Performance of low-loss, high strength optical fiber splices is analyzed using a parametric model that relates losses with the critical splicing conditions such as initial misalignment; prefusion condition; pressure applied between fiber before fusing, PA ; fusing temperature, T ; and time, t. Fusion time is optimized for minimum splice loss via considerations of the forces due to PA, thermal expansion, and surface tension of the viscous melted glass in the fiber. In silica fibers, the critical conditions of splicing for a minimum t and splice loss are: PA 20 g and T 2000 to 2150 °C. Although t can be reduced further at higher T, the tensile strength of the spliced zone becomes poor. For the best initial alignment and prefusion conditions achieved in the laboratory, fusion splices show an average loss of 0.12 and 0.02 dB for 10/125 pm and 50/125 pm fibers, respectively ; and a maximum tensile strength of 0.65 kg when fused at t of the order of (1.8-3.0) sec. Fiber breaking strength can be increased fivefold, provided the spliced zone is reinforced with chemical adhesive followed by polyethylene(PE) shrinkable tube and solid packing. Prooftesting of fused fiber splices subjected to a variety of adverse conditions (extreme temperatures, humidity, and submersion) assured the long-term reliability of the reinforced splices. Performance of fusion splices thus fabricated and lifetested are discussed.