Ultra thin fiber laser accelerometer for structure vibration detection

Accelerometers are often used in structural health monitoring, smart structures, and aircraft damage detection. In this paper, an ultra thin fiber laser accelerometer (FLA) for structure vibration detection based on a flat diaphragm is presented. This accelerometer uses an flat diaphragm to transfer the acceleration-induced displacement of the mass to the axial elongation of the fiber laser. The flat diaphragm is clamped by the sensor shell to reduce the transverse sensitivity. The interrogation of the fiber laser accelerometer is achieved by using phase generated carrier (PGC) demodulation. A piezo-electric fiber stretcher in one of the unbalanced Mach-Zehnder interferometer (MZI) arms in the demodulator induces a phase-shift carrier signal on the sensor output signals that enables passive recovery of dynamic phase-shift information. This set-up uses a commercially available Dense Wavelength Division Multiplexer (DWDM) as a wavelength filter at the output of the MZI to interrogate multiple sensors. Both theoretical and experimental investigations are presented in this paper. The result shows that the proposed accelerometer has a high sensitivity and a flat frequency response. Owing to the greater deformation of the diaphragm with a mass at its center, ultra thin dimensions have been achieved.