Coherent NuSENSOR pure silica core multimode fiber is immune to the damaging effects of hydrogen ingression, enabling Raman based distributed temperature sensing in harsh environments. This 0.20 NA fiber features a graded refractive index profile with a 50 μm core diameter and a 125 μm clad diameter. The fibers are available with a polyimide or mid-temperature acrylate coating and also available in combination with a hermetic carbon coating. NuSENSOR multimode fiber is manufactured in-house, and every process step is monitored and controlled providing high bandwidth and low attenuation. As with all Coherent fibers, this multimode fiber provides tight tolerance optical and geometrical specifications measured at the application critical wavelengths. For high H2 partial pressure and elevated temperature up to 300°C (150°C for MTA) you will find no measurable induced loss for typical sensing applications.