| 摘要 |
PURPOSE:To cope with the increase of the signal volume of up signals by provid ing an optical bidirectional receiver, which is installed on the transmission line between a center device and a terminal, with a frequency converter which converts frequencies of up signals from plural main line systems. CONSTITUTION:The down signal divided by a branching device 64 passes a demodulator 68, a controller 76, a modulator 69, and couplers 70 and 67 and is converted from the electric signal into an optical signal by an optical transmitter 66 and is transmitted to the center device through an up signal transmission line 65 as an optical fiber. The up signal transmitted from the terminal through a terminal-side transmission line 75 has the low band branched by a branching device 63. The up signal of the low band branched by a branching device 73 passes a gate switch 74 and has the frequency converted by a frequency converter 72 and passes a variable attenuator 71 and is coupled by couplers 70 and 67 and is converted from the electric signal into an optical signal by the optical transmitter 66. Consequently, the down signal of the high band H and the up signal of the low band L can simultaneously exist by frequency division. |
