High spatial resolution and intrinsically strain-insensitive distributed temperature sensing based on stimulated Brillouin scattering in gas

Temperature/strain cross sensitivity is a long-standing issue in Brillouin-based distributed sensors, impairing the reliability of such sensors. So far, all the proposed methods perform the discrimination by measuring two quantities showing distinct responses to temperature and strain. Distributed Raman sensing enables temperature measurement without strain sensitivity. However, due to its weak signal intensity resulting from the principle based on spontaneous scattering, the spatial resolution is typically limited to ∼ 1 m. Here, for the first time, we use stimulated Brillouin scattering in gas-filled hollow-core photonic crystal fibers for distributed temperature sensing and we demonstrate ∼ 1 cm spatial resolution and 0.3°C temperature resolution fully free of strain cross sensitivity. Substantially higher performance is obtained thanks to the higher Brillouin gain, narrower gain linewidth and relaxed optical power restrictions when compared to solid silica single-mode fiber. This opens a new avenue in high performance distributed fiber sensing based on gas nonlinear optics.