用于量子密钥分发的半导体激光器温控系统

摘要

The QKD system has a rigorous demand on the stability of the optical source,especially the stability of the wavelength and the intensity of the laser,which directly affect the system's bit rate. To meet this requirement and con-sider the temperature characteristics of DFB Laser,an effective temperature control system was designed. The system uses FPGA as the controller,along with the incremental PID algorithm to monitor the working temperature of DFB la-ser in real time and uses thermoelectric refrigeration control chip MAX8520 as the TEC driver. The NTC thermistor, which is integrated into the DFB laser,constitutes a temperature acquisition module and a closed－loop negative feed-back structure. The experimental results show that the temperature control accuracy is above ±0. 03 ℃,and the wave-length drift can be controlled within 0. 01 nm. The temperature control system has the characteristics of small size, high efficiency and high reliability. It can provide a stable temperature control for the laser to ensure the stability of the optical source wavelength of the QKD system.%由于量子密钥分发(quantum key distribution,QKD)系统对光源的稳定性要求极高,尤其是激光器发出光的波长和光强的稳定性,直接影响了系统的成码率.由此,针对分布反馈式(distributed feedback,DFB)激光器的温度特性,设计一种有效的温度控制系统.系统以 FPGA为控制核心,采用增量式PID算法,对DFB激光器的工作温度进行实时监控.采用热电制冷控制芯片MAX8520 作为半导体制冷器(thermoelectric cooler,TEC)的驱动芯片.利用集成于DFB激光器内部的负温度系数(negative temperature coefficient,NTC)热敏电阻构成温度采集模块,组成闭环负反馈结构.通过实验测试,温度控制精度可达±0. 03 ℃,波长漂移可控制在0. 01 nm以内.该温控系统具有电路体积小、效率高和可靠性高等特点,可为激光器提供稳定的温度控制,以保证QKD系统的光源波长的稳定性.