| Fiber Bragg Gratings (FBGs) as a kind of photonic devices rapidly developed in recent years, have a wide application in optical sensing, dispersion compensation, and now various special structures of FBGs have got more and more attention. The composite magneto-optical FBG (CMFBG) as a special grating structure combines the traditional grating and the magneto-optical effect and its spectral characteristics can be adjusted by the the magneto-optical effect, with potential applications in optical communication and magnetic field se nsing. In this paper, the optical spectral and time delay characteristics of the CMFBG are analyzed, and some applications in optical sensing and dispersion compensation are discussed. The research works are as follows:1. Based on the magneto-optical waveguide theory, the coupled-mode equations for the CMFBGs are deduced, including the magneto-optical refractive FBG (MrFBG), magnetic-field-induced non-uniform FBG (MnFBG), and multi-subsectional magneto-optical FBG (MMFBG). From the coupled mode equations, the transfer matrixes of MrFBG, MnFBG and MMFBG are also obtained, which is the theoretical foundation of CMFBG's applications in optical sensing, dispersion compensation and clock extraction, and is also the core chapter of this paper.2. According to the coupled-mode equations, the equivalent relationship between the magneto-optical coupling coefficient of MnFBG and the chirp coefficient of the tradition chirped FBG is obtained. By utilizing the transfer matrix method, the equivalence between the MnFBG under linear magnetic field and the non-magnetic linearly chirped grating is verified, and then the dynamic dispersion compensation under the control of magnetic field can be implemented. Based on the above-mentioned equivalent relationship, the Gaussian pulse compression characteristics of the MnFBGs under three magnetic field distributions are also investigated through the Optisystem software and the magnitude of magneto-optical coupling parameter is 1000m-1 in the magnitude of order when the output pulse width is minimum.3. The characteristics of MrFBG and MMFBG are analyzed through the transfer matrix method. It is shown that: the compensation characteristics of the magneto-optical chirped FBG (McFBG) depend on the initial chirp coeffient of the input optical pulse, which can be optimized by the external magnetic field and the the chirp coefficient of McFBG. The tunable dispersion compensation of the MMFBG in the wavelength division multiplexing (WDM) system is also investigated. |
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