US Patent 7672588 Ring optical transmission network access node

A ring optical transmission network access node (ANi) comprises:two identical band splitters (BSa, BSb), each provided with homologous first, second and third ports (Ba, BWa, BPa; Bb, BWb, BPb),a first coupler (CW) coupling the second port (BWb) of the second splitter (BSb), on the one hand, to the second port (BWa) of the first splitter (BSa) via a first channel and, on the other hand, to an access point (A2) via a second channel,a second coupler (CP) coupling the third port (BPa) of the first splitter (BSa), on the one hand, to the third port (BPb) of the second band splitter (BSb) via a first channel and, on the other hand, to another access point (A1) via a second channel.