Long distance, high spatial resolution distributed temperature measurement using a graded index optical fiber at 1550 nm

Raman-based distributed temperature sensing (DTS) systems have found widely ranging commercial applications. For extended distance DTS measurement the spatial resolution is sometimes limited through pulse broadening caused by the intermodal dispersion of graded index multimode (GIMM) optical fiber. In this paper we describe the design, manufacturing and performance of a high bandwidth GIMM fiber, with bandwidth optimized at 1550 nm. Using this fiber, we demonstrate distributed temperature measurement with an extended distance of 32 km and spatial resolution of 3 meters. In comparison, the spatial resolution of an OM4 (bandwidth optimized for use at 850 nm) fiber typically used in temperature sensing over 32km is more than 10 meters.