Pressure measuring device and method of fiber difference interference

The invention provides a pressure measuring device and method of fiber difference interference. The device comprises a fiber laser unit, a fiber coupling unit, a reflection difference unit, a fiber beam expanding and collimating unit, a photoelectric detection unit, a storage unit and a signal processing unit; and the reflection difference unit includes a reflection phase grating of a special structural design, and used to cut reflected light waves. The reflection phase grating includes two non-light-transmission parts and two reflection light parts in one period; the two reflection light parts include a direct reflection part (without phase delay) and a pai-phase delayed reflectin part; and the duty ratio of the reflection phase grating is 1/2, namely, the proportion of the size of the non-light-transmission parts to that of the reflection light parts is 1/2. The device of the invention can be used to realize pressure measurement of high temperature and high corrosion, and has advantages including being resistant to electromagnetic interference and radiation. In addition, a differential pressure type flowmeter is combined to realize high-temperature medium flow measurement.