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Study On Multiwavelength Erbium-Doped Fiber Laser

Posted on:2009-02-25Degree:MasterType:Thesis
Country:ChinaCandidate:Z Y LiuFull Text:PDF
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With the advent of information era, human society's increasing demand for communication capacity causes the introduction of Wavelength-Division Multiplexing(WDM). In present, WDM communication system is developing towards two directions. On the one hand, WDM system is transforming from the point to point system to all optical networks. Optical Add/Drop Multiplexer (OADM), which has a capacity of add/drop signals in the optical formation and then avoids the drawback of electronic bottleneck demonstrated in traditional technology, becomes the pivot to realize all optical WDM networks. On the other hand, the number of signal channels keeps increasing with the development of WDM communication system. Due to their economic cost, it is an indispensable way to utilize multiwavelength lasers as signal emitters in communication system. Multiwavelength Erbium-doped fiber lasers (MW-EDFLs) become the research focus for their attracting merits.The work is supported by the National Key Basic Research and Development Programme of China under Grant No. 2003CB314906"Innovative and basic investigation of optoelectronic device based on Photonic crystal fibers"and the Tianjin Natural Science Foundation under Grant No. 06YFJZJC00300"Investigation of novel multifunction-integrated Photonic Crystal Fiber Raman amplifier".This dissertation emphasizes on the study of multiwavelength erbium-doped fiber lasers, and the major innovative work includes the detail descriptions on the following subjects:1. The fundamental principles of both the linear cavity fiber lasers and the ring cavity fiber lasers and the stability criterion for multiwavelength oscillations are introduced. Several kinds of techniques to achieve mulitwavelength oscillating are summarized.2. The spectra characteristic of the polarization-maintaining fiber grating is analyzed with coupled-mode theory. We proposed the switchable dual- and triple-wavelength erbium-doped fiber laser with a narrow wavelength spacing of <0.1 nm via using a single fiber Bragg gratings written in polarization-maintaining (PM) fiber. By adjusting polarization controller, the wavelength spacing of dual-wavelength lasing oscillations can be tuned to as small as 0.032 nm. The maximum amplitude variation for every lasing wavelength is less than 0.5 dB. The room-temperature operation principle is based on the polarization hole burning and spectral hole burning in an ordinary erbium-doped fiber ring laser (EDFRL).3. The principles of sampled fiber grating and nonlinear optical loop mirror are analyzed. We propose and demonstrate a stable room-temperature channel-spacing and wavelength tunable multiwavelength erbium-doped fiber (EDF) laser using a sampled Hi-Bi fiber grating and a photonic crystal fiber (PCF) loop mirror. By adjusting the polarization controller, we can achieve 0.4 nm and 0.8 nm channel-spacing of the multiwavelength EDF laser. The measured power fluctuation of each wavelength is less than 0.2 dB.4. We propose and demonstrate a tunable multiwavelength erbium-doped fiber laser based on a polarization-maintaining photonic crystal fiber (PM-PCF) Sagnac loop filter. Stable, room-temperature operation is obtained by employing a nonlinear optical loop mirror. At a central wavelength of 1563.000 nm, we generate 60 wavelengths oscillation within 3-dB bandwidth. The measured power fluctuation for each lasing wavelength is less than 0.2 dB in half an hour. Furthermore, by adjusting the polarization controllers in the sagnac filter, wavelength locations of the laser lines with a fixed channel spacing of ~ 0.078nm can be continuously shifted.5. A simple technique for generating multi-transmission-band fiber Bragg grating filter is proposed and demonstrated. Via attaching half of a uniform fiber Bragg grating to the central portion of a triangle cantilever beam, a multi-transmission-band fiber filter can be achieved by applying displacement on the free end of the beam. Dual- and triple-wavelength erbium-doped fiber laser with the wavelength spacing as small as 0.094 nm at room temperature are experimentally achieved by employing the filter and a nonlinear optical loop mirror. The measured power fluctuation for each lasing wavelength is less than 0.2 dB in half an hour.
Keywords/Search Tags:Erbium-doped fiber laser, Fiber Bragg Grating (FBG), multiwavelength, photonic crystal fibers, fiber loop mirror, polarization controller, polarization hole burning
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