Ultrafast Interrogation of Fiber Bragg Grating Sensors
Real-time diagnostics of fast-vibrating objects, such as a running aircraft engine, relies on high-speed sensor interrogation systems. Most of the fiber Bragg grating (FBG) sensors are functioning based on wavelength modulation, in which the sensed information is directly encoded as the grating wavelength change. To monitor the wavelength shift of an FBG, various FBG sensor interrogation techniques have been developed, with the maximum interrogation speed of tens of kHz.
Temporal-spectroscopy technique using a chirped optical pulse to map the optical spectrum to a temporal waveform has been a promising technique for FBG sensor interrogation in the megahertz regime. By applying chirped pulse compression technique in the temporal-spectroscopy-based FBG interrogation system, both spectral resolution and signal-to-noise ratio can be improved. Most recently, to overcome the fundamental tradeoff between the interrogation speed and resolution in a temporal-spectroscopy-based FBG interrogation system and that between the measurement resolution and dynamic range in a dual-wavelength heterodyne-based interrogation system, a novel technique to achieve ultrafast and ultrahigh-resolution interrogation of FBG sensors based on interferometric temporal spectroscopy has been proposed and experimentally demonstrated.