Patent ID: 7127170

Claim:
A transmission apparatus connected to an optical signal transmission line, first network and second network, comprising: an optical frequency selection unit for selecting a first optical signal of a first optical frequency and a second optical signal of a second optical frequency among an optical frequency division multiplexed signal received from said optical signal transmission line and transmitting said selected first and second optical signals separately, a first optical frequency conversion unit connected to said optical frequency selection unit and said first network for converting a frequency of said first optical signal from said first optical frequency to a third optical frequency and transmitting an optical signal of said third optical frequency toward said first network, a second optical frequency conversion unit connected to said optical frequency selection unit and said second network for converting a frequency of said second optical signal from said second optical frequency to said third optical frequency and transmitting an optical signal of said third optical frequency toward said second network, wherein said first optical frequency is allotted for transmissions of signals from said optical transmission line to said first network, said second optical frequency is allotted for transmissions of signals from said optical transmission line to said second network, and said third optical frequency is allotted for transmissions of signals from said transmission apparatus to said first and second networks.