OPTICAL TRANSMISSION SYSTEM INCLUDING OPTICAL RESTORATION

摘要

An optical communications system employs a plurality of optical nodes interconnected in a ring configuration by at least two optical transmission media, for example, optical fiber. The at least two optical transmission media, in this example, provide optical service transmission capacity and optical protection transmission capacity. Efficient restoration of optical communications between optical nodes in the ring, after an optical transmission media failure, is realized by employing a relatively simple and efficient optical switch matrix having a first number of possible switching states and, then, by utilizing only a second number of the switching states fewer than the first number to switch optically from the optical service transmission capacity of the failed or faulted optical transmission media to the optical protection transmission capacity of another optical transmission media. Optical switching states of the optical switch matrix are blocked that are not actively used for switching from the active optical service capacity of the faulted optical transmission media to the standby optical protection capacity of the other optical transmission media. Use of this relatively simple optical switch matrix allows for the bulk switching of the optical wavelengt hs as contrasted with the one-to-one switching of the optical wavelengths used in prior arrangements. In a preferred embodiment of the invention, each of the at lea st two optical transmission media provides both bi-directional service transmission capacity and bi-directional protection transmission capacity. In a specific embodiment of the invention, each optical transmission channel (wavelength) includes 50 percen t bi-directional optical service transmission capacity and 50 percent bi-directional optical protection transmission capacity. In another embodiment of the invention, on e of the at least two optical transmission media provides active optical service transmission capacity and another of the optical transmission media provides standby optical protection transmission capacity. In still another embodiment of the invention, at leas t four optical transmission media (optical fiber) are utilized to provide transmit and receive active optical service transmission capacity and transmit and receive standby optic al protection 25 transmission capacity. Specifically, one pair of the optical transmission media is used to provide bi-directional transmit and receive active optical service transmission capacity and another pair of the optical transmission media is used to provide the bi - directional transmit and receive standby optical protection transmission capacity.