Modal Analysis of Loss and Mode Mixing in Multimode Parabolic Index Splices

In this paper we present an electromagnetic modal theory for characterizing parabolic-index multimode fiber splices with either intrinsic or extrinsic mismatches. The theory agrees with previously published theoretical results for transverse offset using a uniform power distribution. It also agrees with new experimental measurements made with a long, spliced input fiber using a published, theoretical, steady-state modal power distribution. This modal theory predicts, and experiment confirms, a previously unreported periodic fluctuation in splice loss as a function of wavelength for intrinsic parameter mismatch. The analysis also predicts a large degree of mode mixing for transverse offset but negligible mode mixing for parameter mismatch in typical multimode fiber splices.