| 摘要 |
PURPOSE:To transmit the frequency multiplex signals corresponding to the video signals and the digital video signals corresponding to the video demand via a single optical fiber with no clipping distortion by, applying the modulation corresponding to the video signals to each of semiconductor laser beam sources equal to the number of divided channels set for the video signals to be transmitted. CONSTITUTION:The FDM signals corresponding to the video signals 20VAAA, 20VAB and 20VAC obtained by dividing the video signals of 60 channels every 20 channels among three LD (semiconductor lasers) 14 to 16 ungergo the analog modulation by the F20A to F20C respectively. Thus each of LD 14 to 16 is assigned for the video signals of only 20 channels. Under such conditions, the effective light modulation degree mue is 20% or less as long as the light modulation degree is set at 6.3% or less per channel. Thus no clipping distortion is generated. Meanwhile the VOD signals are also transmitted via an exclusive LD 18. The optical outputs of the LD 14 to 18 are synthesized by the 3dB optical couplers 22 to 24 and finally multiplexed into a single optical signal LF20 ABCV that is transmitted via a single optical fiber 2. |
