| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the need for an optical attenuator for level adjustment, to set a reception level to an appropriate value and to eliminate the deterioration of quality by means of the attenuator by separating light signals by individual modes and selecting and transmitting mode light fitted to an output level in accordance with the loss in a transmission line. SOLUTION: Various pieces of data and information are overlapped with multi-mode light having a level deviation from a light source 1 in a modulator 3. Multi-mode light can receive an overlapped signal in the same way as the reception of full mode light even if respective mode light beams are similarly modulated and any mode light beams are received. A selection block 6 cuts unnecessary mode light in multi-mode light and single desired mode light is made incident on the optical transmission line 4 and it is transmitted. At that time, the transmission loss of the optical transmission line 4 is previously evaluated and the selection block which can output single light suitable for reception in a receiver 2 is selected and arranged. Thus, the optical attenuator for level adjustment is eliminated and the deterioration of quality at the time of transmission by the attenuator can be eliminated. |
