Abstract
We developed a novel fiber-optic acoustic emission (AE) monitoring system and applied this to gas-leak detection. The system is a Mach-Zehnder, homodyne-type optical fiber laser interferometer with a phase compensation feedback circuit. The feedback signal was given by a piezo-actuator which can maintain the system at quadrature condition. The system was demonstrated to measure the in-plane motion of elastic waves with a S/N ratio comparable to that of a commercial piezo-electronic AE sensor. The system can also detect Ao-mode Lamb wave generated by a pulse YAG laser and cylindrical waves produced by lead breaking on a 2-inch steel pipe. We also detected continuous cylindrical waves from gas leakage from a hole of 0.3mm diameter through a 4 inch steel pipe. RMS voltage of the AE signals, monitored by the sensor fiber wound the pipe surface, was found to increase with gas pressure.
