Abstract: It is herein described a linear optical transmission system with failure protection wherein the protection is totally accomplished at an optical level, and it operates on the entire system, and not just at a local level. This is accomplished, in a linear system for the transmission of N signals from a first station to a second station, by providing in each station an optical communication path for each signal, and a single shared optical communication path, as well as a communication path for a protocol between the two stations for managing the protection requests arising from optical failure detectors in the optical communication paths and optical switching sections in the two stations for selectively switching the signal propagating along the optical communication path having an optical failure onto the shared communication path. Arrangements of optical switching suitable to the implementation of said system are also described.

Abstract: An optical cross connect (OXC) switching fabric that has wavelength and fiber modularity, allowing the OXC fabric to be expanded for new wavelengths and new input fibers with the addition of new modules is disclosed. A plurality of main module switches comprising two-channel add/drop modules are connected to a common junction module switch. For M wavelengths on N fibers switched within the OXC, each of N/2 main modules includes M separate building blocks each comprising two one-channel add/drop module, and the junction module includes M×N/2 selection matrices for N/2 main module and M×N passive optical splitters having one-input and (N/2−1) output. The main module building blocks and junction module selection matrices provide wavelength and fiber modularity and expandability for the OXC.

Abstract: An apparatus and method for reducing polarization hole burning in a rare-earth-doped fiber amplifier within an optical communication system by converting an optical carrier having a characteristic wavelength into a polarization-rotating optical carrier is disclosed. The apparatus includes a polarization-fixing device optically coupled in the optical transmission system to transform the optical carrier to a polarized optical carrier, and an acousto-optic modulator positioned to receive a first portion of the polarized optical carrier and to orthogonally convert the polarization of the polarized optical carrier and to shift the polarized optical carrier by a modulation frequency. The apparatus and method further includes a polarization beam combiner optically coupled to receive the orthogonally polarization converted and frequency shifted polarized signal and a portion of the original polarized optical carrier.