Study Of High Extinction Pulse Light For BOTDR System

Distributed optical fiber sensing technology based on brillouin optical time-domain Reflection has broad application prospect,for it can sense the temperature and strain at the same time.However,it still has some shortcomings such as low space resolution ratio and instability of the system.The stability of the pulsed light source is the primary factor that causes the instability of the BOTDR system.Therefore,this dissertation deeply researched the basic principle of the pulsed light source for BOTDR system,and designed a pulsed light source system with high-extinction ratio.The performance of pulsed light source system had been tested.The concrete contents were listed as follows:Firstly,this dissertation analyzed the basic principle of pulsed light modulation and designed index.Then,we determined the overall plan and component of pulsed light source system with high-extinction ratio.Secondly,this dissertation designed a Laser drive system controlled by STC12 microchip.And this system integrated with a constant current driver modulation and a temperature feedback adjustment modulation,which achieves stable continuous light.It solved the problem that continuous light's power and wavelength is easily fluctuating with the fluctuation of drive current and working temperature.Thirdly,this dissertation designed an auto-locked circuit of biased electrical voltage and step tracking algorithm,which make sure the electro-optic modulator always working at the fit voltage.It solved the problem that electro-optic modulator is easily drifted with the temperature changes and the decreasing of extinction ratio.Finally,a pulse light source modulation device is setted.And testing the performance of pulse light source by contrast experiment.When the bias voltage automatic locking modulation device is not used,the extinction ratio of pulsed light decreased by 19.3dB in 150 minutes.When the bias voltage automatic locking modulation works,the extinction ratio of pulsed light can be stable in 51 d B ~ 53 dB in 150 minutes.Form the above,the paper has developed pulsed light source with high extinction ratio and high stable.