Experimental Study On Static/Dynamic Gain Equalizer Based On Novel Long Period Fiber Grating

Based on the new fabrication method of long period fiber grating (LPFG) induced by high frequency CO2 laser pulses invented by my supervisor-professor Yunjiang Rao, Ran Zeng-ling and the author studied the fabrication process of the novel LPFGs under the supervision of prof. Rao. The automatic fabrication method of the novel LPFGs controlled by the computer becomes reliable through many times experiments. The comparison of fabrication methods of LPFGs reported in the resent years and the forming mechanism of the novel LPFG are discussed in this paper. The tunable optical characteristics of the novel LPFGs are recognized during the study of their optical characteristics: (1).The relationship between the resonant amplitude and the applied curvature radius in the bend-sensitive orientation of the novel LPFGs is linear, (2). The relationship between the resonant amplitude and the applied transverse load in the wavelength-insensitive orientation of the novel LPFGs is linear, (3). The relationship between the resonant wavelength shift of the novel LPFGs and the applied temperature is linear. All these unique characteristics are the application fundament of the novel LPFGs to optical communication and sensor systems.The works of this thesis is summarized as follows: (1). The gain spectrum of an EDFA is flattened using the novel LPFG statically, and the flatness of less than 0.8dB in a wavelength the range of 32nm at the C-band was obtained. (2). The method of dynamic gain equalization based on the temperature and bending characteristics of the novel LPFG was demonstrated. Another method based on the temperature and transverse load characteristics was also demonstrated. The resonant amplitude and wavelength of the LPFG were adjusted by applying bend or transverse load and temperature to the LPFG, respectively. (3). The flattening arithmetic of an EDFA was presented based on the inter-correlative function between the gain spectrum function of the EDFA and that of the reserve transmission spectrum of the LPFG. For optimal matching between the two spectra, the flattening arithmetic calculates the variation of the resonant amplitude and wavelength of the LPFG. (4). A dynamic gain equalizer device including control circuit, mechanical structure and control program was designed using a cooler and a PZT. A dynamic gain equalizing experiment of the EDFA using the designed dynamic gain equalizer was accomplished, and a 1.2dB flatness in the range of 32nm at C-band was obtained. Finally, some future improvements were discussed in thisthesis.