The Design And Manufacture Of High-Stabilization Temperature Control Module

Communication technology leads the global development in every field. A piece of information took quite a long time and manpower to be transferred before. Now we can know what are happening in any corner of the world at home just by pressing the mouse lightly, which profits from the flourishing development of network and communication technology. Due to the optical communication technology developed in recent years, the rate, distance and reliability of communication transfer have entered a new step. With the development of optical fiber communication, optical amplifier shows more and more important effect. EDFA(Er Doped Fiber Amplifier), applicable to C wave band, and full wave band online RAMAN amplifier, made the capacity and distance of the information transferred in optical fiber develop farther. Although there are only about30 years since the semiconductor laser appeared the first time, the new material and technology about it developed very quickly .From the homojunction, the heterojunction to the quantum well and the strained multi-quantum well ,the semiconductor has played more and more important role in the information society as the core of the semiconductor optoelectronics. And with its superior characteristic ,it has penetrated into the area which the other lasers cannot set foot in .For the above facts ,it has drawn wide attention ,and at the same time ,a higher quality semiconductor laser is needed. Semiconductor laser diode, as a core device of optical fiber communication, has the character of high efficiency, small size, low weight, high reliability, direct modulation and high integrated ability with other semiconductor devices. However, semiconductor laser diode is a kind of device with high power density and sky-high quantum efficiency. Even weak drive current and temperature change will lead to its large change of output light power. It can not work continuously under room temperature even if with small output power. At the same time, semiconductor laser diode is very sensitive to the temperature. The fluctuation of surrounding temperature not only leads to the fluctuation of supply current, but also makes threshold current, quantum efficiency, output wavelength and output light intensity of the laser diode change greatly. No matter which field semiconductor laser diode is applied to, it is always expected to work long and steadily. Especially in the benthic optical fiber communication system, semiconductor laser diode is required to work more than 25 years. However, actually used semiconductor laser diode can not meet people′s demand. Except of factor of the laser diode itself, many other factors result in the deterioration and unsteadiness of the device, such as the fluctuation of surrounding temperature, improper drive current, frequent impulse and heat dissipation. Therefore, the stable and constant control of semiconductor laser diode is rather important.Based on the practices in engineering, in this paper some key technological problems are deeply discussed in designing the whole structures and hardware, modeling and designing controlling strategy for this system. First, considering the technological requirements of the system and based on the study and absorption of relative theories and technologies for the key problems, the whole structure of this system is designed which is satisfied for the requirements of high reliability ,uniform distribution, the model being controlled of this system is designed based on the over-all heat transfer theory. In the process of making PID control realized ,calculating precision is improved by designing software and, designing hardware improves measuring and controlling precision of the system. This strategy is of excellent accuracy and strong robustness. The adjusting results prove that the requirement of technology of the system is satisfied in essence. Next, considering the complexity of the heating process of the system, such as the characteristics time change and delay, the heating system has to be further studied based on adaptive control of its model. The feasibility of the method is verified by simulation. And the simulating results prove this method is of excellent prospect.In constant temperature control, the principles of negative feedback control is also applied. NTC(negative temperature coefficient thermistor) is used to sense the change of temperature. TEC(thermoelectric cooler) is used to control the temperature. The temperature sensor and TEC are integrated together into some commercial laser diode modules. Therefore, it is necessary that the parameter of constant temperature controller is designed to match with the temperature sensor and TEC in laser diode modules. The feed back signal from the temperature sensor and setting temperature signal make subtraction, the calculated error-signal is sent to PID controller, and then to TEC drive circuit to control the magnitude and direction of the current in TEC. TEC is a device driven by current. When the direction of the current in TEC is different, TEC may work as heating or cooling. According to different number of couples of TEC, TEC has different cooling power and maximum current. Therefore, the circuit of current limitation in constant temperature control can avoid that output current is higher than maximum current of TEC. In this paper, a simple mathematic model is proposed for constant temperature controller. Its reliability has been proved by the experiment. This constant temperature controller can be applied not only to the temperature control in semiconductor laser diode, but also to other small cases when temperature control is necessary.Due to the particularity of the module, many necessary demands are put forward for making PBC, technics desighning of the apparatus appearance. As while as we are synthetically considering each character of every sort of device, we give attention to the questions such as knobs setting of the apparatus face, planning position of devices reasonably. Considering of miniaturizing of module, most devices chosen are sticked on surface. On the side of electromagnetic compatibility, besides regarding the lines going angle and width in the process of making board, due to the request of the module precision, D15 interface line makes corresponding particular treatment. Aspect craftwork plentifully considers some actual questions such as heat dissipation, choosing aluminium plate as the apparatus's bottom. At the same time, installation holes are obligated for the assembling of module and heat dissipation slice. Question about combination of module power and displaying is discussing actively.In the designing process of stable and constant control system, we consulted advanced application technology in the aspect of constant current control, constant power control and constant temperature control. Using the prime design idea as reference, we put forward the concept of stable and constant control and at the same time discuss the servo system of LD as a one system. Finally we finished the debugging and assembling of sample constant temperature controller. Temperature control precision of this constant temperature controller is 0.1℃; its short term stability is 0.02℃;its long term stability is 0.05℃.This paper has positive significance to the wide application of semiconductor laser diode. The limitation in the application resulting from the principles and techniques of semiconductor laser diode may be improved, such as the drift of output wavelength caused by the increase of junction temperature. The parameter of this stable and constant control system has been proved by the experimental test. It is precise and reliable.