Directional acoustic signal measurement based on the asymmetrical temperature distribution of the parallel microfiber array

A parallel microfiber array for the measurement of directional acoustic signals is proposed and experimentally demonstrated. Two microfiber Bragg gratings (micro-FBGs) in single-mode fibers were placed on two sides of a Co²⁺-doped microfiber, forming an array of three parallel microfibers. The micro-FBGs can measure the temperature difference between the two sides of the Co²⁺-doped microfiber through interrogation of the matched FBGs. Due to the asymmetrical temperature distribution of the Co²⁺-doped microfiber under the applied acoustic signal, sound source localization can be realized through the acoustic particle velocity. The experimental results show that an acoustic particle velocity sensitivity of 44.2 V/(m/s) and a direction sensitivity of 0.83mV/deg can be achieved at a frequency of 1000 Hz, and the sound source localization has been realized through the orthogonal direction responses of two crossed Co²⁺-doped microfibers. The results demonstrate that the parallel microfiber array has the ability to recognize orientation, offering potential for directional acoustic signal detection with miniature size.