Patent ID: 7548693

Claim:
A relay transmission apparatus optically connected to first and second transmission routes that are different from each other, comprising: a first regenerating unit adapted to regenerate an optical signal input from the first transmission route and output a regenerated drop signal as a first signal; a second regenerating unit adapted to regenerate an optical signal input from the second transmission route and output a regenerated drop signal as a second signal; a first branching unit adapted to branch a power of the first signal from the first regenerating unit into two branched first signals; a second branching unit adapted to branch a power of the second signal from the second regenerating unit into two branched second signals; a first relay transmitting unit adapted to optically transmit one of the branched first signals to the second transmission route; a second relay transmitting unit adapted to optically transmit one of the branched second signals to the first transmission route; and a protection process unit adapted to selectively output either the other of the branched first signals or the other of the branched second signals as a drop signal, wherein the first regenerating unit includes a first optical-to-electrical conversion unit that converts the optical signal from the first transmission route into an electrical signal and a first drop signal generating unit that generates the regenerated drop signal output as the first signal based on the electrical signal from said first optical-to-electrical conversion unit, and the second regenerating unit includes a second optical-to-electrical conversion unit that converts the optical signal from the second transmission route into an electrical signal and a second drop signal generating unit that generates the regenerated drop signal output as the second signal based on the electrical signal from said second optical-to-electrical conversion unit.