水中計測用干渉計型光ファイバAEセンサの無指向性化

抄録

Directivity of the Mach-Zehnder interferometer type optical fiber acoustic emission (AE) sensor having the U-shaped sensing region for the use of underwater measurement was discussed. It was demonstrated that detected waveforms by the sensor depend on the incidence angles of the AE waves although the amplitude of the first peak in the waveform caused by the arrival of the AE wave indicates no change. It was also found that directivity of the sensor tends to disappear by setting masking tubes on the sensing fiber that avoid the influence of undesirable elongation of the sensing region. Nearly omnidirectional sensor was successfully made with the effective ratio for receiving waves given by masking tubes was less than 50%. It was concluded that the J-shaped sensing region is preferable for waveform analyses by taking sensitivity of the sensor into accounts.