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Wavelength Tunable Erbium-doped Fiber Ring Laser

Posted on:2006-01-15Degree:MasterType:Thesis
Country:ChinaCandidate:J S ZhangFull Text:PDF
GTID:2168360155953445Subject:Communication and Information System
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In order to satisfy the request of superhigh -speed, superhigh -capacity optical communication system, lots of optical communication models appear. Among them, the WDM (Wavelength Division Multiplexing) technique becomes a hot subject and a research frontier because of its reconfigurability, transparency, compatibility and survivability. Many new types of active fiber components and passive fiber components are being researched and developed to meet the demand of WDM communication systems. Among the active fiber components, the fiber lasers, especially the wavelength tunable fiber laser, attract researchers'attention because of its simple integrability with the basic fiber systems and good temperature stability. Fiber lasers are emerging as an interesting alternative to semiconductor laser diodes for use in future WDM communication system. Tunable laser is the key devices in WDM fiber communication system, and is used in the fields of optical sensing system and high resolution spectroscope as well. Tunable erbium-doped fiber laser (EDFL) using an dielectric thin-film interference filter (DTF) is studied, which was controlled programmablly and has many merits such as excellent reliability of temperature wide tunable range, narrow linewidth, quick tuning speed, easy and reliable tuning and right matching fiber. The erbium-doped fiber of high concentration is introduced, which can not only simplify the lasers'structure while shortening their size, but can increase the stability and practicability for their compactness and flexibility. The procedure is done by optimizing some of the fiber laser parameters, such as the coupler's reflectivity R and the length of erbium-doped fiber L for a given concentration of erbium-doped fiber in order to achieve maximum output power for given pump power. Therefore, this fiber laser, as a new laser or information source, has their sharp competitiveness and promising future. Organization of Thesis: Chapter 1: The general survey of optic fiber lasers is given in. With the wide application in optical communication, optical data storage, sensor technology, medicine and so on, the optic fiber lasers develop very fast. The historical overview and the classification of the fiber laser is summarized, as well as, the basic structure and principle of fiber laser are analyzed and their recent research and development are also discussed in this chapter. The hot points that include high power fiber laser, narrow linewidth tunable fiber laser and ultra short pulse fiber laser are presented. And the future trend of fiber lasers is described. Chapter 2: The design and principle of Wavelength Tunable Erbium-doped Fiber Ring Laser is presented. Firstly, We give the general background knowledge of erbium-doped fiber lasers such as the basic principle of laser, the character of pump and threshold. Secondly, the theoretical study that relates to the characteristic of the energy level of Er3+ and the fluorescence spectrum for erbium-doped fiber is investigated. From the rate equations, we shall establish a few of the analytical and explicit expressions for an erbium-doped fiber ring laser, which include input power, output power, laser threshold, slope efficiency and length of the erbium -doped fiber. The design of laser cavity is a key step in building a fiber laser with good performance. Various configurations based on two types of cavities, linear FP cavity and ring cavity. Because ring cavity has excellent lasing efficiency and is able to eliminate back scattering and spatial hole-burning effects, fiber ring lasers have better potential to achieve single-longitudinal mode oscillations. Thirdly, the optimization procedure of the fiber laser parameters, such as the coupler's reflectivity R and the length of erbium-doped fiber L for a given concentration of erbium-doped fiber, is done by means of: combination of simulation and experiment, in order to achieve maximum output power for given pump power. Chapter 3: The tunable mechanism of erbium -doped fiber laser is studied. Firstly, the transmission principle of F-P filter is presented, and the experimental investigation of tunable erbium-doped fiber ring laser based on F-P filter has been developed. Secondly, the transmission principle of dielectric thin film interfere filter and the experimental investigation of tunable erbium-doped fiber ring laser based on this filter has been developed, at the same time, the programmable control of this thin film interfere filter is achieved.Lastly, the analytical comparison of above two tunable methods is developed. Chapter 4: The deep and systematical researches on Erbium -doped Fiber Superfluorescent Sources and Erbium-doped Fiber Amplifier have been developed. Firstly, the basic principle of superfluorescence and the structures of superfluorescent fiber source were introduced. Theoretical analysis of superfluorescent fiber source was developed such as the relationship of gain distribution, power distribution and bandwidth variation v.s pump power. A experimental configuration of SFS in single-pass backward (SPB) was established to study the characteristics of superfluorescent fiber source. Because of homogeneous broadened transition the bandwidth of this superfluorescent fiber source decreased as the pump power increased. Secondly, The basic principle of erbium-doped fiber amplifier was introduced, and the structures of superfluorescent fiber source were introduced and a experimental configuration of EDFA in single-pass forward (SPF) was established to study the characteristics of erbium-doped fiber amplifier gain spectrum. Small signal gain of 33 dB was achieved. A high quality amplifier with high gain, low noise figure and wide bandwidth gain spectrum has been reported. Chapter5: The configuration and experimental research of the wavelength tunable erbium-doped fiber ring laser is presented. Firstly, put forward the practical design scheme of the wavelength tunable erbium-doped fiber ring laser on the basis of analyzing and contrasting various current popular schemes; On the basis of theoretical design scheme, the apparatus and components for the experiment were actively prepared and configured; The configuration of the Tunable Erbium-doped Fiber Ring Laser was formed by a spool containing 2.33m of erbium-doped fiber as gain medium, 980nm pump laser induced from fiber pigtail of the 980 nm semiconductor laser was launched into the resonant-cavity via a 980/1550 nm WDM, then, a population inversion was formed in erbium-doped fiber, the lasing wavelength was selected by means of tunable band-pass filter. Traveling wave operation of the ring laser was accomplished by a polarization independent optical isolator. coupler output splitting ratio is 0.8, Secondly, optimization of output power characteristics of wavelength tunable erbium -doped fiber ring lasers is done by optimizing some of the fiber laser parameters,...
Keywords/Search Tags:Wavelength Division Multiplexing, Dielectric thin-film (DTF) interference filter, Fiber ring laser, Wavelength tunable, Erbium-doped fiber
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