Efficient laser-diode-single-mode-fibre coupling using two confocal lenses

Abstract

A new method for coupling a laser diode to a single-mode fibre is described. It uses a spherical ruby lens and a g.r.i.n. rod lens, which are positioned nearly under confocal conditions. A high coupling efficiency of more than −3 dB has been realised, and stringent alignment tolerances required for conventional coupling circuits have been overcome.