| 摘要 |
Branching filters (1,2) are placed on a trunk fiber along which light signals of wavelengths lambda 3, lambda 4 and lambda 5 are transmitted in multiplexed form. A transmitting-side branch fiber F2 and a receiving-side branch fiber F3 are respectively placed on the opposite sides of the branching filters. The branching filters both have spectral characteristics in which they reflect the proximity of wavelengths lambda 1 and lambda 2 and pass the wavelengths lambda 3, lambda 4 and lambda 5. A white light source (10) is provided at a termination of the transmitting-side branch fiber and light switches SW-B are disposed in the course thereof. The light switches incorporate therein branching filters placed on the optical path when they are turned on and withdrawn from the optical path when they are turned off. One branching filter has a spectral characteristic in which is reflects the wavelength lambda 1 and allows wavelengths to pass therethrough, whereas the other branching filter has a spectral characteristic in which it reflects the wavelength lambda 2 and passes other wavelengths. On the other hand, a receiver is provided at a termination of the receiving-side branch fiber, and a further branching filter, which reflects the wavelength lambda 1 and passes other wavelengths, is placed in the course thereof. Further, a receiver is provided on the opposite side of the branching filter. <IMAGE> |
