Return loss characteristics of optical connectors

This paper describes the return loss characteristics for four typical contact type connectors : perpendicular and oblique endface connectors employing either physical contact or contact via index matching material. The high index layer on the polished fiber endface and the index matching material, which are important connector parameters, are investigated by measuring the return loss from one perpendicular fiber endface coated with the material and by etching the fiber endface. It is useful to apply two materials with different refractive indices to derive the refractive index and thickness of high index layers on perpendicular fiber endfaces. The index matching material we use has a refractive index of 1.467 at 20 °C and a thermal coefficient of -2.9 x10 -4 /° C at 1.3 μm. We performed return loss calculations and experiments of the four contact type connectors. The worst value at any temperature from -40 to 80 °C can be estimated, by measuring the return loss of these connectors at room temperature.