Study On Laser Ultrasound Detecting With Fiber Interferometer

Fiber interferometer is compatible to be used in laser ultrasound detection as it is small volume, low weight, compact structure and high sensitivity. However, any unsteadiness of phase and polarization of the light could bring the unsteadiness of the interferometer due to environment factors. So keep the interferometer steady is in a critical position in the field of laser ultrasound detection with fibre Michelson interferometer.Traditional fiber Michelson interferometer used to 2×2 coupler, the feasibility of laser ultrasound stably detecting was demonstrated by a new type fiber Michelson interferometer with 3×3 coupler in this paper. Firstly the advantages is discussed. And then the design and execution were introduced of the laser and the servomechanism used in this experiment. And a new method was brought forward to measure phase-shift of the piezoelectric phase modulator, which is more exactly and able to reiterate as compared with traditional methods. An experiment system has been designed, and a phase-shift coefficient was gotten of one kind of PZT used in the servomechanism of fiber Michelson interferometer. At last, ultrasound vibration detection experiment was demonstrated by the fiber Michelson interferometer with 3×3 coupler, the results shows that, the new interferometer is able to detect CW and pulse ultrasound vibration well.