| 摘要 |
PURPOSE:To break an optical signal, which is subjected to amplitude modulation with an optional frequency, or allow this optical signal to pass through in accordance with the modulation frequency, by setting the sharpness of a filter to a required value in relation to the attenuation quantity of an optical variable attenuator. CONSTITUTION:The attenuation quantity of an optical variable attenuator 9 is controlled to change the characteristic of the filter, and the response to an impulse input of the filter is controlled, and the level of a noise which can be removed or suppressed is adjusted in an optical circuit where a narrow noisy optical impulse input is removed to output only the signal. Frequency characteristics of respective fibers, an optical coupler 5, and an optical branching filter 6 are perfectly flat in the band of an angular frequency W of modulating waves, and a fiber 2 is sufficiently shorter than a fiber 1, and the time required for the transmission of the light through the overall length of the fiber 2 is sufficiently shorter than that required for the transmission of the light through fibers 7 and 8. |
