Study And Implementation Of One Kind Of Control System For Tunable Laser

Laser control system is a type of instrument used to drive lasers work properly.The current laser control system on the market only provides one or two source outputs to meet the work needs of most lasers.Modulated Grating Y-branch(MG-Y)laser is a kind of widely used tunable laser.It consists of SOA(semiconductor optical amplifier),gain,phase,MMI(multi-mode interference)and modulation gratings.The laser requires five channels of current source input to drive for working.Existing laser control systems can not directly meet the drive requirements of tunable lasers.This paper is devoted to solving the driving problems of one new type of five channels tunable laser.There are three difficulties in control of the MG-Y laser.The five parts of the laser need to be driven at the same time to make the laser work properly.After the laser works normally,frequency control and power control are needed to maintain the stability of the emitted light.The laser is a temperature-sensitive device.The heat generated during the operation of laser affects the characteristics of the emmited light.It is necessary to control the operating temperature of the laser to eliminate the influence.After reference the design of existing laser control systems,this paper proposes one kind of tunable laser control system based on embedded system for the control difficulties of tunable laser.The main work of the paper includes:(1)For the problem that tunable laser's five channels of current source input need to be synchronized,first FPGA is used as the control chip,then a source output module is designed based on logic units of the FPGA to provide five channels of current source those were synchronous on hardware level.At last output logic of the current source is controlled to realize synchronous of source inputs to tunable laser.(2)For the problem that tunable laser needs frequency control and power control,ARM and FPGA are used to build dual-control-chip architecture of the system.The system takes ARM as main control chip and designs data transmission,logic control and measurement modules on it.System takes FPGA as co-control chip and designs source output,measurement modules on it.Finnally it realizes the frequency control and power control to the tunable laser through task allocation and cooperative work of ARM,FPGA.(3)For the problem that the operating temperature of tunable laser needs to be controlled,the PID(proportional integral derivative)control algorithm is used to design compensator of temperature control module.System designs TEC(thermo-electric cooler)control module based on FPGA.At last it realizes the control to operating temperature of the tunable laser through cooperative work of temperature control module and TEC control module.The test shows that the tunable laser control system designed in this paper can drive tunable laser working normally.The frequency of emitted light can be stable at ±2.5GHz.It control the operating temperature of tunable laser stable at±0.03?.And the pressure resistance test is passed.So the system meets the expected requirements.The system has been mass-produced.