| 摘要 |
<p>A fiber-optical network using wavelength multiplexing has a ring configuration comprising a plurality of nodes (1) connected by regular communication links (3) for transferring information between neighbouring nodes. A standby link (5') is provided in parallel to each regular link (3). In the case of a failure of a regular link (3) switches (17, 27) in the nodes (1) switch the information to be transferred over the failed link to travel through all standby links except the standby link parallel to the failed regular link, so that this information will have to travel through all nodes in a direction opposite to that which it would have regularly taken. Optical amplifier assemblies (19, 29; 35) are used for the protective links (5') at both ends thereof. Control units (35) of the amplifiers use signals from light sensors (33, 39) sensing the input and output light power of the amplifiers and adapt the output power of the amplifiers stepwise in accordance with the sensed input power. An intermediate state of the amplifier output power is used for supervising the protective links and then normally light carrying no signals will propagate around the network in two closed loops, the light power therein being considerably lower than that used for regular signal transmission. In this way a simple supervision of the protective links is obtained, resulting in a simple architecture of the nodes requiring little management functions.</p> |
