YOFC's spun fibre is manufactured by spinning a polarization maintaining preform during the fibre drawing process, featuring high mechanical reliability and geometric consistency. The preform is deposited through Plasma Chemical Vapor Deposition (PCVD) process, which enables a precise refractive index profiles and dimensional tolerances of the fibre. Excellent environmental immunity and circular polarization-maintenance performance are obtained by design to meet the requirement of applications, such as fibre optic current transformer (FOCT).With dual-layer, UV-cured Acrylate coating, YOFC spun fibre has high environmental stability performance over the temperature range of -45℃ to +85℃ (-49 ℉ to +185 ℉ ).