| 摘要 |
PURPOSE:To provide a light transmission device having a function of automatically controlling inputted signals of multi-channel to make them constant in degree of modulation when outputted signals of multi-channel are changed in degree of modulation due to temperature change, the deterioration of the device in characteristics with time or the like. CONSTITUTION:Combining means 11 and 12 combine multiple input signal is with off-band signals together, signals outputted from the combining means 11 and 12 are inputted into a gain amplifying means 1 which is controlled through a control terminal, and signals outputted from the gain amplifying means 1 are electro-optically converted. The converted optical signals are partially branched off, and the branched signals are photoelectrically converted through optical output monitoring means 3 and 4, output level control means 5 and 8 detect the overall output level of the optical output monitoring means 3 and 4 and output, control signal A which controls the gain amplifying means 1 in output so as to make the output level of the optical output monitoring means 3 and 4 coincident with a prescribed reference output level, the output level of off-band signals detected from the output of the gain amplifying means 1 and the control signal A are inputted into a computing means 16, the computing means 16 computes the degree of modulation basing on the ratio of the overall optical output signal to the off-band signal level, and a modulation control means 10 feeds feedback signals to the gain amplifying means 1 and the control terminal so as to make the output signal of the computing means 16 coincident with a set reference degree of modulation. |
