| The improvement of living standards makes that people is not also higher to therequirement of network technology, but more and more diversified. People want tonetwork faster, rich web content and get a lot of information in a short period of timethrough the network. At this time, optical-electricity-optical network transmissionsystems continue to highlight the technical limitations. All-optical network is put onthe agenda and then greatly improving the network information transmission,processing, storage, and other properties. The most important is the optical buffer. Weknow that slow light technology is a prerequisite for optical buffer. Now, thetechnologies which can realize slow light with strong dispersion areElectromagnetically Induced Transparency, Coherent Population Oscillation,Stimulated Brillouin Scattering and Stimulated Raman Scattering. Technologiesmentioned above are based on K-K dispersion effect. If the refractive index of themedium changes dramatically with the frequency, the group velocity of light willchange accordingly. Therefore, the speed of light can be controlled to produce slowlight. This article mainly introduced the process that the thulium doped fiber to realizeslow light under the coherent population oscillation effect. And discussed thepossibility of improve the relative delay of the speed of light. The full text can bedivided into the following four parts.Chapter One: This chapter describes the development of the optical andmeasurement of the speed of light. It analyzes the significance of slow light toachieve all-optical network and develop optical buffer. Then, it also introduces thedifferent ways of realization of slow light. Discussed the merits of the ways whichbased on electromagnetically induced transparency (EIT) effect, coherent populationoscillation (CPO) effect, stimulated Brillouin Scattering effect (SBS), stimulatedRaman Scattering effect (SRS) and so to slow the speed of light. After comparing, thecoherent population oscillation (CPA) technology to realize slow light is lowerexperimental requirements, more controllable range of light and applicability better. Chapter Two: This chapter firstly illustrates the four kinds of definition of thespeed of light and compares the phase velocity and group velocity. Then, this chapterfocuses on explaining the definition of K-k dispersion and its importance to realizeslow light. K-K dispersion relation reflects that different frequencies of light havedifferent refractive indices in the same medium. We can use the important conclusionK-K relations exhibited to realize the speed control and realize the slow light. And theconclusion is that the group velocity of light will vary, if the refractive index changesdramatically with frequency of light.Chapter Three: This chapter mainly introduces the mechanism in the use ofcoherent population oscillation (CPO) effect to achieve slow light. Then article givesthe appearance process of spectral hole burning and its importance of slowing downthe speed of light. The article also writes the density matrix equations of two-levelsystem and deduces the interaction of systems and the light field by the densitymatrix equation.Chapter Four: This chapter establishes a theoretical model of slow light inthulium-doped fiber.Chapter Five:This chapter has been simulated, made relationship of fractionaldelay and modulation frequency under large signal and small signal situations,discuss ways to improve the interaction distance time delay changes. |
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