Modified single crystal fibers for distributed sensing applications

Abstract

Single crystal fibers like those made from sapphire are capable of operating at higher temperatures than conventional silica-glass-based fibers. This work aims to construct single-crystal optical fiber sensors capable of providing environmental data in combustion, high-temperature chemical processing, or power generation applications where temperatures exceed 1000 °C and standard silica fibers cease to provide useful information. Here, we explore the functionalization of single crystal fibers using methodologies intrinsic to the crystal growth process or with methods which do not severely reduce their operating temperature range. While operating a laser-heated pedestal growth system to produce single-crystal optical fibers from rod feedstock, we continuously vary parameters such as fiber diameter to produce novel single-crystal linear distributed-sensing devices. The spectral characteristics of those modified devices, along with sensing performance in a high-temperature harsh-environment are reported. Finally, a technique for increasing the intrinsic Rayleigh backscattering using femtosecond laser irradiation is discussed for temperature sensing applications.