Patent ID: 6882801

Claim:
An optical transmission system comprising: a main unit which inputs a first electric signal and outputs a plurality of first optical signals, and inputs a second optical signal and outputs a second electric signal; a plurality of sub units, each of which inputs one of said plurality of first optical signals from said main unit and outputs a third electric signal, and inputs a fourth electric signal and provides said second optical signal to said main unit; and a plurality of optical fibers, each of which connects said main unit and said plurality of sub units, wherein said main unit comprises: an electro-optical converter which inputs said first electric signal and converts said first electric signal to a first optical signal; a coupler unit comprising: a first optical coupler which divides said first optical signal into a plurality of first optical signals; a plurality of input/output ports, each of which outputs one of said plurality of first optical signals divided by said first optical coupler to one of said sub units through one of said optical fibers and inputs said second optical signal from one of said sub units through one of said optical fibers; an output port which outputs said second optical signal; and a second optical coupler, provided between said first optical coupler and said input/output ports, which provides said first optical signal to said input/output ports and said second optical signal to said output port; an opto-electric converter which converts said second optical signal output from said output port to a second electric signal; and an electric signal output terminal which outputs said second electric signal.