Dynamic strain monitoring by wavelength locking between two fiber Bragg gratings fiber sensing system

We demonstrated a fiber sensing system using the method of wavelength locking of two identical fibers Bragg gratings (FBG) to interrogate the wavelength shift by directly measuring the intensity of the reflection from the sensing Bragg grating. The light source of the fiber sensing system is an EDFA fiber ring laser pumped by a 980 nm laser diode and a narrow bandwidth fiber Bragg grating for the filter of the ring laser resonator. The wavelength shift is converted to the intensity deviation of the reflection from the sensing FBG under strain variation, and is able to achieve real-time sensing of the dynamic strain sensing in civil engineering. The characteristics and key factors to maintain stability of the dynamic strain sensing system are discussed.