etc. from entering the casing 21. However, a lid is required to open and close the casing 21, and there is inevitably a gap between the lid and the main body of the casing 21, and a connector is required to input and output optical and electrical signals. However, gaps also occur there, and moisture, dust, etc. enter the inside of the casing 21 through these gaps. If the casing 21 is not exposed to air, the temperature of the casing 21 will increase, although the intrusion of moisture, debris, etc. will be small. Therefore, instead of always blowing air with a fan, if you blow air with a fan only when necessary as in the present invention, the temperature of the semiconductor laser can be brought to the same range as when blowing air with a fan all the time. At the same time, it is possible to reduce the intrusion of moisture, dust, etc.

Effects of the Invention The present invention relates to an outdoor optical transmission device, and even when there are slight changes in the outside temperature or sunlight irradiation, the semiconductor laser can be kept at a set temperature, and the semiconductor laser can be kept at a low temperature. Stable and high-quality analog transmission is possible by setting the temperature to ensure low noise and low distortion.

Also, when a fan blows air onto the casing surface, it does not always blow air, but only when the outside temperature becomes too high or when the casing temperature becomes too high. As a result, it is possible to reduce the intrusion of moisture, dust, etc. into the housing, and at the same time, it is possible to keep the temperature of the semiconductor laser constant to the same outside temperature as when air is constantly blown.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an optical transmission device according to an embodiment of the present invention, FIG. 2 is a diagram of a main part of FIG. 1, and FIG. 3 is a diagram of a main part of a conventional optical transmission device. 8... Semiconductor laser, 9... Temperature sensor, 10... Temperature setting circuit, 11...
Amplifier circuit, 12... Drive circuit, 13...
・Electrothermal conversion element, 14...Cooling plate, 15...
...Insulation material, 16...Housing, 17...
・Wind, 18...Reference signal generation circuit, 19...
... Comparison circuit, 20 ... Fan. Name of agent: Patent attorney Toshio Nakao and one other person #I
Figure 2 Figure 3 Figure 42.5

Claims (1)

[Claims] a semiconductor laser, a temperature sensor that detects the temperature of the semiconductor laser, a first signal generator that generates a signal for setting the temperature of the semiconductor laser, a signal from the temperature sensor, and the first signal. means for outputting a signal according to the difference in signals from the generator; an electrothermal conversion element for heating or absorbing heat from the semiconductor laser according to the signal from the output means; and a signal for specifying a state in which the fan is to be operated. a second signal generator that generates a second signal generator, an output control means that changes a signal to be output based on a difference between a signal from the output means and a signal from the second signal generator, and a signal from the output control means. An optical transmission device consisting of a fan whose operation is controlled and which sends air to the heat dissipation section of an electrothermal conversion element.