Improved optical fiber coupling reliability is realized by improving structures and materials used at the fiber joint. When ceramic ferrules are used at the fiber joint, the penetration of a UV-cured optical adhesive between the ceramic ferrules and the fiber ends is avoided or prevented, while an anti-reflective coating, an uncured optical adhesive, or a refractive index matching gel may be applied between the ceramic ferrules. When glass ferrules are used at the fiber joint, the UV-cured optical adhesive may be applied and fully cured between the glass ferrules and the fiber ends.