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Investigation And Design Of Optical Filter Based On Fiber Bragg Grating

Posted on:2009-09-06Degree:MasterType:Thesis
Country:ChinaCandidate:B XieFull Text:PDF
GTID:2178360245489381Subject:Communication and Information System
Abstract/Summary:PDF Full Text Request
Optical filter is an indispensable component in optical fiber communication and optical sensor systems. It has been widely adopted in wavelength locking, wavelength multiplexer/demultiplexer, wavelength routers, wavelength conver -sion, dispersion compensators, and gain equalizers etc. With the increasing number of channels and decreasing channel spacing in wavelength division multiplexing (WDM) system, novel optical filters with excellent characteristics have become a leading trend presently. Particularly, filters based on fiber Bragg gratings (FBG) have attracted considerable attentions in the WDM system, because of their excellent characteristics, such as low insertion loss, insensitive with polarization, easy concatenating with general optical fiber and dynamic tunable of spectrum response etc.Firstly, the development, research status and relative applications of FBG have been simply introduced. Then the reflectivity of uniform FBG has been calculated with Coupled-Mode Theory. And a simple but effective numerical method known as Transfer Matrix Method is also presented. Further, principle of filtering devices using FBGs and Mach-Zehnder Interferometer (MZI) has been introduced by taking Optical Add/Drop Multiplexer (OADM) based on MZI using FBGs for example. Meanwhile based on the interference principle of MZI and transfer principle of FBG, the theoretical output expression of optical filter using cascaded MZIs with sampled FBG was investigated. At the last part of the thesis, a novel theoretical model of improvement on peak-to-trough ratio of sample fiber Bragg gratings with multiple phase shifts (MPS-SFBG) is established for the first time. The sidelobes of filter are suppressed because of the phase matching condition between the two MPS-SFBGs with inverse arrangement of introduced phase shift. Further, we also analyze the improvement on peak-to-rough ratio for different multiplication factors.The simulations of filter based on MZI and sinc-SFBGs indicate that the design can obtain equal 3-dB bandwidth and gain spectrum simultaneously, while design with traditional rectangular sampled FBG can not. Furthermore, continuous tuning can be realized over the entire Free Spectral Range (FSR) by injecting current to the electrodes. The analyses of cascaded MPS-SFBG show that the filter can effectively improve the output spectrum. Compared with the decrease of peak value, the improvement of peak-to-trough ratio is far more considerable in our design.
Keywords/Search Tags:Optical fiber communication, Optical filter, Fiber Bragg grating (FBG), Mach-Zehnder interferometer (MZI), Multiple phase shift (MPS)
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