Research Of General Demodulation Technique For Fiber F-P Sensor And FBG Sensor

With the development of optic fiber communication technology, optic fiber sensors are widely used. With monitoring the changing of optic intensity, wavelength, phase and polarization state, optic fiber sensors can detect many parameters, such as pressure, strain, temperature, etc. They have the advantages of simple structure, easily duplicated, low sensitivity towards magnetic, high insulation and good defending bursting capability. There are two typical optic fiber sensors, fiber F-P (Fabry-Perot) sensor and fiber FBG (Fiber Bragg Grating) sensor. Each has many advantages, and has been already widely used. These two sensors are synchronously demanded in great engineering. Otherwise, existing demodulating method increases the complexity of demodulating system, decreasing dependability and enhancing cost of system. So it is necessary to study general demodulating method for F-P/FBG sensor. So some researches are carried on in this paper.At the beginning of this paper, the principle of many kinds of demodulation methods for fiber F-P/FBG sensors are analyzed and compared. A conclusion is drawn that using tunable F-P filter can realize demodulation for fiber F-P sensors and fiber FBG sensors separately. In order to validate the availability of general demodulation system for fiber F-P/FBG sensors using a tunable F-P filter, wastage characteristic of tunable F-P modulating device and the effect of actual spectrum to sensor output are deeply analyzed, modulating principle based tunable F-P filter is thorough discussed. And considering non-linearity of tunable F-P filter, benchmark compensation for non-linearity demodulating principle is put forward, which using a series of FBG wavelength references as benchmarks. The device of FBG wavelength reference is studied and manufactured, and general demodulation system is designed. SLD light source driving circuit, controlling circuit of FBG wavelength reference and tunable F-P filter are analyzed and designed. Finally, experiments of F-P and FBG demodulating system are carried. Experiments indicate that the performance of these circuits and parts are usable and dependable and such demodulating system is in good working.