| 摘要 |
<p>An optical fiber network of WDM type comprises two fibers (7e, 7w) which carry light signals propagating in opposite direction and which are arranged in a ring configuration, in which always one link (2) between two neighbouring nodes is inactive but provides a standby-link which is used for failure in another link, in the case of which the previously inactive link is made active. An add and drop (1) node used in the network has band blocking filters (31e, 31w) connected in a fiber (7e, 7w) between a drop coupler (17e, 17w) and an add coupler (23e, 23w), taking out a share of the light power in each direction to be received through bandpass filters (37e, 37w) in receivers (11e, 11w) and adding new wavelength channels produced in transmitters (13e, 13w) respectively. Switches (39e, 39w; 33e, 33w) are used for receiving and transmitting on the wavelength channels in correct directions. The positions of the switches can be changed when the inactive link (2) has to become one of the two links directly connected to the node. A very efficient use of the wavelength channels in the network can then be achieved for nodes having a minimun of in-line components and particularly a minimum of in-line filtering components.</p> |
