Universal model for splice loss in few-mode fibers

We employ confluent hypergeometric functions to simplify the expression of modal fields, thereby establishing a general theoretical model for splice loss in few-mode fibers (FMFs). This model: (1) unifies the splice loss of all LP modes as a function of d/ω₀ (axial offset / fundamental mode field radius), enabling the estimation of all-mode splice losses once d/ω₀ is determined; (2) proves that the conventional backscattering method, which infers splice loss from power drops, does not apply to FMFs. Experimental results show that the model predictions exhibit a maximum error of less than 0.24 dB, whereas backscattering-based measurements deviate by up to 2.45 dB. The model enables rapid splice-loss prediction and derives the axial-offset tolerance under a specified loss constraint, thereby guiding splicing-parameter setting and engineering quality control.