Optical transmission system

摘要

The present invention provides a low-cost optical transmission system using a plurality of subscriber lines which is capable of efficiently utilizing an optical transmission path. A communication status observing section (116) in a transmitting device (1) classifies subscribers into a plurality of groups based on a communication status at each subscriber end, and outputs constellation level information and level information which are different for each group. For each constant cycle, a modulation control section (117) and a gain control section (118) respectively set a QAM constellation level and a signal level which are different for each group and used in a basic modulating section (103).