Studies On Optical Frequency Swept FBG Sensing Interrogation Driven By RF Signal

With the development of FBG sensing technique, the widespread application andproduction of novel types of FBG sensor and the expansion scale of sensing networkhave proposed new challenges to the demand of FBG sensing interrogation. In thisthesis, the wavelength conversion technique based on Single-Side-Band modulator isprofoundly investigated theoretically and experimentally. Furthermore, we utilize theSingle-Side-Band Modulator as main device to build a recirculating frequency shiftersystem and generate the multi-wavelength optical source. At last, a novel FBGinterrogation method is created and experimentally proved based on the recirculatingfrequency shifter. The thesis contains the following aspects:1. Theoretical research about wavelength conversion of Single-Side-Band modulator(a) We do theoretical analysis of the electro-optical characteristic ofSingle-Side-Band modulator, and find the influential elements of the restraint andgeneration of single side band optical wavelength. Besides the operation theory ofwavelength conversion technique based on Single-Side-Band modulator andfactors of noise are investigated.(b) On the foundation of Single-Side-Band-modulator based wavelength conversiontheory, we analyze the possibility and stability of generation of multi-wavelengthoptical source from recirculating frequency shifter system, and search for the wayto restrain the noise.(c) The feasibility of FBG sensing interrogation method based on the technique ofmulti-wavelength optical source generation from recirculating frequency shiftersystem is theoretically analyzed.2. Experimental research of a novel method of FBG interrogation(a) The narrow-bandwidth continuous wavelength conversion using theSingle-Side-Band modulator is experimental researched. The impacts of RF signalfrequency, DC voltage on the effects of wavelength conversion are concreteanalyzed. (b) The multi-wavelength optical source’s wavelength conversion using theSingle-Side-Band modulator is experimental researched as well. And somedeterminants of the stability and effects of the wavelength conversion areinvestigated.(c) We build a recirculating frequency shifter system and realize the generation ofmulti-wavelength optical source with10GHz frequency interval and totally about30channels stable and flat-power-distributed output.(d) By the frequency scanned theory of recirculating frequency shifter system, a novelmethod of FBG interrogation is achieved. The interrogation resolution is0.08nmexperimentally (0.08pm theoretically) and the interrogation frequency is700KHz.Moreover, we compared the results of this interrogation method with the normalones to prove its feasibility.