Playing with fire and fibers

Annealing optical fibers has made the optical-fiber current sensor practical for monitoring and diagnostics by utility companies. To produce an annealed-fiber coil for this application, the annealing process must be held within time and temperature bounds or devitrification and OH absorption will degrade coil performance. Annealed-fiber devitrification can produce other useful fiber components, such as a fiber depolarizer and increased photosensitivity for FBG production