Large-scale multiplexed weak reflector array fabricated with a femtosecond laser for a fiber-optic quasi-distributed acoustic sensing system.

ABSTRACT

In this Letter, we propose a large-scale multiplexed weak reflector array fabrication method by using a femtosecond laser with relatively high reflectivity and low transmission loss. This kind of weak reflector array can be used in a quasi-distributed acoustic sensing system as sensing fiber instead of single-mode fiber (SMF) to achieve an ultrahigh signal-to-noise ratio (SNR). An automated fabrication system is designed, and a reflector geometric structure with high reflectivity and low scattering loss is designed based on this system. As a prototype to demonstrate the performance, one thousand weak reflectors are written on the SMF with an interval of 10 m, a reflectivity around -42dB, and a transmission loss of 0.34 dB/km. In comparison to the method of using SMF as the sensing fiber, at least 15.8 dB enhancement to the SNR can be achieved by using the reflector array as the sensing fiber.