Fast-Fiber is also involved in specialty fiber development, including rare-earth doped fibers for telecom amplifiers, UV and IR fibers, polarization preserving highly birefringent and low-birefringent fibers for various sensor applications, fibers with custom-made profiles (two-core, double clad, "holey" fibers) and with customized jacket materials (polyamide, metal, plastic) and consulting services on polarization problem handling in high bit-rate telecom systems (compensators, isolators, circulators, PMD modeling).