Modular DAS demodulation system based on ultra-weak fibre Bragg grating

Abstract

Aiming at the requirements of low power consumption, miniaturization, and massive data processing, a modular distributed optical fibre acoustic sensing (DAS) demodulation system based on ultra-weak fibre Bragg grating (UW-FBG) is proposed. A highly integrated circuit and embedded system is used for the time-domain positioning and data acquisition of the gratings. Field programmable gate array (FPGA) demodulates the phase changes of each sensing section in real time. The demodulation outputs are uploaded through a Gigabit Ethernet connection. Through innovative software and hardware design, the demodulation system power consumption is less than 20 W, and the device volume is 250 mm× 180 mm× 45 mm, and the output data size is about 2.6% of the conventional methods. All the outputs are then tested on a piezoelectric transducer (PZT) platform. Results show that the background noise within 5 Hz–1280 Hz range is 2.16 pε/√(Hz), and the strain sensitivity reaches 484 pε/√(Hz)@200 Hz. The correlation coefficient of voltage and phase is 0.9991, which shows good linearity. Combined with a common commercial laptop to demodulate the micro-vibration signals, this system could provide a cost-effective scheme for acquiring acoustic-level micro-vibration signals and on-line field monitoring.

Pilot-scale testing of natural gas pipeline monitoring based on phase-OTDR and enhanced scatter optical fiber cable

“…Therefore, to achieve better sensing performance, increasing the fiber backscattering signal over the longer fiber lengths is crucial. In the literature, several works have been proposed to enhance the backscattering signal, such as weak fiber Bragg grating (FBG) arrays 10 , 11 , ultra-short and random FBGs 12 , 13 , and localized reflectors 14 , 15 . In these methods, the number of reflectors or FBGs are limited to less than a hundred per fiber which restricts longer distance pipeline monitoring applications.…”