Splice Loss Calculator

Splicing two fiber ends together always introduces some signal loss, and that loss comes from three distinct physical misalignments this calculator models separately before summing them. Lateral offset loss — cores that aren't perfectly centered on each other — uses a Gaussian mode-mismatch approximation, 4.343 × (offset ÷ mode-field-radius)², where the mode field diameter is 10.4 μm for single-mode fiber (larger than the 9 μm core itself, since light spreads slightly beyond the core boundary) or approximated as the core diameter itself for multimode. Angular offset loss uses a similar squared-error approximation scaled by the core's refractive index and wavelength (1.31 μm for single-mode, 0.85 μm for multimode in this model).

End separation loss models the Fresnel reflection that occurs at each glass-to-air interface when fiber ends don't touch — roughly 0.15 dB per face, doubled for two faces, scaled toward its full value as the gap approaches 10 μm. These three losses sum to your calculated per-splice loss, then get compared against typical and worst-case reference values for your chosen splice method: fusion splices (typically 0.05–0.10 dB) are consistently lower-loss than mechanical splices (0.30–1.0 dB), because fusion actually melts the fibers together rather than clamping them with an index-matching gel. All per-splice figures are then multiplied by your splice count for the link total — remember these are alignment-based estimates, not a substitute for an actual OTDR trace measured after the splice is made.