| 摘要 |
PURPOSE:To eliminate the need for a light source for a reception terminal station, to enhance the reliability and profitability and to avoid the effect of a modulation element onto a transmission signal by providing a light source, a 1st optical demultiplexing section and a 1st light receiving section on a transmission terminal station, and providing a 2nd light demultiplexing section, a phase modulation section, a reflection section and a 2nd light receiving section on the reception terminal station. CONSTITUTION:A transmission terminal station 1 is provided with a light source 2, a light demultiplexing section 3-1 demultiplexing a light from the light source subjected to light intensity modulation at a prescribed ratio and a light receiving section 4-1, and a reception terminal station 6 connected to one optical fiber transmission line 5 in common is provided with an optical demultiplexing section 3-2, a phase modulation section 7, a reflection section 8, and a light receiving section 4-2. The light transmitted in such a manner is bisected once by the demultiplexing section 3-2 and a modulation section 7 gives phase modulation to at least one of the divisions to made both demultiplexed beams in the light receiving section 4-2 simultaneously via the reflection section 8. On the other hand, the two demultiplexed beams reflected partly in the reflection section 8 are returned to the original route composed of almost same demultiplexing length the light intensity is modulated by the demultiplexing section 3-2 and the resulting light is returned again to the transmission line 5. |
