Research On Wavelength Tuning Characteristics Of MGY Laser Devices For Optical Fiber Sensing

The wavelength tunable semiconductor laser is an ideal light source in optical communication and fiber grating sensing interrogation systems,and it is also a hot spot in the field of interrogation light source research today.Among them,the modulated grating Y-branch(MGY)laser is the state-of-the-art,which has good static and dynamic performance,high side mode suppression ratio(SMSR),wide tunable range,high tuning speed.Besides,it has the characteristics of no additional optical frequency selective structure,and has been widely used in the field of optical communication.It also shows great technical advantages in the field of fiber grating sensor interrogation,and has good application prospects in the fields of military science and technology,aerospace science and industry,industrial production monitoring and road and bridge quality monitoring.However,to use the MGY laser for communication as the light source of the fiber grating interrogator,it has to overcome the difficulties of few standard wavelength points and large spacing of the communication light source,it is necessary to quickly establish a high-resolution wavelength look-up table to provide a high-resolution tuned light source for interrogation.The current research does not solve the problem of fast wavelength calibration of MGY lasers.In this paper,we proposed a comprehensive mathematical model based on transmission line laser model(TLLM)and transfer matrix method(TMM)for MGY lasers to study its tuning characteristics.Based on this,we designed and developed an automatic wavelength tuning system based on MGY lasers,which solved the problem of high-resolution and rapid calibration of MGY lasers.The main research contents of this paper are as follows:(1)As for the comprehensive model,the gain region and the phase region of the MGY laser are simulated by TLLM in the time domain,and the left and right modulation grating regions are simulated by TMM in the frequency domain,which then converted to time domain model by inverse fast Fourier transform and digital filtering methods.Based on this model and combined with the carrier density rate equation,the simulation analysis is carried out to simulate the wavelength tuning characteristics of the MGY laser and analyze its output power-current characteristics.(2)According to the wavelength tuning characteristics of MGY lasers,we designed and developed an automatic wavelength tuning system for MGY lasers,including the hardware part—laser driving module and the software part—laser control module.Besides,We propose a wavelength tuning algorithm based on cubic polynomial fitting method and a variable-step phase current tuning method..(3)we carried out the wavelength tuning experiment of the MGY laser with the wavelength tunable range of 40 nm on the designed laser wavelength tuning system based on the wavelength tuning algorithm of the cubic polynomial fitting method and the phase current tuning method with variable step size.The experimental results show that the single wavelength calibration time is 27 s,which is more than double the speed of the existing stepping current scanning tuning method.And the laser "wavelengthcurrent" tuning table is generated at a high speed,which provides a high-resolution tuning light source for interrogation.