| 摘要 |
PROBLEM TO BE SOLVED: To superpose an auxiliary signal in which a high-frequency component is pre-emphasized through a frequency filter upon signal light without deteriorating the transmitting quality of the signal light itself by modulating the intensity of excitation light with the auxiliary signal. SOLUTION: A CR type differentiation circuit 6 which can be most readily constituted is used as a frequency filter. The capacitor C and resistor R of a differentiation circuit 6 are adjusted to the optimum states in corresponding to the excitation light modulating frequency characteristic of an erbium-added fiber 1 which is an amplifying medium, namely, in corresponding to the reciprocal number 1/τof the time constant of the stimulating light. Therefore, the intensity of stimulating light is modulated in advance with an auxiliary signal corrected by means of the differentiation circuit 6. The auxiliary signal outputted from the circuit 6 has a differential waveform in which a high-frequency component is emphasized and intensity modulation which is close to the original waveform of the auxiliary signal is superposed upon amplified signal light. Since the differentiation circuit 6 is used as the frequency filter, an excellent auxiliary signal having no signal distortion can be superposed upon the signal light. |
