Laser Driver Products II

In last article, some types of laser drivers have been introduced, low noise laser driver and constant current laser driver. This paper aims to the other two types laser drivers, high voltage constant current laser driver and AC input laser driver.

III. High voltage constant current laser driver

High voltage constant current laser drivers include two series, ATLSXA212 and ATLSXA214. Both of them have high input voltage than other laser drivers in ATI. ATLSXA212 has an input voltage between 4.75 to 16V while the other one 5V to 16V. High efficiency, high output power, compact size, low noise, high stability are the main features of these high power laser drivers. Therefore, they are often costly.

IV. AC input laser driver

Most of ATI laser drivers are DC input. There are also some AC input laser drivers, which have relatively larger size. The output current range is 20A ~ 45A. These laser drivers come with a low noise 2.5V reference voltage. It has high efficiency and low temperature rise, with low power consumption.

The physical photo of a constant current laser driver

For different types of laser drivers, we also provide corresponding evaluation boards, which simplifies

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Laser Driver Products I

Diode laser drivers are designed to drive diode lasers in a stable and efficient way. Based on different functions, laser drivers are divided into multiple types, among which DC input laser drivers include low noise diode laser drivers, high efficiency constant current laser drivers, high voltage constant current laser driver, constant current laser drivers; and AC input laser drivers.

I. Low noise laser driver

ATLSXXX103 and 104 are typical low noise laser drivers, which come with ultra low noise, compact size and over current protection function. The maximum output current of laser drivers can be from 100mA to 1A, with high stability. These laser drivers are of 100% lead-free and RoHS compliant.

II. Constant current laser driver

Constant current laser drivers include ATLSXA201 and 202 series. These laser drivers are designed to drive diode lasers with constant output current at high efficiency. The output current can be 1A to 6A for 201 and 500mA to 4A for 202. The laser drivers are packaged in a 6-side metal enclosure, thus emitting zero EMI.

The physical photo of a constant current laser driver

To be continued…
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Development of a laser driver for driving diode lasers

With the development of science and technology, semiconductor laser technology has penetrate every field of national economy and defense construction. It has been applied in remote communication, laser radar, digital signal storage and recovery, laser ranging, robot, holographic application, medical diagnosis, etc. However, It’s very demanding for semiconductor laser on its working conditions. If It’s under improper work or storage condition, it will result in a sharp deterioration in performance and even failure. Therefore, an electronic power supply for driving diode lasers, i.e. laser driver is playing a more and more important role in making the laser work normally.

In recent years, the laser has been used in wider and wider applications, so the development of the driving power supply with high quality is imperative. Besides regular functions, the new power supply should have more stable output current and more reliable and effective protection for the laser.

The physical photo of a laser driver for driving diode lasers

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The main performance parameters of laser driver

A laser driver is between multiplexer and laser, which completes electro-optical conversion function. In order to make the laser work well, the good driving signal needs to be provided, depending on the performance parameters of laser driver.

The physical photo of laser driver

The performance parameters of laser driver mainly include:
(1)Working speed: the working speed of laser driver can be reflected by system bandwidth and the upper limit of working speed can increase with the bandwidth increase.
(2)Output voltage swing: the output modulation voltage has enough swing.
(3)Shake: small shake can reduce bit error rate and improve the performances of driving circuit.
(4)Power consumption: driving circuit usually has larger power consumption than other transmission modules have. The heat generated by chip can be reduced by declining the chip power consumption, so the requirements of chip package can also be reduced. Therefore, chip can work more stably and reliably.
(5)Input and output impedance: the impedance 50Ω is usually selected.
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Driving modes of laser driver

The main function of laser driver is to enlarge high speed signal outputted by a multiplexer to drive the laser diode to work effectively.

Figure 1.The modulation modes of laser driver

Subsequent circuit of laser driver is light emitting device and there are two driving modes to drive it, as shown in the figure 1. One is directly working on laser diode. The main principle is to change the input current of laser diode and then the required optical digital signal is generated, which is called direct modulation. The generation and modulation of light wave are both completed in this method. It is easy to implement this driving mode and this node has simple equipment, low cost and wide bandwidth, etc.

The other diving mode is indirect modulation. Generally speaking, by using electro-optic crystal modulator, modulation in the external light source can be realized and the continuous wave of laser driver is modulated by transmission digital signal in the electro-optic crystal modulator. The advantage of external modulation is that it can reduce Chirp effect that is the maximum factor to block bit rate increase, so as to obtain higher bit rate and further transmission distance.

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Function of laser driver

In optical fiber communication, optical module plays a very important role. Laser driver used on the front end of optical emission can realize the laser bias and modulation. High speed voltage signal is converted into high speed current signal to modulate laser.

Actually, a laser driver is a kind of high speed switching current and its circuits mainly include:(1) high speed modulation circuit; (2) high speed bias current driving circuit; (3) automatic power control circuit.

Our company specializes in researching and producing laser drivers. In order to meet customers’ different design demands, we have designed multiple types of laser drivers, such as high voltage constant current laser driver, low noise constant current laser driver, dual mode laser driver, AC input high current high efficiency, and so on. These laser drivers don’t need heat sink because of their high efficiency.

The physical photo of laser driver

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The simple classification of thermoelectric coolers

Thermoelectric cooler (TEC) is built on the thermoelectric system, which can both cool and heat, depending on DC current direction. As TEC has no refrigerant, no pollution, no rotation parts, no noise, long service lifetime and some other advantages, it has been widely used in electronic fields, laser fields and so on.

The physical photos of TEC

According to temperature, TECs can be divided into two types, regular temperature rectangular TEC and high temperature rectangular TEC. The temperature range of the former is −60°C~85°C and the latter is −60°C~200°C.

According to package form, there are sealed version and non-sealed version. The service lifetime of sealed TEC is longer than that of non-sealed TEC, but the former has lower efficiency. If TEC works in a moisture environment, the sealed TEC should be selected to achieve long service lifetime and high reliability.

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Development prospect of thermoelectric cooler

With the development of science and technology, there are more and more researches about thermoelectric cooler (TEC) and the achievements on the improvement of the material optimal value and the optimization of thermoelectric cooler has been obtained. Now TEC has been widely used in many fields, and along with the time and research development, TEC will play more and more important role in the electronic  and  some other fields.

（1）Theoretical study of TEC technology is mature. Low optimal value coefficient indicates that it has great development space in theory. With the further research and development of new materials, the optimal value will continuously improve and TEC will have broad prospects.

（2）More experiments in production technology and process should be done. The organic combination of computer aided design has a great help for reducing the test cost, accelerating the improvement of theory and improving the performance of the semiconductor.

（3）In application, different research methods are used in different fields. As the operation process of TEC is influenced by many factors, it is best to use the methods of system analysis and comprehensive analysis.

It can be seen from above that TEC will have good development prospect in the future.
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The current main problems of thermoelectric coolers

Thermoelectric cooler (TEC) is built based on Peltier effect. It is a kind of solid components, which has no pollution, high reliability, small size, rapid cooling, rapid heating and some other characteristics. It has been widely used in electronic, medicine, industry, agriculture and some other fields. However, TEC still has some problems.
1.In order to reach the equivalent cooling efficiency of mechanical compression refrigeration, the material optimal coefficient of TEC is not high, which is the main factor that hinders the development of TEC.

2.There is little research about optimization design of cooling system on cold and hot sides, so it makes the design of TEC in the theoretical calculation stage and the actual operation effect cannot be well guaranteed.

3.With the rapid development of science and technology, the sizes of devices are becoming more and more complex and there are more and more factors needing to be considered. How to solve optimization problems of multi-stage TEC, dissipation problems of small size devices and thermoelectric energy conversion problems are the content of the future research.

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Dissipation methods on TEC hot-side

During the cooling process of thermoelectric cooler (TEC), the dissipating effect has direct effect on the cooling performance. The bad performance of heat transfer will cause the temperature rise on hot-side, thus the cooling capacity will reduce a lot.

Under certain current, heat transfer from hot side to cold side can be reduced with the decrease of temperature. Only when the heat on the hot-side is drained away in time to maintain different hot-side temperature, the cold side can continuously cool.

At present, there are many researches on dissipation methods on TEC hot-side. The main dissipation methods include air natural convection, air forced convection cooling, water cooling, heat pipe heat transfer, etc.

1.Air natural convention
Using air national convention, the heat can be dissipated into environment. Because of small power, this method can be used in some small occasions or some occasions with noise restrictions.

2.Air forced convection cooling
Based on natural convection cooling, an axial flow fan is fixed on the end of heat sink.

3.Water cooling
A cold water tank is connected to the hot end of TEC. The water through the cooling water pipe can take the hot-side heat away. This is a very high efficiency cooling method.

4.Heat pipe heat transfer
When comparing with troditional method, in working process, the temperatures on the both sides have little difference on both ends. A long isotherm ribbon comes in to being along with the axis of the heat pipe.

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