Low-Loss Random Fiber Gratings Made With an fs-IR Laser for Distributed Fiber Sensing

Abstract

By using the plane-by-plane grating inscription method with an fs-IR laser, random fiber gratings with low laser-induced loss were fabricated in SMF-28 fiber for distributed temperature sensing. Compared to conventional random gratings having broadband backscattering enhancement, the demonstrated random fiber grating has a well defined narrower bandwidth of backscattering enhancement, higher laser-induced backscattering level, and lower laser-induced loss, which are critical for long-haul distributed fiber sensor systems with high measurement accuracy. Experimental results showed that by using fabricated random fiber gratings along with the technique of optical frequency-domain reflectometry, a distributed temperature fiber sensor could be realized having a gauge length of 10 mm, standard deviation of temperature measurement as low as 0.00085 °C, and laser-induced loss of 0.08 dB/m.