Photorefractive Effect And Its Application In Wavelength Division Multiplexing Technology

In this thesis, by contrasting, I indicate some advantages and disadvantages of several kinds of WDM respectively. Based on volume grating having strict wavelength and angle selectivity, put forward a new method of making Wavelength division multiplexing—volume holographic wavelength division multiplex. Meanwhile I discuss some issues about this kind of WDM such as design principal, facture method and its properties.the main contents are as follows:1. The mechanisms of the photorefractive effect and the creation of photorefractive grating are explained .Based on the coupled-wave theory, the Bragg diffraction efficiency, the angle selectivity and wavelength selectivity of volume holographic Bragg gratings formed in photorefractive crystals are analyzed. According to the Bragg's diffraction formula, the relation of the demultiplexing angle on communication wavelengths to the writing angle of volume holographic Bragg gratings, and the Bragg mismatching value during wavelength demultiplexing with wide spectra by employing volume holographic Bragg gratings are discussed.2. Writing angle, channel space, rotation angle, in LiNbO₃:Fe:Zn crystal as the device of wavelength-division multiplexing, are discussed in theory. And the relation of the thickness of grating and the minimum channel space is discussed, too.3. The holographic time constants were gained by recording and erasing a single grating in a slice of LiNbO₃:Fe:Zn crystal. According to the recording and erasing time constants, the exposure time schedule of superimposed gratings was discussed. The pacing technology in making the WDM device such as selecting recording material, making sure recording geometry , exposure method and so on are analyzed further. The research conclusions are as follows: the Fe and Zn doped LiNbO₃ should be considered at first as holographic recording material in our system.4. The recording approach of the multiple volume holographic Bragg gratings in LiNbO₃:Fe:Zn crystal was investigated. Concretely designing scheme of holographic wavelength demultiplexing based on the technique of volume holographic gratings is put forward. On the base of this experiment, the experiment shows the feasibility of the multiple volume holographic Bragg gratings using in the wavelength division multiplexing.A experimental scheme of selective 1×2 holographic optical self- thoroughfare based on volume holographic grating is designed, and compared the result of the experiment with the theory.