Study Of Brillouin Scattering Mechanism In Optical Fiber And Its Application

Relative to the incident light, the Brillouin scattering light has a certain Brillouin frequency shift, and the frequency shift has a linear relationship with the temperature and strain. These properties can be used in high speed signal (microwave signal) generation, exchange (controllable delay), access (fiber optical sesnsing) and so on, and these aspects are the important parts in all optical information technology. Therefore, the systematic study of Brillouin scattering mechanism and its application not only have academic value, but also have important social significance.In this paper we analyze the characteristics of Brillouin scattering, and research the application of Brillouin scattering in theoretical and experimental in distributed optical fiber sensing, photonic generation of tunable microwave signal and controllable optical delay.The optimized Brillouin laser with single frequency has been designed as the local oscillator light for coherent detection Brillouin optical time domain reflectometry (BOTDR). The phase noise has been analyzed in theoretical, and the phase fluctuations of Brillouin laser are strongly correlated to that of the pump laser but they are also much weaker. The single frequency Brillouin laser with2.8MHz3dB bandwidth is obtained, and the maximum output power is about14dBm. The BOTDR using Brillouin laser as local light is demonstrated, and the experiment of53km sensing fiber is also performed, the measurement error is less than0.5℃. The experimental results show that the method can effectively reduce the required bandwidth of the detector in BOTDR, and improve the measurement accuracy.A simple approach to generate two bands of tunable microwave signal is proposed and demonstrated by using the Briouin laser. The principle generation of tunable microwave signal is analyzed in theoretical. Two single mode fibers with optimized Brillouin frequency shift spacing have been chosen as scattering medium in two cascaded ring cavities. The two bands of tunable microwave signal from390-453MHz and10.863-11.076GHz can be obtained through adjusting the temperature of the fiber and pump wavelength. The frequency fluctuation is less than0.2MHz, which illustrates good stability on frequency. The frequency range of microwave signal can be further expanded by using higher temperature controller, the gain fibers with higher frequency shift interval and wider tuning range of pump wavelength.On analysis of Brillouin controllable optical delay, the Brillouin gain and delay with multi-longitudinal mode pump is analyzed in theoretical. Through the analysis of Brillouin gain, delay and signal broadening affected by the mode spacing, the optimized mode spacing is obtained, and the ratio between the mode spacing and intrinsic Brillouin spectral width must be less than0.3in order to ignore the fluctuation of Brillouin gain and delay. In experiment the multi-longitudinal mode pump with optimized mode spacing is obtained by using semiconductor optical amplifier. A tunable broadband Brillouin pump with tuning range from1515to1560nm is genetared by using an F-P filter in the ring laser, the spectrum of the pump is comprised of a large number of longitudinal modes separated by6MHz,3dB-bandwidth is about11.5GHz and its fluctuation is less than100MHz within the tuning range. An8Gbit/s data signal is delayed by up to83.Ops (bit error rate<10"9) at17dBm pump power. And independent delay control of multi-channel signals is also demonstrated by the laser, which is generated by using two FBG in the SOA ring laser. The spectrum of each pump is separated by7MHz and spanning a bandwidth of11.6GHz and11.2GHz, respectively. The multi-channel broadband Brillouin slow light is demonstrated by using8Gbit/s data signals. The signals in both channels are continuously delayed and the maximal delay time with error free operation are up to56.4ps and56.Ops at19dBm pump power.