Effect of surface roughness profiles on optical characteristics of plasticsplit sleeves for single-mode fiber-optic connectors

We successfully fabricated split alignment sleeves for single-mode operatio n with the injection-molding technique using both thermosetting epoxy resin and thermoplastic polyetherimide (PEI) resin. The relationship between the surface smoothness and the connection-loss characteristics of these inject ion-molded plastic sleeves was investigated. We made two-dimensional contou r maps of the outer and inner surfaces of the plastic sleeves using the mea sured surface roughness. There were many contour lines on both the outer an d inner surfaces of the PEI sleeve. In contrast, the epoxy sleeves had very smooth surface profiles. An offset Delta (r) was estimated by using the in ner-surface roughness data of the sleeve-ferrule contact regions. The conne ction loss of the sleeve increased as the Delta (r), value increased. The m easured losses agree fairly well with the theoretical losses estimated by u sing the a, values. The PEI sleeves exhibited large Delta (r), values, and one-third of them had large connection losses of > 0.5 dB. In contrast, the epoxy sleeves had very small Delta (r), values of < 0.6 <mu>m, and exhibit ed an average loss of < 0.1 dB.