A novel ultrasound fibre optic sensor based on a fused-tapered optical fibre coupler

Abstract

This paper describes the design and development of a novel fibre optic sensor to detect ultrasound. It is based on a fused-tapered optical fibre coupler, incorporating mechanical strain amplification in the sensor design. Strain amplification allows the sensor to be used for detecting low acoustic energy, such as acoustic emission emanating from composite materials and structures. This fibre optic ultrasonic sensor has a frequency response range from several tens of kHz to several hundred kHz. The sensitivity of the sensor system was found to be 0.56 V mbar−1 with an acoustic noise floor of 18 µbar at 155 kHz when evaluated in a water bath. The bandwidth of the electrical circuit was in the range of 10 kHz up to 1 MHz.