Underwater acoustic sensor using optical fiber Bragg grating as detecting element

An underwater acoustic sensor using an optical fiber Bragg grating (FBG) in the reflection mode is examined to characterize the sensor under various conditions. For the fabrication of the sensor: one end of the FBG fiber pigtail is terminated by a low reflection facet such as an APC connector or an angled cut fiber and the output signal is extracted by an optical circulator of low back reflection. The sensor demonstrated as good performance of fundamental characteristics as a FBG acoustic sensor in the transmission mode. Considering many of the basic properties such as sensitivity, linearity, frequency response and compactness, an acoustic sensor using a FBG is as good as or better than a conventional PZT acoustic sensor.