Planar flexible fiber-optic acoustic sensors

Abstract

The acoustic sensitivity of optical fibers is considered analytically. High sensitivity is obtained with low bulk modulus, very thick polymeric coatings. The fiber coatings play an important role in determining the fiber acoustic sensitivity. The very thick coating limit is realized by embedding optical fibers in an appropriate elastomer (polyurethane). A planar flexible fiber-optic interferometric acoustic sensor is developed by wrapping optimized single-mode fibers in a planar spiral form, and then embedding the fiber in a thin polyurethane layer. The acoustic sensitivity of the sensor is found to be high, and frequency (0.2-2.5 kHz) and static pressure independent. The sensor is found to be compatible with water, and is compared favorably to that of a planar polyvinylidene fluoride sensor of similar geometry.< >