| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical direct amplifier capable of avoiding operation in the vicinity of the threshold of each of exciting LD light sources and thus stabilizing its characteristics over the whole multiplexing range, by changing the number of exciting LD light sources to be driven according to an increase or decrease in the number of multiplexed signals in a manner increasing the number of exciting LD light sources to be driven when the number of multiplexed signals is increased, and decreasing the number of exciting LD light sources to be driven when the number of multiplexed signals is decreased. SOLUTION: A control circuit 15 generates such a control signal as to decrease the number of LD light sources to be turned on, among a plurality of LD light sources respectively constituting a frontward exciting light source 7 and a backward exciting light source 8, according to a decrease in the number of detected signals indicative of the presence of any signal supplied from a signal detector 14, and supplies the generated control signal to driving circuits 5 and 6. Compared with a conventional optical direct amplifier wherein all exciting LD light sources are driven at all times while decreasing the number of exciting LD light sources according to a decrease in the number of signal channels, this optical direct amplifier is designed such that a current for driving each exciting LD light source is increased when the number of signal channels is decreased, whereby the operation in the vicinity of the threshold of each exciting LD light source can be avoided. |
