A method for optical signal amplification in an optical communication system is presented. The optical communication system comprises an optical line terminal, a plurality of optical network units, an optical splitter and a plurality of circulators. The optical network units comprise each an optical amplifier. A first optical signal is sent in a downstream direction from the optical line terminal to a first circulator from the plurality of circulators. The first optical signal is further sent from the first circulator to a first optical network unit from the plurality of optical network units and it bypasses the optical splitter. The first optical signal is amplified in the optical amplifier of the first optical network unit to generate an amplified optical signal. The amplified optical signal is sent from the first optical network unit to the first circulator through the optical splitter and is further sent from the first circulator to a further of the plurality of optical network units.