Frequency-shifted multiwavelength FBG laser sensor

We propose and demonstrate a novel frequency-shifted FBG (fiber Bragg grating) laser sensor system. It is composed of an EDFA (erbium-doped fiber amplifier) broadband light source, 3-FBG array, single mode fiber, circulator, acousto-optic modulator (AOM) and an output 3dB fiber coupler. The frequency-shifted feedback by the AOM allows the laser to operate at multiwavelength at room temperature. Compared to a conventional passive system, the optical signal power and SN ratio were enhanced by 20.1 dB, and 17.0 dB, respectively, and the linewidth was reduced to 1/5.3.