多通道干涉大范围可调谐激光器控制系统(特邀)

Control System of Multi-channel Interference Widely Tunable Laser(Invited)

多通道干涉大范围可调谐半导体激光器是波分复用系统中的新型关键器件,设计了一套针对此激光器高精度电流注入、温度控制、波长锁定等问题的控制系统。将该激光器的整套控制方案集成单板。在该控制系统下,测试得到激光器输出波长在1524~1572 nm中每间隔0.4 nm的120个ITU标准波长光谱图,调谐范围超过48 nm,并且在整个调谐范围内,边模抑制比超过了45 dB,波长偏差与ITU标准波长相差小于±10 pm,线宽小于100 kHz。

Monolithic integrated widely tunable semiconductor laser is one of the key devices of photonic integrated circuit and next-generation reconfigurable optical network.In 2016,Wuhan National Laboratory for Optoelectronics of Huazhong University of science and technology proposed and experimentally verified a new type of widely tunable laser multi-channel interference widely tunable laser(hereinafter referred to as MCI-WTL),which has the advantages of low cost,large fabrication tolerance and excellent performance.In this paper,a set of control system is designed to solve the problems of high-precision current injection,temperature control,wavelength locking and so on.A complete scheme of MCI-WTL control is integrated into a single PCB board to realize the miniaturization and integration of control,which is of great significance to promote the commercial application of this laser.Firstly,the control system is introduced,including the control principle and control requirements of MCI-WTL,the physical diagram of software and hardware of the system,innovation and research significance.Then the principle of the control system is analyzed in detail.The hardware part includes the main control chip STM32F429;2 ADN8810 output two channels of 0~300 mA controllable current to work in the active section and SOA section to realize laser generation and optical power amplification;8 AD9744outputs 8 channels of 0~20 mA high-speed controllable current,which works in the common phase area and 7 arm phase areas to realize wavelength tuning.Digital Proportional Integration Differentiation(P-ID)algorithm is used for temperature control.In the wavelength locking part,a unique reflection peak locking technology is proposed to compensate the wavelength deviation.In the software part,LabView is used to make the upper computer interface,and the interaction between the host and the control module is carried out through the upper computer software,which can switch the wavelength and adjust the power in real time.Then the principle of temperature control and wavelength locking system are introduced respectively.The principle of temperature control can be divided into four parts:temperature detection,error amplification,P-I-D calculation and output current.The principle of wavelength locking is divided into two parts:longitudinal mode locking and reflection peak locking.The current wavelength drift is calculated by the frequency domain characteristics of F-P etalon,and then the current in the common phase area of the laser is adjusted to achieve the wavelength pullback.After adjusting the current in the 7 arm phase area,the laser peak is locked.Reflection peak locking is a unique technology of MCI-WTL in wavelength locking.The test results of the whole system are shown at last.Firstly,the construction of the whole test-bed and instrument connection are shown,and the performance indexes of MCI-WTL when injecting 100 mA current in the active area and 300 mA current in the SOA area are tested.The spectrum superposition diagram of 120 standard ITU channels from 1524 nm to 1572 nm with an interval of 0.4 nm at double temperatures of 25℃and 45℃is obtained to realize the tuning range of more than 48 nm covering the whole communication C-band,the Side Mode Suppression Ratio(SMSR)is greater than 45 dB,and the wavelength deviation from ITU-T standard wavelength is less than±10 pm.The maximum output power in the whole tuning range can reach 51 MW.In the test of the wavelength locking system,when the wavelength locking system is not turned on,the laser output wavelength can change positively with temperature,and the wavelength drift is about 0.1 nm/℃.When the wavelength locking system is turned on and the chip temperature is changed,the laser output wavelength is stable at the calibration wavelength and almost no drift occurs.In the line width test system,the coherent receiving system based on the delayed self homodyne method is used to measure the linewidth of MCI-WTL.The block diagram of the linewidth test system is shown.The linewidth of all wavelengths is less than 100 kHz in the whole tuning range.In the high and low temperature test of the module,the changes of wavelength,power and SMSR of 9 wavelengths at-5℃,25℃,50℃and 60℃were recorded.