The Research Of Delay System Of Slow Light In Fiber Based On SBS

It is a significant technique to control the speed of light in an optical fiber for the all optical communication. In the present communication network system, optic-electric or electric-optic convertions are usually needed , which make the optical communication system can not bring its advantages into full play. In order to raise the speed of the system, men have been dreaming of the coming of all-optical communication for a long time. To slow down the speed of light is the key to realize all-optical communication, which is called slow light. Now, there are many means to realize slow light, such as eleetro-magnetieally induced transparency(EIT),coherent population oseillation(CPO),Stimulated Roman scattering(SRS),Stimulated Brillouin scattering(SBS).Stimulated Brillouin scattering(SBS)is the common nonlinear effect in fiber, and has more advantage than other technique in the area of slow light, such as low Brillouin threshold power, easily controllable group velocity, tunable wavelength and it is easy to be integrated with existing telecommunications. So slow light based on SBS has already becomes a hot topic in the research of slow light.With the support of the Tianjin Natural Science Foundation (Grant No. 08JCYBJC14400), and the Ministry of Science and Technology of China 973 Project Program (Grant No. 2010CB327605), we finish the work. The main contents of the paper are as below:1. We systemically introduced the advancements on controllable slow light based on SBS, elaborates the theory of the usual used slow light technique, such as eleetro-magnetieally induced transparency(EIT),coherent population oseillation(CPO),Stimulated Roman scattering(SRS),Stimulated Brillouin scattering(SBS), and compare and analyse the advantages and disadvantages of these techniques.2. The technique of controllable slow light based on SBS is systemically introduced, and presented the physical principle of SBS in optical fibers and theoretically studied the SBS slow and fast light in optical fibers. The reason of the pulse distortion as the pulse is transmitted in the slow light system is analysed. And particular analyse a typical slow light system based on SBS.3. The configuration of optically controlled delay line is studied carefully, and on this basis presented a novel configuration of optically controlled delay line. This configuration can remarkably enhance delay time, has simple structure, and has notable high pump efficiency. Experimental results show that the pulse signal of 50 ns is obtained 90.552 ns delay through the two fiber segments, and the efficiency of the pump power is up to 96%.4. To solve the limitation of narrow bandwidth of SBS gain spectrum on high speed signal and pulse distortion, a novel method to broaden the gain spectrum of SBS based on direct modulation is presented. Simulation demonstrates that we obtain 11.2GHz bandwidth of the power spectrum of laser using this approach, and it is much larger than that using single PRBS at same injection current. In the simulation, for 10GBit/s PRBS, 11GHz of SBS gain spectrum is achieved. Under the 16dB of Brillouin gain, 100ps long pulse was delayed by up to 54ps. The pulse broaden ratio is 45% and the fractional delay is up to 0.54.