A Novel Interrogation System for Large Scale Sensing Network With Identical Ultra-Weak Fiber Bragg Gratings

A novel interrogation system for large scale sensing network with identical ultra-weak fiber Bragg gratings (FBG) is proposed, theoretically analyzed and experimentally studied. Based on time-division multiplexing (TDM) technique, two semiconductor optical amplifiers are introduced to the interrogation system to achieve fast and flexible demodulation. A simulation depending on the formula of reflected pulse spectra, derived by analyzing the source of disturbance along the optical path, is processed for evaluating the performance theoretically. Experiment was demonstrated on an 843 serial FBGs sensor network, with a peak reflectivity of -40 to -45 dB and a spatial resolution of 2 m along a single optical fiber by launching a 50 kHz scanning frequency with 20 ns effective pulse width to the system. Due to the low crosstalk, it is possible to integrate several thousands of FBG sensors in a single optical fiber.