Fiber Bragg grating ultrasound sensor for process monitoring and NDE applications

An ultrasonic sensor for detection of ultrasonic waves in liquids and solid structures is proposed. The sensor contains a fiber probe which is a single mode fiber with a Bragg grating; a tunable narrowband laser source; and a photodetector. When an ultrasonic wave impinges the fiber probe the pitch of the grating is modulated by the acoustically induced mechanical strain through the elasto-optic effect. The corresponding changes in reflectivity of the grating are detected by a photodetector. Main advantages of the sensor are direct modulation of laser intensity by ultrasound, simplicity of design, and high sensitivity over broad frequency range.