Study On The Tuning Of Semiconductor Laser Used In Optical Fiber Sensing System

The semiconductor laser has the characteristics of small volume,narrow linewidth,low power consumption and high side mode rejection ratio.It is an important component of the optical fiber sensing system.The stability of its output wavelength and power determines the measurement accuracy of the whole optical fiber sensing system.In the optical fiber sensing system,the characteristic wavelengths of optical elements often deviate from the original design values,which makes the output wavelengths of semiconductor lasers deviate from the characteristic wavelengths of these elements,thus affecting the measurement accuracy and stability of the whole sensing system.This deviation value is usually not very large,so the laser does not need to have a large adjustment range.Generally,it requires about 3nm,but it requires high tuning accuracy,which needs to reach 0.01 nm.The system design of the sensor can be optimized by using the tunable semiconductor laser,which makes the sensor system more flexible.The wavelength tuning of semiconductor laser is studied by driving current control and temperature control.As the change of driving current will lead to the change of temperature,the previous tuning process is complex,time-consuming and difficult to adjust to the best state.In this paper,a 2x2 matrix describing the relationship between wavelength ? and power P as output and driving current I and temperature T as input is proposed,and the values of four matrix elements in the matrix are measured.By using this relation matrix,the optimal tuning value of driving current and temperature can be calculated directly according to the requirements of different wavelength and power,which makes the tuning process more efficient and accurate.In the hardware part,the driver,temperature control,back light acquisition circuit and laser bottom board module of the semiconductor laser are designed,and the hardware circuit is communicated with the micro host through USB5622 data acquisition card to realize the signal acquisition and control.In the software part,the control and acquisition of driving current and temperature,laser self-protection control,front panel response and interactive interface display are realized by Labview program.The software and hardware are combined to complete the whole instrument assembly and system integration.The laser tuning range is 3.2nm,the precision is 0.01 nm,the drift is less than 0.002 nm,and the power fluctuation is less than 3?W.