A Compact DAS Based on a Low Phase Noise DDS and Mini-EYDFA for Real-Time Vibration Measurements

We report on the design of a compact source for a distributed acoustic sensor (DAS) using a miniaturized erbium-ytterbium-doped fiber amplifier (EYDFA) commonly used in CATV networks and an integrated, low-phase-noise direct digital synthesis (DDS). A DDS module that can generate readily programmable probe waveforms with a bandwidth of up to 1.4 GHz is synchronized with a NI-PXIe system for real-time acquisition of traces at a rate of up to 200 MS/s in a scheme that enables measuring vibration signatures with a bandwidth of up to 4 kHz at a distance of 9.71 km, with an SNR of
$\sim 24\text{dB}$
without trace averaging. The proposed configuration simplifies the source used in DAS systems, paving the way toward further miniaturization of interrogation units and their scalable commercialization for wider use in various safety and integrity monitoring applications.