Degradations in Gbit/s DFB laser transmission systems due to phase-to-intensity noise conversion by multiple reflection points

Severe system degradations and bit error rate floors are observed in Gbit/s fibre transmission systems due to the interferometric conversion of laser phase noise to intensity noise by multiple reflections from connectors and splices. Studies of penalties as a function of both the magnitude and number of reflections indicate that fibre joints with guaranteed minimum return losses of better than 20 dB may be required for high-speed direct detection systems as well as future coherent systems, even though optical isolators may be employed in such systems