An all-fibre micro-vibration sensor multiplexing method based on frequency modulated continuous wave (FMCW) and laser intensity modulation

The techniques of frequency modulated continuous wave (FMCW) and laser intensity modulation by a linear saw tooth-swept voltage controlled oscillator (VCO) are integrated with a kind of all-fibre micro-vibration vector sensor in this research. A senor multiplexing method aimed at detecting multipoint feeble vibration signals using only a long single mode fibre (SMF) is reported. In this system, a high sensitive photodetector is employed to execute photoelectric conversion. Its output is subsequently mixed with a branch of reference saw tooth chirped signal so as to obtain beat components, which provide information necessary for locating the position of each sensor. Theoretical analysis of the signals from each part is made in detail. The simulation results are exhibited and reveal the effectiveness and feasibility of this method.