| Laser ultrasonic is non-contact, can generate ultrasound with narrow pulse, which have very high resolution in time and space. It can be excited in different shape issues. It also can work in high-temperature, high pressure, toxic, radioactive and other harsh environment. Laser ultrasonic is a emerging cross-disciplinary which is good at the research of ultrasonic transmit and material property's ultrasonic nondestructive evaluation.Compared with other ultrasonic detecting methods, Optical fiber interferometer is advantage in small size, light weight, compact structure and sensitive, and Michelson interferometer is one of the best Optical fiber interferometers. Because of the two optical beams through two different optical paths in interferometer, Michelson interferometer is often influenced by environment facts and few of Michelson interferometer is used. So solving the unstable problem is a key for Michelson interferometer application.Firstly, a basic theoretical analysis is carried on the Michelson interferometer and the environmental factor influence is analyzed on the fiber-optic interferometer in this paper. Then, according to fiber-optic Michelson interferometer related principles, the structure of fiber-optic interferometer and the key components of interference system are studied. In this paper, key device and debug the process has done a detailed introduction. The study on phase compensation of Michelson interferometer is proposed. And a phase compensation circuit is produced, which is finally used in ultrasonic detecting. The phase compensation circuit successfully makes the interferometer stable and is successful in eliminating the effects of Environment .The experimental results shows that the Michelson interferometer system can detect ultrasonic signals accurately. At the same time, in order to limit the load on the piezoelectric ceramic voltage, an automatic discharge circuit is designed and used.
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