Optical fiber acoustic sensing multiplexing system based on TDM/SFDM

We propose a system of time-division multiplexing (TDM) and spatial frequency-division multiplexing (SFDM).Extrinsic Fabry-Perot interferometric sensors are applied to detect weak acoustic signals.The broadband source is employed, the light from it is modulated by a pulse signal sequence and is efficiently amplified by semiconductor optical amplifiers.Experimental results show that the equivalent noise pressure spectrum level is -97.2 dB re 1 rad/√Hz below 1250 Hz, and the cross talk between two sensors in one TDM channel is -32.7 dB with a cavity length difference of 60 μm.The number of sensors in this multiplexing system can theoretically reach 160.