Effects of optical feedback on the performance of high data rate single-mode fiber systems

Performance measurements data accomplished on a 678 Mbit/s single-mode fiber optic transmission system for various laser diode structures and more importantly under different near- and far-end optical feedback conditions are presented. Specifically, for two integral coupling schemes i.e., the drawn fiber taper with a lens and hemispherically ended graded index fiber lens (GRINFLENS) the near-end optical feedback are modelled and simple method for its experimental assessment are given. Feedback induced variations of lasing spectra and of mode partition noise and their influences on bit error rate (BER) data are experimentally determined for a dispersive single-mode fiber transmission link with the two coupling arrangements. Comparative measurements were done with a butt-coupled fiber and with a non-dispersive fiber system. Furthermore, far-end reflections from a connector joint and their quantitative influence on BER data were investigated.