Fiber Sensor Based on Interferometer and Bragg Grating for Multiparameter Detection

An integrated in-fiber Mach-Zehnder interferometer (MZI) and fiber Bragg grating (FBG) sensor that can simultaneously detect localized temperature, strain, and ultrasonics is proposed and demonstrated. Using a 60-mm single-mode fiber with a 12-mm FBG spliced to two 3-mm multimode fibers and lead-in and lead-out single-mode fibers, the sensor can discriminate temperature and strain from the responses of the MZI and the FBG to the two static parameters. Ultrasonic signals are directly recorded as high-frequency voltage vibration by demodulation of Bragg wavelength shift using a corresponding sensing system. The overall system shows high practical potential for use in nondestructive testing.