Study Of Sampled Grating Reflective Spectrum Based Photonic Crystal Theory And Fiber Grating Sensing Technology

As sampled fiber Bragg grating has multichannel filtering, fine structure, flexibility, good compatibility, low insertion loss and extremely good wavelength selectivity, it was attended currently. Now it has become novel passive device for to realize optical modulation. Due to above-mentioned characteristics, sampled fiber Bragg grating has much important application and potential in multi-wavelength laser, wavelength-division multiplexer and demultiplexer, re-configurable optical add-drop multiplexer, fiber sensor, multi-channel dispersion compensator, encoder and decoder etc. Sampled grating reflective spectrum based photonic crystal theory and sampled fiber Bragg grating simultaneously measuring strain and temperature sensing characteristic were mainly researched in the paper. Details include the followings.In the paper basically theory of fiber Bragg grating and its sensing characteristics were introduced. Strain and temperature sensing model was deduced. The reflective spectrum of sampled fiber Bragg grating was analyzed and simulated.The effect of sampled fiber grating's parameters on reflective spectrum was analyzed. Parameters include length, period, sampled rate, the refractive index modulation depth, apodization coefficient and chirp coefficient.The relationship of sampled fiber Bragg grating's geometric and physical parameters and reflectivity, bandwidth and channel numbers was discussed. This can provide foundation to design sampled fiber Bragg grating.Theoretical analysis of the photonic crystal method was introduced. Methods include FDTD, transfer matrix method and plane wave expansion method. sampled fiber bragg grating was assumed as one-dimensional dual photonic crystal with a large size defect. Sampled fiber Bragg grating was researched by means of transfer matrix method of photonic crystal theory.The effect of sampled fiber grating's parameters on reflective spectrum was analyzed from photonic crystal theory. Result showed that sampled fiber Bragg grating had many reflective peaks. Its reflectivity, center wavelength, reflective peak intervals and band width change with the grating parameters. Parameters include grating length, duty ratio of the material with high dielectric constant, and index modulation depth and period.Results follow the conventiona1 couple mode theory. The distributed fiber Bragg grating simultaneously measuring strain and temperature system is presented in this paper. Light source adopted clock pulse wide band source. The system integrates time division multiplexing and wavelength division multiplexing. Different cladding diameter fiber works as sensing probe. It can realize measurement of strain and temperature simultaneously. It can solve strain and temperature cross sensitivity problem.Demodulation system adopts arrayed-waveguide grating. The feasibility of the system is confirmed from theoretically.According to effect law of sampled fiber Bragg grating parameters on its reflective spectrum, sampled fiber Bragg grating simultaneously measuring strain and temperature sensing model was researched using regression analysis method. Sampled fiber Bragg grating sensing characteristic experimental system was designed. Sensing experiment was made. Experimental data were analyzed and disposed. Each several part of experimental system was regulated. Results were same as those from simulation experiment.At last experimental system error were analyzed, each factor of influence system measurement and improvement method were analyzed.