Patent ID: 7054522

Claim:
A bidirectional optical recirculation loop transmitting device for transmitting a forward directional optical signal generated from an end and a reverse directional optical signal generated from the other end to the other end and the end, respectively, the device comprising: an optical combiner having four ports which, when receiving an optical signal from a first port and a second port, separately outputs one to a third port and the other to a fourth port and, when receiving an optical signal from the third port and the fourth port, separately outputs one to the first port and the other to the second port; a first optical circulator which receives the forward directional optical signal generated from the end and outputs the received forward directional optical signal to connect to the first port of the optical combiner, and receives the reverse directional optical signal from the first port of the optical combiner and outputs the received reverse directional optical signal to a receiving end of the reverse directional optical signal formed at the end; a second optical circulator which receives the reverse directional optical signal generated from the other end and outputs the received reverse directional optical signal to connect to the third port of the optical combiner, and receives the forward directional optical signal from the third port of the optical combiner and outputs the received forward directional optical signal to a receiving end of the forward directional optical signal formed at the other end; a first connection unit which allows an optical link and the second port of the optical combiner to be in an “ON” connection state during a period from a time point at which the forward directional optical signal is stopped from being input to the first optical circulator to a time point at which the input of the forward directional optical signal resumes; and a second connection unit which allows the optical link and the fourth port of the optical combiner to be in an “ON” connection state during a period from a time point at which the reverse directional optical signal is stopped from being input to the second optical circulator to a time point at which the input of the reverse directional optical signal resumes.